Self-excited Squirrel-cage Induction Generator Research Articles

Performance Evaluation and Dynamic Characteristics of a Self-Excited Induction Generator for Pico Hydro Power Plants

The dynamic performance of an isolated three-phase squirrel cage self-excited induction generator (SEIG) in a Pico Hydro Power Plant (PHPP) is examined in this work. The investigation is carried out with the help of MATLAB/Simulink for mathematical modeling and simulation of the proposed system under various operational situations. The SEIG model, which was created using the steady-state equivalent circuit approach, included the electrical, magnetic, and mechanical components of the SEIG and PHPP. The dynamic behavior of the SEIG is explored under a variety of operating situations. The effects of load variations, speed fluctuations, and other disturbances on the voltage and frequency of the generator are examined. The experiment results were used to validate the simulation results. This research has implications for the design and optimization of PHPP using SEIGs.

A grid forming control for wind energy conversion systems

This paper presents an effective and practical structure to improve voltage and frequency regulation in grid-forming control of self-excited induction generator-based wind energy conversion systems. In the proposed control structure, in addition to a fixed parallel excitation capacitor, a small wound rotor synchronous generator is also used as a reactive power compensator. The excitation voltage of the small synchronous generator is controlled in such a way that by injecting the required amount of reactive power, this generator maintains the balance between the inductive and the capacitive reactive powers in the isolated system, and thus, improves the system voltage regulation. In addition, an active power control is proposed in which the speed of the prime mover of the self-excited squirrel cage induction generator is adjusted in such a way that the active power of the small synchronous generator is maintained at zero value. The proposed power controller, by creating the balance between the generated and the consumed active powers, improves the frequency regulation of the wind energy conversion system. The validity and effectiveness of the proposed structure are demonstrated through both simulation studies and experimental implementation. The obtained results confirm that the poor regulation of voltage and frequency, which is one of the major drawbacks of self-excited induction generator-based wind energy conversion systems, has been significantly mitigated by using the proposed method.

Battery‐supported unified power quality controller for small hydro‐based isolated power generation

In this paper, a battery-supported unified power quality controller (UPQC) for a small hydro-based isolated power generation is investigated as a voltage and frequency controller. The self-excited squirrel cage induction generator driven by constant power prime mover (small hydro turbine) has unacceptable voltage, frequency and power quality under non-linear loads. The battery-supported UPQC-based voltage controlled-voltage source converter is designed, modelled and simulated in MATLAB environment. Here UPQC has series and shunt converters with a battery and it is used to feed the local loads. This small distributed power generation system is capable to feed unbalanced non-linear loads because a shunt converter is used to take care the compensation of unbalanced loads and it always maintains the source currents balanced and sinusoidal. Moreover, a series converter is used to inject the series voltages in the self-excited squirrel cage induction generator terminals to regulate the common coupling point voltage during unbalanced non-linear loads. Performance of a battery-supported UPQC is also validated experimentally using a laboratory prototype of a 3.7 kW, 230 V, 50 Hz capacitor excited induction generator.

Modelling and simulation of self-excited induction generator driven by a wind turbine

The excellent specifications of the isolated squirrel cage self-excited induction generator (SEIG) make it the first choice for use with renewable energy sources. However, poor voltage and frequency regulation (under load and speed perturbations) are the main problems with isolated SEIGs. Wide dependence on the SEIG requires prior knowledge of its behaviour with regard to variations in the input of mechanical power and output of electrical power to develop a control system that is capable of maintaining the voltage and frequency at rated values, as far as possible, with any change in the input or output power of the SEIG. In this paper, a mathematical model of a wind energy conversion system (WECS) based on a squirrel cage SEIG with a generalized impedance control (GIC) was built using the Matlab/Simulink environment in a d-q stationary reference frame. A fuzzy logic controller (FLC) was used to control the parameters of the GIC. The training of the FLC was conducted by a neural network through Matlab's Neuro-Fuzzy designer. The results of this paper showed that the trained FLC succeeded in controlling the real and reactive power flow between the SEIG and the GIC system, in which the maximum variation for both magnitude and frequency of the generated voltage with any load or wind speed perturbation will not exceed (0.2 %) for the frequency and (3 %) for the voltage magnitude in both directions. The SEIG model was validated by comparing the results obtained with those of well-known studies with the same rating and operating conditions

A SEIG-Based DC Nanogrid for Rural Electrification

The Government of India has launched several schemes for rural electrification by enhancing the penetration of renewable energy resources. This paper aims toward a DC nanogrid for rural electrification in India. The DC nanogrid consists of a self-excited squirrel cage induction generator, PV panel, a battery storage for smooth and reliable operation, and compatible converters for voltage regulation and required conversion. The proposed DC nanogrid has been modeled and simulated in MATLAB/Simulink. The proposed system maintains a constant 120 V DC at load terminal. The performance of WECS has been analyzed in the environment of MATLAB/Simulink, and the same has been validated using a prototype hardware developed in the laboratory.

A Reactive Power Based Reference Model for Adaptive Control Strategy in a SEIG

In this paper, a new control strategy is proposed for a three-phase squirrel-cage self-excited induction generator (SEIG) connected to a variable speed wind turbine in autonomous mode. In order to improve the dynamic performance of the mentioned vector control system, a model reference adaptive controller is used for online rotor time constant estimation. Thus, the main drawbacks of this method, which include the effects of the changes in machine parameters on rotor flux estimation, slip speed, the creation of instability problems and the system leaving vector control mode, are resolved. In this control strategy, a PI controller is used to control the dc voltage and three similar hysteresis current controllers (HCC) are used to control the switching of IGBTs. The results of the dynamic simulation indicate the desirable performance of the proposed system.

