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IECON Proceedings (Industrial Electronics Conference) (25771647)
Impedance mismatching is a prevalent issue in wireless power transfer (WPT) systems across various power levels and operating frequencies. In scenarios where coils are closely coupled, the maximum power transfer does not occur at the natural resonant frequency of the coupled coils due to impedance mismatching between the internal impedance of the power source and the WPT system’s input impedance. This results in the frequency splitting phenomenon. This paper first examines the frequency splitting phenomenon using the maximum power transfer theorem. Subsequently, a Perturbation and Observation (P&O)-based method with a variable step size is proposed to enhance power transfer efficiency over a range of coil-to-coil distances. Unlike conventional, time-consuming search-and-find impedance matching (IM) methods, this approach achieves optimal IM network parameters in a single step. A scaled-down 20-watt prototype is fabricated to validate the effectiveness of the proposed method in terms of input current, active and reactive input powers, as well as power factor correction (PFC). © 2024 IEEE.
IEEE Transactions on Transportation Electrification (23327782) 10(2)pp. 3482-3491
An innovative control method for reducing the torque ripple of non-sinusoidal brushless dc motors in field weakening regions based on direct power control is proposed here. Torque ripple, due to the disproportionate stator current and its non-sinusoidal back EMF voltage, is one of the known drawbacks of brushless dc motor drives. Upon motor speed acceleration, the waveform of the stator current becomes distorted, which in turn intensifies the torque ripple. This proposed method is able to control the motor speed from zero to values higher than the base speed range. The realization of the proposed method in the stationary reference-frame makes the method implementation simple and robust. In addition to controlling motor speed, by applying a three-phase conducting method instead of the conventional two-phase conducting method and control of instantaneous input power into the rotor in the proposed method, the torque ripple is also reduced, simultaneously. The torque ripple reduction and robustness of the proposed method are compared with the phase advance angle (PAA) method through simulation and experimental. The results indicate the superiority of the proposed method in both the steady- and transient-states. Moreover, the implementation of the proposed method on a prototype brushless direct current (BLDC) drive is successfully evaluated. © 2015 IEEE.
IEEE Transactions on Instrumentation and Measurement (00189456) 73pp. 1-9
High impedance fault (HIF) detection is a problem in distribution power systems protection. Detection of these faults by overcurrent protection relays is difficult or impossible. Therefore, system recovery is postponed, and individuals may be exposed to the risk of electrical shock. This article defines a family of HIF current-time patterns with different ignition angles. To detect the HIF current, the proposed detection method searches in its family of HIF patterns and finds the pattern that has the highest correlation to the HIF current. Based on the measured correlations, a time-domain algorithm is proposed for the HIF current. If the highest correlation between the family of HIF patterns and the measured current signal is above a given threshold value, then the fault is detected as an HIF. Verified by simulations and experimental results, the proposed method can correctly detect HIF within one power system cycle. © 1963-2012 IEEE.
IEEE Transactions on Circuits and Systems (15498328) 70(9)pp. 3806-3817
Wireless power transfer (WPT) systems' efficiency is significantly impacted by non-monotonic variations in the coupling coefficient. For very short distances or strong-coupling cases, the WPT efficiency is minimal at the natural resonant frequency, with two peaks around this frequency, known as the frequency splitting phenomenon. On the other hand, WPT capability decreases for long distances or weak coupling cases. Therefore, adaptive matching is required for WPT systems with varying distances, like wireless charging systems for electric vehicles (EVs). This paper first presents a detailed analysis of the frequency splitting phenomenon by studying the root locations of the WPT system's transfer function. Then, a real-time fixed-frequency adaptive impedance matching (IM) method is proposed, in which the amplitude and phase of the input impedance is estimated using the average active power, the average reactive power, and the amplitude of input voltage. Unlike traditional search-and-find techniques, the proposed method calculates the optimal IM network parameters only in a single iteration, which improves the convergent speed. A scaled-down 20-Watt prototype controlled by the TMSF2812 is fabricated and used to validate the effectiveness of the proposed method over a wide range of coil-to-coil distances. © 2004-2012 IEEE.
IEEE Transactions on Transportation Electrification (23327782) 9(3)pp. 3769-3779
In this article, a second-order sliding mode control (SMC), based on super-twisting algorithm, is proposed for direct power control (DPC) of the brushless dc (BLDC) motor. The proposed controller uses a super-twisting scheme that requires only sliding surface information and can handle system uncertainties and external disturbances, well. This scheme can improve the BLDC motor torque ripple by solving the disadvantages of the conventional SMC method, such as the chattering effect and high-frequency switching control. This method is simple and robust for the BLDC motor's biggest challenge, torque ripple, which does not require any voltage and current control loops or complex reference frame transformations. The simulation results of the proposed method are compared with the DPC and model predictive control (MPC) methods, which indicate the superiority of the proposed method in both the steady and transient states. Moreover, the motor parameters variation in the tracking of active and reactive power are discussed. In addition, the practical results of the proposed method in both cases of speed and load variation show the effectiveness of this method in reducing power (torque) ripple and current total harmonic distortion (THD) and increasing the system's efficiency compared to other methods. © 2015 IEEE.
Journal Of Operation And Automation In Power Engineering (24234567) 10(2)pp. 122-133
The relay coordination problem of directional overcurrent has been an active research issue in distribution networks and power transmission. In general, the problem of relay coordination is the nonlinearity of the optimization problem, which increases or decreases with different network structures. This paper presents a new method with directional overcurrent relay coordination approach to reduce the operating time of the relays between the primary and backup relays by using hybrid programming of ILP (interval linear programming) and DE (differential evolution). Due to the difference in short circuit current level from grid connected to the isolated mode, therefore, it is necessary to use a reliable protection solution to reduce this discrimination time and also to prevent the increase of coordination time interval (CTI). The ability of the objective function used in this paper is to reduce the discrimination time of primary and backup relays and simultaneously reduce the operating time of primary and backup relays by introducing a new method. The basic parameters of the directional overcurrent relay (DOCR) such as time multiplier setting (TMS) and plug setting (PS) have been adjusted such that the relays operation time should be optimized. Optimization is based on a new objective function, described as a highly constrained non-linear problem to simultaneously minimize operating time in backup and primary relays. A function of penalty is also used to check the problem constraints in case the backup relay time is fewer than that of the main relay. The method is implemented on modified IEEE 14-and 30-bus distribution networks. The results demonstrate the efficiency of the method, and the values are optimal compared to those of other algorithms. MATLAB program has also been used to simulate optimization. © 2022 University of Mohaghegh Ardabili. All rights reserved.
