Entire Simulation Model Research Articles

Novel Manta Rays Foraging Optimization Algorithm Based Optimal Control for Grid-Connected PV Energy System

Large-scale photovoltaic system (PV) installation can affect power system operation, stability, and reliability because of the non-linear characteristic of the PV system installation. DC/AC and DC/DC converters are the major devices use in connecting PV into the grid. These converters are liable to power quality problem if the proper control mechanism is not adopted. This study presents an optimal control technique to improve dynamic operation of PV grid-connected system. An optimal control method with use of Manta ray foraging optimization (MRFO), is implemented as a control strategy for tuning the proportional-integral (PI) controllers of DC/DC and DC/AC converters for the integration of the PV system into the grid. The MRFO is chosen because of its ease of implementation and requirement of less adjusting parameters. The effectiveness of the proposed technique is studied under irradiance variation. The obtained results demonstrate the superior performance of the MRFO over five other metaheuristic algorithms (i.e., grey wolf optimization, whale optimization, grasshopper optimization, atom search optimization, and salp swarm algorithm) in terms of convergence rate and optimal global solution capture. The entire simulation model is established using MATLAB editor and Simulink. The acquired transient result shows the functionality and viability of the MRFO approach.

Study of Indoor Ventilation Based on Large-Scale [DNS by a Domain Decomposition Method

This paper presents a large-scale Domain Decomposition Method (DDM) based Direct Numerical Simulation (DNS) for predicting the behavior of indoor airflow, where the aim is to design a comfortable and efficient indoor air environment of modern buildings. An analogy of the single-phase convection problems is applied, and the pressure stabilized domain decomposition method is used to symmetrize the linear systems of Navier-Stokes equations and the convection-diffusion equation. Furthermore, a balancing preconditioned conjugate gradient method is utilized to deal with the interface problem caused by domain decomposition. The entire simulation model is validated by comparing the numerical results with that of recognized experimental and numerical data from previous literature. The transient behavior of indoor airflow and its complexity in the ventilated room are discussed; the velocity and vortex distribution of airflow are investigated, and its possible influence on particle accumulation is classified.

Molecular Dynamics Simulation of Surface Effect on Tensile Deformation of Single Crystalline Copper

Based on molecular dynamics method, the tensile process of single crystalline Cu nanorod and single crystalline Cu bulk were simulated at atomic scale. The motion of atoms, total energy of atom-strain curves and number of dislocation atom-strain curves during the tensile process were acquired. The results shown that surface effect has a significant effect on the tensile mechanical properties of single crystalline Cu nanorod. For single crystalline Cu nanorod, the energy of atoms in the edges and surface were higher than the energy of atoms inside the nanorod. Dislocations nucleation in the edges that with high energy and extend along the {111} crystal plane. The nanorods produce plastic deformation and shows excellent ductility under the "dislocation nucleation-energy rising and dislocation layers cross-slip" mechanism of the alternating cycle. For single crystalline Cu bulk, dislocation nucleation randomly and extend to the entire simulation model along the {111} crystal plane quickly. The single crystalline bulk Cu produce fracture under the "microscopic vacancy-microscopic hole-penetration of microscopic holes-fracture" mechanism.

Fast start-up analyses for Benson heat recovery steam generator

In this study, an entire simulation model is developed to investigate the influence of fast gas turbine start-up (within 20 min) on the dynamic behavior of a Benson heat recovery steam generator. The model includes a new high pressure feedwater control concept that considers a large number of live plant parameters and derivative functions. The advanced feedwater control circuit offers the possibility to operate the high pressure system in level mode (nature circulation) or Benson mode (once-through). Furthermore, it provides a rapid response and ensures a save operation to Benson HRSG (heat recovery steam generator) during the GT (gas turbine) abrupt transients and fast start-up procedures. A set of enhanced steam bypass control circuits are also implemented in the model. The developed HRSG model and its advanced control circuits are validated toward the design data at different part loads. The obtained results demonstrate very good physical agreement with relative error less than 3% and cite as evidence that the Benson model represents the real power plant. Finally, different fast start-up procedures (hot, warm, cold) are assessed with the validated Benson model, which provides adaptable operation demands to meet the gas turbine fast start-up requirements.

