Synchronous Generator

This paper discusses the field tests of the wind turbine unit, in which the front and the rear wind rotors drive the inner and the outer armatures of the synchronous generator. The wind rotors were designed conveniently by the traditional procedure for the single wind rotor, ...

Classical Potier model is widely used to predict the behavior of isotropic synchronous machines in steady state conditions keeping into account the main effects of core saturation. Its parameters are usually determined using a popular traditional procedure, but the obtained model proved to appreciably lack accuracy in some machines at high loads. It also requires a short-circuit test, rather unpractical in large
machines. This paper proposes a generalization of such procedure, retaining its basic simplicity while allowing a much wider flexibility in the selection of test points. In fact, it uses 2 correlated null-power-factor tests, possibly carried out at the same voltage even with machine connected to the grid, avoiding the short-circuit test and permitting a more focused parametrization for operating range around the rated point.

This contribution deals with the analysis of synchronous generator loss of excitation (LOE) protection. This paper presents a new method for detecting LOE in synchronous generator based on the variation of the magnetic flux linkage in the air gap. To show the effectiveness of the proposed protection, comparisons
are made with the conventional LOE protection methods by considering different generator sizes. The simulation results show that the proposed method is useful and effective to detect LOE conditions. The main advantage of this method is its speed and sensitivity.

The Heffron-Phillips model of the synchronous generator is a fourth order linear model including a third order synchronous machine and a first order automatic voltage regulator (AVR) model. This model is used for small signal stability analysis and power system stabilizer (PSS) design. In some power grids, the synchronous generators and excitation system parameters are not available or valid because of derating, while these parameters are essential to analyze the power systems, design the controllers, and assess the security of the network. In this paper, a genetic algorithm-based method is proposed to identify the parameters of the synchronous generator and excitation system in the frame of Heffron-Phillips model using on-line measurements data. In the proposed method, the reference voltage of AVR is considered as the input signal, while the terminal voltage and output active power of the machine are considered as output signals. The output signals are provided by phasor measurement units (PMUs). The proposed method is applied to a single machine connected to an infinite bus, to show its effectiveness and accuracy.

Distributed Generation is increasing in nowadays power systems. Small scale systems such as photovoltaic, biomass or small cogeneration plants are connected to the distribution level, while large wind farms will be connected to the transmission level. Both trends lead to a replacement of large synchronous generators as the dominating generation technology. Up to now, transient stability of transmission systems has been analysed to a satisfactory degree of accuracy with a simplified representation of the distribution systems. In future, distributed generation will more and more influence the behaviour of the system. Stiff, inverter-based local generation technologies may improve the system stability; however, increasing electrical distances between large synchronous generators in operation will impede the system stability. These (and other) diverging effects have to be studied in detail. This overview paper summarises the latest findings and reveals future research questions. It is concluded that the accuracy and validity of the currently applied dynamic models for transient stability analysis of power systems with high penetration of DG should be further investigated.

Mathematical model of third and seventh order that describes the synchronous generator is given. Basic principle, application field and equivalent circuit of synchronous generator are explained. Simulation model of synchronous generator using Matlab is given. Model made in SimPowerSystems is explained. Essential parameters used for simulation are given. Usage of model for different testing and analysis is proposed.

