Transmission system-level studies face a growing challenge: the distribution networks they interface with are no longer passive. The rapid expansion of rooftop solar, heat pumps, electric vehicles, and other power-electronic-interfaced devices has fundamentally changed how distribution systems behave during disturbances, making the simplified load representations that have long served as industry standard increasingly unreliable.

This thesis develops a methodology for constructing location-specific and time-dependent aggregated load models suitable for transmission-level dynamic stability studies. Working within the Composite Load Model (CLM) framework, residential, industrial, and commercial load profiles are built from the ground up using end-use decomposition — combining publicly available Dutch and proxy datasets to derive time-varying CLM parameters across different sectors. The resulting models reflect genuine differences in load composition driven by time of day, season, and sector-specific process characteristics.

A sensitivity analysis of the CLM reveals that induction motor dynamics dominate voltage recovery behaviour under fault conditions. Static load fractions improve post-fault recovery, while power-electronic components are shown to influence system behaviour mainly through their protection and reconnection logic rather than intrinsic electrical properties. Multivariate analysis confirms that these effects are strongly nonlinear and cannot be adequately captured by first-order regression models.

To manage the dimensionality of temporal variability, K-means clustering is applied to compress thousands of hourly operating states into a small number of representative CLM parameter sets. Finally, a node importance assessment based on the Dutch transmission network admittance and impedance matrices is developed, showing that electrical distance to generating units outperforms purely topological centrality measures as a predictor of dynamic voltage rate of change. Together, these contributions provide a scalable and reproducible framework for parameterising distribution system equivalents in large-scale transmission simulations.

As the European grid transitions towards renewable energy targets, new system stability phenomena are being observed through the electrical power system. The share of renewable generation is growing quickly as synchronous machine-based power plants are phased out. Unlike traditional synchronous machine plants, these Inverter-Based Resources (IBRs) do not provide inherent synchronous mechanical inertia. Consequently, the overall system inertia is decreasing, posing a threat to the frequency stability of the system. This trend is observed worldwide and addressed by organisations such as ENTSO-E through the introduction of future minimum inertia thresholds.

Grid-forming (GFM) technologies have emerged as a solution, providing an immediate active power support after a disturbance, via control methods. These technologies enable IBRs to contribute to frequency stability and mitigate the Rate of Change of Frequency (RoCoF).
The share of distributed energy resources has also grown, with utility-scale renewable Power Park Modules (PPMs) connected to the Medium Voltage (MV) network. These PPMs could help unlock further active power frequency support from the MV network. However, whether this support effectively supports the transmission system remains insufficiently explored.

This thesis assesses the effectiveness of synthetic inertia provided to the transmission network by GFM-controlled IBRs connected at the MV level. The study explores the metrics to assess the effectiveness of the synthetic inertia at the MV-HV interface, investigates the technical constraints of the provision from the distribution-connected resources and offers mitigation measures. Additionally, the comparison of the synthetic inertia support from the HV and MV-connected GFM assets is done.

Firstly, using DIgSILENT PowerFactory, a test benchmark is developed, where the response of a storage PPM with grid-forming controls is evaluated under different disturbances, in order to tune the GFM dynamic models and ensure compliance with grid code requirements. To test the synthetic inertia support of PPMs in a realistic model, a combined transmission and distribution system model is developed from an initial model, which has been adjusted to represent the Dutch grid characteristics. Multiple scenarios and disturbances are simulated with the GFM PPM connected at various locations within the MV network to explore the limits of synthetic inertia support.

The results demonstrate that for a frequency disturbance, the RoCoF and the frequency nadir/zenith improve regardless of the PPM connection point. However, the magnitude of the improvement is dependent on the available active power headroom and the current capabilities of the PPM. A critical limitation was observed regarding the parallel provision of active and reactive power when the PPM is connected to the MV grid. For connection points far from the point of interconnection, voltage stability became more important, as MV buses are more sensitive to active/reactive power injection. During large frequency disturbances, the PPM's active power and reactive power demand grew, which led to current limits being hit, as the PPM sustains the active and reactive current. This suggested a need to enhance voltage and reactive power control or alternative voltage stability methods to support the voltage during frequency disturbances for distribution-connected grid-forming units.

