Research on control strategies of soft start and grid connection for high power synchronous compensator fed by low-voltage LCI

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This paper describes the soft start and grid connection control strategies for high power synchronous compensator fed by low-voltage load-commutated inverters (LCI). In the start-up stage, field weakening method is used to make the motor start stably, and the back electromotive force (EMF) basically remain stable within the LCI withstand voltage at the same time. When the motor speed up to above the rated speed, a free-deceleration connection strategy is adopted to connect grid. The motor back EMF amplitude is changed through the adjustment of excitation current. When the motor is decelerated to the rated speed, the conditions for grid connection are judged. If the grid connection fails in this cycle, the motor will re-access the LCI and repeat the same steps until meets the requirements. The feasibility of the proposed strategy is validated by simulation.