Fault ride-through capability studies of MMCHVDC connected wind power plants have focused primarily on the DC link and onshore AC grid faults. Offshore AC faults, mainly asymmetrical faults have not gained much attention in the literature despite being included in the future development at national levels in the ENTSO-E HVDC code. The proposed work gives an event-triggered control to stabilize the system once the offshore AC fault has occurred, identified, and isolated. Different types of control actions such as proportional-integral (PI) controller and super-twisted sliding mode control (STSMC) are used to smoothly transition the post-fault system to a new steady state operating point by suppressing the negative sequence control. Initially, the effect of a negative sequence current control scheme on the transient behavior of the power system with a PI controller is discussed in this paper. Further, a non-linear control strategy (STSMC) is proposed which gives quicker convergence of the system post-fault in comparison to PI control action. These post-fault control operations are only triggered in the presence of a fault in the system, i.e., they are event-triggered. The validity of the proposed strategy is demonstrated by simulation on a 525 kV, three-terminal meshed MMC-HVDC system model in Real Time Digital Simulator (RTDS).

Voltage source converters (VSCs), particularly modular multilevel converters (MMCs), play a pivotal role in modern power grids due to their application in interconnected systems and renewable energy integration. However, their complex internal dynamics and control systems can cause stability issues under a variety of operating conditions. Impedance-based stability analysis is critical for understanding these interactions and ensuring grid reliability. Traditional small-signal models based on physics and circuit analysis often neglect nonlinearities and practical implementation details, limiting their accuracy. In contrast, black-box impedance measurement techniques necessitate significant computational resources and human effort, particularly when analysing both AC and DC side impedances.

This thesis presents a transfer learning framework for accurate impedance characterization of MMCs. The framework uses a combination of linear time-invariant (LTI) modeling and black-box impedance measurements to estimate impedances based on system-level parameters such as AC and DC side voltages, active power, and reactive power. The methodology involves pre-training artificial neural network (ANN) models on a diverse dataset derived from LTI models, followed by fine-tuning with real-time electromagnetic transient (EMT) simulations. Unlike traditional approaches, which use a single ANN model across the entire frequency range, this study discusses the use of multiple smaller ANN models tailored to specific frequency ranges and operating points, which improves prediction accuracy.

The effectiveness of the proposed transfer learning framework is demonstrated with a practical MMC converter from the CIGRE B4 DC grid test system. The results show that impedance estimation outperforms traditional ANN methods even in scenarios involving confidential converter parameters. This approach allows for precise impedance characterization while reducing computational complexity and data requirements.

The MMC-based MTDC systems are considered a promising solution for long-distance power transmission, integration of renewable energy sources, and interconnection of power grids. Nowadays, MMC-based MTDC systems have been successfully developed in various projects worldwide and are expected to play a significant role in future electrical power transmission systems.

Despite the benefits provided by the MMC-based MTDC system, various technical problems emerge. For example, in case of a DC fault on HVDC transmission lines, the DC voltage suffers a deep sag, and the fault current increases to the peak value after several milliseconds, the system stability is seriously affected. The fault currents will easily damage the power electronics and may lead to a collapse of the entire system if the faults are not cleared promptly. Thus, it is crucial to implement a fast, selective, and reliableDC fault protection technology in the system for fault detection. Once the fault is cleared, it is important to know the exact fault location to repair the faulty sections and to restore the system. Hence, an accurate DC fault location technique is of utmost importance for the MTDC system, which would significantly minimize electricity loss and expedite the system restoration process in the event of power outages. In addition, there is a lack of standardization in MMC control, and the majority of HVDC projects are constructed in a vendor-specific manner. As of today, it is unclear how MMC converters from different manufacturers will interoperate with each other. These pose new challenges to the performance of HVDC protection and MMC control and need to be addressed to manage, safeguard, and accelerate the practical feasibility of this system.

