无死区三相六开关AC/DC双向变流器的拓扑结构及控制技术研究

Three-phase AC/DC bidirectional converter is widely used in new energy power generation, electric vehicle charging station and other occasions. This project takes the three-phase AC/DC bidirectional converter as the research object, and takes the improvement of the operation reliability, efficiency and power density as the research target, to study the topology generation methods and control technology of no dead-time three-phase six-switches AC/DC bidirectional converter, and to overcome the shoot-through problem existed in bridge-type topology and the loss problem caused by diode reverse recovery. The main research contents are as follows. The topology generation methods and control strategy of no dead-time three-phase six-switches AC/DC bidirectional converter are researched to inhibit the current zero-crossing distortion problem in dual Buck converter under half period operation. The parameters and structure of the filter are optimized by statistical optimization modeling method with establishing high and low frequency THD estimation model, in combination with magnetic integration design. Thus the size of the filter can be reduced. From the perspective of the grid voltage distortion, no phase-locked-loop control technology is researched in order to realize the smooth switching between the rectifier and inverter operation modes. Design of controller and soft start-up control based on no damping filter are studied to speed up the start-up of system under the ensure of stability. The research of this project will lay the theoretical foundation for no dead-time three-phase six-switches AC/DC bidirectional converter to realize high reliability and high efficiency.

三相AC/DC双向变流器在新能源发电、电动汽车充放电站等场合有广泛的应用。本项目以三相AC/DC双向变流器为研究对象，以提高其工作可靠性、效率和功率密度为研究目标，研究无死区三相六开关AC/DC双向变流器的拓扑构成和控制技术，克服桥式拓扑存在的桥臂直通问题和二极管反向恢复带来的损耗问题。主要研究内容有：研究无死区三相六开关AC/DC双向变流器的拓扑生成方法和控制策略，消除双Buck变流器在半周期控制下存在的电流过零畸变。通过建立高低频段的变流器THD估算模型，采用统计学优化建模方法，同时结合磁集成设计研究滤波器的参数和结构优化，降低滤波器的规格。从电网电压畸变的角度，研究无锁相环控制技术，实现整流和逆变工作模式的平滑切换。研究基于无阻尼滤波器的控制器设计和缓起动控制方法，在保证稳定性的条件下加快系统起动速度。本项目的研究将为构成高可靠、高效率的无死区三相AC/DC双向变流器奠定理论基础。

三相AC/DC双向变流器在新能源发电、电动汽车充电站、UPS等场合有广泛的应用。传统的三相桥式AC/DC变流器具有功率器件少、功率因数可控等优点，但为避免桥臂直通问题而加入的死区会导致谐波含量增加，现有的死区谐波补偿方法则对控制系统提出了更高的要求。本项目研究了无死区三相六开关AC/DC双向变流器的新拓扑生成、控制策略及优化设计等关键问题，克服了桥式拓扑存在的桥臂直通问题和二极管反向恢复带来的损耗问题。主要研究内容有：研究了无死区三相六开关AC/DC双向变流器的拓扑生成方法，推导出了三种无死区三相六开关新型拓扑,比较了各拓扑的优缺点；提出了一种基于变流器电流总谐波畸变率THD模型的参数优化方法，通过建立高低频段变流器的THD估算模型，采用简约梯度算法，对有无死区变流器的滤波器参数进行了优化设计；从电路原理上探讨了各种电感磁集成方案分别在全周期和半周期两种工作模式下的可行性以及对电感体积和滤波效果的影响，通过对比得到了一种较好的磁集成方案；分析了双buck/双boost电路在半周期工作模式下电流过零畸变产生的原因，针对该问题，提出了基于纹波电流负反馈、调制波补偿和重复控制的三种改进型控制策略，均能有效地抑制半周期控制下交流侧电流过零畸变的问题；针对现有锁相技术中锁相角易受非理想电网电压影响且计算较为复杂的问题，提出了一种基于相角给定和坐标变换的无锁相SVPWM控制方法及在此方法下的基于无功功率负反馈的频率跟踪方法，提高了变流器对非理想电网的适应性；此外，还研究了基于磁芯损耗等效阻尼的无阻尼磁损式LCL滤波器下的变流器控制器设计方法；针对起动冲击电流大的问题，提出了高通滤波负反馈控制起动策略，较好地抑制了电流冲击问题，实现了缓起动和整流逆变双向平滑切换。本项目的研究为构成高可靠、高效率、高功率密度的无死区三相AC/DC双向变流器奠定了理论和应用基础。