Functional Predictive Control for Voltage Stability Improvements of Autonomous Hybrid Wind–Diesel Power System

This study investigates the application of the model predictive control technique for voltage stability of an isolated hybrid wind–diesel power system based on reactive power control. The proposed generation system mainly consists of a synchronous generator for a diesel-generator system and an induction generator for a wind energy conversion system. A static VAR compensator is used to stabilize load voltage through compensating reactive power. Two control paths are used to stabilize load bus voltage based on model predictive control. The first control path is used to adjust the total reactive power of the system by controlling the static VAR compensator firing angle. The second is proposed to control the excitation voltage of the synchronous generator. Model predictive control is used to determine t optimal control actions, including system constraints. To mitigate calculation effort and reduce numerical problems, especially in a large prediction horizon, an exponentially weighted functional model predictive control (F-model predictive control) is applied. The proposed controller was tested through step change in load reactive power plus step increase in input wind power. The performance of the proposed system with the proposed controller was compared with classical model predictive control; moreover, this scheme is tested against parameter variations.     

Power Electronic Converter Configurations Integration with Hybrid Energy Sources – A Comprehensive Review for State-of the-Art in Research

Abstract

The electricity demand is increasing day by day. On the other side, fossil fuels are depleting at a higher rate. The abundantly available renewable energy sources like solar, wind, and fuel cells are becoming popular sources of energy. But due to the intermittent availability of these renewable energy sources, two or more energy sources are integrated together. Power electronic converters are used for integrating different energy sources. Various power electronic converter (PEC) topologies have been proposed and analyzed in detail to control maximum power point, voltage, frequency, and harmonic distortions. Each of these configurations will differ in its topology and operating principle. The objective of this paper is to present a comprehensive review of various aspects of PEC configurations available for integration of renewable energy sources by systematization into three groups (AC shunt coupled, DC shunt coupled, and hybrid coupled systems). Emphasis is also given to coordination power control, maximum power point, and grid integration challenges related to the hybrid energy system. Furthermore, a general, system modeling of solar, wind, and grid integration is presented here to give an overall picture of a hybrid renewable energy system.     

Investigation of Buck-boost DC–DC Converter Operation in Discontinuous Conduction Mode (DCM) and the Effect of Converter Elements on Output Response Using a Mathematical Model Based on Laplace and Z-Transforms

In this paper, a new method based on Laplace and Z-transforms is proposed for mathematical modeling of a buck-boost DC–DC converter in discontinuous conduction mode (DCM). The Laplace transform is used to obtain the time response of the output voltage and inductor current. The Z-transform is used to analyze the transient and steady state responses. Using the determined initial values of output voltage and inductor current which are obtained by the final value theorem of Z-transform, the effect of converter elements on transient and steady state responses can be analyzed by using the proposed method. Finally, the results of theoretical analysis are compared to experimental and simulation results in PSCAD/EMTDC software.     

Application of Hybrid Differential Evolution–Grey Wolf Optimization Algorithm for Automatic Generation Control of a Multi-Source Interconnected Power System Using Optimal Fuzzy–PID Controller

This paper deals with an optimal hybrid fuzzy-Proportional Integral Derivative (fuzzy-PID) controller optimized by hybrid differential evolution–Grey Wolf optimization algorithm for automatic generation control of an interconnected multi-source power system. Here a two area system is considered; each area is provided with three types of sources namely a thermal unit with reheat turbine, a hydro unit and a gas unit. The dynamic performance of the system is analyzed under two cases: with AC tie-line and with AC-DC tie-line. The efficiency and effectiveness of the proposed controller is substantiated equally in the two cases. The sturdiness of the system is proved by varying the values of the system parameters. The supremacy of the recommended work is additionally ascertained by comparison with the recently published results like differential evolution optimized PID Controller and hybrid Local Unimodal Sampling-Teaching Learning based Optimization (LUS-TLBO) optimized fuzzy-PID controller. The dynamic performance of the system is observed in terms of settling time, peak overshoot and peak undershoot. Finally the analysis is extended by applying the proposed control technique in two different models namely (i) A three area unequal thermal system considering proper generation rate constraints (GRC) and (ii) A three area hydro-thermal system with mechanical hydro governor. These test results reveal the adaptability of the proposed method in multi-area interconnected power system.     

