Modeling Simulation And Parameters Test Of Alternating Current Excitation System For Variable Speed Pumped Storage Units

To deal with the energy crisis and alleviate the environmental problems,the development of renewable energy has become the common goal of all countries in the world.With the large-scale access of wind power,photovoltaic power generation,and other intermittent energy to the power grid bring great challenges to the frequency adjustment and safe operation of the power grid.As the energy storage power supply with the most perfect technology and the largest storage capacity pumped storage power station has good frequency regulation and peak shaving capacity,which is an effective means to ensure the stable operation of the power grid.The traditional pumped storage units generally use synchronous motors,which can’t adjust the power in pumping conditions and can’t operate in the optimal efficiency range in power generation conditions.In contrast,The new type of variable speed pumped storage units adopts the AC excitation generator,which can realize smooth speed regulation by changing rotor current frequency,not only can realize independent and rapid power regulation,but also can make the units always work in the best state,and improve the operating efficiency.The reason why the variable speed pumped storage units have better performance is that the AC excitation system can give full play to the advantages of the motor.Therefore,this paper studies the operation characteristics of the AC excitation system of variable speed pumped storage units.Firstly,the structure and basic operation principle of variable speed pumped storage units are analyzed.The actual value mathematical model and the per unit value mathematical model of AC excitation motor are established.The mathematical model of the excitation system inverter in the ABC static coordinate system and the DQ rotating coordinate system are derived.The vector control system of the inverter is studied and the decoupling control of output power is realized.Secondly,the selection standard of AC excitation per unit value system is proposed,and the selection method of the base value is explained by using Fengning variable speed pumped storage units,and the interface conversion relationship between the motor per unit system and excitation per unit system is deduced.Under the premise of complete decoupling of the excitation control system,the inner current loop is set as a first-order inertial link by the elimination method.Based on the stagger theorem and the second-order best theorem,the parameter setting principle of the PI regulator in the outer loop is derived.The internal parameters of the motor are measured by the simulation data of the AC excitation system,and a complete test method of the motor parameters is formed.Finally,the electromagnetic transient simulation model of the AC excitation system of variable speed pumped storage unit is built by using RTDS.Based on the electromagnetic transient model,a voltage source electromechanical transient model considering the dynamic process of rotor flux linkage of AC excitation motor and retaining the characteristics of excitation inner loop is established.The correctness of the simplified electromechanical transient model and the effectiveness of the control function is verified by different step disturbance tests.