DCI Suppression strategy of three-phase grid-connected PV power generation system based on electrolytic capacitor

The issue of direct current injection(DCI) which is introduced in the transformless non-isolated PV generation system can decrease the quality of the output power, however, inadequate attention is focused on this problem. A new method is proposed based on electrolytic capacitor in order to suppress DCI, and non-ideal vector proportional-integral(NIVPI) controller is adopted to control the voltage of the electrolytic capacitor. The 17kVA 640VDC/220V50HzAC PV inverter is adopted as the plant, and the prototype and Matlab/simulink are both developed to confirm the effectiveness of the theory.