Resonance Suppression Method for Grid-Connected Converter With LCL Filter Under Discontinuous PWM

This paper presents a resonance suppression method that reduces current oscillation incurred by the LCL-filtered grid-connected converter’s discontinuous PWM (DPWM). First, the cause of LCL resonance is analyzed with an aspect of frequency and time domain for DPWM scheme. Then, voltage references are manipulated to decrease the resonance problem. In the proposed method, pole voltage references at the edge of offset voltage are slightly adjusted to reduce the current oscillation. In addition, a perturb and observe (P&O) technique is adopted to search the magnitude of an edge voltage. Through the simulation and experimental tests, the current oscillation is dramatically reduced while keeping the advantages of DPWM scheme. The proposed method can minimize the switching frequency under the grid harmonics regulation.