Research On Topology And Control Of Micro Modular Energy Storage Converter

In order to promote the national development strategy of carbon peaking and carbon neutralization and speed up energy transformation,new energy is becoming the object of national vigorous development.However,renewable energy represented by photovoltaic and wind power is affected by light intensity and wind speed respectively,which has the disadvantages of intermittency,randomness and instability.New energy vehicles are limited by technical conditions,which have the disadvantages of short mileage and inaccurate estimation of residual power.Multilevel energy storage converter is widely used in photovoltaic,wind power and other new energy power generation systems because its output waveform has the characteristics of high equivalent switching frequency,low harmonic content,energy storage,simple and flexible control.In addition,it can also be used in the battery system of new energy vehicles for battery unit energy management,so as to improve the estimation accuracy of mileage and residual power,and alleviate the mileage anxiety of drivers.In order to alleviate the problems of the above multilevel converter in new energy power generation and new energy vehicles,such as high topology cost,complex equalization control,difficult new energy consumption,large voltage stress of power devices,difficult fault diagnosis and fault-tolerant control,a new modular multilevel energy storage converter topology,modulation strategy and other key technologies are proposed in this paper,A new capacity balancing strategy and a new fault diagnosis and fault-tolerant control strategy are proposed.The new modular multilevel energy storage converter proposed in this paper is composed of two completely symmetrical bridge arms,each of which is composed of multiple half bridge sub modules with energy storage batteries in series.Based on this topology,firstly,its equivalent circuit is introduced,the mathematical model is established,the working mode and its advantages over the existing multilevel converter topology are analyzed,a new dual carrier cross phase-shifting control strategy is adopted to realize the basic functions of the new converter topology,and the mathematical expression of dual Fourier transform of output voltage under dual carrier cross phase-shifting control is derived.For the new converter topology,the simulation model is built,the feasibility of control strategy under different modulation schemes and the dynamic performance of the system in the process of load dynamic switching are analyzed,and the hardware platform is built to verify the practicability and reliability of the new converter topology and its modulation strategy.Based on the energy storage sub module of the new topology,this paper proposes a new battery capacity equalization control strategy,introduces the working mode and operation flow chart of the equalization strategy,analyzes the current flow state of each energy storage sub module,reveals the working principle of the equalization strategy,and finally builds a simulation model to verify the feasibility of the battery capacity equalization strategy.In order to improve the practicability and reliability of the new modular multilevel energy storage converter system.This paper analyzes the fault diagnosis principle of the energy storage sub module of the converter,including the analysis of fault types and fault characteristics,and deduces the mathematical expression of the output voltage of the open circuit fault sub module.According to the above analysis,a fault diagnosis strategy for the open circuit fault of the switch is proposed and the open circuit fault diagnosis flow chart is drawn.Then,an innovative shortcircuit fault diagnosis strategy of interrupting the driving signal based on dual carrier cross phase-shifting modulation strategy is proposed,and the expression of the interruption time period of each driving signal is deduced.This strategy solves the problem of difficult and harmful short-circuit fault diagnosis of current converter topology,and puts forward faulttolerant control strategies for different fault types.Finally,the feasibility of the fault diagnosis strategy for the new multilevel converter is verified by building the simulation model and hardware platform.Finally,the hardware experimental platform is built,mainly including hardware circuit design and system software design.Among them,the design of hardware experimental platform includes three parts: main circuit design,driving circuit design and sampling circuit design;The system software design includes the whole process of model design,construction,parameter debugging and system operation of the experimental control model.The above experimental verification is completed by using the hardware platform.