The research in this thesis aims to address the shortcomings that have not been addressed in the state of the art, mainly related to the challenges arising when DC faults occur in the MMC MTDC systems and, as such, could provide promising solutions for future practicalMTDCapplications. The main topics areMMC control&interoperability, Protection, and Fault location for the MMC-based MTDC system. The thesis deals with designing a robust protection scheme, a fault location method, and an investigation of the interoperableMMC controllers...
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Submodules are the building blocks for MMC-type HVDC converters and therefore of utmost importance for converter reliability. In order to unlock smarter maintenance strategies for submodule semiconductors, the technical condition of the semiconductors needs to be estimated to form a health index. Besides the non-project-specific traditional health index methods, a complete practical implementable data-driven lifetime estimation approach for individual converters is needed to determine the exact remaining useful lifetime of all submodule semiconductors. The methodologies should finally explore a new research direction in the optimization of the converter lifetime considering maintenance intervals. This thesis presents a health index methodology applicable to submodule semiconductors in modern MMC-type HVDC converters. The ON-state collector-emitter voltage is used as a condition indicator and external influences are neglected with electrical and thermal models. These models are needed to estimate the junction temperature in the submodule semiconductors due to the temperature-dependent ON-state collector-emitter voltage. A novel lifetime optimization methodology is presented that determines the submodule that is near its end-of-lifetime and should be replaced in the next maintenance interval. In order to optimize the converter lifetime, the selected submodule is switched more frequently based on a selection window generated from the submodule insertion vector. Switching this submodule more frequently can ensure that it fails exactly at a determined time instant and allows other submodules to be switched less frequently extending their remaining useful lifetime. Finally, a complete data-driven lifetime estimation methodology has been described that uses available measurements in existing MMC-type HVDC converters. Based on the converter load profile and the semiconductor specifications, estimations are made on the submodule semiconductors’ lifetime. Simulations show the significant influence of the DC-pole current based on different voltage class semiconductors and their limitations considering the minimum required lifetime.

Zero emission fuels and reducing emissions are important topics in all transport sectors and hybrid systems play a key role in the transition towards full decarbonization. This thesis studies the components that are found in hybrid maritime electrical power systems and their influence on power quality, short-circuit currents and protection & coordination. In order to help system integrators such as Alewijnse in the design of these hybrid systems, two typical models of actual vessels are created in simulation software ETAP. Both systems are low-voltage, high-power systems, based on either an AC or DC busbar.

Rules and standards related to power quality and short-circuit currents are studied as well as practical protection strategies. For the AC model, various studies have been successfully simulated including a load flow study, transient stability study including peak shaving and virtual generator simulations for the battery, a protection & coordination study and a harmonic study. Some challenges with ETAP regarding DC grid simulations are discussed, but is also demonstrated how to use the formulas and standard approximation function from the IEC 61660 to calculate short-circuit currents and I2t values and how to use these results in the protection & coordination study.

With an accelerated inclusion of renewable energy generators in the power system, the inertia support traditionally provided by conventionally powered synchronous generators is lagging, and power system stability is reducing. This grid-supporting behavior will now have to be provided by the power converters of renewable energy sources with the help of power electronics. Grid forming control refers to the idea of the converter’s ability to set its frequency and voltage by means of emulating similar characteristics as that of conventional synchronous generators. Most of the protection and control studies on grid forming control for wind turbines have been done using a simple power system model containing the generator and an infinite AC bus and very less insight is available for grid forming generators in a realistic power system. This study aimed to apply the grid forming control strategy on DFIG (Type-3) and full converter wind turbines (Type-4). For this, the MIGRATE benchmark models in RSCAD/RTDS were used for the comparison of the key power indicators for both grid forming and grid following controlled modes. This was followed by the development and validation of the grid forming controller as a black-box model using IntervalZero and RTDS software in the loop setup (SIL).

