Three-phase UPQC Power Circuit Design

In power users,the proportion of load sensitive to power quality is increasing,and the digital information age has higher requirements for power supply reliability and personalized power supply.Therefore,power quality control devices based on power electronics technology emerge as the times require.Among them,Unified Power Quality Regulator(UPQC)is one of the devices which can solve many kinds of power quality problems comprehensively.It can realize voltage control(voltage drop,distortion),active filter,active/reactive dynamic regulation,balanced compensation,uninterrupted power supply,etc.The power circuit of UPQC is designed and developed in this thesis.By investigating the existing UPQC device topology and control methods,a new three-phase UPQC topology structure is designed.The high frequency isolated DC/DC is used to replace the traditional power frequency transformer,which greatly reduces the device volume,avoids the direct and short circuit of DC capacitor,and enhances the reliability of the system.Combining with this topology,modular design of the structure is carried out from the point of view of easy maintenance and functional expansion.In the design of UPQC power circuit,the effects of power device loss and system efficiency,DC capacitor voltage and current ripple,filter parameters on device performance are studied.By analyzing the working modes of each converter module,the total loss of power transistors under different working conditions is calculated,and the switch with higher efficiency and lower temperature rise is selected.In order to smoothly filter the DC voltage,absorb the pulsating current and prevent the voltage fluctuation from exceeding the given value,the DC capacitor parameters are calculated.In addition to considering this role,it also combines the functions of each converter to meet the design requirements in both steady and dynamic conditions.The design of the filter mainly focuses on the elimination of the high harmonics of the output voltage and current of the converter.The function of the UPQC device is considered comprehensively.In the design method,the compensation target,dynamic performance,ripple requirement,damping resonance,high frequency attenuation,volume cost and other factors are combined to calculate,so that the system performance is better.In Simulink simulation environment,the simulation models of each module of UPQC are established to verify the rationality of the selection of each device in power circuit,and the performance of the device is preliminarily verified.On this basis,an engineering prototype has been developed,and the feasibility and effectiveness have been proved by experiments.