Research On Random Pulse Width Modulation Technology Of Five-phase Inverter For Non-sinusoidal Power Supply

In recent years,with its great advantages,the multiphase motor drive system has been widely used in many occasions where high power,high reliability and high performance are required,and has become a hot research field at home and abroad.Among them,the research on the modulation technology of the multiphase motor drive system is receiving more and more attention,especially the modulation strategy of multiphase inverter which can realize non-sinusoidal power supply.With the increasing requirements for electromagnetic compatibility of systems in applications such as aerospace,random pulse width modulation(PWM)technology provides a new solution that can effectively suppress electromagnetic interference without increasing the hardware cost.Based on this background,this paper studies the random modulation strategy of five-phase voltage source inverter drive system for non-sinusoidal power supply.Based on the theory of multiphase space vector decoupling,this paper analyzes the working principle of space vector pulse width modulation(SVPWM)algorithm of five-phase inverter in detail.By comparing several methods of different vector selection,the Near Four Vectors SVPWM is adopted due to its better harmonic performance.Based on the Near Four Vectors SVPWM,the fundamental and third harmonic reference voltage vectors are synthesized at the same time,which realizes the non-sinusoidal output of five-phase inverter.On the basis of the non-sinusoidal SVPWM algorithm of five-phase inverter,this paper introduces two random variables into the switching function to randomize the switching frequency and pulse position.The switching frequency is randomized through the switching delay,while the symmetrical pulse position is randomized through the random distribution of the time of two zero vectors.A non-sinusoidal dual random SVPWM modulation method based on random switching delay and random zero vector timing is proposed,which can effectively disperse the higher harmonics concentrated on the switching frequency and its integer multiple without affecting the output of fundamental and third harmonic components.This method is compared with two kinds of single random SVPWM and the Near Four Vectors SVPWM under non-sinusoidal power supply,which verifies the correctness and validity of the proposed modulation method.In order to evaluate the harmonic dispersion effect of the proposed modulation method more accurately,this paper analyzes its power spectrum density and calculates its harmonic spread factor(HSF),which are compared with other modulation methods to further prove the superiority of the proposed modulation method.Secondly,the random modulation methods using random numbers with different distribution are compared and analyzed by means of power spectrum and harmonic spread factor,in which,the different distributions of random numbers are modeled using variable parameters in the Beta distribution.The results show that the different distributions of random numbers have little effect on the modulation strategy.It proves the rationality of using uniform random numbers which is easy to implement.In order to verify the feasibility of the proposed modulation scheme,the experimental platform for five-phase inverter is set up and the modulation method is realized based on field-programmable gate array(FPGA).As well,the proposed modulation method is compared with several other modulation methods through experimental analysis.The experimental results are consistent with the theoretical analysis,which show that the proposed modulation method can effectively reduce the amplitude of higher harmonic without affecting the output of fundamental and third harmonic components and has better effect of the harmonic dispersion.The research results of the proposed modulation method further prove its great value on practice.