In the current grid infrastructure, the power flow reaching the limits of the grid capacity induces several problems. A way to circumvent this issue is the introduction of flexibility in order to alleviate the impact on the energy network. However, the estimation of the required flexibility remains a problem in the current state of the art. In this thesis, an approach is proposed to estimate the flexibility of distribution systems by identifying assets based on aggregated transformer measurements. Flexibility can be seen as the ability of the system to adapt to changes coming from demand and generation. Different assets can be available such as solar panels, and heat pumps and have their specificities. The problem thus translates into the identification process in aggregated data. Several steps are important in the process, such as the consumption baseline, the study of the different characteristics of the profiles, and the number of iterations. To allow the accuracy to reach high levels and to match the standards of distribution system operators (DSO), the process requires the minimization of squared error between the data and the chosen profiles. Different cases are investigated and validated prior to the study of the results. For the identification of heat pumps and solar panels, individual approaches have been investigated in the literature. However, the combined identification of assets has not yet been studied. A mixed identification process is proposed in this work, and the method has been tested, reaching a high level of accuracy. Within this new framework aiming at separating the assets, options are proposed to enhance the accuracy of the process.

In an era defined by the rapid evolution of energy technologies and the necessity of sustainable power generation, effective voltage control is a critical component in optimizing the performance of the power distribution grid and the seamless integration of renewable energy sources. This thesis presents the development and evaluation of an adaptive voltage control policy for high voltage to medium voltage transformers aimed at mitigating voltage limit violations in modern power distribution networks.

The motivation for this research arises from the increasing integration of distributed energy resources and the growing complexity of power grids, which require dynamic and robust voltage management strategies. The proposed policy utilizes a voltage control curve, optimized using a genetic algorithm, which systematically identifies the best parameters for the curve to ensure voltage stability and minimize violations across diverse grid configurations.

The methodology involves quasi-dynamic simulations performed on 30 real-world distribution grids, which test the effectiveness of the voltage control curves in maintaining grid stability under varying load and generation conditions. This was done by setting a stricter ±3% voltage limit for the medium voltage grid. Results show an average reduction of 88.54% in voltage limit violations and a 17.19% decrease in the maximum difference between the maximum and minimum voltage levels in the medium voltage grid throughout a complete year (2023). This study highlights the importance of a grid-specific voltage control curve, as every distribution grid exhibited unique voltage regulation needs.

Furthermore, the policy was evaluated under projected grid scenarios, demonstrating sustained effectiveness across two future timeframes: one set five years and the other ten years into the future. In the first scenario (2028), an 80.06% reduction in voltage limit violations was achieved, while the second scenario (2033) still showed a reduction of 62.25%.

Through the genetic algorithm optimization, the voltage control policy adapts to fluctuating grid dynamics, contributing to improved power quality and the successful integration of distributed energy resources. While effective in medium voltage grids, further research is needed to explore the policy’s applicability to low voltage networks and in environments with limited data availability.

The simplicity and universality of the proposed adaptive voltage control strategy make it a practical solution for real-world deployment, as it can be implemented on existing hardware. In contrast, the proposed strategy alone will not be enough to completely eliminate all the voltage stability problems in distribution grids and additional measures are necessary. However, by minimizing voltage violations and improving grid resilience, this work offers a robust framework for voltage management in modern, evolving power distribution networks, particularly in the context of the global energy transition towards sustainable energy sources.

This thesis titled "Addressing voltage sag contribution of an optimally sized Industrial Hybrid Power System" introduces a framework for sizing an industrial Hybrid Power System (HPS) to minimise Cost and CO2 emissions relative to connecting the industrial site directly to the grid with the help of a genetic algorithm, specifically NSGA-II. The framework utilises an Energy Management System (EMS) that is based on a rolling average principle which attempts to restrict the change in grid consumption from one time step to the next. The optimally sized configuration and its new grid consumption profile are analysed in the CIGRE MV Distribution Network to assess the effects of the new consumption profile on the bus voltages. The combination of a rolling average-based EMS and an optimal sizing with NSGA-II resulted in a $47\%$ reduction of the CO2 emissions while not worsening the voltage behaviour in the system (with a focus on voltage sag introduced by large loads).

