Excitation Capacitance Research Articles

Dynamic Analysis of a Novel Single-Phase Induction Generator Using an Improved Machine Model

The dynamic analysis using an improved transient model of a recently introduced single-phase induction generator suitable for renewable energy conversion is presented in this paper. In this three-phase cage type induction machine based generator topology, one of the three windings is used as the control winding for real and reactive power control and the other two windings are connected in series to form the output winding. Due to larger percentage errors resulting from existing models in comparison to the experimental values, transient model of the generator is improved to take into account the core loss resistance and the nonlinearity of magnetizing reactance in the saturated region. The generator system is simulated in Matlab software to present a numerical comparison of the simulation results obtained from improved and existing models. The transient behavior of the generator is comprehensively studied by considering sudden variations in rotor speed, excitation control voltage, capacitance and load. The simulation results are verified by experiments performed on a laboratory experimental setup.

Experimental Performance Evaluation of a Power Generation System Using SEIG

One of the working induction generators is the self-excited induction generator (SEIG). In the self-excited mode, the generator can produce its voltage and frequency and for this it requires a capacitor. Determination of exciting capacitance of the induction generator (IG) is very important in adjusting the capacitance size. The effect of varying the capacitance of this capacitor on the generated output power, voltage, and its frequency has been studied. Besides, these three factors also differ inside by the value of the capacitor, the speed of the generator, the size and the change of the load, and the parameters of the generator. For this purpose, an experimental system, which consists of an AC driver, an induction motor, an induction generator, a step-down transformer, an AC/DC converter, and a controller, was installed. Various loading and excitation capacitor configurations of the IG were also examined at load and no-load. Thus, the experimental analysis of the powers gathered from the output of the generator has been achieved.DOI: http://dx.doi.org/10.5755/j01.eie.23.1.13069

Performance Characteristics of Six-Phase Induction Generator for Renewable Power Generation

<p>This paper presents the performance behavior of a multi-phase induction generator operating in six-phase mode. An experimental analysis has been done to determine operating characteristics of the six-phase machine to illustrate the advantageous features of the machine as compared to its three phase counterpart. The machine is configured to operate as a standalone power source in conjunction with a DC prime mover. The multi-phase machine can operate with one three phase capacitor bank which does not lead to complete shutdown of the system during fault conditions across one of its two sets of its stator windings. In the analysis the machine is connected to different capacitor configuration and the influence of these connections on the machine performance during no load and load have been implemented. Experimental results include voltage build up of the machine with different excitation capacitors at both sets of stator windings with changing speed during no load condition, resistive load condition and resistive inductive load condition with simple shunt and short shunt configuration.</p>

Modeling, implementation and analysis of a high (six) phase self excited induction generator

Dual d-q model of six phase-self excited induction generator (6Ph-SEIG) developed in stationary reference frame is proposed in this paper. Developed model, implemented in terms of a simulation model, is utilized to evaluate no-load and on-load characteristics along with the estimation of dynamic parameters of studied 6Ph-SEIG for each working condition. Simulation results are verified on the implemented 6Ph-SEIG test-rig with high accuracy. Inherent loading limit of 6Ph-SEIG is obtained as 68% of the rated capacity with the evaluated optimum excitation capacitance of 4μF per phase. The reactive power of SEIG varies from 4400 var to 600 var from no-load to maximum load of 1377W with a corresponding change in magnetizing current from 4A to 0.64A.

Optimal capacitance selection for a wind-driven self-excited reluctance generator under varying wind speed and load conditions

This paper presents a methodology to determine and select a suitable excitation capacitance value for a wind-driven self-excited reluctance generator (WDSERG), which would produce a constant output voltage under changing wind speed and connected load. A steady state mathematical model of WDSERG is developed from the dynamic model of self-excited reluctance generator (SERG) and phasor diagram. This model is used to develop an algorithm that searches for the optimum excitation capacitance which produces a desired output voltage level for any given wind speed and load within the operating limits of the WDSERG. Different scenarios of variable speed, load and power factor are considered and an optimal capacitance value is determined and selected for each cases. Published experimental data was utilised to validate the developed model. The results show that there is a distinct capacitance value that would produce a constant output voltage under any given operating conditions of wind speed and terminal load. The procedure presented can form a basis for the design of a variable excitation capacitor to maintain a constant output voltage under varying wind speed and load, which will invariably offer an effective and low-cost solution for output voltage control of WDSERG.

