Modeling Of Generator Research Articles

Dynamic Modeling and Analysis of a Virtual Synchronous Generator with Supercapacitor

With the continuous integration of new energy sources, the power system gradually begins to present the characteristics of a weak power grid. The system’s inertia decreases, leading to problems in the stability of the power grid. In this paper, a virtual synchronous generator model with a supercapacitor is analyzed. The supercapacitor provides additional virtual inertia to the system and suppresses system frequency disturbances more quickly. Bifurcation theory is used to analyze the nonlinear dynamics of the model. The bifurcation diagram of input active power is given in this paper, and the phase portraits and sequence diagrams of the frequency and power angle are presented to verify that, if the initial value of the system falls inside the stability region, the system can remain stable. If the initial value of the system falls outside the stability region, conversely, the system will lose stability. Finally, the simulation verifies the influence of the supercapacitor on the system inertia. The results show that the recovery speed of a small capacitance system is faster than that of a large capacitance system when disturbance occurs. It is concluded that, the smaller the supercapacitor is, the greater the virtual inertia it can provide.

Modeling and Emulation of a Synchronous Generator Considering Unbalanced Load Conditions

Modeling and Emulation of a Synchronous Generator Considering Unbalanced Load Conditions

Design and modeling of a free-piston engine generator

Design and modeling of a free-piston engine generator

Fully–coupled thermal–electric modeling of thermoelectric generators

Numerical models of thermoelectric generators require quantification of discretization uncertainty, the scrutinization of thermoelectric phenomena on model energy imbalances and simultaneous thermal–electric predictions, and the rectification of disagreement with analytic models when considering temperature-dependent material properties. Within this methods paper, two fully coupled, thermal–electric unicouple-level models are developed and evaluated over various thermal and electrical conditions to address the aforementioned issues—a numeric model in ANSYS CFX and an iterative analytic model. Model results were compared to ANSYS Thermal–Electric (TE) and ANSYS Fluent. Agreement between all models’ electrical and thermal predictions was achieved, albeit ANSYS Fluent’s thermal predictions exhibited high percent differences (7–8%) and had global energy imbalances on the order of 15% due to incongruent thermal–electrical power output predictions. ANSYS TE congruently predicts power output when considering the device’s thermal behavior and electrical performance separately, with disagreement on the order of a percent. Through incorporating all thermoelectric phenomena, ANSYS CFX’s global energy imbalances were hundredths to thousandths of a percent; exclusion of pertinent thermoelectric phenomena such as Thomson and Bridgman heating caused imbalances of tens of percent. The inclusion of Thomson heat is imperative when modeling thermoelectric devices. The analytic model’s thermal and electrical performance predictions are within ANSYS CFX’s uncertainty (2–5%), and these predictions yielded percent difference of less than 1% in comparison to ANSYS CFX when the unicouple produces ±50% maximum power. By using temperature-integrated averages of material properties, analytic modeling is sufficient for the thermal–electric characterization of unicouples with interconnectors operating under Dirichlet thermal boundary conditions.

Segmented thermoelectric generator modelling and optimization using artificial neural networks by iterative training

Renewable energy technologies are central to emissions reduction and essential to achieve net-zero emission. Segmented thermoelectric generators (STEG) facilitate more efficient thermal energy recovery over a large temperature gradient. However, the additional design complexity has introduced challenges in the modelling and optimization of its performance. In this work, an artificial neural network (ANN) has been applied to build accurate and fast forward modelling of the STEG. More importantly, we adopt an iterative method in the ANN training process to improve accuracy without increasing the dataset size. This approach strengthens the proportion of the high-power performance in the STEG training dataset. Without increasing the size of the training dataset, the relative prediction error over high-power STEG designs decreases from 0.06 to 0.02, representing a threefold improvement. Coupling with a genetic algorithm, the trained artificial neural networks can perform design optimization within 10 s for each operating condition. It is over 5,000 times faster than the optimization performed by the conventional finite element method. Such an accurate and fast modeller also allows mapping of the STEG power against different parameters. The modelling approach demonstrated in this work indicates its future application in designing and optimizing complex energy harvesting technologies.

Modeling of the Payload Signal Generator of the UAV Radio Transmitter based on the Phase Distortion Autocompensator

A block diagram of a payload signal generator of a UAV radio transmitter with an autocompensator for phase distortion of a digital computational synthesizer with improved spectral characteristics compared to known solutions is considered. Schematic diagrams and circuit design models of the main paths of the shaper in the Micro-Cap environment with the analysis of the characteristics of the necessary radio elements and microcircuits have been developed. The simulation of the device operation in the frequency domain is carried out. Based on the simulation results, the conditions for selecting the parameters of the shaper to achieve the greatest compensation of phase distortions are formulated.

