Research On Circulating Current Analysis And Suppression Method Of Hybrid Parallel Hydrogen Production Power Supply

In recent years,traditional fossil fuels such as oil,coal,and natural gas are facing an increasingly depleted situation,which also brings environmental issues that cannot be ignored in the process of use.As a clean secondary energy that can be stored and transported for a long time,hydrogen energy can not only effectively alleviate the energy and environmental crisis,but also solve the problems of difficult absorption,intermittent and volatile power generation of new energy through electrolytic production and energy storage systems.As the core of the electrolytic hydrogen production system,the design and research of hydrogen production power supply is of great significance to ensure efficient hydrogen production efficiency.In addition,the topology of the hydrogen production power supply designed in this paper has a circulation problem between parallel converters.In order to reduce the impact of circulation,analysis and suppression of circulation is also crucial.In this paper,a hybrid parallel hydrogen generation power supply topology with isolation transformers is designed,which has the advantages of low cost,high power,and high current quality.Subsequently,the concept of topology design and topology functions that can improve the quality of AC and DC side currents are introduced.Then,a detailed mathematical modeling of each converter module in the topology is carried out,and a harmonic detection algorithm based on instantaneous reactive power theory and sliding average filtering theory is designed for the AC/DC side active power filter control system.Finally,a topology model is built on the PSIM simulation experimental platform to verify the proposed topology functions.Then,the circulation characteristics of a hybrid parallel hydrogen production power supply without isolation transformers are studied.Firstly,the mechanism of circulating current generation and its variation characteristics within the switching cycle and power frequency cycle are analyzed.Subsequently,an analysis method based on the equivalent loop of the circulating current is proposed,and based on the analysis of the switching period,the circulating current change rate and the maximum peak value of the circulating current under different switching states within the switching period are obtained.Then,in order to analyze the circulation characteristics within the power frequency period,an average model of the hydrogen production power supply is established.Based on the power frequency period analysis,the circulation change rate and the circulation peak value under different three-phase AC bus voltage levels within the power frequency period are obtained.Finally,the correctness of the circulation characteristics analysis is verified on the PSIM simulation experimental platform.Finally,the method of restraining circulating current in hybrid parallel hydrogen production power supply without isolation transformer is studied.Firstly,the passive suppression methods of circulating current are introduced and the suppression effects are compared.Based on the analysis of circulating current suppression mechanism,an active circulating current suppression method based on PWM rectifier side closed-loop control is proposed.However,due to the traditional PI regulator’s inability to achieve static error free control of zero sequence circulating current,a circulating current controller with a PI regulator and a QPR regulator is designed and its parameters are designed.Then,an active suppression method of circulating current based on closedloop control of PWM inverter side is proposed.Finally,the effectiveness of the circulation suppression method is verified on the PSIM simulation experimental platform.