【作者】 李武华；

【导师】 何湘宁；

【作者基本信息】 浙江大学 ， 电力电子与电力传动， 2008， 博士

【摘要】 世界性的能源短缺和能源危机促使学术界和工业界把目光投向清洁、绿色、安全的太阳能、燃料电池等可再生能源。在新能源并网发电系统中,如何把电压较低的太阳能、燃料电池等输出升压到较高的标准母线电压,成为一个重要的研究课题。论文在总结、归纳现有隔离型和非隔离型Boost变流器(俗称变换器)的基础上,提出了三绕组耦合电感概念。并基于三绕组耦合电感概念,论文提出了隔离型与非隔离型的基本单元结构。通过这些基本单元结构,并进一步引入有源箝位软开关技术和无源无损软箝位技术,论文实现了一系列高增益、高效率和适用于较大功率的交错并联软开关Boost变流器拓扑族。论文还找出了三绕组耦合电感实现的隔离型与非隔离型变流器之间的内在联系,并总结了一般隔离型变流器与相应的非隔离型变流器之间相互转换的普适性原理。首先,论文提出了三绕组耦合电感概念。论文从隔离型交错并联Flyback变流器出发,采用三绕组耦合电感的方式演绎出了一种新型的交错并联Flyback-Boost变流器。论文采用有源箝位软开关技术,实现了一种隔离型的有源箝位软开关交错并联Flyback-Boost变流器,该变流器实现了漏感能量的无损转移和开关管关断电压尖峰的有效抑制。通过一定的拓扑变换。该变流器仅用一套辅助电路就可实现两相交错电路的漏感能量吸收。由于三绕组耦合电感的漏感对输出二极管关断电流的限制能力,有效地抑制了输出二极管的反向恢复电流。在整个开关周期内,主开关管和辅助开关管都实现了零电压软开关动作。论文还采用原边并联、副边串联结构,实现了变流器的倍压输出功能。三绕组耦合电感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,论文提出了一种非隔离型三绕组耦合电感基本单元结构。论文采用三绕组耦合电感概念,把传统Boost变流器仅由占空比决定的单一维数的电压增益表达式,演变成由占空比和耦合电感匝比决定的二维增益表达式,既拓展了变流器的电压增益、避免了极限占空比的工作状态,又降低了开关管的电压应力。为了无损地吸收三绕组耦合电感的漏感能量,论文首先采用有源箝位软开关技术,提出了一种高增益有源箝位软开关交错并联Boost变流器。该变流器实现了主开关管和辅助开关管的零电压软开关动作,三绕组耦合电感的漏感限制了输出二极管关断电流的下降速率,有效地抑制了二极管的反向恢复电流。论文还实现了有源箝位软开关方案到无源无损软箝位方案的过渡,提出了一种高增益无源无损软箝位交错并联Boost变流器。该变流器简化了电路结构,实现了开关管的零电流开通和关断电压的软箝位。论文还提出了一种三绕组耦合电感基本单元结构,根据该基本单元,并引入有源箝位软开关方案或无源无损软箝位方案,论文实现了一系列适用于大电流、高效率、高增益或高降压场合的变流器拓扑族。三绕组耦合电感基本单元的提出,为非隔离型交错并联DC/DC变流器的拓扑生成提供了一种新的思路。论文还提出了另一种非隔离型三绕组耦合电感基本单元结构。论文采用有源箝位软开关技术,实现了一种具有最少箝位开关管的高增益交错并联软开关Boost变流器,该变流器仅用一套箝位电路就实现了两相交错电路的漏感能量吸收和开关管关断电压尖峰抑制。在该变流器基础上,经过一定的拓扑变换,并增加两个输出箝位电容,不仅有效地抑制了输出二极管上的寄生振荡,并可在输出通道上内置一个LC低通滤波器,有效地减小了输出电流纹波。基于该三绕组耦合电感基本单元,论文演绎出了一系列交错并联DC/DC变流器拓扑族,这类变流器可通过一定的拓扑变换来简化软开关实现方案。最后,论文从隔离型变压器和自耦升压变压器的内在联系出发,分析了三绕组耦合电感实现的隔离型和非隔离型变流器之间的关系,实现了隔离型有源箝位软开关交错并联Flyback-Boost变流器、非隔离型高增益有源箝位软开关交错并联Boog变流器和高增益无源无损软箝位交错并联Boost变流器之间的相互转化。同时,也实现了隔离型具有最少箝位开关管的交错并联软开关Flyback-Boost变流器和非隔离型具有最少箝位开关管的交错并联软开关Boost变流器之间的相互转化。论文还总结了一般隔离型变流器与相应的非隔离型变流器之间相互转换的普适性原理,从方法论上实现了隔离型与非隔离型变流器的统一。论文上述提出的新型电路拓扑不仅实现了变流器电压增益的拓展,避免了电路工作在极限占空比的状态;还降低了开关管的电压应力,减小了导通损耗和开关损耗,提高了功率器件的工作可靠性。这类拓扑可通过简单的电路实现开关管的软开关动作,减小了开关损耗;还有效地抑制了输出二极管的反向恢复电流,减小了反向恢复损耗。而且,三绕组耦合电感的交错并联结构简便的实现了系统的功率扩容,减小了变流器中无源元件的体积,提高了变流器的功率密度。论文还对工程应用三绕组耦合电感交错并联Boost电路的实现方法进行了探讨,并在一太阳能并网发电小型示范系统中获得了成功的应用。丰富、详实的仿真及实验结果验证了论文理论研究的正确性。更多还原