Multiple-Input–Multiple-Output Linear-Quadratic Control of the Energy Production of a Synchronous Generator in a Nuclear Power Plant

—A multiple-input–multiple-output linear-quadratic servo controller is proposed for a synchronous generator operating in a nuclear power plant that keeps the active power at the desired level and performs reactive power reference tracking using the reactive power demand from a central dispatch center. The controller design was based on the locally linearized version of a previous non-linear dynamical model of the synchronous electrical generator [1 Anderson, P., and Fouad, A., Power-Systems-Control and Stability, Ames, IA: The IOWA State University Press, Chap. 4, 1977. [Google Scholar], 2 Fodor, A., Magyar, A., and Hangos, K.M., Control-oriented modeling of the energy-production of a synchronous generator in a nuclear power plant, Energy, . 39, pp. 135–145, 2012.[Crossref], [Web of Science ®] , [Google Scholar]], the parameters of which have been identified using measured data from Paks Nuclear Power Plant (Hungary). The method can easily be applied to any industrial power plant generator connected to the electrical grid after estimating its parameters. The proposed observer-based multiple-input–multiple-output state feedback controller is a linear-quadratic servo controller with very good reference tracking and disturbance rejection properties, which were confirmed by simulation experiments.     

A Robust H∞ Controller Based Gain-scheduled Approach for the Power Smoothing of Wind Turbine Generator with a Battery Energy Storage System

Output power fluctuation of the wind turbine generator is a serious issue for power systems. The battery energy storage system is installed to the power system to solve this problem. However, the large battery energy storage system can increase the capital cost of the wind turbine generator system. Hence, the capacity of the battery should be reduced as much as possible. This article presents an H_∞ based control method for the output power smoothing method of the wind turbine generator by using a battery energy storage system. The output power fluctuation of the wind turbine generator is considered in the frequency domain. Low-frequency fluctuations are smoothed by pitch angle control of the wind turbine generator, while high-frequency variations are smoothed by charge or discharge of the battery energy storage system, respectively. The battery energy storage system’s capacity and mechanical stress of wind turbine blades can be reduced by the proposed method. In addition, the gain-scheduled control theory is applied to the pitch angle control system of the wind turbine generator. Therefore, the robust control performance for high non-linearities of the wind turbine generator model can be achieved. The effectiveness of the proposed method is validated by numerical simulations.     

Analysis and control of a single switch wider step-down gain DC–DC converter for low-voltage applications

This paper presents a point-of-load transformerless DC–DC converter having a wider step-down conversion ratio. In comparison with quadratic/stacked buck converter variants, the presented topology exhibits nonpulsating source current, more effective switch utilization at small voltage gains, and reduced current stress on components. Its comprehensive steady-state analysis is carried out under continuous and discontinuous modes of inductor currents, and design criteria to select L-C components are established. State variable dependency feature in the topology, imposing a reduced fourth-order dynamics, is discussed and subsequently verified from its average model. A fixed frequency sliding mode controller is then designed with a step-by-step evaluation of sliding surface existence, reachability, and stability conditions. The equivalent control law devised in this scheme is duly constituted from source side inductor current dynamics and load voltage error information, so it facilitates simple realization as well as better transient response. Remarkable operational characteristics of the presented converter are studied analytically and demonstrated with experimental observations on a laboratory prototype.     

Frequency Stabilization for Multi-area Thermal–Hydro Power System Using Genetic Algorithm-optimized Fuzzy Logic Controller in Deregulated Environment

Abstract—This article develops a model of load frequency control for an interconnected two-area thermal–hydro power system under a deregulated environment. In this article, a fuzzy logic controller is optimized by a genetic algorithm in two steps. The first step of fuzzy logic controller optimization is for variable range optimization, and the second step is for the optimization of scaling and gain parameters. Further, the genetic algorithm-optimized fuzzy logic controller is compared against a conventional proportional-integral-derivative controller and a simple fuzzy logic controller. The proposed genetic algorithm-optimized fuzzy logic controller shows better dynamic response following a step-load change with combination of poolco and bilateral contracts in a deregulated environment. In this article, the effect of the governor dead band is also considered. In addition, performance of genetic algorithm-optimized fuzzy logic controller also has been examined for various step-load changes in different distribution unit demands and compared with the proportional-integral-derivative controller and simple fuzzy logic controller.     

Design and Implementation of Adaptive Neuro–Fuzzy Inference System Based Control Algorithm for Distribution Static Compensator

This article focuses on the design and implementation of a distribution static compensator using an adaptive neuro–fuzzy inference system based controller. The distribution static compensator is controlled to provide power quality improvement, such as power factor correction, harmonics compensation, load balancing, and voltage regulation. Active and reactive power fundamental components of load currents are extracted using d-q theory. A distribution static compensator is realized using a voltage source converter. Both simulation and experimental results prove the effectiveness of the control algorithm under non-linear loads. The adaptive neuro–fuzzy inference system based controller works satisfactorily for power factor correction and harmonics reduction under balanced as well as unbalanced load conditions. Test results clearly depict the dynamics of the performance of the system under steady state as well as dynamics under load change and load unbalancing.     

