Research Of Hybrid Control For Three-phase Inverter

Power electronics (PE) converters are the equipments used to convert theelectric power with the help of PE components. The principal purpose to study PEconverters is to improve the output power quality and enhance the workingefficiency. Currently, because of the different requirements of the electricequipments, the structures of the PE converters are becoming increasingly complex.Correspondingly, it is also more difficult to design the control strategy for theconverters.The main method to design the controller for PE system is to treat it as thecontinuous time dynamic system. I use the traditional and the modern control theoryto establish the system model, analysis the characteristic and design the controllerparameters. However, in practice, the performance of the converter still need furtherimprove and the current control methods are becoming more intricacy. As a result, itis very necessary to analysis the system from another aspect of the control theoryand attempt to utilize hybrid control method. I treat the PE system as the hybridcomposition of several discrete events happened in a continuous time sequence.Apparently, this method matches the particle working process of the PE componentsbetter and can describe the feature of the system more accurately. Also, it is moreconvenient to design the discrete controller to achieve better output performance.This thesis uses the three-phase voltage source inverter as the object to studythe hybrid control theory. I explore a method to apply the hybrid control strategy toanalysis the PE converter, build the mathematics model and design the systemcontroller. The switched linear theory and hybrid automaton are the two maindevelop directions of the hybrid control. So, I will analysis the PE system from thesetwo different aspects.First, this thesis establishes the switched linear system model of the converterand testifies its controllability and observability using the modern control theory.This is the theoretical basis and premise of further work to design the controller.Second, this thesis establishes the hybrid automaton model of the three-phaseinverter and divides the working process of the inverter into eight different stages. Ialso work out the transient state of the inverter. It helps me get the boundaryconditions to drive the eight stages switch to each other. When the condition issatisfied, it will trigger the turning and the stages will start auto-cycle to form ahybrid automaton.Again, I choose to use MATLAB/Stateflow toolbox to simulate the workingprocess of the hybrid automaton. It helps to adjust the boundary conditions tooptimize the output performance. Also, it can verify the feasibility and effectiveness to apply hybrid control method in PE system.Finally, I build up the hardware of a three-phase inverter, with which I performexperiment with the DSP2812controller. I realize the hybrid control in C languageand use it to regulate the output voltage of the inverter. The practical experimentalresults further verify the hybrid control method is efficient to the PE system.