变频器输出有功功率测量方法研究

摘要

讨论了变频器测量自身输出功率的两种方法:通过输出相电流的FFT变换获取基波幅值和相位,利用PWM调制波为输出相电压基波的特点获取输出电压基波幅值和相位,从而计算有功功率;近似相电流为基波电流,对电流进行采样并与相应时刻的PWM调制波数值相乘得到瞬时功率,在输出电压一个周期内对瞬时功率累加后求平均得到有功功率.FFT方法对电流谐波的抗干扰能力强,对相电流基波幅值和相位的获取准确,但占用CPU资源较多;周期内瞬时功率求平均方法计算简单,CPU资源消耗低,但对电流谐波敏感.经过对实际运行变频器输出功率的测量,表明叙述的变频器自身测量输出功率的方法是可行的.%Two methods to measure the output power of inverter was discussed:calculating the output active power by getting the fundamental amplitude and phase of the output phase current through the FFT transform and obtaining the fundamental amplitude and phase of the output phase voltage according to the features of PWM modulation wave;regarding the phase current as fundamental current,and calculating the active power by average the instantaneous power within a period,which came from the sample current multiply PWM modulation value.The FFT method had a strong anti-interference ability to the harmonic current,and could obtain fundamental amplitude and phase accurately,yet it required more CPU resources.The latter method was simple in calculation and required less CPU resources,but it was sensitive to current harmonics.The experiment of the actual system showed that the methods to measure output power of inverter was workable.