DFIG与VSC-HVDC协同参与电网调频的动态潮流算法

Dynamic Power Flow Algorithm With Coordinated Regulation of Power System Frequency With DFIG and VSC-HVDC

针对双馈感应发电机(doubly-fed induction generator,DFIG)经电压源变流器–高压直流(voltagesourceconverterhigh voltage direct current,VSC-HVDC)并网,基于"主网频率-直流电压-风电场"串级下垂控制调频策略,建立DFIG经VSC-HVDC参与系统一次调频的动态潮流模型,用于量化DFIG备用与直流电容虚拟惯量协同控制下电网频率响应。计及DFIG有功备用,在直流电压限制范围内,提出直流电容虚拟惯性时间常数的取值上限。考虑调频过程中DFIG转速变化,提出基于转子动能的DFIG惯性时间常数动态修正算法,提高动态潮流结果精度。算例验证了所提算法分析DFIG与VSC-HVDC协同电网调频能力的可行性,证实计及DFIG参与调频的直流电容虚拟惯性时间常数最大取值可提升交流系统惯性水平;DFIG等效惯性时间常数修正算法符合其动态调频特性。

For the doubly-fed induction generator(DFIG) grid-integrated through voltage source converter-HVDC(VSC-HVDC), based on cascaded droop control(grid frequency-DC voltage-wind farm) for frequency regulation, a dynamic power flow model with DFIG participating in primary frequency regulation through VSC-HVDC is proposed to quantify frequency response of the power grid with coordinated control of the active power reserve of DFIG and the virtual inertia of DC capacitor. Considering the active power reserve of DFIG, within the range of DC voltage constraint, an upper limit of the virtual inertia constant of DC capacitor is proposed. Considering the rotor speed variation of DFIG during frequency regulation, an algorithm of dynamic correction to the inertia time constant of DFIG based on the stored kinetic energy of rotor is proposed to improve accuracy of dynamic power flow result. Numerical analysis verifies feasibility of analyzing the coordinated frequency regulation capability of DFIG and VSC-HVDC with the proposed algorithm. It is verified that the inertia level of the AC system is improved by applying the maximum equivalent inertia constant of the virtual inertia control with DC capacitor, taking the frequency regulation of DFIG into consideration. The correction to the equivalent inertia time constant of DFIG is consistent with its dynamic frequency regulation characteristics.