Volume 65 (2014): Issue 4 (August 2014)

The work aims at a development of positioning algorithm suitable for low-cost indoor or urban pedestrian navigation application. The sensor fusion was applied to increase the localization accuracy. Due to required low application cost only low grade inertial sensors and wireless network based ranging were taken into account. The wireless network was assumed to be preinstalled due to other required functionality (for example: building control) therefore only received signal strength (RSS) range measurement technique was considered. Wireless channel loss mapping method was proposed to overcome the natural uncertainties and restrictions in the RSS range measurements The available sensor and environment models are summarized first and the most appropriate ones are selected secondly. Their effective and novel application in the navigation task, and favorable fusion (Particle filtering) of all available information are the main objectives of this thesis.

For wireless systems, it is of vital importance to use the scarce radio resources in an efficient way. The main targets are to reduce the power consumption and increase the throughput of wireless devices. Using header compression both throughput can be increased and power can be saved. Using packet overhearing reduction power can be saved. This paper presents the achieved performance improvements when using these two methods. The simulation results are confirmed by analytical calculations. We show that we can achieve up to 35% power save when combining both methods and close to 0.1 additional normalized throughput.

This paper presents a new table based algorithm for overcurrent relay with inverse-time characteristic. The algorithm is based on loading the adequate time vector through which inverse-time characteristic is modeled. It uses samples of the current and calculates rms value. The rms current represents an input value for the index estimation what determines corresponding element from already loaded time vector. Since the calculations used in this algorithm are based on simple mathematical operations, short processing time is achieved. Performances of the algorithm are tested by several computer-generated signals. Furthermore, comparative analyses showed indisputably that suggested procedure possesses significant advantages compared to other solutions: simplicity, high speed of operation and accuracy.

A conductor thermal model related to CIGRE and IEEE solutions was developed and compared with measurements. Two pylons of a single line were equipped with weather monitoring stations and conductor temperature sensors based on Surface Acoustic Wave (SAW) principle. Also a fiber optic distributed temperature sensing system was installed to provide additional data. Over 2.5 million data points were evaluated. Developed model deviation for more than 99 % of values proved to be ±1 °C for SAW sensor and ±3.5 °C for the fiber optic measurement. Several ampacity determination methods were described from a transmission grid operator’s point of view. Their features were compared in order to show at which planning period they could be useful. A new method for dynamic line rating determination was proposed. Although it reduces maximum ampacity gain, its advantage lies in minimizing measurement systems while retaining relatively stable value and low risk of temperature limit exceeding.

This paper presents design and evaluation of a novel approach based on emotional learning to improve the speed control system of rotor flux oriented control of induction motor. The controller includes a neuro-fuzzy system with speed error and its derivative as inputs. A fuzzy critic evaluates the present situation, and provides the emotional signal (stress). The controller modifies its characteristics so that the critics stress is reduced. The comparative simulation results show that the proposed controller is more robust and hence found to be a suitable replacement of the conventional PI controller for the high performance industrial drive applications.

The increasing wind power integration with power grid has forced the situation to improve the reliability of wind generators for stable operation. One important problem with induction generator based wind farm is its low ride through capability to the grid voltage disturbance. Any disturbance such as voltage dip may cause wind farm outages. Since wind power contribution is in predominant percentage, such outages may lead to stability problem. The proposed strategy is to use dynamic voltage controller (DVR) to compensate the voltage disturbance. The DVR provides the wind generator the ability to remain connected in grid and improve the reliability. The voltage dips due to symmetrical and unsymmetrical faults are considered for analysis. The vector control scheme is employed for fault compensation which uses software phase locked loop scheme and park dq0 transformation technique. Extensive simulation results are included to illustrate the control and operation of DVR.

In this paper, general electric field expressions are proposed to consider the effect of channel base ground reflections and ground conductivity on the electric field components due to lightning. The proposed method can support different current models and functions directly in the time domain without the need to apply any extra conversions. The proposed method is applied on a sample of measured channel base current from triggered lightning experiment and the results are discussed accordingly. The results show that the ground reflection and ground conductivity can have an effect on the peak values of the electric fields whereby the electric field components have a great effect on the widely used coupling models.

This paper presents the high gain step-up BOOST converter which is essential to step up the low output voltage from PV panel to the high voltage according to the requirement of the application. In this paper a high gain BOOST converter with coupled inductor technique is proposed with the MPPT control. Without extreme duty ratios and the numerous turns-ratios of a coupled inductor this converter achieves a high step-up voltage-conversion ratio and the leakage energy of the coupled inductor is efficiently recycled to the load. MPPT control used to extract the maximum power from PV panel by controlling the Duty ratio of the converter. The PV panel, BOOST converter and the MPPT are modeled using Sim Power System blocks in MATLAB/SIMULINK environment. The prototype model of the proposed converter has been implemented with the maximum measured efficiency is up to 95.4% and full-load efficiency is 93.1%.

In this paper we present the capacitance study of the intrinsic amorphous silicon/crystalline silicon heterostructure with the aim to gain insight on the heterointerface properties of a passivated silicon heterojunction solar cell. It is shown that due to the high density of defect states in the amorphous layer the structure has to be analyzed as a heterojunction. Using the analysis, the following values have been determined: conduction-band offset of 0.13 eV, electron affinity of 3.92 eV, and density of defect states in the intrinsic amorphous silicon being that of 4.14 X 10²¹m^—3.

Magnetoelastic properties of Fe6iCoigSÍ5Bi5 alloy after thermomagnetic treatment were tested for both compressive and tensile stresses, what is significant novelty. Results of presented investigation opens new ways of modelling the magnetoelastic effects in amorphous systems tailored by thermomagnetic treatment.

Specific saturation magnetization σ_S is an important parameter of ferromagnetic materials. It is in principle independent of the structure and shape of the sample. There are two ways to calibrate devices for determining σ_S: the standard method, using a calibrated magnetic moment standard, or an alternative method, using a special moment coil. This paper presents a calibration method used at Czech Metrology Institute for calibration of Koerzimat 1.096 using a special moment coil. Special attention is given to a description of the special moment coils used for Koerzimat 1.096 calibration, and to analysis of sources of uncertainty. Calibration expanded uncertainty of 0.4 up to 0.6 % can be achieved using this method.