There will soon be a huge influx of EV chargers required in the coming years. Therefore it is important to find out the lifetime of EV chargers like the DC Fast Charger for business cases. These chargers are a combination of multiple power converters to help regulate the grid AC voltage to something that can be used to charge the battery. Multiple Industrial surveys have shown that the most vulnerable parts of power converters are the power semiconductors used inside them. Moreover, research shows that most of the failure in these EV chargers is due to thermal cycling which causes thermo-mechanical fatigue. While there are studies that estimate the lifetime of these semiconductors, it is seldom done in the context of EV charging load profiles. These EV charging load profiles are responsible for long-term power cycling contrary to short-term power cycling which is generally done to estimate the lifetime of the semiconductors. This thesis shall thus choose a popular DC Fast Charger power converter, feed in a load profile and analyse the effects of thermal degradation of the switches and rectifier diodes present in the circuit. This data will then be used to make an estimate of how long the whole power converter will last thus leading to the lifetime of the DC Fast Charger.

The increasing adoption of renewable energy sources, particularly photovoltaic (PV) systems in residential sectors has raised important energy balancing challenges due to the intermittent nature of energy generation. To address these challenges and prioritize cost savings for residential consumers, this research investigates the integration of battery energy storage systems (BESS) and dynamic pricing strategies through an intelligent energy management system (EMS). Given the stochastic nature of PV generation, market prices, and load profile it is still challenging to achieve optimal control. Therefore Reinforcement Learning (RL)-based EMS is proposed in this research to make real-time optimal control decisions. RL is a machine learning approach where an agent learns to make decisions by interacting with an environment to maximize cumulative rewards. In this study, a deep deterministic policy gradient (DDPG) RL architecture is chosen due to its capability to handle continuous action spaces. In addition, deep learning-based models are employed to forecast uncontrollable load, PV generation and market prices for the integration into the EMS for which Bi-directional LSTM (Long Short Term Memory) was found to be the most accurate for all three uncertain variables. The DDPG algorithm is trained with data from a single household from the Lucerne region, Switzerland for 30 days and tested for a week. The results showed that compared to a deterministic rule-based approach the RL-based EMS increased cost savings for the end consumer by 14.2% but reduced the benefits for the grid operator to alleviate grid congestion quantified in terms of load factor, peak power consumption and ramping. Further work could be undertaken in testing the model on more extensive data and finding the best trade-off between customer and grid operator benefits.

We are on the verge of a global energy system revolution. By signing and ratifying global treaties, the groundwork for this revolution is laid. The objective is to limit global warming to two degrees Celsius above pre-industrial levels and stabilise greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system, before 2050. This requires a carbon-free electricity system, which implicates that existing fossil sources of electricity need to be replaced by renewable sources. Most of these sources are weather-dependent and follow seasonal patterns. This leads to a variable, uncertain, and uncontrollable electricity supply. Energy system integration is posed as a key concept to provide the much-needed flexibility to the electricity grid and has been the subject of extensive research. However, there still is a considerable need for further research in the field of energy system integration. Part of the research gap is validation and substantiation of the proposed energy system integration policies and investment decisions. An indispensable component for filling the research gap is a numerical model of the energy system. In this context, the author of this thesis developed a numerical model of the Dutch high-voltage electricity grid. The model can be used to analyse proposed energy system integration policies, optimise the electricity system investment decisions, and prioritise the bottlenecks in the electricity system. The model is used to analyse the effects of several power and heating sector integration scenarios for 2050. The model is constructed in the pandapower framework. The framework is coded in the Python programming language. The model parameters are based on open data and the model input is derived from national sector outlooks and the Energy Transition Model from Quintel Intelligence. Due to the unavailability of operational data from the reference system, the accuracy of the model is determined by evaluating the underlying assumptions and performing a sensitivity analysis. Once the model is validated, the effects of power and heating sector integration on the Dutch high-voltage electricity grid are analysed and the bottlenecks are identified. The results show a substantial increase in grid loading. The highest grid loading occurs when a large portion of the heating demand is electrified, and a large portion of the electricity supply is generated by variable renewable energy sources. The bottleneck analysis of power and heating sector integration scenarios presents one of the use cases of the created representative model of the Dutch high-voltage electricity grid. As the model is based on open data, it is the intention of the author to make the model publicly available as well. This allows other entities to perform a broad range of analysis on the electricity system.