Greenhouses in horticultural MV grids face a transition to meet their heat demand with sustainable heat sources; however, the effect of the transition on the network stress is unknown.
This research simulates the dispatch of greenhouses under 3 different transition scenarios: Full geothermal, Mixed commodity, and Full Power-to-heat. The dispatch control of the greenhouse is based on the day-ahead electricity prices, gas prices, and strategic position on other associated greenhouse markets. Network parameters of an MV grid case study with 29 greenhouses were calculated based on their power exchange. For the calculation, a numerical solver from another research was used. Network simulations show a transition from feed-in to consumption behaviour for all future scenarios. This behaviour change is associated with a decrease in CHP dispatch, which is strongest for the geothermal scenario. The P2H scenario mainly shows large single peak consumptions for the months with high heat demand caused by the dispatch of P2H assets at the same time instants. The mixed commodity scenario has the best voltage and current values of the three scenarios. This research highlights the importance of decentralized power generation by the CHP unit to compensate for the high electricity demand of the artificial lighting.

This thesis presents an implementation method for optimizing the external geometric dimensions of an existing wireless power transfer (WPT) coil through multi-objective optimization. Wireless charging systems have been widely applied in daily electrical devices, and the trade-off between the geometric dimensions of the charging system, its charging efficiency, and power transfer capability is a key challenge faced by designers and manufacturers. During the design process, the evaluation methods for the power, losses, weight, and size of wireless charging coils significantly influence the product design cycle as well as the labor and time expenses associated with the design process. Based on an existing WPT coil sketch, this thesis designs and verifies the feasibility of implementing a multi-objective optimization method. The proposed optimization method is developed based on given power transfer requirements and external dimension constraints. A 3D geometric model is reconstructed using the SALOME open-source modeling platform, where meshing is performed to prepare the geometry for finite element analysis (FEA). The ElmerFEM open-source finite element solver is then employed to evaluate the coil's performance from multiple perspectives. To achieve large-scale iterative optimization for a single performance evaluation, a multi-objective constrained optimization framework is formulated in a Python environment, where constraint equations are defined and deployed using Pymoo. To address the challenges encountered in the implementation of this design method, this thesis primarily considers two key aspects. The first is the automated performance evaluation of a given coil geometry using Python. Given a set of geometric parameters, SALOME can be automated using Python scripts to generate the geometric model and perform mesh generation through a descriptive approach. The generated mesh files are then processed by the ElmerFEM solver, which, supported by SIF configuration files, computes the required physical quantities for performance evaluation. The obtained physical quantities are refined through a proposed computational method to extract the objective data necessary for multi-objective optimization. The second aspect is the multi-objective optimization of coil dimensions using Pymoo. Pymoo is a well-established open-source multi-objective optimization framework. It enables designers to define problems, establish constraints, and formulate quantitative equations, thereby integrating and binding optimization cases with real-world applications. By leveraging this framework, the desired optimization design is effectively achieved.

This thesis investigates how heavy-duty vehicle fleet electrification can be achieved cost-effectively under energy grid constraints. A scenario-based modelling approach combines solar generation, battery energy storage, and energy management to evaluate different charging strategies across multiple deployment phases. Realistic charging demand profiles are derived from historical fleet operations to ensure operational feasibility.

