三相全控整流桥的准动态模型

QUASI-DYNAMIC MODEL OF FULLY CONTROLLED THYRISTOR RECTIFIER OF THREE-PHASE

随着大型同步发电机自并激励磁系统的推广应用 ,三相全控整流桥做为励磁系统的重要部件 ,其模型误差对电力系统稳定性数字仿真结果有重要影响。三相全控整流桥的传统平均值模型不能反映控制角变化时整流桥的非线性动态电压输出 ,特别是在电力系统故障 ,输出电压频繁大幅度调整时 ,模型误差将被显著放大。该文在计算耗时支出较小的前提下 ,提出基于仿真步长的电压源 变压器 三相全控整流桥的动态模型 ,即 :先对三相全控整流桥触发脉冲形成环节进行模拟 ,求出触发时刻 ,再对应计算出整流桥输出在一个机 电互动仿真步长上的平均值 ,使其反映整流器开放角、换弧过程和电源电压对整流器输出电压的动态影响 ,从而消除了模型在这个应用范围内的模型误差。该模型可在一个数字仿真步长上反映整流器开放角由大到小变化时的输出电压纹波以及换弧过程对整流器输出电压的动态影响。该模型耗时少 ,可以用于电力系统稳定性分析和励磁系统控制方式的研究 ,以及电力系统稳定器PSS的设计和整定计算验证。

The static excitation system for large size synchronous generator has put in to application widely nowadays. The model error of controlled 3 phase thyristor rectifier, which is a main part of the excitation system, has obvious effect on the result of digital simulation for power system stability study. The conventional average model of controlled 3 phase thyristor rectifier cannot reflect the truth of its dynamic non linear voltage output. Especially when there is an emergency in power system, the excitation system generally regulates its output voltage in an extended range and the model error will be enlarged significantly. Within the paper, after balancing the requirements of precision and computing cost, an improved model is given as voltage source transformer thyristor rectifier model based on simulation step length. The modeling is, firstly to simulate the firing pulse generation part of the rectifier bridge for firing moment, secondly to calculate the average value of bridge output voltage during a simulation step length which is suitable for simulating mechanical and electrical transients.Cause average value worked out is affected by the firing angle,commutation and AC input voltage,the modeling can eliminate the conventional model error in simulation for power system stability study.This new model can give out the triple of output voltage during the variation of the firing angle from a large value to a smaller one and the commutation influences on the bridge output in each simulation step\|length.Consuming less computing time, the model is considered to be suitable for analysis on power system stability, studies on the control principle of excitation system and the design of power system stabilizer.