IET Renewable Power Generation (17521416) 15(13)pp. 2931-2943
This paper proposes a frequency-control scheme for Doubly Fed Induction Generator (DFIG)-based (Type-3) wind turbines to improve the primary-frequency-control when the grid power balance is disturbed. The increasing penetration level of renewable energy sources, like wind power plants, reduces the total available inertia of modern grids, which deteriorate the frequency response in case of sudden power-mismatches. The proposed closed-loop participation of wind power plant interacts with the thermal units to reduce the frequency nadir and frequency settling-time, during the inertial and primary stages. The designed disturbance observer decreases the uncertainties in the estimation of grid parameters, which results in robust PI performance in adjusting the ancillary power provided by wind turbines. Certain measures considered within the control loop to limit the rate-of-change-of-frequency within the permissive range to avoid the protective relays tripping. Comparative simulations studies on modified IEEE 9-bus and 68-bus test systems verify the effectiveness and advantages of the proposed method. © 2021 The Authors. IET Renewable Power Generation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology
IET Renewable Power Generation (17521416) 15(7)pp. 1469-1482
The new generation of photovoltaic (PV) systems represents higher sustainability during grid faults thanks to increased ancillary services, such as low voltage ride-through (LVRT) capability used when the PV system is subjected to voltage sag. Unlike previously presented strategies that just dealt with voltage sag problem under uniform radiation conditions, in this study, a new control strategy implementing LVRT capability during low-voltage faults under partial shading conditions is proposed. First, radiation levels are estimated by using the least-squares curve fitting (LSCF) algorithm. Second, the voltage/current of maximum power points (MPPs) and minimum power points are calculated. Also, the corresponding algebraic function for the (Power - Voltage) P-V curve is extracted using only PV voltage and power vectors. Finally, under partial shading conditions, the moving operating point to the right side of MPP is well-achieved through a power proportional-integral controller. To validate the effectiveness of the proposed control strategy, simulations and experiments are conducted on PV systems. The simulation and experimental results and the comparison made between this algorithm's performance and other methods confirm that the proposed algorithm outperforms other methods in terms of high accuracy, fast dynamic and low oscillations in different partial shading conditions and with different radiations. © 2021 The Authors. IET Renewable Power Generation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology
IET Microwaves, Antennas and Propagation (17518725) 14(1)pp. 36-44
Wireless charging is widely considered as a safe and reliable way for powering biomedical implants, as it avoids problems like surgical infection. Wireless power transfer (WPT) systems are desired to work efficiently against variations in coil–coil distance or output load. On the other hand, to maintain the maximum overall efficiency of the WPT system, the high frequency (HF) power amplifier, used to feed WPT system, must operate at optimal zero-voltage switching (ZVS) condition. In this paper, an automated dual-objective control strategy adaptive to variations in coil–coil distance or output load is proposed which ensures both targets of tracking maximum power point and operating at optimal ZVS condition by adjusting operating frequency and duty-cycle of switching voltage of HF power amplifier, respectively; that is while there have been few studies which have addressed both the two targets. To evaluate the effectiveness of the proposed strategy, a PCB prototype, operating at 800 kHz, is fabricated. Experimental results, demonstrating the proposed strategy increases transferred power from 23 mW to about 45 mW, are in good agreement with theoretical predictions. Additionally, while implanting the receiver coil in a real biological tissue, experiments show only 2% of degradation in power transfer efficiency as well as no frequency shift. © The Institution of Engineering and Technology 2019.
IEEE Transactions on Industrial Electronics (02780046) 67(1)pp. 28-37
This paper proposes a new reference-generation-strategy for direct torque control (DTC) of doubly fed induction generator (DFIG), under symmetrical voltage-dips. Since DTC has no current-control loop, it cannot prevent overcurrent during voltage-dips. The proposed method prevents overcurrent in the rotor side converter, by damping the transient-flux and modifying the references of rotor-flux and torque, during voltage dip and recovery. The analysis of DTC for DFIG is presented by a λ-i equivalent circuit, which is decomposed into forced and natural circuits. Based on the natural λ-i circuit, the method adds a transient compensation term to the rotor-flux reference, which is obtained by multiplying the stator-natural-flux with a proposed decaying-ramp function. Moreover, this method reduces the forced component of rotor-flux proportional to the grid voltage. As a result, this method adjusts the transient-flux damping time and ensures overcurrent prevention in the rotor and stator windings. The torque reference is modified to maintain the torque-angle (between rotor and stator flux vectors) constant, which results in stable control of the DFIG during grid faults. The effectiveness of the proposed method is confirmed by experimental results of a 3-kW test set-up and simulation results of a 2-MW DFIG. © 1982-2012 IEEE.
IEEE Transactions on Power Delivery (19374208) 35(2)pp. 919-928
Switching-on a power transformer creates energizing inrush current (EIC) which in turn leads to sympathetic inrush current (SIC) in adjacent in-service transformers (ITs). Sympathetic inrush current changes the waveform and prolongs the duration of its origin EIC. This makes the analysis and estimation of EIC complicated. Occasionally, the stress of EIC can cause internal short circuit in energizing transformer. Detecting short-circuit fault current during EIC is a challenge for transformer differential protection. On the other hand, SIC may mislead the earth-fault protection of in-service-transformer. This paper, first, proposes a new dc equivalent-circuit based on the dc-component of inrush current, which is efficient in analyzing concurrent EIC and SIC. Next, based on this equivalent circuit, new predictive formulas for EIC and SIC are derived. By employing these formulas, the transformer internal fault during inrush current can be detected based on the comparison between the predicted and measured waveforms, which prevents differential protection from fail-to-trip. Also, the predicted SIC waveform can be compared with the measured waveform to prevent IT earth-fault protection from mal-trip, during inrush current. Finally, the proposed equivalent circuit and formulas are verified using the EMTP simulation results of a real grid, under different system conditions. © 2019 IEEE.
IEEE Transactions on Industrial Electronics (02780046) 67(7)pp. 6078-6088
In this article, an innovative control method, termed direct flux-vector control, is proposed for the stand-alone doubly fed induction generators (DFIGs) feeding local ac loads. In these systems, both the amplitude and frequency of the stator voltage must be precisely controlled. The proposed method, instead of controlling the rotor currents or voltages, directly controls the rotor flux vector, including magnitude and angle. To achieve an accurate control, two separate closed-loop hysteresis controllers are employed in which the stator-voltage amplitude and frequency are adjusted through the rotor-flux magnitude and angle, respectively. The proposed control method is performed in the rotor reference frame, thus it does not require the rotor speed/position sensors or any reference-frame transformation. As an outstanding feature, the method works for both sub and supersynchronous speed modes without changing the switching table. Hence, no need to detect the operation mode of DFIG. Besides, the method consists of a simple implementation and is almost parameter independent, as it only requires the rotor resistance. The proposed method is implemented on a 3-kW laboratory scale DFIG and its performance, effectiveness, robustness, and correctness are evaluated and discussed for a series of experimental tests. © 1982-2012 IEEE.
Sadeghi, R. ,
Madani, S.M. ,
Lipo, T.A. ,
Agha kashkooli m.r., M.R.A. ,
Ataei, M. ,
Ademi, S. IEEE Transactions on Industrial Electronics (02780046) 66(10)pp. 7510-7519
This paper presents the performance analysis of brushless doubly fed induction generator (BDFIG) during symmetrical voltage dips. The equivalent circuit consists of resistances and dependent voltage sources in its rotor loop; thus, its voltage-dip analysis becomes more challenging. To overcome such difficulty, a reduced full-order model of the BDFIG into a new T-model is presented. A detailed mathematical analysis is performed subject to voltage-dip conditions. The time variation for the machines fluxes, electromotive forces, voltages, currents, and active and reactive powers are analyzed and their analytical approaches are derived. The current/voltage stress of power converter during voltage dip is discussed. The accuracy of the proposed T-model and the theoretical voltage dip is confirmed via experimental tests on a 3-kW BDFIG, and simulation results of a 2-MW BDFIG. © 1982-2012 IEEE.
