Research On The Innovation Graph Technique For State Estimation In AC/DC Hybrid Power Grid

With the expansion of the scale of China’s power grid, the requirement for transmission line is higher. Therefore, due to the unique advantages of DC transmission technology, it has been widely used in high voltage and long distance transmission. For the power system, the pattern of system interconn ection in the whole country has been formed because of the application of DC transmission technology. Power system will form a complex AC/DC hybrid power system. The stability of power system safety operation has been further improved. In particular, it needs to consider the impact of the DC transmission line for the safe operation of the entire system. So it puts forward higher requirements to the original state estimation. State estimation is required to provide timely, accurate and comprehensive real-time operating conditions of the power system.Due to bad data and topology errors will affect the result of state estimation and the speed of state estimation, this paper will consider the problem of how to identify bad data, topology error and the abnormal events in the AC/DC hybrid power system. Due to the advantage of innovation graph approach in the AC power system for the handling of abnormal events, it is considered that it is combined with the AC/DC state estimation to identify bad data, topology error and the abnormal event overlapped in the AC/DC hybrid system.Firstly, the operation mode of DC transmission system is simplified. A simplified model for DC transmission lines is established. This paper analyzes and compares the common algorithm of the AC/DC state estimation. According to the requirements of convergence, accuracy and calculation, we choose the alternative method to calculate the AC/DC state estimation. The result of AC/DC state estimation is used as the forecast state in the innovation graph.Secondly, the new information network model of AC/DC hybrid system is established. This paper discusses whether the bad data identification and topology error identification on the innovation graph approach can be used in AC/DC hybrid system. While taking into account the influence of DC converter station loss of criterion, we discuss the DC converter station loss will affect the identification characteristics of bad data and topology error. When we analyze the influence of DC converter station loss at the same time, we should also take into account the distribution of DC transmission lines in a single loop or related circuit in the power system which will affect the identification of bad data and topology error. Then this paper gives out the abnormal event identification process of AC/DC hybrid system and verifies the example of the standard system.Lastly, we study the identification of bad data in the DC power transmission system in the DC power system. This paper analyzes the correlation between the measurement of DC system and identify the bad measurement by using the correlation of the measurement’s innovation.This paper shows that the innovation graph can identify the abnormal events in the AC/DC hybrid system, we also verify that the correlation of measured data’s innovation can identify the bad data.