【摘要】 我国一些地区电网与主网间联系薄弱,发生解列故障的风险较大。针对安装有较大容量水电机组的外送型地区电网,进行了解列故障时的水电机组孤网暂态频率特性和控制策略研究。分析了水电机组的过速保护和过电压保护的配置情况,以大型水电机组外送功率典型系统为例,研究了解列故障时水电机组的调控特性,结果表明采用常规一次调频下限幅时水电机组转速飞升较为严重,而放开一次调频下限幅措施下存在较为严重的超调现象,有可能引发低频减载动作。文中提出一种应对解列故障的水电机组调频控制改进方案,通过测量解列前地区电网外送功率值,对原有调速控制系统进行改进,包括更新控制目标值和加入呈衰减特性的前馈信号,实现对频率飞升的控制和超调现象的抑制,仿真结果验证了改进方案的有效性。文中工作可为充分掌握水电机组调频特性,制定有效措施提高地区电网抵御解列故障的能力提供参考。更多还原

【Abstract】 There exists high risk of separation fault for some regional power networks in China due to the weak connection with main power network. According to the separation fault of regional sending network installed large capacity hy dropower unit, the dy namic frequency characteristics and control strategy of hydropower unit are studied. The configurations of overspeed protection and overvoltage protection of hydropower unit are investigated, and the primary frequency regulation characteristics are researched based on a typical testing example. When the regional sending network installed a large capacity hydropower unit is isolated from main power network, the speed of hydropower unit will increase seriously with normal limiting amplitude of primary frequency regulation. To improve the frequency control effect, the method of expanding the limiting amplitude is testified, and the result shows that the under frequency load shedding devices may be triggered by overshoot problem. This paper presents a new method for the improvement of frequency control of hydropower unit for separation fault. The key technology is to modify the speed regulating system from two aspects by introducing the signal of transfer power from the regional network to main network. The power target of the speed regulating control is switched to appropriate value, and a feed-forward signal with attenuation characteristic is superimposed to the valve command signal when the separation fault happens, thus to realize the frequency control and overshoot suppression. The effect of the new method is confirmed by simulation and suggestions of taking effective measures to improve the regional power network’s ability to resist separation failure are provided.更多还原