The Research On Control Strategy Of Inverter Supplies Powering Nonlinear Loads

With the progressing of technology, all kinds of sophisticated electronic equipment havehigher and higher requirement to the quality of power, and the researchers pay more and moreattentions to the study on the high performance inverter. Nowadays, a great deal of powerelectronic equipment are widely used. The loads of three-phase inverter are no longer limitedto the linear loads, more time the three-phase inverter need to power the nonlinear loads.Thetypical nonlinear loads-rectifier loads is the main reason which cause the three-phase inverteroutput voltage distortion. How to achieve high quality output waveform under all kinds ofcomplicated loads has become an urgent problem in the inverter research field. So thisdissertation mainly focuses on the control strategies of the inverter powering nonlinear loads.First, the mathematical models in ABC、 dq and frame for three-phase inverterwere established. Based on the Equivalent Transformation theory, the transform equationsbetween different frame were derived. Then,it was deeply analysed that nonlinear loadscaused the inverter ouput waveform distortion. This dissertation chooses rectifier loads astypical nonlinear loads to research, and the operation principle and optimal design of therectifier circuits are discussed in detail.Based on the analysis of inverter and rectifier loads, the dual-loop controller ofthree-phase inverter was designed in dq frame, and the Quasi-PR controller was designed inαβ frame. The PI control structure was designed for the coupling inverter model indq0-frame, while the control parameters were designed for the rapidity of inner current loopand the anti-disturbance of outer voltage loop. The Quasi-PR controller can achieve highperformance and regulate the output impedance of the inverter.The Quasi-PR controller has a proportional regulator of inner current loop to speed upthe current track and speed.And a multi-resonance Quasi-PR regulator was adopted in theouter voltage loop to achieve high performance and regulate the output impedance of thethree-phase inverter.Based on the mathematical models of inverter and the design of two controllers, thesimulation model of inverter under the two control systems were builded inMATLAB/Simulink. The two control systems performance of inverter were comparedunder the nonlinear loads. The simulation result shows that, both the dual-loop PI controllerand Quasi-PR controller of inverter have high performance under the linear loads, but the Quasi-PR controller has better performance under the nonlinear loadsFinally the experiment platform was designed and constructed while theDSP-TMS320F28335was used for the core of the peripheral hardware circuit. The controlstrategies were realized by programming in DSP. The hardware experiment also prove thecorrectness and availability of Quasi-PR controlling method in this dissertation.