Assessment of excitation capacitance for a multiphase isolated self-excited induction generator for power generation

Self-excited induction generators are used in remote places for electrical power generation from both conventional as well as non-conventional sources. An induction generator can operate as a capacitor-excited machine, provided the machine is driven beyond synchronous speed and a suitable capacitor is connected across its terminals. In this paper, a technique has been proposed to estimate the values of excitation capacitances to maintain desired terminal voltages in a multiphase induction generator. A mathematical model using nodal admittance technique of a six-phase induction generator has been analysed. Genetic algorithm technique is applied here to obtain the unknown parameters and the capacitance requirements to obtain desired terminal voltages under various operating conditions.

Assessment of excitation capacitance for a multiphase isolated self-excited induction generator for power generation

Self-excited induction generators are used in remote places for electrical power generation from both conventional as well as non-conventional sources. An induction generator can operate as a capacitor-excited machine, provided the machine is driven beyond synchronous speed and a suitable capacitor is connected across its terminals. In this paper, a technique has been proposed to estimate the values of excitation capacitances to maintain desired terminal voltages in a multiphase induction generator. A mathematical model using nodal admittance technique of a six-phase induction generator has been analysed. Genetic algorithm technique is applied here to obtain the unknown parameters and the capacitance requirements to obtain desired terminal voltages under various operating conditions.

DC Bus Voltage Control of a Power Generation System Based on a Dual Star Induction Generator

The main objective of this paper is the study and the evaluation a squirrel-cage Dual Star Induction Generator (DSIG) performances. This generator can be used in energy production at variable speed for high-power wind or hydro turbines. The studied system consists of a DSIG feeding a static load through two voltage source inverters connected in parallel on the same DC bus. A DC motor is used to ensure the generator drive at variable speed. This scheme is chosen to avoid the generated voltage amplitude and frequency variations, which occurs in case of self-excited induction machine and depends on the rotating speed and the size of the excitation capacitors. Thus, Modeling of DSIG, in the synchronous reference frame, and different parts of generation system are given. Then control strategy development is detailed. To ensure DSIG excitation and DC bus regulation under variable speed and at different loads, a control strategy based on active and reactive power control principle is used. Finally, power generation system performances are validated by simulation and confirmed by a set of experiments, carried out on an experimental test bench composed DSIG driven by DC motor. Simulation and experimental results show that the DC bus voltage is well regulated under different mode operating.

STUDY OF INDUCTION GENERATORS PERFORMANCE OF TWO-SPEED USED IN STANDALONE WIND TURBINES

Recent interest in renewable energy sources is growing as a resource substitute for conventional energy and this led to increased interest in electric power can be obtained from the wind energy.With the rapid development in electrical generators used in wind turbines, induction generators have proven quality among the different types of electric generators used in this field.Based on that research aims to study the behavior of squirrel cage induction generator(two-speed) when linked with a wind turbine and study of using feasibility in this field.To achieve this purpose theoretical and practical study for induction generator two- speed were completed.Theoretical study contains a review of principles of operation of the machine , circuit equivalent and math equations, but practical study has been fulfilled on a laboratory model for two-speed induction generator driven by DC motor with variable speed .This study has been fulfilled when induction generator operates on both of speed and set speed at which it move from working as a motor to work as a generator for different values ​​of the excitation capacitors, and relationship between voltage of generator and speed is identified at different degrees of excitation.

Voltage regulation approach to a self-excited induction generator: Theoretical study and experimental validation

Summary This article describes an accurate steady-state analysis of a stand-alone 3-phase self-excited induction generator (SEIG). This analysis, based on the Newton-Raphson algorithm, has shown that the system performance is greatly affected by the parameters related to the availability of primary energy, load variations, and excitation capacitor values. These parameters explain the stator voltage fluctuations and the output frequency decrease. To avoid any interruption of the excitation process and to ensure a good quality of the stand-alone minigrid, a three-phase voltage regulator (TPVR), based on switched capacitors, is proposed to keep the terminal SEIG voltage constant. The control algorithm and the regulation process are implemented using a microcontroller. The SEIG-TPVR is experimentally developed, and a variable capacitor bank is constructed. The experimental investigations on a 1.5-kW induction machine confirm the efficiency of the whole suggested system.

Analysis of wind driven self-excited induction generator supplying isolated DC loads

This paper presents the analysis, modelling and simulation of wind-driven self-excited induction generator (SEIG). The three-phase SEIG is driven by a variable-speed prime mover to represent a wind turbine. Also, the paper investigates the dynamic performance of the SEIG during start-up, increasing or decreasing the load or rotor speed. The value of the excitation capacitance required for the SEIG is calculated to give suitable saturation level to assure self-excitation and to avoid heavy saturation levels. Matching of the maximum power available from the wind turbine is performed through varying the load value. The effect of AC–DC power conversion on the generator is investigated. The system simulation is carried out using MATLAB/SIMULINK toolbox program.

