Research On Improving Breaking Capacity Of AC Solid State Circuit Breaker

In recent years,with the acceleration of China’s energy Internet construction and large-scale new energy grid connection,the problem of power system stability becomes more and more prominent.Based on the relationship between system stability failure and power Angle,this research group proposes a new power system stability control methodcommutation sequence technology.In technical requirements phase sequence circuit breaker has the device.the speed,switch time accurate,flow capacity and strong compression ability etc,therefore,by means of power semiconductor devices the advantage of fast switching speed,switch time accurate,based on the Insulated Gate Bipolar Transistor(Insulated Gate Bipolar Transistor,the IGBT)designed a new type of ac solid-state circuit breaker,and is committed to improve the breaking ability of circuit breaker and power levels.Focusing on solid state circuit breaker,this paper mainly completed the following work:(1)combining the forced commutation technology with the solid state circuit breaker,a forced converter type ac solid state circuit breaker is designed,which can effectively suppress the over-voltage of the breaker.Perceptual work hard in order to reduce IGBT off the impact of voltage,current,this article will first HVDC force converter technology application to the new type of circuit breaker,by changing flow reduce break-brake overvoltage,but at the same time,the study found that the traditional force converter technology lack of reasonable charge and discharge circuit and charging scheme,and h as lead to voltage of the IGBT mutation faults.For this reason,an improved forced converter circuit is designed,its working principle is analyzed,and its correctness and effectiveness are verified by PSpice platform simulation.Then the structure and working principle of the new circuit breaker are introduced in detail,and the design principle of the main parameters of the circuit breaker is studied.Finally,a prototype 110 kV/30 kA solid-state circuit breaker was built according to the design principle.The simulation data showed that the impulse voltage of the tripping gate was effectively suppressed,and it had good switching performance,which could basically meet the performance requirements of phase-change sequence technology for switching equipment.(2)the dynamic and static voltage unbalance mechanism of series IGBT is analyzed in detail,and a new type of dynamic voltage equalizing circuit is proposed to solve th e non-uniform voltage problem caused by the unsynchronization of driving voltage signals during the dynamic conduction or shutdown of series components.In order to improve the voltage resistance of the circuit breaker,it is a simple and effective method to use multiple IGBT components in series,while the direct use of IGBT components in series may cause the problem of unbalanced voltage distribution due to the inconsistence between the component parameters and the peripheral circuit parameters.For this reason,this article first analyzes the uneven series IGBT static and dynamic pressure mechanism,and on this basis,proposed a new type of dynamic equalizing circuit,by adjusting the driving signal of IGBT element dynamic conduction delay grid high level driver signal and dynamic shut off the grid of the low level driver signals,to reduce the degree of driving signals are not synchronized,so as to improve each element set emitter voltage dynamic consistency;Then,in order to verify the effectiveness and correctness of the designed voltage equalization circuit,IGBT series voltage equalization simulation was carried out on PSpice platform.The simulation results show that the new voltage equalization circuit effectively improves the voltage equalization degree in the dynamic process.(3)the dynamic and static current unbalance mechanism of parallel IGBT is analyzed in detail,and a new static non-uniform flow control strategy is designed to solve the nonuniform flow problem caused by the difference in on-state resistance of parallel components during static conduction.In order to improve the flow capacity of the circuit breaker,it is the simplest and most effective method to use multiple IGBT components in parallel,while the saturation voltage drop,drive voltage,and output impedance parameters are not consistent with the parameters of the peripheral circuit will lead to uneven distribution of parallel current.Therefore,this paper analyzes in detail the dynamic and static non-uniform flow mechanism of parallel IGBT and the corresponding current sharing technology,and proposes a new static non-uniform flow control strategy,which realizes the parallel non-uniform flow control by compensating the equivalent on-state resistance of each parallel branch with modulation resistance,and verifies the correctness and effectiveness of this strategy through simulation on PSpice platform.