Inertial and Frequency Response of an Offshore Wind Turbine: Effect on Extreme and Fatigue Loads

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...

Optimisation of subwoofer placement using a finite-difference time-domain acoustic simulation

The placement of a subwoofer has significant impact on the quality of its sound reproduction. This paper present a method to optimise subwoofer placement in a room. Resonances caused by room boundaries (called "room modes") cause localised peaks and lows for specific lower frequencies. The goal is to minimize the simulated frequency response...

Topology optimization for suppression of vibrations in suspended structures and achieving dynamic global flatness

In a high-precision system that performs measurements or tooling on a workpiece, alignment of the tool and workpiece is of prime importance. To prevent misalignment, which leads to a loss in accuracy and precision, unwanted vibrations in structures must be attenuated. Topology Optimization (TO) is evolving as a mature design tool that provides...

Frequency support of Non-Synchronous Generation in the Nordic Power System in 2030

his thesis aims to investigate the change in frequency performance of the Nordic Power System in 2030 caused by the replacement of synchronous generation by NSG. To do this, the Nordic Power System is modeled in the simulation software DIgSILENT PowerFactory 2022 SP1 for modeling and simulation. For the Nordic Power system, periods of low demand...

Optimization of Battery Energy Storage System Operation in Distribution Grids

Currently, the main revenue streams for grid connected BESS stem from regulated energy markets, such as Day Ahead Market (DAM) and Primary Frequency Regulation (PFR). Furthermore, BESS have great potential in providing services to network operators, however a clear business case for such functionalities is still missing. Therefore, this research...

Providing Stacked Balancing Services using Wind-Storage systems

In order to decarbonize the electricity grid, renewable energy sources must be utilised in con- junction with energy storage to provide ancillary services, which maintain electricity supply quality, reliability and restorability, whilst remaining aordable. Due to a lack of knowledge about the potential of stacking UK ancillary services and...

Optimal Tuning of Active Power Gradient Control in Multi-Energy HVAC-HVDC Power Systems

Power systems nowadays are experiencing a significant energy transition characterized by the progressive increment of power electronic interfaced units. Voltage source converters are extensively utilized to interconnect renewable energy sources at various transmission levels, facilitate the asynchronous interconnection of system areas through...

Modelling and Simulation of Energy Storage System for Frequency Stability Studies

The frequency stability of the power system is challenged by the high penetration of power electronic interfaced renewable energy sources (RES). This paper investigates the improvements of frequency responses of fully decoupled wind power generators (FDWG) by proposing a novel implementing of ultracapacitors (UC) within a hybrid scheme in real...

Numerical and experimental study on post-buckling skin-stringer separation in butt-joined stiffened thermoplastic panels

So far thermoset based composites have been used in primary aircraft structures, owing to their good performance and vast research on the subject. Recently thermoplastic based composites also gained an increased attention and there is a push towards adopting these for primary aircraft structures as well. This interest for thermoplastic...

Inversion scheme for multichannel impact echo measurements

Conventional imaging techniques from medical ultrasound and seismic imaging are not suitable for multilayered domains where there is no separation between received reflection events. This happens in layered structures where the thickness of the individual layer is small with respect to the induced wavelengths. An example of these structures is...

Hamaker constant and tip radius determination in dynamic atomic force microscopy

Dynamic Atomic Force Microscopy (dAFM) is an extremely powerful tool for exploring surface topology and nanoscale manipulation and characterization. A feature of dAFM is the existence of highly nonlinear forces between a cantilever tip and sample. One of these forces that plays a large role in operation of AFM is the van der Waals (vdW) force....

Integrity check of grounding grids at high voltage substations

The safety in the high voltage substations rely on the integrity of its grounding grid. A single discontinuity at any part of the grounding grid may cause a swell in touch or step potential that may expose the personnel to a hazard of critical electric shock. It may also lead to malfunction of the protection devices leading to erroneous tripping...

Response of an oscillator with a Duffing parameter of the fifth power

Quintic Duffing oscillator is considered. Amplitude-phase relations are derived using averaging theorem and perturbation methods. First The forced quintic system is studied. Stability regions are com-pared to the general case with quintic-qubic non-linearity. Numerical results show that Perturbationmethod and averaging are in agreement with each...

Continuous-time System Identification: A Bilinear Optimization Approach

In the noiseless case, the identification of a grey-box model can be posed as a feasibility problem, i.e. determining if existent - and if so - finding a parameter vector such that the parametric model equals the actual model (or its associated input-output data). Being that in this thesis we are interested in continuous-time grey-box...

Innovative power system event-detection and synchronous plant emulation technique for large wind power plant

The subject matter of this thesis report investigates a synthetic inertia and dynamic stability technique for grid inter-connection of large VSC-HVDC connected offshore windfarms. Assuming traditional load frequency control on the AC grid for the short-term reallocation of power generation resources due to load disturbances, this technique ties...

Wave slamming forces on truss structures for wind turbines

Generally the foundations of offshore wind turbines are steel truss structures which are exposed to wave slamming forces due to breaking waves, typically plunging breaking waves in shallow water. Calculations show that the forces from the plunging breaking waves are governing the design responses of the structure and the foundations. However,...