The integration of Home Energy Management Systems (HEMS) into Taiwan's smart grid infrastructure has been a cornerstone in enhancing energy efficiency. However, uncertainties persisted regarding the extent to which HEMS could effectively bridge the energy efficiency gap. This study investigated HEMS' role as boundary objects, capable of transcending knowledge barriers within complex socio-technical systems. To address these concerns, a comprehensive methodology was employed, guided by a mixed-methods approach comprising a systematic literature review and an interview. The development of the evaluative framework drew insights from the understanding of complex systems and the concept of boundary objects, uncovering the intricate interplay of elements, relationships, and emergent patterns. This framework served to illuminate the nuanced dynamics underlying HEMS adoption, fostering meaning creation and collective efforts, ultimately paving the path for enhanced energy efficiency. The findings elucidated multifaceted interactions between technology, user behaviour, and knowledge boundaries, collectively shaping the potential for energy efficiency enhancement. By amalgamating theoretical insights with practical experiences, the study furnished a comprehensive comprehension of the potential role of HEMS in effectively bridging the energy efficiency gap within Taiwan's evolving smart grid landscape. This research bestowed valuable insights for enhancing energy efficiency and navigating the intricate terrains of energy management, echoing beyond the confines of Taiwan and resonating in the global pursuit of sustainable energy utilisation.

The replacement of conventional generation units with variable renewable energy sources could have a negative impact on the balance of supply and demand of electricity. Moreover, since the variable renewable energy sources are inverter based and therefore decoupled from the grid, the overall grid inertia will decrease. To solve this problem, the traditional mechanical frequency response can be re- placed by synthetic inertial response and fast frequency response (FFR) alternatives from wind turbines. However, there is uncertainty about the order of magnitude of these ancillary services and how these ancillary services will affect the ultimate and fatigue loads on the wind turbine. The aim of the study is to gain an understanding of the extent to which an offshore wind turbine can provide synthetic inertia and fast frequency response and how this affects the fatigue and ultimate loads on the wind turbine.

Simulations were performed in FASTTool to study the response of the IEA 15MW offshore wind turbine using the baseline controller, synthetic inertia controller and FFR controller. The moments at the blade roots and tower base were used to perform a fatigue and ultimate load analysis. Three different grid frequency data sets were used for the grid frequency inputs of the synthetic inertia controller and FFR controller. In addition, the response of the wind turbine was studied at two different response sizes for both the synthetic inertia controller and the FFR controller.

This study showed a significant increase in fatigue damage equivalent load and maximum stresses due to an increase in the response size of the synthetic inertia and FFR controller. The results therefore showed that the extent to which an offshore wind turbine can provide synthetic inertia and FFR depends mainly on the magnitude of the controller response and not on the size of the wind turbine.

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 report focuses on the analysis of a cost-optimal hydrogen network in Europe within the context of an integrated energy system. It addresses the need for understanding the required capacity and spatial distribution of hydrogen infrastructure to meet the growing demand for clean energy carriers. Previous studies often overlook the integration of a hydrogen network and lack optimized designs considering a sector-coupled energy system.

To overcome these limitations, this report models hydrogen pipelines using the Calliope energy system modeling software with the objective of determining the necessary capacity and distribution of a hydrogen grid in Europe under a fully renewable scenario. Modeling was conducted with a spatial resolution of 35 nodes and a temporal resolution of 2 hours over a full year, using the 2018 weather data. The software uses a linear optimization method to determine the optimal configuration of the hydrogen network.

This study formulates several allocation scenarios for electrolysis capacity to examine the capacity and spatial distribution of an optimal hydrogen network under different conditions. It is found that an energy system with hydrogen hubs requires the development of extensive new pipeline infrastructure, while a system with a more balanced distribution of electrolysis across Europe requires less pipeline capacity and relies mostly on repurposed infrastructure. The estimated capacity of the network ranges from 135 to 244 TWkm. This is 40% to 70% lower than what is estimated in the European Hydrogen Backbone (EHB) vision.

In the scenario with hydrogen hubs, the study identifies four hydrogen corridors that align with the vision presented in the EHB report, with Britain, Ireland, Denmark, and Portugal as key hydrogen producers. Furthermore, the analysis highlights the significant role of salt caverns as the predominant storage technology for hydrogen, despite uncertainties surrounding their capacity estimates. The optimal storage capacity in salt caverns ranges from 42 to 178 TWh when accounting for cost and weather uncertainty.

The analysis initially considered a self-sufficient energy system, but the sensitivity to international imports was also considered. To analyze this aspect, hydrogen imports from four North African countries were included. The findings revealed that international imports play a relevant role in shaping the optimal configuration of the hydrogen network. Imports increase the required investment in infrastructure but also reduce hydrogen storage capacity and its associated uncertainty. Changes in the network configuration result in a 6% reduction in total system costs due to decreased renewable energy capacity and reliance on external hydrogen supply.

Overall, this study emphasizes the need for accurate electrolysis allocation estimation, alignment with international import planning, and efficient utilization of storage technologies in the development of hydrogen infrastructures. The findings contribute to informed decision-making and the creation of sustainable hydrogen networks that integrate effectively with renewable energy systems.

