Study On The Temporal And Spatial Characteristics Of HVDC Commutation Failure In Complex Power Grid

With the rapid development of our economy, the project of "Power Transmission from West to East" and Nation-wide Interconnection are of full implementation. With its obvious technical and economic advantages in long-distance transmission and cross-regional interconnection, HVDC transmission has become an important framework of interconnected power grid in China, and AC/DC interconnected power grid pattern has been formed in China, especially the "Eight AC Eight DC" power system in South China Power Grid is the most complex. For access to a large number of HCDC system, its working principle, operation mode, electrical characteristics of the fault are of great differences from traditional AC power system. As a result, there are series of theoretical and engineering challenges need to be solved, of which the commutation failure is the most prominent issues and has been a hot-spot in theory and engineering in recent years.Researches on commutation failure mechanism, influence factors, prevention and control measures have had a lot of achievements, but they are mainly based on the analysis of DC inverter and only consider the influence of asymmetric fault on commutation voltage phase. Research about the influence of fault on converter bus voltage and the influence of symmetric fault on commutation voltage phase is not enough when fault point extrapolated from the inverter station to complex large power grid.Aiming at this problem, this paper analyzed the main factors that influence the commutation failure in complex power grid first, and then established a model which contains detailed DC system and can reflect the characteristics of AC power grid. With the model, temporal and spatial correlation properties between AC fault and communication failure of DC system are studied when extrapolated from the inverter station to complex large power grid. Among them, the temporal correlation characteristic mainly refers to the difference of electrical time, which corresponding to voltage phase of the fault point; and the spatial correlation characteristic refers to the difference of electrical distance, which corresponding to space position of the fault point. Then analyzed the characteristics of AC symmetrical fault in complex power grid from a theoretical point of view, and considered the influence of voltage phase of the fault point and the DC inverter into account for the first time. From the steady state voltage phase difference between fault point and DC inverter, analyzed the influence of AC fault on DC converter’s voltage amplitude and voltage phase. At last, using the PSCAD/EMTDC model based on a FD operation mode of China Southern Power Grid, starting from the three aspects of different fault locations, different DC systems and different operation conditions, to analyze the main factors that influence DC converter’s voltage amplitude and voltage phase, and get the temporal and spatial characteristics of DC system’s commutation failure in complex power grid.This work is supported by the the National High Technology Research and Development Program(“863” Program) of China(No. 2012AA050209). Some of the research results have been applied to the operation of actual HVDC systems, obtaining great economic and social benefit.