Energy capacity reduction of energy storage system in microgrid stabilized by cascade control system

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 with distributed power generation systems (DGs). The use of energy storage system (ESS) such as EDLC facilitates power compensation. However, since the energy capacities of these components are limited, the contol of their state of charge (SoC) is necessary. 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 dependant 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 in islanding mode is also reported in the paper.