自激异步发电机变速恒压运行时电容值的计算

Capacitance Requirement for Constant Voltage Operation of Induction Self-excited Generator under Variable Speeds

为保证自励异步发电机在转速和负载改变时能稳态恒压运行,采用改变机端电容值的措施,并给出了机端电容值的计算方法。以异步发电机带阻感负载稳态运行时的等值电路为基础,推导了回路阻抗方程,依据异步发电机稳态运行时同路阻抗为零这一必要条件,选择同路阻抗绝对值为目标函数,把端电压作为优化约束条件,利用单纯形法计算了不同转速和负载下的机端电容值,克服了传统方法不能处理有约束问题的弱点,计算值与实验值的一致证明了方法的有效性。此法亦可用来计算并联补偿电容值。论文还给出了恒定负载时机端电容值与转速的关系曲线,说明异步发电机恒压运行时存在临界转速。

To keep the self-excited induction generator operating steadily at constant voltage under variable speeds and different loads, the paper presents an approach of computing the terminal capacitance. Based on the steady state equivalent circuit of an induction generator, the loop impedance is calculated, from which the terminal capacitance is determined by a direct optimizaed method with constant terminal voltage as the constrained condition. The simplex method is employed to obtain the terminal capacitance, which is advantageous over the traditional methods in dealing with constrained problems. That good agreement between the calculated results and the experimental ones from a 2.2kW laboratory machine confirms the validity and accuracy of the method. This paper also gives the variation of the terminal capacitance with the speed for the specified load impedance, showing that there is a critical speed below which the constant terminal voltage can＇t be created.