Wind-driven Self-excited Induction Generators Research Articles

The Behavior of Terminal Voltage and Frequency of Wind-Driven Single-Phase Induction Generators under Variations in Excitation Capacitances for Different Operating Conditions

This paper assesses the behavior of output voltage and frequency of wind-driven self-excited induction generators with variable excitation capacitances connected to the main and auxiliary windings under different operating conditions. The optimum values of the main winding excitation capacitance for fixed terminal voltage operation under different values of shunt capacitance, load, and speed are also evaluated. The obtained results show that the terminal voltage is highly affected by changing the main winding excitation capacitance. In addition, the frequency is greatly affected by changing the auxiliary winding excitation capacitance. However, under different operating conditions, variation in the output frequency under different values of the main winding capacitance, with fixed auxiliary winding capacitance, is acceptable. Extensive simulations were conducted and the results are discussed in this publication.

Control algorithm for coordinated operation of wind-solar microgrid standalone generation system

ABSTRACT In this paper, a wind-driven self-excited induction generator (SEIG) combining solar photovoltaic (SPV) and battery storage has been successfully demonstrated. A second-order sequence filter-based frequency locked loop (SOSF-FLL) control is implemented for operating the voltage source converter (VSC). The SOSF-FLL method is designed by replacing two second-order low pass filter (LPF) pure integrators with two reduced order generalized integrators (ROGIs). The SOSF-FLL has a nonlinear control feedback system. The major contributions in this study include: 1. Implementation of SOSF-FLL control to generate reference source currents for VSC and evaluate the amplitude of load current component under intermittent condition of renewable energy sources (RESs) and nonlinear load, 2) The control algorithm with VSC performs numerous functions such as voltage/frequency regulation, load leveling, harmonic reduction, active/reactive power compensation and reduces the overall power quality problems, 3) Through DC-link voltage management, a bidirectional converter (BDC) with battery storage optimizes the best power flow to provide power balancing between the sources and the unbalanced load, 4) Under diverse operating situations, an incremental conductance (INC)-based maximum power point tracking approach with BDC control provides quick system convergence and support frequency. Moreover, a comparison is carried out between SOSF-FLL control and conventional control algorithms. The settling time of the proposed control is very less than one cycle (20 ms) within 2% described limit, whereas the conventional control algorithms show oscillations of more than 5% during the load dynamics. Despite the load current THD 24.41%, the proposed control is able to obtain supply current THD at 4.23%, which is less than 5% as per IEEE-519 standard. The proposed microgrid (MG) is constructed in MATLAB/Simulink and experimental prototype environment, and its dynamic response is investigated under dynamic conditions of RESs and nonlinear load conditions.

Genetic algorithm‐based analysis of wind‐driven parallel operated self‐excited induction generators supplying isolated loads

A procedure based on genetic algorithm (GA) has been formulated for the performance predetermination of wind-driven self-excited induction generators (SEIGs) operating in parallel and supplying common loads. Both static and induction motor (IM) loads have been considered. The GA technique has also been applied for the evaluation of the excitation capacitor required for obtaining a desired terminal voltage for a given speed and load. This technique is also used for the predetermination of the upper and lower limits of the rotor speed of any SEIG in the parallel set up, to keep all the machines in the generating mode. The necessity of the terminal voltage equality of all the parallel operating machines serves as one of the factors in the formation and minimisation of the objective function, leading to the solution for the unknown magnetising reactances and core loss resistances of the various induction machines and the common frequency of operation of the set-up. Experimental results obtained on the SEIGs have been furnished and they are shown to be in close agreement with predetermined values using the GA method. The analysis developed herein will be useful in forming AC and DC microgrids, fed by several SEIGs.

Build‐up steady‐state analysis of wind‐driven self‐excited induction generators

For the contradiction between the increasing importance of the application of induction generator in the new energy power generation such as wind energy and the relative laggard of research on its comprehensive performance, the build-up steady-state analysis is performed for the wind-driven self-excited induction generator (SEIG) system based on the unloaded transient equivalent circuits and its mathematic model of SEIG in the two-phase stationary reference frame. Thus, it obtains the build-up steady-state conditions represented by the unloaded transient mathematic model. On the basis of the result obtained for the build-up steady-state limit cycle condition, the analytic solution for the build-up steady-state operating point condition and the analytic formulas for the limit magnetising induction are further obtained. Example analysis is to test out the only set of analytic solution for the build-up steady-state condition. Thus, the analytic solution for the build-up steady-state condition produces the formulas of the torture and the power factor, which can be applicable to further analysis for the system dynamics and build-up steady-state operating performance, showing practicability and referenced value in engineering.

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.

PSO-based MPPT control of wind-driven Self-Excited Induction Generator for pumping system

In recent years, much research has been done to improve the performance of a wind energy conversion system at various wind speeds using Maximum Power Point Tracking (MPPT) algorithms to find an efficient production of peak energy.In most cases, the MPPT techniques used to maximize the turbines power coefficient neglect the effect of losses generated by the system components, which can shift the true optimal operating point of the wind turbine. Furthermore, conventional MPPT methods such as Perturbation and Observation (P&O) and Incremental of Conductance (IncCond), need to sense both the rotor speed and the power of the wind turbine. In addition, other methods such as Fuzzy Logic and neural networks based on MPPT algorithms are proposed but these methods require knowledge of the wind speed and system parameters for the training phase.In this context, a new MPPT technique is being proposed in this paper, based on Particle Swarm Optimization (PSO) for a standalone Self-Excited Induction Generator (SEIG) operating at variable wind speed and supplying an induction motor coupled to a centrifugal pump.

