【作者】 王莉；

【导师】 周娟；

【作者基本信息】 中国矿业大学 ， 电气工程， 2022， 硕士

【摘要】 可再生能源不能持续稳定地为电网输送能量,影响电网正常运行,将新能源发电设备、超级电容器等储能设备及电网构成直流微电网,可有效解决新能源带来的不稳定问题。双有源桥(Dual Active Bridge,DAB)变换器具有高功率密度、电气隔离、能量双向流动等优点,便于实现模块化,被广泛应用于大功率场合,成为近年来的研究热点。本文主要对单体DAB变换器辅助电感的电流应力优化控制策略、多DAB子模块按照输入并联输出串联(Input Parallel Output Series,IPOS)方式构成IPOS-DAB变换器输出电压均衡控制策略展开研究。本文在分析DAB变换器在单移相控制时不同模式下运行状态的基础上,推导不同电压传输比时传输功率及辅助电感的电流应力特性,指出当输入电压不匹配输出电压时,单移相控制的辅助电感的电流应力会增大,损耗会增加,不利于变换器的安全经济运行。为使变换器高效运行,应减小辅助电感的电流应力。本文详细分析了扩展移相控制及双重移相控制在不同工作模式下的运行状态、传输功率和辅助电感的电流应力特性;给出电压传输比k≠1时两种控制方式下的辅助电感的电流应力优化控制策略,以辅助电感的电流应力最小为优化目标,根据模式约束条件及传输功率特性得到可行域,在可行域内求取最优解,推导出全功率范围内的最优移相比组合。通过对比发现,当k≠1时采用优化控制策略的辅助电感的电流应力较单移相控制时辅助电感的电流应力明显降低。大功率应用场合下,需将低压直流微网并入中压直流配电网,DAB变换器可以按照输入并联输出串联的结构构成IPOS-DAB变换器,但当模块间参数存在差异时,各模块的输出电压不均衡,影响变换器的稳定运行。本文以各模块输出电压均衡和IPOS-DAB变换器输出电压稳定为控制目标,推导了IPOS-DAB变换器的小信号模型,分析了输出均压控制策略解耦控制的条件,使输出均压环与输出电压环互相独立,并根据系统参数设计控制器参数,实现各模块的输出电压均衡。设计和搭建了一个100W的DAB变换器实验平台,利用此平台验证了本文中采用的电流应力优化控制策略以及IPOS-DAB变换器的输出均压控制策略的可行性与有效性,实验结果表明:在电压传输比k≠1时,辅助电感的电流应力优化控制策略能够明显降低电流应力,提升效率;输出均压控制策略在系统模块参数存在差异时,各模块间输出电压仍能保持均衡,且具有良好的动态性能。更多还原

【Abstract】 Renewable energy cannot continuously and stably transmit energy to the power grid,which affects the normal operation of the power grid.The new energy power generation equipment,supercapacitors and other energy storage equipment and the power grid form a DC microgrid,which can effectively solve the instability problem caused by new energy.Dual Active Bridge(DAB)converters have the advantages of high power density,electrical isolation,bidirectional energy flow,etc.,and are easy to achieve modularization.They are widely used in high-power applications and have become a research hotspot in recent years.This thesis mainly studies the current stress optimization control strategy of the auxiliary inductance of the single DAB converter,and the multi-DAB sub-module according to the input parallel output series(IPOS)method to form the output voltage balance control strategy of the IPOS-DAB converter.In this thesis,on the basis of analyzing the operating states of the DAB converter in different modes of single-phase-shift control,the current stress characteristics of the transmission power and auxiliary inductors under different voltage transfer ratios are deduced,and it is pointed out that when the input voltage does not match the output voltage,the single-phase-shift control,the current stress of the controlled auxiliary inductor will increase,and the loss will increase,which is not conducive to the safe and economical operation of the converter.For efficient operation of the converter,the current stress of the auxiliary inductor should be reduced.In this thesis,the operation state,transmission power and current stress characteristics of auxiliary inductance under different operating modes of extended phase-shift control and dual phase-shift control are analyzed in detail.The current stress optimization control strategy takes the minimum current stress of the auxiliary inductor as the optimization goal,obtains the feasible region according to the mode constraints and transmission power characteristics,obtains the optimal solution in the feasible region,and derives the optimal shift ratio in the full power range.combination.By comparison,it is found that when k≠1,the current stress of the auxiliary inductor using the optimal control strategy is significantly lower than that of the auxiliary inductor when the single phase-shift control is used.In high-power applications,the low-voltage DC microgrid needs to be merged into the medium-voltage DC distribution network.The DAB converter can form an IPOS-DAB converter according to the structure of input in parallel and output in series.However,when there are differences in parameters between modules,each module The output voltage is unbalanced,which affects the stable operation of the converter.Taking the output voltage balance of each module and the output voltage stability of the IPOS-DAB converter as the control objectives,the small-signal model of the IPOS-DAB converter is deduced,and the conditions for the decoupling control of the output voltage equalization control strategy are analyzed,so that the output voltage equalization loop It is independent of the output voltage loop,and the controller parameters are designed according to the system parameters to realize the output voltage balance of each module.A 100 W DAB converter experimental platform is designed and built.The platform is used to verify the feasibility and effectiveness of the current stress optimization control strategy and the output voltage equalization control strategy of the IPOS-DAB converter.The experimental results show that: When the voltage transfer ratio k≠1,the current stress optimization control strategy of the auxiliary inductor can significantly reduce the current stress and improve the efficiency;the output voltage equalization control strategy can keep the output voltage of each module balanced when the system module parameters are different,and has good dynamic performance.更多还原