Analysis Of The Harmonics Of Medium And High Voltage Converters

With the increase demand of electricity continually, it is expected to develop higher distribution voltage grade in our country and developed countries, focusing on reducing the transmission loss. And the main trend in our country is to develop 6kV and lOkV voltage grade main distribution circuit and corresponding high voltage AC motor. With the capacity of the inverter improved, the impact of the converter harmonics on the grid and the electrical load will be greater. The topology and harmonic suppression technology of high voltage and large capacity converter have been a focus of study and concern since modern times.Scholars home and abroad with the aim of reducing the input and output harmonic have carried out in depth studies in the high power converter topology and control methods. So far, medium and high power variable-frequency technology has not formed the unified structure and control plan, each kind of plan structure, the principle and input output harmonic frequency spectrum also are different from each other.Medium and high voltage converter topologies are summarized in the paper, and then the paper has analyzed the structure, working and characteristics of various topologies. Taking the multi-pulse rectifier technology and Three-level PWM rectifier as study object, the harmonic suppression technology of medium and high power converter input, which is also known as the rectifier circuit, are proposed, and have analyzed the net-side current harmonics thoroughly; the comparison between harmonics of Medium and high voltage converters and IEEE-519 standard are made. Several kinds of converter output topologies are also presented, including transformer-coupled output, power multi-level cell series, Neutral-Point Clamped (NPC) three level inverter, IGBT in direct series high voltage inverter and multiple structures, and have some detailed analysis about the inverter output harmonic, and also provided harmonic content of NPC and power multi-level cell series circuits with and without other filter. And the output voltage harmonics, total harmonic distortion and the IEEE-519 were compared. Applying Matlab/simulink to simulate the three-level inverter's SPWM and SVPWM strategies respectively, as to SPWM, the article simulated the uniform phrase carriers wave PWM and the opposite phrase carriers wave PWM and compared the result of the simulation. And seeing from the harmonic spectrum, the two control methods exists some relationships in nature.In this paper, the comparison between harmonics of Medium and high voltage converters and IEEE-519 standard are made by building models of Matlab simulation. The harmonic features of several typical converters were showed, which will provide an important reference to choose high power variable-frequency technology plan in the project application.