PREMESSA Per studiarne le vibrazioni torsionali, gli alberi dei gruppi di produzione elettrica vengono di solito rappresentati con sistemi a parametri concentrati. Ciò può comportare significativi "errori di discretizzazione", in particolare nel calcolo delle frequenze proprie di oscillazione. In questo articolo viene proposto un metodo di calcolo che conserva il carattere distribuito dei parametri meccanici, consentendo di evitare gli errori di discretizzazione. Si utilizzano, a questo scopo, equazioni formalmente identiche a quelle che governano i circuiti elettrici a parametri distribuiti. La linea d'albero viene così rappresentata con un numero assai esiguo di doppi bipoli in cascata, ciascuno con una sua costante di propagazione ed una impedenza caratteristica. Tale sistema equivalente viene studiato in ambiente MATLAB. Il calcolo, che non richiede più di cinque secondi, fornisce l'ampiezza delle oscillazioni, sia nel dominio del tempo che in quello della frequenza. Il ricorso alla trasformazione secondo Fourier consente di studiare qualsiasi regime di funzionamento, sia permanente che transitorio. È possibile quindi simulare una classe assai ampia di eventi di esercizio: ad esempio, l'apertura improvvisa dell'interruttore di interfaccia, o le vibrazioni legate al possibile squilibrio nel sistema trifase di correnti statoriche. Un modello di calcolo a parametri distribuiti. Vibrazioni torsionali nei gruppi di produzione elettrica Giuseppe Dell'Olio, GSE Generalità I gruppi di produzione di energia elettrica sono spesso soggetti a vibrazioni torsionali sulla linea d'albero, le quali possono dar luogo a fatica nei materiali, a fluttuazioni di potenza e a danneggiamenti vari. Per evitare tali effetti indesiderati, è importante calcolare sin dalla fase di progetto le frequenze torsionali proprie dell'albero: si potrà così accertare che siano sufficientemente lontane dalle frequenze delle sollecitazioni che prevedibilmente si manifesteranno durante l'esercizio. I metodi di calcolo oggi disponibili per questo scopo si basano su modelli con elementi concentrati. I vari elementi (rappresentati dai rispettivi momenti di inerzia) sono disposti in serie tra loro: ciascuno è collegato al successivo per mezzo di una molla rotazionale, caratterizzata dalla propria rigidezza torsionale. Si tratta, come è facile comprendere, di modelli approssimati, che presentano significative limitazioni di impiego. La più importante è forse quella legata all'errore di discretizzazione. L'albero e gli elementi che vi sono calettati vengono idealmente suddivisi in tanti elementi spaziali, di ciascuno dei quali viene calcolato l'angolo di rotazione. Ogni elemento ha dimensioni piccole ma finite; si perde così il carattere "continuo" dell'intero sistema, a favore di una rappresentazione discreta. La precisione del calcolo ne risulta ridotta: particolarmente importante è l'errore che riguarda le frequenze proprie di oscillazione. Per mantenere gli errori entro limiti accettabili, è ENERGIA 8 Power Technology 01-02 2017 n. 97 indispensabile ridurre le dimensioni dei singoli elementi concentrati, aumentandone di conseguenza il numero complessivo. Evidente l'aggravio che da ciò deriva, quanto all'occupazione di memoria ed al tempo di calcolo necessario. Il metodo che qui proponiamo (lo indicheremo come il "metodo del doppio bipolo") considera l'albero e gli elementi ad esso solidali scomposti in strati cilindrici di spessore infinitesimo. Ne risulta un circuito a parametri distribuiti, il quale non è affetto da errore di discretizzazione. Di più: il calcolo viene limitato alle sole sezioni dell'albero delle quali interessa studiare la vibrazione, con enorme risparmio di risorse (memoria, tempo di calcolo). Immediata, poi, l'estensione del metodo a casi più complessi. Ad esempio, per studiare un sistema composto da più alberi che si diramano, si può applicare il metodo del doppio bipolo a ciascun albero singolarmente. Si collegheranno poi tra loro i vari doppi bipoli così ottenuti, fino a ridurli ad uno solo, equivalente a quelli.

Trading with reactive power will soon become a very important part of electric energy trade. However, while trading, voltage regulation in portable and distribution systems must not be neglected. In order to balance the technical and economic aspects it is necessary to be familiar with the electric power system, the source of electric energy most of all, meaning the synchronous generator and its possibilities. These possibilities are shown in the synchronous generator P-Q diagram. We nowadays use static P-Q diagrams, provided by generator producers, which in most cases refer only to generators. This article presents a dynamic user P-Q diagram containing changeable parameters and showing a real availability of a synchronous aggregate.

The paper briefly contains about the analysis of the synchronous generator. This contains the consideration of the actual parameters, state space model, consideration of the generator under the no damping conditions. This is a simulink based project to determine the performance of the generator. This also includes the design of the PID circuit for controlling the field winding excitation voltage.

Abstract:- The aim of this work is to analyze a typical configuration of a Wind Turbine Generator System (WTGS) equipped with a Variable Speed Generator. Nowadays, doubly-fed induction generators are being widely used on WTGS, although synchronous generators are being ...

Heffron -Phillips model of a synchronous machine is commonly used in small signal stability analysis and for off-line design of power system stabilisers. The data used to determine the parameters of this model are either hard to measure or require the machine to be taken off-line to take the measurements which, in general, is inconvenient. Identifying these parameters from online data measurements is important since it does not require any a priori knowledge of the machine data. The problem of closed-loop identification of the Heffron -Phillips model parameters is of practical importance since the data used for identification can be gathered when the machine is normally connected to the power system. The use of open-loop identification techniques using data gathered during closed-loop operation of synchronous generators leads to bias errors in the estimated parameters. Motivated by the fact that the synchronous machine model is multivariable and is well defined in a state space structure, a closed-loop subspace parameter identification technique is proposed. Consistency of the proposed approach is illustrated using Monte Carlo analysis. Comparison of the proposed method with open-loop identification technique shows the superiority of this approach.

