Good Power Quality Research Articles

Hybrid Damping in Higher Order Line Side Filter in Active Front-end Operation

 Abstract—Active front-end converter draws a special attention in drives application and distributed generation application where good power quality and robustness are essential. Damping is an essential part of design in LCL filter based grid-connected system from point of view closed loop stability. This paper presents a novel concept of state-space based hybrid-damping technique, which is an appropriate combination of passive and active damping, in order to make grid-interconnection reliable and robust which can ensure adequate stability margin in all possible grid interactive conditions.

An integrative approach to the design methodology for 3-phase power conditioners in Photovoltaic Grid-Connected systems

A novel methodology is presented in this paper, for the design of the Power and Control Subsystems of a 3-phase Photovoltaic Grid-Connected system in an easy and comprehensive way, as an integrative approach. At the DC side of the Power Subsystem, the Photovoltaic Generator modeling is revised and a simple model is proposed, whereas at the AC side, a vector analysis is done to deal with the instantaneous 3-phase variables of the grid-connected Voltage Source Inverter. A d– q control approach is established in the Control Subsystem, along with its specific tuned parameters, as a vector control alternative which will allow the decoupled control of the instantaneous active and reactive powers. A particular Case of Study is presented to illustrate the behavior of the design methodology regarding the fulfillment of the Photovoltaic plant specifications. Some simulations are run to study the performance of the Photovoltaic Generator together with the exerted d– q control to the grid-connected 3-phase inverter, and some experimental results, obtained from a built flexible platform, are also shown. The simulations and the experimental results validate the overall performance of the 3-phase Photovoltaic Grid-Connected system due to the attained unitary power factor operation together with good power quality. The final validation of the proposed design methodology is also achieved.

A Cascaded Photovoltaic System Integrating Segmented Energy Storages With Self-Regulating Power Allocation Control and Wide Range Reactive Power Compensation

This paper presents a single-phase photovoltaic (PV) system integrating segmented energy storages (SES) using cascaded multilevel inverter. The system is designed to coordinate power allocation among PV, SES, and utility grid, mitigate the overvoltage at the point of common coupling (PCC), and achieve wide range reactive power compensation. The power allocation principle between PV and SES is described by a vector diagram. Accordingly, a sophisticated power allocation strategy is developed to allocate power between PV and SES based on a novel discrete Fourier transform (DFT) phase-locked loop (PLL) method. An appropriate reactive power allocation coefficient (RPAC) is designed to avoid duty cycle saturation and overmodulation so that wide range reactive power compensation and good power quality can be achieved simultaneously. The self-regulating power allocation control system integrating the preferred RPAC and an advanced active power control algorithm is developed to achieve the aforesaid objective. A 3.5-kW single-phase grid-connected cascaded PV system was built and tested at 1.6 kW in the laboratory. Simulation and experimental results are provided to demonstrate the effectiveness of the proposed cascaded PV system integrating SES.

Electrically Pumped Vertical External Cavity Surface Emitting Lasers Suitable for Passive Modelocking

Modelocked optically pumped vertical external cavity surface emitting lasers (VECSELs) have generated up to 6.4-W average power, which is higher than for any other semiconductor lasers. Electrical pumping of modelocked VECSELs is the next step toward a higher level of integration. With continuous wave (cw) electrically pumped (EP) VECSELs, an average output power of 900 mW has been demonstrated from the undisclosed proprietary novalux extended cavity surface emitting laser (NECSEL) design. In contrast, modelocked NECSELs have only been demonstrated at 40 mW. Recently, we presented a numerical study of EP-VECSELs suitable for modelocked operation; here, we demonstrate the first realization of this design. Power scaling is achieved with a lateral mode size increase. The competing electrical and optical requirements are, on the electrical side, low ohmic resistance, and on the optical side, low optical losses and low dispersion. Additionally, the device needs to operate in a fundamental mode for stable modelocking. We have fabricated and characterized 60 EP-VECSELs with varying dimensions and compared their lasing performance with our numerical simulations. The tradeoff between good beam quality and output power is discussed with an outlook to the modelocking of these EP-VECSELs. Initial EP-VECSEL devices have generated >;100 mW of cw output power.