As more and more solar panels are installed on households, a problem arises when the power from the solar panels fluctuating throughout the day due to clouds passing over the solar panels. This in turn causes voltage flickers in the household, which can be visible/irritable to the human eye and damage appliances in the household. These voltage flickers can exceed limits set by the IEC standard 61000-3-7 or the visible flicker threshold on the Low Voltage (LV) network set by Qualtech [1]. This problem can be solved by making use of an Energy Storage System (ESS) which delivers active power in order to reduce and avoid the voltage fluctuations above the visible flicker threshold. In this report, a novel control algorithm is designed and implemented in two different ways to control the active power dispatch of the ESS. The main goal for the control algorithm is to reduce or avoid any visible voltage flickers from occurring and minimizing energy usage asmuch as possible in order to open the possibility for a Supercapacitor Energy Storage System (SESS) application in the future. For this, a power to energy ratio of higher than 70 is needed to achieve this. The primary control algorithm makes use of a moving average with a weight distribution that is optimised for smoothness and accuracy. Furthermore, extra layers of control was added to the control algorithm tominimize energy usage. The first implementation of the control algorithm, called power control, makes use of the Photovoltaic (PV) system output power to dispatch the appropriate amount of power from the ESS. The second implementation, called voltage control, makes use of the measured voltage at Point of Common Coupling (PCC) to dispatch the ESS power. Simulation results using pre-existing PV system data showed that the power control implementation was not able to fully eradicate all of the measured visible and annoying voltage flickers. The voltage control implementation was able to do so within the window of operation. Furthermore, simulation results showed that the energy usage from the control algorithm with a power control implementation uses 87% percent less energy than a control algorithm using conventional moving average. The energy usage from the control algorithm with a voltage control implementation uses 95% less energy than the conventional moving average control algorithm. Furthermore, the power to energy ratio of the control algorithm with a power control implementation was around 98.9 and with a voltage control implementation the power to energy ratio was around 190.2. This shows a clear implementation of a SESS in the future. Two different experimental setups were built and commissioned. The first setup having the Battery Energy Storage System (BESS) connected via an inverter on the same Alternating Current (AC) bus with the PV system. The second setup has the BESS connected on the same Direct Current (DC) bus with the PV system which is then connected to an inverter. Experiment results showed that the DC connected ESS experiment setup operating in power control mode had the best performance in terms of avoiding any visible voltage flickers from occurring. While the AC experimental setup and mode of operation (voltage and power control mode) did not operate properly due to the slow inverter response time. In terms of energy usage, both experimental setups had very low ESS energy usage. Although the results showed that power to energy ratio from both experimental setups using both power and voltage control did not exceed the set goal of 70 due to the limitations of both experimental setups. Finally, a conclusion based on the results is given with future work and as well as recommendations for the continuation on this research topic.

With the popularity of electrical vehicles (EVs), the demand for EVs charging is also increasing. Compared to traditional wired charging, wireless charging can avoid many safety issues. The efficiency of wireless power transfer (WPT) system is determined by many factors, the coupling factor is one of the most important factors. Therefore, estimating the coupling factor of WPT system is necessary. The research objectives of this work are to review and benchmark different methodologies of coupling factor estimation. Besides, a comprehensive method is selected and simulated. This work is focused on magnetic inductive WPT systems. Five different methodologies of coupling factor estimation for static WPT system and one methodology for dynamic WPT system is reviewed and analyzed. The methodology that uses alternative capacitors to estimate the coupling factor of a static WPT system is analyzed in detail. By using the zero crossing unit, the primary side and secondary side of WPT system are under full resonant. The WPT system will work in two different modes by changing the primary side capacitance. The two sets of circuit parameters will be recorded and calculated by a PLL unit. Based on theoretical analysis and the calculated parameter, the load and mutual inductance of WPT system can be identified. Therefore, the value of the coupling factor can be determined. The accuracy of coupling factor estimation of this methodology is higher than 97 %.
Compared to the literature that proposed this methodology, this work made a sensitivity study. The circuit parameters are made to fluctuate in a certain range. The accuracy of estimation of mutual inductance is still higher than 95% when the primary side resistance, secondary side resistance and load fluctuate. However, the system becomes unstable when the primary side capacitance, inductance and secondary side inductance fluctuate. The reason is that when the capacitance and inductance change, the operating frequency will deviate from the resonant frequency. However, the mutual inductance identification unit is not able to detect this deviation. If the deviation of circuit parameters is updated, the accuracy of coupling factor estimation will remain at about 97%.

