Three-phase Self-excited Induction Generator Research Articles

Efficient voltage regulation scheme for three‐phase self‐excited induction generator feeding single‐phase load in remote locations

This study presents analysis, design and implementation of a microcontroller based electronic load controller (ELC) for efficient voltage regulation of a three-phase self-excited induction generator (SEIG) feeding single-phase loads in remote locations. The proposed ELC has an uncontrolled rectifier, a filtering capacitor, an insulated gate bipolar transistor switch and a series dump load. The pulse-width modulation (PWM) pulses with appropriate duty cycle are generated using the dsPIC30F6010 microcontroller. The duty ratio is determined based on the closed-loop control scheme which decides the amount of power diverted to the dump load. The proposed SEIG–ELC system demonstrates an effective power switching between the main load and the dump load thereby providing an efficient voltage regulation at the machine terminals. The controller is modelled in Matlab/Simulink and the simulated results are validated by experimental results.

Steady State Analysis of an Isolated Self-Excited Dual Three-Phase Induction Generator for Renewable Energy

In this paper modelling and analysis in autonomous mode of dual three-phase induction generator (DTPIG) with a new algorithm have been done. We develop the steady state model of a dual three-phase self-excited induction generator for stand-alone renewable generation dispensing with the segregating real and imaginary components of the complex impedance of the induction generator. The obtained admittance yields the adequate magnetizing reactance and the frequency. These two key parameters are then used to compute the self-excitation process requirements in terms of the prime mover speed, the capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. Steady state performances and characteristics of different configurations are clearly examined and compared. The analytical results are found to be in good agreement with experimental results.

Design and Implementation of a Prototype Underwater Turbine Generator System for Renewable Microhydro Power Energy

This paper presents the installation and field measurements of a prototype microhydro power (MHP) generation system based on an underwater turbine generator. The studied MHP system employs the energy of flowing water in the agricultural irrigation of one of the irrigation ditches of the Yunlin Farmland Irrigation Association, Taiwan. The irrigation ditches are basically used for distributing irrigation water to different farmlands. To design the prototype, the MHP unit has to meet practical conditions of the selected ditch such as depth, width, water flow rate, total days of water flowing in a year, etc. The designed MHP unit consists of an underwater turbine, a gearbox, a three-phase self-excited induction generator with a switchable excitation capacitor bank, a three-phase diode bridge rectifier, a dc-to-dc buck converter, and a dc-to-ac inverter. A monitoring and control system based on an embedded system is also designed to measure the electrical data of the MHP unit.

Optimum utilisation of self‐excited induction generator

The voltage and frequency of three-phase self-excited induction generator (SEIG) depend upon various factors such as prime mover speed, capacitance value, load etc. The poor voltage and frequency regulation are the main constraints for poor performance of SEIG. The improved performance can be achieved through short shunt SEIG configuration. In this study, the utilisation of SEIG is transformed into a number of novel functions. The combination of speed, series and shunt capacitances as design parameters are selected for short shunt SEIG in order to provide optimum values for voltage regulation (VR), frequency regulation (FR), loadability, voltage/frequency regulation and to provide optimum performance, defined as a weighted combination of VR, FR and loadability. The effect of weights, speed and power factor on designed parameters is also assessed for a generic application on SEIG. Correspondingly, an optimisation is proposed using particle swarm optimisation, a heuristic approach considering various equality and inequality constraints related to SEIG. This study is carried out for resistive and inductive loads. The simulated results are validated with test results.

D.C. Motor-Based Wind Turbine Emulator Using LabVIEW for Wind Energy Conversion System Laboratory Setup

This paper describes the development and implementation of a wind turbine emulator (WTE), based on a d.c. motor, using LabVIEW. The emulator imitates both static and dynamic characteristics of a typical wind turbine (WT) of a wind energy conversion system (WECS). The setup can be used for development and testing of real-time control algorithms. The laboratory setup consists of a d.c. motor coupled to a three-phase self-excited induction generator (SEIG). The mathematical model of WT, designed in LabVIEW, is interfaced with the d.c. motor control circuit by the compact real-time I/O module (cRIO). The armature current is regulated by armature voltage control with appropriate switching signals for a power MOSFET-based control circuit. The simulation and experimental results under different scenarios prove the effectiveness of this LabVIEW-based WTE. This WTE can be effectively used as a laboratory-based teaching tool for electrical engineering students. The learning objective of this simple yet efficient laboratory setup is to study the WT characteristics in the absence of a real WT. A manual and a list of questions have been prepared related to the experiment and have been used at the Indian Institute of Technology Kharagpur (India). The learning performances of the students have been evaluated based on a questionnaire.