Analytical Design and Simulation of a 9.3-GW Tesla Transformer for HPM Sources

This article presents a step-by-step design and modeling of a high-voltage pulse generator (PG) based on a Tesla transformer (TT) with an open-magnetic core to drive a low-impedance high-power microwave (HPM) source. Our design uses the OFF-resonance mode of operation for higher voltage transformation ratios. The pulse-forming line of the transformer is filled with deionized water for a higher energy density of the line and an increased output pulse duration. Maxwell equations are used to establish the transformer parameters such as the magnetizing and leakage inductances, and subsequently, the geometry of the TT for optimum power transfer between the resonant circuits. The required circuit parameters and geometry of the generator producing up to 250 kV and peak power of 9.3 GW when matched to a 6.7- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> load were determined through analytical design and validated through simulations.

Modeling and design optimization of a hybrid power generator for full-electric naval propulsion

The purpose of this work is to build a model of diesel engine useful for studying new hybrid solutions for power generation. This kind of study is of significant interest particularly for the marine sector, due to recent limitations on fuel consumption and constraints imposed on the minimum powertrain efficiency. In this paper a variable-speed diesel generator model is presented. The model simulates both the dynamic behavior of the engine and the fuel consumption during the operating cycle. This model was developed using experimental results of bench tests conducted on the VL1716C2-MLL engine by Isotta Fraschini Motori (IFM) SpA. Diesel engine dynamics is based on the formulation found in the technical literature on mean value models and then adjusted through experimental data. Special attention was paid to developing the procedure to find the minimum specific fuel consumption for a given load. Initially, the presented resutls concern the correct response of the model under different load conditions. Then, the improvement in specific fuel consumption (obtained by adjusting the engine speed according to the load), in comparison with fixed speed operation, is shown.

Modeling and simulation of a multistage heat recovery steam generator

As the share of renewable energy increases in modern power grids, their inherent intermittency compels existing thermal power plants to become more agile and flexible in their operation. To achieve such flexibility, understanding the transient behavior of thermal power plants is key. In this regard, physics-based dynamic models are useful tools. They help in predicting performance and in exploring various operating conditions in a risk-free, cost-effective manner. To this end, this paper presents a multi-stage Heat Recovery Steam Generator (HRSG) model. Fast simulations are demonstrated for this three pressure-stage system with interconnected thermodynamic and mass transfer phenomena. The HRSG’s multi-physics behavior is captured through mathematically modeled and numerically simulated phase change, fluid dynamics, and thermal coupling. Heat exchange elements such as economizers and superheaters are modeled by directly solving the Unsteady Flow Energy Equation (UFEE). The phase change dynamics of the boiler are modeled using a multi-mode switching mechanism, where each mode is characterized by boiling/evaporation/condensation and heating/cooling phenomena. A judicious combination of spatially discretized or lumped and dynamic or quasi-static models is used to achieve reasonably accurate transient response while lowering the computational burden. In collaboration with Siemens Energy Inc., steady-state prediction capability and transient pressure behavior are validated with plant startup data from an operational HRSG.

Modeling and validation of the thermoelectric generator with considering the change of the Seebeck effect and internal resistance

Thermoelectric generators (TEGs) produce power in direct proportion to the temperature difference between their surfaces. The Seebeck coefficient and internal resistance of the thermoelements (TEs) that make up the TEGs change depending on the temperature change. In simulation studies, it is seen that these two values are kept constant. However, this situation prevents approaching the data of TEG in real applications. In this study, a TEG Simulink/MATLAB ® model has been developed to capture real TEG module data, which considers changing of both the Seebeck coefficient and the internal resistance depending on the temperature difference change. To achieve this aim, a commercially available TEG data used in also academic studies has been used. A boost converter with a perturb and observe (P&O) maximum power point tracker (MPPT) algorithm has been designed to maximize the TEG power. The TEG Simulink/MATLAB ® model data are compared with commercially available TEG data at different temperatures. The error between the actual values and the simulation results, and the mean absolute percent errors (MAPEs) are calculated. The open circuit voltage and short circuit current error rates of the designed TEG module are 0.125% and 0.256%, respectively. The MAPE values of the designed model are 0.5104%, 0.7837%, and 2.0952% for 30 °C, 50 °C, and 80 °C cold surface temperatures, respectively. In addition, simulations are made in order to see the effect of temperature-dependent parameters in a TEG system built using the designed model. While the simulations made with the designed model give realistic results, with the simulations made with constant coefficients, up to 2.63% more power is obtained than the capacity of the system, contrary to reality. Simulation and validated results show that this new TEG Simulink/MATLAB® model gives more realistic results.

