Harmonic Current Suppression Strategy for Grid-Connected PWM Converters With LCL Filters

As for a grid-connected PWM converter with LCL filter, harmonic current can flow freely into the grid-side inductor and filter capacitor, when the connected power grid is harmonically distorted. The fact lies in that the conventional control scheme has a little ability to suppress the grid current harmonics. Though the harmonics can be suppressed by the capacitor current compensation method, it may lead to system stability issues. This paper proposes an improved harmonic suppression scheme with the partial capacitor current feedforward, which can effectively suppress the specified grid current harmonics on the premise of ensuring the system stability. Since the partial capacitor current is obtained as the differential output of a multi-second-order generalized integrator, no extra current sensors are needed. The effectiveness and feasibility of the proposed strategy are verified by detailed experimental results.