Abstract
The multi-channel (MC) back-to-back voltage source inverter (VSI)-fed doubly fed induction machine (DFIM) is emerging as a highly interesting topic in large-rated variable speed pumped-storage power plants (PSPP) in view of cost, optimal efficiency, and space requirements. Although the VSI is the fundamental part of the drive controlling the active/reactive power of the plant, redundancy is presently not adopted in practice causing the unit as a whole to shut down upon a failure in the converter and control circuit. This paper evaluates a large-rated (250 MW) DFIM-fed variable-speed unit of a PSPP in terms of its reliability and availability. A Markov model is developed to assess the reliability of the drive based on a number of factors including survivability and annual failure rate (FIT). Further, the Markov model is applied to different PSPPs for comparison of reliability among them.
Highlights
Several energy storage technologies have been developed including compressed air, pumped-storage power plant (PSPP), flywheels, high energy batteries, super capacitors, biofuels, and thermal energy storage
Variable speed PSPP is an emerging technology used in pumped-storage systems where it offers several benefits, (i) increased efficiency in generation/pumping mode irrespective of water level in the dam, (ii) mode transition from pumping to generation and vice versa in short time, (iii) high dynamic stability against grid and speed fluctuations, (iv) high ramp rate compared to fixed-speed PSPP, (v) quick response in load balancing, and (vi) flywheel effect [5], etc
Reliability of a 250-MW doubly fed induction machine (DFIM) unit is estimated with the following assumptions: (i) all the components/equipment are operational during their scheduled period, (ii) input power supply has been fully reliable
Summary
Several energy storage technologies have been developed including compressed air, pumped-storage power plant (PSPP), flywheels, high energy batteries, super capacitors, biofuels, and thermal energy storage. Faults are more likely in power converters of variable speed drives causing frequent plant shutdowns and huge generation losses [13]; redundancy in power converters and control circuits, especially in pumped-hydro applications of large rating (>100 MW), is expected to be imposed as a statutory requirement by the regulatory body, e.g., Central Electricity Authority (CEA) of India (2007) [14]. This creates uncertainties in decision-making for the policy makers and project authorities of the variable speed PSPP in view of reliability and availability of the unit.
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