The increasing penetration of the distributed energy sources and the increasing load on the AC grid demands for integration of DC grids in AC distribution network. This has resulted in the requirement of power electronic converters such as DC/AC converters. For different operating conditions of the DC/AC converter it is not recommended for the converter to operate in open loop. Hence, while designing the control for the converter there are challenges such as the presence of unbalance on the grid leading to higher losses, offsetting of AC voltages at the output and grounding of the converter leading to higher common mode voltage and currents. This thesis explores the control strategy that can be implemented on the converter to mitigate the unbalance in different operating conditions and compares different modulation techniques to reduce the common mode voltage and currents.
To begin with the islanded operation is considered for the converter and the voltage control is implemented on this type of converter. Further a modification on this type of control is proposed for the operation of converter under overcurrent scenario. Subsequently the control strategy for grid connected operation is analyzed such that the issue of unbalanced currents on the grid is mitigated. Three different operating modes are considered under grid connected operation for validating the control strategy proposed. Following the controlled operation in islanded and grid connected scenario, the active methods for reducing the common mode voltage are reviewed by comparing different modulation techniques.
On the discussed control strategies for different operating conditions of the DC/AC converters, an optimized implementation of the control on the microcontroller is presented. Other functionalities such as protection of the converter against unwanted actions is investigated through implementation of state machine. The results of the controlled DC/AC converter operating in islanded operation is presented and modifications in the existing PCB are discussed to make it compatible to operate under grid connected condition. The operation of control strategies implemented is validated for the real time application of the converter with unbalanced load conditions.

We are in the middle of a transition to zero-emission mobility. The European Union has set high targets for zero-emission bus sales. Many European local governments and public-transit operators are looking to replace their GHG-emitting diesel/gas bus fleets with clean alternatives. One such alternative is In Motion Charging (IMC) technology for trolleybuses. With this technology trolleybuses are able to charge an on-board traction battery whilst in motion and connected to the overhead wires. This makes it possible for these buses to extend their range outside the trolleygrid infrastructure. These IMC buses can replace diesel/gas buses. IMC is of particular interest for municipalities that currently have a functioning trolleybus fleet and infrastructure. Existing infrastructures are however not built with the increased power demand of IMC buses in mind. A good understanding of the power demand of IMC buses and the limits of a trolleygrid is necessary before implementing IMC buses. The explanatory research that is presented in this report aims to give insight in the design factors that influence the feasibility of adding in-motion charging buses to an existing trolleybus network. It does so by first explaining the difference in energy consumption between IMC buses and regular trolleybuses through simulations. Next, by performing a case study on the Arnhem trolleygrid the effect of IMC buses on the trolleygrid is discovered. The results of the energy consumption comparison indicate that there is promising potential for IMC implementation. It shows that there is a large margin in which IMC buses can make more efficient use of their regenerative energy compared to their regular trolleybus counterparts. It also shows that there are large degrees of freedom in IMC bus implementation leaving room for errors. The Arnhem case study uncovers where exactly these errors lie by looking at potential power demand, minimum voltage and maximum current limit breaches on the network. As long as these breaches can be mitigated through smart charging strategies there is a lot of promise for IMC bus implementation on existing trolleygrid infrastructures.

State estimation (SE) is a crucial tool for power system state monitoring since the control center requires a process to deal with a large number of imprecise measurements. Several SE methods have been applied and developed for the electric power system in the transmission level in the past several decades. Meanwhile, SE for the distribution level remained in the background for a long time since the distribution networks were mainly radial with uni-directional power flows, making classical monitoring and control functions sufficient. Recently, due to the liberalization of the energy market, growing penetration of distributed generation, mainly renewable energy sources, and distributed energy resources such as electric vehicles, the distribution system has been gradually changing from passive into active grids. This requires more sophisticated monitoring and control of the distribution network via a distribution management system (DMS) to ensure optimal integration and maximize the grid hosting capacity. Since one of the key functions of DMS for real-time operation is the SE procedure, this calls for the following: (i) development of SE techniques for the distribution level, so-called distribution system state estimation (DSSE); (ii) more deployment of time-synchronized devices like phasor measurement units (PMU) that can directly measure and acquire accurate and time-aligned phasors with typical refresh rates up to 20-60 times per second.

Two types of DSSE algorithms were developed and implemented on the real-life 50 kV ring distribution grid composed of PMU devices by using the real-time simulation platform. The first is a static approach. The problem is formulated as a WLS problem to be solved based on the iterative Newton method, known as static state estimation (SSE). The second is a dynamic approach, which is more advanced, known as the forecasting-aided state estimation (FASE). It is one of the particular applications of the dynamic state estimation (DSE) concept based on the quasi-steady-state operating conditions. The dynamic formulation is solved using the extended Kalman filter (EKF) technique. This research aims to implement distribution system state estimation (DSSE) algorithms coupled with the auxiliary function, the so-called anomaly detection discrimination and identification (ADDI), into the distribution network. Both normal and abnormal operation scenarios of the power system are simulated to validate the algorithms.

