Research And Application Of The Large Synchronous Generator Excitation Control Strategy

With the implementation of the Three Gorges Project and the project of transmitting electric power from west to east, a large scale power grid is forming. How to improve stability of the grid is an important problem. Excitation controller is a necessary part of the generator set. It's helpful for improving stability of the power grid. Novel control theories, novel constructs and new hardware for excitation systems are discussed in this paper.The adaptive optimal theory is introduced. It's implemented on a digital signal processor. Dynamic simulations on a physical model of single-machine-infinite-bus system verify the ranges of the parameters, such as input gains, output gain, preset parameter of identification, the maximum value of the parameters identified et al. The performance of the adaptive optimal excitation controller is compared with that of a conventional PID excitation controller. The adaptive optimal excitation controller has been already put into practice in several power stations. And some experiments onsite are also introduced. The influence of identification resetting on performance is discussed.The adaptive PSS theory is introduced. The setting rule for the gains of the adaptive PSS is verified in dynamic simulations. The performance of a conventional AVR before and after adding adaptive PSS is compared in dynamic simulations.The dual loop adaptive excitation control theory is introduced. The performance of the dual loop adaptive excitation controller is compared with that of a conventional PID excitation controller in dynamic simulations.An optimal excitation controller based on neural networks is introduced. The back propagation neural networks are applied to simulate the gain curves of the linear optimal excitation controller. Thus the gain curves with better performance are obtained with the nonlinear character of the BP networks. The gain curves obtained by BP networks are verified in dynamic simulations.The excitation controller with high-low voltage rectifier bridges is introduced. It has 2 work modes. In one mode the 2 rectifier bridges are working together in normal situation. It's found in simulation that this mode can work only on condition that the rectifier bridges are triggered with wide pulses. And when the rectifier with high input voltage works, the rotor circuit's situation is the same as that with only one rectifier bridge. The other mode is that only the rectifier bridge with low input voltage works in normal situation. The rectifier with high input voltage works only when a malfunction presents. Thus in normal situation the input voltage of the rectifier bridge is low, and the flash angle is small. Then the harmonic is cut down. The implement scheme of the excitation controller cooperating with the high-low voltage rectifier is introduced.An implementation scheme of the excitation based on programmable computer controller modules is introduced. By calling library functions of the time processor unit all the functions concerning hardware, such as frequency measurement, triggering pulses generator and Fourier A/D conversion, are implemented with the peripheral equipment of the CPU module, IP161. Then the implementation scheme of the excitation based on a digital signal processor, F2812, is introduced. All the functions concerning hardware, such as frequency measurement, triggering pulses generator and Fourier A/D conversion, are implemented with the peripheral equipment on chip. The two schemes were implemented and verified in dynamic simulations. And the excitation controller is operating in a hydropower plant.The adaptive excitation control based on a weighted least square method is presented. Digital simulation on a single machine infinite bus system verifies its performance.