Influence and comparison of P/Q-control based VSC-HVDC system on the grid power oscillation damping

Abstract

To analyze the dynamic process of VSC-HVDC system actively participating in suppressing the grid power oscillation, under the electromechanical time control scale, this paper establishes the linear mathematical model of the VSC-HVDC connected to the single machine infinity system, and the dynamic interaction relationship between the controlled active and reactive power injected into the power grid by VSC-HVDC, moreover, the synchronization, inertia and damping level are investigated by the electrical torque method in this paper. The study shown that when the rotor speed is selected as the grid state quantity feedback signal, adjusting the PID controller gain of rotor speed control loop can effectively adjust the VSC device’s active and reactive output power to improve the system damping level, synchronous characteristics and inertial effects, which can thus restrain the rotor speed deviation and speed change rate under oscillating conditions and improve the system frequency stability. In addition, this paper proposes an index for the proportion of inverter station regulation capacity, which proves that the VSC-HVDC operating in active power control strategy has better suppression effect on power oscillation than reactive power control, reducing the design capacity and cost of inverter stations. Finally, the simulation proves the dynamic process analysis correctness of VSC-HVDC suppressing the grid power oscillation in this paper.

Keywords

• VSC-HVDC
• Power oscillation
• Dynamic process
• Damping level