【正文】 (2) ? ? ? ? ? ?,tititi psq ?? (3) where ??tip and ??tiq are instantaneous active and reactive currents， respectively。 Singlephase circuit。s power definition is proposed. The results of theoretic alanalysis and simulation show that the proposed method is effective in realtime detecting of instantaneous harmonic and reactive currents in singlephase circuits. When only detecting the total reactive currents， this method does not need a phaselocked loop circuit, and it also can be used in some special applications to provide different pensations on the ground of different requirements of electric work. Compared with the other methods based on the theory of instantaneous reactive power, this method is simple and easy to realize. Keywords Active filter。 Harmonic。 Electricwork 0、 Introduction At present it is a major tendency to limit harmonics with active filters??31? ， which can not only limit harmonics dynamically and pensate reactive power but also can achieve a continuous and dynamic tracking of the pensation for timevarying harmonic and reactive currents and are not apt to be affected by the resistance of electric work. The key technology of active filter is the realtime detecting of harmonics and reactive currents from load currents to receive reference to meet the need of the active ， the result of the filter will be influenced by the accuracy and realtime ability of the detection. On the basis of the theory of instantaneous reactive power in threephase circuit，many relatively mature detecting algorithms for harmonics and reactive currents of threephase circuits have been proposed， such as the methods of p, q, ip and ? ?41?qi However, in singlephase circuits， these methods can not be directly used and an extra 外文原文 2 twophase voltage and current need to be constructed， which lowers the realtime ability and makes the algorithm more plicated. Refs. [1 ,5] presented a method that is construeted on the basis of Fryze39。 外文原文 3 ??tus and ??tis are instantaneous voltage and instantaneous current of electric work, respectively。 n? ， and n? are the phases of the nth harmonic voltage and current, respectively。 that is， the distribution and magnitude of the detected harmonic is the same as that of the harmonic in the detected current. Fig .7 shows the simulated performance of the dynamic response of the proposed method. Assume that the electricwork current is 1800 square wave， which lags voltage by 360 . For ease of observation， suppose the amplitude of the current increases from 100 A to 200 A between 2030 ms， and the waveform of current is shown in (a). (b)(d) are respectively the outputs of the lowpass filter, the detected results of the fundamental current and the harmonic current. It is found that both the outputs of the lowpass filter and the detected results of the fundamental and harmonic currents begin to change at about 30 ms, and then stabilize at 40 ms. Therefore， the time lag is 10 ms. The time lag is caused by the filter. In fact, the lowest order of harmonics to be filtered is 2. Using the digital filtering method to get the average value in one cycle of the lowest harmonic， the steady and accurate result can be obtained after a half power cycle， . ， 10m is obvious that the performance of the dynamic response of this method is good. (a) The voltage of electric work (b) The spectrum of voltage (c) The current of electric work (d) The spectrum of current 外文原文 9 (e) The total reactive current (f) The total active current The detected total active and reactive current (a) The active current ponent (b) Harmonic and fundamental reactive current The detected active current and harmonic and fundamental reactive current (a) The current of electric work (b) The spectrum of current 外文原文 10 (c) The detected harmonic current (d) The spectrum of harmonic current Dynamically detected harmonic current (a) The current of electric work (b) The output current of LPF (c)The fundamental current (d)The harmonic current The simulation of performance of dynamic response 4 、 Conclusion In this paper, a realtime detecting method for harmonics and reactive currents on the basis of the Fryze39。1931(8):225234。當(dāng) 只要求檢測總的無功電流時，這種方法并不需要一個索相環(huán)電路，并且它也能在一些特殊