Improved Thermal Behaviour of Multi-MW Power Converter Fed Pumped Storage Power Plant During Symmetrical Grid Fault

Variable-speed Pumped Storage Power Plants (PSPPs) are gaining renewed interest from policymakers and hydropower developers due to their improved flexibility in managing real and reactive power under varying water head conditions. In these systems, Doubly-Fed Induction Machines (DFIMs) with multi-megawatt power electronic converters on the rotor side are commonly preferred for high power ratings (over 100 MW). During grid faults, the junction temperature on the power semiconductor devices increases rapidly which leads to the failure of multi-megawatt power electronic converter excitation system. This paper investigates thermal stress on the multi-megawatt power electronic converter system during symmetrical faults in variable-speed PSPPs operating in pumping mode. To mitigate this stress, a coordinated DC-link chopper with demagnetizing control for the Rotor-Side Converter (RSC) is proposed. This strategy effectively controls power semiconductor device temperature during grid faults, and it gives superior results compared to the traditional vector control strategy. Thermal study is performed for a 5-channel parallel connected power converter serving to 250 MW DFIM (to be commissioned in Tehri PSPP, India) operating in pumping mode, and the control strategy’s effectiveness is validated through a scaled-down laboratory prototype.