Articles
IEEE Access (21693536)12pp. 84374-84386
Maximum power point tracking (MPPT) techniques are regarded as an important component of photovoltaic systems (PVSs) to extract the output power of a photovoltaic array. Algorithms based on perturbation suffer from the tradeoff between steady-state oscillations around (MPP) and the tracking speed. In this article, a fuzzy logic controller (FLC)-based Adaptive P&O MPPT algorithm for PVSs with fast tracking and low oscillations under rapidly irradiance change conditions are developed. When the operation point reaches a steady state, the proposed method can halt any artificial perturbation. Consequently, no oscillations around the MPP, and energy loss is reduced compared with conventional perturbation-based algorithms. The proposed algorithm can detect any change in irradiance without using additional sensors by employing a technique called drift avoidance. In addition, the FLC creates variable step sizes adaptively to accomplish speedy, accurate convergence to the MPP under normal and changeable weather circumstances. In a MATLAB program environment, the suggested method is simulated. DSP TMS320F28335 is used to validate that the proposed algorithm can monitor MPP with a low settling time, low steady-state oscillations, and a high convergence rate at the operational point. © 2013 IEEE.
Haghighat, M.,
Niroomand, M.,
Tafti, H.D.,
Townsend, C.D.,
Fernando, T. Journal of Modern Power Systems and Clean Energy (21965420)12(1)pp. 1-21
To maximize conversion efficiency, photovoltaic (PV) systems generally operate in the maximum power point tracking (MPPT) mode. However, due to the increasing penetration level of PV systems, there is a need for more developed control functions in terms of frequency support services and voltage control to maintain the reliability and stability of the power grid. Therefore, flexible active power control is a mandatory task for grid-connected PV systems to meet part of the grid requirements. Hence, a significant number of flexible power point tracking (FPPT) algorithms have been introduced in the existing literature. The purpose of such algorithms is to realize a cost-effective method to provide grid support functionalities while minimizing the reliance on energy storage systems. This paper provides a comprehensive overview of grid support functionalities that can be obtained with the FPPT control of PV systems such as frequency support and volt-var control. Each of these grid support functionalities necessitates PV systems to operate under one of the three control strategies, which can be provided with FPPT algorithms. The three control strategies are classified as: constant power generation control (CPGC), power reserve control (PRC), and power ramp rate control (PRRC). A detailed discussion on available FPPT algorithms for each control strategy is also provided. This paper can serve as a comprehensive review of the state-of-the-art FPPT algorithms that can equip PV systems with various grid support functionalities. © 2013 State Grid Electric Power Research Institute.
PCIM Europe Conference Proceedings (21913358)2024pp. 74-83
Power cycling is typically performed by periodically self-heating a power device using a DC current. This paper demonstrates a technique to boost the heating power to shorten the heating phase, by the addition of switching loss. This power cycling technique is demonstrated on 190 mΩ, 600 V Gallium Nitride (GaN) discrete devices, where it achieves 240,000 thermal cycles per week with a junction temperature swing ∆TJ of 100°C, and where the device remains integrated in a switching converter. The device under test is heated rapidly from 30°C to 130°C in 0.5 s, by hard-switching at 1 MHz, at rated current and 400 V. An optimized thermal path cools the junction back to 30°C in 2 s. The junction temperature is closed-loop controlled to maintain an approximately constant temperature swing. This requires junction temperature sensing with low ms-scale latency, implemented here using peak turn-on di/dt as the junction temperature indicator. The inferred temperature is fed into a control system that governs the heating and cooling durations. The resulting closed-loop-controlled heating time is shown to be a sensitive real-time indicator of device change. The paper discusses the practicality of temperature calibration methods, in light of temperature-sensitive electrical parameters’ known drift and sensitivity to bias temperature instability, and the problem of self-heating during calibration. Experimental results show one GaN device surviving 400,000 cycles with a ∆TJ of 102°C with no apparent thermal degradation, and another GaN device cycling at a ∆TJ of 136°C, whose heating duration reduces from 500 to 10 ms over the course of 30,000 cycles, indicating an apparent degradation of the device’s thermal properties. © VDE VERLAG GMBH · Berlin · Offenbach.