With the rise of various renewable energy sources, comes the possibility for combining the different type of sources together to balance their shortcomings. The goal is to find a renewable energy system that can be reliable year-round and be accessible for everyone. This research tries to model such a system. A model of a grid-tied PV-battery-electrolyser-fuel cell power system, which is based on a continuation of a series of master thesis projects, was expanded to include a neighbourhood with a fully electrical load or a combination of electrical and hydrogen loads. This model was developed to answer the following question. What is the techno-economic feasibility of a grid-tied PV-battery-electrolyser-fuel cell power system for a household area in the Netherlands which is either fully electrical or hydrogen integrated? This hybrid system is simulated by using the graphical interface program TRNSYS. The system size of the PV, batteries, electrolyser, fuel cell and hydrogen gas storage tank are optimised by the GenOpt, an add-on for TRNSYS. The optimisation algorithm will try to find the lowest levelised cost of energy(LCOE) while keeping the system self-sufficiency ratio(SSR) around 1 [%]. This will mean that only 1 [%] of the load is allowed to be extracted from the grid. The simulation is based on a neighbourhood that consists of 630 houses located in Pijnacker Netherlands. All houses will be equipped with a roof mounted solar PV system with centralised batteries, electrolyser, fuel cell and a hydrogen storage tank. If needed the model can be extended to include a small solar park next to the neighbourhood. The model will simulate two scenarios for a simulation time of one year, the first being that the neighbourhood is fully electrical and the second for a neighbourhood with integrated hydrogen gas in its consumption. The first one is the base, with only the electrical load demand of houses. Then the load profile will be extended by adding vehicle to the neighbourhood, including the heat demand of the house. These additional load profiles will either be electrical energy based for the fully electrical scenario or hydrogen gas based for the integrated hydrogen scenario. To estimate the economic development of this hybrid system, a price projection of PV, battery, electrolyser, fuel cell, hydrogen heating, heat pumps and inverters components were determined for the years 2020, 2030, 2040 and 2050. a, the cases will all be simulated for these years. The economic analysis will be over the systems lifetime, which is 25 years. Before the cases were simulated the model undertook a sensitivity analysis. From this resulted that the simulation start time can be moved from the 1st of January to the 2nd of March to relief the storage tank of getting depleted at the start of the simulation. A battery discharge constraint was lifted and this led the batteries to provide more energy. A forecasting method was applied to the system that effectively reduced the electrolyser on/off cycles by 60 [%], which increased the lifetime of the electrolyser component. From a technical feasibility analysis of the cases, it resulted that the integrated hydrogen scenario was not technical feasible with the PV system (roof mounted with the PV park) of this model. All the integrated hydrogen scenario cases resulted in a depleted hydrogen storage tank, which forced the system to buy the hydrogen demand externally. The system will rely on an external source more than the allowed 1 [%] (hydrogen gas SSR >> 1 [%]) of the load demand. From the fully electrical scenario the 2020 C-E-(V+H) case resulted not be technical feasible with a SSR value of 2.1 [%]. All the other cases were technical feasible. From an economic and cost perspective, the cases resulted that the LCOE reduced with the years. The lowest LCOE value found was for the C-E-(Base) case, which reduced from 0.44 [€/KWh] in 2020 to 0.21[€/KWh] in 2050. The cost breakdown of the cases resulted in the PV system and the storage tank to be the most expensive components of this system. Due to the fact that the C-H2-(H) case had to buy a significant amount of hydrogen from an external source, this became a significant expensive cost of the system. Comparing the two scenarios resulted that the integrated hydrogen scenario system sizes were smaller, but this is an effect of the system being more eager to buy hydrogen gas then to expand the hydrogen production components. As both scenarios had different SSR values of their respected energy demands, a conclusion of which scenario is more beneficial will be inadequate.

The reliability of power semiconductor devices is an important feature when designing converter, since the semiconductors are prone to failure and a weak link in the system. Power semiconductor devices are susceptible to thermo-mechanical stresses, and should be investigated to make reliable semiconductors. The power losses inside the device resulting in thermal cycling and expanding and contracting the layers of the semiconductors with different rates, are the cause of the thermomechanical stresses. Thermo-mechanical fatigues are the most frequently encountered forms of failure in power devices, e.g. bond wire lift-off, solder cracks, and reconstruction of chip materialization. In this thesis, the end-of-life assessment of the silicon IGBT and silicon-carbide MOSFET are investigated. Specifically the power cycling test can replicate the thermo-mechanical stresses and wear out the device in a couple of weeks [8], [9]. Multple short power cycling tests are executed to find the relationship between the selected parameters and resulting thermal cycle. Furthermore, the thermal response measurements are used to study the thermal behaviour of the semiconductor devices and thermal fatigues. In addition, the thermal model for the test system is arrived, making it possible to create a testbed for the power cycling test for different thermal cycles. Lastly, the end-of-life assessment is executed for 23 days on eight silicon IGBTs.

