Research On Control And Parallel Technique Of Three-phase UPS Inverter

With the development of economy,the users that require high quality electric energy increase rapidly.However,the quality of electricity form power grid is reducing because of the complicated electrical equipment.UPS(Uninterruptible Power Supply)gradually become the first selection for electricity consumption industry.For UPS an efficient and feasible control method is the key to ensure the security reliability,so the control technique of three-Phase inverter of UPS must be developed all the time to fit the increasing need of high quality of electricity.The invert system of three-phase UPS is the research object of this dissertation.Firstly,the development trends of the UPS are introduced and analyzed the advantages and disadvantages of common control strategy,and the frames of inverter parallel operation.Secondly mathematical model of three-phase inverter is built under three-phase static coordinates,two-phase static coordinates and two-phase rotation coordinates.After that close loop of voltage and current controller is designed and droop control method is added in to realize parallel operation without signal lines and finished simulation experiment.Thirdly,current sharing status under different condition when the UPS in parallel operation mode is analyzed,and the mathematical model of droop control is built under the theory of time-varying vector,and optimization design method is given.Although compared with traditional method space vector pulse width modulation has the advantage of low harmonic distortion rate,for any PWM inverter it will contains a large number of harmonics inevitably.This dissertation analyzed the factors affect output voltage harmonic by mathematical derivation and simulation analysis and proposed a solution to compensate the dead zone.At last,based on the theory analysis hardware experiment is done include the design of voltage and current sampling,protective circuit,drive circuit.Based on the SYS/BIOS real time operating system from TI the software is designed for TMS320F28335 float point DSP to verification the control theory of three-phase inverter with SVPWM.