Dynamic Performance of Pumping Mode of 250 MW Variable Speed Hydro-Generating Unit Subjected to Power and Control Circuit Faults

Abstract

Doubly fed induction machine (DFIM) is increasingly being preferred in sites where there is large variation in water head (e.g., Tehri hydropower complex in India having water head variation from 130 to 230 m), as it offers high dynamic stability and better energy efficiency at part loads. Smooth starting, unity power factor, and better rotor current profile are the reasons; back-to-back voltage source converters are used in rotor side of the machine. Speed and power factor of DFIM are controlled through power converters in accordance with surplus power available in grid and water head of dam. This paper presents dynamic behavior of a 250 MW DFIM hydro-generating unit, to be commissioned in 1000 MW Tehri pumped storage plant, operating in pumping mode. Further, the performance of pumping operation of DFIM is assessed under power converter and control circuit failures. Persevere ability of the machine is analyzed based on performance measures: Speed, current, reactive power consumption. From the analysis, energy storage loss of about 66.61 MU/year is estimated in a 1000 MW plant due to the inadequate power and control redundancy. A 2.2 kW DFIM is experimented at laboratory level to support the simulation.