Equivalent Inertia and Dynamic Performance of Different VSC Control Strategies

In order to adapt to the weak grid in HVDC, three kinds of control are proposed: frequency support loop in the phase-locked loop, droop control with the low pass filter and inertial synchronous control. The frequency support abilities of these three controls are related to their equivalent inertia, which depend on control structure. In order to achieve better performance of DC transmission system, the influence of the three controls is compared with the same equivalent inertia in the paper. Firstly, the equivalent inertia of three controls is discussed. Then, the small-signal models are established to reveal the mechanisms of their dynamic responses. Finally, the performance is compared under various grid faults. The theoretical analysis is verified with the circuit simulation results.