Electronics, Volume 7, Issue 4 (April 2018) – 14 articles

This paper proposes a technique that compensates for unbalance and nonlinearity in microgrid inverters with power transformers operating in stand-alone mode. When a microgrid inverter is operating in stand-alone mode, providing high-quality power is very important. When an unbalanced, nonlinear load is connected, zero sequence current and negative sequence current occur, which leads to an unbalanced output voltage. This paper examines why the zero sequence component occurs differently depending on the structure of a three-phase transformer connected to the inverter output terminal, and it proposes a method for controlling the zero sequence component. It also uses a resonant controller to remove the harmonics that correspond to the negative sequence component and the nonlinear component. The proposed elements were verified by a Powersim (PSIM) simulation. Full article

This paper consists of the design and implementation of a simple conditioning circuit to optimize the electronic nose performance, where a temperature modulation method was applied to the heating resistor to study the sensor’s response and confirm whether they are able to make the discrimination when exposed to different volatile organic compounds (VOC’s). This study was based on determining the efficiency of the gas sensors with the aim to perform an electronic nose, improving the sensitivity, selectivity and repeatability of the measuring system, selecting the type of modulation (e.g., pulse width modulation) for the analytes detection (i.e., Moscatel wine samples (2% of alcohol) and ethyl alcohol (70%)). The results demonstrated that by using temperature modulation technique to the heating resistors, it is possible to realize the discrimination of VOC’s in fast and easy way through a chemical sensors array. Therefore, a discrimination model based on principal component analysis (PCA) was implemented to each sensor, with data responses obtaining a variance of 94.5% and accuracy of 100%. Full article

This paper proposes a design methodology for an active power filter (APF) system to suppress the second harmonic subgroup injected by an AC electric arc furnace (EAF) to the utility grid. The APF system is composed of identical parallel units connected to the utility grid via a specially-designed coupling transformer. Each APF converter is a three-phase three-wire two-level voltage source converter (VSC). The number of parallel APF units, coupling transformer MVA rating, and turns ratio are optimized in the view of the ratings of commercially-available high voltage (HV) IGBTs. In this research work, line current waveforms sampled at 25.6-kS/s on the medium voltage (MV) side of a 65-MVA EAF transformer are then used to extract the second harmonic subgroup, 95-, 100-, and 105-Hz current components, by multiple synchronous reference frame (MSRF) analysis, which was previously proposed to decompose EAF current interharmonics and harmonics in real-time. By summing up this digital data of the second harmonic subgroup, the reference current signal for the APF system is produced in real-time. A detailed model of the APF system is then run on EMTDC/PSCAD to follow the produced reference current signal according to hysteresis band control philosophy. The simulation results show that the proposed APF system can successfully suppress the second harmonic subgroup of an AC EAF. Full article

Because the traditional transmission line method treats electromagnetic waves as excitation sources and the cavity as a rectangular waveguide whose terminal is shorted, the transmission line method can only calculate shielding effectiveness in the center line of the cavity with apertures on one side. In this paper, the aperture coupling effect of different sides was analyzed based on vector analysis. According to the field intensity distribution of different transport modes in the rectangular waveguide, the calculation model of cavity shielding effectiveness in any position is proposed, which can solve the question of the calculation model of shielding effectiveness in any position in the traditional method of equivalent transmission methods. Further expansion of the equivalent transmission lines model is adopted to study the shielding effectiveness of different aperture cavities, and the coupling effect rule of the incident angle, the number of apertures, and the size of the cavity is obtained, which can provide the technical support for the design of electromagnetic shielding cavities for electronic equipment. Full article

The traditional configurations of power systems are changing due to the greater penetration of renewable energy sources (solar and wind), resulting in reliability issues. At present, the most severe power quality problems in distribution systems are current harmonics, reactive power demands, and the islanding of renewables caused by severe voltage variations (voltage sag and swell). Current harmonics and voltage sag strongly affect the performance of renewable-based power systems. Various conventional methods (passive filters, capacitor bank, and UPS) are not able to mitigate harmonics and voltage sag completely. Based on several studies, custom power devices can mitigate harmonics completely and slightly mitigate voltage sags with reactive power supplies. To ensure the generating units remain grid-connected during voltage sags and to improve system operation during abnormal conditions, efficient and reliable utilization of PV solar farm inverter as STATCOMs is needed. This paper elaborates the dynamic performance of a VSC-based PV-STATCOM for power quality enhancement in a grid integrated system and low voltage ride through (LVRT) capability. LVRT requirements suggest that the injection of real and reactive power supports grid voltage during abnormal grid conditions. The proposed strategy was demonstrated with MATLAB simulations. Full article