In this paper, a methodology to estimate parameters of synchronous generator and its excitation system, based on the trajectory sensitivity technique, is proposed. Some alternatives are proposed for this technique regarding a future 'on-line' application.

This paper models and simulates a salient-pole synchronous generator using a modified winding function theory and more precise stator and rotor winding distribution with dynamic eccentricity between the stator and rotor. Air-gap permeance is also computed more accurately compared to currently available methods. Inductances with this method are compared to those obtained from other methods and it is shown that the results are closer to those obtained from finite element computations. Finally, the calculated inductances are used in a coupled electromagnetic model for simulation and studying the frequency spectrum of the stator line current in the presence of dynamic eccentricity.

Recently linear synchronous generator for the exploitation of sea wave energy has been proposed. That solution does not require reactive power to magnetize but needs permanent magnets to assure the excitation. The electrical energy generated by such a device must be converted and conditioned in order to match the instantaneous utility requirements and a power link from the sea to an interconnection is needed. In this paper in order to overcome that difficulty, the authors propose the use of the electrical energy generated to generate "in situ" hydrogen. As a result the output of the generation would be hydrogen that can be stored and used when needed The proposed electrical generator is a PM linear synchronous generator.

Brushless doubly fed iuduction machine has recently attracted attention in variable speed generators and motor drives. In order to have a high performance control, a precise dynamic model is required. This paper aims at introducing a model of brushless doubly fed induction machine taking core loss into account. The details of model derivation are outlined and the torque relation is expressed in the general reference frame. The model is then used for simulation of the dynamic performance of the machine. The error introduced by neglecting core loss effect is also shown.

Growing number of wind turbines is changing electricity generation profile all over the world. This brings challenges for power system operation, which was designed and developed around conventional power plants with directly coupled synchronous generators. In result, safety and stability of the electrical network with high wind energy penetration might be compromised. For this reason transmission system operators (TSO) impose more stringent connection requirements on the wind power plant (WPP) owners. On the other hand flexible AC transmission systems (FACTS) devices offer enhancement of grid stability and can facilitate grid code compliance for WPP.

Implementations of mini hydro schemes with conventional hydraulic, electrical equipment's and controllers have proven very expensive and uneconomical. Many developing countries that are in need of rural electrification have encountered economical problem when setting up these mini hydro schemes. To address this problem, alternative options and new designs of these equipment's have been explored by many researchers around the world. The application of these new designs would reduce the overall cost of mini hydro development and would help in making it a cost effective technology. These new designs will also help developing countries to provide electricity to rural areas or remote regions where interconnection of transmission line from the electrical grid is uneconomical. The new designs can also be an enabling factor in boosting up electricity generation using a renewable energy source. This paper provides survey of all these alternative options and new designs in the controller, hydraulic turbine and generators that have been implemented in different countries of the world.

New and simple explanations on two fields: 1) electric current and 2) light and colors. The explanations are based on many experiments, very simple and very easily reproducible ones, some of them, although simple, still very impressive and yet not known.

This paper shows, through simulations using the software Matlab/Simulink and its library Simpowersystems, how to perform the synchronous generator load rejection tests and how to obtain the values of the synchronous generator electrical operational parameters which are important data to perform generator and electrical power system dynamic studies. The paper discuss the d-axis load rejection test, the q-axis load rejection test, the arbitrary axis load rejection test also shows how to calculate the electrical fundamental parameters which characterizes the synchronous generator.

Due to their high efficiency and reliability, permanent magnet synchronous machines are widely used in low speed direct-driven applications. The present paper deals with the design and analysis of a special topology of a PMSG suited for small rating, direct-driven wind turbine. A preliminary design procedure is presented and the results are introduced in FEM based software in order to analyze the performances of the machine. The theoretical approach is validated thought experimental measurement and methods adopted to improve energy performance.

In the paper the full performance analysis of a salient poles synchronous generator (SPSG) is presented. The focus is put on the simulation of transient characteristics in the case of three-phase bolted short circuit at the generator terminals. The analysis is based on the combined solution of the magnetic field equations and the circuit equations of windings. The equations are elaborated by the finite element method (FEM) and the field solution is obtained by using of the time-stepping approach.

