Research On One Cycle Controlled Power Factor Correction Technology In Three-phase Circuit

Power electronic equipments have become an important part of the power conversion,because of the merits of improving the power efficiency and achieving the green energy.However,with the development of the devices,especially the rectifier in the power supply device,a lot of harmonic pollution and reactive power loss in the public power grid caused a serious influence on the quality of power supply and the equipment operation.Active power factor correction technology can effectively reduce the harmonic contents and improve the power factor of the system.The three-phase circuit APFC technology is one of the hotspots.The three-phase three-wire and three-phase four-wire systems are two kinds of the three-phase six-switch topology structures,taking the two topologies as the research object in the paper,and one cycle control achieves the goal of the three-phase power factor correction.Firstly,the applicability and operating characteristics of one cycle control technology are analyzed based on the basic principle and the general theory in one cycle control.The application of one cycle control technology in single-phase APFC is studied.The control equation is derived and established,and the simulation is analyzed.The results show that the AC-side input current and voltage have the same frequency and phase to achieve the purpose of unity power factor.And the application of one cycle control technology in three-phase circuit is briefly analyzed.Secondly,the basic working principle is theoretically analyzed for one cycle controlled three-phase three-wire APFC circuit.The derivation and establishment of core control equation is made,and the large signal modeling and AC small signal modeling analysis is carried out.The principle of selecting the integral time constant and designing the input inductor and output capacitor parameters is given.The reasons of the instability at light load condition and the difficult switchover from the rectifier to inverter are analyzed.With the introduction of three-phase virtual current,a modified measure is proposed that the sum of the virtual currents and corresponding inductor currents is as the modulation signal.In order to reduce the switching loss,the improvement strategy of vector mode one cycle control is used.The number of switching devices which working in a state of high frequency in each range is reduced.The corresponding simulation model is set up in the Simulink environment,and the simulation analyses verify the correctness and feasibility of the modified one cycle control strategy.Thirdly,the one cycle control equation is deduced for one cycle controlled three-phase three-wire APFC circuit.And the small signal model of the one cycle controlled three-phase four-wire APFC rectifier circuit is established in the rotating coordinate system.In the same time,it has made a detailed derivation and analysis and got the reasons to the DC side capacitor voltage umbalance.The voltage balance control link is added to the control system to solve this problem.The simulation model is set up,and the results are analyzed to verify the correctness of the theoretical analysis.Finally,the study on the design and analysis of experimental circuits is carried on.The TMS320F2812 DSP as the core digital control is adopted to achieve the scheme of one cycle control three-phase three-wire circuit.The hardware and software of the system is designed and experimental verification and analysis is made.The results show that the one cycle control technology can realize the unit power factor in three-phase circuit.