An optimized synchronous approach to DC/DC droop backstepping control considering voltage compensation in DC microgrids

Abstract

This paper addresses the impact of widely distributed power electronic loads and their constant power operations on the stability of DC microgrids. A backstepping controller, based on droop control, is proposed as a solution for mitigating the issues of constant power load in these grids. The unique feature of this controller is its independence from inter-device communication, which enhances the expandability and scalability of the DC microgrid. To tackle the challenge of power side converters needing a subsequent level DC/DC converter for voltage adjustment, a synchronous optimization method is introduced. This method, incorporating voltage compensation, keeps track of local output power during system transients. It identifies when the droop coefficient ratio deviates from proportionality, using this deviation as the initiation point for algorithm optimization. This approach modifies the local droop curve, enabling synchronous optimization. Before being optimized, the controller under heavy load conditions cannot meet the requirements of maintaining bus voltage and accurately allocating power simultaneously. However, after optimization, the system can maintain bus voltage while still ensuring accurate power allocation after disturbances. Moreover, the controller before optimization requires a secondary DC/DC converter to transfer electrical energy from the variable DC bus to the main bus. The optimized controller can effectively eliminate voltage offset and directly connect the DC/DC converter to the main bus, eliminating the cost problem caused by the secondary converter.