评“瞬时无功理论”和方法

Instantaneous Reactive Power Theory and Methods

瞬时无功理论是20世纪80年代出现的实时测取谐波电流的方法,目的是为了给有源滤波器提供发生谐波的依据。处理周期波形,分离谐波,历来是用傅里叶变换方法。将傅里叶方法与瞬时无功法作对比,可以看出瞬时无功法就是在傅里叶方法上加入一段正交变换,这段正交变换使这个方法在3相电流不对称时,不对称电流(负序)被当作谐波,和谐波合并一起取出。该文指明这个问题产生的原因,并说明在有谐波的3相电流上使用对称分量的风险。

Instantaneous reactive power theory was presented in the 1980s. To detect harmonic currents in real time, these currents will be the formate of harmonic generation of the active filters. The traditional method to separate harmonic components from periodic wave was Fourier transformation. Comparing the Fourier method with the instantaneous reactive power method, we can find out that the instantaneous reactive power method was just the Fourier method plus an orthogonal transformation. This orthogonal transformation makes trouble when the three-phase current was unsymmetry. The unsymmetry currents (negative sequence) will be detected as harmonic currents. This paper explains that the symmetrical component method has the risk of the currents with harmonics.