Grid-connected photovoltaic (PV) systems impose challenges like voltage fluctuations, low system inertia, and power quality issues. The need to tackle these challenges led to the introduction of flexible power point tracking (FPPT), where the PV power output is controlled by an energy management system, rather than solely operating the PV systems on the maximum power point. The requirement of fast transient response implies that algorithms such as the one proposed in this article are desirable. The proposed algorithm uses the secant method to achieve significantly improved results in comparison to the existing methods. The method also simplifies the prediction of variations during changes in the environment and power reference, hence, results in reduced oscillation around the set-point and faster convergence. Experimental validation is presented in this article for supporting the claims. The results in terms of accuracy, convergence rate, steady-state oscillations, and cumulative error are bench-marked against one of the most recent FPPT methods.

This paper reviews a family of power electronic high voltage gain dc-dc boost converters. The dc-dc boost converter acts as an interface between the renewable sources and the utility grid. Over the last few years, many topologies have been developed on the basis of boost converter topology. Among these, some important topologies are discussed and compared with various parameters such as voltage gain, switching element stress, voltage stress on the diodes, and component count. Conventional boost converter topology starts with switching voltage multiplier techniques and then introduces a coupled inductor. Several topologies have been developed by integrating these coupled inductors with voltage multiplier circuits to achieve a high voltage gain and reduce stress. This work provides an introduction, framework, and review of high voltage gain power electronic dc-dc boost converters.

This article investigates the photovoltaic fed universal active power filter (PV-UAPF) system for enhancing power quality indices. A novel comb filter together with second-order generalized integrator (CFSOGI) based instantaneous power balance theory with power angle (IPBTPA) control scheme is implemented. Under distorted or adverse grid conditions, the CFSOGI effectively extracts the phase angle, frequency, and fundamental positive and negative sequence components (FPNSC) to overcome the limitations of adaptive notch filters. Here, a comb filter constitutes a cluster/group of zeros at multiple harmonic frequencies to achieve notch peaks thereby providing superior harmonic rejection ability. Whereas, IPBTPA generates the reference signals to operate the system at dual compensation strategy with or without solar PV. The power angle is used to extract the desired load voltages under grid voltage fluctuations thereby reducing the burden on the shunt converter. Moreover, the hysteresis controller generates the switching pulses based on the calculation of reference and load powers which improves the dynamic performance by maintaining system power balance and effective DC voltage regulation. Besides, reactive power compensation, suppression of harmonic currents and mitigation of grid voltage fluctuations is also carried out to strengthen the system further. The system is also tested in grid voltage interruption for islanding mode to realize a microgrid system. The overall system performance is also validated using simulation and in a real-time experimental set-up, and results are demonstrated under various conditions.

This article presents a single-switch high step-up quadratic DC-DC converter for DC microgrid applications. The quadratic boost converter is integrated with switched capacitor cell along with coupled inductor to achieve high gain at reduced duty ratio. The switched-capacitor cell is composed of two diodes and two capacitors. The capacitors charge in parallel and discharge in series to increase the converter’s gain. The coupled inductor turn ratio can be increased to elevate the converter’s gain further. The inductor at the input minimizes the current ripples and makes the input current to be continuous. Moreover, the proposed converter works as a passive clamp circuit to minimize large voltage spikes across the switch (MOSFET) and it has low $R_{ds}$ (on-state) to minimize the conduction losses. As a result, the device’s rating improves, losses decrease, and it becomes less expensive to switching devices of the converter. The energy leakage of the coupled inductor is recycled to the output capacitor, it can reduce the reverse recovery issue in diodes and increases efficiency of converter further. The proposed converter working principle and its analysis are explained with different operating modes. The performance of the converter is validated with laboratory hardware setup with rating of 160W. Here, the input and output voltages are considered at 20V and 400V, respectively. Finally, the superiority of the proposed converter is compared with existing literature in terms of gain, stress across various components, switching performance and efficiency.