Recent Advances in Electrical & Electronic Engineering - Volume 12, Issue 5, 2019

Background: A new wireless multiple access technology enabled by using Time Modulated Arrays (TMAs) is proposed in this paper. Methods: It benefits due to the requirement of only a single Radio Frequency (RF) chain, compared with other multiple-RF-chain schemes. Results: As a result, it is able to greatly reduce the system cost, energy consumption, and complexity. Conclusion: In addition, the signal through the single RF chain is narrow-band modulated, reducing the signal Peak-to-Average-Power-Ratio (PAPR), thus, further enhancing the power efficiency of the RF chain, especially for power amplifiers. The operation principle and synthesis approach are elaborated in this paper, and are demonstrated with two examples.

Background: This article proposes the design and implementation of a MMIC (monolithic microwave integrated circuits) Power amplifier using the ED02AH process. Methods: The MMIC ED02AH technology have been developed specifically for microwave applications up to millimeter waves, and for high-speed digital circuits. The use of a single branch of a power amplifier can produce high distortion. In the present paper, the Linear amplification with nonlinear components (LINC) method is introduced and applied as a solution to linearize the power amplifier, it can simultaneously provide high efficiency and high linearity. To validate the proposed approach, the design and characterization of a 5.25 GHz LINC Power Amplifier on MMIC technology is presented. Results: Good results have been achieved, and an improvement of about 37.50 dBc and 59 dBc respectively is obtained for the Δlower C/I and Δupper C/I at 5.25 GHz. Conclusion: As a result of this method, we can reduce the Carrier Power to Third-Order Intermodulation Distortion Power Ratio. Excellent linearization is obtained almost 37.6 dBc for Δlower C/I and 58.8 dBc for Δupper C/I.

Background: Transformer is one of the most important pivot equipment in an electric system which undertakes major responsibility. Therefore, it is very important to identify the fault of the transformer accurately and transformer fault diagnosis technology becomes one topic with great research value. Methods: In this paper, after analyzing the shortcomings of traditional methods, we have proposed a transformer fault diagnosis method based on Online Sequential Extreme Learning Machine (OS-ELM) and dissolved gas-in-oil analysis. This method has better precision than some commonly used methods at present. Furthermore, OS-ELM is more efficient than ELM. In addition, we analyze the effect of different parameter selection on the performance of the model by contrast experiments. Result: The experimental result shows that OS-ELM has certain promotion in precision than some traditional methods and can obviously improve the speed of training than ELM. Besides, it is known that the number of neurons in the hidden layer and the size of dataset have a great effect on the model. Conclusion: The transformer fault diagnosis method based on OS-ELM can effectively identify the faults and more efficient than ELM.

Background: A comparative analysis of Automatic Generation Control (AGC) of two-area electric power systems interconnected by AC and AC-DC links under deregulated environment is conducted. Each area has Thermal-Thermal (TT), Thermal-Hydro (TH) and/or Hydro-Hydro (HH) multiple power sources. A maiden attempt is made to study the demeanour of HH power system under restructured mode. Methods: The state space models of the power systems have been developed to simulate all market transactions probable in a deregulated power environment and optimal proportional integral structured controller is applied to improve the dynamic performance. The concept of DISCO participation matrix is harnessed to simulate the transactions. Results: Eigenvalue analysis is carried out to assess the comparative stability analysis of the power systems with/without AC-DC links. Further, the dynamic responses of TT, TH and HH power systems are contrasted in the presence of AC link and AC-DC links. The inclusion of AC-DC links improves the dynamic performance of all the systems remarkably, however, the responses of HH system are sluggish/poor with large undershoots in comparison to TT and TH systems. Also, TH system exhibits degraded dynamic performance compared to TT system. Conclusion: Moreover, optimal controller is found competent to demonstrate the matching of generation with power demand under different market transactions.

Background: A novel, small size, dual-band rectangular patch antenna with two narrow vertical slots for Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) application is presented here. Methods: The proposed antenna, fed by coaxial line, has dimensions of 21.075 mm ×17 mm ×1. 6 mm. With a pair of vertical slots, the antenna is resonating in 3.5 GHz WiMAX and 5.3 GHz WLAN band. The dimensions of the ground plane, substrate, radiating patch and two slots on the patch antenna are optimized using Particle Swarm Optimization (PSO) to obtain the desired operating frequency band. Results: The proposed antenna shows good radiation characteristics at these two operating bands, making it suitable for dual-band operation. Conclusion: The same design with some different physical parameter may be suitable for other kinds of wireless services. Further, application of Defected Ground Structure (DGS) to such models may also provide better performance.

