Parallel control strategy of energy storage interface converter with virtual DC machine

Abstract

To improve the inertia and damping properties of the energy storage units (ESUs) interface converters in DC microgrids, an enhanced virtual DC machine (VDCM) control technique based on traditional P-U droop control is proposed in this paper. The control scheme actively introduces additional inertia and damping to the converter by equivalently analogizing the P-U droop control of the energy storage converter with the speed control of the DC machine. With the proposed control scheme, the operation stability of the DC microgrid can be improved effectively. Due to the problem that the energy storage interface converter under VDCM control cannot achieve power distribution, a coordinated control method of power proportional distribution of parallel energy storage converter is proposed. A small signal model is established to analyze the influence of control parameter changes on system performance. The effectiveness of the proposed method is verified by the simulation, the results show that the proposed strategy can actively introduce greater inertia and damping for the converters to improve the inertia and damping characteristics of the energy storage converter. At the same time, it can play a dynamic adjustment effect when the energy storage interface converters are connected in parallel, which can make each converter distribute power according to the set proportion in the three working modes of charging, discharging and charging and discharging switching.