The results reveal that the FASE is superior to the SSE algorithm in terms of estimation accuracy and computational time under normal operating conditions. However, under abnormal conditions, if there is no ADDI module, the performances of both algorithms are degraded significantly due to erroneous measurements. The FASE algorithm loses the system states' trajectory when sudden load change occurs. These issues point out the necessity of using the ADDI module against possible disturbances in real-life networks. In the end, the results show that the proposed FASE algorithm coupled with the ADDI module can accurately estimate the states under both normal and abnormal operations. One significant contribution is that the proposed algorithm can perform adequately fast so that it can process every high-speed measurement from PMU devices.

Traditional trains, with steel rails and wheels, have been around for centuries. The very good energy efficiency of steel-wheeled trains is one of the reasons that they are one of the more promising transportation modes in the future, where energy conservation becomes more and more important. Furthermore, electric trains are able to efficiently use sustainable power. They usually power their on-board motors by a sliding contact, with an overhead catenary wire or a 'third' power rail. However, trains using a linear motor have also emerged. These have several advantages: the amount of moving parts is reduced and the amount of traction force available is independent of the slipperiness of the tracks. Some systems still use a 'third rail' for power transfer however, which is a sensitive moving part and limits the train speed. Furthermore, arcs can cause damage under reduced air pressure. This may be eliminated using a linear doubly-fed induction machine (DFIM), which may be able to simultaneously propel and provide power to the train. The latter can be used to charge an on-board battery, which can provide the energy to keep the velocity constant between the stations, where active tracks may be omitted to save costs.

In this thesis, the use of a DFIM for a train application has been reviewed. A linear DFIM has been designed in a previous work \cite{Becetti2021}, whose parameters are used in this thesis to simulate the concept. A controller is to be designed which allows the prescribed use of simultaneous propelling and charging. This thesis explores the requirements and possible controller candidates for the train application, which is followed by simulation and laboratory testing.

The application for a vehicle drive provides unique objectives and restrictions. One of the most restricting elements is that preferably no trackside (stator) quantities should be required for the control of the DFIM. After all, requiring trackside quantities would require a critical very dependable communication link between the track and vehicle. For this reason, estimation methods have been selected to control the vehicle with only vehicle-side measurements.

Three main categories of controllers have been identified: field-oriented control, direct torque control, and model predictive control. It has been found that each controller family has its advantages and disadvantages, and the best controller depends on the final system design of the train system. Field oriented controllers have the lowest current ripple, and can therefore be very predictable and efficient. Direct torque control is best used if it becomes very important to keep the final algorithm very simple. A model predictive controller excels if additional constraints are required, such as when using a multilevel inverter that requires balancing. This thesis provides a selection that can be used to make a decision in a later stage.

The operational principle of the train with the DFIM has been verified with a simplified laboratory test. A rotary DFIM has been powered with a fixed grid frequency-powered stator and an inverter-controlled rotor. Using a simplified control algorithm, the experiments have verified that the DFIM can be used to charge the vehicle at a high efficiency of up to 85\%, and that the DFIM can indeed be used to simultaneously charge the vehicle and provide a tractive force. Additionally, a Simulink-simulation is performed where the performance of the linear DFIM design is validated. It has been concluded that the DFIM is an attractive candidate for use with a linear motor-driven train since it can indeed fulfil the roles of both motor and charger simultaneously and efficiently.

In the transmission and distribution network of the future, there is expected to be a mix of both Alternating Current (AC) and Direct Current (DC). In the high voltage division owing to technical and economic aspects, there is a wider use of High Voltage Direct Current (HVDC) instead of High Voltage Alternating Current (HVAC). However, when observing the medium voltage network, it is noticed that it is completely AC in nature. One major reason for this preference of AC in the medium voltage network is the better know-how of an AC network and the presence of well established and reliable MVAC components and the ability to transform (step up and down) voltage in AC. A switch to Medium Voltage Direct Current (MVDC) is expected as the cost of power electronic components is decreasing with time, and there is an improvement in their performance. Therefore, switching to MVDC would provide advantages in the form of improved transfer capacity and better power control. MVDC grids are debated to be a vital member of the future distribution network. In the present scenario, there is an absence of such an MVDC grid. Thereby, there are also no MVDC accessories available which can be used in such a grid. Therefore, there is also the absence of a testing procedure for the same. CIGRE TB 496 provides the testing strategies for DC cable systems up to 500 kV, but it does not take into consideration the difference between an MVDC system and an HVDC system. The systems may have a striking difference in construction, such as concerning materials. Additionally, there is also a difference concerning max field stresses and thickness of the insulation. The possibility of using the AC accessories for DC application needs to be analysed, and it needs to be verified how such an AC accessory would behave under the influence of prolonged DC stresses. The use of existing MVAC accessories for DC would be beneficial given the high production standards and the voluminous supply chain of MVAC systems. Additionally, this also opens possibilities of reusing existing AC cable system for DC stress. It needs to be noticed that in DC, the field distribution would depend on the conductivity of the material which is different from AC where the field distribution depends on the permittivity of the material. The permittivity of insulation is virtually independent of the temperature. However, conductivity has a strong relation to temperature and electric field, which makes DC field distribution more complex when compared to AC field distribution for any geometry. The test criteria of MVAC and pre-qualification test for HVDC are well known and need to be utilised in proposing and motivating the test sequence and test voltages for the accessories to be used in the future MVDC network. These accessories to be used in this future MVDC cable system needs to be analysed using Finite Element Method (FEM). The field simulations would give identification of locations in the joint which are undergoing maximum stresses during DC application. These maximum values of stresses are used to calculate the voltage life of the system based on electro-thermal life laws. The test results based on the representative testing procedure would help in understanding the performance and lifetime of the cable systems under DC stress. Therefore, to understand all items previously mentioned, a representative testing procedure needs to be proposed and motivated to test the use of existing MVAC accessories in the future MVDC network.

