<abstract><title style='display:none'>Abstract</title> This paper presents results of study of loss-of-excitation phenomena simulations. Loss of excitation is a very common fault in synchronous machine operating and can be caused by short circuit of the field winding, unexpected field breaker open or loss-of-excitation relay mal-operation. According to the statistic [1], the generator failure due to loss-of-excitation accounts for 69% of all generator failures. There has been concern over possible incorrect operation of the relay when operating the generator in the under-excited region, during stable transient swings and during major system disturbances. This article can serve as inputs for system operators in preparation of operation area or protection relaying area.</abstract>

Power System Management s.r.o., Ondavská 5, 040 01 Košice,

Vchodoslovenská distribučná, a.s., Mlynská 31, 040 01 Košice,

Loss of excitation of synchronous generator

<abstract xml:lang="en"><title style='display:none'>Voice Conversion Using Pitch Shifting Algorithm by Time Stretching with PSOLA and Re-Sampling</title>Voice changing has many applications in the industry and commercial filed. This paper emphasizes voice conversion using a pitch shifting method which depends on detecting the pitch of the signal (fundamental frequency) using Simplified Inverse Filter Tracking (SIFT) and changing it according to the target pitch period using time stretching with Pitch Synchronous Over Lap Add Algorithm (PSOLA), then resampling the signal in order to have the same play rate. The same study was performed to see the effect of voice conversion when some Arabic speech signal is considered. Treatment of certain Arabic voiced vowels and the conversion between male and female speech has shown some expansion or compression in the resulting speech. Comparison in terms of pitch shifting is presented here. Analysis was performed for a single frame and a full segmentation of speech.</abstract>

Voice Conversion Using Pitch Shifting Algorithm by Time Stretching with PSOLA and Re-Sampling

<abstract xml:lang="en"><title style='display:none'>Single Phase PWM Rectifier in Traction Application</title>This research has been motivated by industrial demand for single phase PWM rectifier in traction application. This paper presents an advanced control structure design for a single phase PWM rectifier. The PWM rectifier is controlled to consume nearly sinusoidal current with power factor nearing to unity. The control structure consists of a DC-link voltage controller and a current controller implemented by a proportional-resonant controller using a fast phase angle and frequency estimator. The estimation algorithm is derived from the weighted least-squares estimation method. The feasibility of the proposed control structure is confirmed by experimental tests performed on designed laboratory prototype.</abstract>

Single Phase PWM Rectifier in Traction Application

<abstract><title style='display:none'>Abstract</title>The normal life of a transformer is well above 25 years. The economical operation of the distribution system has its roots in the equipments being used. The economy being such, that it is financially advantageous to replace transformers with more than 15 years of service in the second perennial market. Testing of transformer is required, as its an indication of the extent to which a transformer can comply with the customers specified requirements and the respective standards (IEC 60076-3). In this paper, induced over voltage testing on transformers using enhanced Z source inverter is discussed. Power electronic circuits are now essential for a whole array of industrial electronic products. The bulky motor generator set, which is used to generate the required frequency to conduct the induced over voltage testing of transformers is nowadays replaced by static frequency converter. First conventional Z-source inverter, and second an enhanced Z source inverter is being used to generate the required voltage and frequency to test the transformer for induced over voltage test, and its characteristics is analysed.</abstract>

Induced over voltage test on transformers using enhanced Z-source inverter based circuit

<abstract><title style='display:none'>Abstract</title>We have designed and verified a new structure for ohmic contacts to p-GaN based on a layer of carbon nanotubes (CNT), reduced graphene oxide (r-GO) and metallic layers of Cr, Pd and Au, namely in configurations Au/Cr/r-GO/CNT/p-GaN and Au/Pd/r-GO/CNT/p-GaN. The effects have been studied of the annealing temperature and the gas ambient upon the electrical properties of the contacts. Annealing of the Au/Pd/r-GO/CNT/p-GaN structure in air at 500°C for 1 minute resulted in linear <italic>I - V</italic> curves measured between planar electrodes on the p-GaN. Hence, addition of r-GO to the CNT interlayer between p-GaN and the metallization layer is a highly promising procedure for further improvements of the ohmic contacts to p-GaN.</abstract>

