A Low Voltage Ride Through Control Strategy for Large-Capacity Shore Variable Frequency Power Supply Based on Cascaded H-Bridge Topology

Shore variable frequency power supply system (SVFPSS)have been widely used in ports to solve the issue of air pollution when ships arrive at ports. However, there are few studies about low voltage ride through (LVRT) of SVFPSS. This article presents a LVRT control strategy when the SVFPSS is connected to the ship’s grid. The frequency converter adopts cascaded H-bridge (CHB) topology. The control method includes voltage and current double closed-loop control of positive and negative sequence separation based on a double second-order generalized integrator (DSOGI). And it also includes the low voltage detection method and switching of control mode in case of ship power grid fail. The frequency converter provides reactive power to support the recovery of the ship’s grid voltage. Through simulation, this paper simulates the three symmetrical drops and asymmetrical drops of the grid voltage. The experimental results have demonstrated the effectiveness of the proposed strategy.