Operating performance of static series compensated three-phase self-excited induction generator

The performance of three-phase self-excited induction generator (SEIG) is investigated with static synchronous series compensator (SSSC) and static compensator (STATCOM) to feed static and dynamic loads. The employed compensators are three-phase, Insulated Gate Bipolar Transistor (IGBT) based, Pulse Width Modulation (PWM) operated, Current-Control Voltage Source Converter (CC-VSC). The proposed control techniques employ proportional-integral (PI) controller to generate the reference current. With the designed parameters and control, the SSSC is found effective to regulate load voltage during sudden change of the loads. The SSSC also provides stable operation with dynamic induction motor load and mitigates the unstable and oscillating behavior that is resulting during the operation of compensated SEIG with dynamic motor load. The presented results prove that both SEIG–SSSC and SEIG–STATCOM systems provide satisfactory performance.

Performance analysis of a new configuration of three-phase self-excited induction generator feeding a single-phase load

This paper presents a steady-state performance analysis for a new configuration of self-regulated self-excited three-phase squirrel cage induction generator feeding single phase loads. The proposed scheme provides the required reactive power for excitation, small voltage regulation, acceptable phase balance and large output power. Using an equivalent circuit model incorporated with the method of symmetrical components, the total impedance equation of the generator’s model is derived. This non-linear equation is minimised to obtain the operating frequency and magnetising reactance. Based on the derived circuit model, the performance of the generator under different operating conditions is predicted. To confirm the validity of the proposed scheme, simulation results are compared with their corresponding test results.

Wind-Driven SEIGs for Supplying Isolated Loads Employing DSP Based Power Electronic Controllers

A DSP based closed-loop system has been developed for wind-driven three-phase Self-Excited Induction Generators (SEIGs) using a diode bridge rectifier (DBR) followed by an IGBT inverter. This system is meant for supplying isolated ac loads with a voltage of constant magnitude and frequency, for any operating condition of varying nature of wind speed and consumer load. The configuration and implementation of this proposed system have been fully described. The detailed method of analysing and predetermining the performance characteristics of such stand-alone systems has also been explained. Test results obtained on an SEIG operated with the controller built in the laboratory, demonstrate the successful working of both the hardware and software of the control scheme and the usefulness of the set-up as a whole for supplying isolated ac loads. With the varying nature of wind speed, a method of meeting the power balance between the wind power available and the load power requirement has also been explained with extensive Simulation studies.

Steady-State Analysis of Parallel-Operated Self-Excited Induction Generators Supplying an Unbalanced Load

Steady-State Analysis of Parallel-Operated Self-Excited Induction Generators Supplying an Unbalanced LoadThis paper proposed a multi-objective genetic algorithm (MOGA) based approach for determining the steady-state performance characteristics of three-phase self-excited induction generators (SEIGs) operating in parallel and supplying an unbalanced load. The symmetrical component theory is used for the transformation of a complex three-phase generators-capacitances-load system to a simple equivalent circuit. The MOGA has been employed for the determination of unknown variables by minimizing the impedance module of the equivalent circuit. Using this approach, effects of various parameters on the terminal voltage control characteristics are examined for two parallel SEIGs with C2C connection under a single phase load.

Analysis and control of self-excited induction generator-converter systems for battery charging applications

A method has been developed for the analysis of operation of self-excited induction generators (SEIGs) supplying battery charging loads through three-phase semi-converters by representing the battery circuit as equivalent resistance and reactance in the equivalent circuit of these generators. Such equivalent values are functions of the dc charging voltage and current and the control angle set in the converter. The solution for this circuit has been carried out using the genetic algorithm technique instead of using higher-order polynomials for the loop or nodal equations of the circuit. Apart from the conventional phase angle control, other firing control schemes namely negative firing angle control, extinction angle control and symmetrical angle control have been considered for the operation of the converter. The relative performance of these control schemes, for the various modes of operation of SEIG-converter systems such as constant and variable speed, has been brought out. Experimental results obtained on a three-phase SEIG charging suitable batteries through an IGBT-based semi-converter, controlled with all these schemes, confirm the usefulness of the proposed system and the validity of its analysis.

