【作者】 汪东；

【导师】 何湘宁；

【作者基本信息】 浙江大学 ， 电力电子与电力传动， 2009， 博士

【摘要】 电力电子技术是21世纪应用最广泛的技术之一。随着现代科技的迅猛发展,各行业对电力电子系统性能与可靠性要求等愈来愈高。高频化、模块化的电源产品由于其体积小、污染小以及易于维护与扩容,已成为目前的发展趋势。并联技术与交错控制技术的产生使原本单台低频大容量的变流器被多台并联输出的高频、小容量、模块化的电源取代成为可能。电力电子技术也是协助解决人类越发关注的能源短缺与环境污染问题必不可少的技术之一。新型可再生能源由于其绿色、安全、可再生的特点备受人们的关注。为实现和推广低电压输出的新能源的工业应用,科研人员对高增益DC/DC变流器及其后级的DC/AC逆变电路做了大量的研究。为实现变流器的功率扩容,交错并联DC/DC变流器以及逆变电源的并联冗余技术更是研究中的热点。本文首先在总结、归纳常规flyback与forward变流器的基础上,基于常规flyback变流器的电路结构与交错并联的控制方式,提出了在反激变压器的副边串联占空比控制直流电压源的思想,为扩展电路的电压增益与实现自动均流特性提出了一种新思路,并在此基础上提出了flyback变压器与开关电容相结合的flyback-forward概念,实现了一种隔离型的交错并联flyback-forward Boost变流器。该变流器通过反激变压器与开关电容的有机结合,充分利用了变压器的正激特性,降低了激磁电流,提高了磁芯的利用率,并通过开关电容的隔直特性实现了并联支路的自动均流。通过采用有源箝位软开关技术,实现了漏感能量的无损转移和开关管上关断电压尖峰的有效抑制。由于反激变压器的漏感对输出二极管关断电流的限制能力,有效抑制了输出二极管的反向恢复电流,减小了反向恢复损耗,提高了变流器的效率。为了进一步提高变流器的功率密度,本文还采用了单管箝位技术实现了漏感能量的吸收与无损转移。仿真与实验结果证明,隔离型的交错并联flyback-forward Boost变流器具有较高的工作效率。开关电容型flyback-forward概念的提出为隔离型交错并联DC/DC变流器的拓扑演绎提供了一种可实践的思路。其次,本文针对非隔离应用场合,在分析了常规交错并联boost变流器与耦合电感型交错并联boost变流器的基础上,通过采用所提出的占空比控制直流电压源的思路,提出了一种开关电容型交错并联非隔离Boost组合变流器。由于引入了耦合电感与开关电容的组合,电路的电压增益得到了进一步的拓展,同时降低了开关管的电压应力。开关电容的存在使耦合电感不仅工作在传统的储能一释放模式,同时利用了其正激变压器的特性,既充分利用了耦合电感的磁芯,又拓展了变换器的功率等级。由于开关电容的隔直特性,交错并联的两个支路实现了自动均流,简化了控制电路的设计,降低了生产成本。为了实现对开关电容型交错并联非隔离Boost组合变流器的闭环控制,本文采用基本建模法对其小信号模型进行了推导,并采用电压电流双环控制策略实现了闭环控制。仿真与实验结果证明了模型的正确性。随后,为进一步提高电路的可靠性,降低生产与设计成本,本文探讨了开关电容型无源无损交错并联Boost组合变流器的实现方法。首先在分析耦合电感型无源无损高增益boost变流器的基础上,通过采用所提出的占空比控制直流电压源的思路,提出了高增益无源无损交错并联Boost变流器。该变流器通过在电路结构上将箝位二极管交叉连接的方式,在利用箝位电容实现漏感能量的无损吸收的同时实现了两个支路的自动均流。在此基础上,为了进一步拓展电路的电压增益,通过一定的分析与拓扑变换,本文进一步提出了利用开关电容代替箝位电容的概念,并推导出了开关电容型高增益无源无损交错并联Boost变流器。该变流器在保留了高增益无源无损交错并联Boost变流器的所有优点的同时,既拓展了变流器的增益,又降低了开关管的电压应力。在此基础上,为了进一步提高耦合电感的磁芯利用率,本文采用前述的flyback-forward概念,通过添加两个二极管,保证了耦合电感与开关电容的正激电流通路,从而实现了开关电容型无源无损交错并联Boost组合变流器。由于正激工作模式的加入,耦合电感的激磁电流得到了有效降低,变流器的功率密度得到了进一步的提高。耦合电感/反激变压器与开关电容相结合的flyback-forward概念实现了从新型可再生能源的低输出电压到逆变电源标准母线电压的高增益提升。作为采用此概念实现的新型变流器拓扑的工业应用,论文的第五章对逆变电源多机并联系统的实现和优化进行了探讨和实践。在采用瞬时电流平均值均流模式的基础上,论文对逆变电源多机并联系统进行了建模与仿真实验研究。随后,本文通过对在线的逆变器进行编码的方式提出了自动主从式并联控制策略。该控制策略实现了主从机的自动切换,提高了系统的容错能力。针对隔离型逆变器的变压器直流偏磁问题,本文对比了电压型与电流型反馈补偿的优缺点,并提出了一种电压型补偿的反馈控制电路。该电路无需添加额外的辅助电源与控制环节,实现了变压器原边电压直流分量的采样与闭环补偿,具有一定的工业利用价值。更多还原

