Research On Transient Voltage Balancing Strategies About Series-connected Seimconductors

With the emerging of the energy crisis,AC transmission network can not meet the demand of social development.HVDC transmission is developing in a fast way,and it promotes the study on the DC circuit breaker.The DC circuit breaker is realized by the series-connected semiconductors.This dissertation focuses on the technology of dynamic voltage balancing of series-connected semiconductors.This dissertation is about judging the stabilization of the series-connected semiconductors,studying the dynamic performance,designing a power supplier for series-connected semiconductors and keeping the voltage balancing between switches in circuit and controller.All the mentioned work is implemented in a circuit model,which can guarantee the voltage balance between the power semiconductors,and tested in a 1000 V platform.With a equivalent circuit modeling,this dissertation establishes a state matrix for the series-connected semiconductors,and judges the stability by the matrix’s latent root.With the help of the theory,the dissertation calculates a proper value for series-connected semiconductors’ gate resistance value,based on MOSFET 20N60.A passive voltage balancing strategy is studied in the dissertation,which focuses on the effects to the circuit and the theory to making the voltage balance.In the study,a power supplier is designed and created,which can meet the series-connected semiconductors’ power supply demand.It is made up of a inverter,which may produce 6 A/70 k Hz sinusoidal current,and a linear voltage regulator.A theory about the two grade Γ-type filter is given in the dissertation.Based on that the inverter may keep the circuit working in a economical way and provide high isolation rating.It shows a good performance in the simulation.The circuit may provide a 5 V power supply.All the designation is implemented in the model.In the area of controlling semiconductors,the research focuses on the delay control,with a circuit to control and monitor the circuit’s performance,a control strategy is programmed.With the help of state machine control strategy,the FPGA is used to generate precise control signals.All the mentioned study is tested in a platform,which can supply 1000 V voltage.The series switches may open within 100 ns under the test condition with the dynamic voltage balance.