Research On Harmonic And Reactive Power Current Detection Of Active Power Filter Based On Instantaneous Reactive Power Theory

With the rapid development of power electronic technology and the needs of the development of modern industry, power electronic devices begin to be used on a large scale, which caused a large impact on the power grid. However harmonic pollution is going to be one of the most serious problems. Harmonic affects the normal function of power system, which is urgently needed to be solved. Active power filter(APF) is becoming the main method to solve the problem of harmonic pollution, and the harmonic current detection, as one of the key links in active power filter, its detection effect is directly related to harmonic compensation effect of APF, thus has received extensive attention of many researchers at home and abroad. Since the three-phase instantaneous reactive power theory has been proposed from the 1980 s, the harmonic detection method based on the theory has been widely used in APF with continuous improvement.This paper analyzes the detecting principle of the methods, based on the instantaneous reactive power theory, which including p-q, ip-iq and dq method. And on this basis, this paper then studies on the distorted three-phase voltage, the asymmetric three-phase voltage and three-phase four-wire system, to see the detecting precision and limitations of the above three methods with simulation by MATLAB/SIMULINK software. In the above three methods, the dq method is most widely used, and its detection precision and speed of dynamic response are relatively optimal. However, in the case of asymmetric three-phase voltage, the error does exist by dq method in detecting reactive current, so this article puts forward a kind of improvement method can accurately detect the harmonic and reactive current. Theoretical analysis and simulation show that the improved method is correct and flexible.In addition, due to power grid fault diagnosis and the current limit of actual requirements and so on, except for the full compensation, selective harmonic compensation also occupies an important position. Therefore, selective harmonic detection is also worth attention. Traditional method, the fast Fourier transform, which is complicated in calculation, large-time delay and other defects, is unfit for the fluctuated power grid and the demand of rapid compensation. Based on the generalized instantaneous reactive power theory, this paper puts forward a method which can detect the selective harmonic accurately and quickly in the three-phase three-wire system and three-phase four-wire system. With the simulation software, the results show that this method not only has high precision, fast dynamic response speed, but also considerable flexibility.