Research On Power Control Strategy Of Hydrogen Production From New Energy Electrolysis Of Water

The production of hydrogen from new energy sources by electrolysis is an important way to achieve the local consumption of new energy sources and the production of green hydrogen.As an intermediate link between the new energy source and the PEM electrolyzer,the hydrogen production power supply needs to meet the fluctuating power consumption of the new energy source and adapt to the operating characteristics of the PEM electrolyzer.The paper proposes a modular hydrogen power supply scheme based on a three-phase staggered parallel LLC topology,and investigates the control strategy of single module hydrogen power supply and multi-module parallel connection,taking into account the requirements of the new energy generation scenario.The operating characteristics of the PEM electrolyser,as the load of the hydrogen production power supply,determine the control strategy of the hydrogen production power supply.Considering the relationship between the port voltage,hydrogen production efficiency,hydrogen production rate,reaction temperature and electrolysis current density of the PEM electrolyser,the electrical characteristics and efficiency characteristics of the PEM electrolyser are analysed separately,and a PEM multi-input and multi-output mathematical model is established.The PEM electrolyser requires a high current and low ripple output for hydrogen production,which requires electrical isolation.Based on this,this paper proposes a three-phase interleaved parallel LLC hydrogen power supply solution.In order to adapt to the different states of the PEM electrolyser and the fluctuating power consumption of the new energy side,a small-signal mathematical model of the hydrogen power supply is established,a single-module hydrogen power supply control strategy of start-up control,constant voltage control and current control is proposed,and the control strategy switching rules of the hydrogen power supply in response to the hydrogen side and the new energy side are designed.The excellent performance of the hydrogen power supply in terms of low output current ripple,soft switching and the correctness of the control strategy design are verified through simulation.In order to achieve high-power hydrogen production in new energy scenarios and to solve the problem of limited output power of individual power modules,a modular multi-unit parallel hydrogen production scheme is designed.When the voltage control strategy is adopted in parallel,the uneven current between modules caused by the inconsistency of actual circuit parameters is analysed.The magnitude of the influence of the deviation of resonant inductance,resonant capacitance and excitation inductance parameters on the uneven current is analysed,the relationship between the output impedance and the resonance parameters of the main circuit is derived,and a sagging current equalisation control strategy is designed for the parallel connection of hydrogen production power modules to equalise the output current between modules.When the current control strategy is adopted in parallel,the total electrolytic current command is calculated first by the power outer loop to meet the new energy consumption demand;when the hydrogen production demand is met,the electrolytic current command value corresponding to the maximum efficiency point is searched first,and the total current command obtained is distributed equally among the modules.In order to verify the proposed hydrogen production power supply scheme and control strategy,the calculation of magnetic devices for the main circuit,the selection of switching devices and the design of hardware circuits were first carried out,and then two 6k W modular experimental prototypes were built.The experiments on soft-switching,output current ripple and dynamic characteristics were carried out for the single unit of the hydrogen power supply,while the experiments on the parallel current equalisation control strategy and the load mutation were carried out for the multiple units.The experimental results show that the modular hydrogen power supply solution designed in this paper has high efficiency,low ripple and high power,and is suitable for new energy hydrogen production scenarios.