基于轨迹灵敏度的DFIG直流过电压优化

DC Overvoltage Optimization of DFIG Based on Trajectory Sensitivity

电网故障后电压下降,可能导致双馈感应发电机DFIG(doubly-fed induction generator)直流过电压,可确定有效控制参数以降低直流电压。首先,提出DFIG直流电压轨迹灵敏度的解析表达;然后,定义峰值相对轨迹灵敏度指标,确定对直流电压影响较大的参数;最后,提出直流电压优化模型,以直流电压峰值与直流电容为目标,以轨迹灵敏度为一阶梯度信息,并通过BFGS算法近似构造海森矩阵,采用内点法对选取参数迭代求解。仿真结果表明,同时优化直流电容和变流器参数,可以在限制直流电压前提下减小电容取值,且故障切除后直流电压恢复速度加快。

Considering that the voltage drop after grid fault may yield DC overvoltage of a doubly-fed induction generator(DFIG),the DC voltage can be reduced by the determination of effective control parameters. First,the analytical expression of the DC voltage trajectory sensitivity of DFIG is given. Then,the peak index of relative trajectory sensitivity is defined to determine the contributing parameters of DC voltage. Finally,an optimization model of DC voltage is proposed,which takes the peak DC voltage and DC capacitance as its objective. In addition,based on the trajectory sensitivity which is taken as the first-order gradient information,the Hessian matrix is approximately constructed using the BFGS algorithm,and the selected parameters are iteratively solved using the interior point method. Simulation results show that the optimization of both the DC capacitance and the converters’ parameters can reduce the DC capacitance under the premise of limiting DC voltage,and the recovery speed of DC voltage after fault clearance is faster.