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.

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.

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.@en

Access to electricity is a key actuator in order to tackle poverty in areas of limited resources. While the population without access to electricity has a decreasing tendency, still almost 1 billion people continue to live without this basic amenity. This thesis has been carried out at the company DC Opportunities as part of the rural electrification project. On this field, the main activity focuses on developing cost-effective DC solutions in the form of a solar home system which consists of a total of 4 devices including low-power LED lights, a solar charging station, a high-power rate power bank and a power hub. The report analyses various existing electrification projects identifying the characteristics of their approaches in order to recognize the shortcomings of market available products and to build a design criterion. Given that the main target application is aimed at rural areas, a modular approach has been the base of the design criterion with the purpose of tailoring the SHS to developing countries with limited resources. The project analyses each step within this modular process together with the power electronics involved in every stage. The main objective of the project is to perform direct charging between the charging station and the power bank, which consists in feeding power directly from the bus voltage of the charging station into the battery cells with only one active converter. This feature is implemented as a result of the introduction of the power delivery protocol released together with the USB type C connector . This offers a wide variety of possibilities which includes negotiable voltage levels ranging from 5 to 20V. The first element taking part in the direct charging is the charging station .This thesis addresses the challenge of designing and building a circuit with dynamic adjustment of voltage and current in a cost-effective and reliable manner. By adding a digital to analogue converter and 2 operational amplifiers, it is possible to add this feature to a wide range of standard voltage converters available in the market. The report analyses this circuit in 3 steps: first with circuit theory, secondly by simulation and eventually by including the results obtained in an empirical test implemented in one of the prototypes. The power delivery protocol is also beneficial for a power-bank application, which is the second element of the direct charging. It is one of the purposes of the thesis to evaluate the performance of direct charging. Eventually, the report presents the main conclusions derived from the analysis of the aforementioned elements and also covers future lines which include improvements to be implemented within the components of the solar home systems.

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.

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.

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.

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.