Active Damping Control of Cascaded DC Converter in DC Microgrids Based on Optimized Parallel Virtual Resistance

In dc microgrid, the cascaded dc system has been extensively employed. However, the negative impedance characteristics of the converter may induce system instability. This article proposes an optimized parallel virtual resistance (PVR) based active damping control to improve the stability of the cascade dc system in the dc microgrid. The advantage of this method is that it not only meets the closed-loop dynamic performance of the source converter (SC), but also meets the stability requirements of matching the input impedance of the load converter. The stability range of PVR under full load and its influence on the output impedance of SC in cascade system are determined. Additionally, a large-signal model is constructed by using state-space averaging method to investigate the open-loop stability in the cascaded dc system. The suggested control stability requirements are investigated by using the Lyapunov indirect approach, and a matching PVR is then adopted to ensure system stability. Finally, the performance of the control strategy is verified by establishing a MATLAB simulation and experiment platform.