E-field distribution analysis on three types of converter double valve in 800kV valve hall
Converter valve possesses the function of AC-DC voltage conversion and power transmission. It is an important device in the valve hall of UHVDC converter station. Since the corona discharge has a serious impact on the safe and stable operation of converter valve, it is necessary to analyze its surface electric field (E-field) distribution. In this paper, the structure characteristics of three typical double valve designs have been analyzed, which were respectively used in three high voltage (400-800kV) valve halls of one ±800kV UHVDC transmission project in China. Based on the project drawings, the equivalent model of each type of double valve with shielding structure was built with three-dimensional (3D) finite-element method (FEM) software ANSYS. Considering the interaction of double valves in actual valve hall, three double valve FEM models of same type in one hall, which formed the upper 6-pulse bridge in the 12-pulse converter unit, were built for the analysis of E-field distribution. Due to the hybrid AC-DC operating voltage, the transient E-field analysis with discrete loading voltage waveforms was adopted in these models. After calculation, the E-field distribution characteristic of different double valve types were summarized and compared under the normal operating condition. The results showed that the surface E-field strength on the shielding structure of all the double valves was lower than the critical value of corona inception and could meet the project requirements. This research could provide valuable references for shielding structure design and optimization of converter valve in the UHVDC transmission project.
Influence of Aluminum Foil and External Conductor on the Temperature Distribution of RIP Condenser Converter Transformer Bushings
With the increase of capacity, it's imperative to research about the 3-D temperature distribution regularity of transformer converter bushings. However, the influence of aluminum foil plates and heat generation power of external conductor on the temperature distribution of bushings has usually been neglected. In this paper, using the computational fluid dynamics (CFD) and finite element method (FEM) analysis method, the 3-D temperature distribution of the converter transformer bushing will be simulated according to the actual operating environment by considering the effect of the aluminum foil plates and the heat generation of the external conductor. The research indicates that the aluminum foil plates have little influence to the temperature distribution of RIP bushings. The thickness of external conductor should be reduced as much as possible, and try to choose materials with larger resistivity to reduce alternating eddy current loss of the external conductor and improve the bushing temperature distribution.
Simulation Analysis on Conducted EMD Caused by Valves in $\pm$ 800 kV UHVDC Converter Station
Wideband frequency electromagnetic (EM) noise generated during the turn-on and turn-off processes of thyristor valves in converter stations is conducted along the primary circuitry, and may interfere with secondary systems. The EM interference (EMI) problem in a plusmn800 kV ultra-HVDC converter station is an important issue that should be studied carefully in the design stage. A method to analyze the conducted EM disturbance (EMD) based on time-domain wideband circuit simulation is proposed here, which is verified through the field test results of a plusmn500 kV converter station. Models of major equipment are described. The EMD levels of a plusmn800 kV converter station, which is currently being planned and built in China, are calculated, and compared with those of a plusmn500 kV converter station.