In this thesis, the main objective is to argue and address the best fitting micro grid electric distribution system for a typical water-pump systems whereby the primary energy sources is renewable. So far, the grid whose main sources were wind, fossil fuel and solar energy has achieved the energy supply for the pump located at 51° 26’ 58” N and 4° 13’ 41” E. Seasonal changes were taken into consideration when carrying out the analyzes in the study from both perspectives; the load side and the energy sources. Energy efficiency is analyzed and compared across multiple types of micro grid distribution systems, and the raw data are processed by HOMER program and the results are deduced as such.
The study consists of various grid configurations. Each grid configuration (AC, DC and hybrid AC/DC) is also analyzed by assuming that all three main energy sources are connected to the micro grid. The system performance is also analyzed with 50% load increase in the AC-DC hybrid network. Besides, each grid configuration was re-analyzed using multiple types wind turbine and PV panels and the results were depicted. In Rilland-Netherlands, which was the selected pilot area, solar energy technologies are not utilized sufficiently because the solar energy potential is low. Therefore, most of the energy is supplied by wind power generation systems. For this region, energy surplus produced could be stored in batteries. However, this is not an option due to the cost and technical constraints. According to the analysis results obtained via the HOMER program, the most appropriate solution is to use a hybrid micro grid whose energy source is renewable and it is Grid-Connected. In this regard, the Grid/PV/wind renewable hybrid in a hybrid AC/DC micro-grid system is the most suitable one for the selected pilot area Rilland-Netherlands. ... Read more

The transportation industry is causing 14% of the worldwide greenhouse gas emission. Therefore, the United Nation concluded with the Paris climate agreement to reduce and limit their emissions to keep the global average temperature increase below 2 degrees Celsius. Based on the agreement the European union introduced new regulations to limit the average fleet emission of car companies. In this push towards lowering emission the companies introduced their first generations of electric cars. To further improve the efficiency of the electric drive train new multilevel topologies were introduced. One of the topologies is called modular multilevel converter (MMC) introduced by R. Marquardt and A. Llesnicar in 2003. This new topology main advantage are its modularity and the option to use low voltage component. However, no company industrialized the MMC for drive train application. The reason therefore are the extensive control architecture, hardware and software wise. This thesis investigated possible ways to reduce the wiring and complexity by introducing a low level communication bus together with distributing the control to remove the centralized architecture. Therefore, the different possible low level communication bus were analysed and compared. The different bus protocols were compared based on speed and time to send the same amount of information to control a MMC. It was concluded that the serial peripheral interface bus (SPI) shows the highest capability for the proposed single phase 5 level converter set-up. Therefore, an experimental system was built to validate the performance. The system itself was designed with the goal to use low cost and low voltage component. The validation of the experimental set-up showed the stable operation of the system with an open loop control. Thereby it proofs the possibility to integrate and control the MMC with a low level communication bus. The results can be used as a baseline to further research on integrating theMMC and make it viable for drive train applications. ... Read more

This thesis deals with the modelling and application of magnetic fields in roads. The backbone technology being inductive power transfer (IPT) for electric vehicles. The magnetics for energy transfer in vehicles, can be adapted for heating steel fibres in roads, referred to as self-healing and modelling this is a second aspect of this thesis. The first sections of this thesis is dedicated to an overview of modelling techniques for coil design of IPT systems using both analytical and semi-analytical tools. A detailed literature review of techniques is followed by a comparison highlighting the strengths and weakness of techniques in terms of ease of use, computational efficiency, application to material interfaces etc. Analytical modelling of single and multi-coil configurations of IPT systems is carried out subsequently. The theory of partial inductance is used to model these geometries, to assess the impact of system parameters such as coupling, power transferred and magnetic efficiency with shapes of couplers and misalignment. Next, the problem of misalignment is highlighted by considering a distributed IPT system. The analytical modelling and experimental analysis of misalignment - lateral and longitudinal is performed. Edge effect is observed and experimentally validated. The second part of this thesis is dedicated to a multi-objective optimization based on the results of the developed analytical model. The goal being the development of a prototype IPT system for powering light EVs. The double rectangular (DR) coupler is chosen as the geometry for power transfer. Several geometry parameters - turns, ferrites (number, dimensions), gap between ferrites etc. are considered as design variables. Efficiency, area related power density and weight are considered as the optimization targets. Pareto fronts are developed and a particle is chosen for the development of a prototype. An experimental set-up is built consisting of a 85 kHz inverter, compensated charge-pads, rectifier and resistive load. The inverter is based on SiC MOSFETS and SiC Schottky anti-parallel diodes, the rectifier made from the same diodes. Phase shift control of the inverter legs is used to control power flow. An experimental analysis to validate the magnetic models is also developed. The third part of this thesis deals with system level economic analysis of IPT technology. A case study of bus fleet is considered and a generic methodology is developed to determine driving range as a function of mass and frontal area of the EV. The economic analysis is performed also identifying the trade-offs between road coverage of IPT, efficiency and battery size. Finally, the thesis culminates with a vision toward a future highway. Such a highway is expected to undergo a functional upgrade to handle electrification of transportation. This evolves around the integration of IPT systems, with low maintenance inductive healing asphalt roadways and renewable energy generation. The modelling challenges to such an integration is studied both using simulations and experiments. A case study for sizing renewable energy in a highway (A12) in the Netherlands using IPT is detailed. ... Read more

