Research On Voltage Performance Improvement Methods And Applications Of High Voltage Semiconductor Switch Modules

Flexible HVDC has broad prospects for application in future power grids due to its flexible controllability and strong long-distance transmission capacity.Facing the problem of overcurrent fault traversal in flexible HVDC systems,it is necessary to equip DC circuit breakers to ensure the stable operation of the system.The high-voltage semiconductor switch modules technology that can achieve high DC current breaking is a common key technology for various types of hybrid DC circuit breakers.However,the effective voltage utilization of power electronic devices connected in series in current semiconductor switch modules is low,requiring a large number of cascades,greatly reducing the economic efficiency of semiconductor switch modules technology.This article aims to overcome the technical defects and cost issues of high-voltage semiconductor switch modules,and conducts in-depth research on the construction of strong nonlinear voltage limiting circuits,transient voltage spike suppression,and high capacity and efficient integration in high-voltage semiconductor switch modules.Ultimately,it effectively solves the problem of low voltage utilization in power electronic devices,The relevant achievements will be directly applied to the 30kV/10kA hybrid DC circuit breaker in the Xinjiang onshore wind power full DC power generation demonstration system.The main content is as follows:Firstly,in response to the problem of insufficient nonlinear capability in current pure MOV voltage limiting circuits,a composite voltage limiting circuit with strong nonlinear components connected in series with MOV is proposed.Two types of voltage limiting circuits,gap-MOV circuit and thyristor-MOV circuit,are specifically constructed.By utilizing the strong nonlinear characteristics of static high resistance and transient low resistance of gap and thyristor components,the decoupling of transient overvoltage and static working voltage of semiconductor switch modules is achieved.A modular series connection method and circuit parameter design method were further proposed,and a semiconductor switch modules testing platform was built.The experimental results showed that compared with pure MOV voltage limiting circuits,the static voltage utilization rate of semiconductor switch modules increased from 44.4%to 72%.Secondly,in response to the demand for suppressing turn-off voltage spikes and improving transient voltage utilization rate in semiconductor switch modules,an equivalent circuit model of semiconductor switch modules is established,revealing the coupling mechanism between circuit stray inductance,large capacity breaking capacity,turn-off voltage spikes,and transient voltage utilization rate.Propose a voltage spike suppression and transient voltage utilization improvement method based on low stray inductance design.Specifically,propose a "T" type low inductance layout design for single semiconductor switch modules modules and a buffer circuit integration design method for cascaded modules.A semiconductor switch modules testing platform was built,and the experimental results show that the peak voltage of the optimized semiconductor switch modules decreases by 40.9%,and the transient voltage utilization rate increases from 74.1%to 93.2%.Thirdly,in response to the reliable energy dissipation and overvoltage suppression requirements of large capacity semiconductor switch modules,a voltage limiting circuit integrated design method combining modular gap-MOV circuits and centralized thyristor-MOV circuits is proposed,leveraging the advantages of high cost performance of gaps and high surge capacity of thyristors.A semiconductor switch modules circuit model has been established,and a method for regulating switch performance under the influence of multiple parameters has been proposed.The decoupling of the energy dissipation and overvoltage suppression functions is achieved through the differentiation of volt-ampere characteristics between voltage-limiting circuits.The experimental results show that the effective discharge frequency of the gap is increased by more than 10 times,the voltage imbalance of the cascaded semiconductor switch modules is controlled within 5%,and the cost of the gaps and thyristors is reduced by 45%.Based on the above theoretical research results,a new compact hybrid DC circuit breaker scheme with ultra-high voltage utilization efficiency was designed for Xinjiang’s ±30kV onshore wind power full DC power generation demonstration system.A scaled prototype of the 10kV/10kA hybrid DC circuit breaker and key components such as power electronic switches,converter devices,isolation and energy supply systems,and fast mechanical switches were developed in the laboratory.The experimental results show that the 10kV hybrid DC circuit breaker can break 10kA current within 3ms while withstanding 13.1kV overvoltage.Especially,the required number of semiconductor switch modules cascades has decreased by 40%.greatly improving the technical and economic efficiency of the 30kV/10kA hybrid DC circuit breaker equipment used in engineering.At the same time,it can provide a technical foundation for other similar protective equipment using semiconductor switch modules.