Research On Carrier Phase Shifted SPWM For ELF Geolgical Detection

In the underground resources exploration and earthquake prediction field, ELF detectiontechnology can satisfy large scope, deep detecting demand, and it is a new means ofgeological detection. ELF detection techonology need to produce high precision lowharmonic content of artificial signal field source, in many of the control method, sine pulsewidth modulation (SPWM) control method has the incomparable advantage in harmonicelimination performance on ELF. Carrier Phase Shifting SPWM (CPS-SPWM) controlmethod is a new control method developed from the basis of SPWM control method. it isoften used in cascade type multilevel transform circuit, and with less harmonic content thanthe basic SPWM control method. So in ELF geological exploration use CPS-SPWM controlmethod have many advantage.This paper first elaborates the CPS-SPWM control method theoy, and deduces theexpression of the output voltage of the cascade type multilever converter, from the expressionwe can see that the CPS-SPWM control technology has got a good harmonic eliminationperformance. Through the MATLAB/Simulink modeling simulation, the related parametersthat can influence output current harmonic such as modulation ratio, carrier ratio, carrier’sfrequency and modulation mode are slected. Then we use the FPGA realize CPS-SPWMcontrol signal generation, and introduce ideas of the high stability and accuracy of theCPS-SPWM signal generation,and realize the sine modulation wave, triangle carrier waveand dead-zone control function modules and form the CPS-SPWM drive signal system byVHDL hardware description languag. Finally through the constructing of the experimentalplatform, we verifie the related simulation conclusion, which further proof the CPS-SPWMcontrol method have superiority on the application of ELF geological exploration.