IEEE Transactions on Sustainable Energy (19493029) 9(1)pp. 371-380
The Brushless Doubly-Fed induction Generator (BDFG) has a commercial potential forwind power generation, due to its low maintenance cost. For simplicity, the Cascaded Brushless Doubly Fed induction Generator (CBDFG) topology is usually applied as a model for BDFG. The BDFG-based wind turbines must be synchronized and connected to the grid, without inrush current. This paper purposes an improved Direct Torque Control (DTC) method for smooth synchronization of BDFG. Since BDFG has a complicated model, due to the resistance and voltage source in its rotor loop, finding proper references for smooth synchronization is difficult. To overcome this difficulty, a new model for BDFG is proposed. Appropriate flux and torque references for the DTC scheme are proposed based on this model, in order to achieve grid synchronization without inrush current. A 2-MW BDFG is simulated to show the efficiency and accuracy of this proposed method. The experimental results of a 3-kW laboratory scaleBDFGconfirm the efficiency of this proposed method. © 2017 IEEE.
Journal of Power Electronics (15982092) 18(1)pp. 11-22
This paper presents a single switch, high step-up, non-isolated dc-dc converter suitable for renewable energy applications. The proposed converter is composed of a coupled inductor, a passive clamp circuit, a switched capacitor and voltage lift circuits. The passive clamp recovers the leakage inductance energy of the coupled inductor and limits the voltage spike on the switch. The configuration of the passive clamp and switched capacitor circuit increases the voltage gain. A wide continuous conduction mode (CCM) operation range, a low turn ratio for the coupled inductor, low voltage stress on the switch, switch turn on under almost zero current switching (ZCS), low voltage stress on the diodes, leakage inductance energy recovery, high efficiency and a high voltage gain without a large duty cycle are the benefits of this converter. The steady state operation of the converter in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is discussed and analyzed. A 200W prototype converter with a 28V input and a 380V output voltage is implemented and tested to verify the theoretical analysis. © 2018 KIPE.
IEEE Transactions on Power Delivery (19374208) 33(6)pp. 3242-3245
Fast and accurate fundamental phasor-estimation is a challenging task in digital relays. This letter proposes an improved discrete Fourier transform (DFT)-based phasor estimation algorithm. The accuracy of DFT-based methods is degraded owing to presence of decaying dc component (ddc) in fault current signals. To overcome the undesired effect of ddc, this letter introduces an auxiliary signal, which is generated by down-sampling of the fault current. The fundamental phasor is precisely estimated using sample-summation of the auxiliary signal besides DFT and sample-summation of the fault-current signal. Comprehensive simulations are performed for performance evaluation. The simulation results confirm that the proposed algorithm is fast and robust against ddc, harmonics, and noise. Moreover, the algorithm reduces the computational complexity, which makes it appropriate for digital relaying. © 1986-2012 IEEE.
IET Power Electronics (17554543) 11(13)pp. 2151-2160
A new non-isolated high-voltage gain three-port converter for standalone photovoltaic systems is proposed. The magnetic element of this converter is only one coupled inductor. The primary winding of the coupled inductor is shared between battery charger circuit and main converter. Leakage inductance energy of the coupled inductor is either transferred to battery or is regenerated via the passive-clamp circuit. Using switched capacitor and voltage lift techniques, the voltage gain is significantly increased for both low-voltage ports. Single magnetic element, high-voltage gain with reasonable duty cycle, lowvoltage stress on the switches, low winding turn ratio of coupled inductor and high efficiency are the merits of this converter. The operation principles and the steady-state analysis are described for the three modes of: single-input single-output, single-input dual-output and dual-input single-output. To verify the theoretical analysis, a laboratory prototype with 28 V input, 48 V battery voltage and 380 V output voltage is implemented and tested. © The Institution of Engineering and Technology 2018.
IEEE Transactions on Instrumentation and Measurement (00189456) 67(3)pp. 582-592
This paper presents a new filter-based algorithm to estimate the fundamental phasor of fault currents, using the proposed complex frequency filter. The presence of decaying dc component (ddc) in fault currents causes large error in discrete Fourier transform (DFT)-based phasor estimation methods. The proposed filter discriminates the ddc from dc and sinusoidal signals. In this algorithm, first, the ddc is filtered out by the proposed filter. Then, the fundamental phasor can be precisely extracted by applying DFT. Second and fourth order of the complex frequency filter and their design method are presented. To evaluate the performance of the proposed algorithm, several test signals are used. The algorithm is also compared with recent DFT-based and mimic-DFT methods, using four performance indices. The simulation results demonstrate the robustness of the proposed algorithm against harmonics, noise, multiple ddc components, and off-nominal frequency. It also offers faster convergence speed. The proposed complex frequency filter can also be used for the phasor estimation of harmonic components in the presence of ddc with no need to readjust its parameters. © 2018 IEEE.
IEEE Transactions on Instrumentation and Measurement (00189456) 67(11)pp. 2592-2602
Frequency estimation is vital for monitoring, control, and protection of power systems. Multiple signal classification (MUSIC) method has been used for frequency estimation in communication systems. This method requires wide range of frequency scanning and heavy computations, which is inappropriate for power system applications. This paper proposes an adaptive accelerated MUSIC algorithm for frequency estimation in power systems. The algorithm accelerates the frequency scanning and adapts itself to transient conditions of power systems, to keep the accuracy of the frequency estimation with minimum computations. Experimental signals besides several static and dynamic test signals are used to evaluate and compare the performance of the proposed algorithm with recent methods. These comparisons show that the proposed algorithm provides faster convergence speed, lower computation burden, and more robustness to noise and grid disturbances. These significant advantages make the proposed algorithm appropriate for power system protection and control applications. © 1963-2012 IEEE.
IET Electric Power Applications (17518660) 12(6)pp. 757-766
Here, a reduced-order model for stand-alone cascaded doubly fed induction generator (CDFG) is presented for aircraft application, which is capable of operating in both starting and generating modes. This generator has lower maintenance cost and higher reliability, in comparison with traditional variable speed constant frequency system, based on a doubly fed induction generator (DFIG). These features make the CDFG appropriate for embedded aircraft applications. The main drawback of this generator is its inherent complexity; therefore, its analysis and control design is difficult. This complexity is due to the existence of resistances and voltage sources in the rotor loop of the full-order model. To overcome this difficulty, this study proposes a reduced-order model for the CDFG, which is similar to that of the DFIG in the synchronous reference frame. To demonstrate the efficiency of the proposed model, a field-oriented controller for CDFG is designed based on this model and compared to the full-order model. The performance and accuracy of the proposed model is validated through simulation and experimental results subject to balanced and unbalanced load change, and rotor speed variations test scenarios. © The Institution of Engineering and Technology 2018.
