Research On Hardware-in-the-Loop Real-Time Simulation Technology Of Multi-Port Power Electronic Transformer

Power electronic transformers have the characteristics of electrical isolation,power factor adjustment,small size,AC and DC voltage interfaces of different voltage levels,and convenient access to renewable energy.They have received extensive attention in smart grids and energy Internet.Aiming at the current proposed power electronic transformer topology and medium and high voltage intelligent distribution network,a power electronic transformer topology based on hybrid modular multilevel converter is proposed.The topology is composed of a hybrid sub-module MMC,isolated DAB converters with serial input and parallel output,and a low-voltage inverter.This thesis carries out the following research:First,the system structure and working principle of power electronic transformer are analyzed,and it divides the topology of power electronic transformer into several modules for targeted research,including hybrid MMC,isolated DAB converters with series input and parallel output,low-voltage inverters,and AC/DC load interfaces.Study its individual modulation and control principles.The preliminary digital simulation is carried out,which lays a good foundation for the whole research.Second,a 10 k V/DC±375V/AC380 V high and low voltage distribution network model and a simulation model of a multi-port power electronic transformer are built in the RT-lab simulator,and the virtual multi-port power electronic transformer is controlled by an FPGA-based controller.The RT-lab and the controller exchange data through SFP,realizing real-time hardware-in-the-loop simulation,and verifying the feasibility and reliability of the proposed topology and control strategy.For the future development of similar products,shorten the development cycle,improve work efficiency and reduce the development cost.Third,the multi-port power electronic transformers studied in this paper are applied in a practical demonstration project of China Southern Power Grid,which consists of four multi-port power electronic transformers.According to the design plan and on-site commissioning requirements of the demonstration project,an overall distribution network plan was built.Through this platform,the energy flow,operation mode,dynamic characteristics and fault characteristics of the power grid and core equipment were studied,and the entire system was verified through tests.The rationality of the network structure and control strategy minimizes the possibility of control and protection system defects being brought to the site,and provides comprehensive technical support for equipment development and engineering site equipment commissioning.