Power decoupling control design of the VSC-HVDC under the weak receiving AC grid conditions

The power coupling effect of the voltage source converter-based high voltage direct current (VSC-HVDC) system using the vector control is obvious under the weak receiving AC grid conditions. In view of this issue，the reason for the power coupling caused by the weak receiving AC grid is revealed， and a corresponding improved decoupling control strategy is proposed. Firstly，the linearized relationships between the output power and dq-axis currents of VSC were derived. Then，the coupling relationships between output active power and q-axis current, output reactive power and d-axis current were analyzed. The power coupling mechanism was revealed based on the coupling relationships. Meanwhile, based on the idea of feedforward compensation，the vector control strategy was improved to achieve more effective power decoupling. The theoretical analysis and time-domain simulation results show that the strong power coupling under the weak receiving AC grid results from the strong coupling of active power and q-axis current, and reactive power and d-axis current, respectively. Besides, the proposed improved vector control can improve the decoupling performance，fault response characteristics and stability of the system. © 2022 Editorial Department of Electric Machines and Control. All rights reserved.