Institute of Electronics and Photonics, Slovak University of Technology, Ilkovičova 3, 812 19 Bratislava, Slovakia

Danubia NanoTech, s.r.o., Ilkovičova 3, 841 04 Bratislava, Slovakia

Ohmic Conacts to p-GaN on the Basis of Carbon Nanomaterials

<abstract xml:lang="en"><title style='display:none'>A New Soft Starting Method for Wound-Rotor Induction Motor</title>Starting of a three-phase Induction motor using a starter rheostat in rotor circuit has some disadvantages. A new method for starting of a three-phase motor by using a parallel combination of resistors, self-inductors and capacitors in rotor circuit is proposed in this paper. The proposed method ensures the soft and higher starting torque as well as limited starting current as compared to shorted rotor method. The characteristic curves for both methods (shorted rotor and rotor with added elements) are provided. The mathematical model based on the steady-state equivalent circuit of the induction motor is expanded in frequency domain and the required computer program is prepared using an optimization method. The values for added elements to rotor circuit are calculated in such a way that minimum starting time considering current and torque limitations are achieved.</abstract>

A New Soft Starting Method for Wound-Rotor Induction Motor

<abstract><title style='display:none'>Abstract</title>
This paper describes realization, basic properties, testing, and experiments with a special prototype of a wearable two-channel photoplethysmography (PPG) sensor supplemented by contact thermometers that maps the skin temperature at the place where the optical part of the sensor touches a measured hand part (typically a wrist and fingers). Preliminary measurement confirms that proposed I2C thermometers have proper stability and precision, so can be successfully used in the developed PPG sensor. The performed main experiments show that the significant increase of temperature was always observed at the place of the worn PPG sensors during the whole measurement. This rise of temperature affects mainly the PPG signal range, thus it has also influence on the quality of the sensed PPG wave. The conclusion formulates the final recommendation about the necessity of at least 5-minute time delay between the PPG sensor placement on the hand and the start of the PPG signal acquisition. While the current measurements were realized in normal laboratory conditions, the whole wearable PPG sensor consists of non-ferromagnetic materials and all parts are fully shielded by aluminum boxes to enable measurement in a low magnetic field environment which, is our final long term research aim.
</abstract>

Contact measurement of skin temperature using a wearable two-channel PPG optical sensor supplemented by thermometers

<abstract><title style='display:none'>Abstract</title>
Test case prioritization (TCP) is a regression technique that sequences test cases by assigning priority based on specific criteria defined by software testers. Various parameters, such as code coverage, statement coverage, and method coverage, are utilized in Test Case Prioritization (TCP), wherein metaheuristic techniques are widely employed to determine the optimal order of test cases based on these specified parameters. However, simply applying these techniques does not ensure the satisfaction of all the needs of software testers. This paper introduces an empirical study that employs the multi-objective test case prioritization (MOTCP) technique to prioritize the test cases based on target points defined by software testers. The study calculates a Software Complexity Index (SCI) at the code level, identifying fault-prone areas. Furthermore, a Test-case Complexity Index (TCI) is also used for prioritization. The proposed technique incorporates various target points defined by the software tester to calculate SCI and TCI, which serve as our main objectives for TCP. A detailed analysis is also performed to examine the impact of these target points on the generated optimal order of test cases. Finally, the proposed model is compared with other state-of-the-art techniques across various evaluation parameters.
</abstract>

Fault sensitivity index-based multi-objective testcase prioritization

<abstract><title style='display:none'>Abstract</title>
The emergence of Internet of Things enabled with mobile computing has the applications in the field of unmanned aerial vehicle (UAV) development. The development of mobile edge computational offloading in UAV is dependent on low latency applications such as disaster management, Forest fire control and remote operations. The task completion efficiency is improved by means of using edge intelligence algorithm and the optimal offloading policy is constructed on the application of deep reinforcement learning (DRL) in order to fulfill the target demand and to ease the transmission delay. The joint optimization curtails the weighted sum of average energy consumption and execution delay. This edge intelligence algorithm combined with DRL network exploits computing operation to increase the probability that at least one of the tracking and data transmission is usable. The proposed joint optimization significantly performs well in terms of execution delay, offloading cost and effective convergence over the prevailing methodologies proposed for UAV development. The proposed DRL enables the UAV to real-time decisions based on the disaster scenario and computing resources availability.
</abstract>

