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A Novel Reference Signal Generation Method for Power-Quality Improvement of Unified Power-Quality Conditioner

This paper proposes a novel reference signal generation method for the unified power quality conditioner (UPQC) adopted to compensate current and voltage-quality problems of sensitive loads. The UPQC consists of a shunt and series converter having a common dc link. The shunt converter eliminates current harmonics originating from the nonlinear load side and the series converter mitigates voltage sag/swell originating from the supply side. The developed controllers for shunt and series converters are based on an enhanced phase-locked loop and nonlinear adaptive filter. The dc link control strategy is based on the fuzzy-logic controller. A fast sag/swell detection method is also presented. The efficacy of the proposed system is tested through simulation studies using the Power System Computer Aided Design/Electromagnetic Transients dc analysis program. The proposed UPQC achieves superior capability of mitigating the effects of voltage sag/swell and suppressing the load current harmonics under distorted supply conditions.

A Review on Feature Extraction for Speaker Recognition under Degraded Conditions

ABSTRACT Speech is a signal that includes speakers emotion, characteristic specification, phoneme-information etc. Various methods have been proposed for speaker recognition by extracting specifications of a given utterance. Among them, short-term cepstral features are used excessively in speech, and speaker recognition areas because of their low complexity, and high performance in controlled environments. On the other hand, their performances decrease dramatically under degraded conditions such as channel mismatch, additive noise, emotional variability, etc. In this paper, a literature review on speaker-specific information extraction from speech is presented by considering the latest studies offering solutions to the aforementioned problem. The studies are categorized in three groups considering their robustness against channel mismatch, additive noise, and other degradations such as vocal effort, emotion mismatch, etc. For a more understandable representation, they are also classified into two tables by utilizing their classification methods, and used data-sets.

Dynamic control of unified power flow controller under unbalanced network conditions

Abstract The effective and reliable use of existing transmission lines are critically important because high-voltage transmission networks met enormous power demands are very expensive investments in terms of their costs. Flexible Alternating Current Transmission Systems (FACTS) are quite efficient to control the power flow of the transmission lines and increase the current capacity of system. Unified Power Flow Controller (UPFC) is the more efficient among FACTS equipments which have the potential to increase the power flow and stability of the transmission line. This paper develops new control approaches for both series and shunt inverters of UPFC. The proposed controller algorithms of shunt and series inverters are based on fuzzy logic controller and rotating orthogonal-coordinate method, respectively. Dynamic control of power flow using proposed UPFC is analyzed as mathematically. Power System Computer-Aided Design (PSCAD) is used to simulate the system and test UPFC in the simulation environment. The test results are presented to show the increased stability of the system and improved dynamic response of UPFC during faults occurred in the transmission line.

Simulation Study of Fuzzy Based Unified Power Flow Controller on Power Flow Controlling

Unified power flow controller (UPFC) is the most widely used FACTS device to control the power flow and to optimize the system stability in the transmission line. The controller used in the control mechanism has an important effect on the performance of UPFC. According to this, the performance of UPFC for several case studies was observed by using different control mechanisms based on Proportional-Integral (PI) and fuzzy controllers in this study. Fuzzy Logic Controller (FLC) was developed by using Takagi-Sugeno inference system and used in UPFC. The case studies are applied to prove the capability of UPFC on power flow and the effectiveness of controllers on the performance of UPFC at the different operating conditions. PSCAD/EMTDC program is used to model UPFC and to verify the performance of UPFC with different controllers in the transmission line.

Implementation of Fuzzy Logic Controller Using FORTRAN Language in PSCAD/EMTDC

Fuzzy logic controllers have gained widespread use by engineers and practitioners due to their design simplicity, closeness to human reasoning and suitability for control applications. Fuzzy logic controlled studies are usually performed in MATLAB, or sometimes in PSCAD/EMTDC (Power Systems Computer Aided Design/Electromagnetic Transient including d.c.) with MATLAB interfacing. The PSCAD/EMTDC software does not include a component for a fuzzy logic controller. This paper is, to the best of our knowledge, the first work that designs and implements a fuzzy logic controller in PSCAD/EMTDC by using FORTRAN codes. In this way, several drawbacks which arise from the interfacing between MATLAB and PSCAD/EMTDC are eliminated. The simulation section of this paper consists of a case study based on a fuzzy logic-controlled PWM inverter in which the performance of the developed fuzzy logic controller is evaluated.

A robust SVM technique to minimize the effects of unbalanced voltage disturbances

Space vector modulation (SVM) is one of the most popular PWM techniques in the control methods of multilevel inverters. The assignment of the reference vector location is very important to obtain the exact switching times and to determine the correct space vectors in this techniques. The location of the reference vector is determined by utilizing the phase angle of the system. It can be obtained from Clarke Transformation for SVM technique or phase-locked loop (PLL) for other methods. The unbalanced disturbances occurred in the three-phase systems affect the switching times obtained by utilizing the phase angle. The output waveform of the multilevel inverters is affected as well. In this study, the effect of disturbances such as line to line faults, unbalanced voltage sags/swells are investigated on conventional SVM technique. In order to minimize these affects, a new technique based on Clarke Transformation is proposed and applied to the two-level inverter. PSCAD/EMTDC simulation program is used to apply the case studies and to take the simulation results.

Computer simulation and experimental implementation of a PIC-controlled hybrid multilevel inverter for undergraduate laboratories

Hybrid multilevel inverters have emerged as attractive power conversion systems at medium voltage levels, which are structured by cascaded series inverters having different internal DC bus voltages. This scheme therefore provides the capability to produce higher voltages at higher speeds with low switching losses and high conversion efficiency. The fundamentals and importance of hybrid multilevel systems can be easily enhanced by the undergraduate with visual learning and laboratory studies. However, the students cannot be able to implement the peripheral interface controller (PIC)‐based projects sufficiently. In this paper, the simulation models and experimental setup of a hybrid multilevel inverter are presented in detail. From the theoretical and experimental experience obtained from this study, the students and engineers can provide more analytical opportunities for studying control algorithms of PIC controlled power electronics projects. This will provide the students to reinforce their lectures and laboratory studies.

A novel switching signals generation method for hybrid multilevel inverters

Use of multilevel inverters is becoming more popular in the recent years. Various topologies and modulation methods have been reported for utility and drive applications in the recent literature. Hybrid multilevel structures are the new multilevel inverter topologies where the cascaded series inverters have different internal DC bus voltages and/or modulated quite differently. This paper introduces a novel switching signals generation (modulation) method for hybrid multilevel inverters. This method is new and based on reference signal tracking. The structure of modeled hybrid multilevel inverter and operating principles of the proposed method are presented. The proposed method is verified by computer simulations using PSCAD/EMTDC. The waveform and THD values are presented and analyzed, which prove the validity of the proposed method.