【Abstract】 Power electronics technology is one of the most widely used technologies in the 21st century. With the rapid development of modern science and technology, the performance and reliability requirements of the power electronics system increase. High-frequency and modularized power products has become the current trend because of the small size, less pollution, as well as easy maintenance and volume extension. Parallel and interleaving control technology have resulted in the replacement of the single converter of low-frequency and high-power with the high-frequency, low-power, modularized converter.Power electronics technology is also one of essential technologies to help solve the energy shortage and environmental pollution problems which are increasingly concerned about by the human beings. Because of its green, safe, renewable characteristics, the new renewable energy sources have received more and more concern. In order to realize and promote the application of the new renewable energy with low output voltage, high step-up DC/DC converter and inverter as the application of the high voltage DC bus have become the research focus. Interleaved DC/DC converter and inverter parallel control technology have become one of the most popular topic in the world because of their easy volume extension characteristic.Based on the analysis and the conclusion of the conventional interleaved flyback and forward converters, this paper put forward the thought that adding a series connected duty cycle controlled DC voltage source to the secondary side of the flyback transformer, which provide a new method to extend the voltage gain and auto-balance the input current of the converter. On the basis of this thought, an isolated and interleaved flyback-forward converter with the combination of flyback transformer and switched-capacitor is proposed. The converter makes full use of the forward characteristics of the transformer which reduces the magnetizing current and improves the utilization of the magnetizing core. The current auto-balancing characteristic is also realized because of the charge balance of the switched capacitor. In order to absorb the energy stored in the leakage inductance and restrain the turn-off voltage spike of the switches, active clamp strategy is adopted. The reverse recovery currents of the diodes are limited by the leakage inductances, so the efficiency of the converter is promoted. In order to improve the power density of the converter further, single switch clamping technique is also examined. The simulation and experiment results show that the isolated and interleaved flyback-forward Boost converter has high efficiency and good performance. The concept of flyback-forward based on switched capacitor provide a new practicable thought of the interleave DC/DC converter.As for the non-isolated application, based on the analysis of the traditional interleaved boost converter and boost converter with coupled inductors, this paper presents a non-isolated and interleaved combination boost converter with switched capacitor implemented by the duty cycle controlled DC voltage source concept. Due to the existence of the coupled inductors and the switched capacitors, the voltage gain of this converter is extended further and the voltage stress of the switch is alleviated. With the help of the switched capacitor, the transformer can not only be operated in coupled inductor mode, but also in forward mode. Therefore, the power level of the converter is improved. The charge balance of the switched capacitor realizes the current auto-balance characteristic of the converter, so the designing and the realization of the converter are simplified. In order to realize the close loop control of the proposed non-isolated and interleaved combination boost converter with switched capacitor, the small signal model is deduced with basic modeling method. Voltage-current-dual loop control strategy is used to implement the close loop control of the proposed converter. The simulation and the experiment results validate the model.In order to improve the reliability of the circuit, passive lossless clamp strategy is investigated. Based on the analysis of the high step-up lossless interleaved boost converter, this paper proposes a high step-up interleaved boost converter with passive lossless clamp circuit using the foregoing duty cycle controlled DC voltage source concept. With the structurally crossed diodes, this converter can not only realize the passive lossless clamp of the switches, but also has the current auto-sharing characteristic. In order to extend the voltage gain further, the clamp capacitor is replaced by switched capacitor. As a result, the passive lossless clamping interleaved boost converter with switched capacitor is proposed. With the replacement of the clamp capacitor with the switched capacitor, the voltage gain of this topology in increased and the voltage stress of the switch is alleviated. By adding additional two diodes into the passive lossless clamping interleaved boost converter with switched capacitor, the forward current route for the coupled inductor is obtained. Consequently, a new topology named passive lossless clamping interleaved combination boost converter is presented. Because of the forward mode, this converter achieves high power density and increased voltage gain.The purpose of the flyback-forward conception is to lift the low output voltage of the new renewable energy to the standard high voltage DC bus. As its application, the realization and the optimization of the parallel inverters technology is discussed in the fifth section of this paper. Based on the average current sharing strategy, the modeling, simulation and experiment of the parallel inverters are implemented. Subsequently, a new parallel control strategy named auto-master-slaver strategy is proposed. By encoding the on-line inverters, this strategy realizes the auto master/slave assignment and exchange of the on-line inverters. Therefore, the reliability of the parallel system is improved. In order to restrain the flux imbalance of the output transformer, the close loop compensation using primary voltage and current strategies are discussed. Based on this comparison, a new DC voltage feedback compensation circuit is proposed. This circuit can achieve the primary DC voltage component sampling and compensating with no additional auxiliary power and control circuit.更多还原