Grid-voltage-feedforward active damping for grid-connected inverter with LCL filter

Abstract

For the grid-connected voltage source inverters, the feedforward scheme of grid voltage is commonly adopted to mitigate the current distortion caused by grid background voltages harmonics. This paper investigates the grid-voltage-feedforward active damping for grid connected inverter with LCL filter. It reveals that proportional feedforward control can not only fulfill the mitigation of grid disturbance, but also offer damping effects on the LCL filter resonance. Digital delays are intrinsic to digital controlled inverters; with these delays, the feedforward control can be equivalent to a damping resistor and a reactance paralleled with filter capacitor. The damping performance in different frequency regions are discussed through Bode diagrams. Compared to other widely used active damping strategies, no extra sensor is needed because the Point of Common Coupling (PCC) voltage is sampled for Phase Locked Loop (PLL). Simulation and experiment results are provided for verifying the theoretical analyses.