Improved Droop Control Strategy Involved in Power Grid Frequency Regulation for VSC-MTDC Transmission Systems
The traditional droop control strategy involved in power grid frequency regulation can take advantage of frequency devia-tion and DC voltage to achieve mutual support between the frequencies of voltage source converter based multi-terminal flexible direct current transmission systems(VSC-MTDC).However,the droop coefficient of traditional DC voltage is fixed.The operation status of power grid and converter station capacity are neglected when allocating the unbalanced power which results in the converter station overload and weak grid frequency fluctuate greatly when bearing power.To solve this problem,an improved droop control strategy participating in power grid frequency regulation is proposed.Firstly,the power energy allocation relationship of the traditional droop control strategy involved in power grid frequency regulation is analyzed.Secondly,the voltage droop coefficient is redesigned considering the frequency margin of the power grid and the capacity of the converter station itself.The control strategy proposed can ensure the converter station not overloaded and the stable operation of weak power grid when the system is disturbed.Finally,simulation verification is conducted through MATLAB/SIMULINK,the results show that the proposed strategy can improve the frequency adjustment capability of multi-terminal flexible DC transmission systems,and operating ability of system is effectiely improved.
traditional droop controlVSC-MTDCfrequency marginpower marginweak power grid
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