Coordination Control Between Excitation and Hydraulic System During Mode Conversion of Variable Speed Pumped Storage Unit

Variable speed pumped storage (VSPS) unit has various operation modes and it is often required by the dispatcher to convert rapidly and frequently between these modes. Unlike conventional units, however, VSPS is controlled by both excitation and hydraulic system, and control of them is independent of each other. The mismatch between the rapid electromagnetic response of the former and the relatively slow mechanical response of the latter could result in unfavorable transients or even conversion failure. Hence, coordination controls between excitation and hydraulic system during mode conversion is a meaningful topic but has seldom been investigated. To this end, the electromechanical transient model of VSPS considering the excitation dynamics of the converter is first established. Then, a multistage soft coordination control strategy is proposed in this article. By applying this strategy, the soft and smooth mode conversion of VSPS is achieved with favorable dynamic performances during the complete conversion process. And finally, simulation and experimental results verified the effectiveness of the strategy.