Optimal Switching Frequency for Three-phase Bipolar Inverter with Different Dead Time

In order to optimize the design parameters of inverter, an optimization method of inverter switching frequency was proposed. In this paper, the three-phase voltage type bipolar SPWM bridge inverter was taken as the research object. Firstly, the output PWM wave was analyzed by using double Fourier transform and Bessel function, and the spectrum of SPWM with dead time was obtained. On this basis, the relationship between THD and switching frequency was analyzed. It is found that there is an optimal switching frequency that makes the THD of output voltage minimum. Secondly, according to the principle of impulse equivalence, a dead time setting rule closing to the actual situation was proposed. Thirdly, the piecewise linear Lagrange interpolation method was used to fit the formula of choosing the optimal switching frequency with different dead time, and a method of inverter switching frequency selection based on the lowest THD considering the dead time was proposed. Finally, the experimental prototype of three-phase voltage type bipolar SPWM bridge inverter based on TMS320F28335 control chip was built to verify the effectiveness of the proposed scheme.