Research On Loss Of Permanent Magnet Synchronous Motor Drive System Based On DPWM

The existing minimum loss control of permanent magnet synchronous motor mainly studies the loss of the motor body and completely ignores the inverter loss in the drive system.At the same time,the influence of the inverter modulation method on the loss of the inverter and the motor in the drive system is not considered,which makes the loss of the permanent magnet synchronous motor drive system not to the minimum.In this paper,from the perspective of modulation strategy,according to the clamping characteristics and harmonic characteristics of the intermittent pulse width modulation strategy,it is proposed to apply the intermittent pulse width modulation strategy to the minimum loss control of permanent magnet synchronous motors.The calculation formulas of inverter and motor losses are derived through theory.According to the difference between clamping characteristics and harmonic characteristics,the total loss of the drive system under different modulation methods is obtained.At the same time,considering the change of working conditions during the operation of the motor,an intermittent pulse width modulation strategy suitable for motor loss control is proposed.Finally,the loss model of the permanent magnet synchronous motor drive system is established,and the intermittent pulse width modulation strategy is applied to the minimum loss control.Firstly,the realization method of intermittent pulse width modulation strategy is given,and the simulation model of intermittent pulse width modulation strategy is established in MATLAB/Simulink.According to the modulation wave clamping interval diagram and the switching waveform diagram of different intermittent pulse width modulation strategies,the calculation formula of inverter loss under different intermittent pulse width modulation strategies is derived.Finally,the inverter losses under different intermittent pulse width modulation strategies when the power factor changes are obtained.When the modulation degree M is constant and the power factor changes from 1 to 0,the inverter conduction loss gradually decreases;at the same time,the switching loss of the intermittent pulse width modulation strategy changes with the change of power factor;the power factor is different,the inverter loss the minimum intermittent pulse width modulation strategy is different.Secondly,the theoretical derivation relates the calculation of iron loss and copper loss of the motor to harmonic voltage and harmonic current when considering different modulation strategies to output harmonics.According to the theoretical calculation formula,when the modulation degree M changes,the motor body loss under different modulation strategies is obtained.At the same time,combined with the inverter loss calculation formula,the total loss of the motor drive system is obtained.After comparative analysis,it is found that different modulation strategies have different minimum loss intervals.According to different minimum loss intervals of different modulation strategies,an optimal intermittent pulse width modulation strategy suitable for motor loss control is proposed.Thirdly,based on the basic motor loss model theory,according to the actual inverter loss requirements,the loss model of the permanent magnet synchronous motor drive system is established.In MATLAB/Simulink,the minimum loss control system based on the drive system loss model is established and simulated.The simulation results show that compared with the minimum loss control based on the motor loss model,the system efficiency of the minimum loss control method proposed in this paper can be significantly improved.Finally,the optimal intermittent pulse width modulation strategy suitable for motor control is applied to the minimum loss control based on the drive system loss model.The simulation results show that when the modulation degree M and power factor change,the permanent magnet synchronous motor drive system can always maintain optimal system efficiency.Aiming at the problems of the minimum loss control of existing permanent magnet synchronous motors,this paper proposes to apply the intermittent pulse width modulation strategy to the minimum loss control from the perspective of modulation strategy.Through theoretical calculation of losses,the losses of the drive system under different modulation strategies are obtained.Therefore,the optimal intermittent pulse width modulation strategy suitable for motor loss control is proposed,and the minimum loss control method based on the loss model of the permanent magnet synchronous motor drive system is established.Through simulation comparison,the effectiveness of the minimum loss control method proposed in this paper and the superiority of the optimal intermittent pulse width modulation strategy in the range of full modulation and power factor are verified.