基于移相串联优化光伏系统高电压等级直流功率汇集的关键技术研究

Abstract： As the photovoltaic power generation capacity increases, one of the current development trends is to raise voltage level of photovoltaic system. The 1500V voltage level photovoltaic system has the advantages of low cost, high efficiency and convenient maintenance. In addition, the invert technology of high voltage level photovoltaic system has been researched mostly and maturely, and there is less optimization study on the DC power influx. Therefore, based on the phase-shifting series scheme of DC modules, this project researches on the technology of DC power influx applied to 1500V photovoltaic system, and the DC/DC converter is used to realize MPPT and increase power output; meanwhile, the number of passive filter components can be reduced, and the volume and weight of filter is decreased as a whole, which is beneficial to further increasing the system efficiency. The operating principles and realization of some new DC power influx schemes, such as two-level square wave in series, sine half-wave in series, multi-level step wave in series and so on, are studied; these DC/DC converter topologies without filter, including two-level square wave, three-level step wave with changed turn ratios, three-level step wave with switched capacitor, dual voltage rectifying and so on, are constructed to adapt to different framework, and these performance index, such as efficiency, stress, leakage current, subject range of input voltage, can be balanced; according to the DC modules and the system, the photovoltaic system is controlled in phase by adjusting the phase-shifting angle dynamically, which can ensure the system performance and reliability. According to theoretical analysis, simulation and experimental validation of the above content, a novel 1500V photovoltaic power generation system is constructed, and the technology is further expanded to higher voltage-level new energy power generation filed. They are conducive to exploring new theoretical methods and technological approaches to improve the efficiency and reliability of high-capacity new energy power generation system.

随着光伏发电系统容量的增加，提升系统电压等级成为发展趋势之一。1500V电压等级光伏系统具有低成本，高效率，维护方便等优势，该架构逆变技术研究较多且相对成熟，但关于直流功率汇集优化研究较少。本项目基于直流模块移相串联方案研究1500V系统直流功率汇集技术，采用直流模块实现分布MPPT，提升发电量；整体消减无源滤波元件，减小体积重量，进一步提升效率。研究两电平方波、正弦半波、多电平阶梯波等串联架构工作原理及实现；构建无滤波器DC/DC变换器拓扑适应不同架构，包括两电平方波、变匝比三电平、开关电容三电平、倍压整流等结构，兼顾效率、应力、漏电流、输入电压适应范围等性能指标；动态调整移相角，模块及系统层面协调控制保证系统稳定可靠。通过对上述内容理论分析、仿真和实验验证，为构建新型1500V及更高电压等级光伏系统、提高大容量新能源发电系统效率和可靠性探索新的理论方法和技术途径。

项目针对1500V光伏系统，研究基于移相串联优化的直流功率汇集关键技术。随着光伏发电系统容量的增加，提升直流母线电压等级至1500V可有效提升系统效率和发电量，降低成本。项目提出了1500V直流模块移相串联方案的基本构建方式，给出了两电平方波、正弦半波、多电平阶梯波等串联架构模式并就其工作原理及特性展开深入研究。通过隔离型直流变换器移相输出串联再集中滤波的方式，在兼顾器件电压应力的同时整体消减了无源滤波元件，且滤波前波形易实现多电平，从而减小体积重量。针对具体的串联架构，提出了多种无滤波器DC/DC变换器拓扑，包括多电平方波、变匝比多电平等结构。对其中典型拓扑的研究表明，直流模块移相串联技术能更好的兼顾效率、应力、输入电压适应范围等性能指标。采用直流模块串联还可实现分布MPPT，提升发电量。结合后级逆变器研究，项目给出并研究了直流模块移相串联架构的系统总体控制方案，实现系统稳定可靠运行。对基于项目架构的光伏逆变系统展开了深入探讨，并在无直通逆变、无源无损软开关等方面给出并实现了技术优化，利于提升系统可靠性。研究工作基本构建了1500V直流模块移相串联架构的理论架构和关键技术，达到了可靠性高、变换效率高等预期目标，为构建实用型装置奠定了基础。. 项目共发表SCI论文6篇，重要核心期刊论文4篇，申请发明专利4项，培养硕士研究生4人。除在新能源发电系统展现良好应用前景外，项目技术在废水废气处理高压电驱动器方面取得应用推广，为2017年南京工业大学所获得的1项江苏省科学技术三等奖提供了重要支撑。项目后续将在正弦半波式直流模块移相串联架构、电驱动器应用优化等方面展开持续研究。