A Framework to Derive Synchronous Generator Modeling Parameters from Grid Connection Tests

Synchronous generator parameters are an important subset of input data to various power system studies. These parameters influence steady-state and dynamic behavior of the generator. This paper presents a framework to derive the parameters of a synchronous generator from grid connection test measurements. An industry standard generator model has been adopted to accurately match test measurements and simulation results obtained with the derived parameters. The proposed framework optimizes the parameters of the model to a higher accuracy level contributing to the fidelity of simulation results. A practical study is presented to demonstrate the performance of the proposed framework.

Downsizing the Linear PM Generator in Wave Energy Conversion for Improved Economic Feasibility

A crucial part of wave energy converters (WECs) is the power take-off (PTO) mechanism, and PTO sizing has been shown to have a considerable impact on the levelized cost of energy (LCOE). However, as a dominating type of PTO system in WECs, previous research pertinent to PTO sizing did not take modeling and optimization of the linear permanent magnet (PM) generator into consideration. To fill this gap, this paper provides an insight into how PTO sizing affects the performance of linear permanent magnet (PM) generators, and further the techno-economic performance of WECs. To thoroughly reveal the power production of the WEC, both hydrodynamic modeling and generator modeling are incorporated. In addition, three different methods for sizing the linear generator are applied and compared. The effect of the selection of the sizing method on the techno-economic performance of the WEC is identified. Furthermore, to realistically reflect the relevance of PTO sizing, wave resources from three European sea sites are considered in the techno-economic analysis. The dependence of PTO sizing on wave resources is demonstrated.

Detailed Transients Simulation of a Doubly Fed Induction Generator Wind Turbine System with the EMTP-Type OVNI Simulator

Doubly fed induction generator wind turbines are increasingly used in new wind turbine installations all over the world. Growing concerns about the impact of a large number of these generators on transient and voltage stability of power system networks has led engineers to revisit modelling and simulation practices used for system stability analyses. In this paper, the latest advancements in design of the general purpose power system simulator OVNI developed at the University of British Columbia are presented, and its application to the simulation of a doubly fed induction generator (DFIG) wind turbine system is shown. Because OVNI is based on the EMTP methodology for accurate detailed modelling, and the Multilevel MATE (Multi-Area Thévenin Equivalent) concept, which, combined with hardware solutions, allows for fast simulation of large power system networks, it represents an ideal tool for testing and developing benchmark models of different wind turbine installations. Using the EMTP approach for modelling of a DFIG wind turbine system and its feeding power network we were able to study the responses of the wind turbine generator to different network events. The ultimate goal of our investigations is the development of a benchmarking process for testing different models of wind turbine generators and determining the range of validity of various degrees of approximations normally used for stability simulation purposes. Due to the rapid development of wind generation technology, it is essential to determine the minimum requirements for dynamic modeling of wind turbine generators for assessing impacts of their installations on the dynamic security and stability of power systems.

Design and Analytical Magnetic Modeling of a Spherical Motion Generator With Multi-DOF Electromagnetic Actuation

This article proposes a novel spherical motion generator with integration of multi-degree-of-freedom actuation which brings out a more compact and flexible structure. The actuation is implemented by electromagnetic driving principle, and the spherical rotation is generated by the interaction between the iron-core coils and skewed stator permanent magnets, which helps increase the torque output. The magnetic field model is formulated analytically and validated using finite-element analysis. Finally, the cogging torque is modeled and the skewing of permanent magnets is discussed.

Dynamic Performance Enhancement of a Direct-Driven PMSG-Based Wind Turbine Using a 12-Sectors DTC

This paper focuses on the performance analysis, modeling, and control of permanent magnet synchronous generator (PMSG)-based wind energy conversion. This work analyzes controllers for the machine-side converter (MSC) and grid-side converter (GSC) and presents a new direct torque control (DTC) scheme based on a 12-sectors polygonal DTC for variable speed control of the PMSG. The proposed method solves the drawbacks faced by conventional six-sectors DTC control. The proposed method utilizes 12 sectors of 30° each compared to 60° in the conventional 6-sectors DTC. The 12-sectors technique was applied to voltages and flux vectors to increase the degrees of freedom for the selection of optimal vectors and, thus, reduce the torque ripple. This work analyzed the aforementioned DTC methods using MATLAB/Simulink, comparing the dynamic response of the proposed 12-sectors DTC with the conventional 6-sectors DTC control, and the results verified the effectiveness of the proposed DTC control.