Deep reinforcement learning based computing offloading in unmanned aerial vehicles for disaster management

<abstract><title style='display:none'>Abstract</title>
The paper evaluates how the control of transmitted power affects the intensity of radiation in a mobile network cell. Cell models without power control, with standard power control and a model with power control and channel reallocation are considered. The relative reduction of radiation is evaluated and several examples of calculations are presented. Remarks are given on the dependence of radiation reduction on the number of traffic channels, traffic intensity and signal attenuation coefficient. The assessment procedure and results are based on previously verified traffic process simulation models.
</abstract>

Influence of power control in the mobile network on the radiation level

<abstract><title style='display:none'>Abstract</title>
In order to further improve the defect detection capability of gas insulated switchgear and avoid equipment faults, broadband current array sensing system is designed to simultaneously monitor the system status such as partial discharge, relative dielectric loss, and power frequency overvoltage. The dynamic model of the system is analysed, and based on which, the system state equation is obtained meanwhile fault observer is designed, and the system stability criterion under <italic>H</italic>∞ condition is calculated. The reliability of the system under different packet loss rates is verified based on cloud models, and the principle of using appropriate electromagnetic compatibility to prevent packet loss rates below 50% is proposed.
</abstract>

Stability and reliability analysis for broadband current array sensing system applied to GIS

<abstract><title style='display:none'>Abstract</title>
In this paper, a broadband(12-18G) low-noise amplifier (LNA) using 65-nm CMOS technology for satellite communication is presented. This LNA was designed in a cascode common source with inductive degeneration topology. In addition, the bulk isolation technique is employed to make the proposed LNA have a higher gain. Furthermore, a two-stage cascaded configuration combined with inductive parallel peaking technology is utilized to make the LNA achieve a wide operating band. For validation, we design this LNA in a 65nm CMOS technology. The simulated results show that S21 of 17.7dB <italic>± </italic>0.5dB, the input/output return loss of -10dB to -33dB and -12dB to -23dB, respectively. It offers the minimum noise figure (NF) performance of 3.33dB, reverse isolation(S12) better than 60dB, and third-order input point (IIP3) of -22.8 dBm obtained over the band of interest. Excluding the output buffer stage, the LNA is consuming 5.1 mW at a supply voltage of 0.8V and its layout area occupies 0.205 mm2.
</abstract>

A Ku band low-voltage and low-power CMOS low-noise amplifier with bulk isolation techniques

<abstract xml:lang="en"><title style='display:none'>Small-Signal Analysis of Autonomous Hybrid Distributed Generation Systems in Presence of Ultracapacitor and Tie-Line Operation</title>This paper presents small-signal analysis of isolated as well as interconnected autonomous hybrid distributed generation system for sudden variation in load demand, wind speed and solar radiation. The hybrid systems comprise of different renewable energy resources such as wind, photovoltaic (PV) fuel cell (FC) and diesel engine generator (DEG) along with the energy storage devices such as flywheel energy storage system (FESS) and battery energy storage system (BESS). Further ultracapacitors (UC) as an alternative energy storage element and interconnection of hybrid systems through tie-line is incorporated into the system for improved performance. A comparative assessment of deviation of frequency profile for different hybrid systems in the presence of different storage system combinations is carried out graphically as well as in terms of the performance index (PI), <italic>ie</italic> integral square error (ISE). Both qualitative and quantitative analysis reflects the improvements of the deviation in frequency profiles in the presence of the ultracapacitors (UC) as compared to other energy storage elements.</abstract>

Research Scholar, Department of Electrical Engineering, Motilal Nehru National Institute of Technology, Allahabad, India

Department of Electrical Engineering, Motilal Nehru National Institute of Technology, Allahabad, India

Small-Signal Analysis of Autonomous Hybrid Distributed Generation Systems in Presence of Ultracapacitor and Tie-Line Operation

