单相低压宽输入高可靠并网逆变器的研究

The single-phase high-reliability grid-connected inverter with low and wide input-voltage range are adopted with two-stage conversion. As the input current ripple is high in the voltage-source DC-DC converter and the output current ripple and voltage spike of the switches are high in the current-source DC-DC converter, the DC-DC converter suitable for low and wide input-voltage range application is used as the front-end DC-DC converter. The power density of the dual-buck full-bridge grid-connected inverter is low, so the high-reliability grid-connected inverter with high power density is adopted as the downstream grid-connected inverter. The three-level (TL) cells suitable for low input voltage are constructed, so the circuit topologies of the TL converters for low and wide input-voltage range application can be proposed. The control method of the proposed TL converter is researched. The influence of different control methods on the voltage stresses of the switches is discussed. The mathematic model of the converter is established. The optimized input and output filters are designed. The closed-loop parameters are designed. The bridge-type converters with an integrated boost capability and boost bridge-type converters with an interleaved parallel capability are presented. The control strategies of the proposed converters are studied. The parameters of the proposed converters are designed optimally. The composition mechanism of the single-phase high-reliability grid-connected inverter is revealed, and the high-reliability cells are constructed. The high-reliability grid-connected inverters with high power density are deduced according to the the grid-connected inverter with unity power factor. The related control strategies for the proposed grid-connected inverters are researched. A new thought will be provided for the DC-DC converters with low and wide-range input voltage application. A theoretical and technical foundation will be established for the single-phase high-reliability grid-connected inverter with low and wide input-voltage range.

针对单相低压宽输入高可靠并网逆变器中前级电压源直直变换器输入电流脉动大、电流源直直变换器输出电流脉动大和开关管电压尖峰大以及后级双降压全桥并网逆变器功率密度低的问题，研究前级适合低压宽输入的直直变换器和后级具有高功率密度的高可靠并网逆变器。本项目拟构建适合低压输入的三电平单元，提出适合低压宽输入的三电平变换器拓扑，研究其控制方法，探讨不同控制方法对开关管电压应力的影响，建立变换器的数学模型，优化设计输入输出滤波器，设计闭环参数；提出集成升压功能的桥式变换器和具有交错并联升压功能的桥式变换器，研究所提变换器的控制策略，优化设计电路参数；揭示单相高可靠并网逆变器的构造机理，构建高可靠性单元，并针对并网逆变器单位功率因数输出的场合，提出具有高功率密度的高可靠性并网逆变器，研究其控制策略。本项目将为适合低压宽输入直直变换器的应用提供新思路，为单相低压宽输入高可靠并网逆变器的发展奠定理论和技术基础。

并网逆变器作为可再生能源与电网的接口装置，将太阳能电池和燃料电池等输出的直流电转换成交流电传输给电网，在分布式发电系统中起着至关重要的作用。本项目围绕低压宽输入高可靠并网逆变器，开展了前级适合低压宽输入三电平变换器、集成升压功能直直变换器、后级高可靠并网逆变器拓扑及其控制方法等三个方面的研究工作，所取得的研究成果如下：(1) 提出了MOS管箝位三电平变换器及其控制方法，所提三电平变换器可工作在三电平和两电平两种工作模式；提出了一种三电平变换器的建模方法，该建模方法可得出三电平和两电平两种工作模式具有相同的小信号模型，使得系统闭环参数的设计只需根据一种工作模式设计即可，简化了设计步骤；提出了一种分段线性函数逼近的简化电路来模拟除法器，提高了精度，降低了成本，该除法器可用于输入电压前馈系统中以便消除宽输入电压对输出电压和电感电流的影响。(2) 提出了集成升压功能的直直变换器拓扑及其控制策略，降低了其功率开关管和整流二极管的电压应力，减小了输入和输出滤波电感的体积和重量。（3）提出了一种并串联组合隔离变换器变压器变比的设计方法，通过变压器变比的设计，减小了整流二极管的电压应力；此外，两电平工作模式下，将较小变比的变换器工作，较大变比的变换器不工作，可减小输出滤波电感的体积和重量。(4) 提出了高可靠并网逆变器拓扑及其控制策略，构建了高可靠性单元；针对并网逆变器单位功率因数输出的场合，揭示了单相高可靠并网逆变器的构造机理。（5）提出了一种三相并网逆变器的软启动控制方法。本项目为适合低压宽输入直直变换器的应用提供了新思路，为低压宽输入高可靠并网逆变器的发展奠定了理论和技术基础。