Detailed mathematical and simulation model of a synchronous generator

Synchronous generator theory has been known since the beginning of its use, but the modelling and analysis of synchronous generators is still very existent in the present-day. Modern digital computers enable development of detailed simulation models, thus individual power system elements, including synchronous generators, are represented by the highest degree order models in power system simulation software packages. In this paper, first, a detailed mathematical model of a synchronous generator is described. Then, a simulation model of a synchronous generator developed based on the presented mathematical model. Finally, a transient stability after a short-circuit is simulated using real generator parameters.

Modeling and optimization of a rotational symmetric spherical triboelectric generator

Triboelectric nanogenerators (TENGs) are superb candidates to harvest low-frequency energy from water waves, wind, and ambient vibrations. They consist of triboelectrically-charged dielectric materials in relative motion and have been realized experimentally in several configurations and geometries. In this work, we provide a detailed mathematical analysis and fast computational method for designing spherical TENG devices to realize optimal performance. The method provides a self-consistent analysis to determine the charge distribution on spherical electrodes in compliance with the physical constraint of uniform potentials over the electrode surfaces. It is shown that the difference between the assumptions of a uniform potential vs. uniform charge density on electrodes for spherical TENG model parameters increases with the spatial dimensions of the electrodes relative to other characteristic dimensions of the TENG. For typical spherical TENGs the difference in harvested energy can be several percentages. A major benefit of the present model of a spherical TENG is its applicability to design large TENG network systems for which 3D methods, such as the finite element method, are computationally far too demanding.

Modeling, analysis and design optimizations of an axial-type piezoelectric energy generator for optimal output

This paper presents the optimal design of axial-based piezoelectric generators. The optimization problem is solved for the combination of the two different types of poling piezo elements used and the total cumulative voltage output. The task is to optimize the design in such a way as to obtain the optimal output voltage for a given mechanical excitation. The Piezoelectric Energy Generators (PEGs) have two domains—active and passive domains. The optimization process is divided into several steps, which significantly reduces the number of calculations. This paper is focused on the optimization process in the passive domain, that increases the output voltage for given mechanical excitation. In the optimization, the process can be developed for specific operating conditions, various lengths of duralumin base plate, the various position of proof mass, and different applied acceleration. It has been modeled and analyzed for axial-based piezoelectric generators. The maximum voltage and power are observed 11.64 V and 1355 µw at 633 Hz, respectively, when the length of the duralumin base plate is 150 mm and 5 m s−2 acceleration. The analysis of this study can guide the passive domain optimization of PEGs to meet desired purposes of energy harvesting.

Numerical Assessment of a BAY-Type Model for different Vortex Generator Shapes Applied on a Wind Turbine Airfoil

Modern wind turbines are increasingly equipped with vortex generators in the inner part of the rotor blade. On large blades it is usual to install hundreds of these small passive devices to delay flow separation. Therefore, affordable numerical methods to include vortex generators in the design process are required. One very promising method based on the addition of source terms in the flow equations is the BAY model. In this work a BAY-type model is presented and assessed for three different vortex generator shapes (rectangular, delta and cropped-delta) placed on a DU 97-W-300 airfoil and computed with steady-state Reynolds-averaged Navier-Stokes numerical methods. In order to quantify the circulation of the main streamwise vortex, a method to identify the vortex core based on the λ2-criterion is presented and shows good results. The computations reveal very good agreement with the experimental data for attached flow in terms of lift and pressure distribution while drag is inherently underestimated by the BAY model due to the inviscid modelling of the vortex generators. It is displayed that this underestimation is proportional to the vortex generator surface area. Concerning the different shapes, it is shown that the delta shape reveals larger deviations from the fully resolved case than the other geometries and therefore requires higher mesh resolution.

Optimal Control of an Inverter-based Virtual Synchronous Generator with Inertial Response

Renewable energy sources are gradually replacing conventional synchronous generators, which are responsible for supplying the power grid inertia damping properties. This paper proposes a nonlinear optimal controller for a renewable energy generation system based on a power electronics inverter, in order to incorporate the system inertia behavior through imitating the rotor inertia of synchronous generators. The main contributions of this paper are: 1) the modeling and synthesis of a nonlinear optimal control scheme for a power inverter such that it dynamically behaves as a conventional synchronous generator, where the active and reactive power are regulated, and provides robustness against utility grid disturbances; 2) the dynamical modeling of the virtual inertia-based inverter generator and its corresponding response to power reference variations and utility grid voltage disturbances. Further, an analysis procedure is presented to compute a predefined value of the inverter inertia constant, proportional to the one that a synchronous generator could provide, but taking into account the rated power of the generator. Simulation results assess the proposed methodology effectiveness