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This paper proposes an ac-linked hybrid wind/photovoltaic (PV)/fuel cell (FC) alternative energy system for stand-alone applications. Wind and PV are the primary power sources of the system, and an FC-electrolyzer combination is used as a backup and a long-term storage system. An overall power management strategy is designed for the proposed system to manage power flows among the different energy sources and the storage unit in the system. A simulation model for the hybrid energy system has been developed using MATLAB/Simulink. The system performance under different scenarios has been verified by carrying out simulation studies using a practical load demand profile and real weather data. Index Terms--Alternative energy, electrolyzer, fuel cell (FC), hybrid, photovoltaic (PV), power management, stand-alone, wind.

This paper presents a physically based dynamic model for tubular solid oxide fuel cells (SOFCs) based on the electrochemical and thermodynamic characteristics inside SOFC. The diffusion, material conservation, electrochemical, and thermodynamic equations are used to develop the SOFC model. The effect of temperature on the steady-state (V-I and P-I) characteristics of the SOFC model has been studied, and the model responses have been obtained for constant fuel flow as well as for constant fuel utilization operating modes. The dynamic characteristics of the model are investigated in small, medium, and large timescales, from milliseconds to minutes. The model has been implemented in MATLAB/Simulink and used to investigate the distributed generation applications of SOFCs. Index Terms--Constant fuel flow, constant fuel utilization, distributed generation, dynamic model, fuel cell, operating mode, solid oxide fuel cell (SOFC), timescale.

This paper presents some application studies of the dynamic solid oxide fuel cell (SOFC) model developed by the authors and reported in C. Wang and M. H. Nehrir, 'A physicallybased dynamic model for solid oxide fuel cells,' IEEE Trans. Energy Convers. First, the model is used to investigate the short-time overloading capability of the SOFC. Then, the application of the model in distributed generation (DG) system studies is explored. Controller design methodologies are also presented for grid-connected SOFC DG power conditioning units to control power flow from the SOFC DG to the utility grid. Simulation results show that the SOFC DG system is able to manage real and reactive power flows to the utility grid to which it is connected. They also show that a properly designed SOFC DG can remain stable under temporary electrical faults. Index Terms--Distributed generation (DG), dynamic model, fuel cell, overloading, power management, solid oxide fuel cells (SOFCs).

In this paper, a load transient mitigation technique for stand-alone fuel cell (FC)--battery power generation systems is proposed. The technique can be used not only to improve the output power quality of the overall system, but also to mitigate or eliminate the electrical feedback stresses that are caused by load transients upon fuel cells. As a result, the durability of the fuel cell can also be improved. System analysis and controller design procedure for the proposed technique are given in this paper. Simulation studies have been carried out on FC-battery power generation systems using the dynamic models developed for proton exchange membrane fuel cell (PEMFC) and solid-oxide fuel cell (SOFC). Simulation results show the effectiveness of the proposed technique in preventing load transients from affecting the fuel cell performance. Index Terms--Battery, fuel cell (FC), stand-alone, transient mitigation.

Six steady-state fuel cell electrical terminal models are compared using experimental data from an Avista Laboratories SR-12 500 W proton exchange membrane (PEM) fuel cell. The paper begins by reviewing the physical effects in a fuel cell. The proposed electrical terminal models are introduced in terms of these physical effects, parameterized for identification and compared using the measured data. Index Terms--Fuel cells, modeling, static behavior.

The phenomenon of unintentional islanding occurs when a distributed generator (DG) continues to feed power into the grid when power flow from the central utility source has been interrupted. This phenomenon can result in serious injury to the linemen who are trying to fix the power outage problem. Several techniques have been proposed in the past to avoid such an occurrence. This paper first gives an overview of the dominant islanding detection techniques. Then, the principles of two of the suggested techniques are combined to obtain a new hybrid islanding detection technique for synchronously rotating DGs. Simulation results show that the proposed hybrid technique is more effective than each of the techniques used. Simulation results are given for two testbeds to verify the advantages of the proposed hybrid islanding detection technique. Index Terms--Distributed generators (DGs), islanding, microgrid (MG), point of common coupling (PCC).