Lightweight PV modules offer a solution to the constructional weight limitations of rooftops. PV modules made by Solarge are considered as one the lightweight PV module solutions. The aim of this thesis project is to analyse and compare the thermal- and electrical behaviour of the polymer modules with glass modules. Also, the thermal- and electrical behaviour of polymer modules with a white backsheet are compared with polymer module containing a black backsheet. First, an experimental setup was designed and installed. The PV modules selected for the installation were polymer and glass PV modules both containing half-cut cells. The white- and black backsheet polymer modules contained full PV cells. All PV modules had a pre-installation check with separate electroluminescence and indoor I-V measurements to determine the performance values under standard test condtions. The first thermal- and electrical behaviour comparison was performed for the polymer- and glass modules over the period of 1 June till 30 September. It was found that increasing wind speed affects the cell temperature of glass modules most compared to the polymer modules. On the other hand, the level of irradiance affects most the cell temperatures of the polymer modules. Overall, it was found that the solar weighted average cell temperature was higher for the polymer modules, 39.1 - 39.3∘𝐶, compared to the glass modules, 36.9 - 37.2∘𝐶. Regarding the electrical behaviour, it was found that the mean energy yield of the polymer modules was 4.69% lower compared to the mean energy yield of the glass modules. Also the the glass modules had a higher daily performance ratio, 91.5 - 92.2%, compared to the polymer modules, 87.5 - 87.7%. Part of the difference in energy yield and performance ratio origins in the higher cell temperature for the polymer modules. However, a normalised current difference was found as well, that root in optical losses. The second thermal- and electrical behaviour comparison was performed for the white backsheet and black backsheet polymer modules over the period of 1 June till 30 September. It was found that increasing wind speed affects the cell temperature of black backsheet polymer modules most compared to the white backsheet polymer modules. On the other hand, the level of irradiance affects the cell temperatures of the white backsheet- and black backsheet polymer modules with a comparable heating slope. Overall, it was found that the solar weighted average cell temperature was comparable with 8.3 - 38.7∘𝐶 for the white backsheet polymer modules and 38.1 - 38.7∘𝐶 for the black backsheet polymer modules. Regarding the electrical behaviour, it was found that the mean energy yield of the white backsheet polymer modules was 1.54% higher compared to the mean energy yield of the black backsheet polymer modules. Also, the white backsheet polymer modules had a higher daily PR, 87.7 - 89.1%, compared to the black backsheet polymer modules, 86.8 - 87.8%. The small difference in performance was not directly found in the normalised current and voltage. Measurement uncertainties are therefore seen as a possible root for this difference.

Board-level reliability (BLR) looks at the reliability problem in the package and PCB interconnection, which is an important topic in microelectronics. The current criterion in the BLR test is to look if the connection is open, which can only detect the failure and there is no available method that can detect the degradation of the solder joints. This project mainly focuses on the degradation process of solder joints in board-level vibration tests and thermal cycle tests. Special methods and test programs are developed tailored for two test vehicles, and some of the test results are collected and analyzed. Assisted by the failure analysis technique, the physical change of solder joints can be observed. Findings in this study show the parameter shift during the solder joint degradation and also the mathematic model that describes the relationship between the crack of the solder joints and resistance increment.

Remotely operated vehicles (ROV) are used for the inspection, maintenance and repair of submarine and offshore cables, subsea exploration, and rescue operations. ROVs are powered by umbilical cables, which have to withstand electrical, mechanical, and thermal stresses. This thesis investigates the effect of repetitive bending on the insulation properties of ROV umbilical cables for medium voltage. Umbilical cables with XLPE, polypropylene, and HDPE insulation were mechanically aged using a cyclic bend-over-sheave setup, after which the dielectric properties were analysed using electrical breakdown tests and several diagnostic tests, such as partial discharge analysis. The cables with XLPE and HDPE insulation showed delamination of the conductor–insulation interface, which resulted in increased partial discharge activity, a reduced breakdown voltage, and a significantly decreased lifetime. For HDPE, the lifetime power law exponent 𝑛 dropped from 18 to 9 after 23,000 cycles of mechanical ageing. Polypropylene, on the other hand, did not show delamination but an increase in dielectric-bounded cavities with mechanical ageing.

