Coordinated control of distributed renewable energy in bipolar DC microgrid based on modulus transformation

The coupling between the positive and negative poles of the bipolar DC microgrid will influence the voltage control which makes it difficult to compute the parameters of the control loop independently. The unbalanced voltage in the bipolar DC microgrid is a special power quality problem. The suppression of unbalanced voltage is a significant work in operation planning. In this paper, the expressions of voltage unbalance coefficient and distribution line current is deduced to investigate the influence of unbalanced loads on voltage deviation, voltage unbalance coefficient, and current distribution accuracy. On this basis, the common-mode and differential-mode consensus control of the bipolar DC microgrid is proposed to improve the dynamic performance of the control system and reduce the voltage deviation and voltage unbalance coefficient. In addition, the small-signal stability is analyzed in this paper. To verify the effectiveness of the proposed modulus control method in the bipolar DC microgrid, a MATLAB/Simulink simulation platform, and a low-voltage experimental platform are established. The proposed modulus control is better than the droop control in regulating unbalanced voltage. In addition, it is still effective under the influence of load change. Moreover, the unbalanced voltage can be controlled when addition PV and BEMS are added in the bipolar DC microgrid.