电网电压不平衡下双馈型风电场可控运行区域及其控制策略

电网电压不平衡条件下,双馈感应发电机(DFIG)风电机组实现电磁转矩无脉动等不同传统控制目标时所需要的负序电流幅值不同。结合电网电压不平衡条件下电网侧变换器(GSC)与转子侧变换器(RSC)实现各传统控制目标时所需的负序电流幅值,通过详细分析等值DFIG风电场GSC与RSC的输出负序电流能力,得到基于不同电网电压不平衡度和系统有功出力的DFIG风电场可控运行区域。以该可控运行区域为基础,提出电网电压不平衡条件下DFIG风电场的多目标协调控制策略,即根据电网电压不平衡度及系统有功出力选择或切换系统最优控制目标,进而改善不平衡电压下DFIG风电场的运行能力及所并电网的电能质量。仿真与实验结果验证了所提方案的可行性。

Control Strategy of Doubly-Fed Type Based Wind Farm and Its Controllable Operation Area under Unbalanced Grid Voltage Condition

Under unbalanced grid voltage conditions, doubly-fed induction generator (DFIG) based wind power generation system requires different amplitude negative-sequence current to achieve different control targets, such as zero pulsation of the electromagnetic torque. Combined with the required negative-sequence current of traditional control objectives during network unbalance, this paper analyzed the output capabilities of the negative-sequence current by the grid-side converter (GSC) of DFIG and rotor-side converter (RSC). Then the controllable operation area of DFIG-based wind farm was achieved, based on the degree of grid voltage unbalance and the active power output. Thereafter, this paper proposed a multi-objective coordinated control strategy of DFIG-based wind farm under unbalanced grid voltage conditions. That is, the optimal control target could be selected according to the degree of grid voltage unbalance and active power output, which further improves the operation performance of DFIG wind farm and the grid-tied power quality. The simulation and experimental results verify the proposed scheme.