Random SVPWM Selective Harmonic Elimination Strategy Research

In the traditional SVPWM(Space Vector Pulse Width Modulation),semiconductor devices are turned on and off at a fixed frequency,which generates harmonic components related to the switching frequency.These harmonics can cause electromagnetic vibration and audible electromagnetic noise.In order to reduce the vibration noise,the structure and material of the motor can be studied,and the control strategy of the motor can also be studied.In terms of control strategy,a random SVPWM selective harmonic elimination method is proposed in this paper.Based on the traditional random SVPWM,which can disperse the harmonic components at the switching frequency and its multiple frequencies,the harmonic at the specific frequency can be selectively eliminated or reduced by the way that the front and back terms in the PWM pulse Fourier series cancel each other.Firstly,the development status and research significance of random PWM technology are discussed,then the principle of the method proposed in this paper is analyzed.The ideas 1 and 2are deduced respectively under three pulse positions,and the corresponding expression of switching period,random integer k and the general formula of the upper and lower limit of corresponding frequency are obtained.Taking the pulse in the middle of the switching cycle as an example,the simulation analysis is carried out to verify the correctness of the strategy.In this paper,the influence of the fixed frequency SVPWM modulation strategy,the traditional random SVPWM modulation strategy and the random SVPWM selective harmonic elimination method proposed in this paper on the current harmonics is analyzed and studied.Taking the permanent magnet synchronous motor as the control object,the simulation model is built in MATLAB/SIMULINK.The output current spectrum of the fixed switching frequency modulation strategy,the traditional random switching frequency modulation strategy and the modulation strategy proposed in this paper are compared and analyzed,and the effectiveness of the random switching frequency modulation strategy is verified by simulation.The simulation results prove that the modulation strategy proposed in this paper has a good current spectrum uniformity effect,and the power spectrum at the selected frequency and its multiple frequencies can be selectively eliminated.Finally,an experimental prototype of the three-phase voltage inverter is built to verify the feasibility of the proposed control method..