The Research Of Power System Under Voltage Shedding Load Setting Strategies

Under Voltage Load shedding is an important measure to inhibit the voltage collapse and maintain the voltage stability of power system. Reasonable and effective option the node to shed load can make power system recover to a stable condition in the shorter time, which is one of important means to ensure safety operation of power system.Firstly, from the perspective of the power balance, the paper illustrated that the basic requirements of the system voltage stability is to ensure the system reactive power balance. Meanwhile, the system voltage stability is related to dynamic load characteristics and operation status before voltage collapse. On the foundation of fully understanding the principle of power system voltage stability, the quantitative relation between the critical stability voltage of the load node and load power is derived through a simple single-circuit transmission line. It illustrates that appropriate load resection can effectively reduce the power system critical voltages and maintain system stability.The rise of system voltage is associated with each node load power changing in the process of under voltage load shedding. Therefore, a sensitivity coefficient of the node voltage along with the node load power changing is discussed in this paper, which has an important effect on the node voltage rise, and the relationship among the sensitivity coefficients of the node voltage with node load power changing is deduced by the reduced-order Jacobin matrix. On this basis, the load of higher sensitivity coefficient is prior removed, which can get optimal load shedding programs. The method ensures faster rise and higher voltage stability margin of the system voltage, and the simulation results demonstrate the effectiveness of the scheme.The reliability and economy of load shedding must be considered in the power market environment. For various qualitative and quantitative factors about reliability and economy, Fuzzy Analytic Hierarchy Process is used to make a comprehensive evaluation on the voltage impact factors of each load node in this paper, which can get a comprehensive weight load shedding scheme giving consideration to various factors such as sensitivity coefficient, node voltage, load importance degree, average load rate and power outrage cost. With an example and simulation, simulation results show that the proposed load shedding order can make a rapid voltage recovery within the range of safe and stable operation of the system voltage, it is reasonable and effective. Therefore, the combined effect of this method is superior to other traditional methods.