Proportional derivative based stabilizing control of paralleled grid converters with cables in renwable power plants

Resonant interactions of grid-connected converters with each other and with cable capacitance are challenging the stability and power quality of renewable energy sources based power plants. This paper addresses the instability of current control of converters with the multiple resonance frequencies consisting in LCL filters and cables. Both grid and converter current controls are analyzed. The frequency region, within which the system may be destabilized, is identified by means of the impedance-based stability analysis and frequency-domain passivity theory. A proportional derivative control strategy is then proposed to stabilize the system. Simulation case studies on four paralleled grid converters and experimental tests for two paralleled grid converters are carried out to validate the performance of the proposed control.