Study on the Corresponding Relationship Between Critical Points of P-V Curve and V-Q Curve of Simple Thevenin Equivalent System

With the further increase in power demand for highly concentrated load centers and the gradual formation of a power system with a high proportion of new energy sources, China will face severe risk of voltage instability. In this paper, firstly, the load bus voltage equation of simple Thevenin equivalent system is derived, and then the P-V and V-Q curves are obtained respectively. Secondly, the mutual restriction relationship between active and reactive power of load is discussed when there is a real value solution to the voltage. Finally, the relationship between the voltage of critical points of the P-V curves and the reactive power of the load, and the relationship between the voltage of critical points of the V-Q curves and the active power of the load are deduced respectively. The relationship of one-to-one correspondence between critical points of P-V curves and critical points of V-Q curves is proved according to the mutual restriction between active power and reactive power of load and monotonicity of critical voltage and load power function.