【作者】 赵雷；

【导师】 李浩昱；

【作者基本信息】 哈尔滨工业大学 ， 电力电子与电力传动， 2017， 博士

【摘要】 电力电子设备由于具有高效率、高功率密度等特点,已经成为现代工程中电能变换的重要装置。直流变换器作为电力电子设备中最核心的部分之一,广泛应用于工业生产、航空航天、交通运输、新能源发电等领域。经过近几十年的发展,直流变换器的种类越来越多,已经可以根据应用场合筛选出相对较为合适的拓扑结构。但是大部分拓扑仅在特定工况下具有优势,不具有一定的普适性。为此,不断有新的拓扑被提出,以适应一些特殊工况下的应用。对直流拓扑构成本质规律和内在联系的研究,有助于形成拓扑的衍生理论,丰富直流变换器的种类,成为一个重要的研究课题。论文在分析开关型直流变换器的内在构成规律基础之上,提出了变压器耦合单元的构成方法,并将其与全桥直流变换器相结合以拓宽开关管的软开关范围。通过采用不同的组合方式,衍生出一类具有不同软开关特性的组合型全桥拓扑。所提出的拓扑结构,具有软开关范围宽、电流纹波小等优点,能够有效地改善传统移相全桥变换器的性能,从拓扑层面为高效率直流变换器的实现提供了解决方案。本文首先对直流变换器的构成规律进行简要分析,提出了以电感、电容和开关管三种器件构成的单端口基本单元,并对其可行的连接方式进行研究,重构出了Buck、Boost和Buck-Boost三种基本的变换器结构。两组基本单元通过容性耦合的连接方式,可以形成四种拓扑结构,分别对应Buck-Boost、Cuk、Sepic和Zeta变换器。将基本单元中的电感增加一个绕组,构成变压器结构,得到一个新的功率输出端口。该端口与常规的变换器以不同方式进行组合,可以推导出一类新的拓扑结构,能够满足不同工况下的功率变换要求。其次,将变压器耦合单元的构成方法应用到全桥隔离型直流变换器中,以改善传统全桥变换器的性能。全桥拓扑的原边由四个开关管构成,可以形成四个变压器耦合单元,加上自身的主变压器,总共可以构成五个功率输出端口。采用排列组合的方式,对各个端口可行的连接方式进行分析,推导出一类组合型全桥拓扑结构。组合型拓扑由于具有多个功率输出端口,通过一定的变压器耦合方式,可以在输出侧获得具有多电平特性的整流电压,保证在整个开关周期内功率传递的连续性,有利于减小输出滤波器的容量。本文以双端口全桥拓扑为主要研究对象,提出了一种具有零电压零电流开关(Zero-Voltage and Zero-Current-Switching,ZVZCS)特性的双端口组合型全桥拓扑,超前管采用MOSFET,工作在零电压开关状态,滞后管采用IGBT,工作在零电流开关状态。该拓扑具有软开关范围宽、电流纹波低、转换效率高等特点。上述ZVZCS双端口组合型全桥拓扑中,励磁电感储存的能量为恒定值,为了进一步拓宽开关管软开关范围,降低传导损耗,研究了具有储存能量自适应(Adaptive-Energy-Storage,AES)的组合型零电压开关(Zero-Voltage-Switching,ZVS)全桥拓扑。与常规移相全桥变换器相比,AES拓扑通过引入耦合变压器,能够有效地改善软开关范围、二次侧电压振荡、占空比丢失等问题。AES全桥拓扑本身具有双端口功率输出的特性,现有文献只采用其中一个端口作为功率输出,存在较大的环流损耗。基于组合思想,研究了AES拓扑中双端口可行的组合方式,提出了一类改进型的AES全桥拓扑,并详细地分析了该类拓扑的工作原理和电路特性。AES组合型拓扑不仅保留了原型拓扑的所有优点,而且具有更宽的软开关范围和更低的环流损耗,并且副边无需增加辅助二极管,就可以实现原副边功率传递的连续性,能够显著地降低滤波电感电流纹波。最后,对基于变压器耦合的组合型全桥拓扑存在的共性问题进行了分析,并提出了对应的解决方法。组合型拓扑由于存在两个功率输出端口,保证了原副边功率传递的连续性。但是,该特性会造成变换器的电压增益范围变窄。本文通过改变开关管的驱动时序,能够使组合型拓扑在双端口模式和单一端口模式之间进行切换,进而拓宽电压增益范围。组合型全桥拓扑虽然降低了开关管实现软开关的难度,但是仍然是依靠漏感对结电容进行充放电,完成ZVS转换。轻载下,开关管会丧失软开关的特性。本文通过对轻载下组合型全桥拓扑的ZVS转换过程进行分析,发现只要原边励磁电流大于负载的映射电流,两者之差便能够对结电容进行充放电,为零电压导通创造条件,能够进一步拓宽开关管的软开关范围。因此,对于轻载下的组合型全桥拓扑来说,其负载电流越小,软开关的实现条件越容易满足。更多还原

