Research On High-performance Modulation Algorithm Of Industrial Inverter

Frequency Converter is widely used in many devices amony all kinds of industry,which becomes the main means in power-saving, enhanceing production automation level,improving traditional industry and product quality, promoting the technology development.Frequency Converter is the popular new technology in economy activity. While, itsmodulation algorithm still exists some defects such as high common-mode currents andswitching power comsumption. It’s necessary to design and improve the new modulationalgorithm in the controller of Frequency Converter. As a result, the research on industrialFrequency Converter high-performance modulation algorithm is done:After introducing the structure, modulation and variable frequency speed controlalgorithm, the theory of common-mode voltage present and common-mode currentnegative influence is analysed. The relationship between common-mode voltage andcurrent is deduced on the basis of mathematical model. Summing up the othercommon-mode voltage reduction method, the new common-mode-voltage reductionSVPWM is proposed. Moreover, dead-time error effects is analysed and dead-timecompensation algorithm principle is introduced. The2new improved SVPWM issimulated On the MATLAB/Simulink.The hardware design of Frequency Converter is composed of rectifier circuit, invertercircuit, power-stage protection circuit, DSP controller system and its peripheric circuit,IGBT driver and protection circuit and fly-back switching power supply. Regarding theelectrical parameter of low-pass filter circuit in sensor signal process, the result is gainedby means of PSPICE simulation. Taking the cost, EMC and efficiency of system intoaccount, related schematic diagrams and PCB diagrams are drawn.The software design comprises main subprograms, which consists of keys scanningprocedure and system status process procedure, PWM signal production interrupt subprogram, motor startup subprogram, voltage-frequency adjustment subprogram, ADsampling interrupt subprogram and fault protection interrupt subprogram. Not only theconvential SVPWM is realized, but common-mode-voltage reduction SVPWM anddead-time compensation SVPWM is finished as well on the hardward platform metionedbefore.System debugging of Frequency Converter is described. In the different stages ofhardware circuit design, the corresponding control procedures are developed anddebugged step by step. Eventually the whole program’s compilation and debugging arecompleted. A number of problems, such as jitterring elimination of the keyboard, the shortcircuit of the IGBT in a phase in common-mode voltage reduction SVPWM, and so on,are encountered and solved during debugging the system. The prototype of a industrialFrequency Converter with high-perfomace modulation algorithm is produced andexperimented. The measured results show good effects satisfying the purpose of thedesign.A new method to improve stator-side power factor is proposed, which is theapplication of power factor corrector technology (PFC) in the cascade speed controlsystem. By constructing the equivalent model in which motor parameters are converted torotor side, the new cascade speed control system can be equivalent to rotor resistancespeed control system when active PFC substitutes for traditional incontrollable rectifier.The equivalent resistor’s formulas, changing rules is proposed. The influence on statorpower factor, electromagnetic torque and proves is also analyzed and these parameterswill be better in new system. Owing to the low frequency of the rotor inductive voltage,specific consideration and parameters calculation of the single phase APFC’s componentsare analyzed. Then a new three-phase low-frequency PFC on rotor side is realized basedon the symmetrical balanced Scott transformer and2single phase APFCs. DC outputvoltage with superior low ripple is gained. The entire system is established in MALABsimulation platform, the simulation conclusion proves the theoretical analysis.