Research On Unified Power Quality Conditioner And Its Comprehensive Detection Method

Currently,electric power has became the most dependent power source in human society.As the power system are becoming more and more complicated,various power loads are becoming diversified,during the transmission and consumption process of electric power,the occurrence of various electric power quality problems are inevitable,so the control and regulation of electric power quality,the guarantee of supplying high quality electric power became the important issues in electric power research.The unified power quality conditioner(UPQC)combines a variety of electric power quality regulation device functions,so it has good compensation effect on voltage quality problems,current quality problems and reactive power,which is a promising electric power quality regulation device.Firsty,this paper first analyzed the main functions and basic principles of UPQC,and took the three-phase three-wire UPQC as the research object to establish the mathematical models of its various parts respectively,based on this,this paper studied the topological structure and working principle of several new UPQC:large-capacity parallel UPQC,modular multi-level UPQC and hybrid UPQC.Secondly,this paper analyzed the detection and calculation methods of UPQC compensation amount,for the problems that in the voltage asymmetry and distortion state,the traditional phase-locked loop's phase detection is out of alignment,this paper used the multi-channel sine amplitude integral circuit with negative feedback to extract the positive sequence components of fundamental voltage from the original voltage signal,and subtract the extracted signal with the actual voltage can directly generate voltage compensation command,which can save the use of phase-locked loop and the calculation is greatly reduced.Thirdly,this paper analyzed the power definition system under several non-sinusoidal conditions,and used the FBD current detection method based on Fryze power definition,and took the fundamental positive sequence voltage extracted from voltage detection section as reference signal,and it didn't required the phase-locked loop,so that the detection of current compensation amount won't be affected by the grid voltage state.Using the integral module with a fixed cycle to extract the DC component with equivalent active electrical conductivity,so that the time delay of current detection was decreased.The voltage and current detection section formed the comprehensive detection of UPQC compensation dosage as a whole.Finally,under the premise of the same tracking compensation control method,this paper compared the compensation results of UPQC under the four detection methods,when using the comprehensive detection method researched by this paper,the time for UPQC to achieve current stabilization compensation is the shortest,and under different voltage conditions,its supply current distortion rate after compensation is the lowest,which has great control effect in voltage dip,asymmetry and harmonic distortion.