Research Output
Articles
Publication Date: 2024
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.
Publication Date: 2024
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.
Publication Date: 2024
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.
Publication Date: 2023
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.
