Research On Optimization Of Active Voltage Control For Press-pack IGBT In Series Connection

With the progress and development of power electronics technology, flexible HVDC show its unique advantages in resolving long-distance, large-capacity transmission, new energy distributed power access and problem large mixing AC and DC power grid will face. Flexible HVDC system consist voltage source converter based on insulated gate bipolar transistor (IGBT) and advanced control strategies to realize efficient power transfer.Limited by the capacity of the IGBT, a plurality of IGBT devices in series or modules is usually performed to address the problem of low voltage of single IGBT. Topology of flexible DC voltage source converter develop from the two-level technology into the mainstream of modular multi-level technology. While with further improvement of voltage level, IGBT in series with modular multi-combined with the level of technology would be flexible for high voltage direct current transmission direction of development. Recently the ABB flexible HVDC project put into operation using the technology route. Therefore the technology of IGBT in series has a very high value.Press-pack IGBT holds a very significant competitive advantage in application in DC power of IGBT in series compared to the welded IGBT with a compact structure,short-circuit failure mode, double-sided heat dissipation, etc. This paper relies on State Grid Smart Grid Institute of Technology project " Research of key technology and protection in dedicated drive of 2500V/1200A Press-pack IGBT ". Mechanism and control measures of voltage unbalance in Press-pack IGBT in series were studied, especially on the active voltage control technology research and optimization.The basic characteristics of IGBT and FRD are described, focusing on the static and dynamic analysis IGBT voltage unbalance mechanism; secondly the active voltage control principle for IGBT in series is analyzed, and reference voltage optimization method is given. The correctness of optimization strategy is verified through multiple sets of simulation. Based on new AVC dynamic voltage-sharing circuits, field-programmable gate array (FPGA) device and hardware description language were used to design the drive signal distribution circuit, so as to realize each unit precision delay control in the process of switch- on and switch-off and to realize the logic synthesized protection.Finally a inverter experimental platform based on the Press-pack IGBT in series is built to verify the correctness of active voltage control optimization strategy. The research of high-power IGBT voltage control on flexible HVDC application of IGBT in series results has a guiding significance for the development of actual project.