Enhanced Voltage Control of Bipolar DC Distribution System Based on Modulus Decomposition

Abstract

There is a coupling between the positive and negative poles of a bipolar dc distribution system, which makes the control of power converters influence mutually. It is difficult to calculate the control parameters of the positive and negative control loop independently. In this article, the modal conversion is introduced into PI control and voltage droop control of the bipolar dc distribution system. Then, the mathematical models of bipolar dc converter, dc lines, and dc loads in modal component space are deduced. Thus, the common-mode and differential-mode decoupling equivalent models are built for the bipolar dc distribution system. The coupling relationship between the common-mode and differential-mode equivalent circuit when the positive and negative loads are balanced and unbalanced is analyzed. The transfer functions from the common-mode and differential-mode duty ratios of the positive and negative power converters to the output voltage are deduced. Finally, the applications of modulus decomposition in the control of parameter design are analyzed based on PI control and voltage droop control. Moreover, a simulation model of the bipolar dc distribution system is built in MATLAB/Simulink and a low-voltage experimental platform is established to verify the validity and accuracy of the proposed algorithm.