Applied Soft Computing (15684946) 62pp. 1044-1055
Phase unbalancing is a problem in distribution networks that causes feeder service tripping and reduces the network quality. Re-phasing is the strategy used for phase balancing. Moreover, the power loss reduction is a significant problem in distribution networks. A common solution for power loss reduction is reconfiguration. Besides, optimal DG placement can reduce power loss and improve voltage profile. In this paper, a new method is proposed for simultaneous optimization of re-phasing, reconfiguration, and DG placement in distribution networks to reduce phase unbalancing and power loss and improve voltage profile. As there are four dissimilar objective functions, the objectives are made fuzzy and integrated as the fuzzy multi-objective function. Finally, the optimization is done by using Bacterial Foraging with Spiral Dynamic (BF-SD) algorithm. To demonstrate the performance of the proposed method, it is applied to IEEE 123-node test feeder. © 2017 Elsevier B.V.
IEEE Transactions on Industrial Electronics (02780046) 65(11)pp. 9147-9156
This paper proposes and implements a super-twisting sliding mode direct power control (SSM-DPC) strategy for a brushless doubly fed induction generator (BDFIG). DPC has fast and robust response under transient conditions; however, it suffers from active and reactive power ripples and current distortions, which degrades the quality of the output power. In contrast, vector control has good steady-state current harmonic spectra; however, it is not robust to machine parameters variations, and thus needs a phase-locked loop for synchronous coordinate transformations. The SSM-DPC strategy controls active and reactive power directly without the need of the phase-locked loop. Moreover, its transient performance is similar to DPC and its steady-state performance is the same as vector control. The proposed controller is robust to uncertainties toward parameter variations and achieves constant converter switching frequency by using space vector modulation. Simulation and experimental results of a 2 MW and 3 kW laboratory-scale BDFIG are provided and compared with those of integral sliding mode and DPC to validate the effectiveness, correctness, and the robustness of the proposed strategy. © 1982-2012 IEEE.
IET Generation, Transmission and Distribution (17518687) 12(10)pp. 2317-2324
Energising a power transformer may cause inrush current, which misleads the protection systems. Therefore, the inrush current analysis is important in designing and protecting power transformers. The non-linear behaviour of transformer core saturation makes this analysis difficult. Thus, several researches try to model the core saturation and inrush current. This study presents a new technique based on core flux analysis to develop an equivalent circuit for power transformer during inrush current. For this purpose, a new λ-i equivalent circuit is proposed for saturated core transformer by transformation of conventional v-i circuit. This λ-i equivalent circuit clearly shows the effect of parameters on transformer saturation and inrush current; and provides a powerful insight into these phenomena. Moreover, new equations are developed which can predict inrush current and core-flux envelopes. The predicted waveforms can be compared with measured transformer current to detect transformer internal-fault during inrush current, which is a challenge in transformer protection. This model and the equations are compared with the recorded inrush current waveform of a real transformer, and simulation results. These comparisons verify the efficiency of the model and accuracy of the equations. © 2018, The Institution of Engineering and Technology.
IEEE Transactions on Power Delivery (19374208) 32(6)pp. 2416-2423
This paper proposes a new fast algorithm to estimate the fundamental phasor of fault current signals, based on discrete Fourier transform (DFT). Since fault currents include decaying dc component (ddc), DFT-based algorithms have inaccuracy in phasor estimation. The proposed algorithm consists of four steps. First, a new auxiliary signal is introduced based on a simple high-frequency modulation of the fault current. Then, DFT of the fault current and sample-summation of both fault current and auxiliary signal are calculated, for each one-cycle-length data stream. Next, DFT estimation error due to the ddc is calculated. Finally, by removing this error, accurate fundamental phasor is obtained. This paper uses an innovative and accurate formulation based on notations of signal processing literature. To validate the proposed algorithm, several computer-simulated signals and an electromagnetic transient program-generated signal are employed. The proposed algorithm is compared with recent phasor estimation methods, using wide variety of test signals. Standard indices of rise time, settling time, and percentage overshoot are used for comparison. These comparisons show that the proposed algorithm has robust performance in off-nominal frequency condition, and presence of harmonics, noise and multiple ddc components. Moreover, it provides faster convergence speed and lower computation burden. © 1986-2012 IEEE.
Madani, S.M. ,
Sadeghi, R. ,
Agha kashkooli m.r., M.R.A. ,
Sadeghi, R. ,
Madani, S.M. ,
Agha kashkooli m.r., M.R.A. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 53-57
A direct torque control (DTC) method is developed for grid synchronization of Brushless Doubly Fed Induction Generator (BDFIG). The presented method and the dynamic model of BDFIG are conferred in a reference frame aligned to the stator of control machine. The proposed controller has high performance, i.e., grid connection with minimum current overshoot and fast dynamic response, during the BDFIG loading. The robustness and efficiency of the proposed controller are verified by both simulation and experimental tests. © 2016 IEEE.
Madani, S.M. ,
Moradi, A. ,
Sadeghi, R. ,
Moradi, A. ,
Madani, S.M. ,
Sadeghi, R. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 1416-1421
This paper investigates the impact of load power factor on sympathetic inrush current. Sympathetic inrush current is caused by the voltage drop across the system resistance due to energizing current of the parallel adjacent transformer. It may cause the protection system to mal-trip and the transformer outage. The presented model is validated by simulation using DIgSILENT. The simulation results show that sympathetic inrush current's magnitude depends on the load power factors. This dependency is illustrated and analyzed, which gives deeper insight into sympathetic inrush current and transformer protection. © 2016 IEEE.
Madani, S.M. ,
Agha kashkooli m.r., M.R.A. ,
Sadeghi, R. ,
Agha kashkooli m.r., M.R.A. ,
Madani, S.M. ,
Sadeghi, R. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 58-63
This paper presents a modified hysteretic controller to improve Direct Torque Control (DTC) of the Doubly-Fed Induction Generator (DFIG) to achieve constant switching frequency and reduced torque and flux ripples. The proposed controller generates appropriate voltage vector with variable magnitude and angle, in order to reduce those ripples. The Space Vector Modulation is employed to apply the reference voltage vector to rotor windings. Other advantages of DTC methods such as fast dynamic response and simple coordinate transforms are preserved. The experimental results verify the advantages of this method compared to conventional DTC. © 2016 IEEE.
Foroushani, H.M. ,
Mohammadrezaei, M. ,
Madani, S.M. ,
Sayyar, A. pp. 305-308
On account of its stochastic generation, system voltage fluctuation is one of the impediments to further increase the penetration level of the grid-connected photovoltaic system. However, the reactive power capacity of the photovoltaic inverter can be controlled to regulate the grid voltage. In this paper, the outer current control loop, which is designed in the dq synchronous reference frame, is proposed to give the single-stage three-phase grid-connected photovoltaic system the opportunity to solve the voltage fluctuation problem during the daytime. In order to verify the performance of the presented controller, several simulations are carried out through MATLAB/Simulink in different load, solar power generation and fault conditions. © 2015 IEEE.
2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 31-35
In this paper, a new approach for controlling the Static Synchronous Series Compensator (SSSC) during the fault condition is proposed. To limit the flow of large line currents, and therefore protect the SSSC and other system components, a fault limiting function is exploited in the SSSC operation. © 2015 IEEE.
