Research On Harmonic Suppression Method Of Special Inverter For High Speed Motor

High speed motor has the advantages of high speed,small volume,high power density and so on.It is widely used in the field of home appliances and industry.The speed of high-speed motor can reach tens of thousands or even hundreds of thousands of revolutions per minute.With the increase of speed,the fundamental frequency of motor will also increase.High speed motor is usually powered by high frequency converter.For high-power high-speed motor,it needs to match the same high-power converter,and the high-power converter needs to use high-power switching devices.The switching frequency of these switching devices will be limited due to the high power.As a result,the switching frequency of the switching device is very close to the fundamental frequency of the motor,and the number of pulses generated in a fundamental period is less,which significantly increases the high-order harmonics in the output current and voltage of the converter,and reduces the performance of the high-speed motor system.At the same time,it will increase the temperature of the motor and reduce the service life of the motor.Therefore,it is of great significance to reduce the harmonic content of the motor output and improve the utilization of electric energy by selecting the appropriate inverter control strategy.This paper focuses on the following aspects of high-speed motor special inverter research:Firstly,the mathematical model of PMSM is analyzed in detail.Several common vector control methods are compared,and the vector control strategy is chosen.This paper introduces the basic principle and two modulation methods of PWM control technology,and chooses the synchronous modulation strategy which is more suitable for high-power and high-speed motor.The topological structure of the main circuit of three-phase voltage source PWM inverter is analyzed,its mathematical model is derived,and the corresponding structure diagram is given.Secondly,the working principle of SVPWM and traditional SPWM are analyzed in detail,and the limitation of their application in high-power and high-speed motor is pointed out.By adjusting the carrier wave ratio,the position and width of the pulse are analyzed.Finally,the simulation model of SPWM synchronous modulation strategy with strict phase locking is built by using Matlab / Simulink simulation software,and it is compared with SVPWM modulation strategy and traditional SPWM modulation strategy.The simulationwaveform is analyzed to verify that the SPWM synchronous modulation strategy with strict phase locking is applied to high-power and high-speed motor.The number of pulses generated in a fundamental period is In the case of limit,it can effectively reduce the harmonic content of stator current,make its waveform closer to sine,and then improve the utilization of electric energy.By adjusting the carrier wave ratio,the position and duty cycle of SPWM signal waveform can be adjusted.The harmonic content of stator current and the total harmonic distortion rate under different carrier ratio are compared and analyzed when the motor is running at high speed,and the best carrier wave ratio in different speed range can be found.