An improved DPWM method for reduction of resonant problem in the inverter

This paper proposes an improved discontinuous PWM (DPWM) algorithm. The modulation signal of the conventional DPWM changes discontinuously and has many harmonic components. If these harmonics components and the resonant frequency band by a grid-connected LCL-filter are overlapped, the grid current oscillates. To solve this problem, the proposed method uses the 6-th harmonic injection technique to the modulation signal. As the proposed method is used, the modulation signal changes smoothly and the harmonic components is sufficiently reduced. The proposed DPWM method is verified from the PSIM simulation with a 10 kW photovoltaic (PV) power conditioning system (PCS).