Unit sizing and control of hybrid wind-solar power systems

The aim of this paper is to provide the core of a CAD/CAA tool that can help designers determine the optimal design of a hybrid wind-solar power system for either autonomous or grid-linked applications. The proposed analysis employs linear programming techniques to minimize the average production cost of electricity while meeting the load requirements in a reliable manner, and takes environmental factors into consideration both in the design and operation phases. While in autonomous systems, the environmental credit gained as compared to diesel alternatives can be obtained through direct optimization, in grid-linked systems emission is another variable to be minimized such that the use of renewable energy can be justified. A controller that monitors the operation of the autonomous/grid-linked systems is designed. Such a controller determines the energy available from each of the system components and the environmental credit of the system. It then gives details related to cost, unmet and spilled energies, and battery charge and discharge losses     

Fuel-cell sharing for a distributed hybrid power system

This paper investigates the benefits of sharing a proton exchange membrane fuel cell (PEMFC) in a distributed hybrid power system. The PEMFC is usually used as backup power in stationary hybrid power systems; however, in that scenario, it might be working only 2% of the time while incurring 20% of the system expenses. Therefore, this paper examines the potential of sharing a PEMFC among multiple power systems. We develop a distributed hybrid power system that comprises several immovable power stations and a fuel-cell vehicle (FCV). Each power station is equipped with solar panels and batteries, while the FCV contains a PEMFC module and can move among the stations to provide sustainable power as needed. We propose power management strategies and show that the total system costs can be significantly reduced by 10.83% and 17.89% when sharing one FCV between three and twelve power stations, respectively. We also design experiments to demonstrate the feasibility of the proposed distributed hybrid power system. In the future, the developed model can be extended to provide further cost reductions by optimizing distributed hybrid power systems with multiple FCVs.     

A new method for dynamic performance improvement of a hybrid power system by coordination of converter's controller

In this paper, a new strategy for modeling and controlling a hybrid power generation system that contains a fuel cell (FC) and super capacitor (SC) system is proposed. The main drawback of FC systems is its slow dynamic because the FC current slope must be limited in order to prevent fuel starvation problems and to improve its efficiency and lifetime. To overcome this slow dynamic and to improve dynamic performance, a new control strategy is proposed to combine FC system with SC system. The proposed control strategy can be also used for cold starting and different types of FC systems with different dynamics. The control strategy is capable of determining the desired FC power to prolong FC system lifetime and keeps the AC and DC voltages around its nominal value in transient event by supplying propulsion power and recuperating FC energy. The minimum SC system is computed in new method and used to meet the load demand to constraint the DC bus voltage and enhances power regulation under various active and reactive load conditions. Two different case studies are used to obtain the simulation results using MATLAB/SIMULINK to verify the validity of the proposed control strategy.     

光伏电站远程控制系统的动态 IP 地址分配实现

一前言随着光伏技术的迅猛发展,光伏电站也日益增多。为了方便管理和监控光伏电站的运行、优化设计光伏电站,每个光伏电站都应具有远程数据传输能力。远程监控系统主要对以下数据实时监控并建     

离网光伏电站智能控制系统的通信模块设计

介绍了一种基于低压电力载波的通信模块.该模块作为离网光伏电站智能控制系统的通信单元.实现各用户电表数据和控制信号的实时传输,为实现离网光伏电站自动化集中抄表和远程控制奠定了基础.文章详细阐述了该通信模块软、硬件设计方法和仿真结果.     

Adaptive control of a fuel cell-microturbine hybrid power plant

The composition of natural gas may vary significantly, and load power varies randomly. Traditional control design approaches consider a fixed operating point in the hope that the resulting controller is robust enough to stabilize the system for different operating conditions. On the other hand, adaptive control incorporates the time-varying dynamical properties of the model and considers the disturbances acting at the fuel cell-microturbine hybrid power plant. It may be possible to identify the parameters of the adaptive controller. This scheme is called direct adaptive control, because we are going to obtain directly the required controller parameters through their estimation in an appropriately redefined plant model. An adaptive minimum variance controller is developed in this paper.     