Voltage Control of Single-Phase Two Winding Self Excited Induction Generator Using SVC-MERS for Isolated System

Single-phase induction generator is very suitable to be used in the typical loads which only need a single-phase power supply with small power capacity requirement, such as diesel engine, picohydro or small wind plant. It has some advantages such as rugged, effective cost, maintenance free and require no external excitation. However, it has inductive characteristic which makes poor voltage regulation. This paper proposed a shunt reactive compensator called SVC-MERS which can provide a variable reactive power to maintain the generator voltage despite of load variations. The experiment was conducted on single-phase two winding induction generator coupled by a three-phase induction motor which serves as the prime mover. SVC-MERS and the load are connected in shunt to the main winding, while the excitation capacitor was connected to the auxiliary winding. The experimental results showed that SVC-MERS can improve voltage regulation and substantially enhanced steady state loading limit.

Grid-Connected Dual Stator-Winding Induction Generator Wind Power System for Wide Wind Speed Ranges

This paper presents a grid-connected dual stator-winding induction generator (DWIG) wind power system suitable for wide wind speed ranges. The parallel connection via a unidirectional diode between dc buses of both stator-winding sides is employed in this DWIG system, which can output a high dc voltage over wide wind speed ranges. Grid-connected inverters (GCIs) do not require booster converters; hence, the efficiency of wind energy utilization increases, and the hardware topology and control strategy of GCIs are simplified. In view of the particularities of the parallel topology and the adopted generator control strategy, we propose a novel excitation–capacitor optimization solution to reduce the volume and weight of the static excitation controller. When this excitation–capacitor optimization is carried out, the maximum power tracking problem is also considered. All the problems are resolved with the combined control of the DWIG and GCI. Experimental results on the platform of a 37 kW/600 V prototype show that the proposed DWIG wind power system can output a constant dc voltage over wide rotor speed ranges for grid-connected operations and that the proposed excitation optimization scheme is effective.

A Comprehensive Analysis of Optimal Performance Parameters of Stand-Alone Generator

Background/Objectives: This paper aims to evaluate performance characteristics of standalone Self-Excited Induction Generator (SEIG) under varying load condition. Methods/Statistical Analysis: Prime mover speed, excitation capacitance and load significantly influence the performance of SEIG. Due to nonlinear magnetization, estimation of nonlinear magnetic characteristics involves clumsy mathematical computation. It gives an opportunity to model nonlinear magnetization characteristics suitable to obtain minimum impedance and optimal capacitance for improved performance. Findings: The effect of regression on nonlinear magnetization curve has been discussed while estimation of magnetization reactance by employing regression functions. It provides optimal value of magnetization reactance to compute performance variables of SEIG. Solution techniques are applied to calculate frequency and excitation capacitance and compared their results. Regression functions with solution techniques have been applied on comprehensive data of induction machines to exhibit validity and accuracy of proposed scheme. Applications/Improvements: The proposed techniques reveal lower capacitance requirement as compared to existing piece- wise linearization model.

Analysis of performance parameters and estimation of optimum capacitance for asynchronous generator

This paper presents a comprehensive analysis of performance characteristics under varying load condition for asynchronous generator. Performance of asynchronous generator depends on variation in prime mover speed, excitation capacitance and load. Estimation of magnetic characteristics involve complicated mathematical computation due to nonlinear nature of magnetization curve. It provides an opportunity to model nonlinear magnetization characteristics to get optimum impedance and optimal capacitance for better performance of asynchronous generator. The nonlinearity of magnetization curve has been analyzed by employing regression functions to estimate magnetization reactance. Thus, optimal value of magnetization reactance is obtained to calculate performance variables of asynchronous generator. Proposed technique provide optimal values of performance variables of asynchronous generator as compared to conventional piecewise linearization model. The effect of solution technique has been discussed while calculating performance variables of asynchronous generator at optimal value of magnetization reactance. Proposed technique of regression function and solution technique is applied on comprehensive data of induction machines as asynchronous generator to prove its validity and accuracy.

