Simulation of three-phase grid connected parallel inverters with current error compensation control

Switching frequency of the inverter is increased in order to transfer high quality current to the grid. Increasing switching frequency decreases the efficiency of the power converter. In this paper, two inverters are connected in parallel to transfer high quality current to the grid. L filters are connected between inverters and the grid to filter current, thus simple control techniques can be used in these inverters. The first inverter operates as a main inverter, and the second one operates as an auxiliary inverter. The main inverter produces grid reference current, and the auxiliary inverter is utilized to compensate the main inverter current error. The main inverter has high power capacity, and operates at low switching frequency; on the other hand the auxiliary one has low power capacity, and operates at high switching frequency. The advantages of the proposed system are simple control technique and high efficiency. The proposed system and control scheme is simulated in MATLAB/Simulink for 10 kW. Simulation results shows that the two inverters connected in parallel can be controlled with the proposed control scheme and the THD value is limited to less than 5%.