Research On Operational Test Methods Of Hybrid HVDC Circuit Breaker

Hybrid high-voltage direct current circuit breakers,as a new type of high-end power equipment in the field of power electronics,have different working principles and operating conditions from traditional AC circuit breakers or DC circuit breakers in the low-and medium-voltage applications.Until now,international or national standards of hybrid HVDC circuit breakers have not be referenced and electrical tests have not yet been conducted.In order to verify the validity of the hybrid HVDC circuit breaker design and accurately reflect the electrical,thermal and mechanical processes of the circuit breaker,it is imminent to carry out the research on the hybrid HVDC circuit breaker operational test method.Based on the study of the relevant theory of DC circuit breaker operation test,this paper analyzed the operation characteristics and stress characteristics of hybrid HVDC circuit breakers.Furthermore,based on the circuit breaker topology and stress parameters,a mathematical model of the system-level and device-level of the hybrid HVDC circuit breaker was established.The stress characteristics and its influence factors of the millisecond-level breaking process and the microsecond-level commutation process were studied,which demonstrated the weak coupling between the stress of the complete machine and the stress of the component is presented.Then,according to the stress characteristics and mathematical research conclusions,a complete set of hybrid HVDC circuit breaker operational test program was proposed,and the breaking test method was discussed in detail.The results of the test conducted in accordance with the test program verified the accuracy of simulation circuit and mathematical analysis.Finally,an equivalence evaluation method for hybrid high-voltage circuit breaker operation test was established.This paper analyzed the principle of energy termination and absorption function in hybrid HVDC circuit breakers based on hybrid HVDC circuit breaker functional materials,hybrid HVDC circuit breaker key components and hybrid HVDC breaker circuit topology.Based on it.the physical basis for the two-characteristic evaluation of hybrid HVDC breakers was proposed,which laid the foundation for the operational test research for hybrid HVDC breakers.This paper studied the stress characteristics both of the millisecond overall breaking process and the microsecond commutation process of the hybrid HVDC circuit breaker in detail based on the circuit breaker topology and the analysis of the breaking operation,and discussed the two time dimensions connection between the two kinds of' transient processes.The interrelationships demonstration was aimed to extract the millisecond-level breaking process and the microsecond-level commutation process stress characteristics and influencing factors.This paper built a PSCAD/EMTDC system-level digital simulation circuit and a device-level digital simulation circuit for hybrid HVDC circuit breakers.It verified the correlation between millisecond-level overall breaking stress and microsecond-level commutation stress in hybrid HVDC breakers,and could be used for hybrid HVDC breaker and operational test unified modeling.This paper proposed a hybrid HVDC circuit breaker operational test framework,proposed three breaking test methods based on LC oscillation power supply,a small-capacitance constant-voltage source,and a large-inductance constant-current source.Based on that,this paper constructed three kinds of breaking test scheme including a single source test,a dual-source synthesis test and a three-source synthesis.In addition,hybrid HVDC circuit breaker operational test equipment was built in the laboratory.The complete 200kV hybrid HVDC circuit breaker test,component test and 500kV hybrid HVDC circuit breaker reclosing test were successfully completed.This paper extracted the key stresses of the equivalence evaluation principles for hybrid HVDC circuit breaker operational test,which is used for building a hybrid HVDC circuit breaker operational test suitable for practical MMC-HVDC application.This paper established an equivalence evaluation method derived from dual-level stress concept based on both of whole machine and its core components,which was able to correctly evaluate equivalence of the type test.The conclusions of this paper can guide the design of the hybrid HVDC circuit breaker electrical structure and test system,guide the design and verification of the circuit breaker operational test device,and assist the promotion and application of the circuit breaker engineering.