| The magnetic field needed for the permanent magnet synchronous motor to rotate is provided by permanent magnet instead of excitation winding.Compared with asynchronous motor, the PMSM has many distinguishing features such as smaller size and lighter quality; higher power factor and higher efficiency; higher flux density and higher reliability. The PMSM is a new type of energy saving motor which is widely generalized in the period of the national12 th five-year. It is widely used in the space navigation, military affairs, ship electric propulsion, fan pump, elevator, air conditioner, direct drive wind power generation system and new energy vehicles. Most PMSM servo-control system need frequency control, however the torque ripple is large when the frequency converter is supplied, the operating stability of the open loop is poor and the noise is big because of the nonlinear electromagnetic of the motor. In some specific applications, such as electrical propulsion, spindle drives and automotive vehicles, a wider speed range is required and the operation is extend from constant torque region to constant power region, which can be implemented by ways of flux-weakening.In this paper, the hardware design of the frequency control system and the flux weakening strategy of permanent magnet synchronous motor are studied,and the specific research is as follows:A new PMSM frequency control system of 30 k W is designed based on the existing hardware of a 2.2kW system in the laboratory. Design of the main circuit and drive circuit, device selection are the emphasis. To reduce the strayinduction,laminated bus bar is applied in the main circuit. Dual-driver core2SC0108 T from CONCEPT is used as the drive core. Control circuit is redesigned based on the existing one. Until now, the frequency control system has been integrated and installed completely and has been tested on a asynchronous motor of 2.2kW. The result shows that it can control the working of the motor.The principle of vector control of permanent magnet synchronous motor is deeply studied. A double closed loop simulation model is built in MATLAB, and the performance of motor starting, speed regulation, load mutation, overload capacity are simulated. The simulation results show that the performance of the motor is in line with the theoretical analysis, which lays a solid foundation for the following research.On the basis of analyzing the theory of the flux-weakening of PMSM, the gradient descent method is used to carry out to weaken the flux field, and the method is deeply studied.To solve the problem of lower load capacity of the IPMSM because of the limitation of DC bus voltage in the flux-weakening region(above the base speed), minimum magnitude error over modulation(MMEOM) is introduced into the flux-weakening region to improve the utilization of DC voltage, and then the load capacity is improved. Combining this method with the gradient descent method, a simulation model is built in MATLAB, the simulation result shows that MMEOM can improve the output torque in flux-weakening region effectively.Using the hardware and software plat of the 2.2kW IPMSM frequency control system, the exiting program is improved and the performance below based speed is better. The experiment result shows that the no-load and load characteristic is good. |
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