“风火打捆”交直流外送系统的暂态稳定控制研究

"风火打捆"交直流外送是未来千万千瓦级风电能源基地电力外送的重要方式之一,亟需掌握"风火打捆"交直流外送系统的稳定特性及其机理。功角是反映系统暂态稳定性的主要标志,分析了双馈电机的功角快变特性和"风火打捆"系统等值机械转动惯量对火电机组功角暂态稳定性的影响。针对系统的暂态稳定性问题,提出了一种附加控制策略,并设计出控制装置样机,可提高"风火打捆"系统的暂态稳定性。基于所提附加控制策略的试验样机通过了实时数字仿真器(Real Time Digital Simulator,RTDS)的闭环验证,结果表明:该附加控制策略通过改变直流输送功率和调节风机的有功输出,消除或减小了系统在暂态过程中的瞬时不平衡功率,增强了直流系统和风机对火电机组的等效阻尼作用,有效抑制了火电机组的功角摇摆幅度,提高了"风火打捆"系统的暂态稳定性。

Study on transient stability control for wind-thermal-bundled power transmitted by AC/DC system

For the 10 GW wind power bases in China, wind-thermal-bundled power transmitted by AC/DC system is regarded as one of feasible ways, but the stability characteristic of this kind of transmission system should be investigated. Angle is the special symbol to reflect the system transient stability, in the paper, the influence of angle rapidly changing behavior of DFIG and equivalent mechanical rotational inertias of wind-thermal-bundled system on synchronous generators angle transient stability characteristic are studied. To solve the problems of transient stability, an additional control strategy is proposed and is designed to become a control device prototype. Using real-time digital simulator (RTDS), the control device prototype is validated, simulation results show that the proposed additional control strategy can enhance the equivalent damping effect of DC system and DFIG to synchronous generators by changing the DC transmission power and adjusting the active power output of DFIG which can eliminate or reduce the imbalance of instant power in the transient process, as a result, the amplitude of angle fluctuation can be effectively inhibited, and the transient stability characteristic of wind-thermal-bundled power transmitted by AC/DC system is improved.