The energy transition is advancing rapidly, and the Dutch electricity grid is changing with it. Increasing shares of variable renewable energy sources create mismatches between electricity supply and demand. These mismatches create a need for large-scale energy storage. Existing large-scale energy storage technologies are pumped hydro energy storage and compressed air energy storage, but their storage potential in the Netherlands is limited. The alternative is to store energy in chemical bonds, for example by producing hydrogen, and regenerate the electricity later. This type of storage is called a Power-to-X-to-Power (PtXtP) system. Power-to-X technologies have existed for a long time. This
report evaluates their potential in an energy storage application. First, PtXtP systems are compared to compressed air energy storage (CAES) and pumped hydro energy storage (PHES). The geographic potential of CAES and PHES in the Netherlands is limited for both technologies, proving large scale energy storage is a challenge to which PtXtP. Next, all PtXtP technologies are investigated and compared based on available literature. The three technologies with the most potential (hydrogen, ammonia and methane) are further investigated. This report gives a current and comprehensive overview of data on PtXtP system components, including amongst others their OPEX, CAPEX, efficiency and energy use. This data was used as input for several models of hydrogen, methane and ammonia storage systems, to determine system cost and performance in a dynamic system. Simulations are run with these PtXtP systems as energy storage technologies for a 1GW wind park. The simulations are used to identify main system bottlenecks, investigate the impact of intermittent use on system performance, and evaluate the potential of a PtXtP storage system. The first important bottleneck is the size of the hydrogen buffer required for operation of the Haber-Bosch reactor and Sabatier reactor. It is as large as or larger than the storage capacity in a hydrogen storage system. The second bottleneck is the size of ammonia and hydrogen fuel cells. The required fuel cell power is 425 MW, which is larger than any current or expected fuel cells. Next the simulations were used to investigate the performance of a PtXtP system as energy storage medium in a VRES system. The first important finding is the tradeoff between system flexibility and system sizing. An ammonia system with 33%-100% flexibility can be 60% smaller than a 0%-100% system, while still processing the same annual amount of hydrogen. Intermittent system use increases the levelized cost of storage significantly, in these models by factor 2.2-4, due to the unchanged CAPEX which must be paid for a reduced system output. The first important finding related to the PtXtP system is that the cost and energy consumption of hydrogen transport and storage are relatively small compared to energy conversion steps. The electrolyser proved to be the system component with the highest cost and energy loss. Finally, the added value of the storage system is significant wind park size reduction. The 1GW wind park size could be reduced by 35% when connected to a hydrogen storage system, while still meeting the same demand. In addition, zero grid exchange can only be achieved when implementing a storage system. With lower shares of grid exchange, storage becomes increasingly more valuable. The overall conclusion drawn is that hydrogen or methane systems seem to have the most potential for energy storage purposes. The report also shows energy storage is necessary, and no alternatives to PtXtP are available in the Netherlands. PtXtP will therefore have to play a large role in the future Dutch electricity grid. However, use of PtXtP storage will increase the price of electricity and several technological developments, mostly scale-ups, are necessary before a PtXtP
system is feasible.