Madani, S.M. ,
Sadeghi, R. ,
Kharkan B. ,
Abadi M. ,
Madani, S.M. ,
Sadeghi, R. ,
Kharkan B. ,
Abadi M. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 503-508
Doubly fed induction generators (DFIG) are widely used in wind energy conversion. Due to low voltage during fault, these generators may have sudden disconnection, which damages the grid stability. Therefore, many technologies for improving low voltage ride through LVRT capability of this generator have been proposed, in recent years. LVRT capability ensures no loss of production during and after a normal fault. Such a capability cause wind turbines to withstand certain duration and percentage of voltage dips. This paper proposes a method that sustain DFIG synchronization after clearing a fault, with minimal additional equipment and changes in control strategy. Therefore, the turbine can be reconnected to grid very quickly after faults. Another advantage of this method is the possibility of feeding local load during fault. Using this method also keeps the generator in safe operation area (SOA) during fault and voltage recovery periods, and thus improves the turbine behavior and the LVRT capability. © 2015 IEEE.
Australian Journal of Electrical and Electronics Engineering (1448837X) 12(1)pp. 45-59
In the recent years the synchronous reluctance motor (SynRM) has received much attention due to its desirable controllability and simple structure. In this paper, in order to improve the position control performance of a three phase SynRM, a control scheme is proposed. In the proposed controller design, the smooth operation of the traditional linear controllers and the robustness of variable structure controllers have been considered. The proposed controller eliminates the drawbacks of traditional linear control schemes and conventional variable structure control scheme, such as high frequency chattering at the same time. Yet, their advantages such as smooth operation and robustness are preserved as a big merit. The experimental results clearly demonstrate the superiority of the proposed controller over conventional control schemes. © 2015, © Institution of Engineers, Australia.
Electric Power Components and Systems (15325016) 43(15)pp. 1681-1695
A variable structure robust position controller is presented for a three-phase synchronous reluctance motor. Linear control and variable structure control and pulse-width modulation generation are combined. These provide robust, fast, and accurate position control without the penalty of high chattering. Schemes, including conventional sliding-mode control and the proposed scheme, are tested under parameter variations, and sudden perturbations are applied to the system at a specific time, then compared. This scheme uses both advantages of traditional variable structure control methods and linear methods. The disadvantages of each method, such as chattering and parameter sensitivity, are minimized. Results demonstrate that the proposed technique preserves the classical linear position control merits, while both the steady-state and transient behavior are significantly improved in terms of robustness, accuracy, and low ripple. The results also prove that the position reference command is perfectly tracked in spite of motor parameter uncertainties and load torque disturbance in control of the system that uses the new schemes. © 2015 Copyright © Taylor & Francis Group, LLC.
Iranian Journal Of Electrical And Electronic Engineering (17352827) 10(4)pp. 324-332
In Permanent-Magnet Synchronous Generators (PMSGs) the reduction of cogging torque is one of the most important problems in their performance and evaluation. In this paper, at first, a direct-drive vertical-axis wind turbine is chosen. According to its nominal value operational point, necessary parameters for the generator is extracted. Due to an analytical method, four generators with different pole-slot combinations are designed. Average torque, torque ripple and cogging torque are evaluated based on finite element method. The combination with best performance is chosen and with the analysis of variation of effective parameters on cogging torque, and introducing a useful method, an improved design of the PMSG with lowest cogging torque and maximum average torque is obtained. The results show a proper performance and a correctness of the proposed method. © 2014, Iran University of Science and Technology. All rights reserved.
IET Renewable Power Generation (17521416) 8(3)pp. 324-333
Increase in doubly fed induction generator (DFIG)-based wind farms degrades the short-term frequency regulation of power systems. However, such wind farms may have large amount of kinetic energy which can be rapidly injected into the power system to support system frequency by using an appropriate supplementary control loop. This study first analyses the impacts of DFIGs and their supplementary loop on power system short-term frequency regulation. Then, the average power system frequency model is modified to include the participation of wind farms in frequency control. Moreover, a new method is proposed to derive an analytical expression for minimum frequency of a power system, as an important index of frequency regulation, after a power imbalance occurrence. This analytical expression provides a tool for better insight into frequency behaviour of power systems with high levels of wind generation. The results of the analysis are verified by simulation of the nine-bus test system, using MATLAB/SIMULINK. © The Institution of Engineering and Technology 2014.
Madani, S.M. ,
Koofigar, H.R. ,
Arashnia A. ,
Sharafoddin A. ,
Arashnia A. ,
Madani, S.M. ,
Koofigar, H.R. ,
Sharafoddin A. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 470-475
Isolated single-stage, single-switch power factor correction have some advantages, such as fewer element count, higher efficiency, and lower oscillation output. Usually, linear controllers with limited bandwidth frequency are used for these types of converters. This controller degrades the converters performance after any sudden load change. The time required by the controller to respond to such a change is at least 2 cycles of input voltage, which cause defects such as intensive output the bulk capacitor voltage deviation. Conventional solution requires a large and costly capacitor. This paper proposes a 3 dimensional sliding surface (instead of sliding line), to improve the converter's performance during sudden load changes. The proposed method controls the switching frequency by adjusting bandwidth hysteresis modulation. Finally, the performance improvement of the method is verified by simulation. © 2014 IEEE.
IET Power Electronics (17554543) 7(3)pp. 745-752
This study presents a single-stage single-switch soft-switching converter based on boost-flyback power factor correction (PFC) scheme. In the proposed circuit, soft-switching condition is achieved by only an auxiliary winding on the transformer and a resonant capacitor without any extra switch. The converter operating modes are discussed in details. The design guidelines for the proposed PFC converter, are provided and simulation results are presented. A prototype of this converter is realised to justify the validity of theoretical analysis. © The Institution of Engineering and Technology 2014.
Journal of Power Electronics (15982092) 12(5)pp. 723-730
This paper presents a new ZVS single phase bridgeless (Power Factor Correction) PFC, using an active clamp to achieve zero-voltage-switching for all main switches and diodes. Since the presented PFC uses a bridgeless rectifier, most of the time, only two semiconductor components are in the main current path, instead of three in conventional single-switch configurations. This property significantly reduces the conduction losses,. Moreover, zero voltage switching removes switching loss of all main switches and diodes. Also, auxiliary switch turns on zero current condition. The presented converter needs just a simple non-isolated gate drive circuitry to drive all switches. The eight stages of each switching period and the design considerations and a control strategy are explained. Finally, the converter operation is verified by simulation and experimental results.
IEEE Transactions on Energy Conversion (08858969) 27(4)pp. 873-884
In this paper, coupling between active and reactive powers in conventional direct power control (DPC) strategies is analyzed and a new direct DPC method for doubly fed induction machine without rotor position sensors is presented. Coupling analysis is done on an improved DPC strategy with rotor flux controllers in the stator reference frame. The presented control strategy is done by controlling the rotor flux in the grid flux reference frame. The rotor flux command is calculated using a predicted stator flux, the stator current command, and the stator resistance. Moreover, the rotor position is estimated by comparing measured and estimated values of the rotor current. Furthermore, to reduce the methods sensitivity to the parameter inaccuracies, the mutual inductance of the machine is updated during the machine operation by the error between the magnitudes of the measured and estimated values of the rotor current. © 1986-2012 IEEE.