A method to estimate the dynamic parameters of the commonly used third-order d-q model of a synchronous generator, based on measured electrical power, reactive power, terminal voltage, field current, field voltage and rotor angle following a small perturbation of the field voltage, is described. The parameters are estimated from two newly developed nonlinear functions for electrical power and terminal voltage by using a nonlinear least squares (NLS) algorithm. Results of simulation studies and experimental data collected from an 80 MVA, 10.5 kV generator show the efficacy of the proposed method and also reveal that the proposed method is valid for a wide range of operating conditions. For cases where rotor angle is not available, a new method for rotor angle estimation is also proposed.

In this paper a regulation of the terminal voltage of synchronous generator (SG) has been developed. Here, the nonlinear model of the SG is used directly without requirement for a linearized mathematical model of the generator. A proportional integral PI-controller is used to adjust the duty cycle of the DC chopper of step-down type for controlling the field voltage and consequently the output voltage of the generator. Furthermore, Particle swarm optimization (PSO) algorithm is employed as an optimization technique for tuning the optimal parameters of the PI controller (Kp and Ki). This is achieved by the minimization of the quadratic output error between the reference voltage and the output voltage calculated from the adopted model at the same time. In order to test the performance of the PSO-PI controller, results are compared with the genetic algorithm (GA). Moreover, to reduce the overshoot resulting in the response of the terminal voltage, a varied reference voltage is adopted. Results obtained show the superiority of the varied reference voltage to decrease the overshoot versus the fixed reference voltage.

This paper deals with the control of a hybrid excitation synchronous generator which is used to supply an isolated grid for aircraft applications. This grid is supposed to be a 270-V dc bus. Thus, a rectifier is required between the machine and the dc bus. A diode rectifier is preferred here due to its great reliability and because it is also a low-cost solution. A controller is then proposed in order to regulate the output dc voltage of the generator. It is finally validated by simulations and experimental results.

A state-space representation of a synchronous generator is established and used to analyze the transient behavior of a synchronous generator. The machine is a 2 pole, 150 MVA, 120 MW, 13.8 kV, 50 Hz generator connected to an infinite bus through a transformer and a transmission line. The state-space representation is based on a two-axis equivalent-circuit model of the generator

Power demand increases continuously and it is not economical and reliable to fulfill the demand by thermal based generation methods. To overcome the problems of thermal based generation, use of non-conventional sources increases very rapidly. These sources are pollution free and economical but creating the problems while synchronization with synchronous generator. Compensating devices like STATCOM are suggested for the issue of stability and synchronization. This paper deals with the combine working by simulation method of oil based synchronous generator and induction generator based micro hydro plant located at remote places. The main objectives of this paper are to control voltage and frequency for variable load. The Simulink model is developed to perform the transient analysis of the proposed scheme.

When a small generator is connected to the distribution system, the voltage at the point of interconnection is determined largely by the system and not the generator. This report examines the effect on the generator, on the load voltage and on the distribution system of a number of different voltage control strategies in the generator. Synchronous generators with three kinds of exciter control are considered, as well as induction generators and do/ac inverters, with and without capacitor compensation. The effect of varying input power during operation (which may be experienced by generators based on renewable resources) is explored. as well as the effect of connecting and disconnecting the generator at ten percent of its rated power.

Abstract—This work shows a method to quantify rotor eccentricities in synchronous machines by exploiting the unbalance caused in the split-phase currents. The paper first develops a machine model comprehensive of eccentricities and parallel circuits in the stator, by using symmetrical components. Then, the model is used for formal calculation of the unbalanced currents. Finally, the equations are reversed to obtain eccentricity degrees from current measurements. Practical formulas are given for fault assessment, only requiring machine line voltage and synchronous reactance. The method can be applied on load. This paper provides full details of the theory underlying the method. The theory also clarifies some aspects about split-phase currents, not deepened before. It is proven that the air gap flux modulation due to eccentricities, acting through additional 2(p±1)-pole flux waves in 2p-pole machines, stimulates additional currents which circulate in the stator and turn into 2(p±1)-pole rotating space-vectors in the complex domain. Vector trajectories have shape and amplitude dictated by eccentricity type and degree, respectively. This study is limited to 2p-pole machines with p≥2. The theory is corroborated by simulations of a practical 1950kVA generator in this Part I. Experimental proofs and simulations of a laboratory 17kVA machine are provided in Part II of the paper.

