A Novel Bus Current-Based Series Virtual Impedance Method to Enhance Stability of DC Distribution Power System in All Operation Modes

In a DC distribution power system (DPS), various power electronic converters work together and make the DPS have a great opportunity to operate in multiple operation modes. The interaction among power converters has a high risk of causing oscillations, which can even occur at more than one mode. Although existing virtual impedance solutions are capable of providing a desired amplitude or phase margin to stabilize the DPS under a specified condition, it is challenging for designers to compensate for impedance at all different modes. To solve it, this paper systematically analyzes the compensation capability of the traditional series virtual impedance (SVI) method, and then the design boundary is derived and proved in a DPS with two typical unstable operation modes. To eliminate this boundary, a novel bus current-based SVI (BC-SVI) method is proposed in this paper by feeding back the DC bus current to construct a general virtual impedance in any sole-mode converter. Then, the stability of DPS can be enhanced under different operation modes. Finally, an experimental prototype system is built to validate the proposed method.