Research On Inverter Control And Parallel Technology Of Three-phase UPS Power

With the application of computer in all walks of life is increasingly widespread,Users have put forward higher requirements for the security and reliability of power supply.Uninterruptible Power Supply therefore arises at the historic moment.Inverter,as the core of UPS power supply,is the key to determine the quality of power supply.To this end,a series of control technology of inverter is studied in this paper.Main work is as follow:The mathematical model of the three phase inverter is constructed,and the transformation between coordinate systems is derived and analysis of the difference in control.In the modulation strategy,an improved SVPWM algorithm is introduced to avoid the complex mathematical calculation,which can improve the operation speed.Based on the analysis of the SVPWM output characteristics by using the double Fourier series,harmonic characteristics,power factor and reactive power factor and other factors are integrated to optimize the filter parameter design.In three-phase inverter control,the traditional voltage and current double closed-loop control scheme needs the exact inductance value when decoupling,and the decoupling is not complete when the inductance parameter numerical error exists.In order to solve this malpractice,by introducing synthetic vector reconstruction controller zero point used to eliminate the system poles and achieve the purpose of decoupling control.Simulation experiments show that the improved decoupling control eliminates the dependence of the inductance parameters of the current loop,increases the flexibility of the design,enhances the ability of the system to resist parameter interference,and improves the dynamic response characteristics.Droop control is a very effective control strategy for parallel operation of inverters,which has the advantages of high redundancy and high reliability.However,in the low voltage parallel system,due to the inductance existence resulting in active and reactive power decoupling is not complete,traditional droop method can not be effectively controlled.Therefore,this paper improved droop control algorithm to self-adaption low voltage line inductance changes at first,and then adding the virtual complex impedance to reform inverter output characteristics.Simulation and analysis show that the combined control strategy of the improved droop control and virtual complex impedance can effectively reduce the circulation of the system and improve the reliability of the parallel system.