Integrating renewable offshore wind generation into global power grids is a critical issue in the energy industry. Modular Multilevel Converter (MMC)-based High Voltage Direct Current (HVDC) grids are the most effective and promising technical solution for the new offshore wind energy power system connections. These grids offer scalability, controllability, and reliability advantages, but their stable and compliant operation requires implementing MMC control strategies and controllers. This thesis investigates the intricacies of HVDC technologies, focusing on MMC control strategies and controllers. The research explores grid following and grid forming converter control strategies, essential for ensuring stable and compliant operation of MMC-based HVDC grids.
The research elaborates on the Model Predictive Control (MPC), which is a promising control strategy for MMC-based HVDC grids. The MPC controller makes the control strategies respond faster, emphasizing constraints
and cost functions. Furthermore, a comparative analysis of Proportional Integral (PI)-based and MPC-based
controllers is conducted across various scenarios, highlighting the advantages of MPC-based controllers over
PI-based controllers regarding response time and stability.
Lastly, a large stability analysis is conducted using the direct Lyapunov method to evaluate the effectiveness of the control strategies and controllers during transient events. This analysis provides insights into the stability and performance of MMC-based HVDC grids under different operating conditions and disturbances.
This thesis illustrates the capabilities of grid-forming control strategy through Model Predictive controllers for
FPGA-based MMC-MTDC networks on RSCAD/RTDS®. The outcomes of this thesis contribute to advancing
HVDC technologies and control strategies, with implications for enhancing the stability and efficiency of MMC-based HVDC grids. The findings of this thesis have significant potential in the energy industry, particularly in integrating renewable offshore wind generation into global power grids.

This Master's Thesis is conducted in collaboration with Alewijnse, a leading maritime systems integrator in the Netherlands. The thesis aims to identify the optimal and cost-effective method of incorporating battery energy storage systems (BESS) into both new and existing DP-2 vessels, as well as DP-3 vessels. The objective is to determine the most efficient battery size and technology, establish the ideal time frame for return on investment, and design a power generation schedule that is ideal for the DP-2 cable laying vessel’s power system.

The primary objectives of this research are to optimize the battery system, ensure effective energy system operation, and establish a strong business case. Specifically, the study explores the feasibility of retrofitting a DP-2 vessel that operates in the North Sea and Taiwan with a battery system to create a hybrid system.

To determine the optimal sizing of the battery energy storage system, 12 different battery solutions from two European battery suppliers considering three different fuel price scenarios are analyzed. These solutions encompass a variety of battery technologies, such as High Power or High Energy Li-ion batteries or a combination of both.

The integration of BESS into vessels offers several operational benefits to operators, including the ability to operate diesel engines at higher or more efficient points of operation to maximize their performance. Battery systems can also act as ”virtual generators” during dynamic positioning (DP) mode for DP-2 vessels, reducing fuel consumption, lowering diesel engine ON-time, and decreasing maintenance costs.

However, hybridizing vessels involves more than just integrating an optimally sized battery system.The existing power management system (PMS) and energy management system (EMS) must also undergo upgrades to ensure effective operation. To address these challenges, the BOOSTER (Battery Optimization for Optimal Sizing and Throughput Energy Regulation) methodology is proposed, which incorporates the operation of an optimized management system based on fuel prices and the throughput energy cost of the battery system.

The energy transition requires massive expansion and reinforcement of the transmission grid which is challenging because of its high utilization, and regular maintenance, replacement, and repair. The difficulty of performing maintenance on high-voltage equipment and especially the substations lies in the fact that a big part of the substation needs to be taken out of service for the maintenance crew to work safely. When a part of a substation is taken out of service this influences the capacity and redundancy and thus the reliability of the grid. A planned outage is required to take a part of a substation out of service, these planned outages are limited in frequency and duration due to a shortage of especially trained and skilled people in combination with the high utilization of the grid.

The objective of this master thesis is to investigate important design aspects for mobile transmission stations to reduce/prevent planned outages during maintenance, replacement, and expansion projects on TenneT's (the Dutch transmission system operator) permanent substations. A mobile substation is a fully equipped substation mounted on one or multiple trailers to be easily transported. The mobile substation provides a bypass during maintenance on permanent substations allowing continued service without requiring planned outage.
A case study in this work shows that using a mobile substation during maintenance, replacement, and expansion projects on substations can possibly save TenneT several hundred million euros per year. Using the mobile substation on a 380 kV or 220 kV substation would make it possible to work on multiple 380 or 220 kV substations at the same time. It would also be easier to get a planned outage permit for the 150 kV and 110 kV substations. The use of a mobile substation would thus increase the efficiency of the projects and would reduce the amount of required critical resources.

Besides the case study, this work investigates the design requirements for mobile substations. The mobile substation should be able to (partly) bypass all TenneT substations and should contain mobile power transformers. The weight of the mobile substation is limited by road regulations. The transformers will be the heaviest components in the substation thus special attention is needed for their design. For the power transformers, a shell-type core design would be preferred with (high temperature) hybrid-insulation, due to its compact design and robustness for transportation. To comply with road regulations without special permits six 83.33 MVA single-phase transformers with an approximate weight of 36 tonne need to be connected in two banks of three single-phase transformers to reach the standardized capacity of 500~MVA.

