MPC - based Frequency Regulation and Inertia Mimicking for Improved Grid Integration of Renewable Energy Sources Diploma

In the future, renewable energy sources will contribute a significant share if not the majority of our energy supply. Especially for the electricity sector this means a radical transformation from current practise. The current infrastructure will in part need to be adapted but in part also to be rebuilt. This reorganisation taking place during “operation” increases the difficulty of the task at hand. The stability and safe operation of the electricity grid is of paramount importance and has to be guaranteed under the changing operating conditions. One aspect of variable renewable energies is their connection through power converters, electro-mechanically decoupling them from the synchronous grid. For rotating generators that means their rotational inertia cannot contribute to the frequency stabilising inertial response of the grid. Former research showed the ability of converter connected renewable energy sources to mimic the inertial response of conventional generators by using additional control loops. New control methods have been elaborated to give WTG an inertial response. This concept of mimicking inertia is one of the control strategies of this work. This thesis contributes strategies for supplementary control to stabilise the grid. Through the implementation of model predictive control (MPC), mimicking the inertial response of conventional generators as well as providing frequency control with wind turbine generators (WTG) can be achieved. The benefits and drawbacks of each type of control are discussed and the performance is compared. The concept is transferable to all converter connected electricity generators. The inertia mimicking lets the bus appear as a conventional generator.This increases the stability of the grid, as well as the functional value of renewable energy sources. In addition initial tests for the functionality of reference tracking as well as the inclusion of a state of charge are included in the simulations. Simulations and results presented in this work are based on the data and topology of the IEEE 14 bus test system.