Survey of actual viewing conditions at home and appropriate luminance of LCD‐TV screens

Abstract— To understand actual viewing conditions at home is important for TV design. And the preferred luminance level of LCD TVs under actual viewing conditions is also important in order to obtain both good picture quality and low power consumption. The actual viewing conditions of households and the preferred luminance levels was investigated. In a field test of 83 households, the display luminance, screen illuminance, and viewing locations were measured on site. In laboratory experiments, young and elderly subjects adjusted the luminance of an LCD‐TV screen to their preferred levels under different screen illuminance levels, angular screen sizes, and average luminance levels (ALL) of the images. As a result, two equations, which represent the preferred luminance level of LCD‐TV screens corresponding to different viewing conditions for young and elderly subjects were obtained. When the ALL of the images was 25% and the screen illuminance and angular screen size were set at 100 lx and 20°, respectively, the preferred luminance was 1 60 cd/m2 for the young subjects and 248 cd/m2 for the elderly subjects. By using the setting of the preferred luminance of an LCD TV under actual viewing conditions, it is possible to conserve energy consumption.

Voltage Sag Compensation of Point of Common Coupling (PCC) Using Fault Current Limiter

In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure of fault current limiter (FCL) is proposed. The proposed structure prevents voltage sag and phase-angle jump of the substation PCC after fault occurrence. This structure has a simple control method. Using the semiconductor switch (insulated-gate bipolar transistor or gate turnoff thyristor at dc current rout leads to fast operation of the proposed FCL and, consequently, dc reactor value is reduced. On the other hand, the proposed structure reduces the total harmonic distortion on load voltage and it has low ac losses in normal operation. As a result, other feeders, which are connected to the substation PCC, will have good power quality. Analytical analysis and simulation results using PSCAD/EMTDC software and experimental results are presented to validate the effectiveness of this structure.

Energy Management Techniques For Improvement Energy Efficiencies For Energy Conservation At District Energy Distribution Centers

The fundamental goal of energy management is to produce goods and provides services with least cost and least environmental effect. The objective of Energy Management is to achieve and maintain optimum energy procurement and utilization throughout the organization. The primary objective of Energy Audit is to determine ways to reduce energy consumption per unit of product output or to lower operating costs. This paper focuses on a case study for local energy Distribution Company urban division was taken and provides a “bench-mark” (Reference point) for managing energy in the organization and also provides the basis for planning a more effective use of energy throughout the organization. Testing and calibration of all the major equipment under the jurisdiction of urban division Kolhapur is studied. Energy auditing will assist in profit center approach at each level as indicated Level of auditing, Distribution Transformer, Zonal level, District Level, Circle Level. How there should be effectively application of Modernization of Distributions is studied. Also how there should be digital automation of distribution for Better quality of power, Better supply continuity, Stability in the voltage, Lower system losses, Minimize outage time and Better customer service is explained in the case study

18.2: Distinguished Paper: Appropriate Luminance of LCD‐TV Screens under Actual Viewing Conditions at Home

AbstractThe preferred luminance level of LCD televisions under actual viewing conditions is important to obtain both good picture quality and low power consumption. We investigated actual viewing conditions of households and preferred luminance levels. As a result, we obtained equations which represent the preferred luminance level corresponding to different viewing conditions.

Control of power converters for microgrids

PurposeNowadays, distributed generation and microgrids (MGs) are becoming an important research line because of their peculiar characteristics. MGs are composed of small power sources which can be renewable, placed near customer sites. Moreover, they have the inherent property of islanding: the disconnection of either the MG from the main grid or a part of a MG from the rest of the MG. The purpose of this paper is to study two different control strategies allowing grid connected and islanding operation of the MG.Design/methodology/approachIn this paper, the behaviour of a particular MG during grid connected and islanding operation is investigated. The studied MG is based on different energy sources: a wind turbine, a photovoltaic array, a backup diesel generator and a storage system. The renewable sources and the storage system are connected on a DC bus which is interconnected with a main grid through a voltage source inverter (VSI). The attention focuses on the control technique of the VSI during grid connected and islanding operation of the MG. The behaviour of the AC signals on the point of common coupling between the MG and the main grid as well as the DC signals on the DC bus on which are connected renewable energy sources of the MG has been investigated by simulation using a MATLAB/Simulink model.FindingsFor the investigated MG, the simulation results show that using a single master VSI and classical control strategies, it is possible to have a good power quality on the MG during grid connection and islanding operation.Originality/valueThis paper investigates the behaviour of a particular MG in order to analyse two different control strategies allowing grid connected and islanding operation.

