Research On Power Response Regulation Of Small Variable Speed Hydraulic Generator Unit Under Load Fluctuation

In order to implement the strategy of energy saving and emission reduction,renewable and clean energy has been paid more and more attention in recent years.Small hydropower plays an important role in the development of renewable and clean energy in China.Variable-speed small hydropower units can better adapt to frequent changes in the head of small hydropower stations,effectively improve the operating conditions of small hydropower units and maintain a relatively wide and efficient operation area.In this paper,variable speed constant frequency(VSCF)power generation technology is applied to small hydroelectric units,and the power response regulation characteristics and primary frequency regulation characteristics of small VSCF hydroelectric units are studied.Firstly,this paper introduces the research status of variable-speed hydropower units,and points out the technical feasibility of variable-speed transformation of small hydropower units combined with the advantages of variable-speed constant-frequency technology.Secondly,based on the original small hydropower units,a full-power converter is introduced to form a variable-speed hydropower system,and mathematical models of turbine,water diversion system,governor,generator and converter are established.Then,the speed and efficiency characteristics of variable speed hydropower units are analyzed in depth,and the principle of optimal load regulation of variable speed hydropower units based on the minimum unit flow rate is proposed.The relationship curve between unit output and optimal unit speed is deduced through the similarity theory of turbines,and the method of speed optimization is established.Finally,the simulation models of variable-speed hydropower units and synchronous hydropower units under single load and grid-connected operation conditions are built respectively,and the effects of load variation,control parameters,Tw and Ta on the regulation process of hydropower units are studied.The dynamic and static characteristics of the control system under single machine with load are analyzed and studied.The simulation results show that the dynamic process of the variable speed control system is basically the same as that of the synchronous control system,and the static state can keep the optimal speed.In the case of incorporation into large power grid,the simulation results of power regulation of variable speed units and synchronous units show that the variable speed units can track load changes and operate in optimal conditions,and their power response and primary frequency regulation speed are faster.