The insulation distance in the mobile substation will greatly influence the size of the substation when deployed and during transport. Therefore, this insulation distance is an important design aspect which is covered in this work. The standards for insulation distances were analyzed. This analysis gave rise to doubts if these distances would apply to compact substations with large electrodes. An experiment was conducted at the TU Delft Electrical Sustainable Power Lab to determine the dielectric strength of large electrodes with sharp points in compact substations, and to verify if the insulation distances as specified in the standards should be applied to mobile substations.
It was found that the large electrodes with sharp points have similar breakdown voltages as a rod-rod gap setup. A higher breakdown voltage was found for the large spheres with protrusions compared to the rod-conductor gap which is used by the IEC standard. This indicates that the IEC standard insulation distances would be sufficient for use in a compact substation. Whether the substation can be made more compact by reducing the insulation distances should be investigated by executing experiments on an actual skid in a future study.

Busbars are one of the most crucial components in the electricity grid and, as such, must always be protected against all types of faults.
The busbar differential protection is a protection scheme typically utilized to protect the busbar system in high-voltage substations. Nevertheless, due to the vast number of substations in the distribution level and the high cost of differential busbar protection, DSOs try to implement more cost-effective protection schemes for the busbars. This includes using various communication-based protection schemes, such as the reverse-blocking scheme that Stedin implements. However, due to impedance grounding, the single-phase-to-ground short circuit current can reach small values in magnitude in medium voltage distribution grids, making detecting it more challenging for these protection schemes. That is the problem that Stedin experiences in its network.
In this thesis, a novel communication-based protection scheme is proposed as a solution to this problem. The protection scheme utilizes the IEC 61850 standard and the currently available infrastructure Stedin owns. The scheme can be considered a distributed protection scheme. The grid is modeled in RTDS, and a HiL simulation is carried out to test the protection scheme. The extensive simulations show that this scheme can detect single-phase-to-ground busbar faults in impedance earthed networks. Some limitations of the proposed scheme are also seen in the simulation results. Furthermore, a centralized approach for busbar protection is discussed. Two algorithms are developed based on GOOSE and SV messages, respectively. HiL simulations are carried out for these centralized algorithms too. The advantages and the considerations for implementing centralized protection are discussed. These findings can serve as a basis for further research for Stedin in the domain of centralized protection.

Photovoltaic technology has become one of the leading renewable alternatives for energy production. One main factor in the diminished performance of a photovoltaic module is partial shading, due to the resulting mismatch conditions in the module. However, it is difficult to understand how a specific PV module reacts to shading in comparison with others, as currently the ability of a module to withstand shading is usually expressed in vague qualitative terms on its datasheet. In this work, the development of a shading tolerability calculator in MATLAB was completed. This tool can relatively easily and quickly calculate the shading tolerability of a module as a numeric parameter (ST), which can then be used for characterization and comparison purposes.

First a MATLAB based model to simulate the IV characteristics of a PV module under different conditions (including partial shading) was developed. The model was developed at a cell level, and was translated to a module level by taking the series connection of cells into account, and modeling the impacts of reverse bias and bypass diodes operation. Validation with experimental data showed errors at Pmpp remained below 4.5%.

Next, the shading scenarios to be considered were defined and developed. The objective was to determine Pmpp of a given PV module under all possible shading scenarios, using the IV simulation model developed. The possible shading scenarios were based on a PV module split into 12 equal sections, and considering two irradiance levels: 100 W/m2 for shaded sections, and 1000 W/m2 for unshaded. To improve the speed of the model, which was an important aim within this project, the existence of equivalent scenarios based on the symmetry of the module was utilised. The Pmpp value was only simulated once for every unique scenario, greatly reducing the required number of simulations and simulation time.

Based on the above, the development of a calculator for the shading tolerability parameter of a PV module was accomplished. The ST values for more than 40 PV modules were calculated, giving ST% values ranging between 22% and 29%. Correlations between different module parameters were explored to see their impact on ST. One main result seen was the impact of bypass diodes on ST, specifically the considerable positive effect of a higher number of bypass diodes. Another was the positive correlation between temperature coefficient of open circuit voltage and ST.

