S. S. Murthy

Analysis and design of STATCOM-based voltage regulator for self-excited induction generators

This paper deals with the design of static compensator (STATCOM)-based voltage regulator for self-excited induction generators (SEIGs). SEIG has poor voltage regulation and it requires adjustable reactive power source with varying load to maintain constant terminal voltage. The required reactive power can be provided by a STATCOM consisting of ac inductors, a dc bus capacitor, and solid-state self-commutating devices. Selection and ratings of these components are quite important for design and control of STATCOM to regulate the terminal voltage of SEIG. The analysis, design, and selection of these STATCOM components are presented for five different rating machines to operate at varying power factor loads. Two criteria (full and reduced rating of STATCOM) are considered while designing STATCOM-SEIG systems.

STATCOM-Based Voltage Regulator for Self-Excited Induction Generator Feeding Nonlinear Loads

This paper deals with the performance analysis of a static compensator (STATCOM)-based voltage regulator for self-excited induction generators (SEIGs) supplying nonlinear loads. In practice, a number of loads are nonlinear in nature, and therefore, they inject harmonics in the generating systems. The SEIGs performance, being a weak isolated system, is very much affected by these harmonics. The additional drawbacks of the SEIG are poor voltage regulation and that it requires an adjustable reactive power source with varying loads to maintain a constant terminal voltage. A three-phase insulated-gate-bipolar-transistor-based current-controlled voltage source inverter working as STATCOM is used for harmonic elimination, and it provides the required reactive power for the SEIG, with varying loads to maintain a constant terminal voltage. A dynamic model of the SEIG-STATCOM feeding nonlinear loads using stationary d-q axes reference frame is developed for predicting the behavior of the system under transient conditions. The simulated results show that SEIG terminal voltage is maintained constant, even with nonlinear balanced and unbalanced loads, and free from harmonics using STATCOM-based voltage regulator

A novel self-induced self-regulated single phase induction generator. I. Basic system and theory

This paper describes a newly developed single phase capacitor self excited induction generator with self regulating features, suitable for oil engine driven portable gen-sets for autonomous/standby power generation. The system is also suitable for microhydel and wind energy systems. The generator has two specially designed stator windings in quadrature, connected externally to a shunt and a series capacitor respectively. It employs a standard die-cast squirrel cage rotor. Special features, advantages and theoretical concepts of the system are highlighted. >

Isolated Wind–Hydro Hybrid System Using Cage Generators and Battery Storage

This paper deals with a new isolated wind-hydro hybrid generation system employing one squirrel-cage induction generator (SCIG) driven by a variable-speed wind turbine and another SCIG driven by a constant-power hydro turbine feeding three-phase four-wire local loads. The proposed system utilizes two back-to-back-connected pulsewidth modulationcontrolled insulated-gate-bipolar-transistor-based voltage-source converters (VSCs) with a battery energy storage system at their dc link. The main objectives of the control algorithm for the VSCs are to achieve maximum power tracking (MPT) through rotor speed control of a wind-turbine-driven SCIG under varying wind speeds and control of the magnitude and the frequency of the load voltage. The proposed wind-hydro hybrid system has a capability of bidirectional active- and reactive-power flow, by which it controls the magnitude and the frequency of the load voltage. The proposed electromechanical system using SCIGs, an MPT controller, and a voltage and frequency controller are modeled and simulated in MATLAB using Simulink and Sim Power System set toolboxes, and different aspects of the proposed system are studied for various types of linear, nonlinear, and dynamic loads, and under varying wind-speed conditions. The performance of the proposed system is presented to demonstrate its capability of MPT, voltage and frequency control (VFC), harmonic elimination, and load balancing.

An improved method for the determination of saturation characteristics of switched reluctance motors

Experimental determination of magnetization characteristics of switched reluctance motors (SRMs) is quite important in their accurate performance prediction. Over the last decade, various experimental procedures have been used to obtain these characteristics. Every evolved new method has its own limitations and constraints. This paper describes an improved, simple and cost effective experimental procedure and an equally simple post-experimental data processing to obtain the flux-linkage-current curves at varying rotor positions of the SRM. The experimental results on a 4 kW, four-phase, 8/6 pole SRMs show the effectiveness of the method and the results compare well with the previously results compare well with the previously published results of similar and higher rating SRMs.

