Research On Converter Topology And Control Strategy Of Offshore Wind Power DC-collected Wind Turbines

In order to achieve the great strategic goals of "carbon peak" and "carbon neutrality",the use of new energy power generation technology has become the most effective means to reduce carbon dioxide emissions in my country.Offshore wind power generation,as an important part of new energy power generation technology,has also ushered in With the increasing installed capacity of offshore wind power,it is very important to study efficient ways of gathering offshore wind power.Among them,compared with AC collection,DC collection adopts high-frequency transformer instead of using largevolume power frequency AC transformer,which reduces system transmission loss and cost investment.DC/DC converter is the key in DC collection fan unit Equipment has become the focus of research and development in recent years.By combining multiple DC/DC converters into a system structure with parallel input and serial output to meet the high-gain and large-capacity requirements of DC/DC converters in offshore wind power DC collection wind turbines,Dual Active Bridge(DAB)is selected as the sub-module converter.in order to ensure the normal operation of the converter in the modular combination,the control strategy of the output voltage equalization of the converter system with input parallel and output serial is carried out indepth research.In this paper,the topology of the dual active bridge converter is first studied,its working principle and transmission power characteristics are deeply analyzed,and the relationship between different voltage ratios and backflow power,inductor current stress and soft switching conditions is derived and calculated.The theoretical analysis and verification is carried out through simulation.The simulation results show that when the voltage ratio of the dual active bridge converter does not match,the backflow power and inductor current stress will increase and the soft switching range will be reduced.Then analyze the main factors affecting the output voltage equalization of the dual active bridge converter system with input parallel connection and output series connection,adopt the droop control strategy of input current sharing,aim at the static deviation problem existing in the droop control strategy of traditional input current sharing,propose a Improve the droop control strategy of input current sharing,analyze its stability by building a small signal model of the IPOS-DAB converter system,and conduct simulation analysis on the IPOS-DAB converter system,the simulation results verify the droop of the improved input current sharing The stability and effectiveness of the control strategy.Finally,an experimental prototype of the IPOS-DAB converter system was built,and the hardware and software of the experimental prototype were designed respectively,and the theoretical analysis of the DAB converter and the droop control strategy for improving the input current sharing were verified.The experimental results verified the theory Analytical correctness and effectiveness of improved control strategies.