Hearing-impaired people do not hear indoor and outdoor environment sounds, which are important for them both at home and outside. By means of a wearable device that we have developed, a hearing-impaired person will be informed of important sounds through vibrations, thereby understanding what kind of sound it is. Our system, which operates in real time, can achieve a success rate of 98% when estimating a door bell ringing sound, 99% success identifying an alarm sound, 99% success identifying a phone ringing, 91% success identifying honking, 93% success identifying brake sounds, 96% success identifying dog sounds, 97% success identifying human voice, and 96% success identifying other sounds using the audio fingerprint method. Audio fingerprint is a brief summary of an audio file, perceptively summarizing a piece of audio content. In this study, our wearable device is tested 100 times a day for 100 days on five deaf persons and 50 persons with normal hearing whose ears were covered by earphones that provided wind sounds. This study aims to improve the quality of life of deaf persons, and provide them a more prosperous life. In the questionnaire performed, deaf people rate the clarity of the system at 90%, usefulness at 97%, and the likelihood of using this device again at 100%. Full article

Measurement-Device-Independent Quantum Key Distribution (MDI-QKD) is a two-photon protocol devised to eliminate eavesdropping attacks that interrogate or control the detector in realized quantum key distribution systems. In MDI-QKD, the measurements are carried out by an untrusted third party, and the measurement results are announced openly. Knowledge or control of the measurement results gives the third party no information about the secret key. Error-free implementation of the MDI-QKD protocol requires the crypto-communicating parties, Alice and Bob, to independently prepare and transmit single photons that are physically indistinguishable, with the possible exception of their polarization states. In this paper, we apply the formalism of quantum optics and Monte Carlo simulations to quantify the impact of small errors in wavelength, bandwidth, polarization and timing between Alice’s photons and Bob’s photons on the MDI-QKD quantum bit error rate (QBER). Using published single-photon source characteristics from two-photon interference experiments as a test case, our simulations predict that the finite tolerances of these sources contribute $(4.04\pm 20/\sqrt{N_{\mathrm{sifted}}})\%$ to the QBER in an MDI-QKD implementation generating an $N_{\mathrm{sifted}}$ -bit sifted key. Full article

This article presents a robust speed tracking algorithm for a permanent magnet synchronous generator utilized for wind power generation systems, considering the machine parameter and load uncertainties. There are two major contributions: (a) a disturbance observer is designed to exponentially estimate disturbances from the model-plant mismatches and severe load torque variations, and (b) it is included in a nonlinear cascade-type proportional speed tracking controller to establish the performance recovery and offset-free properties without the use of tracking error integrators. A simulation result numerically verifies the effectiveness of the proposed technique, where the PowerSIM software emulates a wind power generation system. Full article

The massive penetration of wind generators in existing electrical grids is causing several critical issues, which are pushing system operators to enhance their operation functions in order to mitigate the effects produced by the intermittent and non-programmable generation profiles. In this context, the integration of wind forecasting and reliability models based on experimental data represents a strategic tool for assessing the impact of generators and grid operation state on the available power profiles. Unfortunately, field data acquired by Supervisory Control and Data Acquisition systems can be characterized by outliers and incoherent data, which need to be properly detected and filtered in order to avoid large modeling errors. To deal with this challenging issue, in this paper a novel methodology fusing Fuzzy clustering techniques, and probabilistic-based anomaly detection algorithms are proposed for wind data filtering and data-driven generator modeling Full article

In high-resolution spaceborne synthetic aperture radar (SAR), imaging of moving ship targets is strongly influenced by ships’ complex three-axis motions, so that imaging results are fuzzy and unfocused. Yet scattered and moving information on ship targets is wholly contained in the complex image data. This paper proposes a novel SAR and inverse SAR (SAR–ISAR) hybrid imaging method to improve imaging effects, using this complex SAR image data on ship targets, and based on frequency-domain-extraction-based adaptive joint time frequency (FDE–AJTF) decomposition. First, complex SAR image data is transformed to the Doppler domain in the azimuth dimension, and the optimum azimuth data are selected. Next, the signal in each range cell is decomposed to its polynomial phase signal (PPS) components by FDE–AJTF. Finally, a two-dimensional image of the ship target at a given azimuth time is constructed directly. The feasibility and effectiveness of this proposed imaging method is verified through comparisons with conventional methods in simulation and experimental tests. Full article

