Study On Flux-Weakening Control Of PMSM

Permanent magnet synchronous motor has been widely used in various fields because of its merits of small volume,high efficiency and high power density.in electric cars,CNC machine tools,aerospace and other fields it is required to have the more wide speed range.Flux-weakening control strategy can effectively improve the speed of permanent magnet synchronous motor.So the performance of flux-weakening control of permanent magnet synchronous motor is studied in this paper.Based on the mathematical model of PMSM,vector control technology was analyzed.Flux-weakening control based on single current regulator(SCR)was introduced to solve the cross coupling problem coused by traditional double current regulator.Traditional flux-weakening control based on SCR was analyzed based on the concept of the voltage limit and current limit circle.It can solve the cross coupling problem and has simple structure and many other advantages,but the load capability,efficiency and voltage utilization ratio will drop.The paper presents a new q-aix voltage given strategy aiming to maximize the load capability.Compared with traditional control mode,this article proposed method can effectively improve the load capacity.For the low efficiency and voltage utilization problem,the paper analyzed another effective stratage,and based on this,the paper presents a new SCR flux-weakening methods combined with over-modulation algorithm.Analyzed the basic principle of SVPWM overmodulation and its realization method in different areas.So the output voltage of the inverter was improved while the voltage of DC bus was still constant,and the flux-weakening speed and the dynamic response was also improved.And using the resonant controller to control the d-axis current to eliminate the effect of low harmonic,thus the performance of flux-weakening control based on SCR was improved.