Research On Random Pulse Width Modulation Of DC-DC Chopper Converter

At present,DC-DC power is widely used in the fields of general industry,renewable energy and military.The power supply varies from milliwatts to hundreds of megawatts,which has the advantages of high efficiency,low cost,easy control and so on.But the problems of electromagnetic interference and electromagnetic noise are prominent;Thus,it causes the electromagnetic vibration and noise of the load,pollutes the power grid,interferes with the communication of the surrounding electrical equipment,etc.,for example,causes the operation failure of the frequency converter and the adjacent sensitive equipment.In order to realize the electromagnetic compatibility of the converter and reduce the unwanted harmonic components in the electromagnetic noise spectrum,this paper studies the random pulse width modulation method of DC-DC chopper based on the well table lookup method,and the selective harmonic elimination method of random pulse width modulation in DC-DC chopper.(1)A dual random pulse width modulation method for DC-DC chopper based on the well table lookup method is proposed.The method uses well algorithm to generate two groups of random arrays,and makes real-time calls to random data table by DSP,which produces random carrier period and slope.The method can save a lot of time and the algorithm is simple and stable;The peak noise power concentration near the integer times of switching frequency in traditional PWM method can be reduced,and it can be distributed evenly and within a certain frequency range.The method is verified and analyzed by taking the step-down chopper as an example to prove the correctness and effectiveness of the method.(2)A method of eliminating selective voltage harmonics with random pulse width modulation is proposed.Traditional random pulse width modulation method can not selectively eliminate the specific harmonic of the frequency with high harm.Firstly,the mechanism of eliminating the selective voltage harmonics of random pulse width modulation is analyzed;On this basis,a general formula for selective harmonic elimination of random PWM is derived,which can selectively eliminate the harmonic noise power at a specific frequency and its integer frequency ratio.Compared with the traditional RPWM,the method can reduce the harmonic noise power at a specific frequency.The simulation and experimental results show the effectiveness of the method.There are 74 pictures,5 tables and 53 references in this paper.