The Netherlands aims to accelerate the energy transition. Accordingly, ambitious targets have been set for the industrial sector. This will require additional investments in the Dutch industry which is expected to reduce the CO2 emissions at limited costs in comparison with other sectors. However, the ambition to reduce the emissions can create a risk of loss of activity and jobs if the industrial businesses prospects are not ensured. Power-to-heat technology provides an opportunity to the industry to reduce the emissions for heating processes. This technology can be implemented in hybrid configurations to ensure the electrification of heat. Hybrid configurations are characterised by their ability to switch between natural gas and electricity which could cost-effectively reduce the emissions consuming electricity at low prices. In this research, a techno-economic evaluation of hybrid boiler systems is performed to analyse the potential of this technology to cost-effectively reduce the CO2 emissions for steam generation in a production process, in 2030. To this end, the operation of hybrid boiler systems was simulated and assessed. The performance of hybrid configurations was compared to alternative options. Finally, the hybrid systems were analysed under different scenarios for 2030. The results for the case study presented, showed that hybrid configurations saved operation costs and reduced the direct CO2 emissions by almost 20%. Therefore, the hybrid boiler could cost-effectively reduce the emissions. However the potential benefits of hybrid boilers are subjected to variation of electricity, natural gas and CO2 prices.

Boost-type power factor correction (PFC) rectifiers can be used in, for example, battery charging systems for Electric Vehicles (EVs). Conventionally available three-phase PFC rectifiers are limited to output 1/3 of the rated power when connected to a single-phase mains. This work presents the research into the single-phase operation of the Belgian rectifier, a novel boost-type PFC rectifier which allows for full power operation in both single- and three-phase operation (relevant for the three-wire split-phase systems in the USA with a maximum power of 19.2 kW). The single-phase AC-to-DC power converter is operated by paralleling and interleaving the three-phase rectifier bridge legs. By using the analysed triangular current mode (TCM) modulation scheme complete zero-voltage switching is achieved over the entire mains period. The power converter is further analysed with respect to the steady-state operation and component-level modelling. The modelling techniques are used to generate the Pareto-front of efficiency versus power density. The optimal design is selected based on the multi-objective requirements, and is a design with 6x interleaving with a boost inductance of 30µH that results in complete soft-switching transitions and achieves an efficiency of 98.42% with a power density of 5.34kW/dm3. After that, the single-phase Belgian rectifier is compared to the conventional six-switch boost PFC rectifier to identify and quantify the benefits. Finally, a closed-loop control model is proposed and implemented on the 19.2 kW, 1.5kW/dm3 hardware demonstrator for the conversion of a 240 V AC input with a maximum rms current of 80 A into a 380 V DC output to verify the single-phase operation of the Belgian PFC rectifier. Experimental results show efficiencies higher than 98% for power levels larger than 3kW.

The charging of a rapidly increasing number of EVs places significant strain on electrical distribution grids. Controlled (’smart’) charging of EVs offers a solution to this problem by shifting the charging of vehicles to the most optimal moments in time. Smart charging is not a completely new research topic; it has a high Technology Readiness Level and some commercial implementations already exist. There is a large amount of literature available that compares the effect of controlled and uncontrolled EV charging on the distribution grid. However, most of this literature is based on pure software simulations using power flow analysis and mathematical models of EV charging behaviour. Experimentally validating these results would require a large number of EVs and a controllable distribution grid, which is costly and unpractical. Therefore, this thesis presents a compromise; a hardware-in-the-loop (HIL) testbed in which the distribution grid is software-based but the EV and EV Supply Equipment (EVSE) is hardware-based. In this report, the design and implementation of the testbed is discussed, as well as results from HIL simulations that compare the effect of controlled and uncontrolled EV charging in a distribution grid. The low-cost HIL testbed presented in this thesis is based upon an OPAL-RT OP5700 Digital Real-Time Simulator (DRTS) which runs a Newton-Raphson power flow analysis of a Dutch distribution grid. The DRTS also interfaces with all other hardware in the testbed. This includes a power amplifier which generates a three-phase grid at the voltage calculated by the power flow analysis. A commercially available EVSE is connected to this power amplifier and supplies power to an emulated EV which consists of communication hardware and two bidirectional back-to-back DC power supplies. These power supplies act as an AC load. Various communication protocols were implemented to exchange information between the different systems in a manner that closely represents commercial EVs. A smart charging algorithm which determines the optimal charging current setpoints in real-time, based on external factors like local load power consumption, solar irradiance and energy prices, was implemented into the testbed. The testbed has subsequently been used to study the effect of uncontrolled and controlled charging on the simulated distribution grid for a total of eight different scenarios. Of these scenarios, one consists of traditional uncontrolled charging and the other seven are with the smart charging algorithm activated. These include firstly a base case, then two scenarios with an inaccurate solar irradiance and local load forecast, a further two scenarios with non-ideal EV charging behaviour, and lastly two scenarios with respectively centralized and decentralized curtailment implemented. In all scenarios, one EV was implemented as hardware and three others as software, so that a comparison could be made. Even under non-ideal conditions, smart charging is found to reduce costs, grid overloads, and voltage deviations with respect to uncontrolled charging. The implemented centralized curtailment is shown to be more effective than decentralized and further reduces voltage deviations in the grid but at a slightly higher cost than without this curtailment. Lastly, based on observations made in the HIL simulation results, recommendations for future work and improvement of the smart charging algorithm are given.

