Load Soft Switching between the Main Power Grid and the Backup Grid by Fast Automatic Transfer Switching

Abstract: An approach to the construction of a control system for high-speed automatic reserve input (HARI) is considered. The system performs important algorithmic tasks in transferring loads to the backup grid with a sufficient degree of speed, taking into account the phase matching of the damped EMF of the motor and the voltage of the backup source, minimizing the resulting current surge at the time of load transfer. The induction motor run-out model serves as a means for decision-making by the HARI control system concerning the switching at a permitted time instant. Construction of a simulation model of the HARI system and extraction of the characteristics and transients are carried out in the MATLAB environment. Experiments related to the occurrence of an emergency and disconnection of a general-purpose grid are carried out with the following factors being considered: the level of supply-voltage failures, the time of occurrence of an emergency, the range of permissible phase mismatch, and the response time of switching devices. The result is the elimination of a number of shortcomings of the existing ARIs, the main one of which is the inconsistency of the switching moments of the voltage phase of the damped EMF of the motor and the voltage phase of the grid to which the connection is being made. The simulation results show that the developed control system has sufficient accuracy. © 2022, Allerton Press, Inc.