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运行具有重要意义。在应用最优控制理论对发电机进行控制时，控制器通常是为在某一工作点线性化的模型设计的。虽然这些控制器是有效的设计工作点附近，他们可能不一定是有效的，当操作条件发生了很大的变化。在这项研究中，非线性数字控制方法的同步发电机在电力系统中进行了研究。该方法考虑了被控对象的非线性动力学，应用数字加速度控制的概念。反馈增益根据发电机状态变量而变化，基于非线性控制规则。通过使用该控制规则，所提出的方法是独立的工作点。主要研究成果如下：1.基于数字加速度控制的思想，提出了同步发电机非线性数字控制的数学模型和控制器的设计方法; 2.利用模型系统研究了控制器的性能，重点分析了模型简化、参数变化、工作点移动、限制器等因素对控制器性能的影响; 3.由于模型假设的存在，该方法对采样周期的选取必须给予足够的重视。通过仿真得到了一个合适的采样周期。4.验证了该方法可以代替输出控制应用于发电机转速控制。该方法的性能与最优调节器的性能相同。5.研究了测量噪声对转速的影响，发现测量噪声对转速的影响最大。低通滤波器对其它测量噪声也有较好的抑制效果。

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.