Domain-specific accelerators are a reaction adapting to device scaling and the dark silicon era. This paper describes a radar signal processing oriented configurable accelerator and the application space exploration of the system. The system is built around accelerator engines and general-purpose processors (GPPs) that make it suitable for intensive computing kernel acceleration and complex control tasks. It is geared toward high-performance radar digital signal processing; we characterize the applications and find that each of them contains a series of serializable kernels. Taking advantage of this discovery, we design an algorithm pool that shares the same computation resource and memory resource, and each algorithm is size reconfigurable. On the other hand, shared on-chip addressable scratchpad memory eliminates unnecessary explicit data copy between accelerators. Performance of the system is evaluated from measurements performed both on an FPGA SoC test chip and on a prototype chip fabricated by CMOS 40 nm technology. The experimental results show that for different algorithms, the proposed system achieves 1.9× to 10.1× performance gain compared with a state-of-the-art TI DSP chip. In order to characterize the application of the system, a complex real-life task is adopted, and the results show that it can obtain high throughput and desirable precision. Full article

Low power electronic systems, whenever feasible, use supercapacitors to store energy instead of batteries due to their fast charging capability, low maintenance and low environmental footprint. To decide if supercapacitors are feasible requires characterising their behaviour and performance for the load profiles and conditions of the target. Traditional supercapacitor models are electromechanical, require complex equations and knowledge of the physics and chemical processes involved. Models based on equivalent circuits and mathematical equations are less complex and could provide enough accuracy. The present work uses the latter techniques to characterize supercapacitors. The data required to parametrize the mathematical model is obtained through tests that provide the capacitors charge and discharge profiles under different conditions. The parameters identified are life cycle, voltage, time, temperature, moisture, Equivalent Series Resistance (ESR) and leakage resistance. The accuracy of this electro-mathematical model is improved with a remodelling based on artificial neuronal networks. The experimental data and the results obtained with both models are compared to verify and weigh their accuracy. Results show that the models presented determine the behaviour of supercapacitors with similar accuracy and less complexity than electromechanical ones, thus, helping scaling low power systems for given conditions. Full article

The purpose of the presented flyback converter is to equalise the voltage between the cells in a series string within a battery pack providing an active cell-balancing system. This would be an important part of a battery management system (BMS) for charging li-ion batteries in electric vehicles. The converter is based on primary side current sensing, where the conventional feedback circuit is omitted. The purpose of this converter is to improve efficiency by decreasing losses and to increase battery power density by decreasing the number of elements which constitute the power electronics; these are important factors for the future development of electric vehicle battery packs. Analysis of the circuit and the design procedure of the DC-DC flyback converter with primary current sensing is presented in this paper. Finally, several experimental converters have been built and tested to validate the authors’ approach. Full article

Wireless networks, such as mobile ad hoc networks (MANETs) or wireless sensor networks (WSNs), usually suffer link failures and topology changes, due to the mobility of wireless nodes, the insufficient power of wireless nodes, the unstable state of wireless links, and unpredictable environmental interference. If any link or node failure occurs, a lack of fault-tolerant mechanisms may lead to the interruption of active communication between the source and destination nodes. Multipath routing protocols have been proposed to solve the problem. In this paper, we propose a novel multipath routing approach called node-disjoint multipath routing (NDMR) for discovering and establishing two node-disjoint paths between a source and a destination in a wireless network. The proposed approach uses the request-reply mechanism to find the node-disjoint paths. However, it discards duplicates of request messages instead of re-broadcasting them as occurs in several existing approaches. Additionally, NDMR uses a two-way handshake or three-way handshake process for discovering the node-disjoint paths. If the destination can find two node-disjoint paths in the first route discovery, it uses the two-way handshake process. Otherwise, it applies the three-way handshake process. By decreasing the number of steps in the route discovery process, NDMR reduces the route discovery time achieved by existing techniques. These advantages make NDMR very useful for applications that demand high availability and fault tolerance in MANETs and WSNs. The performance of NDMR has been analyzed, evaluated, and compared with that of several existing approaches. Various simulations were conducted to validate the analyzed results. The analyzed and simulated results show that NDMR significantly reduces the control overhead as well as the time required, by existing approaches, for route discovery. Full article