Voltage instability in a power system with single OLTC

Investigates power system voltage stability in the presence of on-load tap-changing (OLTC) transformers. To assess this type of voltage instability, the sensitivity, dV/dn, of a load voltage, V, to a tap position, n, is analyzed to show the following theoretical results: (1) The region of normal control where inverse control action does not occur lies inside the stability region when there exists an equilibrium. This region is presented as O<I<I_max. (2) Even if an equilibrium does not exist, the voltage continues to recover in the region where this condition holds. (3) The operating point I=∞ corresponds to the point of the static bifurcation which is caused by the dynamics of the load at the bus controlled by the OLTC