Madani, S.M. ,
Nabipour, M. ,
Zarchi, H.A. ,
Nabipour, M. ,
Zarchi, H.A. ,
Madani, S.M. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 410-415
A family of variable structure robust position tracking controller is presented for a three-phase synchronous reluctance motor (SynRM) considering the maximum torque control (MTC) strategy related to this motor. Neglecting the iron losses, the proposed controller is designed including one of the three classes of linear variable structure controller and adaptive input-output feedback linearization (AIOFL) approaches. Foremost, a sliding mode-plus-PI controller is used to obtain the stator current reference signal. For that stage, three classes of a PI-sliding controller are presented. These methods are then compared and its characteristics are specified and the optimum use for any case, determined. The presented position controller is fast response and robust against mechanical parameter uncertainties and load torque disturbance. At Second stage, the proposed sliding mode based AIOFL controller estimates the unknown electrical uncertainties without using sign(.) or sat(.) function. Hence, it reduces chattering or steady state error phenomenon. Finally, the effectiveness and feasibility of the proposed control approach is demonstrated by computer simulation. The results obtained confirm that the desired position reference command is perfectly tracked in spite of motor parameter uncertainties and load torque disturbance. © 2012 IEEE.
in this paper a new Direct Power Control method of the Doubly Fed Induction Machine without the use of rotor position sensors is presented. The method is based on estimating the stator flux in the rotor reference frame, and then applying the correct rotor voltages to obtain the desired rotor flux and power. Estimation of the rotor position is done by comparing the measured values with the estimated values of the rotor current. For this control method to have minimal sensitivity to parameter inaccuracies, the mutual inductance of the machine is also corrected during the process by an error signal produced by comparing the magnitudes of the measured and estimated rotor current. This will also ensures robustness against machine saturation and can be used to detect saturation in the machine. © 2011 IEEE.
IET Power Electronics (17554543) 4(6)pp. 732-741
This study presents a new zero-voltage-switching (ZVS) single-phase bridgeless PFC, using an improved auxiliary circuit to achieve ZVS for all main switches and diodes. Compared to other ZVS bridgeless PFC converters with no extra voltage and/or current stresses, the converter presented here uses lower component count. Since the presented PFC uses a bridgeless rectifier, there are only two semiconductor components in the main current path instead of three in conventional single-switch configurations. This property decreases the conduction losses, significantly. Moreover, ZVS removes switching loss of all main switches and diodes. Furthermore, since resonant current passes only through the auxiliary circuit, there is no extra current and/or voltage stress on the main switches and diodes. The auxiliary switch operates in zero-current conditions; therefore it does not introduce any switching loss. The presented converter just needs a simple non-isolated gate drive circuitry to drive all switches. Nine stages are explained for each ZVS switching period. Design considerations and a control strategy are also explained. Finally, the converter operation is verified by simulation and experimental results. © 2011 The Institution of Engineering and Technology.
Energy Conversion and Management (01968904) 52(1)pp. 590-595
This paper presents a new soft switching inverter with DC-link switch and one auxiliary switch. The important feature of this topology is that the switches voltage stress is lower than that of other quasiparallel resonant DC-link inverters. All diodes and switches are turned on and off under soft switching conditions. Auxiliary switch is turned on and off under zero current switching conditions, and the DC-link switch is turned on under zero voltage zero current switching condition and turned off under zero voltage switching condition. The proposed converter is analyzed and its operating modes are explained in details. The presented experimental results of a prototype converter confirm the theoretical analysis. © 2010 Elsevier Ltd. All rights reserved.
A nonlinear robust position tracking controller is presented for a three-phase synchronous reluctance motor (SynRM) considering the control strategy of maximum torque control (MTC) related to this motor. Ignoring the motor iron losses, the proposed controller is designed based on combination of linear variable structure and adaptive input-output feedback linearization (AIOFL) techniques. At first step, a sliding mode-plus-PI controller is designed for prediction of the stator current reference signal. The proposed position controller is fast response and robust against mechanical parameter uncertainties and load torque disturbance. At Second step, the proposed sliding mode based AIOFL controller estimates the unknown electrical uncertainties without using sign(.) or sat(.) function. Hence, it reduces chattering or steady state error phenomenon. Finally, the effectiveness and feasibility of the proposed control approach is demonstrated by computer simulation. The results obtained confirm that the desired position reference command is perfectly tracked in spite of motor parameter uncertainties and load torque disturbance. © 2011 AmirKabir Univ of Tech.
International Journal of Control, Automation and Systems (20054092) 9(2)pp. 301-309
Overhead crane movement results in suspended load sway, which may cause dangers and damages. Common anti-sway methods are based on swing angle information. This paper presents a novel method that uses load cell sensors for swing angle estimation. According to our proposed method, a damping signal is generated and added to the speed reference in order to suppress the suspended load sway. Conventional methods of swing angle estimation are based on measurement by camera vision, acceleration, or some other type of sensor. Compared to conventional methods, the proposed method based on load cell is simpler to build and less sensitive to ambient conditions. The effectiveness of the method is verified by computer simulation. Copyright © ICROS, KIEE and Springer 2011.
This paper investigates the contribution of Doubly-Fed Induction Generator (DFIG) based wind farms in short term frequency control of power systems. First, three features of DFIGs that make them capable to participate in frequency control are introduced. Then, a new effective method to exploit these capabilities is proposed. The method estimates the system active power imbalance, using system average frequency, and uses kinetic energy stored in the wind farm inertia to compensate it. The performance of the proposed method is evaluated by simulation using MATLAB/SIMULINK.
This paper presents a new series inductance interval (SII) PFC, using an auxiliary winding, to limit double power processing interval around the input voltage zero crossing. This limitation removes the unessential double processing power and consequently reduces the converter loss. Since the converter is a SII type, this converter has a limited voltage stress on the bulk capacitor and the converter can satisfy the IEC 6100 3-2 class D standard. The converter is analyzed, a design strategy is presented and the results are verified with PSIM simulation and experimental results.
This paper presents a new single-stage single-switch PFC using magnetic feedback to reduce the input current harmonic distortion and limit the voltage stress across the bulk capacitor. This topology uses a new magnetic feedback witch changes from one mode to another smoothly so the low frequency harmonic distortion will decrees significantly. The converter different modes are explained and results are verified with simulation and experimental results. ©2010 IEEE.
This paper presents a new ZCS single phase bridgeless PFC which uses an auxiliary circuit for achieving zero current switching conditions for all switches of conventional bridgeless PFC. The input current is controlled by a peak current controller and output voltage is controlled with a limited band pi controller. The proposed PFC uses a bridgeless rectifier therefore the conduction loss will decrease significantly. And with using zero Current switching the switching loss of all switches will be removed. The auxiliary switch turns on and off in zero current conditions so there is no switching loss on the auxiliary switches. Nine stages are described for each ZCS switching period. The results have been verified with PSIM simulation. © 2010 IEEE.
This paper presents new equivalent symmetrical components of a 48-pulse SSSC. Then, based on the presented model, apparent impedance of a transmission line during single phase to ground and phase-to-phase faults will be determined. The simulation results show the accuracy of the proposed model. Finally, the model is simulated, using MATLAB\SIMULINK.
