Research On Instantaneous Reactive Power Theory In The Detection Of Harmonic And Reactive Currents

With the development of science and technology,more and more power electronic equipment is applied in the power grid,which brings serious damage as well as convenience to the power quality.In order to ensure the quality of power supply,the research on harmonic is an important branch in the field of power quality optimization.Accurate harmonic detection is the premise of controlling harmonics.New ideas of the harmonic and reactive currents detection have been presented due to the instantaneous reactive power theory,which application prospect is wide.MATLAB/Simulink software is used to analyze the harmonic and reactive currents detection system based on the instantaneous reactive power theory.First of all,A three diode rectifier circuit with inductive load is built as a harmonic source.Harmonic and reactive currents are detected by p-q detection system and d-q detection system based on the instantaneous reactive power theory when the voltage is symmetrical without distortion,distortion or unsymmetrical.Detection results are contrasted and analyzed.The detection result of d-q detection system is better.But the detection result of harmonic and reactive currents are inaccurate caused by PLL when the voltage is unsymmetrical.The detection result of harmonic is little influenced by the voltage phase because the fundamental frequency is provided by PLL.Secondly,d-q detection system is improved and extended based on the empirical conclusion.Two order Butterworth LPF is designed which is more adapted to d-q detection system.D-q detection system is improved to increase the detection accuracy.PLL is replaced by the sine and cosine calculation model which brings positive sequence in the case of unsymmetrical three-phase voltage.PI feedback loop is added to the detection system in order to improve the dynamic response speed at initial stage of start up.The scope of d-q detection system is expanded to the three-phase four-wire power supply system and single-phase power supply system.Random harmonic currents are detected by the d-q detection system without PLL.At last,the photovoltaic storage micro-grid model is built as a case.The harmonic currents,reactive currents and random harmonic currents are detected to verify the effectiveness of the improved detection system.