Wideband Harmonic Voltage Feedforward Control Strategy of STATCOM for Mitigating Subsynchronous Resonance in Wind Farm Connected to Weak Grid and LCC HVDC

For the wind farm connected to line-commutated converter-based high-voltage direct-current (LCC HVDC) and weak grid at sending end, subsynchronous resonance (SSR) is prone to occur due to the impedance interactions among wind farm, weak grid, and LCC HVDC. First, the mechanism and characteristics of this SSR are analyzed based on the impedance method. With the increase of the output power for wind farm or the decrease of the transmission power for LCC HVDC, the wind farm tends to cause SSR. Moreover, with the decline of the grid stiffness at sending end, the studied system easily causes SSR. Then, a wideband harmonic voltage feedforward control strategy of static synchronous compensator (STATCOM) is proposed to suppress this SSR. For the proposed damping controller of SSR, a constant voltage amplitude-based harmonic extraction method is designed without using filter. The harmonic extraction error of the proposed strategy is a constant |V
_n
- V
_r
|, which is induced by the difference between the constant voltage amplitude V
_n
and actual voltage amplitude V
_r
. By the theoretical analysis and simulation, this constant error |V
_n
- V
_r
| can be automatically counteracted by the PI controller of STATCOM. Finally, experimental results verify the validity of the proposed strategy.