| DC transformer has an important role in metering and rely protection in DC system. Its accuracy and anti-interference capability is necessary for the security of DC system. Nowadays, the application of HVDC becomes more popular specially in long-distance and huge power condition. However, the PQ events in DC system lack attention and few research focus on characteristics of DC transformer in PQ events.This treatise was ground on the research “Study on Metrological characteristics and Detection Technology of DC Transformer”. An zero-flux DC transformer applied in Longquan converter station was selected for the study. Different zero-flux transformers was analyzed and several major zero-flux detecting principles was introduced.A comprehensive analysis of actual waveform in several key converter stations were developed including Gezhouba, Longquan and Jianglin Station in Hubei province. Then different PQ events in DC system was classified according to PQ events in AC system. Several typical DC PQ events waveforms and its main parameters were obtained, which provides input data for later simulation. It is conformed that oscillation, pulse and ripple are the three main PQ events in DC system.Transform function and simulink model of DC transformer were established. Transform function model were set up according to the transform function of its different parts, which could reflect dynamic process of transformer. And Simulink model was closer to actual transformer. The metrological characteristics were inspected by importing actual PQ signal to the two models.The result shows that the transformer could track changes in primary DC current, but there was obvious error when sudden changes happened. Therefore it’s necessary to find how to improve the accuracy and response time in fault conditionFinally, the field test program was designed according to the actual situation and detailed test procedures and key equipment was introduced. |
