Improvement of hybrid grid-connected inverter control scheme with active power injection and power quality improvement in order to operate in weak grid conditions

In this paper, the operation of hybrid grid-connected inverter has been improved by changing the control scheme. Hybrid grid-connected inverter -HGCI-, which injects active power and compensates power quality problems, needs low DC link voltage because of thyristor-controlled LC filter in the output branch. This structure uses instantaneous reactive power theory which doesn’t perform well in distorted grid voltage condition. Hence, in these conditions, HGCI can’t inject active power and improve power quality. In this paper, Recursive digital filter method is used to improve HGCI in a way that operates in weak grid voltage. Instantaneous reactive power theory and recursive digital filter are both simulated in MATLAB/SIMULINK and the results are presented. Simulation results prove the satisfactory operation of HGCI in weak grid conditions.