Study On Electromechanical Coupling Between Electrically Driven Fracturing Pump And Driven Asynchronous Motor

Shale gas needs to be exploited by fracturing equipment.The research on fracturing equipment has been developed from the traditional low-efficiency,high-noise,polluting environment diesel-driven fracturing pump to the green low-carbon electric-driven fracturing pump with high efficiency,low vibration noise and wide speed range.The research on electric fracturing pump at home and abroad is mostly conducted separately from the two aspects of fracturing pump and motor,but few studies and analyses on its integrity.However,performance matching,vibration characteristics and shaft fatigue require electromechanical coupling analysis of the whole electric fracturing pump.In this dissertation,the 5000 HP electrically driven fracturing system is taken as the research object,and its driving motor is 3155 kW asynchronous motor.Starting from the perspective of the operational structural characteristics of the fracturing pump load and the electromagnetic characteristics of the electric motor load,a electromechanical coupling model of the electric fracturing system is constructed by combining theoretical analysis and numerical simulation.The structural dynamic characteristics of the fracturing pump and the electromagnetic characteristics of the electric motor are studied,as well as the influence of the fracturing pump on the electromagnetic characteristics of the electric motor and the system vibration characteristics under various working conditions.The main contents of the dissertation are as follows:First of all,according to the structural characteristics and operating characteristics of the pump,the overall model was built,and the pressure generated by the fluid on the hydraulic end piston head during the operation of the 5000 HP fracturing pump under the fluid solid coupling was obtained,and the free mode analysis and constrained mode analysis were carried out on its crankshaft.Further transient dynamic analysis was conducted by applying piston head pressure as a dynamic load to the overall model of the fracturing pump,and the structural dynamic response characteristics of the crankshaft at the power end of the fracturing pump were obtained.Secondly,based on the motion equation of the electric motor,a shafting dynamics model of the electric fracturing pump was established,and the electromagnetic characteristics of the driving motor during system operation were studied.The no-load starting characteristics were analyzed.Establish a field circuit coupling model for the electric motor and analyze the influence of fracturing pump load on the electromagnetic characteristics of the motor under different working conditions.Finally,the electromechanical coupling analysis model of the electric fracturing system was built.Analyzed the impact of system operation on the crankshaft of the fracturing pump.By simulating the vibration interference generated by the fracturing system during operation under adverse conditions,the influence of the disturbance torque of triangular wave and rising sawtooth wave on the motor torque was obtained.The state equation of the shafting based on the system coupling model was derived.The vibration characteristics of each part of the fracturing system,mainly including the motor end,the fracturing pump end and the shafting,were simulated.The vibration characteristics of the shaft system under load conditions and the impact of the dual ends of the electric motor and fracturing pump on the fatigue failure of the shaft system were determined.