Harmonic Spectral Analysis Of Output Voltage For Matrix Converter

As a green power converter,the matrix conver has received great attention in the field of motor drive and wind power generation due to its excellent characteristics: compact structure,high power density,bidirectional energy flow,controllable power factor,good compatibility with the power grid,etc.Influenced by the switching characteristics of power electronic devices and modulation methods,the existence of harmonics in output waveform of matrix converter is inevitable,incurring harmful effects on practical applications such as electromagnetic interference and noise.Therefore,the main object of this paper is researching the output voltage harmonics of the matrix converter for the purpose of improving harmonic analysis theory of matrix converter and providing a reference for harmonic suppression.In conventional methods such as fast Fourier transform(FFT)and the double Fourier analysis,the harmonic characteristics of matrix converter(MC)are difficult to be expressed accurately because the frequency of output voltage waveforms are related to the input and output frequencies as well as the carrier frequency,which are independent of each other.Thus,to solve this problem and obtain accurate harmonic spectrum,this paper proposes an analytical method to determine harmonic components based on triple Fourier series,which take the input and output frequency and carrier frequency into account.The theory about Fourier series is introduced in detail first,and then the expressions of output voltage harmonics are derived based on triple Fourier series combined with direct transfer function modulation strategy of matrix converter.And the frequency and amplitude expression of each harmonic is obtained by the way.Finally,the spectrums of the output voltage at different frequencies are obtained.According to the results,the harmonic distribution characteristics as well as main harmonic components are analyzed and summarized.In this paper,the above harmonic calculation method is applied to space vector modulation which is more complex than direct transfer function modulation strategy but more widely used in matrix converter.First,the space vector modulation principle of the matrix converter is analyzed.And then the triple Fourier coefficients of the output voltage harmonics expression are obtained,and then frequency and amplitude of each harmonic is solved.Finally,the output voltage harmonic spectrums are achieved.According to the spectrum,the output voltage harmonics distribution role and the main harmonic components of the matrix converter under the space vector modulation strategy are analyzed and summarized.The output voltage experimental waveforms of matrix converter under two modulation methods are analysised by FFT,a contrast between FFT results and theoretical results under different frequencies shows that the harmonic calculation method proposed in this paper can get a accurate spectrum no matter what the value of input frequency,output frequency and carrier frequency are.In addition,the harmonic calculation method proposed in this paper is also applicable to other improved space vector modulation strategies or indirect matrix converters.