Inductive power transfer (IPT) has become a hot topic and is supposed to have a wide range of application in the future. This thesis focuses on the IPT system with multiple pickups in the lighting application. A multiple pickup system can power more than one pickup at the same time and the power consumption varies with a different number of pickups connecting in the circuit. A problem with the multiple pickup system is that at light load the power supply consumes a large amount of reactive power for a small active power demand. The aim of the design is to build a power supply with a constant current output. The designed circuit is supposed to reduce the reactive power demand and keep zero voltage switching (ZVS) in all range of load.

This thesis selects the half bridge inverter and LCL-T network as the topology. The characteristic of the LCL-T network is first analyzed under first harmonic approximation. The trade off between the constant current output, reactive power demand, and ZVS is interpreted. The system is proposed to work at a higher frequency for a light load. In addition, the effects of higher order harmonics on the switching current and apparent power are also given in the form of calculations. Subsequently, the parameters in the topology of the half bridge inverter and LCL-T network are determined. The control circuit is built to realize automatic frequency switching according to the load condition. The next step is to simulate the designed circuit in LTspice and construct it in the lab. The result of simulation and experiment verifies that the reactive power demand is reduced with a higher frequency at light load. Constant current output and ZVS are ensured at the same time in all range of load. But the efficiency of the system does not show a clear improvement since the loss is dominated by the cable loss, which is determined by the requirement of cable current and the pickup design. ... Read more

A driver with high power factor, high efficiency and safety isolation are more attractive in the lighting application. Flyback is an ideal choice to be the power factor stage in LED driver. But one of the most difficulty in flyback topology is the energy stored in its leakage inductance. This part of the energy will introduce very high voltage spike on the main switch. A clamp circuit is needed.Passive clamp flyback converter is with few components and effectively clamping the voltage stress on transistor. But its switching frequency is limited by its switching loss. So the transformer volume in passive clamp flyback is very bulky. The aim of this project is to investigate high switching frequency Active Clamp Flyback converter with GaN transistor as power factor correction in lighting application.With the active clamp loop, the leakage inductance energy and snubber loss could be utilized properly to allow ZVS on switches under all line and load conditions and recycled to input source.So high switching frequency and high efficiency are both achievable.
In this project,specific control method, dead time length and conduction mode are properly designed for active clamp flyback converter as PFC in lighting application.The implementation of closed control loop is not included.A 50W (75V) prototype of active clamp flyback front end converter operation around 1MHz with GaN transistor as Power Factor Correction stage in lighting application is developed to verify the analysis. ... Read more

In a cordless kitchen system, the appliances do not make use of a power cord. The system consists of a power channel and a communication channel. There are various resonant topologies which can be implemented in the power channel[9]. The chosen topology should meet the functional as well as non-functional equirements of the system. Presently, a series resonant topology is used in the system. The topology is easy to understand, to implement and could meet the functional requirements like the amount of power and high efficiency of the system easily. But, it is difficult to meet the non-functional requirements like overvoltage protection, EMI and simple control of the system. This master’s thesis is mainly focused on design and realization an inductive power transmitter which addresses the following research questions:
• EMI: The present inductive power transmitter is based on a series resonant inverter which has a disadvantage of high dV/dt’s across the inverter bridge and the transmitter coil. Furthermore, ZVS of the power switches can be lost at low duty cycles or low loads. Both mechanisms causes high dV/dt’s in the system, which results in increase in common mode noise problems.
• Overvoltage: The present series resonant topology with the calculated circuit components and given load conditions (coupling factor (k) and load resistance (RL)), is observed to be operating in the capacitive mode of operation, when the load is disconnected/removed. Therefore, disconnection of the load causes overvoltage on the transmitter as well as the receiver coil. The overvoltage, in the absence of ’expensive’ protective means, can damage the system components and the system may fail to operate.
• Simple control: The present system is a 4th order system. Due to weak coupling between the transmitter and the receiver coils, there exists multiple operating points where the voltage gain is the same. Therefore, it is difficult to find an optimal operating point for the control loop. Also, as mentioned in previous point, the load disconnection results in capacitive mode of operation of the system. To protect the system the control loop should take care that the system operates in the desired inductive mode of operation, as fast as possible and without causing significant losses.
The report proceeds with an introduction about the cordless kitchen project. It is followed by the description and the analysis of the present system. Next, the detailed analysis of other possible topologies and selection of the alternative topology is described. It is followed by the description about the new proposed model. The report concludes with the conclusion and a paper publication. The paper is published during the Wireless Power Congress arranged by WEKA FACHMEDIEN GmbH in July-2017. ... Read more