Evolutionary algorithm based optimization for power quality disturbances classification using support vector machines

Classification and detection of power signal disturbances are most essential to ensure the good power quality. The power disturbance signals are non-stationary in nature. Non-stationary signal classification is a complex problem and equally a difficult task. In this paper we present a new method for accurate classification of power quality signals using Support Vector Machines (SVM) with Optimized Time-Frequency Kernels by a stochastic genetic algorithm. The Cohen’s class of time-frequency-transformation has been chosen as the Kernel for the SVM. An Evolutionary Algorithm has been used to optimize the parameters of the Kernels. The proposed classification method with optimized parameters is promising for classification of such non-stationary signals. Comparative simulation results demonstrate a significant improvement in the classification accuracy in case of these optimized Kernels. The important contribution of the paper is the optimization of the Kernels for the power system signal classification problem.

Diode-pumped cw Nd:YAG three-level laser at 869 nm

We report for the first time (to our knowledge) a diode-pumped Nd:YAG laser emitting at 869 nm based on the (4)F(3/2)-(4)I(9/2) transition, generally used for a 946 nm emission. Power of 453 mW at 869 nm has been achieved in cw operation with a fiber-coupled laser diode emitting 35.4 W at 809 nm. Intracavity second-harmonic generation in the cw mode has also been demonstrated with power of 118 mW at 435 nm by using a BiB(3)O(6) nonlinear crystal. In our experiment, we used a LiNbO(3) crystal lens to complement the thermal lens of the laser rod, and we obtained good beam quality and high output power stability.

FPGA기반 멀티레벨 인버터의 다중 반송신호 PWM 기법 구현

Multi-level inverters have drawn much of attention in recent years because it can meet the demand of high power applications and good power quality associated with reduced harmonic distortion. As the number of voltage level increases, field programmable gate arrays (FPGAs) are suitable for the implementation of multi-level modulation algorithm. This paper proposes the implementation method for generating PWM pulses at the three phase diode clamped five-level inverter using FPGA. The strategy for communicating stably the data of three-phase reference voltages between the DSP and FPGA is suggested. The techniques for generating PWM signals based on a multi-carrier modulation method are carried out through the experiments with 32-bit DSP and Cyclone-III FPGA.

家庭の視聴環境に即した液晶テレビの最適表示輝度

The preferred luminance level of LCD televisions under real viewing conditions to obtain both good picture quality and low power consumption is a rather controversial issue. The relationship between the preferable luminance and major parameters that affect it were investigated in a field test and laboratory experiments. In the field test of 83 households, the illuminance and luminance of television screens and television viewing distances were measured on site. The results indicated that the mean display luminance was 269 cd/m2 for LCD televisions. The median screen illuminance was 92 lx and the median viewing distance was 252 cm. In laboratory experiments, younger and older subjects adjusted the luminance of an LCD television screen to their preferred levels under different screen illuminance levels, angular screen sizes and average luminance levels (ALL) of images. Based on the results, the preferred luminance of LCD television screens for younger and older subjects is represented as two formulas. When the ALL of images was 25% and the screen illuminance and angular screen size were set at 100 lx and 20°, respectively, the preferred luminance was 160 cd/m2 for younger subjects and 248 cd/m2 for older subjects. By setting the preferred luminance of an LCD television under real viewing conditions, it is possible to not only reduce visual fatigue but also to conserve energy consumption.

Control strategy and space vector modulation for three-leg four-wire voltage source inverters under unbalanced load conditions

One of the desirable characteristics of inverters in three-phase systems is the ability to feed unbalanced/non-linear loads with voltage and frequency nominal values. Therefore three-leg four-wire inverters are expected to play an essential role in future power systems because of their ability to handle the neutral current caused by unbalanced or non-linear loads. This study introduces an original control method in combination with three-dimensional space-vector modulation (3D-SVM) strategy. The steps for the 3D-SVM implementation are identified. The switching vectors, 3D-SVM diagrams and the boundary planes equations, as well as the matrices for the duty cycles and symmetric switching sequences are discussed in detail. Experimental results including different loads are presented to validate the proposed SVM control strategy for three-leg four-wire voltage source inverters. The experimental results of this study show that the developed control scheme in combination with three-leg four-wire inverters can carry out the grid feeding requirements and supply good power quality to loads under extreme unbalanced conditions efficiently.

Development of a Compact Switched-Reluctance Motor Drive for EV Propulsion With Voltage-Boosting and PFC Charging Capabilities

This paper presents a compact battery-powered switched-reluctance motor (SRM) drive for an electric vehicle with voltage-boosting and on-board power-factor-corrected-charging capabilities. Although the boost-type front-end DC/DC converter is externally equipped, the on-board charger is formed by the embedded components of SRM windings and converter. In the driving mode, the DC/DC boost converter is controlled to establish boostable well-regulated DC-link voltage for the SRM drive from the battery. During demagnetization of each stroke, the winding stored energy is automatically recovered back to the battery. Moreover, the regenerative braking is achieved by properly setting the SRM in the regenerating mode. The controls of two power stages are properly designed and digitally realized using a common digital signal processor. Good winding current and speed dynamic responses of the SRM drive are obtained. In addition, the static operation characteristics are also improved. In the charging mode, the power devices that were embedded in the SRM converter and the three motor-phase windings are used to form a buck-boost switch-mode rectifier to charge the battery from utility with good power quality. All constituted circuit components of the charger are placed on board, and only the insertion of power cords is needed.

