Research On The MVU Test Method And Equipment Of HVDC Valve

In 2015,the State Grid Corporation of China put forward the concept of global energy Internet,including intercontinental energy interconnection and clean energy transmission such as wind and solar energy from the arctic and equator.This relies heavily on large-capacity,long-distance transmission technology.At the same time,to solve the reverse distribution conflict of China's power generation and electricity load,West-East electricity transmission strategy is setup.Those rely heavily on large-capacity and long-distance power transmission technology.UHVDC transmission technology,with low investment,long transmission distance and huge capacity will become an inevitable choice.As the "heart" of a HVDC transmission system,the DC converter valve with high reliability is a key factor for ensuring the long-term operation of the transmission system.So it is necessary to carry out comprehensive test work on the valve to test the rationality of its design and the correctness of the assembly before commissioning.IEC60700 standard just provide general requirement about converter valve tests,no and is not sufficient for test conduction.Based on the test of the Brazilian beautiful mountain I ± 800kV and the Zhundong to Wannan ± 1100kV UHVDC transmission projects,test method about the multi-valve tests which have higher test voltage was researched in this paper.Firstly,the overvoltage stresses such as DC voltage,switching and lightning impulse were analyzed,especially in some extreme operation modes such as short circuit and load rejection.Then the specific requirements of the multi-valve test are extracted,based on IEC60700 standard and the tender technical specifications about multi-valve test,laying the foundation for the test method research and test equipment design.Considering the actual situation of power system,the feasibility of equivalent load method is analyzed,and a new high-equivalent load topology is proposed for the first time,which solves the problem of simulation for time-varying characteristic of saturation reactors.Besides,the isolated R-C protection system was designed to meet the requirements of the impulse source and low-voltage energy source protection for some test valve which need energization.DC voltage and impulse voltage test equipment and broadband equivalent load for multi-valve tests are developed with reference to the test parameters of several converter valves of different voltage level worldwide.Especially,the electrical and structural design of the equivalent load is introduced,and the effect of the stray capacitance on voltage distribution between the series-connected valve and the equivalent load is solved by using the capacitor compensation voltage measurement method.Finally,the multi-valve test equipment was applied in the above two UHVDC projects.And the test were successfully completed,corresponding test data and waveform were obtained,verifying the rationality and correctness of the multi-valve test methods and equipment.