Stability Evaluation of the Dual-terminal Structure DC Distribution Power Systems with Multiple DC Transformers

To improve the load capability, operating efficiency and power density of the DC distribution power systems (DDPSs), the application of dual-terminal structure (DTS) composed of multiple DC transformers (DCTs) is widely expanding. Focusing on the cascaded stability, the active damping methods for DCTs are widely researched to suppress the oscillation. However, there are few studies discussing whether the DDPS composed of DCTs controlled by active damping methods is still stable. Therefore, this paper firstly builds an impedance model for a DTS DDPS. Then, the stability of a DTS DDPS composed of all-active-damping-controlled DCTs is evaluated based on the Nyquist Criterion. Finally, simulation results show that a DTS DDPS is stable with a high margin when composed of all-active-damping-controlled DCTs, which has fast dynamic speed and good balance ability.