Design optimization for the hybrid power system of a green building

This paper proposes an optimal design procedure for a green building equipped with renewable energy, energy storages, and proton exchange membrane fuel cells (PEMFCs). First, we introduce the hybrid power system of the green building and construct a simulation model using Matlab/SimPowerSystem?. The model parameters are tuned so that the system responses can be estimated without extensive experiments in the optimization processes. Second, we define the cost and reliability indexes to optimize the system design using three steps: component selection, component sizing, and power management (PM) adjustment. We further define the safety index to evaluate the system's sustainability under extreme conditions when no renewable energy is available. Last, we apply the proposed procedures to the green building and demonstrate the benefits of the optimal design. The proposed method can be directly applied to develop customized hybrid power systems in the future.     

Design of a mobile PEM power backup system through detailed dynamic and control analysis

In this paper we present a one dimensional dynamic model of a PEM fuel cell applied to the design of a mobile backup system for uninterruptable power units. The fuel cell is modeled using a finite difference approach where mass and energy balance equations are applied locally together with the pertinent equations of the electrochemical model yielding the profiles of any relevant thermodynamic and electrochemical cell variable. An accurate analysis of the membrane humidification is included based on state of the art models available in literature.     

Inverse dynamic analysis type of MPPT control strategy in a thermoelectric-solar hybrid energy harvesting system

This study presents the development of a novel inverse dynamic analysis-maximum power point tracking (IDA-MPPT) scheme in a hybrid energy harvesting system between thermoelectric module (TEM) and solar array (SA). The proposed method initially changes the harvested voltage response from both sources to be the third-order exponential function. This input function selection is based on the capability of this function to stabilize the initial response system and maintain its final position despite a prolonged response time. The mV voltage value from TEM is easily boosted up to nearly 5 V using this method. With this hybridization, the total obtained voltage is doubled to become 9.7 V, which results in a total power of 0.722 W. Furthermore, the method also allows for a fast tracking system, which enables faster voltage boosting and supercapacitor charging. The supercapacitor only requires less than 5 min to complete charging and boost the voltage to almost 5 V. Thus, a satisfactory value is obtained as compared with that of the TEM system with a chosen MPPC board.     

Development of a test facility for photovoltaic-diesel hybrid energy systems

To quantify the potential for performance improvements of photovoltaic-diesel (PV-diesel) hybrid energy systems, a test facility has been installed at the Centre for Renewable Energy Systems Technology. The research facility is part of the cooperative program to develop improved power conditioning systems for the provision of electricity in remote areas (ACRE Project 4.1). A customised control interface has been developed using the control and data acquisition software, LabVIEW. The graphical user-interface supports the automatic or manual definition of control parameters, which allows the system designer to apply optimal control methods for the management of PV-diesel hybrid energy systems. Continuously monitored weather data supports the integration of photovoltaic resource and load demand forecasts as part of the control strategy. The paper describes the developed test facility and discusses the potential for performance improvements of stand-alone renewable energy systems, which can be achieved through the application of “intelligent” energy management strategies.     

Optimization strategy for element sizing in hybrid power systems

This paper presents a procedure to evaluate the optimal element sizing of hybrid power systems. In order to generalize the problem, this work exploits the “energy hub” formulation previously presented in the literature, defining an energy hub as an interface among energy producers, consumers and the transportation infrastructure. The resulting optimization minimizes an objective function which is based on costs and efficiencies of the system elements, while taking into account the hub model, energy and power constraints and estimated operational conditions, such as energy prices, input power flow availability and output energy demand. The resulting optimal architecture also constitutes a framework for further real-time control designs.Moreover, an example of a hybrid storage system is considered. In particular, the architecture of a hybrid plant incorporating a wind generator, batteries and intermediate hydrogen storage is optimized, based on real wind data and averaged residential demands, also taking into account possible estimation errors. The hydrogen system integrates an electrolyzer, a fuel cell stack and hydrogen tanks. The resulting optimal cost of such hybrid power plant is compared with the equivalent hydrogen-only and battery-only systems, showing improvements in investment costs of almost 30% in the worst case.     

