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Study on Zoning Optimization of Provincial Power Grid After UHV AC/DC Line Connection

With the development of UHVAC and UHVDC power transmission technology, the power receiving proportion of receiving-end grid is increasing, the security and stability characteristics of receiving-end grid become more and more complex. Researching on the layering and zoning operation scheme of receiving-end power grid after feeding UHVAC and UHVDC transmission systems is useful for the safety and stable operation of power grid. In this paper, comprehensive evaluation indexes of district grid are established by considering economy, security, stability and reliability of the system. An optimal layering and zoning scheme is chosen from multiple layering and zoning alternatives through the multi-objective decision-making method of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) based on grey relational theory. The feasibility and effectiveness of the proposed are verified through the actual power grid, which can provide technical support for layering and zoning optimization of receiving-end power grid after UHV AC/DC line connection. Introduction With the development of UHV AC/DC power grid, UHV AC/DC hybrid structure has been formed in East China, North China and other receiving-end power grids. The replacement effect of DC to conventional unit in the power grid is further intensified, resulting the power receiving proportion of the internal partition of receiving-end power grid increases. The serious frequency and voltage problems may occur after isolated grid operation of district grid in serious faults [1-4]. In this high-power mode of power receiving, relying solely on under-frequency load shedding (UFLS) and under-voltage load shedding (UVLS) are difficult to ensure the safe and stable operation of district grid. In order to ensure the safe and stable operation of the district grid, interchanged power of district grid needs to be controlled or the measure of increase emergency load cutting after isolated grid operation of district grid needs to be taken, which increases the risk of power grid to cut the load invisibly and has large hidden danger of electric power safety accident. Therefore, the layering and zoning scheme of power grid needs to be optimized according to the development of power grid [5-7]. First, the quantitative evaluation indexes of layering and zoning covering economy, safety and reliability are established in this paper. The optimization method of layering and zoning scheme considering multiple constraints is proposed. Multiple layering and zoning alternatives based on the reserve channel of the power grid are established. The best scheme is chosen from the alternatives through the multi-objective decision-making method of TOPSIS based on grey relational theory. The problem of the contradiction between economy, security and stability and reliability in power system operation control can be solved well.