Selection of capacitance for stable operation of low power DC system with constant power loads

Abstract

The connection of constant power loads (CPL) in a low power dc system leads to a reduction in the stability margin of the system. Most of the existing techniques increase the stability margin by modifying the controller for CPL or source converter at the cost of deterioration in the performance of converters. Few publications have suggested methods to determine the value of dc‐link capacitance required for stable operation of dc microgrid with CPL. These methods do not necessarily give the minimum possible capacitance as a solution. This paper suggests a method to determine the lower bound on the value of capacitor, for stable operation of dc system. A dc system with both linear and CPL loads is considered. Detailed mathematical analysis is used to determine the range of capacitance to ensure the stability of equilibrium point. Further, this paper discusses the effects of variation in linear loads on the selection of capacitor. The procedure of capacitor selection for a low power dc system is included. Using the real‐time digital simulator and a digital signal processor, controller hardware‐in‐loop based validation is carried out for the proposed approach.