An electronic solution for the direct connection of a three-phase induction generator to a single-phase feeder

This paper proposes a solution for the direct connection of a three-phase induction generator to a single-phase feeder. This high power quality system is intended to be used in micro-hydro power plants applications with control of the water flow. It is employed to maintain the speed of the induction generator greater than its synchronous value. The difference between the generated power and the power consumed by the local load flows through the single-phase feeder. The power flow control is provided by a three-phase PWM inverter that additionally guarantees the local power quality. A system with good power quality must have sinusoidal and constant amplitude voltages, fixed frequency operation, balanced induction generator voltages and currents, harmonics and reactive power compensation. The paper describes the inverter control strategy, presents design criteria of the controllers, and shows experimental results.

Improvement of electrical arc furnace operation with an appropriate model

Electrical arc furnaces are commonly employed in industry to produce molten steel by melting iron and scrap steel. Furnace control is a necessary operation for production optimization. The principal parameters to be controlled are: maximum productivity requirements, minimum power off time, good power quality and safety. The aim of this study is to achieve all these objectives. Hence, because of the stochastic and dynamic behaviour of the arc during the melting process, a proposed model is checked with measurements at an industrial electrical arc furnace. How electrodes position and transformer taps can affect X and R arc function are discussed in detail. This new operating strategy has been determined taking into account Flicker, melting stages and electrode positions. It is shown that optimum efficiency can be reached by the integration of the proposed model in regulation loop.

Singly-resonant sum frequency generation of visible light in a semiconductor disk laser

In this paper a generic approach for visible light generation is presented. It is based on sum frequency generation between a semiconductor disk laser and a solid-state laser, where the frequency mixing is achieved within the cavity of the semiconductor disk laser using a single-pass of the solid-state laser light. This exploits the good beam quality and high intra-cavity power present in the semiconductor disk laser to achieve high conversion efficiency. Combining sum frequency mixing and semiconductor disk lasers in this manner allows in principle for generation of any wavelength within the visible spectrum, by appropriate choice of semiconductor material and single-pass laser wavelength.

Design and Control for a Charge-Regulated Flyback Switch-Mode Rectifier

This paper presents the design and control of a single-stage charge-regulated varying-frequency flyback switch-mode rectifier (SMR). First, the ratings of key constituted circuit components are derived, and accordingly, the power circuit is designed and implemented. Then, a novel charge-regulated, varying-frequency, current-controlled pulsewidth modulation (CCPWM) switching scheme is developed. In the proposed control scheme, the switch turn-on time is fixed, and the turn-off time interval is determined by the comparison result between the low-pass filtered switch current and its current command. The proposed switching scheme possesses the features of without slope compensation, having more dispersedly distributed harmonic spectrum, robust current tracking control, and ease of implementation using off-the-shelf integrated circuits. Finally, the quantitative and robust voltage regulation controls considering nonlinear behavior are made. Good dc output voltage regulation and ac input power quality control performances under wide load range are obtained. Some simulated and measured results are provided to demonstrate the performance of the developed SMR.

On the Front-End Converter and Its Control for a Battery Powered Switched-Reluctance Motor Drive

This paper presents the development of a front-end converter and its control for a battery powered switched-reluctance motor (SRM) drive. In motoring mode, the converter is operated as a dc-dc boost converter to establish dynamically boostable and well-regulated dc-link voltage from battery. The digital control schemes of boost converter and motor drive are implemented using a common digital signal processor. A proper voltage boosting feedback controller is designed to effectively enhance the SRM winding current and speed dynamic responses. Then the robust speed control performance is achieved by the proposed control scheme consisting of robust disturbance feedforward control and variable-structure system control. In addition, an effective regenerative braking control scheme for SRM is developed. In idle charging mode, the proposed front-end converter is arranged to act as a buck-type switch-mode rectifier (SMR) for charging the battery with good line power quality. Four diodes embedded in the SRM converter and the two motor phase winding inductances are employed to form the necessary constituted components of the SMR. The circuit and controller designs are presented, and good charging power conditioning performance is demonstrated experimentally.