Power Grid Transient Stability Risk Assessment Based On Multi-source Information Fusion

In the journey towards the future power grid, China’s power grid is experiencing from the traditional to the unified strong and smart grid with UHV as the backbone. Power generation, transmission, distribution, transformation, utilization, telecommunication and other areas are undergoing unprecedented changes. Due to the factors including the contradiction of reverse distribution of the energy and the highly concentration of power generation and consumption, there are potential risks and hidden dangers in the operation of power grid. Strengthening investigation of instability risk of the online operation mode is conducive to timely detect security risks of grid and to avoid cascading failure and other serious harm accidents. Several key technologies including information integration of power grid transient stability risk assessment, dynamic expected fault set generation, fast transient stability calculation and instability control strategy, power grid accident risk grading have been studied in depth. Innovative results are formed as follows.①For multi-source information integration, the essence of that WAMS data constitutes the special big data of power system is deduced based on the premise of the big data feature agreement, which points out the theoretical basis for the processing of WAMS information by using big data technology. A kind of new method of double set elastic storage for WAMS specific big data is proposed, which solves the problem of high frequency conversion of mass data and concurrent access of multi applications. In addition, the three-section data integration and calibration assessment method is proposed. The SCADA measurement values and the WAMS high frequency measurement values are combined to modify operation state estimation values of EMS. The selection of the operation mode parameter and WAMS identification results are combined to revise topology and calculation parameters of elements. The availability of multi-source data is evaluated using the evaluation index of operation and model parameters, which can avoid the error caused by dirty data.②In order to improve the overall calculation efficiency of the power grid stability risk assessment and to enhance the coverage rate of expected failure for power grid stability risk analysis, the complete set of contingency equipment is obtained by the full connection topology analysis. Based on the static security calculation of power grid, the double-entropy index nine-grid screening failure equipment filter method is proposed. The SVM failure equipment filter method based on the operation history data is proposed. Through the combination of the above two methods, the fault template generation technology is also used to realize the dynamic adjustment of the expected fault set. The generation time of single fault is controlled in the vicinity of 1ms. The method for generating dynamic fault set takes into account the failure probability of equipment and the degree of harm to the power grid, which can limit the explosive growth of the number of the fault effectively. This method provides a solution to reduce the risk assessment calculation intensity and scale.③For calculation and analysis of power network transient stability, instability and stability control, a quick and automatic method to calculate the load loss is proposed. Taking into account the requirement of speed and accuracy, the hybrid parallel computing method combination of transient implicit trapezoidal integration method and the full implicit Runge-Kutta method is used to save time for risk assessment. Taking the center of inertia as reference datum, the tracking the offset of the node voltage angle relative to the reference as main criterion, the same direction of node voltage phase angle velocity with acceleration and the reverse direction of power change rate with angular velocity as auxiliary criterion, the accurate judgment of power angle instability is realized. The unstable optimization objective and constraint function taking cutting machine and load as main control measures are constructed. The differential algebraic equation is used to solve the gradient of the constraint function. The double sensitivity index of cutting machine and cutting load is constructed by using gradient as multiplier to solve the problem of the combination of fast and optimal search of stability measures. Based on the whole process monitoring and analysis of the transient stability calculation, the comprehensive statistics of the passive loss of power network fault load and the loss of active removal are realized.④ Taking Decree No.599 of the State Council as a criterion, the risk grading index of the transient stability of the power grid is established based on the load loss rate as the leading factor. According to the characteristics of different administrative divisions, a multi-level model of power system transient stability risk assessment is constructed. Considering the complexity of power supply, combining the direct judgment and the analytic hierarchy process, a method of risk assessment is proposed to solve the problem of the grading of accident risk in the multi-level subordinate administrative region. The grading analytic hierarchy process method of power grid fault combines with the influence of differences of load characteristics, regional characteristics and serious degree, which avoids the risk of emphasizing the power grid security and bring huge power grid investment and the depth of conservative operation.