PV interface system with LVRT capability based on a current controlled HFAC link converter

Abstract

The paper presents a current controlled High Frequency AC (HFAC) link based on Matrix Converter (MC) to interface a photovoltaic (PV) system with the grid. The proposed switching scheme for the MC is based on the hysteresis current control and the sign of the input voltage waveform. A strategy for controlling the HFAC link converter to extract the maximum power by regulating the terminal voltage of the PV array is presented. In addition, the proposed strategy mitigates the voltage fluctuations at the Point of Common Coupling (PCC), resulted from the variation in the harvested active power from the PV. Moreover, the proposed interface system supports the grid with the necessary reactive power needed for the Low Voltage Ride-Through (LVRT) to meet the grid code requirements. The proposed control system is based on a signal processing unit to estimate the PCC voltage magnitude and phase angle, simultaneously, which supersedes the rms calculator and Phase Locked Loop (PLL) circuits. Furthermore, the estimated PCC voltage is utilized for instant sag detection to enable the LVRT controller. Simulation results based on MATLAB/SIMULINK software are provided to verify the effectiveness and to evaluate the dynamic behavior of the proposed PV interface system.