Study On Voltage Stability And Reactive Power Optimization Of Power System Based On Bifurcation Theory

As power system is often operating under heavy loads conditions and generation centralized in a few local power plants, thus voltage stability is more serious than before and voltage collapse incidents throughout the world happened frequently. It is well-known that lacking of reactive power is the major reasons for voltage collapse. VAR planning is important to guarantee voltage quality, minish power loss, enhance static voltage stability and achieve secure and economic operation in power systems. In this paper, new ideas have been put forward based on several aspects, such as calculated of static voltage stability margin, selected candidate bus, mathematical model of voltage-VAR planning and optimization solution. The major contributions of this thesis are detailed as follows:The optimal model is established to calculate the minimum load margin for Saddle Node Bifurcation and Limit Induced Bifurcation in power system. The increase of load is fluctuant because of its randomicity, which is more approached to practical system. The sensitivity is computed with extended power flow Jacobian matrix, thus avoided the singularity demand in solution process. The method can provide the voltage stability margin and the possible voltage collapse style for planning and operation personnel in power system. There is critical guiding significance to safety and reliability of system.The mathematical model of voltage-VAR planning has been established based on static voltage stability margin in this paper. The objective function is the equipment investment of reactive compensation and the integration cost of active power loss, and the minimum load margin is considered as voltage stable constraint. Compared with conventional reactive power planning model, this model can obtain optimal reactive power configuration scheme directly under a suitable voltage profile according to a target value of the stability margin. Thereinto, the reactive compensation bus is chose by using"subarea-sensitivity"combining method. 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 compensate bus.In this paper, for the power system model and related algorithms, calculated by continuation power flow and interior-point linear programming algorithm separately, write the MATLAB simulation procedures, simulation results show that the proposed model and algorithm is effective and practical.