This master’s thesis investigates the feasibility of retrofilling existing L-SEP Gas Insulated Switchgear (GIS). This is motivated by the European F-Gas regulations phasing out the usage of Sulphur Hexafluoride (𝑆𝐹6) due to its large Global Warming Potential (GWP). Retrofilling the L-SEP GIS with a dielectrically weaker insulation gas is a two-pronged problem. One side is on a component level, where the physical required alterations are investigated to obtain a new withstand voltage based upon alternative insulation gas. The other side is a system based study, where the grid of Stedin is examined on what transient overvoltages can occur. The latter part is the focus of this thesis and is important as some locations might stress the L-SEP to its rated maximum withstand voltage, not allow for retrofill. The research methodology involves devolvement and investigation of the key transient origin applicable to the Stedin grid by usage of the ATP-EMTP software. An analysis of transient origins identified fault clearing as the highest priority for investigation. Key components (such as cables and transformers) were identified and represented using frequency dependent models such as the ULM and BCTRAN Grey box model. Both of which were tuned and validated using theory, measurement data and datasheets. A sensitivity analysis was then performed for differing fault locations and component parameters to identify the primary drivers of the maximum transient overvoltages. The results show that the magnitude of the overvoltages are governed by grid earthing configuration and total shunt capacitance on the source side of the breaker. Non effectively earthed systems consistently produce higher overvoltages due to a large pole clearing factor. Furthermore, larger parallel capacitance reduces circuit damping which increases the contribution of the oscillatory part to the overvoltage. The highest simulated transient overvoltage was simulated to be a phase to phase overvoltage. In the case of a non effectively earthed systems with very low damping, where the oscillations of different phases align in opposition. This study concludes that the worst case transient overvoltages remain well below the L-SEPs (rated at 72.5kV) rated lightning withstand voltage of 325kVp for 𝑆𝐹6. This implies that the possibility of retrofilling the GIS with weaker insulation gas (which lowers the withstand voltage) might be possible. In order for this to be confirmed, tests must be done on the altered GIS to find the new withstand voltage for the alternative gas. To improve the grid overvoltages remedial actions can be taken such as improving grid earthing and strategic installation of surge arresters.

The study presents the design, calibration, and testing of capacitive soil moisture sensors in laboratory conditions using construction sand. Five different sensor prototypes with different frequencies and designs were tested under four conditions: base case (tap water), low salinity (4.0 dS/m), high salinity (15.7 dS/m), and fertilizer addition. Known water volumes were added to a fixed volume of soil to establish reference volumetric water content (VWC), against which sensor outputs were calibrated by second-order polynomial fits. Each sensor's performance was evaluated using root-mean-square error (RMSE) and coefficient of determination R², and compared to a commercial TEROS 12 sensor. The prototype sensors showed good accuracy, with RMSEs ranging from 0.92% to 6.33% VWC, and with R² values between 0.763 and 0.995. The TEROS 12 showed larger errors, with RMSEs between 6.20% and 11.93% and R² values from 0.157 to 0.773. While the results are limited to laboratory conditions, they show that well-calibrated, low-cost capacitive designs can rival or exceed commercial sensor accuracy. Future work should consider testing at higher operating frequencies and using soil types that are more relevant to the agricultural sector.

With the rise of greenhouse gasses, increasing environmental concerns and pollution, solutions to a cleaner and more sustainable world are demanded. This thesis contributes to a step towards a cleaner and more sustainable planet Earth. Road transportation has a relatively high contribution to greenhouse gas emissions. A promising approach to lower these emissions is to use electric vehicles(EVs) instead of traditional combustion engine vehicles for road transport.
However, EVs come with their challenges. In general, they have long charging time, introduce range anxiety and have a higher initial cost compared to combustion engine vehicles. By introducing dynamic wireless charging(DWC), these challenges will be eliminated/mitigated. In a scenario in which an EV is charged by using DWC, the EV can continue its journey on the road while its charging. However, due to the dynamic behavior of the mutual inductance, between the transmitting and receiving coil, the output power will not be constant, while for charging a battery a stable output power is required. Therefore, it is necessary to stabilize the power.
There are several methods to stabilize the power. This thesis will provide a comparative analysis of three methods to stabilize power which are, stabilizing the power by using a buck converter, an inverter or an active rectifier. Three different models are constructed in MATLAB Simulink in which each model contains the dynamic wireless power transfer (DWPT) circuit and one of the mentioned circuits to stabilize the output power. The circuits are compared based on five characteristics, namely, voltage ripple, space efficiency, voltage regulation, modulation complexity and start-up time. According to the results the active rectifier is the most suitable circuit to stabilize the output power of a DWC system.