Research & Design Of Automatic Generation Control System For Cascaded Hydropower Plant

Cascaded hydropower plant's Automatic Generation Control (Cascaded AGC) lies in the level between power system AGC and plant AGC. It not only needs to balance the real-time load, but also is responsible for adjusting each hydropower plant's generation power according to the error of system frequency. Moreover, for cascaded plant, there are also such complicated constraints as the water quantity balance, the flow time delay, and the demands of flood control and shipping. So the Cascaded AGC should coordinates the power commitment and water discharge of upstream and downstream power plants, using optimal theory and method to achieve the optimal power dispatch and optimal reservoir operation. This thesis is based on the development of the AGC System for the Three Gorges Cascaded Dispatch Center. In the thesis, the optimal algorithm for real-time load dispatch is studied, and for large-scale hydropower plant, a classified control mode is put forward, then for cascaded plant, a fundamental control scheme is provided. Further, an optimal AGC capacity dispatch problem for hydropower in power market is studied. The algorithm research for cascaded AGC is one of the key points in the thesis. Firstly an analysis on security, efficiency and economy performance of the AGC algorithm is carried out, and then the idea of leveled load dispatch algorithm is put forward. The plant level algorithm is divided into three steps: optimal unit combination, UC and load dispatch. For the hinge level algorithm, a POA method is applied to solve the problem and an adjusting algorithm considering the dead zone is provided. For the cascade level algorithm, the Energy Maximization model is discussed and improved, then the coordination alternation method is applied to solve the model, finally a practical algorithm is induced based on the optimal cascade reservoir operation rule. Based on the theoretical research on the algorithms, practical engineering problems of two aspects are also discussed: 1) according to the influences of AGC on hydropower unit, a classified control mode is presented in chapter 3; 2) for cascaded hydropower plant, a leveled control scheme is also presented. Considering the transform of AGC operation mode with the establishment of ancillary market, the thesis focuses on the optimal power sale in both of the active power market and AGC capacity market. The mathematical model is established and then optimal algorithm and numerical examples are also provided.