Jiaqiang Yang, Xiang Zhang, Minghui Zhang, and Dan Peng
Flywheel energy storage system, discharge control strategy, loadcurrent compensation, power balance, decoupling algorithm
This paper is focused on the discharge control strategy of high-speed flywheel energy storage system (FESS). Field oriented synchronous frame equivalent model of the high-speed FESS in both charge and discharge mode is derived, and conventional discharge control strategy with double closed-loop PI controller is analysed. Then a modified strategy based on the power balance between the converter AC and DC side is put forward, which utilizes the load current to compensate the output value of outer voltage loop regulator and recalculate the reference value of inner current loop regulator with DC bus voltage, motor speed and flux considered. A decoupling algorithm is also added to the inner current loop for eliminating the influence of cross-coupled voltage at high speed. The strategy can effectively improve the current tracking ability, accelerate the dynamic response of DC bus voltage recovery and eliminate DC bus voltage fluctuation in the sudden change of load current. Simulation results with MATLAB verify the effectiveness and improvement of the proposed method.
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