Analysis of grid connected induction generators driven by hydro/wind turbines under realistic system constraints

Results of an investigation dealing with the behaviour of grid-connected induction generators (GCIGs) driven by typical prime movers such as mini-hydro/wind turbines are presented. Certain practical operational problems of such systems are identified. Analytical techniques are developed to study the behavior of such systems. The system consists of the induction generator (IG) feeding a 11 kV grid through a step-up transformer and a transmission line. Terminal capacitors to compensate for the lagging VAr are included in the study. Computer simulation was carried out to predict the system performance at the given input power from the turbine. Effects of variations in grid voltage, frequency, input power, and terminal capacitance on the machine and system performance are studied. An analysis of self-excitation conditions on disconnection of supply was carried out. The behavior of a 220 kW hydel system and 55/11 kW and 22 kW wind driven system corresponding to actual field conditions is discussed. >

An improved electronic load controller for self-excited induction generator in micro-Hydel applications

This paper describes the mathematical modelling of self-excited induction generators (SEIGs) with are improved electronic load controller (IELC) for microhydel applications supplying variety of loads. In small hydro plants, governor unit of turbine can be eliminated using IELC, which is simple and cost effective. The improved electronic load controller is a combination of a three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) and a high frequency DC chopper which keeps the generated voltage and frequency constant in spite of change of balanced/unbalanced loads. A dynamic model of the SEIG- IELC supplying different types of loads using stationary d-q axes reference frame is developed for predicting the behavior of the system under transient conditions. The simulation is carried out for compensation of balanced/unbalanced loading conditions. The simulated results show that generated frequency and voltage remain constant with change in load. The proposed IELC acts as reactive power compensator, harmonic eliminator, load balancer and load controller.

A novel self-exited self-regulated single phase induction generator. II. Experimental investigation

Part I of this paper presents the basic system, theoretical modelling and typical test results of a novel self-excited self regulated induction generator. In this part, the results of a detailed experimental investigation are presented to assess its suitability for practical applications. The steady state performance of the self-excited single phase induction generator, maintaining the terminal voltage within a close range is investigated under realistic loading conditions in the laboratory. Detailed experimental results are presented and discussed. Necessary tests to obtain machine parameters for theoretical modelling are also developed and relevant results of the prototype presented. The effects of series and shunt capacitors, prime mover speed, load and load power factor are investigated. It has been shown to exhibit a better voltage waveform as compared to commercially available sets. The experimental results confirm that this new generating system can be favourably employed for use as a small portable generator driven by nearly constant speed prime movers such as oil engines or hydro turbines. >

A Novel Electronic Controller Implementation for Voltage Regulation of Single Phase Self-Excited Induction Generator

A new scheme for voltage regulation of standalone single phase self excited induction generator (SEIG) is proposed. The thyristor switched capacitor scheme with electronic controller is designed and implemented for the reactive power supply and voltage regulation of single phase two winding SEIG reported earlier [1-2]. The recorded waveforms and test results verify the correct and proper operation of all the sections of controller design as implemented in the laboratory. The object of this scheme is to provide a standalone single phase SEIG with acceptable voltage regulation with the help of inexpensive, simple thyristor switched capacitors, suitable for low power generator with single phase out put driven by any fixed speed prime mover such as an engine energized by oil or bio-fuel. The use of SEIG reduces the capital and maintenance cost of the system, while the electronic controller along with capacitors provides acceptable voltage regulation at its output terminal. Such a system is specially suited for portable/standby generator units of 1 to 10 kW rating. Experimental results demonstrate the viability of the scheme for practical deployment.

A Voltage and Frequency Controller for Self-Excited Induction Generators

This article describes a controller for voltage and frequency control of self-excited induction generator (SEIG) supplying static/dynamic, balanced/unbalanced loads. The controller is a combination of a three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) and a high frequency DC chopper, which keeps the generated voltage and frequency constant in spite of change in consumer loads. A mathematical model of the SEIG with this controller supplying different types of loads is developed for predicting the behavior of the system under transient and dynamic conditions. The simulated results show that generated frequency and voltage remain constant with change in load. The proposed controller acts as reactive power compensator, harmonic eliminator, load balancer, and frequency and voltage regulator.