Decentralized Unified Control Strategy for Medium and Low Voltage DC Distribution Power System

Abstract

Distributed photovoltaic (PV) accessed to DC distribution power system (DPS) from multi-port is a major form to promote the consumption of renewable energy, but the increase of PV permeability will lead to the deterioration of the system stability. Traditional analysis usually concentrates on the DC micro-grid and the analysis of DC DPS with multi-voltage levels, such as medium and low voltage DC DPS, is rarely involved. This paper proposes a decentralized unified control strategy for the medium and low voltage DC DPS. It is composed of two parts, one is the decentralized control strategy based on the DC bus voltage signal (DBS) for the PV, storage and fuel cell units on the DC bus; one is the unified control strategy for the DC transformer integrating the power control, medium voltage and low voltage DC bus voltage regulation functions. Consequently, it avoids the control mode switching of DC transformer and can achieve the global power sharing of the system. Finally, the equivalent simulation model of medium and low voltage DC DPS is built in Matlab/Simulink and simulation analysis of multiple operating states and scenarios is carried out to validate the effectiveness of the proposed control strategy.