Research on Grid-Connected Optimal Modulation Algorithm for Seawater Variable-speed Pumped Storage Unit

With the rapid development of new energy such as wind and solar energy, its connection to the grid brings many problems to the safe and stable operation of the power system. So it has great significance to develop seawater variable-speed pumped storage unit for regulation and energy storage. In order to meet the grid harmonic requirement, the common solution is to add the grid side filter for the high-power NPC (neutral point clamping) topology grid-connected converter. But the filter will increase the volume, weight and cost of the equipment, and reduce the system reliability. Therefore, to ensure that the grid current meets the requirement of the standard IEEE 519, this paper adopts a grid-connected optimal modulation algorithm without adding the filter. And the effectiveness of the algorithm is verified by simulation and experiment.