Dynamic Behavior Analysis and Vector Controller Design for a Variable Speed Pumped Storage Power Plant in Generator and Motor Operating Mode

In variable speed pumped storage hydropower plant (VS-PSHP), unlike fixed speed power plants where synchronous machines are used, they are powered by a doubly fed induction motor-generator (DFIM) coupled with a back-to-back converter. In this paper, first, the mathematical model of different components of VS-PSHP is presented. The control sections, the machine side converter (MSC) and the grid side converter (GSC), each contain two control paths for the dq axes, and each path containing an external loop and an internal loop. Therefore, the inner and outer loops is extracted and transfer functions are presented. To adjust the control coefficients, the open-loop and closed-loop transfer function of different control sections, MSC, GSC, and pump-turbine, are extracted and its stability is guaranteed by drawing the Lucas root diagram and tuning of the zero position and system poles. Finally, in order to validate the design, a VS-PSHP is simulated in Matlab/Simulink/SimPowerSystem environment and its results are presented to test the load change in two modes of generator motor operation. The simulation results verify the operation of the designed control system.