Research On IGBT Series Voltage Equalization Control Strategy

In order to effectively isolate power grid faults and improve transmission efficiency,high-voltage direct current transmission(HVDC)technology has been used in power transmission systems.Insulated gate bipolar transistors(IGBTs)combine the driving advantages of MOSFETs and BJT conduction The advantages have been widely used in the field of high-voltage and high-power conversion.However,due to the limitations of semiconductor technology and technology,the voltage and current capacity of a single IGBT cannot meet the requirements of high-voltage and high-power conversion.The direct series and parallel connection of IGBT devices is to improve the power electronic conversion device.The most direct and effective method of pressure level and capacity.In actual engineering,due to the differences in the parameters of the IGBT itself,direct series connection often produces voltage imbalance.When this voltage imbalance reaches a certain level,it may cause damage to the IGBT device.Static and dynamic voltage distribution affect the stable operation of the device At the core,therefore,the research of IGBT dynamic voltage equalization has very important practical significance and application value.This article first discusses the background of this study,introduces the application requirements of IGBT devices under high voltage conditions,summarizes and summarizes the IGBT modeling methods,reviews the domestic and foreign research status of insulated gate bipolar transistor series technology,analyzes and summarizes the current There are advantages and disadvantages of the IGBT device series voltage equalization method.Through the analysis of the basic structure,working principle and basic parameters of IGBT,the relevant theoretical basis has been established for the research of series IGBT voltage equalization.Aiming at the static working process and dynamic working process of IGBT,the voltage imbalance at each stage in the dynamic working process is analyzed,and the main influencing factors of voltage imbalance at each stage are determined by formula derivation.In actual engineering applications,when the pulse difference of the IGBT device does not exceed a certain range when it is turned on,voltage equalization is easy to achieve,and if effective measures are not taken when it is turned off,the voltage equalization of the IGBT device will be difficult to achieve.Therefore,this paper focuses on the strategy of controlling the IGBT devices in series at the turn-off time.Finally,through the theoretical formula derivation,and based on the simplified model of IGBT,through the experimental test and analysis of the operating characteristics of the insulated gate bipolar transistor,the relationship between the off-delay time and the on-time of the sampling circuit is found,and a method is proposed.When there are differences in the operation of series insulated gate bipolar transistors resulting in uneven voltage,the control strategy of dynamic voltageequalization can be realized by adjusting the turn-off delay(or lead)of each IGBT in real time.And through the data analysis of multiple experiments,the unique function relationship between the off delay time of the device and the on time of the sampling circuit is found.When the series IGBTs cause uneven voltage due to the difference of their own parameters,the IGBT can be adjusted in real time by control The gate drive realizes dynamic voltage equalization.The method is fast and stable,and its reliability and stability are verified through simulation and experiments.The experimental results show that the voltage-sharing control strategy in this paper can effectively reduce the voltage difference between the devices,obtain a better voltage-sharing effect,and make the system have better stability.