Modeling Dynamic Frequency Control with Power Reserve Limitations

The frequency variation of a power system depends on the relationship between power generation and consumption. Increase in loads, losses or inclusion of renewable energies will lead to inaccurate controllability of the network frequency, which is the result of consumption-generation imbalance. If this imbalance is high, damage and degradation of network performance, as well as trips of loads and generators is inevitable. In modern grids attention is given to the amount of power supplied to satisfy the loads and system losses and also for reserve services. The latter provides security and stability of the system.Frequency control is usually provided by generating units to regulate the generated power. In modern networks such as smart grids, the power reserve concepts are used via three different technologies, namely: Frequency Containment Reserves (FCR), Frequency Restoration Reserves (FRR) and Replacement Reserves (RR). In some countries such as Denmark and Norway, it is compulsory for FCR to be implemented in the network. The FCR is operating the reserves necessary for constant containment of frequency deviations from nominal value in order to constantly maintain the power balance in the whole synchronously interconnected system. Compared with traditional reserves, the FCR can deliver the same service plus the additional benefit of faster response speed in seconds.This paper proposes a dynamic simulation model of an interconnected network to identify frequency responses based on current practice in power systems frequency control. The dynamic frequency response identification method is deployed in two steps: the first step is the representation of the dynamic models of the power system through the power equilibrium equation and in the second step, modelling the frequency control system in response to the frequency variations, which consider FCR technology. Simulations are carried out in MATLAB/SIMULINK and the simulation studies of the frequency responses confirm that FCR technology can provide reliable performance of frequency control.