Virtual resistor based active damping of LC filter in standalone voltage source inverter

Output LC filter effectively mitigates higher order harmonics in the output of voltage source inverters employing pulse width modulation. The presence of the LC filter introduces stability concern due to the resonance, with options for damping by passive or active methods. The active methods feature lossless damping without the hardware change. Virtual resistance based active damping methods emulate the physical behavior of a resistor in the control loop. Conventional design methods involve sequential selection of the virtual resistance loop and voltage loop controller parameters. This paper jointly analyses the relation between voltage controller parameters and virtual resistance, and their effect on the open loop gain and phase margin. Such an approach for controller design results in increased system bandwidth. Based on the transfer function analysis, a novel control design methodology is proposed. Experimental results are provided that validate the proposed control methodology.