Estimation of Excitation Capacitance Requirement of an Isolated Multi-phase Induction Generator for Power Generation

<table width="593" border="1" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" width="387"><p>Self Excited induction generators are used in remote places for electrical power generation from both conventional as well as non-conventional sources. An Induction generator can operate as a capacitor excited machine provided the machine is driven beyond synchronous speed and a suitable capacitor is connected across its terminals. In this paper a technique has been proposed to estimate the values of excitation capacitances to maintain desired terminal voltages in a multi-phase induction generator. A mathematical model using nodal admittance technique of a six-phase induction generator has been analyzed. Genetic algorithm technique is applied here to obtain the unknown parameters and the capacitance requirements to obtain desired terminal voltages under various operating conditions.</p></td></tr></tbody></table>

Voltage and frequency regulation of standalone self‐excited induction generator for micro‐hydro power generation using discrete‐time adaptive control

This study deals with the development of a control system for voltage and frequency regulation of a micro hydro power generation system, fed by self-excited induction generator (IG). The generation system considers a four-wire three-phase grid, composed by three phases plus neutral conductor, fed by three-phase three-wires IG. The neutral conductor is created from the neutral point of star connection of excitation capacitors bank. The four-wire configuration allows the connection of three-phase loads in star or delta configuration, as well as single-phase loads. The voltage regulation is performed through a four-legs distribution static synchronous compensator (DSTATCOM) shunt connected to the AC bus. It is considered the employment of adaptive control techniques and the compensation of load current unbalances, which offers suitable voltage regulation in conditions of system's parameters variations such as load connection and disconnection, and changes in IG's unmodelled parameters, and voltage unbalance compensation, respectively. Frequency regulation is obtained by electronic load control connected to the DC bus of DSTATCOM. Experimental results were obtained to demonstrate the good performance of the voltage and frequency regulation control system during loads transient, including three-phase and single-phase loads.

Steady State Analysis Operation of Self-Excited Wound Rotor Induction Generator Under Constant Frequency and Tolerated Output Voltage

Self-excited induction generators (SEIG) are found to be most suitable candidate for wind energy conversion application required at remote windy locations. The major drawbacks of these generators are the poor voltage and frequency control under load and prime mover speed perturbations. In this paper, an attempt has been made to optimize the control strategy under various load and prime mover conditions, of the self-excited wound rotor induction generator (SEWRIG). By tolerating a slight deviation of the output voltage and ensuring a constant frequency with an adequate external rotor resistance, only four values of excitation capacitor are required for the whole range of operation. The effectiveness of the adopted strategy has been confirmed by comparing on a 0.8-[Formula: see text]kW wound rotor induction generator the simulated results to the corresponding obtained with an experimental test. A close agreement between the computed and experimental results confirms the efficiency of the adopted method.

Experimental Analysis of Harmonic Distortion in Isolated Induction Generators

The use of induction generator, replacing the continuous and synchronous generators, has proved to be an interesting solution for the supply of electricity in remote areas where the supply through a distribution network is not economically viable. In some cases the use of this machine type is appropriate in these areas, with the same associated with non-conventional systems of electricity, such as wind and hydro generation small. In these isolated systems is common to use cage induction generators with excitation capacitors, known as self excited induction generators. Allied to this, there has been an increase in the number of non-linear loads, at all levels of electricity consumption. Thus, it becomes necessary to study experimentally the harmonic distortion of voltage and current in this type of generator, which can supply non-linear loads that may be present in these remote areas.

A Single-Sensor-Based MPPT Controller for Wind-Driven Induction Generators Supplying DC Microgrid

In this paper, a simple method of tracking the maximum power (MP) available in the wind energy conversion system (WECS) for dc microgrid application is proposed. A three-phase diode bridge rectifier along with a dc–dc converter has been employed between the terminals of a wind-driven induction generator and dc microgrid. Induction generator is being operated in self-excited mode with excitation capacitor at stator. The output current of the dc–dc converter, i.e., dc-grid current is considered as a control variable to track the MP in the proposed WECS. Thus, the proposed algorithm for maximum power point tracking (MPPT) is independent of the machine and wind-turbine parameters. This algorithm has been implemented using dsPIC30F4011 controller. Furthermore, a method has been developed for determining the duty ratio of the dc–dc converter for operating the proposed system in MPPT condition using wind-turbine characteristics, steady-state equivalent circuit of a induction generator, and power balance in power converters. Circuit simplicity and simple control algorithm are the major advantages of the proposed configuration for supplying power to the dc microgrid from the proposed small-scale WECS. The successful working of the proposed algorithm for MPPT has been demonstrated with extensive experimental results along with the simulated values.