A Damping Control for DC Distribution System Under Isolated Operation Mode

Abstract

There are risks of resonant instability exiting in the DC distribution system configured with battery energy storage devices because of capacitors and inductors in the network with fast speed-controlled DC-DC converters. The DC distribution system needs battery energy storage devices to provide DC voltage support when it operates in an isolated island mode because of no AC or DC sources at that moment. To explore the key factors affecting the resonant instability of DC network, a three-terminal DC network consisting of DC voltage control, constant current control, and constant power load is used for state space modeling. Research results show that the inductors for faults current limitation interacting with the capacitors under high constant power load is the main reason causing instability. The other reason is the large parameter of the current controller. To suppress the resonant instability of the DC distribution system, a damping control strategy by filtering DC voltage in advance to the current control loop is proposed, and the parameters are selected using the roots locus method. Simulations verify the correctness and effectiveness of the proposed method.