Parallel coordination control of multi-port DC-DC converter for stand-alone photovoltaic-energy storage systems

Aiming at the low inertia DC micro-grid poor bus voltage quality and the energy storage SOC balanced problem, considering the urgent demand of high up/down ratio, electrical isolation and high-efficiency converter for distributed micro-source. An improved virtual capacitor (IVC) parallel coordination control strategy based on multi-port isolated DC-DC converter is proposed. First, MPIC is used to replace the traditional Buck/Boost circuit to achieve the electrical isolation from the micro sources of the energy storage system. Secondly, by analogy of IVC control, design the control frame of single voltage outside circle and multiple currents inside the ring, IVC control suitable for Four-port isolated DC-DC converter(FPIC) is obtained. Then, the parallel and coordinated control strategy under the control of IVC for multiple energy storage interface converters is established.