Multi-objective Voltage-VAR Planning With Static Voltage Stability Margin

As generation centralized in a few local power plants, electrical distances between generation and load are far away; power system is operating under heavy loads conditions. Because of lacking of reactive power, thus voltage stability is more serious than before, voltage collapse incidents throughout the world happened frequently. VAR planning is of great importance to voltage quality guarantee power loss minimization.. enhancing static voltage stability and thus secure economic operation of power systems. In this paper, new ideas have been put forward based on several aspects, such as selected candidate bus and central bus, mathematical model of voltage-VAR planning and Multi-level VAR planning, and satisfied results are obtained. The major contributions of this thesis are detailed as follows:The relationship of voltage magnitude and static voltage stability margin is analyzed in details. Under heavy loads conditions: voltage magnitude within a specified margin does not imply voltage stability. So, it is important to consider voltage stability margin in VAR planning. The optimized mathematical model of VAR planning based on static stability margin is established in this paper.Var/voltage is considered to be a local problem rather than a global systematic. So ,the paper presents a new method of combining network partitioning with voltage stability sensitivity index to determine candidate bus: First, power system network is partitioned; then, the voltage stability sensitivity for all bus in load subarea is calculated; finally, the largest voltage stability index is selected as candidate bus. And two ways of partitioning network is present in this paper : "decomposition- incorporated" recursion method and decomposition search in layer ?The mathematical model of multi-objective voltage-VAR planning has been established in this paper. The objectives consist of four important terms: investment of reactive source> average voltage deviation of PQ bus -. static voltage stability margin and real power loss. Multiple objectives aren't commensurable. Consequently, it is necessary to present a fuzzy goal to convert objective into numeral, and weighted approach to combine Multi-objective problem into single objective.From the mathematical model of multi-objective voltage-VAR planning, not only the location and capacity of shunt compensator is determined, but also central bus and capacity can be gained . The method of selected central bus and its capacity is present in this paper.Power system operates in different load levels; it is necessary to consider multi-levels in VAR planning. Based on the idea of dynamic programming, the model of Multi-level VAR planning is established in this paper.Continuation power flow (CPF) is adopted to calculate the voltage stability margin, and auto-step approach of CPF is designed in this paper, the speed of CPF is accelerated.GA based on CPF is adopted to calculate the optimizing model of VAR planning, and The software solution of the reactive power planning system is designed in this paper. The reactive power optimization model has been tested in IEEE 14 buses IEEE 57 buses respectively and a real power grid. The results are fairly well.