Finally, a case study for the calculation of ST for a half-cell butterfly module was implemented. This involved modeling parallel connections in PV modules, as well as updating the IV simulation model to include this new type of PV module configuration. The ST values for two half-cell butterfly modules were calculated, giving ST% values of around 42%. This was significantly higher than those calculated for the conventional modules, highlighting the improved shading tolerance of half-cell butterfly modules. The adaptability of this model to be able to calculate the shading tolerability of any type of configuration of PV module was also demonstrated through this case study, paving the way for future research.

With the replacements of coal and nuclear plants with renewable energy sources such as Type-3 and Type-4 wind turbines and photovoltaic system, the fault current levels of the electrical power system become lower. This leads to a weakened ability of the commercial distance relays to detect fault currents. Therefore, new fault detection algorithms have been developed based on different approaches with the intention of raising the ability to detect faults under different circumstances. Among them, Stockwell Transform has been proved to be a useful tool to determine the occurrence of faults. This thesis presents an FPGA implementation of one of the newly developed S-Transform-based fault detection system on Zynq device. The conceptual methods of building an IEC communication interface to connect the system to an RTDS are investigated.
The algorithm on hardware is implemented in fixed-point representation, fully parameterized, and fully pipelined with the operation frequency at 100MHz. The final implementation is able to provide the result within 570ns. The hardware implementation of the S-Transform-based fault detection system is tested with simulations proving it can perform identically with the MATLAB model of itself.

The range anxiety and relatively long charging time issues of electric vehicles (EVs) have boosted the development of fast charging technology. With charging light EVs being the main focus in the past decade, a trend of promoting the charging infrastructures dedicated to heavy-duty EVs (HDEVs) such as E-trucks, and Ebuses has emerged to further the electrification of global transportation. Accordingly, the market is calling for advantageous standards, architectures, and power electronic circuits specialized in the fast charging of HDEVs. For the charging of HDEVs, the power rating of chargers can reach an ultra-high-power level (>1 MW) to ensure a charging time comparable to the refueling time of internal combustion engine (ICE) vehicles. At this power rating, the classic full power processing (FPP) two-stage AC-DC plus DC-DC architecture has limited space for improvement in terms of the efficiency and effective cost of the charger circuits.
This thesis proposes a solution to the HDEV fast charger topologies. Firstly, the
state-of-the-art EV fast charging technology, concepts of the hybrid rectifier, and partial power processing (PPP), which could be beneficial in advancing
the charging architecture are reviewed. Based on the results of the literature review, a new unidirectional Input-Parallel-Output-Series (IPOS) three-phase hybrid rectifer topology is proposed and analyzed. This topology is derived from
the Input-Parallel-Output-Parallel (IPOP) hybrid rectifier in [1] by connecting the
DC-links in series instead of in parallel. The IPOS topology is beneficial at ultrahigh power rating to interface heavy-duty EV batteries which require a high and wide output voltage range, enabling the system to deliver an output voltage range of 800∼1500 V to interface the next-generation of EV batteries with available 600/1200V commercial semiconductors. Besides, the proposed topology is efficient, cost-effective, and scalable with the grid input current harmonic components in compliance with the IEEE-519 standard. The benefits of the IPOS topology are supported by circuit derivation, control strategy, analytical modelling, simulation, and experimental verification of the current modulation technique.
Index terms— fast charging, hybrid rectifier, partial power processing, power factor correction, AC–DC converter

The growing demand for electricity and the importance of decarbonization have forced to transition from fossil fuels to sustainable sources of energy like wind and solar. Currently, the universal power mix remains dominated by fossil fuels but plans are in motion to achieve the target set for the upcoming years. It involves grid expansion and the addition of new elements in the form of Distributed Energy Resources(DERs). This has an influence on the performance of the complete power system. To allow an increasing penetration level of
DG(Distributed Generations) without causing protection problems or unacceptable power flows and fault levels, the impact of DG has to be researched for a secured future grid.
The protection system of the power system is an aspect that will be significantly affected by the continuous integration of Distributed generation sources. For this reason, it is crucial to develop and validate smart protection solutions for future power systems in order to avoid catastrophic blackouts. In order to overcome the shortcomings, Synchrophasor systems can be used for real-time wide area protection and control. The real-time implementation reflects a smart protection scheme, using smart hardware such as a Phasor measurement Unit (PMU). By developing a suitable algorithm that can be used for decision-making
in case of an event on the transmission lines. It coherently helps in faster restoration of the transmission lines operation. Smart protection solutions will help in strengthening the protection system and will allow more flexibility in the coming years.

