一种组合型中点SPWM采样方法的研究

  目的  为了降低中频逆变电源的开关频率，保证输出波形质量，同时易于数字化实现，提出一种基于切−割线中点逼近的SPWM采样方法。  方法  推演证明能够逼近自然采样法的数量关系，并搭建Matlab/Simulink仿真模型，将此算法设计应用在中频逆变装置上，从仿真与试验两个方面验证所提方法的正确性。  结果  仿真结果表明，基于切−割线中点逼近法的输出波形的总谐波失真为2.64%，小于对称规则采样法的3.99%。现场工程试验结果表明，基于切−割线中点逼近法的波形质量明显优于对称规则采样法，既降低了开关频率又兼顾了总谐波失真要求。  结论  基于切−割线中点逼近的SPWM采样法应用在中频电源中，有效克服了对称规则采样法输出波形质量不高、开关频率高等不足，理论分析和工程实践均验证了所提方法的合理性与正确性，并可广泛推广到中频电源实装领域。

On a combined-midpoint SPWM regular-sampling approach

  Objective  In order to reduce the switching frequency of an intermediate frequency inverter power supply, ensure the quality of the output waveform and realize digitalization easily, a SPWM sampling method based on a tangent-secant midpoint approximation is proposed.   Methods  It is proven by deduction that the quantitative relationship of the natural sampling method can be approximated, and a Matlab/Simulink simulation model is built. The algorithm is designed and applied to an intermediate frequency inverter device, and the correctness of the proposed method is verified in the two aspects of simulation and experiment.   Results  The simulation results show that the total harmonic distortion (THD) of the output waveform based on the tangent-secant midpoint approximation method is 2.64%, lower than the 3.99% of the symmetrical regular sampling method. The waveform quality of the tangent-secant midpoint approximation method is obviously better than that of the symmetrical regular sampling method, as it not only reduces the switching frequency but also takes into account the requirements of THD.   Conclusions  SPWM sampling based on tangent-secant midpoint approximation is applied to the intermediate frequency power supply and is able to effectively overcome the shortcomings of the low-quality output waveform and high switching frequency of the symmetrical regular sampling method. Both theoretical analysis and engineering practice verify the rationality and correctness of the proposed method, and it can be widely extended to the field of intermediate frequency power supply installation.