Design And Simulation Of Grey-Fuzzy PID Governor For Hydro Generator Unit

In order to reduce the enormous pressure of energy consumption and environment protection,it has became a general trend to cut down the proportion of thermal power,which leads to more and more clean power,such as wind power,solar power and hydro power,connect to the grid.However,more clean power means more unstable energy as well as power electronic device,and all of these changes may do harm to the stability of the system.There is no doubt that it is a significant matter to maintain and improve the stability of the system.Hydro energy is relatively stable and easy to control of all the kinds of clean energy.Better yet,available resources of hydro energy are widely distributed in many areas of our country.Nevertheless,the water hammer effect in hydraulic turbine leads to the hydraulic generator's bad performance in governing.Therefore in this paper a new control strategy based on fuzzy control and grey prediction method is put forward to improve the governing performance of the hydro generator unit.In this paper,the relationship between active power balance and frequency stability of the system,as well as the essentiality of a favorable governor to both of them are briefly introduced.At the same time,the characteristics and applications of various control strategies and methods are also reviewed.Regard of the special characteristics of the hydro turbine,an integrated control strategy was considered to be used in the design of the governor controller,in which an intelligent control method,a forecasting method and the conventional PID control method were applied.Finally a Grey-Fuzzy PID controller was designed.In order to verify its control effect preliminary,this Grey-Fuzzy PID controller was applied to a simple three order system,and in MATLAB this system is modeled and simulated.In order to verify the performance of the proposed Grey-Fuzzy PID controller in hydro generator governing system,a hydro generating unit in a single machine and infinite bus(SMIB)system is modeled and simulated in MATLAB.For more realistic reflection for the oscillation characteristics of the system,a linearized model with theeffect of elastic water hammer in consideration is adopted in the model of the pipeline and hydro turbine.The performances of the proposed controller is simulated and justified in the cases of full load and half load respectively under two kinds of common and simple disturbs.Compared with conventional PID controller and Grey Prediction PID controller,the proposed controller performs the best in reducing overshoot and adjusting time with superiority in leading the system into a stable state with robustness.After that,in order to further verify the proposed controller's performance in hydro generator governor,a simple nine-bus three-machine system is modeled as a representative of a multi-machine system.A continuous electromagnetic torque disturbance and a three-phase fault are simulated and imposed to the nine-bus three-machine system respectively,and the results of speed and power angle of each generating unit are recorded and studied.The dynamic simulations by MATLAB prove that compared with the conventional PID controller,the system in which the hydro generator governor is equipped with the proposed controller in this paper needs less time to reach the steady state,whether according to the speed characteristics of each generator units,or in accordance with power angles characteristics between the generators.