Research On Parallel Connected IGBT Power Modules

Energy storage system is the key technology to support the development of smart grid, renewable energy access, distributed power generation, micro grid and electric vehicles. The research on large capacity applications of parallel connected IGBT power modules can provide technical support for IGBT power modules used in large capacity storage system.With the development of semiconductor technology, the current capability of single IGBT module offered by the most popular manufacturers has been greatly improved. Two methods are commonly used to increase power handling capacity when the system needs a further expansion of power supply:the selection of higher power level devices and a number of power devices in parallel. Nevertheless, the most economical approach at present stage is to operate multiple switching devices in parallel to increase the current capability, when taking into account the cost, the complexity of the power drive circuit. Due to the discreteness of device parameters, the asymmetry of driving circuit and power circuit when IGBT power modules operating in parallel, the current of each module can not be even. Therefore, the static and dynamic current imbalance must be carefully considered.The paper focuses on the research of factors affecting the static and dynamic current imbalance of parallel connected IGBT power modules and the methods to improve the uneven current. Firstly, the working principle and basic features of power IGBT are analyzed, including equivalent circuit, static characteristics and switching characteristics. Then, the factors affecting static and dynamic current imbalance of parallel connected IGBT power modules are studied by simulation and experiments. Finally, methods of de-rating, adding impedance and gate voltages control are used to improve the static current imbalance based on the foregoing analysis. Methods of de-rating and adjusting gate resistances are used to improve the dynamic current imbalance based on the foregoing analysis. Otherwise, a current sharing model during turn-on period of parallel connected IGBT power modules is proposed on the basis of parameterized IGBT model and single IGBT turn-on process, and the model is verified by experiments. Furthermore, a simple active gate control method is proposed based on the model, the compensation of delay time can be obtained directly by module testing without the need to measure the collector current.