Despite of the technological advancements on renewable energies and integration of those into the grid, there are still around 800 million people who lack access to the electricity. In order to tackle this problem, solar home systems are being deployed especially in rural areas to create units for decentralized energy generation, based on DC microgrid premises. Integration of solar home systems, especially in developing countries, has great positive effects on communities' economic and social conditions.
In line with transition to cleaner energy resources and utilization of these, this thesis has been carried at DC Opportunities RD to facilitate the rural electrification project. Within this project, the thesis focuses on implementation of a general adaptable firmware based on USB Type-C power delivery protocol on several components of modular solar home system.
Firstly, the report analyses the existing solar home systems with their characteristics on power delivery and energy management. The limitations on the existing projects are studied and the main motivation on deploying the firmware is pointed out. The main objective of the thesis is hence is formulated as achieving and implementing the USB Type-C power delivery protocol with data acquisition layer on prototypes of charging station, power banks and charging hub, that is tailored to rural applications. The firmware design topology is followed to take into account the modularity, scalability and applicable to energy management.
The USB Type-C power delivery firmware is developed by studying and adapting two open source packages. Several adaptation layers are developed and the firmware is implemented using micro controllers, from STM32, that are capable of running operating system with no faults, deploying several layers of tasks and state machines. Power delivery library functions are tackled with layers of software architectures and data monitoring and transmission layer is deployed, in order to validate the system as well as the hardware.
Implemented firmware is developed on the prototypes and tests are run with the current editions of the prototype. The energy management layer and formulated test case will be run and tested on March 2020, in the field test in Ethiopia. This field test will provide results and data, thanks to the developed firmware and acquisition system, in order to achieve a step closer to the ultimate goal of the project, which is implementing low voltage DC microgrid in rural areas.

TU Delft, being in the frontier of research and progress in Europe and worldwide, is always interestedin exploring the possibilities of renewable energy production. In that respect, the Facility ManagementDepartment (FMD) of the university approached the Photovoltaic Materials and Devices (PVMD) group,whose research covers a wide area in the renewable energy sector, in order for the solar potential of anextensive available area in the South of the TU Delft Campus to be investigated. This thesis project aimsat shining a light on the latter, while also proposing a best business case scenario for realization.In order to deal with the issue at hand, a complete MATLAB-based modelling tool has been developedfor the simulation and evaluation of PV module and PV system performance. Additionally, a locationsurvey was conducted, which resulted in the recreation of the skyline profile and the study of the reflectivityof the ground. In case of using a bifacial PV module, the PVMD Toolbox can be integrated in theapproach.Using the developed modelling approach, different PV technologies were investigated. The bifacialmono-Si PV modules by LG were found to outperform the competition on yield and cost criteria. Theresults indicated that the best performance is achieved for a tilt of 40^o and an azimuth of 165^o. A sensitivityanalysis was also carried out, based on which a ground clearance height of 1.5 [m] was selected.Furthermore, the results extracted using the modelling tool were cross-validated using the PVMD Toolboxand the System Advisor Model (SAM), showing a satisfactory performance with the maximum deviationsbeing 1.5% and 3%, respectively.Moreover, two different potential loads were studied in conjunction with the solar modules. The firstwas the 1.25 [GWh] annual demand of the EXACT building, closely located to the investigated area. Inthis case a grid-connected PV system was designed with the total amount of modules being calculatedas 2,520. The second was an electrolyzer of a nominal capacity of 1.25 [MW], scheduled to be installedat the Process and Energy (P&E) Department of the university. The electrolyzer was assumed to supplyhydrogen to two fuel cell buses, and its respective PV system was designed both as grid-independent aswell as grid-connected. In the independent approach the total number of required PV modules was foundto be 4,000, while in the grid-connected approach the size of the PV system was chosen similar to theone designed for the EXACT building. Moreover, two hydrogen production strategies, a minimum anda maximum, were investigated. The respective produced hydrogen was found to be 9,100 and 20,619[kg].The choice of the best business case was based on a performance and cost analysis that was conducted.The conclusion drawn from this analysis was that decentralized PV systems have a better performance dueto higher inverter efficiency and lower cable losses, while the centralized approach has a better behaviourcost-wise due to the initial investment being smaller by 2%. Additionally, systems with a higher lifetimeyield better results. All in all, the grid-connected, decentralized, electrolyzer-coupled PV system with themaximum hydrogen production strategy was deemed as the best business case. The initial investment of1.28 [M €] is won back over a period of 5.1 [yr], having an LCoE of 8.2 [cts €/kWh]. The area requiredto fit the PV system is comprised of Zones B1, B2 and B3, which show the greatest potential.