Initialization for Dynamic Simulation of Stressed Power Systems Considering Induction Motor Components of Loads

Power flow solution is used for the initialization of power system dynamic simulation. Available production grade software packages (PSS/E in case of this paper) assume PQ-model for induction motor components of the loads during initialization process but consider accurate dynamic model for the dynamic simulation phase. Since the reactive power consumed by the motor is not known prior to power flow solution, a fictitious shunt reactance is added to the system bus to account for the difference between the assumed and the actual reactive power consumption of the motor. With the added fictitious reactance to different buses, the simulation system no longer represents the actual power system. The objective of this paper is to show that, although the existing method of initialization used by available software packages (PSS/E in case of this paper) produces satisfactory results for lightly loaded systems, it gives erroneous results in the case of stressed systems. The IEEE 14-bus test system is used to prove this claim. The system is simulated for stressed and unstressed situations applying commonly used initialization method and other method that considers the actual induction motor model during the initialization process which does not require the fictitious added reactance. It was seen that the commonly used initialization method could result in inaccurate assessment for power system stability in case of stressed system. Also in this paper, an iterative procedure is proposed that shows how to obtain the correct initial values using PSS/E without the need for the fictitious added reactance that causes erroneous simulation results.