【Abstract】 With the shortage of the energy and ever increasing of the oil price, more and more researchers and industrial companies focus on the renewable and green energy sources, especially the solar arrays and the fuel cells. How to boost the low voltage of these renewable sources to a high voltage for the grid-connected applications is a big issue. In these applications, high efficiency and high step-up front-end DC/DC converters are necessary. The major considerations for high step-up converters are the large input current and the high output voltage. How to avoid the extreme duty cycle and how to reduce the peak current are the main concerns in these applications. The concept of winding-cross-coupled inductors (WCCIs) is proposed in this dissertation. Base on this concept, some general isolation and non-isolation basic cells are presented. Then, a family of high step-up, high efficiency and high power interleaved Boost converters with WCCIs are derived by employing the active clamp or passive-lossless clamp schemes. The relationship between the isolation and non-isolation converters with WCCIs is explored and a general law for the topology derivation from the isolation converters to the non-isolation ones is summarized.Firstly, the concept of winding-cross-coupled inductors (WCCIs) is proposed in this dissertation. A novel isolated interleaved Flyback-Boost converter is derived by adopting the proposed WCCIs. And the leakage energy can be recycled and the MOSFET turn-off voltage spikes can be suppressed by employing the active clamp solution. With some topology variations, only one set of active circuit is necessary for the interleaved two phases to realize the ZVT soft switching performance for both the main and the clamp switches. The output diode turn-off current falling rate is controlled by the leakage inductance, which alleviates the output diode reverse -recovery problem. The primary-parallel-secondary-series (PPSS) structure is employed rather than the primary-parallel-secondary-parallel (PPSP) structure to get a higher voltage gain and to reduce the output diode voltage stress.Then, a non-isolated basic cell with WCCIs is proposed in this dissertation. A non-isolated high step-up interleaved Boost converter is derived by inserting the proposed WCCIs between the power MOSFETs and the output diodes of the conventional interleaved Boost converter. The derived high step-up interleaved Boost converter extends the voltage gain, reduces the switch voltage stress and minimizes the peak current. The active clamp circuits are adopted to achieve the ZVT soft performance of the main and the auxiliary switches, which reduces the switching losses and improves the efficiency. The output diode turn-off current falling rate is’ controlled by the leakage inductance of the WCCIs to alleviate the output diode reverse-recovery problem. The passive-lossless clamp solution can be derived from the active clamp solution by some topology variations. The proposed high step-up interleaved Boost converter with WCCIs and passive-lossless clamp circuits can realize ZCS turn-on performance of the switches, suppress the switch turn-off voltage spikes and alleviate the output diode reverse-recover)’ problem. Furthermore, a non-isolated basic cell with WCCIs is proposed. And a family of DC/DC converters is deduced from the proposed basic cell, which is suitable for high step-up/step-down conversions. Then a series of DC/DC converters with WCCIs and active clamp circuits or passive-lossless clamp circuits are summarized for high efficiency, high power and high step-up/step-down applications. A clear picture is made in this dissertation on the general law and structure of the WCCIs for DC/DC conversion in high step-up/step-down applications.Furthermore, another non-isolated basic cell with WCCIs is proposed in this dissertation. A high step-up ZVT interleaved Boost converter with WCCIs and reduced active-clamp switch numbers is derived. Only one set of active clamp circuit is necessary to handle the leakage energy and absorb the MOSFET turn-off voltage spikes. With some topology modifications and by adding another two small capacitors, the voltage ringing on the output diode is clamped and a built-in LC low pass output filter is formed by the leakage inductance and the additional capacitors. So the output current ripple is cancelled. Moreover, a series of interleaved DC/DC converters are realized based on the proposed non-isolated basic cell with WCCIs, which can achieve high step-up/step-down conversions.Last, the relationship between the isolated transformer and the non-isolated high step-up autotransformer is analyzed and the inherent relationship between the proposed isolated and non-isolated converters with WCCIs is explored. Furthermore, a general law for the topology derivation from isolation converters to non-isolation ones is summarized.The voltage gain of the proposed converters in this dissertation is extended and the extreme duty cycle is avoided, which minimizes the peak current, reduces the conduction losses. The MOSFET voltage stress in the low voltage side is reduced, which low-voltage MOSFETs with low RDS_ON can be adopted to reduce the losses. The output diode turn-off current is controlled by the leakage inductance of the WCCIs, which alleviates the output diode reverse-recovery problem. Soft switching performance is achieved by employing the simple, but effective active-clamp or passive-lossless clamp schemes, which reduces the switching losses and improves the reliability of the power devices. Furthermore, the WCCIs with interleaved structure are available to increase the power level, reduce the magnetic size and improve the transient response.A lot of simulated and experimental results are given in this dissertation. And some analysis and design are shown on how to optimize the proposed high step-up and high efficiency interleaved Boost converters in the industrial applications. A 3kW PV grid-connected demo system is successfully built and tested in the laboratory to verify the validity of the theories in this dissertation.更多还原