Energy management in DC microgrid with an efficient voltage compensation mechanism

Direct current (DC) microgrid facilitates the integration of renewable energy sources as a form of distributed generators (DGs), DC loads, and energy storage system (ESS) devices. A new voltage compensation mechanism is presented in this study to resolve the control issues of DC microgrid in a distributed manner. In this mechanism, a fractional-order voltage compensation term is used in the outer controller loop which eliminates the voltage deviation in the steady-state condition. A detailed mathematical model is developed for the ESS along with the new voltage compensation controller to facilitate proper tuning of the control parameters. Since the proposed voltage compensation term guarantees autonomous bus voltage restoration, the supercapacitor state of charge (SoC) remains at nominal value without violation while it only buffers fluctuating power. However, the battery only compensates for the nominal power demand. The DG power control algorithm strictly maintains the battery SoC within lower and upper bounds. A DC microgrid comprising hybrid ESS, DC load, constant power load (CPL), and distributed generator is implemented with real time digital simulator (RTDS). The results show that the proposed controller is reliable, leading to excellent ESS performance and power management within the microgrid, without any DC bus voltage deviation.