In recent years, superconducting synchronous generators (SCSGs) have been proposed as an alternative to permanent magnet synchronous generators (PMSGs). They are expected to reduce the top head mass and the nacelle size for such large wind turbines. In 2012, the INNWIND.EU project initiated this research to investigate SCSGs for 10-20MWdirect-drive offshore wind turbines. However, the feasibility of SCSGs was limited by a few critical issues, such as high costs, AC losses in the superconducting winding and excessive short circuit torque. Furthermore, SCSG designs proposed in the literature were various but all less competitive than PMSGs. ... Read more

The transition towards a sustainable society calls for the massive deployment of renewable energy sources such as large wind parks located far offshore. High-voltage direct current transmission based on voltage sourced converter technology (VSC-HVDC) offers a wide range of technological benefits that foster the grid integration of offshore wind parks. Coupling AC and HVDC grids comes with significant challenges. Control and system functions, which were formerly separated, interact, especially during faults in the transmission system. Classical (transient stability) modelling and simulation does not suffice and must be made ready for VSC-HVDC.

This Ph.D. thesis answers two questions to master these challenges. First, what is the impact of the operation and control of a, possibly multi-terminal, offshore grid based on VSC-HVDC on the transient stability of the onshore power system? Second, how can we model and simulate these impacts while maintaining the desired simulation accuracy and speed? The results of this thesis facilitate fast and accurate assessment of stability impacts of large transmission systems with a significant proportion of converter-interfaced generation. ... Read more

Throughout the history of power electronics, main driving force of developments is attribute to innovations in power semiconductor technology. With continuous technical improvements in the past 30 years, Si devices, being the most widely used power semiconductor technology, are approaching physical limits e.g. breakdown field, thermal conductivity, etc. of the basic material. Performances of power converters such as efficiency, power density, etc., therefore, has entered into a stage that further improvements are not likely to happen without revolutionary advance in power semiconductor technology. GaN power semiconductor devices, judging from the wide bandgap nature of its material, have the potential of outperforming conventional Si counterparts in measures of high voltage, high temperature and high frequency operations. Capabilities of a GaN device, however, is influenced by more issues, which, apart from material properties, also include die design and fabrication approaches, device packaging technologies, how they are used in an application, etc. In fact, at this stage, available GaN transistors are mostly of lateral structure and, as a consequence, confined to low voltage ones (<1kW) while maximum junction temperature of these products is limited to 175 °C because of the lack of suitable packaging technologies. So far, high frequency operation performance of GaN power semiconductors is unknown and needs to be investigated. This thesis explores high frequency operation potentials of single-die, normally-off GaN power semiconductors that are suited for high voltage, low current applications. The exploration is carried out by means of conducting loss modeling of GaN transistors, uncovering desirable operation conditions of GaN devices for high frequency operations according to analysed results from the model, identifying optimal topologies and operation modes in power converters that can facilitate such conditions for GaN to achieve optimal utilization of the new technology and demonstrating potentials of GaN power semiconductors in an application with all the developed techniques employed. ... Read more

This thesis suggests that with air-cooled direct-drive ring-type machines it is very likely to incur into a weight penalty for the application of main propulsion of civilian helicopters. This is however an application not investigated before at the level of detail presented. Therefore, this work serves as a design philosophy and guideline for the development of electrical main propulsion drives for rotary-wing aircraft with a MTOW of 3t or lower. It proposes a systematic approach to a solution, and initial considerations for high-power/low-weight machines with low to medium rotational speed. Furthermore, it highlights the importance of the mechanical and structural considerations for both the electromagnetic mass and the support structure. ... Read more