Voltage stability affected by on-load tap changer considering excitation reactance of induction motor

Following disturbances, on-load tap changers (OLTC) act to restore the load bus voltage and thus restore the load power to near pre-disturbance level. However, the reverse action caused by OLTC may deteriorate the operating condition in a heavily loaded power system and results in voltage collapse. Considering the excitation reactance of induction motor, the paper analyzes how the maximum power transfer limit is affected by OLTC ratios. The theoretical analysis demonstrates that in the normal regulating range the maximum power transfer limit is of three kinds of changing trends, that is, monotone increasing, decreasing after increasing and monotone decreasing respectively. Further dynamic simulation results show that the regulating voltage effect of OLTC, especially the reverse action, becomes more complex due to the three different changing trends