Equipment Devolopment Of 3kV/60kW Modular Multilevel Converter

With the continuous development of the high and new technology, the development of power electronic technology is changing with each passing day too, some engineering field also need the new power electronic technology to support. Today's engineering application, the biggest demand of power electronic technology and equipment are high voltage and large capacity, but the contradictory relationship between the loss of power devices and the switching frequency are still restricts the application fields of high-power switching devices.How can maintain or reduce the switching frequency,and at the same time ensure that the system capacity and output quality,is a research focus.Under this circumstances,the Modular Multilevel Converter(MMC)arises at the historic moment, through the combination of multiple small power module connection to improve system capacity and voltage grade, at the same time also reduces the frequency of the individual switch of the Converter.In view of the technical characteristics,modular multilevel converter become the crux of the problem's solution of power electronic devices application in high voltage large capacity field.Based on the analysis of MMC's working principle and mathematical model,the following research focused on the modulation method and circulation suppression deeply.Based on the developed a modular multilevel inverter prototype, completed the part of circuit simulation.At the begining, this paper generallizes the modular multilevel converter's working principle and mathematical model.After introductions the advantages and disadvantages of several modulation method used with modular multilevel inverter such as the nearest level modulation method,the carrier phase shift sinusoidal pulse width modulation method, carrier phase disposition sinusoidal pulse width modulation method and space vector modulation method, this paper proposes a more suitable to multilevel inverter modified single carrier modulation method,harmonic characteristic is good.The simulation proves the correctness and validity of the method.Then is the modular multilevel converter internal circulation of the analysis and the design of the new type of repetitive con.troller.The circulation mechanism of harmonic component and component analysis, get the inverter internal circulation of regularity and the correction formula.Improve the inductance bridge arm can effectively reduce the content of the internal circulation, but also reduces the economy;The traditional rapid control and can't suppress all harmonics to the greatest extent, increased the difficulty of system design.After the analysis of the repetitivecontrol strategy, combining with the characteristics of two aspects of repetitive control strategy and internal circulation, put forward a without increasing the inductance of the bridge arm of new rapid repeated circulation suppression strategies, and analyzes the stability performance of this control strategy, the simulation results verify the validity of the proposed controller.After the above theoretical analysis and simulation verification, design has developed a 3kv,60kw prototype modular multilevel converter, the main circuit of the system hardware and the control system hardware design.Main circuit hardware design including the composition of the main circuit, the bridge arm reactance, the sub module selection of capacitance and power unit.Control system hardware design includes drive expansion board design and DSP+FPGA controller design, etc.And in this chapter, the design of modular multilevel converter, on the basis of the experimental prototype, the prototype system of sub module debugging, a experiment is carried out and some experimental results are drawn.