Study On The Selective Harmonic Elimination Inverter Based On CPLD

Along with the development of modern electric power and electronic technology, each kind of structure pattern and each kind of control method inversion is published one after another. But speaking of the inverter, no matter outputs request constant voltage constant frequency or variable voltage variable frequency. To eliminate or reduce output harmonics effectively, and to raise utilization of DC voltage always the question which the researcher devotes to solve. Compare with other Harmonic Elimination technology, Selective Harmonic Elimination (Selective Harmonic Elimination is called SHE) has lots of advantages, such as lower switching frequency, high voltage gain, and high quality of eliminating selected harmonics and so on. So this technology can be used in a wide range of VVVF, reactive compensation and active filtering.Achieving specific harmonic elimination of traditional technical methods used mainly MCU + EPROM manner, through software control methods to achieve the required pulse. However, this control method has some disadvantages, such as the poor quality of anti-jamming, the relatively complex structure of the circuit and the delay of procedures. Based on the analysis of the specific Elimination Technology of the basic theory, using Complex Programmable Logic Device (Complex Programmable Logic Device is called CPLD), design a inverter which is based on CPLD specific harmonic elimination PWM pulse (SHE-PWM Selective Harmonic Elimination–PWM)and control circuit, and produce an Experimental Prototype. Replacing the software with hardware circuit control, it can simplify the control circuit and external device structure greatly, and increase the capability of real-time and the reliability of the inverter. This paper clearly discusses the process of specific pulse harmonic elimination, and the realization of this design based on the DSP + CPLD control mode. According to the design, the SHE inverter can be used in more applications.Through the software simulation and the hardware experiment results show that, inverter based on SHE and CPLD can effectively eliminate or reduce the inverter output in the low harmonic content, distribution and harmonic transfer to the high-order harmonic generation. Because the high times harmonics having more inductance, the impacts of harmonics are reduced in the very great degree.