【作者】 武琳；

【导师】 刘志刚；

【作者基本信息】 北京交通大学 ， 电气工程， 2014， 博士

【摘要】 电力电子变压器(Power electronic transformer, PET)是一种采用电力电子器件和高频变压器,通过电力电子变换技术实现电能变换的新型智能化变压器。电力电子变压器除了具有传统变压器的功能外,还具备功率密度高、可控性好、兼容性强、智能化的特点,可望在未来智能电网、机车牵引、新能源发电等场合得到推广使用。本文分别以基于独立铁芯和共用铁芯变压器的两种级联型电力电子变压器为研究对象,从理论分析、计算机仿真和实验验证三个方面深入研究了这两类级联型电力电子变压器的控制策略。首先,建立了LC谐振式和无LC谐振式两种DC-DC变换器的数学模型,并推导了其传递功率表达式,系统性地分析了原副边电压相位角的差、开关角频率、谐振角频率对双向DC-DC变换器功率传递的影响。在此基础上,研究和提出了双向DC-DC变换器的功率控制策略。仿真和实验结果验证了理论分析的正确性和控制策略的有效性。其次,针对电力电子变压器输入侧级联H桥的直流电容在传统的电压均衡控制策略下,功率器件开关频率过高的问题,提出了一种改进的直流电容电压平衡控制策略。仿真与实验结果表明,该控制策略在没有显著增加直流电容电压纹波的前提下,能够减小H桥单元在切入、切出、PWM调制三种状态之间的切换次数,从而减少开关器件的动作次数,降低开关器件的开关频率。再次,针对基于独立铁芯高频变压器的级联型电力电子变压器,其DC-DC变换器输出并联时的功率不均衡问题,提出了基于功率反馈的DC-DC变换器输出并联功率均衡控制策略。仿真和实验结果表明,基于功率反馈的输出并联功率均衡控制策略,能够避免因并联变换器参数变化引起的DC-DC变换器功率不均衡问题,验证了所提出控制策略有效性。最后,针对基于共铁芯多绕组变压器的级联型电力电子变压器的多绕组变压器绕组之间功率耦合现象,建立了其共铁芯多绕组变压器的数学模型,推导出共铁芯多绕组变压器的传递功率表达式,并深入分析了这类变压器的功率传递关系。分析结果表明,共铁芯多绕组变压器的每个绕组功率是该绕组与其它绕组电压相角差的非线性函数,各绕组功率之间存在着较强的非线性耦合。在此基础上,针对该类拓扑的DC-DC变换器输出并联时的功率不均衡问题,提出了一种基于功率反馈+功率前馈的功率均衡控制策略,仿真和实验结果表明,该控制策略在变换器参数变化时,能够实现DC-DC变换器输出并联功率均衡的控制目标。更多还原

【Abstract】 Power electronic transformer (PET) is combined with power electronic devices and high-frequency transformer. This kind of power electronic converter could achieve but not limit to traditional transformer functions. As a novel power electronic device, PET is expected in occasions such as future smart grid, railway traction, new energy power generation, etc. In this paper, individual and coupling core high-frequency transformer-isolation cascaded power electronic transformers are taken as research objects. The research works include theoretical analyses, computer simulations, and experimental verifications.Firstly, mathematical models of LC resonant and non-resonant DC-DC converter are established, power transmission expression are derived. The effect of voltage phase angle difference, switching angular frequency, resonance angular frequency on the power transmission characteristic is systematic analyzed. Based on the analysis of the power transmission characteristic, a power control strategy is research and proposed. The correctness of the proposed theory and control strategy is verified through simulation and measured results.Secondly, based on the deep analysis of the voltage imbalance of DC capacitor in the cascade H-bridge PWM rectifier, an optimized DC capacitor voltage balancing control strategy is proposed. Simulation and experimental results show that the proposed control method could reduce the switching frequency of the switching device through decrease the switching states of H-bridge.Thirdly, based on the deep analysis of power balance of DC-DC converter parallel output in the individual high-frequency transformer, a power balance control based on power feedback of DC-DC converter parallel output is proposed. Simulation and measured results show that the proposed power balance control strategy could avoid the power imbalance due to the parameter variation.Finally, the mathematical model of multi-winding transformer is established and the power transmission expression is derived. Based on the deep analysis of the power transmission characteristic, a power balance control strategy utilizing power feedback+power forward is proposed. Simulation and measured results show that the proposed power balance control strategy could still achieve power balance even if the parameter variations.更多还原