Flux-weakening Control With Current Regulation Factors In High Speed Region Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor is widely used in electric vehicles,aerospace,rail transit,electric drive systems and other drive systems with high-precision speed regulation requirements.Because the flux of permanent magnet is fixed,the output voltage of voltage source inverter is limited,and the rotor speed can't continue to rise after rising to the rated speed,so it is necessary to realize the further rise of rotor speed through the method of flux-weakening.Under the condition of flux-weakening field,the rotor speed is high and the cross coupling of d-axis and q-axis currents is serious,which greatly affects the control performance of the system.In this paper,the decoupling control strategy and the flux weakening control strategy of PMSM are studied.The research works are as follows:1)The mathematical model of PMSM is built,the principle of vector control is introduced,the basic principle and algorithm of SVPWM are summarized,which lays a theoretical foundation for the follow-up study of flux-weakening control strategy and decoupling control strategy.2)In order to solve the problems of non-linear relationship between d-axis and q-axis currents,difficult calculation of working point and poor command following performance of current under the traditional flux-weakening control strategy,a segmented optimization flux-weakening control strategy is proposed.The process of motor speed-up is divided into three stages and linearized appropriately,which simplifies the calculation of the working point,speeds up the dynamic response and strengthens the performance of current follow command.Finally,the simulation results show that the control strategy is better than the traditional control strategy.3)Aiming at the problem that there is only one adjustable parameter in the traditional internal model decoupling control strategy,which can not take into account the decoupling of d-axis and q-axis currents and the regulation of current at the same time,a three degrees of freedom internal model decoupling control strategy is proposed.On the basis of the traditional decoupling control strategy,the proportional adjustment factor and integral adjustment factor are introduced to increase the number of freely adjustable parameters in the system,improve the degree of freedom of the internal model system and optimize the decoupling network.Finally,the simulation results show that the control strategy is better than the traditional internal model decoupling control strategy.4)In order to solve the problem that the coupling of d-axis and q-axis currents is serious,and the change direction of q-axis voltage output by current controller is oppositeto the expected direction of the system when the load changes suddenly in the second phase of speed-up process under the segmented optimization flux-weakening control strategy,a flux-weakening control strategy with current regulation factors in high speed region of permanent magnet synchronous motor is proposed.The q-axis current information is added into the proportion adjustment factor of the three degrees of freedom internal model decoupling controller,and the fuzzy controller is used to adjust the values of the two current adjustment factors continuously,and then the new decoupling network is applied to the segmented optimization flux-weakening control strategy.The control strategy is able to realize the effective decoupling of d-axis and q-axis currents,effectively restrain the saturation of current controller from the source,relieve the pressure of q-a xis current regulation,and strengthen the current regulation performance when the load in the second phase of speed-up process suddenly changes.Finally,the superiority of the control strategy is proved by experiments.In this paper,the integrated research of the flux-weakening control strategy and decoupling control strategy is realized,which enriches the existing flux-weakening control algorithm and decoupling control algorithm of PMSM,and has a certain reference value for the high-speed control of permanent magnet synchronous motor.