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.

Analysis and control of wind-driven self-excited induction generators connected to the grid through power converters

The analysis of the wind-driven self-excited induction generators (SEIGs) connected to the grid through power converters has been developed in this paper. For this analysis, a method of representing the grid power as equivalent load resistance in the steady-state equivalent circuit of SEIG has been formulated. The technique of genetic algorithm (GA) has been adopted for making the analysis of the proposed system simple and straightforward. The control of SEIG is attempted by connecting an uncontrolled diode bridge rectifier (DBR) and a line commutated inverter (LCI) between the generator terminals and three-phase utility grid. A simple control technique for maximum power point tracking (MPPT) in wind energy conversion systems (WECS), in which the firing angle of the LCI alone needs to be controlled by sensing the rotor speed of the generator has been proposed. The effectiveness of the proposed method of MPPT and method of analysis of this wind-driven SEIG-converter system connected to the grid through power converters has been demonstrated by experiments and simulation. These experimental and simulated results confirm the usefulness and successful working of the proposed system and its analysis.

Direct Voltage Control for a Stand-Alone Wind-Driven Self-Excited Induction Generator With Improved Power Quality

An improved direct voltage control (DVC) strategy is proposed for the control of terminal voltage and frequency of a stand-alone wind-driven self-excited induction generator with variable loads. The DVC strategy, including a proportional-integral (PI) regulator, lead-lag corrector, and a feed-forward compensator, is designed based on the system transfer function matrix. The PI regulator can eliminate the steady-state tracking errors of the terminal voltage. The lead-lag corrector is employed to enlarge the phase stability margin of the dominant loops while the feed-forward compensator is adopted to mitigate the voltage harmonics resulting from the cross-coupling dynamics. The procedures for capacity design of the excitation capacitors, the voltage source inverter, and the consumer load are also presented. The simulation and experimental results verify that the proposed strategy has a fast dynamic response and can effectively control the generated voltage with low harmonic distortions under different linear or nonlinear loads.

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.

Wind-Driven Self-Excited Induction Generator With Voltage and Frequency Regulated by a Reduced-Rating Voltage Source Inverter

This paper discusses the regulation of the voltage and frequency of a stand-alone fixed-pitch wind energy conversion system (WECS) based on a self-excited squirrel-cage induction machine. A shunt connected voltage source inverter (VSI) and a controllable dump load are used for regulation purposes. A battery bank is included in the dc side of the VSI so that it can absorb and inject active power thus increasing the efficiency and availability of the system. A control scheme for the VSI with independent control of active and reactive power allows the state of charge of the batteries to be kept in a safe range while maximizing the voltage regulating capabilities of the VSI. The characteristics of the wind turbine, self-excited generator, and the ratings of the VSI are considered in order to determine the load range for which voltage and frequency can be regulated for a given wind speed range. The feasibility of the proposed system is verified by simulations.

Design Optimisation and Speed Extension of Wind-Driven Self-Excited Induction Generators—A New Approach

An economical design of self-excited induction generators has been proposed, which requires only insertion of appropriate stator winding and excitation capacitor, in available well designed induction machines of suitable rating. Using Genetic Algorithm and least pth optimisation techniques, a program has been developed for the calculation of the values of stator turns per coil and the capacitor, satisfying the required performance constraints of the generator, for wind-driven applications. Further, for obtaining an extended operating speed range of this wind-driven system, a simple stator winding switching scheme for the generator has been suggested, which results in optimum utilization of available wind potential, following cube law power curve. For such variable speed applications, this switching scheme has also been shown to be superior to the earlier methods of employing multiple capacitor connections or pole-changing windings.

Microprocessor-based voltage controller for wind-driven induction generators

A microprocessor-based closed-loop system has been developed for wind-driven self-excited induction generators using a controlled rectifier to maintain a constant DC load voltage with varying rotor speeds. The configuration and implementation of the control scheme are described. Test results on a self-excited induction generator demonstrate the satisfactory performance of both the hardware and the software of the control scheme, and the utility of the set-up as a whole. The steady-state analysis of the generator is extended to include the controlled rectifier, and the performance characteristics are predicted. >

Chopper-controlled wind-driven self-excited induction generators

Two chopper circuit configurations, one with voltage commutation, are shown to be useful for obtaining a controllable DC voltage from wind-driven self-excited pole-changing induction generators. For the case of a resistive load, expressions for the average load voltage and power are derived, and a set of normalized curves relating the voltage ratio and time ratio is drawn. Experimental results on a self-excited induction generator with a 4/6-pole combination using these choppers fully demonstrate the utility of the setup as a whole. Test results on an induction generator controlled by DC choppers demonstrate that any desired load voltage up to a maximum of input voltage can be maintained easily by varying the time period in the case of a load-commutated chopper and the on-off-time ratio in the case of a voltage-commutated chopper.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>