PEFC stacks as power sources for hybrid propulsion systems

In this paper the performance of two polymeric electrolyte fuel cell systems (FCS) for hybrid power trains are presented and discussed. In particular, an experimental analysis was effected on 2.4 and 20 kW stacks with the aim to investigate the energy management issues of the two FCSs for utilization as power sources in electric power trains for scooter and minibus, respectively. The stack characterizations permitted the effect of the main operative variables (temperature, pressure and stoichiometric ratio) on mean power density of cells to be evaluated. The FCS efficiency was evaluated and compared for the two traction systems, individuating the optimal operative conditions for automotive application and specifying the energy losses of the auxiliary components. The efficiency of both fuel cell systems resulted higher than 40% in a wide range of loads (100–600 mA/cm²), with maximum values close to 50%. The experimental characterization of the two power trains was carried out on dynamic test benches, able to simulate the behaviour of the two vehicles on the European R40 driving cycle. The characterization of the two propulsion systems on R40 driving cycle evidenced that the overall efficiency was not affected significantly by the hybrid configuration adopted, as the efficiency values ranged from 27 to 29% in the different procedures analyzed.     

Design of isolated renewable hybrid power systems

Isolated electrical power generating units can be used as an economically viable alternative to electrify remote villages where grid extension is not feasible. One of the options for building isolated power systems is by hybridizing renewable power sources like wind, solar, micro-hydro, etc. along with appropriate energy storage. A method to optimally size and to evaluate the cost of energy produced by a renewable hybrid system is proposed in this paper. The proposed method, which is based on the design space approach, can be used to determine the conditions for which hybridization of the system is cost effective. The simple and novel methodology, proposed in this paper, is based on the principles of process integration. It finds the minimum battery capacity when the availability and ratings of various renewable resources as well as load demand are known. The battery sizing methodology is used to determine the sizing curve and thereby the feasible design space for the entire system. Chance constrained programming approach is used to account for the stochastic nature of the renewable energy resources and to arrive at the design space. The optimal system configuration in the entire design space is selected based on the lowest cost of energy, subject to a specified reliability criterion. The effects of variation of the specified system reliability and the coefficient of correlation between renewable sources on the design space, as well as the optimum configuration are also studied in this paper. The proposed method is demonstrated by designing an isolated power system for an Indian village utilizing wind-solar photovoltaic-battery system.     

Comparative analysis of different grid-independent hybrid power generation systems for a residential load

Demand of electricity is rising all over the world, both in developing and developed countries due to escalation in world population and economic growth. The exploitation of renewable energy is imperative to mitigate energy crisis and to avoid the environmental downfall. The stochastic nature of many renewable energy sources sets techno-economic and functional limitations in their application for covering most types of energy needs. These limitations can be surmounted if a renewable and a conventional energy source are combined to formulate a hybrid generation power system.This paper examines the techno-economic feasibility of four hybrid power generation systems applied to cover the demand of a typical off-grid residence for a 20 years period. Each one of these hybrid power solutions should involve at least one renewable energy source technology and be able to cover all load needs. Four applications are investigated for each hybrid system, accounting to different geographical areas in Greece with diverse solar and aeolic profile. A comparative analysis is followed to set off the optimal solution based on a minimal total cost criterion.     

光伏电站复合储能电压波动抑制双层优化控制方法

大规模光伏电站的不断接入为电力系统的安全稳定运行带来了巨大挑战。为解决光伏电站出力不确定性所造成的功率波动问题,提高光伏电站在并网点处电压的稳定性,文章采用由蓄电池与超级电容组成的复合储能一体化控制方法,提高光伏并网点电压稳定水平。首先研究由光伏电源、复合储能构成的典型复合储能系统拓扑结构下储能双层优化控制策略;其次,在不同储能介质的荷电状态与充放电特性模型基础上,研究基于不同光伏并网点电压波动场景的多储能介质组合电压波动抑制优化控制模型及其求解算法;最后,以并网光伏电站数据为基础,建立光伏复合储能电压波动优化控制仿真模型。仿真结果及其分析表明,文章所提出的基于复合储能的并网点电压波动抑制模型能够有效提升并网点电压稳定性能。     