Thin-film solar cells are second-generation solar cells and they are gaining more traction than the first-generation c-Si solar cells. This is due to the advantages they have over conventional solar cells. The advantages are that they are lightweight, flexible, cheaper and also have better aesthetics than conventional solar cells. Thin-film cells are being processed on a flexible aluminium substrate at HyET Solar which is a Netherlands based company. Their processing technique involves depositing thin-film silicon solar cells on a temporary flexible aluminium substrate. The cells are laminated on a plastic carrier foil and the Al substrate is etched away. HyET solar produces tandem and amorphous single-junction solar cells. For their tandem solar cells, the bottom layer is crystalline. Hence, single-junction crystalline silicon cells are developed at TU Delft to incorporate them into the tandem modules at HyET solar. The crystalline silicon cells deposited at TU Delft are characterized using SEM and raman. The cells deposited at Delft are processed at HyET solar and characterized. Upon characterization, the crystalline fraction and deposition rates increase with an increase in deposition power in the intrinsic layer. The crystalline fraction and deposition rate of a cell does not change by changing the cell thickness of the i-layer. The cell characteristics also change with a change in the silane flow rate in the i-layer. The optimal deposition power with an optimal crystalline fraction was 40W and the corresponding silane flow rate was 3.3 sccm. The deposition rate for a 40W deposition power was 0.41 nm/s. Cells deposited using these parameters were then processed at HyET solar. The cells developed at HyET Solar was shunted. The cause of the shunts was critically analyzed and depositing an amorphous n-layer with a thickness of 80nm seemed to get rid of the shunts. The JV characteristics of the cell were not significant under illumination but the cells displayed diode behaviour when measured in the dark (dark JV). All the deposition parameters except for the deposition time (thickness of deposition) have been optimized for an nc-Si single-junction cell. Further dedicated research on thin-film silicon cells can be performed to improve the electrical characteristics of the cell.

Recent studies have shown that energy distribution systems based on hybrid (or parallel)point-to-point AC and DC links are interesting solutions for capacity enhancement andon-line improvement of energy efficiency under specific operating conditions, particularlyfor high power, medium to high voltage levels and long-enough distances, e.g.>5km.Additionally, due to the power controlability provided by the power electronic circuitswithin the DC links the parallel distribution system can be re-configured through GISdisconnectors operating with improved switching performance. In this work this featureis explored and strategies for the system re-configurations are proposed. These aim toprovide a nearly zero current switching for the GIS in order to prevent its deteriorationand to extend the number of maneuvers for the typical GIS lifetime. In fact, the proposed re-configuration strategies rely on the DC bus voltage and powercontrols of a Back-to-Back (B2B) power electronic system constructed with Voltage SourceConverters (VSC). Herein, three-wire three-phase two-level VSCs with thrid-order AC har-monic filters (or LCL filter) are adopted in the B2B system. Moreover, Grid-side CurrentControls (GCC) for the inner/fast control loops of the front- and back-end circuits are im-plemented in order to enhance the system performance against grid disturbances. Herein,a notch filter-based GCC scheme with a harmonic rejection control is proposed. This isable to deliver attenuation to the LCL filter resonances while suppressing the harmonicsin the grid-side currents originated when the AC voltages are distorted. Interestingly,the parallel AC and DC links provides a low impedance path for the zero-sequence com-ponents which can be created by the power electronics, thus the implementation of aZero-sequence Circulating Current (ZSCC) controller becomes necessary for the properoperation of the system. Hence, ZSCC controllers for the VSCs are used, while bothfront- and back-end circuits are modulated with constant switching frequency using theconventional sinusoidal PWM strategy. All in all, results are obtained in both, computational simulations carried out in MAT-LAB/SIMULINK and laboratory experiments performed in a5kVA VSC or a B2B circuit,are used to verify the study and to prove the superior performance of the investigatedand proposed technical concepts. Herein, more specifically for the re-configuration studyof the parallel AC and DC links, the standalone mode control of the receiving-end VSCin the full DC link configuration is investigated and the smooth transition between grid-connected and standalone modes are realized in both simulation and experimental tests.