An MMC-based full-power variable-speed pumped storage system

Abstract

The invention provides an MMC-based full-power variable-speed pumped storage system in the field of power distribution. The system comprises a generator stator, a full-power converter, a transformer and a power grid, which are connected successively in series via an alternating current cable. The full-power converter comprises a grid side converter and a generator side converter, which are connected in series via an alternating current capacitor and employ an MMC topology structure. For a full-power variable-speed pumped storage power station, the generator side converter can change rotating speed to increase the operating efficiency and the adjusting range of a pump turbine and the grid side converter can realize active power and reactive power rapid control, so that the pumped storage power station can maintain power grid voltage and frequency stability under the circumstances of load fluctuation and various kinds of power supply change. With the MMC topology structure, grid connection of full-power variable-speed pumped storage units can be realized and the content of harmonic generated by power electronic devices can be effectively reduced while improving the quality of electric energy of power grids; the trigger frequency of a single part is low, so that the service life of each part can be prolonged.

Description

[0001] Patent field [0002] The invention relates to the field of power distribution technology, in particular to a full-power variable-speed pumped storage system based on MMC (Modular Multi-level Converter, MMC). Background technique [0003] With the increasing number of stable power sources such as nuclear power and supercritical large-capacity power plants in the power grid, and the large-scale utilization of intermittent renewable energy such as wind power and photovoltaic power generation, the proportion of the power grid is increasing day by day, making the stable operation of the power grid more stable. for difficulty. The stable operation of the power system refers to maintaining the frequency and voltage stability of the system within a certain range, and the power throughput through the energy storage system is an important way to maintain the stable operation of the system. [0004] At present, the only energy storage technologies used in power systems in my cou...

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Problems solved by technology

[0005] However, in practice, the fixed-speed pumped-storage unit can only adjust the input power through the opening of the guide vane under the pumping condition, the adjustment range is small, and the response speed is slow, which cannot meet the requirements of fast and accurate frequency adjustment of the power grid; on the other hand, When the unit is in power generation condition, due to the simultaneous change of the water level of the upper and lower dams, the water head changes greatly, and for different water heads, the speed corresponding to the best power generation efficiency is different, so the variable speed power generation of the pumped storage unit is required to achieve the best power generation efficiency

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