Study On Stability And Regulation Quality Of Primary Frequency Modulation For Hydropower Units

The primary frequency modulation function of the hydro-generator set is essential to maintain the stability of the grid frequency,especially for some grids that can be used for rapid regulation and have less access to the grid.If the unit’s primary frequency modulation function does not play its due role,it will reduce the frequency control level of the grid and increase the probability of accidents.In this paper,the stability and regulation quality of primary frequency regulation of hydropower units are studied.The main contents are as follows:(1)A mathematical model of primary frequency modulation of hydropower units was established,Based on the elastic water hammer model of the diversion system of the hydropower station,the PI regulation of the governor,and the linear model of the turbine,the overall mathematical model of the primary frequency modulation of the hydropower unit is established.(2)The research on the stability of the next frequency modulation in the governor power mode is carried out.First,the total transfer function of a frequency modulation is derived.Using the Rolls-Herwitz stability criterion,the operating stability domain with the governor parameters as variables is calculated;Secondly,for an engineering example,the effects of water strike phase length,water flow inertia time constant,and servo response time constant on the stability domain are analyzed.The smaller the Tr value,the Tw value and the Ty value,the better the stability,and the worse the stability is;Simultaneously analyze the influence of turbine characteristics on the stability domain and find out the most unfavorable conditions in the operating range.(3)The simulation quality simulation study of the unit’s primary frequency modulation was carried out.Firstly,the influence of the water flow inertia time constant Tw and the water hammer phase length Tr on the adjustment quality in the water diversion system is analyzed.When the water flow inertia time constant Tw is smaller,the adjustment quality is better,and vice versa.When the water strike phase value Tr is 1,the adjustment quality is the worst.In general,the value and value have less influence on the frequency modulation of the unit;Secondly,the influence of governor proportional gain Kp and integral gain K1 on the adjustment quality is analyzed.It is concluded that the smaller the proportional gain Kp is,the better the adjustment quality is.The larger the integral gain K1 is,the better the adjustment quality is;Finally,the influence of turbine characteristics on the quality of primary frequency regulation is analyzed,and the working conditions of five different heads under fixed opening degree and five different opening degrees under rated head conditions are obtained and compared.Find out which is the most unfavorable condition.