Analysis and Investigation of Skew Effect on Behavior and Performance of a Small Scale Three-Phase Self-Excited Induction Generator

This paper presents analysis and investigation of the skew effect on behavior and performance of a three-phase, 220/380V, 8.7/5.0A, Δ/Y connected, 4 poles, 2.2kW self-excited induction generator (SEIG) with different angles rotor skewing. A 2D finite element analysis (2D-FEA) is used to consider core loss, flux density and circuit parameters. Analysis of excitation capacitor values for the SEIG based on a steady-state equivalent circuit model including rotor skew effect is given. Skewed rotor slots with angle of 0° (non-skew), 5° and 10° for the SEIGs are employed. Testing and performance comparisons under steady-state operation with a pure resistive load have been conducted. Obtained results can be guidelines and recommendations for development of effective wind induction generators.

Transient Performance of Series-Compensated Three-Phase Self-Excited Induction Generator Feeding Dynamic Loads

This paper presents the transient performance of a series-compensated three-phase self-excited induction generator (SEIG) feeding a dynamic load such as a three-phase squirrel-cage induction motor (IM). Mathematical modeling and simulation study of SEIG and an induction motor (SEIG-IM) combination is carried out using MATLAB/Simulink. An exhaustive experimental study is conducted using a Mawdsley's generalized machine operating as a SEIG and a three-phase squirrel-cage IM as the dynamic load. The simulated results are compared with the experimental results under various operating conditions of the SEIG such as the following: 1) its voltage and current buildup at no-load; 2) switching of a three-phase squirrel-cage IM to the SEIG terminals without series-compensating capacitors (resulting failure to start an IM); and 3) switching on the same motor with the series capacitors (resulting in successful starting of the IM). A sudden switching of the IM as a dynamic load on the SEIG without the series compensation causes severe transients in electrical and mechanical variables of the SEIG and due to large starting current requirement of the IM, there is a collapse of the terminal voltage of SEIG. However, the use of series compensation in short-shunt configuration of SEIG results in the successful starting of the IM with an improved voltage regulation of SEIG. The phenomenon of subsynchronous resonance (SSR) is observed due to the large variations in the impedance of the SEIG-IM combination and the presence of series capacitors. It causes low frequency oscillations in the IM stator voltages, currents, and its speed. The SSR phenomenon restricts the IM to attain the rated speed. A detailed study of the SEIG-IM system is made to select proper combination of shunt and series capacitors to avoid the SSR phenomenon.

A New Method for Voltage and Frequency Control of Stand-alone Self-excited Induction Generator Using Pulse Width Modulation Converter with Variable DC-link Voltage

Three-phase self-excited induction generators play an important role in renewable energy sources such as wind and hydraulic energy. Their main disadvantage is poor voltage and frequency regulation under varying load and speed. This article introduces a new and simple method for voltage and frequency control of three-phase unregulated speed induction generators in the islanding mode. The method uses a constant voltage constant frequency pulse width modulation converter without regulating the DC capacitor voltage. The capacitor voltage is left changing with the loading conditions, and the AC side voltage is regulated by controlling the modulation index or the normalized d-axis reference voltage for space vector modulation. This eliminates the need for an auxiliary switch in the DC side, reducing the cost and high-frequency current components flowing in the DC capacitor and increasing its lifetime. Simulation results are given for comparing between the conventional and the proposed techniques when applied to a 6-kW generator. The proposed technique is tested under step changes in load and prime mover speed, and it gives the same response as the old technique but without the use of DC side switch. Experimental implementation of the proposed technique is tested on a 1-hp generator, and both simulation and experimental results are given to validate the proposed technique.

Digital Signal Processor Based Fuzzy Voltage and Frequency Regulator for Self-excited Induction Generator

This article presents digital design and implementation of a digital signal processor based fuzzy logic load controller to regulate the voltage and frequency of a three-phase self-excited induction generator through an equal time ratio control AC chopper controllable load that is suitable for a stand-alone power mode employing an unregulated turbine such as micro-hydro power generation. The self-excited induction generator can be used to generate constant voltage and frequency if the load is maintained constant at its terminals. Under such operation, the self-excited induction generator requires constant capacitance for excitation. For this purpose, a suitable control scheme is to be developed such that the load on the self-excited induction generator remains constant despite the change in the consumer load. The proposed fuzzy logic based load controller gives non-linear control with fast response and virtually no overshoot. The equal time ratio control AC chopper load controller regulates the dump load as a linear load with minimum harmonics and excellent dynamic response. The self-excited induction generator with such a control scheme is cost effective and provides quality power supply with minimum harmonics. A prototype self-excited induction generator-load controller system with a TMS320F2812 digital signal processor (Texas Instruments, USA) has been developed, and its transient behavior is investigated at different operating conditions such as application and removal of static (resistive and reactive) and dynamic loads.

