Energy management of hybrid DC and AC bus linked microgrid

Abstract

This paper focuses on the energy management system in distributed generation of microgrid, and describes the power management strategies of the different converters in grid-connected, islanded and transition operations. The microgrid consists of wind turbines, photovoltaic panels, batteries and super-capacitors, also includes both AC and DC zones. One of the most important things is keeping the voltage of DC and AC bus steady. When microgrid is connected to the utility grid, DC-bus voltage is regulated by the inverter. And the magnitude and frequency of AC bus are the same with the grid. However when the microgrid works in island operation, DC-bus voltage must be regulated by microsouces and storages. The magnitude and frequency of AC bus are controlled by droop character of parallel inverters. Because of the fluctuation of renewable energy such as wind turbine and photovoltaic, a fast-dynamic storage system is needed. In order to keep supplying power to the local loads in island operation, a long-term storage system is needed. All of microsouces and storages are connected to DC bus by different converters. The converters must be controlled well to keep power balance, especially during the island operation.