Presentation of a virtual power plant environment and its application with combined first-principle and data-driven models intended for the diagnostics of a power plant – Part 1

This work aims to present and discuss the architecture and application aspects of the Virtual Power Plant (VPP) environment, a tool created for the purpose of modeling, simulation, data management, and visualization of power plant systems. The VPP environment is based on a general-purpose simulation package that provides a framework for incorporating a broad variety of models, ranging from real-time models to detailed models that require off-line execution. The VPP, as a tool, opens up the possibility to develop, test, and validate the feasibility of new software and hardware components within simulated operational scenarios. The first part of the work presents the architecture of the VPP and briefly describes its main components. The implementation, including necessary simplifications, encapsulation, and integration of sub-models is discussed and illustrated. A feedwater heater model is the main contributor to the performance of the entire simulation model of a power unit. In the first part of this work, the development process of such a model is presented, including necessary simplifications for improving its performance and functionality.

A feedwater heater model intended for model-based diagnostics of power plant installations

Work related to the first-principle modeling of a feedwater heater operating in a coal-fired power unit is presented, along with theoretical discussion concerning its structural simplifications, parameter estimation, and dynamical validation. The objectives of this work are as follows: (i) formulate and deploy a moderately complex first-principle model of a feedwater heater to reproduce operational measurements in real-time simulations, (ii) develop a tuning method for this model, (iii) propose key indicators of heater performance using a model-based approach, and finally (iv) automate the calculation process of the indicators. A feedwater heater model is the main contributor to the performance of the entire simulation model of a power unit. In this work, the development process of such a model is presented, including necessary simplifications for improving its performance and functionality. As a result of the proposed simplifications, performance which allows operational data to be tracked by means of continuously updating model parameters in real-time mode was achieved on a regular PC workstation for a series of six low- and high-pressure heaters. The model variables (e.g. variability of the power rate of energy exchange) and estimated parameter values were used to formulate key performance indicators intended for a model-based diagnostics approach. Validation was successfully performed using operational data from a 225 MW coal-fired power unit. ► The development process of the first-principle feedwater heater model is presented. ► The tuning and validation were conducted for a 225 MW coal-fired power unit. ► The model reproduces operational measurements for purpose of model-based diagnostics. ► The key performance indicators were proposed based on the model parameters. ► A parametric representation of the indicators facilitates a fault detection process.

Numerical Simulation Model for Predicting Air Quality along Urban Main Roads. 2nd Report Development of Photochemical Reaction Model.

A simulation model for predicting air quality along urban main roads is being studied. The previous report dealt with the development of atmospheric diffusion model, which will be the platform of the entire simulation model. The present report describes the development of a photochemical reaction model, which will be incorporated into the overall simulation program. Focusing on nitrogenoxides, a simplifed 4-component, 5-reaction model has been established. The validity of the model was verified by comparison with data obtained in a chamber experiment. More compelx models containing up to 30-component, 67-reaction have also been constructed to conduct performance comparisons with the simplified model. The difference in the calculated results among the models was found to be less than 1%. The simplified model was applied to a street canyon condition, and the reaction occurring there was visualized.

Simulation of Multivariable Control Systems with SIMCOS

In most cases, the entire simulation model of multivariable control systems itself is composed of different multidimensional subsystems. These can be process models, feedback control systems, state observer schemes, as well as deterministic signal models for reference variables and disturbances. The elements of the coupled multivariable subsystems are obtained by theoretical and numerical modelling and controller design procedures, using matrix-oriented state-space techniques, as well known. The presented program system SIMCOS, therefore, bases on the state-space formulation of multivariable systems and subsystems. For several reasons, SIMCOS is more suitable to simulations of complex linear systems than block-oriented and equation-oriented simulation languages, using scalar variables. Within the program SIMCOS (simulation of multivariable control systems) arbitrary subsystem structures can be defined, using a symbolic and matrix-oriented notation, and therefore it is more flexible than other multivariable simulators with predefined system structures. The composition of the entire simulation model is performed automatically, structure and dimension error detection included. In order to obtain high integration rates, a two pass simulation method with data reduction and zero-element detection in matrix calculations have been applied.