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.     

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.     

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.