| With the rapid development of modern industrial production and people’s living standards,there is a growing demand for electric energy in production and life.However,fossil energy required by traditional thermal power generation is not renewable and is increasingly scarce,and thermal power generation will cause great pollution to the environment.As a result,clean energy generation has attracted researchers’ attention.As a clean energy with mature development and broad prospects,hydropower generation has been widely used,especially for pumped storage power stations,which have developed rapidly in recent years due to their advantages of peak load reduction and flexible start-up.However,with the expansion of installed capacity of pumped storage power station,the control difficulty of speed regulation system of hydropower unit becomes more and more obvious: Its operating conditions are complex and changeable,so it is impossible to use a single working condition model to study the characteristics of the whole working condition.The hump characteristic and "S" characteristic of the pump turbine are easy to cause the oscillation of the unit,especially when the unit is running in the low head condition,the crimp crossover characteristic of the "S" region aggravates the control difficulty.In order to solve the problem that it is difficult to establish an accurate mathematical model for the speed regulation system of pumped storage power station under different working conditions,the working principle and operating mechanism of each part of the speed regulation system of hydropower unit are deeply analyzed.For the water diversion system,considering the water hammer effect,the mathematical model of the pressure water diversion system is established.Aiming at the nonlinear characteristics of water pump turbine,the nonlinear modeling method is adopted: First,the improved Suter transform is used to eliminate the nonlinear influence of the full characteristic curve of the pump turbine.Then the cubic spline interpolation method is used to obtain the operating parameters of water turbine under specific working conditions,and the nonlinear model of water pump turbine is established.Finally,the mathematical models of PID controller,electro-hydraulic follow-up system,pressure water diversion system,water pump turbine,generator and their load are integrated to establish the nonlinear model of the speed regulation system of hydropower unit,laying an accurate model foundation for the optimization of PID controller parameters.Since the operating conditions of hydropower units in pumped storage power stations are easy to change,in order to obtain PID controller parameters with good control performance under various operating conditions,the ITAE index of low head,medium head and high head was taken as the objective function to optimize the target parameters.Considering the fast convergence and good global optimization ability of non-dominated sorting genetic algorithm Ⅲ(NSGA-Ⅲ)in three or more target optimization problems,NSGA-Ⅲ algorithm is applied to the optimization of multiple head ITAE indexes.The experimental study was carried out on the Hongping pumped storage power station as an example,and the experimental results were compared with those using NSGA-II algorithm to get: the NSGA-Ⅲ algorithm optimized speed control system not only cope with no-load frequency disturbance under three kinds of head has a good dynamic performance and static performance,and under the low and high water head has very strong robustness,rapidity and stability,to verify the NSGA-Ⅲ algorithm in solving the hydro turbine governing system PID controller parameter multi-objective optimization problem when the validity and superiority. |
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