基于可释放动能的双馈风机虚拟惯性控制策略影响分析

针对现有双馈风力发电机（doubly-fed induction generator，DFIG）附加虚拟惯性控制策略后存在兼顾频率稳定及暂态功角稳定方面的不足，首先利用DFIG的电压和磁链方程，推导出电磁功率表达式，基于同步发电机功角概念推导出与其类似的DFIG等效功角，并分析了DFIG的调频能力与其等效功角稳定性的关系。其次，鉴于DFIG在不同风速下含有不同程度的可释放动能（kinetic energy，KE），提出了一种基于可释放动能的惯性控制策略:根据转子转速调整DFIG惯性控制策略中频率变化率和下垂回路的回路增益，使运行在较高转速下的DFIG释放更多的动能，根据释放的动能来决定风电机组对系统惯性响应可提供的贡献。该策略在提高系统调频能力的基础上能兼顾改善暂态功角稳定性，并避免了转子转速过低，从而保证了DFIG在惯性控制过程中的稳定运行。最后，基于实时数字仿真系统（real time digital simulation system，RTDS）的仿真软件RSCAD搭建了DFIG单机并网仿真系统，仿真结果验证了所提控制策略的有效性。

Influence Analysis of DFIG Virtual Inertial Control Strategy Based on Releasable Kinetic Energy

In allusion to the defect caused by adding virtual inertia control strategy onto existing doubly-fed induction generator (abbr. DFIG) that leads to the deficiency in giving consideration to both frequency response and transient angle stability, firstly, utilizing voltage and flux linkage equations of DFIG the electromagnetic power expression was derived, and based on the conception of power angle of synchronous generator the equivalent power angle of DFIG, which was similar to the former, was derived too and the relation between the frequency regulation ability of DFIG and its equivalent power anger stability was analyzed. Secondly, in view of the fact that under different wind speeds, DFIG contained various degrees of releasable kinetic energy, a releasable kinetic energy based inertia control strategy based on was proposed, i.e., the rate of change of frequency (abbr. ROCOF) and the loop gain of the droop loop in the inertia control strategy were adjusted according to the rotor speed to make the DFIG, which was operated under a higher rotating speed, enable to release more kinetic energy, and then based on the released kinetic energy the available contribution of wind power generating set to system inertia response could be determined. On the basis of improving system frequency regulation ability, the proposed strategy could give consideration to improve transient power angle stability, and avoid too low rotor speed, thus the stable operation of DFIG during inertia control process could be ensured. Finally, utilizing simulation software RSCAD based on real time digital simulation system (abbr. RTDS), a single machine grid-connected simulation system for DFIG was constructed, and the simulation results show the effectiveness of the proposed control strategy.