Analysis and Practical Assessment of Converter-Dominated Power Systems : Stability Constraints, Dynamic Performance and Power Quality

For years, large power systems have been predominantly managed using the very well known synchronous machine on the generation side. With the increasing penetration of load and generation interfaced by converter-based systems, the conventional synchronous machine is being gradually replaced by these new devices. However, this slow and steady change of the generation technology has led to side-effects which can affect to the local stability and, if no remedial action is taken, system-wide stability. The main objective of this thesis is to understand, expose and overcome the weaknesses of converter-dominated grids within a laboratory environment. To do so, a converter of 10kVA has been built implementing the standard D-Q axis Current Injection (DQCI) control and, for rst time to date, the Virtual Synchronous Machine with Zero Inertia (VSM0H). Further developments have been made to this control strategy to implement this theoretical algorithm into a real system. The solutions proposed in this thesis for converter-dominated grids are based on the Grid Forming Nodes (GFN) solution. This composition suggests the usage of a combination of DQCI and Virtual Synchronous Machine (VSM) converters to achieve stability within converter-dominated grids. However, there is limited understanding about VSM functioning. Initially, the application of VSM-style converters was proposed as a natural replacement of the real synchronous machine present in the system without understanding which are the specific weaknesses that affect to this type of grid. Due to the aforementioned reasons, this thesis aims to provide a more scientificc and rigorous explanation of why the GFN solution can provide stability for converter-dominated power systems. Using the converter built, it is possible to recreate scenarios where the technical challenges involved in power systems can be understood