A self-convergence droop control of no communication based on double-quadrant state of charge in DC microgrid applications

Abstract

With the consideration of a line resistance in a DC microgrid, the state of charge (SoC) of batteries will not be consistent with each other due to the voltage drop in the line resistance. In this paper, a model of a DC microgrid including detailed distributed generation models is established first, which can present the mechanism characteristic of different distributed generations. Then, a self-convergence droop control of no communication based on double-quadrant SoC is proposed to solve the problem modifying the charge/discharge rate with SoC itself and line resistance. After operating for a while by adopting this proposed method, the SoC of batteries in the DC microgrid can converge to the same value itself without need for a communication system to exchange data with each other. Meanwhile, the output/input power of batteries can be equalized. Therefore, the lifetime of batteries can be prolonged and the overuse of batteries can be avoided in this situation. Also, the system reliability is improved. Finally, the test results of a DC microgrid with a photovoltaic cell, a fuel cell, and two batteries in the RT-LAB real-time platform are shown to verify this approach.