Research On High Performance Control Strategy Of High-power LLC Resonant Converter

With the continuous deterioration of the global natural environment,mankind is currently facing an increasingly serious energy and climate warming crisis.Therefore,vigorously developing new energy has become an important way to solve the energy crisis.The vigorous development of electric vehicles has become a consensus among countries around the world.Fast and safe charging facilities are important conditions for the promotion and application of electric vehicles,and also a key factor restricting the further development of the market.At present,the common charging facilities in the market are mostly AC/DC and DC/DC two-stage structures.Among them,the rear stage DC/DC converter is directly connected to the power battery of electric vehicles,which has a significant impact on the performance and safety of DC charging equipment.Among numerous DC/DC topologies,LLC resonant converters are widely used in charging equipment due to their excellent characteristics such as front and rear isolation,high power density,and wide soft switching range.However,the complex and ever-changing operating conditions make the converter face many disturbances during operation,which can seriously affect the performance of the converter and even disrupt system stability.In addition,with the increasing demand for high-power DC converters,achieving modular parallel connection of LLC resonant converters and improving the overall power level is also a current research hotspot.Therefore,this article takes this as the research object and proposes a high-performance control strategy for high-power LLC resonant converters,which improves the dynamic response performance and anti-interference performance of the system,avoids the current imbalance problem when its multiphase modular interleaving is connected in parallel,and can achieve a significant increase in the power level of the entire machine.The main research results of this article are as follows:This paper proposes an integral backstepping control strategy for LLC resonant converters to address various disturbance issues during operation.Firstly,a reduced order mathematical model of the system was derived and a backstepping controller was designed.Furthermore,in response to the shortcomings of the backstepping controller’s wide range voltage regulation ability,after analyzing the gain error between the reduced order mathematical model and the higher-order model,an integral backstepping controller for LLC resonant converter was designed by introducing an integral link.The system stability was demonstrated based on the Lyapunov stability theorem.Compared to traditional backstepping control and PI control,the designed integral backstepping controller can effectively compensate for the modeling error of the reduced order mathematical model,achieve wide range voltage regulation without static error,and effectively improve the dynamic response performance and anti-interference performance of the system.This paper proposes a staggered parallel current sharing control strategy based on phase-shifting control to address the issue of unbalanced current in multiphase modular parallel connections.Firstly,an in-depth analysis of its interleaved parallel topology was conducted,and the "non-uniformity" index was defined to reveal the reasons for the occurrence of system non-uniformity,and the impact of different resonance parameters on the current sharing effect was analyzed in detail.On this basis,new characterization variables were selected and a phase shift control based interleaved parallel current sharing control strategy was proposed.This control strategy is simple and easy to implement,capable of achieving multiple intersecting faults in parallel,achieving current balance under different working conditions,effectively reducing output current ripple,and has good dynamic characteristics.Finally,a dSPACE semi physical experimental platform was built,and output voltage response experiments,interleaved parallel current sharing control experiments,and system anti-interference experiments were completed.The experiments proved the feasibility and superiority of the control strategy.