A Novel Unified Approach for the Analysis and Design of Wind-Driven SEIGs Using Nested GAs

A unified procedure for the design optimization and performance predetermination of wind-driven three-phase Self-Excited Induction Generators (SEIGs) has been attempted using Genetic Algorithm (GA) twice, in two nested loops. The outer loop is meant for the calculation of the values of turns per coil of the stator winding and the excitation capacitor which would meet the specified performance constraints of the generator. The inner loop applies the GA tool for the first time, for a straightforward predetermination of these performance quantities. Further, additional schemes such as, switching of the stator connection from delta to star, at times of lower wind speed and short shunt arrangement suitable for lagging power loads, have also been included. Method of estimating the ranges for the variables, required to be given as input data into each of these two loops for the application of GA, has been explained. Experimental results obtained on a test machine and performance values predicted employing Genetic Algorithm, have been shown to agree closely, validating the comprehensive methodology proposed for the first time for the economical design of SEIGs for wind-driven applications.

Analysis of a stand-alone three-phase self-excited induction generator with unbalanced loads using a two-port network model

This work proposes an equivalent circuit model for a stand-alone three-phase self-excited induction generator (SEIG) with unbalanced load impedances. The SEIG supplying unbalanced loads is modelled by a two-port network that allows the steady-state performance of the generator to be analysed more easily and more efficiently. The proposed model is validated by experiments on a 0.5 Hp cage-type induction motor operated as a generator.

Abc-dq Modelling and Simulation of Wind-Driven Self-Excited Induction Generators

Abtractabc-dq axis model has been developed for the transient and steady state analysis of three-phase Self-Excited Induction Generators (SEIGs). Circuit model equations have been derived in the form of classical state space equations and the MATLAB/Simulink based programs have been formulated. Further, this abc-dq modelling and simulation have also been applied for the study of more complex systems such as SEIGs operated in parallel, SEIG supplying an induction motor load, and SEIG feeding a DC load through thyristor-controlled rectifier, and relevant voltage and current waveforms have been presented. Voltage building-up transients have been recorded experimentally for a three-phase, 400 V SEIG run at constant speed with a terminal capacitance of 80 μF per phase, and this waveform has also been verified with simulated results, thus confirming the validity of the proposed basic model for the operation of these generators.

Performance Analysis of Three-Phase Self-Excited Induction Generator Using Genetic Algorithm

This paper presents a new technique for the analysis of a three-phase self-excited induction generator feeding a three-phase balanced unity power factor load. A genetic algorithm has been proposed to find the generated frequency and magnetizing reactance simultaneously. This leads to a complete analysis of the self-excited induction generator. Computed results have been compared with experimental results. The comparison confirms the validity and accuracy of the proposed method.

Analysis and Design of Electronic Load Controller for Self-Excited Induction Generators

This paper presents an analysis and design of an electronic load controller (ELC) for three-phase self-excited induction generators (SEIGs) suitable for stand-alone pico-hydro power generation with constant input power. Here, the SEIG can be used to generate constant voltage and frequency if the electrical load is maintained constant at its terminals. Moreover, under such operation, SEIG requires constant capacitance for excitation resulting in a fixed-point operation. For this purpose, a suitable control scheme has to be developed such that the load on the SEIG remains constant despite change in the consumer load. In such applications, water is freely available and, hence, a simple and cheap controller has to be developed, which can operate almost unattended in remote and hilly regions. The proposed ELC consists of an uncontrolled rectifier and chopper with a series load. Proper design of rectifier, chopper, and dump load is very important for troublefree operation of ELC. In this paper, an analysis along with a design procedure for computing the rating of various components of ELC is presented for a range of SEIGs.

Matlab Simulink Based DQ Modeling and Dynamic Characteristics of Three Phase Self Excited Induction Generator

In this paper, DQ-modeling approach for Transient State analysis in the time domain of the three- phase self-excited induction generator (SEIG) with squirrel cage rotor is presented along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover (VSPM) such as a wind turbine for the clean alternative renewable energy in rural areas. Here the prime mover speed has been taken both as fixed and variable and results have been analyzed. The basic Dynamic characteristics of the VSPM are considered in the three-phase SEIG approximate electrical equivalent circuit and the operating performances of the three-phase SEIG coupled by a VSPM in the Transient state analysis are evaluated and discussed on the conditions related to transient occurs in the system and speed changes of the prime mover. The whole proposed system has been developed and designed using MATLAB/SIMULINK.