提高暂态稳定的励磁与FACTS协调策略设计

灵活交流输电系统(FACTS)元件及发电机励磁系统对远距离输电系统的暂态稳定性有很大的影响。该文针对单机远距离与电网互联系统，提出采用非线性最优变目标策略协调设计发电机励磁、可控串补（TCSC）和静止无功补偿器(SVC)，从而提高首摆稳定性及快速阻尼后续振荡。所提协调方案是基于TCSC在故障期间闭锁时，SVC作为TCSC的辅助控制手段，当故障清除后，立即投入TCSC，从而使TCSC、SVC与发电机励磁同时贡献于暂态稳定性。在整个过程中，采用非线性最优变目标控制策略来协调所有控制器，即在暂态稳定第一摆及后续动态过程中预先设定两个目标：其一是励磁与FACTS输出最大，从而保证系统最大的暂态稳定域；其二是当发电机滑差接近于零时，控制器以阻尼功率振荡为目标，以使系统迅速恢复至稳态。最后采用NETOMAC仿真软件在我国阳城—淮阴输电工程中进行了仿真，并与常规PID控制进行了比较。结果表明，所提策略是正确的，有效的。

COORDINATED DESIGN OF GENERATOR EXCITATION AND FACTS FOR TRANSIENT STABILITY ENHANCEMENT

The transient stability of a long transmission system can be significantly influenced by the action of excitation systems and FACTS controls installed. This paper presents a nonlinear coordinated control scheme for excitation systems and TCSC and SVC controls for improving the first swing stability and damping quickly the subsequent power oscillation of a transmission system, where a power plant is connected with a power grid through long transmission line. When TCSC is blocked during fault-on, SVC is then treated as the supplement of the TCSC; after clearance of fault, TCSC is inserted instantly. Thus TCSC, SVC and generator excitation system are all contributed to the enhancement of transient stability simultaneously. The proposed coordination scheme is developed upon nonlinear optimal-variable-aim strategy(OVAS). With two pre-selected aims to be achieved during first swings following a fault and in subsequent dynamic ranges, the first is that the excitation system and FACTS installations are of the maximum outputs, to ensure its maximum transient stability region; then, as the slip of generator approaches zero, coordinated control aim is changed to damp the power oscillation and to drive the system to its steady state. The effectiveness of the proposed control scheme is demonstrated with the Yangcheng-Huaiyin transmission project of China, where the simulations are carried out by the NETOMAC program system. In comparison with a conventional PID design scheme, significant improvements in dynamic performance of the test system are achieved.