An assessment of the economic benefits of using fuel cells is presented. A calculation of the cost of electricity generated from a fuel-cell installation, and a determination of the amount of profit that might result from an installation is given. A break even and sensitivity analysis is also conducted to determine what goals need to be achieved to make fuel cells competitive with conventional power generation sources. The study was performed using a graphical user interface programmed in MATLAB. Index Terms--Economic evaluation, fuel cells, graphical user interface (GUI).

This paper presents the development of dynamic models for proton exchange membrane (PEM) fuel cells using electrical circuits. The models have been implemented in MATLAB/SIMULINK and PSPICE environments. Both the double-layer charging effect and the thermodynamic characteristic inside the fuel cell are included in the models. The model responses obtained at steady-state and transient conditions are validated by experimental data measured from an Avista Labs SR-12 500-W PEM fuel-cell stack. The models could be used in PEM fuel-cell control related studies. Index Terms--Dynamic model, electrical circuit, PEM fuel cell, validation.

Power system deregulation and the shortage of transmission capacities have led to increased interest in distributed generation (DG) sources. Proper location of DGs in power systems is important for obtaining their maximum potential benefits. This paper presents analytical methods to determine the optimal location to place a DG in radial as well as networked systems to minimize the power loss of the system. Simulation results are given to verify the proposed analytical approaches. Index Terms--Analytical approach, distributed generation, optimal placement, power loss.

A fuzzy-logic-based adaptive power system stabilizer (PSS) is proposed in this paper. The parameters of the fuzzy-logic-based PSS are tuned by neural networks online. The system is divided into two subsystems, a recursive least square identifier with a variable forgetting factor for the generator and a fuzzy-logic-based adaptive controller to damp oscillations. The effectiveness of the proposed PSS in increasing the damping of local and inter-area modes of oscillation is demonstrated in a one-machine-infinite-bus system; a two-area, 4-machine, 13-bus system, and a 16-machine, 68-bus system. Index Terms--Fuzzy logic, neural networks, power system stabilizer.

This paper reports the development of a computer approach for evaluating the general performance of stand-alone wind/photovoltaic generating systems. Simple models for different system components are developed, integrated, and used to predict the behavior of generating systems based on available wind/solar and load data. The model is useful for evaluating the performance of stand-alone generating systems and gaining a better insight in the component sizes needed before they are built. Simulation results are presented for performance evaluation of a stand-alone generating system that has been previously designed to supply the average power demand of a typical residential house [1]. An electric water heater model is used as a dump load, and the excess available wind/solar-generated power is used to heat the water. The heated water is used as the inlet water to the main house water heater, which is assumed to be nonelectric. It is shown that this strategy can be effective in reducing the amount of fuel used by the main residential water heater. Index Terms--Computer modeling, electric water heater dump load, wind/PV generation.

Power management is an essential tool for microgrid (MG) safe and economic operation, particularly in the islanded operation mode. In this paper, a multi-timescale cost-effective power management algorithm (PMA) is proposed for islanded MG operation targeting generation, storage, and demand management. Comprehensive modeling, cost, and emission calculations of the MG components are developed in this paper to facilitate high accuracy management. While the MGs overall power management and operation is carried out every several minutes to hours, depending on the availability of the required data, simulation for highly dynamic devices, such as batteries and electric water heaters (EWHs) used for demand response (DR), are performed every minute. This structure allows accurate, scalable, and practical power management taking into consideration the intrainterval dynamics of battery and EWHs. Two different on/off strategies for EWH control are also proposed for DR application. Then, the PMA is implemented using the two different DR strategies and the results are compared with the no-DR case. Actual solar irradiation, ambient temperature, nonEWH load demand, and hot water consumption data are employed in the simulation studies. The simulation results for the MG studied show the effectiveness of the proposed algorithm to reduce both MGs cost and emission. [ABSTRACT FROM PUBLISHER]