Wind turbine modelling using doubly-fed induction generators is a well-known subject. However, studies have tended to focus on optimising the components of the system rather than considering the interaction between the components. This research examines the interaction of the control methods for a doubly-fed induction generator (DFIG) in a wind turbine application integrating them with the crowbar protection control and DC-link brake control to make the best use of the converter. The controls of the rotor-side and the grid-side converters of the DFIG model are both well established and have been shown to work. Typically the crowbar protection is designed in order to protect the rotor-side converter and the power electronic components of the DFIG system from high currents occurring in the rotor due to the faults. The DC-link brake-overvoltage protection is also designed to prevent the overcharging of the DC-link capacitor placed between the rotor-side converter and the grid-side converter. In order to show that these protection schemes work and with thought can co-ordinate with each other, tests consisting of a number of balanced three-, two- and one-phase voltage sags are applied to the network voltage. The main contributions of this thesis are establishing operational tuning and design limits for the controllers and system subassemblies. This is to minimise the electrical subsystem interaction while maintaining adequate performance, and have an improved DC-link control. This work also includes a full electrical system study of the wind turbine and an essential literature review on significant references in the field of the DFIG wind turbine system modelling, control and protection. Specifically this research project makes a number of novel contributions to the literature: enhanced DC voltage control including operating point sensitivity analysis and dynamic stiffness assessment, sensitivity and robustness analyses of the power loop control and control loop segmentation by appropriately tuning the controller loops.

Fossil-fuel vehicles are one of the main causes of CO2 emissions nowadays. As we are moving toward cleaner environment electrification of vehicles are becoming more and more popular. With the environment in mind, the recent improvement in battery technology and electronics has drawn a lot of attention to Brushless DC or BLDC  motors. Due to their high torque output and robust design, BLDC motors are a popular choice as the main propulsion unit in electric vehicles.  Permanent magnet synchronous motor, PMSM, is also a brushless dc motor with minor changes in design. So the word BLDC and PMSM is used interchangeably. In this thesis, two motor control algorithms were investigated. 6-Step control and Field oriented control or FOC. A three-phase inverter allows these motors to be driven by a battery. But when battery voltage goes down the speed of the motor also goes down. This thesis investigates a method to maintain the same speed at lower dc voltage. Also running of other motors than the control system was designed for. The control system performs well in simulation for two of the motor tested with the FOC algorithm. Simulation results show that the control system can track speed and current references with minimum error. Speed controller and current controllers control each parameter independently to control the motor. Low battery simulations provide useful data that shows how the field weakening technique makes it possible to achieve higher speed at low dc voltages. / Fossildrivna fordon är en av de främsta orsakerna till koldioxidutsläpp i dag. I och med att vi går mot en renare miljö blir elektrifieringen av fordon allt mer populär. Med miljön i åtanke har den senaste tidens förbättring av batteriteknik och elektronik dragit mycket uppmärksamhet till Brushless DC- eller BLDC-motorer som ska användas som huvudframdrivningsenhet. På grund av dess höga vridmomentutgång och robusta design så är BLDC-motorer mer populära. En permanent magnetisk synkronmotor, PMSM, är också en borstlös dc-motor med mindre förändringar i designen. Så orden BLDC och PMSM används omväxlande. I denna avhandling undersöktes två motoriska styralgoritmer. 6-stegskontroll och fältorienterad kontroll eller FOC. En trefas växelriktare gör att dessa motorer kan drivas av ett batteri. Men när batterispänningen går ner går motorns hastighet också ner. Denna avhandling undersöker en metod för att bibehålla samma hastighet vid lägre likspänning, men även drift av andra motorer än vad styrsystemet var konstruerat för. Styrsystemet fungerar bra i simulering för två av de motorer som testas med FOC-algoritmen. Simuleringsresultat visar att styrsystemet kan spåra hastighet och aktuella referenser med minimalt fel. Hastighetsregulator och aktuella styrenheter kontrollerar varje parameter individuellt för att styra motorn. Simuleringar med lågt batteri ger användbara data som visar hur fältförsvagningstekniken gör det möjligt att uppnå högre hastighet vid låg likströmsspänning.

This diploma thesis demonstrates the differences between approaches in software development. A code generation search is performed. The work describes possible tools and methods of code validation and verification. The next part provides information on the use of a design-based model in critical-demanding applications. Further, the work describes the proposal of platforms for controling the BLDC motor. Low leve software is programed for these chosen platforms. The logic of controling and user interface is created. The logic of controling is created and tested in Simulink. Further more whole programmed code is connected with the low level layer. The whole solution of my diploma thesis is tested.

