Active damping of oscillations in LC-filter for line connected, current controlled, PWM voltage source converters

Presented is a method for active damping of oscillations between line reactance and filter capacitors in LC-filter for line connected current controlled pulse width modulated (PWM) voltage source converters. The idea is to include closed loop feedback control that controls the capacitor voltage oscillations to zero by adding damping components to the current references. The voltage oscillations are calculated from manipulated measured filter capacitor voltages (using phase locked loop (PLL), Park- and inverse Park-transformation, low pass filtering and summation). The advantage of such an approach is that the higher oscillation frequency components can be controlled independently of remaining converter control. It is only the higher frequency components that are controlled by this additional closed loop voltage control. Further, additional measurements and increased converter rating are not required. Simulations and measurements presented in this paper show that the method works as intended. If active damping is implemented, then the voltage quality at the point of converter connection is maintained also in cases were filter oscillations is to be expected when the LC-filter is introduced.