Research on Synchronous Generator Control based on Nonlinear Digital Control Theory

提高发电机控制系统的性能对电力系统的稳定具有重要意义。在将最优控制理论应用于发电机控制时，控制器一般是针对某一工作点的线性化模型设计的。虽然这些控制器在设计工作点附近有效，但当工作条件发生较大变化时，它们可能不一定有效。本文研究了电力系统中同步发电机的非线性数字控制方法。该方法采用数字加速度控制的概念，考虑被控对象的非线性动力学特性。根据非线性控制规则，反馈增益随发电机状态变量的变化而变化。利用该控制规则，该方法与工作点无关。研究结果总结如下：1。基于数字加速度控制的概念，提出了同步发电机非线性数字控制公式和控制器设计算法。利用模型系统研究了控制器的性能，特别是模型简化、参数变化、工作点移动和限位器等因素对控制器性能的影响。由于建模上的假设，本文提出的方法对采样周期要特别注意。通过仿真得到了合适的采样周期。结果表明，该方法可用于发电机转速控制而非输出控制。该方法的性能与最优调节器的性能相同。通过对测量噪声对转速影响的研究，发现测量噪声对转速的影响最大。低通滤波器对其他测量噪声也有效。

Improving the performance of generator control system is very significant for power system stability. In the application of the optimal control theory to generator control, controllers are generally designed for a model linearized at a certain operating point. Although these controllers are effective near the designed operating point, they may not necessarily be effective when the operating conditions change considerably.In this research, a nonlinear digital control method of synchronous generators in a power system is investigated. This method considers nonlinear dynamics of the controlled object by applying the concept of digital acceleration control. The feedback gain changes in accordance with the generator state variables, based on a nonlinear control rule. By using this control rule, the proposed method is independent of the operating point. The research results are summarized as follows :1.A formulation for the nonlinear digital control of synchronous generators based on the concept of digital acceleration control and an algorithm for the design of controller have been developed.2.The performance of the controller was investigated by using model systems, especially the influences of simplifying the model, parameter change, the movement of operating point, and limiters.3.We must give a lot of care to the sampling period in the proposed method because of the assumption on modeling. An appropriate sampling period was obtained by simulation.4.It was confirmed that the proposed method could be applied to rotating speed control of generator instead of the output control. Performance of the method is the same as that of the optimal regulator.5.According to the investigation into the influence of measurement noises, that on rotating speed is the worst. The low-pass filter is effective in the other measurement noises.