【Abstract】 Due to the high conversion efficiency and high power density,the equipment based on power electronic is increasing rapidly in the conversion of electrical energy applications.DC-DC converters,which have been widely adopted in industry,aerospace,transportation and renewable energy applications,are important part of power electronic equipment.As the development of power electronic technology,the types of DC-DC converters are becoming more rich and the suitable DC-DC topology can be selected based on the electrical specifications.However,the common topologies cannot be applied in some special applications.Many novel DC-DC topologies are proposed to extend the applied range of power electronic.A systematic research on the composing laws and internal relations of DC-DC converters contributes to the theory formation of topology derivation.Based on the analysis of fundamental DC-DC topologies,this thesis proposes a transformer-coupling basic cell(TCBC)to generate some novel derivative topologies.The TCBC is introduced into the full-bridge converter to extend the soft-switching range.Compared with the traditional phase-shifted full-bridge(PSFB)converter,the proposed converters can achieve wide range of soft-switching,low current ripple and high conversion efficiency.By analyzing the structure of switching mode power supplies,a single port cell with inductor,capacitor and switch is proposed.Buck,Boost and Buck-Boost converters can be rebuilt based on the proposed cell.Two basic cells are connected through a capacitor and four topologies are obtained,which correspond to Buck-Boost,Cuk,Sepic and Zeta,respectively.By adding a winding to the inductor,a TCBC with dual port is obtained.The topology families can be obtained by combining the TCBC with the basic converters.The novel converters satisfy the requirements in some special applications.The construction of TCBC in the isolated full-bridge converter is researched.In the primary side,the full-bridge converter is constructed by four switches,which generates four TCBCs.Considering the main transformer,five power output ports can be achieved.By adopting the method of permutation and combination,all the connection styles are analyzed and optimised.The combined converter contains more than one output power port and multilevel rectified voltage can be obtained,which is helpful to reduce the filter inductance and voltage stress of rectifier diodes.This thesis focuses on the combined full-bridge converter with dual port and proposes a novel zero-voltage zero-current switching(ZVZCS)full-bridge converter.The leading-leg switches operate with ZVS while the lagging-leg switches operate with ZCS.The ZVZCS converter can achieve a wide range of soft-switching and low current ripple.The combined full-bridge converter based on adaptive-energy-storage(AES)full-bridge converter is also researched.Compared with the traditional PSFB converter,the AES converter overcomes problems of narrow ZVS range,secondary voltage oscillation and duty-cycle loss.However,the conventional AES converter exists circulating current,which causes more conduction loss.Based on the combined method,some improved AES converters are proposed.In the improved converters,the energy from primary side can be transferred to the secondary side during freewheeling interval.Both the current ripple of filter inductor and the voltage stress of rectifier diode are reduced.Compared with the conventional AES converter,the improved converter can obtain a wider ZVS range,lower current ripple and higher conversion efficiency.The detailed theory analysis and experimental results are presented in this thesis.Finally,the common problems in the proposed combined full-bridge converter are analyzed and the corresponding solutions are also introduced in this thesis.In order to transfer the power continually,the combined converter contains two power output ports,which leads to the narrowed voltage gain.In this thesis,the voltage gain of combined converter is extended by changing the driver sequence of switches.The soft switching operation in the proposed converter is obtained by using the energy stored in the leakage inductance to discharge the junction capacitances.The switches may lose the soft switching characteristic at light loads.By analyzing the ZVS commutation process,it is noted that the difference between magnetizing current and the reflected output current can be used to discharge the capacitances.For the combined full-bridge converter,the light load current is benefit to achieve the soft switching characteristic.更多还原