Comparative Stability Analysis for Common Grid-Connected PV Inverter Control Strategies

When connected to distribution networks with distorted grid voltages, inverters can easily produce high levels of current harmonics. When these networks have high interface impedances, the control schemes designed to mitigate these harmonics can become destabilized. This paper compares the relative stability of several different control schemes used for this purpose. Specific comparisons are made when connected to a purely inductive grid with impedance as high as 10% per unit. The paper compares multiple resonant control, repetitive control, and a new multirate control scheme.