Research On The Key Technologies Of The Power Unit And Power Device Cascading Technique Applied In The Medium-high Technique Applied In The Medium-high Voltage Power Conversion

China’s recent economic development relying on industrial investment and infrastructure construction, resulting in high energy consumption, high emission industries excessive growth of electric power consumption, energy utilization efficiency is low. It has seriously hindered the realization of energy-saving target of the11th Five-Year plan. How to avoid unnecessary loss of electric power in generation, transmission, distribution, and to improve energy utilization efficiency, finally to achieve the goal of energy saving, is undoubtedly the main topic of power electronic technology. Power electronic technology in high voltage, high power will play a more and more important role. Therefore, in this paper, following this hotspot in this field of research, some key problems must be comprehensively studied and discussed in the topic of the high-voltage, high power power conversion.Based on the state of art of rectifiers, which used as the former stage of high voltage, high power electronic converter, rectifiers always employs multiple-pulse transformers to improve their performance. Because multiple-pulse transformers can eliminate harmonic, and improve the power factor. This paper proposes a novel class of converters, which can increase the frequency of the multi-pulse transformers, to reduce the weight and volume of these traditional phase-shifting transformer, even to reduce the the volume and weight of the rectifier system. In this way, it can be easily adopted. Cascade topology of power unit makes it possible to realize the high-voltage, high-power, high-frequency power conversion using low-voltage power device. Because of the reasonable modulation, it is also possible to avoid using bi-direction power switches, effectively reducing the system complexity, overall system cost. On this basis, in order to theoretically proved that multiple-pulse converters based on high-frequency-operated transformer can also reduce the harmonic, this paper has established the system model of this converters. The state equations of voltages and currents of the power unit, the high-frequency-operated multiple-pulse transformer, the rectifier circuit have been listed one by one. It is proof that line current of both two multiple-pulse rectifier have exactly the same mathematical. It illustrates that the12-pulse converter based on high-frequency-operated transformer can also eliminates the5and7harmonics of the line current. In addition, this paper also compares two kinds of rectifier filter circuit employing by multiple-pulse converter, and make a detailed working mode analysis of the multiple-pulse converter. Parameter design process for the AC filter inductor, LC filter network, and the high-frequency-operated transformer are presented, In order to provide useful reference to the design and application of practical engineering and to shorten the project development cycle. In order to simplify the existing high voltage, high power converter topology, which seems relatively complex, this paper tries to connect low-voltage power devices in series to solve this problem. This paper presents a novel voltage sharing topology of commercial IGBTs in series with a high-frequency-operated transformer. This share-voltage topology of power device in series with passive components can avoid the complex design process of gate voltage control circuit, and the loss is far less than that of the traditional RCD clamping circuit. In addition, the equivalent circuit modes during the switching transient and effects of parasitic parameters on the voltage sharing performance are studied and discussed further. This paper also gives the calculation method of maximum voltage stress during switching transient. In order to effectively protect these devices in series, and to avoid the voltage spike caused by parasitic parameters, this paper also introduces a diode-clamping circuits to further improve the performance of the voltage sharing circuit. According to the equivalent circuit during switching transient, it gives the parameter design strategy of the diode-clamping circuit.Not only to reduce the volume and weight, and to improve the efficiency and power density of power electronic devices, but also to avoid power devices working at high frequency, EMI issues due to the parasitic parameters, it is necessary to integrate device (IGBT) driver circuit into a chip-level IGBT modules, and to realize the standardization of mass production. After comparing the existing IGBT driver circuit topology, it concludes that the non-isolated IGBT driver is more suitable for integrated circuit. So it proposes a novel driving auxiliary power supply topology, and also points out the design pattern.