Four Leg DSTATCOM based on Synchronous Reference Frame Theory with Enhanced Phase Locked Loop for Compensating a Four Wire Distribution Network under Unbalanced PCC Voltages and Loads

摘要

This paper presents a Distribution Static Compensator based on Four Leg Voltage Source Inverter (4-leg VSIDSTATCOM) with controlling by Synchronous Reference Frame theory (SRF) in the dq0 frame with Enhanced Phase Locked Loop based on Self-Tuning Filter (EPLL-STF) used for compensating four-wire distribution systems. The proposed 4-leg VSI DSTATCOM is used for load balancing, source harmonics filtering, reactive power compensation and power factor correction, and source neutral wire current compensation at the point of common coupling (PCC) in the four-wire distribution network under unbalanced linear loads and nonlinear load variation with various source and PCC voltages conditions. The new SRF theory with EPLL based on STF is used for harmonics current extraction and good estimation of PCC voltages without harmonics under unbalanced PCC voltages and loads. Three dimensional space vector modulation (3D SVM) is used to generate the gate switching pulses for the 4-leg VSI and to circumvent the problems of the switching frequency variant, and for DC bus voltage capacitor and compensating 4-leg VSI DSTATCOM currents we are going to use the PI controller (Proportional-Integral). The effectiveness of the proposed 4-leg DSTATCOM under unbalanced PCC voltages and loads with various control strategies are demonstrated through simulation using sim-power-system and S-Function integrated in Matlab simulink.