Background: Detuning is the main problem that affects the efficiency and transmission distance of the resonant coupling Wireless Power Transmission (WPT). The distance of load and the offset of the load position could cause serious detuning. Methods: This paper presents an adjustable coil in which inductance can be adjusted. Then a model of WPT was established that could compensate resonant frequency automatically using the adjustable coil. Next, the relationship between the primary resonant frequency and the transmission efficiency is analyzed from the circuit. The analysis proved that the design of the adjustable coil could improve the transmission efficiency of the WPT system. Finally, a prototype of WPT system was built. Results: The experimental results showed that WPT system with adjustable coil can improve the transmission efficiency which proves the theoretical research. At the same time, it has essential reference value for the future research of WPT. Conclusion: In this paper, aiming at the system detuning caused by some other factors, such as the position shift of the load during the wireless power transmission, an adjustable coil is proposed.

Background: This article describes the circuit construction of the sinusoidal quadrature oscillator using two Voltage Differencing Gain Amplifiers (VDGAs) as active devices. Methods: Since the presented oscillator circuit uses only two external grounded capacitors as passive elements, it is quite suitable for monolithic integration point of view. The condition of oscillation and the frequency of oscillation are non-interactive, and can be controlled electronically by tuning two separate biasing currents. Non-ideal analysis and sensitivity performance are also discussed. Results: The feasibility of the designed oscillator is justified by the PSPICE simulation results based on TSMC 0.35-μm CMOS process parameters. Conclusion: The effects of the VDGA non-idealities on the proposed circuit are also provided, and the computer simulations based on TSMC 0.35-mm CMOS model parameters are included to evaluate the performance of the circuit.

Background: Modeling and controlling of Doubly Fed Induction Generator (DFIG) are presented in this paper. The DFIG is considered in the positive synchronous reference framework under Distorted Grid Voltage Situations (DGVS). The DFIG electromagnetic torque, active and reactive powers of the instantaneous stator are discussed under the condition of harmonically DGVS. Methods: Four alternative control strategies are implemented on DFIG system to enhance the responses under DGVS. A novel rotor current controller based on adaptive neuro-fuzzy interface system (ANFIS) is developed. The main, fifth and seventh order harmonic components of rotor current are straightly adjusted by ANFIS controller without using any sequential component decomposition techniques at six times the grid frequency. The simulation results of implementing the presented control strategies on a two megawatt wind turbine driven DFIG system validate the feasibility and the robustness of the control scheme. Results: The results are compared with the compound controller consisting of a proportional integral (PI) regulator and a harmonic resonant (R) compensator. Conclusion: This comparison indicates the notable removal of torque and DFIG power oscillations either under DGVS.

Background: The energy router based on power electronic technology is the core equipment of energy internet. Energy router can control the voltage of the port and regulate the power injected into the network flexibly. It is of great significance to study how the capability of the energy router can be used to improve characteristics of the power system. Methods: Based on the analysis of energy router, we construct a unified AC-DC power flow model for energy router considering its different control modes. Then, we establish an optimal power flow formulation for the energy router incorporated AC-DC network and propose the multi-objective function to optimize the comprehensive performance of the network. Several cases are observed and analyzed on a modified IEEE-57 system. Results: The result verifies that the optimal power flow formulation can optimize the control values of ports of the energy router and improve the operating state of the power system. The optimal target presented in this paper can improve the characteristics of the grid better than a single optimal target. Conclusion: Energy router will play a vital role in the energy internet based on the power system. The characters of the power system can be improved and the operating costs can be reduced by utilizing the functionality of energy router in regulating power flow.

Background: In a single-ended speech quality evaluation, the measurement of Mean Opinion Score (MOS) is done objectively without the use of clean speech as a reference. In this work, multiple time-instances or multi-instances features using Multi-Resolution Auditory Model (MRAM) along with other relevant features such as Mel-Frequency Cepstral Coefficients (MFCC), and Line Spectral Frequencies (LSF) features are used for single-ended speech quality measurement. The Voice Activity Detection (VAD) algorithm separates the presence of speech-regions from silence in a speech signal. Methods: The multi-instances features are computed using MRAM, MFCC and LSF for different combinations of speech-regions to capture degradations due to multiple time-localized effects or the attacks of short-time transient distortions such as impulsive noise and their distinctions from plosive sounds in speech. These multi-instances features are used for Gaussian Mixture Model (GMM) MAPPING to compute the objective MOS values, corresponding to all multi-instances features. Results: The overall objective MOS estimation of the speech signal is calculated by averaging all the values of objective MOS corresponding to the different multi-instances features of a speech signal. The results in terms of Pearson’s Correlation Coefficients (PCC) and root mean square error (RMSE) between the subjective MOS and the estimated overall objective MOS of speech signals are computed and compared with International Telecommunication Union-telephony (ITU-T) Recommendation P.563 and recently published works on similar types of databases. Conclusion: The improved values of PCC and RMSE between the subjective and the estimated overall objective MOS show the efficacy of the approach.