Power generation and control of a self excited squirrel cage induction generator

The self-excited squirrel cage induction generator (SEIG) is frequently considered as the most economical solution for powering customers isolated from the utility grid by wind energy because it derives its excitation from its own output terminal and neither an exciter nor voltage regulator is required. Its major drawbacks, however, are poor voltage and frequency regulation under variable load conditions. The aim of this paper is to investigate a feedback control strategy that takes a fraction of the output power and applies it to the prime mover as torque. The wind turbine is to be tied mechanically to the rotor of a squirrel cage induction which is fed with grid powerthat the generator supplies. A back to back converter is used to maintain a constant voltage/frequency relationship at the motor terminals. The implication of this model is investigated. The performance characteristics of the machine for various machine variables are also investigatedusing the MATLAB/SIMULINK environment.Keywords: Wind Power systems, Self-excited squirrel cage induction generator, squirrel cage induction motor, backto- back converter, simulation

Reduced converter topology for integrated wind and small‐hydro energy generation system

This study presents a robust and cost-effective microgrid topology for integrating two commonly available wind and small-hydro renewable energy sources. The proposed topology has two generators, one of them is self-excited squirrel cage induction generator driven by a small-hydro turbine and other one is permanent magnet brushless DC generator driven by a small-scale wind turbine. The proposed system is integrated using a voltage source converter and a boost converter which are maintaining voltage and frequency, mitigating power quality problems and performing mechanical sensorless maximum power point tracking, respectively. A battery bank is also used to balance the load and supply power mismatch and to ensure the supply for critical loads. The proposed control algorithm is tested and verified on a developed laboratory prototype of the system. Test results verify that voltage and frequency of the system are regulated and the power-quality-related issues are also resolved in this microgrid.

Experience in Developing a Single-Phase Two Winding 5 kW Self-excited Induction Generator for Off-Grid Renewable Energy Based Power Generation

This paper deals with the design and development of a novel single-phase two winding self-excited squirrel cage induction generator (SEIG) for off-grid renewable energy based power generation. The principles underlying the design process and experience with SPEED design tool are described to design a 5 kW, 50 Hz, 230 V, 4 pole single phase AC generator. All possible configurations to reduce harmonic components of induced e.m.f. are attempted for desired performance and to get an optimum design keeping in view the manufacturing constraints. The development of a prototype based on this design has been completed with the help of an industry. Typical test results on the prototype are presented to demonstrate its performance. Computed results are obtained with a design based computational procedure for performance analysis and a critical comparison is made with test results.

Modeling, control and fault diagnosis of an isolated wind energy conversion system with a self-excited induction generator subject to electrical faults

In this paper, a contribution to modeling and fault diagnosis of rotor and stator faults of a Self-Excited Induction Generator (SEIG) in an Isolated Wind Energy Conversion System (IWECS) is proposed. In order to control the speed of the wind turbine, while basing on the linear model of wind turbine system about a specified operating point, a new Fractional-Order Controller (FOC) with a simple and practical design method is proposed. The FOC ensures the stability of the nonlinear system in both healthy and faulty conditions. Furthermore, in order to detect the stator and rotor faults in the squirrel-cage self-excited induction generator, an on-line fault diagnostic technique based on the spectral analysis of stator currents of the squirrel-cage SEIG by a Fast Fourier Transform (FFT) algorithm is used. Additionally, a generalized model of the squirrel-cage SEIG is developed to simulate both the rotor and stator faults taking iron loss, main flux and cross flux saturation into account. The efficiencies of generalized model, control strategy and diagnostic procedure are illustrated with simulation results.

Impacto de métodos de sincronismo no desmpenho de geradores de indução auto-excitados

Este artigo analisa sistemas de controle digital, sem sensores mecânicos, usados para regular as tensões de saída de um gerador de indução com rotor gaiola de esquilo. Diferentes métodos de sincronismo são avaliados e seus desempenhos são comparados sob condições de carga distintas, incluindo cargas desequilibradas e não lineares. Resultados de simulação e experimentais são obtidos para demonstrar o impacto de sistemas de controle digitais distintos na distorção e no fator de desbalanço das tensões de saída.

A new microturbine-based dispersed generation scheme

Almost all of the commercial microturbine-based dispersed generation systems today are composed of a high-speed permanent-magnet alternator and a diode rectifier-PWM inverter pair. A dispersed generation scheme made up of a microturbine, an induction generator, and a diode rectifier-PWM inverter pair is introduced in this paper. A complete model for the self-excited squirrel-cage induction generator is developed and used to study the steady-state and transient behaviours of the overall system. The power delivered to the grid is controlled by an injected current control loop. The input/output power balance is maintained by regulating the DC-bus voltage using a new method based on the torque control of microturbine. Analysis shows that the Simulink simulation results of induction generator is a viable substitute for permanent magnet alternator in microturbine-based dispersed generation systems due to its low cost, low maintenance, rugged structure, and slack between rotor speed and terminal frequency, which isolates the transients of the grid from the generator system when the DC-bus capacitor size is reduced. Both schemes have been simulated and the simulation results are presented to compare the proposed scheme based on induction generator with the present microturbine-based dispersed generation scheme based on synchronous machine.