Parametric acoustic arrays are ultrasonic-based loudspeakers that produce highly directive audio. The audio must first be preprocessed and modulated into an ultrasonic carrier before being emitted into the air, where it will self-demodulate in the far field. The resulting audio wave is proportional to the double time-derivative of the square of the modulation envelope. This thesis presents a fully analog processor which encodes the audio into two Pulse Width Modulated (PWM) signals in quadrature phase and sums them together to produce a Single Sideband (SSB) spectrum around the fundamental frequency of the PWM signals. The two signals are modulated between 8% and 24% duty cycle to maintain a quasi-linear relationship between the duty cycle and the output signal level. This also allows the signals to sum without overlapping each other, maintaining a two-level output. The system drives a network of narrowband transducers with a center frequency equal to the PWM fundamental. Because the transducers are voltage driven, they have a bandpass frequency response which behaves as a first-order integrator on the SSB signal, eliminating the need for two integrators in the processor. Results show that the “SSB-PWM” output wave has a consistent 20-30dB difference in magnitude between the upper sideband and lower sideband. In simulation, a single tone test shows higher total harmonic distortion for lower frequencies and higher modulation depth. A two-tone test creates a 2nd order intermodulation term that increases with the frequencies of the input signals.

This work is focused on the design and construction of component parts of resistance saw. Mechanical parts consist of a movable bracket and a taut cutting wire of Constantan. Electrical parts are designed to supply and control temperature of the cutting wire. The current intensity in the cutting wire is compared with the required current intensity. The difference of these two measurements is fed into a PI - controller. The next part is a PWM generator which generates the square wave signal. The pulse ratio of this signal is proportional to the required temperature of the cutting wire. This signal switches a switching converter that consists of a power transistor P-MOSFET IRF5210 and a diode MBR20100CT. Choking coil with a ferrite E core and with the cutting wire is connected to the output of the converter.

Master’s thesis deals with design and realization of power supply, which is supplied and controlled via USB bus. In theoretical part there are described principles of USB communication drivers which ensures this communication, there are described principles of linear voltage regulators and basic types of DC/DC converters. Mentioned is also PID regulator theory. Practical part aims for design of suitable DC/DC converter topology and creating algorithms for driving this converter. Next there is created PC program which drives power supply and there are also accomplished basic power supply measurements. The result of this thesis is functional power supply supplemented with PCB.

Aim of this project is development of the analyser for cable distributed television signals. At the beginning is a block diagram of the suggested analyser with digitally controled wideband tuner, logarithmic detector, microcontroller and a graphical display module. For each block there is a theoretical analysis, features description and description of the electronic components that were used. In the next part of this project is introduced the design of circuit schematic and printed circuit board of prototyping kit, that was used for experiments and testing of its features and parametres. Last part of this thesis focuses on finishing of a prototyping kit, development of firmware and experimental verification of the prototype's parameters.

This diploma thesis deals with digital audio amplifier with universal inputs and its design. The first part describes modulation and audio formats for audio electronics. The thesis contain design of a block diagram of the digital audio amplifier and describes the requirements for functional blocks. As a basic device for audio signal processing was choosen integrated circuit STA326. The thesis continue with circuits design for each blocks with a description of their principles. The next section describes the construction and firmware for microcontroller. The last part of this diploma thesis is targeted on the presentation of the measured parameters of the amplifier. The conclusion summarizes the results that have been achieved and advantages and disadvantages of the digital audio amplifier prototype.

This thesis is about to introduce the development of switched power supply with output voltage of 5,5 kV and power of 4,3 kW. This thesis directly follows the outputs of two previous semester projects. Main task is about to finish the development of remaining printed circuit boards and perform launching of all parts of developed power supply. Next necessary task is about to assemble a functional prototype of the supply using the developed parts, performing a series of measurement supply’s parameters and creating of technical documentation of mechanical part. There are all stages of supply’s development included in this thesis. From the first part, that describes various types of converters, through the design of all the supply’s parts, to final implementation of functional prototype. There are the results of measurement supply’s parameters at the end of this thesis.

This master's thesis deals with a design and realization of a LED driver that is based on integrated circuits NCV78703 and NCV78723 from ON Semiconductor. The aim of the project is to create a demonstration application with these integrated circuits for the use of company. The circuits can be especially used for driving LED automotive lights. The driver is controlled with a microcontroller also providing a communication with a software running on a PC via USB interface. This software enables to simply modify parameters of the driver in order to adjust an intensity of LEDs.