This paper considers the problem of oscillations in a synchronous generator connected to infinite bus through transmission lines. Two on-line control techniques, namely, artificial neural networks (ANN) and simulated annealing (SA) are utilized to cancel the oscillations in synchronous generators (SG). Simulation results of applying external disturbances to the synchronous generator controlled by the proposed simulated annealing controllers are compared to results obtained by using neural network controllers. These control schemes contribute to preventing system instability by suppressing the low-frequency oscillations arising from power grid fault disturbances. The proposed on-line SA and NN integrate a voltage regulator and a power system stabilizer to obtain near-optimal solutions of the problem through utilizing functions evaluation. They can be adopted to replace the conventional automatic voltage regulator (AVR) with power system stabilizer (PSS) of the generator. Simulation results show that algorithms can efficiently and effectively solve such optimization problems within short time. In addition, they are presented to demonstrate the effectiveness and advantage of the control system of synchronous generator (SG) in comparison with the conventional control scheme so as to allow the generator to operate closely to its steady state stability limits.

This paper investigates the cost-effective ranges of gearbox ratios and power ratings of multibrid permanent-magnet (PM) wind generator systems by using a design optimization method. First, the analytical model of a multibrid wind turbine concept consisting of a single-stage gearbox and a three-phase radial-flux PM synchronous generator with a back-to-back power converter is presented. The design optimization is adopted with a genetic algorithm for minimizing generator system cost. To demonstrate the effectiveness of the developed electromagnetic design model, the optimization results of a 500-kW direct-drive PM generator and a 1.5-MW multibrid PM generator with various gear ratios are, respectively, compared with those from other methods. Then, the optimal design approach is further employed for a range from 750 kW up to 10 MW. The optimization results of PM generator systems including direct-drive and multibrid wind turbine configurations are obtained, and the suitable ranges of gear ratios for different power ratings are investigated. Finally, the detailed comparisons of the most cost-effective multibrid PM generator system and the optimized direct-drive PM generator system are also presented and discussed. The comparative results have shown that the multibrid wind turbine concept appears more cost-effective than the direct-drive concept. the author or coauthor of more than 100 papers. His current research interests include design aspects of electrical machines for renewable energy and mechatronic applications.

Virtual laboratories can become important components of the teaching process, because using them several experiment-oriented problems can be solved easily and also from the distance. Graduates using virtual laboratories will be better trained when they enter the job market. In the paper a laboratory work will be presented having two components: a simulation and an experimental module. Both can be used for the preparation of a real lab and for accessing the real-world experiments. The virtual lab modules can also allow multiple students to remote access the experiments, the multicast data transfer mechanisms and arbitration mechanisms.

The Heffron-Phillips model of a synchronous machine has successfully been used for investigating the low frequency oscillations and designing power system stabilisers. The parameters of the model are usually calculated using the synchronous generator parameters and some system variables at steady-state conditions. As the parameters of synchronous generators are not easily measurable or accurately available and steady-state calculations may have some errors, the identification of such parameters using online measurements is investigated by the authors. A generating unit is a multivariable system and is well defined in a state space structure. The subspace state space (4SID) identification method is very suitable for the identification of such a system. This method is used to identify the parameters. Since the synchronous generators are nonlinear, the parameters of the identified Heffron-Phillips model would depend on the operating conditions. To follow such changes, a look-up table model is developed. The proposed method is first applied on a simulated nonlinear model of a synchronous generator with saturation effect and then it is applied on a micro-machine system. Simulation and experimental results show the good accuracy of the identified models.

The main task in this paper is to present a performance analysis of a distribution network in the presence of two synchronous generators in parallel, with its speed and voltage regulators modeled with TACS-Transient Analysis of Control Systems, for distributed generation studies. This type of configuration is common in systems where renewable fuels are used as sugar cane bagasse or straw. Must be highlighted that this generators is driven by a steam turbine, and the whole system with regulators and the equivalent of the power authority system in the point of connection (PAC) are modeled in the "ATP-Alternative Transients Program". Technical questions studied here refer to steady-state voltage profile, voltage stability, voltage dip due to a balanced three-phase fault, load rejection, distribution line outage and the behavior of machine regulators facing the aforementioned contingencies. Results show that, in some cases, the independent power producer (IP) can be a menace to the physical integrity of the system and in other cases can be very beneficial to the distribution system in the point of connection.

Hybrid excitation synchronous machines (HESMs), which combine the best features of traditional electrically excited synchronous machines (SMs) and permanent magnet synchronous machines (PMSMs), are investigated. Such machines provide energy efficiency benefits over traditional field-winding-excited machines, especially in the lower power region upto a few megawatts. This paper studies the applicability of a hybrid excitation synchronous generator (HESG) to a marine diesel genset. Three HESG structures are proposed, and their performance in island operation are studied by the two-dimensional (2D) finite-element analysis. Comparison of the proposed constructions is performed.