State of charge control for energy storage by use of cascade control system for microgrid

The hybrid control system, which is a combination of cascade control and local control, is proposed as a method to compensate power fluctuations caused by load and renewable energy sources in a microgrid using distributed power generation systems (DGs). When energy storage system (ESS) such as EDLC is used in the microgrid to compensate power fluctuations, its state of charge (SoC) should be controlled. In this paper, a new method to control ESS's SoC which would enable power compensation with less energy capacity and with less effect to the compensation result is proposed. This method uses the feature of the cascade control that faster DG's reference is dependent on slower DG's output. The new method is implemented on EDLC in the model microgrid and its effectivity is verified by a simulation and a experiment. The result of the simulation and experiment is also reported in the paper.