发电机叠加型低励限制对电力系统动态稳定影响机制

当前发电机励磁调节器广泛配置有叠加型低励限制功能,该功能对电力系统动态稳定性有着重要影响,但其影响机制并未获得充分认识。文中基于扩展Heffron-Phillips模型,分析了模型新增回路系数随低励限制参数和机组工况的变化规律;采用电磁转矩分析法,将机组的阻尼转矩分解为低励限制提供的阻尼转矩、电力系统稳定器(PSS)提供的阻尼转矩、系统固有阻尼转矩和D系数阻尼转矩;推导分析了低励限制参数和工况变化对各部分阻尼转矩的影响机制。研究结果表明,通常较大的低励限制边界线斜率会导致低励限制提供的阻尼转矩分量变为负值,并且恶化PSS提供正向阻尼转矩的作用。通过典型系统的算例仿真进一步验证了所得结论的正确性。

Influence Mechanism of Superimposed Type of Underexcitation Limiter in Generators on Power System Dynamic Stability

The excitation regulator of generators in current power systems are widely equipped with superimposed type of underexcitation limiters(UELs), which have important impacts on the dynamic stability of power systems. But the mechanism has not been fully recognized. Based on an extended Heffron-Phillips model, the variation law of the new coefficient of the model with the change of UEL parameters and operation point is analyzed. The damping torque of generator is divided into four components by using the electromagnetic torque analysis method. They are damping torque provided by UEL, damping torque provided by power system stabilizer(PSS), the inherent damping torque of system and damping torque related to coefficient D. The impacts of UEL parameters on the various parts of the damping torques are deduced and analyzed in detail. The results indicate that UEL boundary line with a large slope may cause damping torque provided by UEL to become negative, and UEL will worsen the positive damping torque provided by PSS in the usual case of UEL parameters. A typical example of the simulation system further validates the conclusions proposed.This work is supported by State Grid Corporation of China(No. XT71-15-059).