Voltage controlled underfrequency load-shedding in electric power systems

This report is a Master’s Thesis performed by Andreas Adolfsson and David Jacobsson at Chalmers University of Technology. The purpose of this master’s thesis is to evaluate a new method for load-shedding, the voltage controlled underfrequency load-shedding developed by ABB. This report presents a comparison between conventional underfrequency load-shedding and this new method for load-shedding. This master’s thesis also aims to present a detailed description of how the frequency regulation is performed in the Nordic power system. The simulations are performed using the analysis program Power System Simulator for Engineering (PSS/E). The Nordic32 power system is used for the simulations, this is a system with 32 buses based on the Nordic power system and developed by CIGRÉ. A PSS/E user model for the voltage controlled underfrequency load-shedding has been developed in this master’s thesis which is used for the simulations on this new method of load-shedding. A study of the voltage controlled underfrequency load-shedding shows that this method has important advantages compared to the conventional load-shedding when used in a power system with evenly distributed production and load. This method is not suitable for power systems where load and production is not evenly distributed, in a case like this the conventional load-shedding performs better. The results show that the use of voltage controlled underfrequency load-shedding achieves less constraint on transmission lines in the power system after a production loss. The voltage in vicinity of the production loss is improved when the voltage controlled underfrequency load-shedding is used