SPWM数字化自然采样法的理论及脉冲误差分析

根据SPWM数字化自然采样法的基本原理,借助图解分析方法,研究了三种误差源对SPWM输出脉冲误差的影响,得出脉冲误差宽度的解析表达式。等效的脉冲误差由采样周期T1、模数转换器位数n1和三角载波计数器计数周期T0三者共同作用而产生的。T1是产生脉冲误差的主要误差源。n1和T0对SPWM输出脉冲误差的影响可以忽略。分析结果表明,减小脉冲误差的主要途径是缩短T1和增大载波比B。基于FPGA的SPWM数字化自然采样法具有原理简单,实现容易,响应快精度高等优点。SPWM数字化自然采样法克服了微处理器实现的SPWM波形很难同时应用于高调制频率和高精度的多电平逆变器中的缺点。

Theory and Pulse Error Study of Digital Natural Sampling based SPWM

According to the basic principle of natural sampling and diagrammatic analysis,the effect of SPWM pulse error induced by digitization is analyzed in detail,furthermore,analytic expression of pulse error is obtained.Pulse error formed by sampling period T1 and analog-digital bit n1 and count period T0 for counter of carrier wave come into being the equivalent of pulse error.T1 is main error fountain for pulse error.The effect of pulse error for n1 and T0 is neglected.The results show the main approach of minishing pulse error is to shorten T1 and augment B.The principle of the proposed method is simple,easy to realize,and its characteristic is rapid in response and high in precision as SPWM digital natural sampling based on FPGA.Digital natural sampling based SPWM overcomes the disadvantage which is hard to apply to multilevel-inverter of high modulation frequency and high precision synchronously for microprocessor realizing SPWM waveform.