Mahr F (2024)
Publication Language: English
Publication Type: Thesis
Publication year: 2024
Energy systems are in transition. Sustainable and reliable energy systems are cornerstones
of human societies. Renewable energy sources (e.g. wind power plants
and photovoltaic power plants) and innovative consumer technologies (e.g. electric
vehicles and heat pumps) as well as necessary energy storage devices are connected
via power electronic components to the electrical grid. The penetration of the grid by
voltage source converters (VSCs) as one type of power electronic components will
increase. 100% VSC-based power systems will arise. Protective systems against
grid faults are a substantial part of electrical grids. They prevent danger to living
beings and damage to technical equipment.
VSCs and protection must collaborate in future grids. Otherwise, the reliability of
energy supply is at risk. The characteristics of VSCs differ from the characteristics
of synchronous machines used in conventional power plants. Today, protection algorithms
are often not adapted to the characteristics of VSCs. At the same time,
the flexibility options of VSCs to increase the reliability of the energy supply are
not fully utilized today. VSCs and protection algorithms are typically regarded separately
from each other. State-of-the-art approaches are often unilateral. One approach
is to control VSCs in a way to adopt the characteristics of synchronous machines.
Here, the possibilities of VSCs to increase the system resilience against grid
faults are restricted. Another approach is to use adaptive distance protection algorithms.
Here, the settings depend on the situation and represent only a selective
solution.
In this thesis, an alternative approach is presented. VSCs and protection algorithms
are not regarded independently of each other. A holistic principle is developed. The
key aspects of this thesis to realize sustainable and reliable energy systems are:
• Post-fault characteristics of VSCs
• Neutral point treatment and resonant grounding via VSCs
• Model-based protection algorithm
All control and protection algorithms in this thesis are developed analytically. They
are validated in software simulations. In addition, the model-based protection algorithm
is validated in real hardware laboratory tests.
The developed control algorithms of VSCs and protection algorithms for 100%
VSC-based power systems show significant advantages over existing approaches.
Realizing desired properties of frequency and active power in the positive sequence
after a grid fault leads to a stable grid behaviour with defined power flows. The realized
characteristics in the zero sequence reduce fault currents and allow continuing
the grid operation after single-phase-to-ground faults. The model-based protection
algorithm is suitable for VSC characteristics and does not restrict flexibility options
of VSCs to increase the system resilience against grid faults. Overall, this thesis
contributes to the realization of sustainable and reliable energy systems.
APA:
Mahr, F. (2024). Control and Protection of 100% Inverter-based Power Systems (Dissertation).
MLA:
Mahr, Florian. Control and Protection of 100% Inverter-based Power Systems. Dissertation, 2024.
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