Modeling and Management of Batteries and Ultracapacitors for Renewable Energy Support in Electric Power Systems–An Overview

Abstract—Energy storage devices and systems are playing a major role in all electrical systems from small electronics devices and automotive systems to the utility grid. The main objective of this article is to review energy storage devices, management, control, interface, and demonstrations for electrical power systems. Various types of energy storage systems are discussed, but the main focus is on batteries and ultracapacitors. Different types of batteries and their electrical models are explained. Three major types of ultracapcitors are also discussed. The battery management system and its functions, controls, and hardware are discussed. Various power electronics-based interface systems for battery and ultracapcitor charging and discharging are presented. Applications of energy storage systems for utility applications, including renewable firming, power shifting, and ancillary services, are discussed.     

Design and Implementation of a Class of Robust H ∞ Control for Stability Enhancement in Power Systems

The paper presents a method of designing a class of robust H X generator excitation controller in a power system. The proposed controller is utilized to damp inter-area oscillations and enhance power system stability. The robust controller design procedure for a linear composite system is presented in terms of positive definite solutions to modified algebraic inequalities. The resulting controller guarantees closed-loop stability and an H X -norm bound on disturbance attenuation. The effectiveness of the H X controller is demonstrated through digital simulation studies on a two-machine system. The digital simulation studies are conducted using a PSCAD/EMTDC software package. The simulation results show that the controller contributes significantly to the damping of inter-area oscillations and the enhancement of power system stability during disturbances.     

Analysis and Design of a Series–Parallel Uninterruptible Power Supply with an Improved Control Strategy for Seamless Transition

In this paper, a high-performance control structure is designed, implemented, and applied to a three-phase series–parallel uninterruptible power supply (UPS). This kind of UPS system provides input power factor correction, output voltage conditioning, and high efficiency. The control strategy proposed in this paper is based on voltage control of the parallel converter and current control of the series converter. It is shown that this strategy improves the system operation, specifically resulting in a smoother and more seamless transition between UPS operating modes. The controller in the proposed strategy is based on combination of two control methods with different characteristics and is therefore called a hybrid structure. To enhance the steady-state performance of the UPS and reach fast error convergence, a repetitive controller is used. In addition, to reach a fast transient response required for control of output voltage, a fast deadbeat is used. The stability of this hybrid controller is discussed, and the design procedure for a typical converter is given. For validation and verification of the theoretical analysis, both experimental and simulation results are shown.     

Novel high step-up DC–DC converter with increased voltage gain per devices and continuous input current suitable for DC microgrid applications

This paper suggests a nonisolated noncoupled inductor-based topology for direct current (DC)–DC converters for DC microgrids. The proposed configuration profits from advantages like high step-up capability, continuous input current, simple structure, reduced normalized standing voltage (NSV) on switches/diodes, large gain per devices, common ground point between source-load, and maximum power point tracking (MPPT) capability. Both the switches (T₁, T₂) are turned on/off simultaneously, which minimizes the number of operational modes and simplifies the control strategy. These properties lead to a more compact, less expensive, and lighter topology. The operational modes and steady-state analysis as well as design considerations have been presented in detail. According to comparative analysis, the voltage conversion ratio per number of devices in suggested topology is higher than that of other similar topologies addressed in literature. The simulation results extracted from PSCAD/EMTDC software and the experimental outcomes obtained from laboratory-scale prototype confirm the effectiveness and correct performance of proposed topology.     

Power Quality Improvement in Grid-connected Photovoltaic–Fuel Cell Based Hybrid System Using Robust Maximum Power Point Tracking Controller

This article addresses power quality improvement in a 3-Φ grid-connected photovoltaic–fuel cell based hybrid system using hybrid filter topology. In the context of the extraction of maximum power due to the uncertainty of solar insolation and temperature in the hybrid system, backstepping control is addressed for the DC-DC boost converter. A space vector pulse-width modulation control technique is implemented for the voltage source inverter for the grid integration objective. Compensation of the distorted waveform at the point of common coupling is accomplished by a suitable controller design using the hybrid filter. The series of simulation results in MATLAB environment (The MathWorks, Natick, Massachusetts, USA) followed by prototype experimental validation reflects the superiority of the proposed controllers to achieve power quality improvements.     