Dynamics and stability of a hybrid wind-diesel power system

Dynamic system analysis is carried out on an isolated electric power system consisting of a wind turbine generator (WTG) and a diesel engine generator (DG). The 150 kW wind turbine generator is operated in parallel with the diesel generator to serve an average load of 350 kW. A comprehensive digital computer model of a hybrid wind-diesel power generation system, including the diesel and wind power dynamics for stability evaluation, is developed. The dynamic performance of the power system and its control logic are studied, using the time domain solution approach. A systematic method of choosing the gain parameter of the wind turbine generator pitch control by the second method of Lyapunov that guarantees stability is presented. The response of the power system with the optimal gain setting to the random load changes has been studied. Analysis of stability has further been explored using the eigenvalue sensitivity technique.     

Control design and power management of a stationary PEMFC hybrid power system

This paper develops robust control and power management strategies for a 6 kW stationary proton exchange membrane fuel cell (PEMFC) hybrid power system. The system consists of two 3 kW PEMFC modules, a Li–Fe battery set, and electrical components to form a parallel hybrid power system that is designed to supply uninterruptible power to telecom base stations during power outages. The study comprises three parts: PEMFC control, power management, and system integration. First, we apply robust control to regulate the hydrogen flow rates of the PEMFC modules in order to improve system stability, performance, and efficiency. Second, we design a parallel power train that consists of two PEMFC modules and one Li–Fe battery set for the uninterruptible power supply (UPS) requirement. Lastly, we integrate the system for experimental verification. Based on the results, the proposed robust control and power management are deemed effective at improving the stability, performance, and efficiency of the stationary power system.     

Transient recognition control for hybrid fuel cell systems

Hybrid power systems combining fuel cells with fast energy storage devices are good solutions to the fuel cell load-following problem. Hybrid systems may also offer efficiency and reliability advantages. In this paper, we propose a power control scheme for hybrid systems that exploits feed-forward information about the steady-state behavior of incoming load transients. The method uses a modified cluster-weighted modeling (CWM) algorithm to build a load transient recognition model. The model is formulated sequentially and can provide useful feed-forward information in real time. Simulation and experimental results are provided that demonstrate the effectiveness of the transient recognition model and the proposed power control scheme for hybrid fuel cell systems.     

Techno-economical study of hybrid power system for a remote village in Algeria

The share of renewable energy sources in Algeria primary energy supply is relatively low compared with European countries, though the trend of development is positive. One of the main strategic priorities of NEAL (New Energy Algeria), which is Algeria's renewable energy agency (government, Sonelgaz and Sonatrach), is striving to achieve a share of 10–12% renewable energy sources in primary energy supply by 2010.This article presents techno-economic assessment for off-grid hybrid generation systems of a site in south western Algeria. The HOMER model is used to evaluate the energy production, life-cycle costs and greenhouse gas emissions reduction for this study. In the present scenario, for wind speed less than 5.0 m/s the existing diesel power plant is the only feasible solution over the range of fuel prices used in the simulation. The wind diesel hybrid system becomes feasible at a wind speed of 5.48 m/s or more and a fuel price of 0.162$/L or more. If the carbon tax is taken into consideration and subsidy is abolished, then it is expected that the hybrid system will become feasible. The maximum annual capacity shortage did not have any effect on the cost of energy, which may be accounted for by larger sizes of wind machines and diesel generators.     

Model-based optimal control of a hybrid power generation system consisting of photovoltaic arrays and fuel cells

Hybrid renewable energy systems are expected to become competitive to conventional power generation systems in the near future and, thus, optimization of their operation is of particular interest. In this work, a hybrid power generation system is studied consisting of the following main components: photovoltaic array (PV), electrolyser, metal hydride tanks, and proton exchange membrane fuel cells (PEMFC). The key advantage of the hybrid system compared to stand-alone photovoltaic systems is that it can store efficiently solar energy by transforming it to hydrogen, which is the fuel supplied to the fuel cell. However, decision making regarding the operation of this system is a rather complicated task. A complete framework is proposed for managing such systems that is based on a rolling time horizon philosophy.