Resistance-Emulating Control Strategy for Three-phase Voltage Source Rectifiers under Unbalanced Grids

In this paper, a resistance-emulating control strategy without grid voltage sensors is proposed for three-phase voltage source rectifiers under unbalanced grid conditions. It consists of angle estimator, coordinate correction, resistance-emulating, common-mode resistance (CMR) and the differential-mode resistance (DMR) regulation, extended state observer and other critical steps. In this scheme, the CMR regulates the average power, and the DMR controls the ripple power caused by the unbalanced supplies. Three different control objectives including constant active power, symmetrical input currents and constant reactive power are achieved by regulating the DMR. Since the grid voltage sensors and the information of the grid side circuit parameters are not required, the cost is reduced and the robustness and reliability of the scheme is improved. Experiments verify the effectiveness of the proposed method.