Characterization in a Wide Frequency Range (40 MHz–67 GHz) of a KTa0.65Nb0.35O3 Thin Film for Tunable Applications

A (100) oriented KTa_0.65Nb_0.35O₃ 400 nm-thin film has been deposited by Pulsed Laser Deposition on MgO substrate. Microwave measurements, performed on InterDigitated Capacitors, show a paraelectric phase at room temperature with a tunability for the devices of 64% under an electric field of 400 kV/cm. Then, using a specific de-embedding method, the complex permittivity of the KTN thin film has been extracted from 40 MHz up to 67 GHz on coplanar waveguides. As promising applications are pointed out at 60 GHz, such as indoor communications, material characterizations are expected in this spectrum.     

Implications of Carbon and Energy Taxes as Instrument for Environmental Emission Reduction in China＇s Power Sector

With the Integrated Resources Planning Assessment （IRPA） model, implications of carbon tax and energy tax on technological selection, power price and environmental pollution in power industry of China were studied. This model is a least-cost generation planning model, with which the technological composition, electricity price and pollutant emission can be calculated by comparing the cost changes for different power generation options due to carbon and energy taxes. The primary simulation result shows that the levy of US$ 25/tC carbon tax or US$ 0.5/Mbtu energy tax can improve the power generation structure and greatly reduce CO2, SO2 and NOx emissions in power industry. Several advanced power generation technologies such as IGCC and NGCC are of competitive cost, and should be given priority in future planning of power industry.     

Adjusting and Optimizing Structure of Energy Sources for Power Generation of Fujian Province in the 21st Century

DevelopingFujianprovincialelectricpowerindustryisanimportantlinkforexecutingthestrategicarrangementofnationaleconomicconstructionofFujian.Fromnowtotheyearof2020,itwillbedividedintothreestages.Duringthefirststage(from1996to2000),thepowerindustrywilltransferfromthedelayedtypetotheadaptedtype;duringthesecondstage(from20()lto2010),fromtheadaptedtypetothein-step-developmenttype;duringthethirdstage(from2010to2020),fromtheinstep-developmenttypetothesuitableleaddevelopmenttype.Duringthisperiod,theele…     

Application of a system with distributed architecture for information acquisition and processing in tasks of active–adaptive voltage control in distribution electric grids

An active–adaptive control system for power grids with distributed architecture of data acquisition and processing is considered. The advantages of the proposed control principle are compared with commonly used methods. A domestic apparatus—a programmable recording bay controller (PRBC)—is described. This hardware was designed to measure the basic electrical parameters and create distributed systems for data acquisition and processing. The procedure is considered of supervisory control and data acquisition (SCADA) by the SONATA system based on a multicore distributed architecture having high reliability and supporting a rigid real-time mode. A full-function full-scale model of active–adaptive voltage control system (AAVC) was set up using proposed software and hardware. The AAVC makes it possible to use the results of calculating–measuring procedures to select a corresponding on-load tap-changer (OLTC) on the actual voltage levels in the nodes of distribution grid. This approach to centralized voltage control in distribution grids makes it possible to ensure the required level of voltage in the greatest possible number of power consumers owing to prediction of voltage change. The effect of emergencies (random failure of control equipment) during the operation of an active–adaptive voltage control system is analyzed. A qualitative evaluation of the effect of faults on regulation quality and choice of OLTC connection is carried out. It is shown that, for undisturbed operation of an active–adaptive voltage control system, additional diagnostic tools, backup, and data loss compensation are needed.     

Technical and Economic Index System for CO2 Emission Reduction in China’s Power Industry

The main technic and economic indices for carbon dioxide emission reduction of Chinese electric power industry are designed systematically in this paper.According to quantitative calculation and influe...     

Calibration of UHF Sensors for GIS： Comparison of Different Methods and Testing of a Calibration System Based on a Conical AntennaEI北大核心CSCD

Different methods of calibrating ultra high frequency（UHF） sensors for gas-insulated substations （GIS） were investigated in the past. The first approach was to use strip lines, triplates and TEM calibration cells. These cells had already been in use for years for example to test the electromagnetic compatibility of electronic devices. The smaller the size of the cell, the higher its bandwidth-but the cell should be large enough to not disturb the electric field with the installed sensor under test. To overcome this problem, a calibration procedure using a gigahertz transverse e- lectromagnetic（GTEM） test cell and a pulsed signal source were introduced in 1997. Although this procedure has many advantages and is easy to understand, measurements show several shortcomings of this calibration method. To overcome the disadvantages of the known systems, a calibration cell using a monopole cone antenna and a metallic ground plane were developed and tested. The UHF sensor was placed in a region with minimum distortion of the elec- tric field due to its installation. Experience shows that the new method for calibrating UHF sensors is necessary in or- der to overcome the limits in the calibration of large sensors and to suppress the propagation of higher order modes and reflections. Due to its surprisingly simple structure, its low price and low overall measurement uncertainty, it is the preferred method for calibrating UHF sensors for GIS applications.