Tabatabaei s.m., ,
Vahidi, B. ,
Hosseinian s.h., S.H. ,
Madani, S.M. pp. 253-258
This paper proposes a novel methodology for the optimal location and sizing of shunt capacitors in radial distribution systems. The optimization problem includes maximizing capacitor saving function, minimizing active power losses, and voltage profile improvement. The installation node is selected by Loss Sensitivity Analysis in a step by step procedure. An evolutionary algorithm known as bacteria foraging algorithm (BFA) is utilized for solving the multiobjective multivariable optimization problem and the optimal size of capacitor for selected nodes is determined. The proposed approach is applied to 34-bus distribution system as a test study and the results are compared with previous method. The results show that this method provides more economical solution by reducing power losses and total required capacitive compensation. ©2010 IEEE.
International Review of Electrical Engineering (25332244) 5(4)pp. 1670-1677
This paper investigates the impacts and contribution of doubly-fed induction generator (DFIG) based wind farms in power system frequency regulation. First, the negative impacts of increasing penetration of DFIG-based wind farms on power system frequency regulation are studied. Then, DFIGs' useful capabilities and control methods to contribute in system frequency control are presented. Considering the problems of conventional control methods, a new method for participation of DFIG-based wind farms in short term frequency control is proposed. The method uses "average frequency" to estimate power imbalance, quickly and precisely. Then, the kinetic energy stored in the wind farm inertia is exploited to compensate this power imbalance. Several simulations using a nine-bus test system are performed to demonstrate the effectiveness of the proposed method. © 2010 Praise Worthy Prize S.r.l. - All rights reserved.
The increasing penetration of variable speed wind turbines in Power grids results in reduction of the number of connected conventional power plants and system inertia consequently. This reduction affects frequency regulation of the grid. So new grid codes requires wind farms to participate in grid frequency regulation. This paper provides a new method to improve the contribution of DFIG based wind turbines in system frequency regulation. The method uses high kinetic energy stored in wind turbine and ability of DFIG to fast control of output power. This is done by introducing a supplementary loop to DFIG active power control loop. The effectiveness of the method is compared with other methods by simulation. ©2010 IEEE.
This paper presents a new low cost, highly efficient, reliable and compact motor drive topology for residential and commercial applications, such as building air-conditioning, appliances, ete. The drives consist of a three-phase permanent magnet brushless DC (BLDC) motor, a soft switching dc-dc converter and a three-phase inverter containing six siliconcontrolled rectifiers (SCRs). A micro controller or a digital signal processor (DSP) will be used to control the overall system. The proposed system is fault tolerant doe to its current regulated nature, where it can even withstand a solid short-circuit at its output terminals. The drive is low cost with respect to the commercially used IGBT-based systems. Since all the switches used in the output three phase inverter are current commutated, and the dc-dc converter uses soft-switching techniques, this drive has much lower switching losses than the conventional PWM drive. © 2009 IEEE.
Interior permanent magnet (IPM) synchronous machines attract attentions, due to their excellent torque/power density and high efficiency. Comparing to surface PM (IPM) machines, interior PM machines has higher flux weakening capability at high speed, which is suitable for vehicles. It is of interest to keep Constant Power Speed Range (CPSR) condition in wide speed range. Magnet segmentation proposed by several authors to increase IPM flux weakening capability. The basic idea is to provide proper paths for the stator d-axis flux (LdId) (or increasing d-axis inductance Ld) by thin iron-bridge between magnet segmentations. This paper proposes a new IPM rotor design which improves flux weakening while keeping rated torque at low speed. First, the sensitivity of negative d-axis current id in decreasing air-gap flux is evaluated by FEA. Then optimum positioning and sizes of new magnet-segmentations, air-bridges and iron-bridges are presented. The optimization result in removing the iron-bridge at the outer rotor circumference and adding equivalent iron-bridge width in between magnet segmentations. This has same mechanical rotor integrity strength while providing flux weakening without decreasing rated torque. Finally, the torque-speed characteristic is obtained and compared with similar method. © 2009 IEEE.
The brushless dc motor (BLDC) has been widely used in industrial applications because of its low inertia, fast response, high power density, high reliability, and maintenance-free reputation. They are usually supplied by a hard switching PWM inverter, with rather high switching loss. Therefore large heatsinks are required for dissipation of this switching loss which increase the volume and weight of the drive system. In order to reduce switching losses, many soft switching inverters have been designed by several researchers. Soft-switching circuits has other problems, such as excessive voltage stress, non-full PWM control and complexity in control scheme or implementation. This paper presents a simple soft switch inverter proposed which is applicable to battery-fed BLDC drive systems. This inverter has low switching-power loss, low voltage stress on the main switches, simple control scheme and easy to implement. After analytical analysis simulation results are shown to verify the theoretical analysis. © 2009 IEEE.
Torque pulsation reduction of Permanent Magnet Synchronous Motor (PMSM) is an important design issue. One component of this pulsation is cogging torque, which depends on magnetic configuration of stator and rotor (e.g., magnets and slots shape and dimensions). This paper presents a new physical and mathematical analysis of cogging torque for Surface Mount PM (SFPM) motor. Based on the analysis, a mathematical formula is derived for the cogging torque and verified by FEM simulation. Based on the presented analysis, a new method of air-bridge shaping to reduce cogging torque is presented for an Interior PM motor (IPM). The FEM result shows significant reduction of the cogging torque, due to new air bridge design. © 2008 IEEE.
Self Excited squirrel cage Induction Generator (SEIG), is used widely to convert mechanical wind energy to electricity, due to their low cost, small size, no need of separate dc source and brushes. This paper proposes a new reduced order model for small wind energy system consisting of: Squirrel Cage Induction with excitation capacitors, D-Statcom, loads and mechanical parameters. Comparing with conventional high order model, the presented model gives a physical insight and clearly describes the dynamic behavior of frequency and voltage of a SIEG supplied system during isolating from a power system grid. Based on the proposed model, qualitative analysis and controller design method for voltage and frequency control has been presented. These proposed controllers are applied on a 33kv wind energy system, and compared with high order model using MATLAB-Simulink. The simulation results verified the validity of the proposed models and control schemes. © 2008 IEEE.
Generating electrical power from wind energy is becoming increasingly important throughout the world. This fast development has attracted many researchers and electrical engineers to work on this field. Self Excited squirrel cage Induction Generator (SEIG), which uses an excitation capacitor, is used widely to convert mechanical wind energy to electricity, due to their low cost, small size, no need of separate dc source and brushes. This paper proposes a new simplified model for small wind energy system consisting of: Induction generator, D-Statcom, excitation capacitors and loads. The model clearly describes the dynamic behavior of frequency and voltage of a SIEG supplied system during fault and isolating from a power system grid. Based on the proposed model, efficient analytical schemes for voltage and frequency control has been presented. These controllers are applied on a 33kv wind energy system, using MATLAB- Simulink simulations. The simulation results verified the validity of proposed control schemes and models.
The transition of automotive industry from traditional combustion engines to hybrid vehicles and also research on renewable energies show a rapid need for more electrical machineries and consequently a huge demand for their condition monitoring and diagnostic systems. Prodigious improvement in signal processing techniques and availability of cost effective DSP hardware provide a road map for developing such systems. Primarily, these techniques depend upon locating specific features such as harmonics in line current, vibration signals, or thermal measurements. These features are then processed using modern classifiers and classification techniques. By removing correlations among features and harmonic contents, the classification result will be an indication of the health of system and or whether there is a need for maintenance. This paper provides a brief review of past and presents methods, and presents new analytical method to model and analyze broken bar fault of the IM. The method detects the existence and severity of broken bar fault in the line currents of an IM that yields a reliable feature for its fault classification. Theoretical results are verified by experiments and shown at the end of the chapter. © 2005 IEEE.
