The reactive power support forms of the new power system have undergone significant changes on the power source side, grid side, and load side. The traditional large capacity generator sets on the power side have been replaced by small capacity wind and solar energy storage power sources. The scale of AC/DC hybrid connections on the grid side is constantly expanding, and the proportion of renewable energy output on the load side is high, with characteristics such as randomness, volatility, and intermittency. These factors have led to new changes in the voltage support capacity and form of the power system after disturbances.
Traditional accident analysis mainly focuses on the issues of thermal limits and voltage amplitude exceeding limits, while the integration of new energy sources into new power systems significantly weakens voltage support capabilities and increases the risk of voltage instability caused by low stability margins. This article introduces the dual constraints of voltage safety and voltage stability margin, which can more accurately identify the potential voltage instability problems that may occur in the system after accidents, providing stricter standards for the safety and stability analysis of complex power systems.
The concept of coherency originated from transient stability analysis of power systems, with the aim of aggregating generators with similar dynamic characteristics after disturbance into equivalent values, thereby simplifying the analysis; Subsequently, some literature extended the concept of generator synchronization to the coherent contingencies group in transient stability analysis, aiming to reduce the analysis and calculation workload of expected accidents. In the research process of this article, the contingencies for voltage stability and voltage safety also have the characteristic of coherency. Therefore, this article further extends the concept of coherency to the field of voltage safety and stability, and proposes the concept of coherent group characteristics for contingencies for voltage safety and stability, aiming to reduce the computational load of contingencies analysis for voltage safety and stability. This article reveals the similarities in static characteristics of N-k contingencies under different operating conditions, such as load margin, voltage distribution, and generator reactive power exceeding limit sequence. By defining load margin spacing and voltage amplitude spacing as quantitative indicators, the division of synchronous accident groups can be achieved. This expansion not only enriches the application scenarios of homology theory, but also provides new theoretical basis for rapid safety assessment of large-scale power systems.
In response to the problem of high computational complexity in the traditional method of analyzing N-k contingencies item by item, this paper aggregates accidents with similar static features into groups based on the characteristics of coherent groups, and selects representative accidents for detailed analysis. At the same time, this method is robust to different control measures and source load uncertainties, and can meet the real-time requirements of online safety analysis, providing theoretical support for N-k safety assessment and preventive control under different operating conditions. Finally, simulation analysis was conducted using the 118 bus and 3120 bus power systems as examples to verify the effectiveness of the proposed phase backbone grouping method.