Linear Quadratic Optimal Control of MMCSTATCOM with Stationary Frame under Asymmetric Fault in AC Power Grid

Static synchronous compensator based on modular multilevel converter (MMC-STATCOM) can achieve dynamic reactive power output and voltage support when an AC grid fault occurs. Aiming at the problem that the control algorithm is too cumbersome due to the positive and negative sequence AC components when asymmetrical faults occur in the grid, an MMC-STATCOM AC fault ride-through algorithm based on the stationary frame is proposed in this paper. Firstly, a phase-locked loop is used to obtain the phase of the positive sequence component of the grid voltage. Then, the dynamic reactive current reference value is transferred into the two-phase stationary frame. In order to address the problems of the PI regulator not being able to achieve the sinusoidal component tracking with a zero error, the quasi proportional-integral-resonant control algorithm based on the linear quadratic optimal control state feedback is proposed to achieve the fast tunning of multiple control parameters. Finally, the correctness and effectiveness of the control strategy proposed in this paper are verified under a simulation test system.