Three Level Hysteresis Current Controlled VSI for power injection and conditioning in grid connected solar PV systems

Abstract

The penetration of solar Photo Voltaic (PV) systems to the grid is gradually being increased as an alternative to conventional energy sources. The interfacing of solar PV systems to the grid requires efficient control strategies for the operation, control and Power Quality (PQ) improvement. This paper proposes a three-level Hysteresis Current Control (HCC) strategy for grid connected four leg Voltage Source Inverter (VSI). The main objective of three-level HCC for VSI is to perform solar power injection as well as power conditioning such as compensation of harmonics, reactive power, neutral current and current imbalance. Conventional HCC suffers from variation in switching frequency, whereas the three-level HCC exhibits a considerable reduction in switching frequency variation by considering offset hysteresis band, thus enhances the control performance. Here a three phase four wire supply system connected to both linear and nonlinear unbalanced loads are considered. The efficacy of the proposed control concept is demonstrated with different operating conditions using MATLAB/Simulink© simulation studies.