<abstract><title style='display:none'>Abstract</title> This paper investigates the hybrid chaos synchronization of identical Wang four-scroll systems (Wang, 2009), identical Liu-Chen four-scroll systems (Liu and Chen, 2004) and non-identical Wang and Liu-Chen four-scroll systems. Active control method is the method adopted to achieve the hybrid chaos synchronization of the four-scroll chaotic systems addressed in this paper and our synchronization results are established using Lyapunov stability theory. Since the Lyapunov exponents are not required for these calculations, the active control method is effective and convenient to hybrid synchronize identical and different Wang and Liu-Chen four-scroll chaotic systems. Numerical simulations are also shown to illustrate and validate the hybrid synchronization results derived in this paper.</abstract>

Department of ECE, Velammal Institute of Technology, Panchetti, Tiruvalluvar District, India

Research and Development Centre, Vel Tech Dr. RR & Dr. SR Technical University, Avadi, Chennai-600 062, India

Hybrid Chaos Synchronization of Four–Scroll Systems via Active Control

<abstract xml:lang="en"><title style='display:none'>Optimal Relays Coordination Efficient Method in Interconnected Power Systems</title>In this paper an efficient method for optimal overcurrent relay coordination is proposed. In the proposed method using genetic algorithm, an objective function (OF) is developed to solve the problem of miscoordination for six pairs short circuit fault currents. The new OF is improved to be simple, optimal and efficient. This technique takes into account the changes in network configuration. The efficiency of the proposed technique is demonstrated by comparing the results of two different networks namely typical 8-bus &amp; IEEE 30-bus systems with those obtained using the recently developed techniques.</abstract>

Center of Excelence on Power System, Amirkabir University of Technology, Iran

Optimal Relays Coordination Efficient Method in Interconnected Power Systems

<abstract><title style='display:none'>Abstract</title>This paper presents a tuning approach based on Continuous firefly algorithm (CFA) to obtain the proportional-integral- derivative (PID) controller parameters in Automatic Voltage Regulator system (AVR). In the tuning processes the CFA is iterated to reach the optimal or the near optimal of PID controller parameters when the main goal is to improve the AVR step response characteristics. Conducted simulations show the effectiveness and the efficiency of the proposed approach. Furthermore the proposed approach can improve the dynamic of the AVR system. Compared with particle swarm optimization (PSO), the new CFA tuning method has better control system performance in terms of time domain specifications and set-point tracking.</abstract>

CONTINUOUS FIREFLY ALGORITHM FOR OPTIMAL TUNING OF PID CONTROLLER IN AVR SYSTEM

<abstract>The purpose of this paper is to present the design and program implementation of a general procedure which yields the mathematical model for a classical or rotary inverted pendulum system with an arbitrary number of pendulum links. Lagrange equations of the second kind with an integrated Rayleigh dissipation function are employed in model design, and the energetic balance relations, derived for the base and all pendulum links in a generalized (n-link) classical and rotary inverted pendulum system, are implemented in form of symbolic MATLAB functions and a MATLAB GUI application. The validity and accuracy of motion equations generated by the application are demonstrated by evaluating the open-loop responses of simulation models of classical double and rotary single inverted pendulum.</abstract>

Modelling of Classical and Rotary Inverted Pendulum Systems – A Generalized Approach

<abstract>This paper deals with certain options on controlling an inverted rotary pendulum also known as the Furuta pendulum. Controlling an inverted pendulum involves two stages. The first stage is the swing up of the pendulum and the second stage is its balancing in the up-right position. The paper describes two possibilities on swinging up the pendulum. First one is the classical approach based on comparing the current total (potential and kinetic) energy of the system with the energy in its stabilized up-right position. The second option uses an exponentiation operation over the pendulum position since the trend of power law function is very convenient for determining the amount of required energy to be delivered to the system. For the purposes of balancing the pendulum in the up-right position a predictive controller based on optimal control law with perturbation was proposed, which is an LQ controller with control signal corrections when constraints are exceeded. The results are illustrated by real-time experiments on a laboratory rotary inverted pendulum setup.</abstract>

Swinging up the Furuta Pendulum and its Stabilization Via Model Predictive Control

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The Journal of Slovak University of Technology

 The Journal of Electrical Engineering, published bimonthly, is devoted to:   Automation and Control  Computer Engineering  Electronics,...

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