Research On The Reactive Power Of Non-linear Load And Its Measuring Method

With the improving of the electronics technology, there are more and more non-linear loads in the electric power system. These loads produce a serial of high order harmonics, increase the reactive power consumption, lower the power factor, and even interfere the normal running of electric network, some harmful influences to power quality are brought. So the reactive power of non-linear loads is worth to be attention. But the traditional reactive power concept can't explain it completely. And the reactive power of non-linear load has been mentioned in the monographs which are published in recent years, but it's found that the calculating formula is not integral and its physical significance is not very clear after careful analyzing.It introduces briefly the time-domain analysis method and the instantaneous reactive power theory etc. in this paper and points out that there are limitations when they explain the composition of the non-linear load's reactive power. Otherwise, using the classical frequency-domain method is preponderant. Through a detailed description of the reactive power in the linear circuit , it gives a profound knowledge of its physical significance, and then popularizes it to the non-linear circuit. According to the expression formula of the distortion power, we can get the reasonable explain of the reactive power and distortion power of the non-linear load. This paper also briefly introduces the usually used methods of harmonics elimination and reactive power compensation at present.This paper is based on C.Budeanu's classical reactive power definition in frequency domain, and according to the expression formula of the active power and the apparent power, it can be obtained the distortion power's expression formula, which was brought in to counterbalance the power expression. It can be found out from this expression formula that the distortion power is related to the every order harmonic voltages and the different order harmonic currents. And its characteristic is similar to the reactive power's, and its characteristic is that the energy exchanges between the power source and the non-linear load with different frequency, and the integration in a whole period equals to zero, that's there is no energy consumed.According to the conclusions what has been gotten about the reactive power of frequency domain, a virtual instrument is designed by using a computer and a data...