For years, design of conventional permanent magnet motors has been limited mainly to the variation of the stator winding function and little research has been made on stator pole modification as an alternative for motor design. Soft magnetic composites (SMCs) have opened up new possibilities for the 3-D pole shape design of both DC and AC machines owing to their isotropic properties, while having low conductivity. Here, a PM motor with trapezoidal shaped poles is presented and simulated. A modified trapezoidal-shaped poles is also proposed as further work, to reduce the torque pulsation. The latter theoretically exhibits zero torque pulsations. Some FEA results are also presented. © 2005 IEEE.
Conference Record - IAS Annual Meeting (IEEE Industry Applications Society) (01972618) 3pp. 1833-1838
This paper attempts to find an analytical solution for the problem of eccentricity in permanent magnet (PM) machines. The result is helpful in developing proper features in the detection of this kind of fault in a diagnostic package. The analysis starts with the modeling of air-gap eccentricity in PM machines and is supported with both experimental and finite element simulation results. The results show that eccentricity appears in the form of speed related harmonics and can be detected by variation in its second harmonics.
This paper presents a high- performance low-cost brushless dc (BLDC) motor drive for commercial and residential applications. The proposed drive employs less number of switches than the conventional converter and incorporates an active power factor correction feature which results in sinusoidal input current at close to unity power factor. The proposed converter has bidirectional capability, which improves speed control features of the drive. Moreover, a new PWM current control system, with regenerative braking capability is proposed. Finally, simulation and experimental results are given to verify the proposed developed methods.
This paper presents a new method to determine the electromagnetic characteristics of slow release B1 relay, which is used in US railway (Fig. 1). This relay operates few seconds after it is energized or de-energized. The slow operation of this relay is accomplished by short circuits loops around the magnetic core of the relay (Fig. 2). The operation of the B1 relay is highly affected by electromagnetic characteristics of the relay, therefore, this research aimed to obtain the B-H or equivalently λ-I. curve of the relay core. Since the relay has short circuit loop around its core, it is not possible to obtain its λ-I curve by conventional methods. Thus, different methods have been proposed, and finally the most efficient one is chosen and explained further in this paper.
Modern power system networks often consist of multi-loop structures. The coordination of protective relays in such networks is an iterative and time consuming process. To minimize the number of iterations, a proper set of relays, referred to as Break Point Set (BPS), with a minimal size is required to start the coordination procedure. This paper presents a new graph-theoretical method for the BPS determination. The method represents the primary/backup relation among relays by a directed graph, referred to as dependency-diagram. This representation converts the BPS determination to a problem of graph theory. The method approaches step by step to a minimum and/or a near-to-minimum BPS, choosing the best break point relay at each step. The graph-theoretical rules of the method exploit the sparsity of the relations among the relays and reduce the complexity of the problem. Due to the generality of the method, it can be easily applied to any protection schemes and network configurations.
IEEE Power Engineering Review (02721724) 18(6)pp. 43-45
The coordination of protective relays of multiloop networks is a tedious and time consuming process. The complicated part of this process is the determination of a set of relays referred to as the break-point set (BPS), with a minimal size to start the coordination procedure. This letter introduces a new graph-theoretical approach to determine the BPS. This method reduces the complexity of the problem, by exploiting the available sparsity of the dependencies among relays in protection systems.
EUT Report, Eindhoven University of Technology, Faculty of Electrical Engineering (09298525) (98 -E-309)
The basic task of a electrical power system protection is to detect faults in system components, and to rapidly isolate them by opening all incoming current paths. On the other hand, in the case of any fault, the protection system should disconnect only a minimum number of components, to minimize interruptions to consumers. Therefore, relays of a protection system should be adjusted for the minimum possible operation time, while maintaining coordination among all relays. Modern power system networks are often multi-loop structured. Coordinated setting of protective relays in such networks is tedious and time consuming. The complicated part of this problem is the determination of a minimum set of relays, the so-called minimum Break Point Set (BPS), to start the coordination procedure. This report presents a new graph-theoretical method to determine a minimum or a near-to-minimum BPS. Using the rules of this method, the determination of a minimum BPS can be reduced and decomposed into sub-problems. Owing to the efficiency of these rules, the presented method quickly achieves the result, even for large networks. Moreover, due to the simplicity of the method, it can be manually applied to the graph of each network. Since the presented rules are general, they can be applied to improve any method dealing with BPS determination.
Throughout the history of power system protection' improvements have continuously been made to most aspects of the protection system. However' the selection of type and characteristics of the protective relay are still carried out by specialists based on their experience. Since the applied design methods are strongly impacted by the personal philosophy of the designer' most of the existing protection systems are not optimal. In this paper' a new method will be presented to achieve an optimal protection system for an arbitrary network configuration' based on graph-Theoretical tools.an example. In this simple case' a selective protection only requires an overcurrent definite-time function for each relay location. In this case' relays rj' rj and r4 do not backup any relays' and can be adjusted for the shortest operation time (without delay). But relay r3 must take over the function of backup for r^ and rj-Therefore to achieve selectivity' r^ must operate after rj and r'. This can be realized by adding a time delay (i.e. zc=0.3 sec.) to ry In the same way' r^ should operate after ry and needs an additional delay of at least 2. © 1998 Institute of Electrical and Electronics Engineers Inc. All Rights Reserved.
IEE Proceedings: Generation, Transmission and Distribution (13502360) 145(6)pp. 717-721
Modern power system networks are often multiloop structured. Co-ordinated setting of overcurrent and distance protective relays in such networks is tedious and time consuming. The complicated part of this problem is the determination of a proper minimum set of relays, the so-called minimum break-point set (BPS), to start the co-ordination procedure. The paper presents a new graph-theoretical method to determine a near-to-minimum or a minimum BPS. Using the lemmas of this method, the determination of a minimum BPS can be reduced and decomposed into subproblems. Owing to the efficiency of these lemmas, the presented method quickly achieves the result, even for large networks. Moreover, due to the simplicity of the method, it can be manually applied to the graph of each network. Since the presented lemmas are general, they can be applied to improve any method dealing with BPS determination. © IEE, 1998.
Throughout the history of power system protection, improvements have continuously been made to most aspects of the protection system. However the choice of the protection function and the type selection are still carried out by specialist based on their personal experience. Since the applied design methods are strongly impacted by the personal philosophy of the designer, most of the existing protection system are not always optimal. In this paper a new method will be presented which is based on exact rules of the graph theory to achieve (at least near to) an optimum protection system for an arbitrary network configuration.
IEE Conference Publication (05379989) (434)pp. 70-73
Up to now the design of power system protection is done by experts. Despite using software tools like relay coordination program, the design process is mostly based on personal experience. Therefore the design of the most existing protection systems are not always optimal. In this paper a new method will be presented which is based on exact rules for obtaining an optimal design.