Thin-film flexible solar panels can be utilized on many surfaces where conventional solar panels are hard to be used such as side walls of buildings, ship roofs or curved surfaces. In conventional solar cells, glass is used to protect the panels from external damage. However due to its heavy weight and rigidity, glass is not an option for thin-film flexible solar cells. HyET Solar, a company based in the Netherlands that produces flexible thin-film solar cells uses a transparent foil produced using a roll-to-roll process to encapsulate and protect their solar panels. In order to reduce the amount of materials used and cut the costs, a thinner foil is being developed. Producing the thinner foil in a roll-to-roll process causes different defects in the foil, among which half sinusoidal waves forming mostly in the bottom side of the foil, these waves are called wrinkles. The process of manufacturing the top encapsulant layer involves changing temperatures and mechanical stresses applied on the foil. Therefore, two models were developed to understand the effect of three process parameters (web force, web speed and temperatures of each production zone) on wrinkle formation. First, a thermal model of the process using ANSYS program was developed to understand the temperature profile of the produced foil along the process. Then, a mechanical model that uses the output of the thermal model and the applied mechanical forces to study the effect of the investigated production parameters on wrinkle formation was worked out. The results show that operating at higher temperatures and reducing the thickness of the foil are directly responsible for decreasing the threshold of the critical stress that causes wrinkle formation and thus reducing the range and the magnitude of the force to 1.4 N is needed to perform the process without forming wrinkles in the foil. Varying web speed between 0.3 m/min and 3m/min is found to have a minor effect when varied under high temperatures. Finally, decreasing the temperature of the first and second zones by 10 °C is found to extend the range of the web force that can be applied. Performing the process under lower temperatures or reducing the mechanical forces that act on the foil will reduce wrinkle formation in the developed foil; web speed should not be considered in mitigating wrinkle formation.

Intelligent Electronic Devices (IEDs) serve as the foundation of substation automation system. Many testing cases have discussed the performance of implementing IEC 61850 in IEDs manufactured by different vendors. However, the procedures of configuring an IED and mapping it with the power network model are not summarized. This project aims to provide the configuring procedures of a distance relay using IEC 61850 protocols, and test if the relay can correctly operate a circuit breaker modelled in Real Time Digital Simulator (RTDS). The communication between relay and circuit breaker is realized by GOOSE, SV and MMS services embedded in the GTNET card. Two testing cases are performed to illustrate that the closed-loop testing using IEC61850-configured relay is feasible in RTDS environment. The thesis is developed as guidelines for future lab work and teaching materials.

Because of increasing awareness amongst people that 퐶푂2 emissions are impacting our environment and climate negatively, governments around the world are taking an increasing amount of measures to try and mitigate this. The transportation sector is identified as one of the sectors whose pollution will only grow in the future. This particular sector also offers lots of possibilities for improvement, particularly the public transport sector. European governments are moving towards an entire zeroemission fleet by 2030. This requires a rapid electrification of the current public transport infrastructure. A feasibility study is performed to determine if a overnight charging system, opportunity charging system or flash charging system can be implemented in the city of Arnhem. First the energy consumption is estimated by taking into account route and temperature variations. This is used to estimate the number of buses overnight charging system would need. Next the system is expanded to a opportunity charging system where the location of chargers, the number of chargers and the charge power are evaluated. Also, strategies for extreme weather conditions are evaluated. Next the system is further expanded into a flash charging system to evaluate charge power with the addition of more chargers. Finally a preliminary cost analysis is performed. A overnight charging system would require quadruple the amount of regular buses. A opportunity charging system with two charger is sufficient to service the route without extra vehicles. A flash charging system offers no real benefit beyond opportunity, marginally better battery capacity against more chargers. The cost analysis shows the 2 and 3 charger opportunity charging systems as the most cost efficient.