Bhagwan K. Murthy

Dynamic analysis of a grid-connected induction generator driven by a wave-energy turbine through hunting networks

The presence of forced oscillations occurring in a Wells Turbine driven grid-connected induction generator enables one to seek a solution by considering the analogy between the dynamics of the Wells Turbine drives systems with those associated with diesel-engine driven generators or electric motors driving reciprocating compressors, where also such forced oscillations occur, although there they occur in synchronism with shaft-position or speed. This difference is taken into account and the hunting network theory, which has hitherto been applied to the dynamic analysis of motors driving reciprocating compressors, is applied to analyse the dynamics of a Wells Turbine driven grid-connected induction generator. The method enables the generator current, power and slip to be predicted from a knowledge of the shaft-torque harmonics. The result is compared with that obtained through d-q analysis.

Rotor Side Control of Wells Turbine Driven Variable Speed Constant Frequency Induction Generator

Abstract Wave energy can meet a sizeable portion of the worlds energy needs. For countries having long coastlines, wave energy conversion is an attractive proposition. Wells turbine driven grid–connected systems with squirrel cage induction generators have been in existence; however, rotor–side control of grid–connected induction machine is an attractive option for variable speed constant frequency operation. The power rating of the converter can be considerably reduced when used in the rotor circuit over a limited slip range (approximately 50%). Since the stator is directly connected to the grid, the stator flux is constant over the entire operating region. Therefore, the torque can be maintained at its rated value even above synchronous speed. This article describes the simulation of a rotor side chopper controller for wave energy.

Control of Induction Generator in a Wells Turbine Based Wave Energy System

This paper describes a method for controlling a Wells-turbine driven induction generator to extract maximum power and feed it to the grid. The optimum voltage and frequency to be applied to the stator of the squirrel cage induction generator at any air velocity is obtained. This information can be used to design a suitable power electronic controller

Dynamic analysis of a grid-connected induction generator driven by a wave-energy turbine

This paper presents a methodology for predicting instantaneous values of electrical quantities such as active power, reactive power, power factor, current, torque and slip of the grid-connected induction generator driven by a Wells turbine from given data of axial air flow velocity variations with time so that the quality of power fed to the grid can be predicted. An index of power quality could be the ratio of peak active power to average active power. The paper then establishes the effect of taking the electrical transients into account or omitting the same on the accuracy of the modelling for such dynamic studies.

Buck-Boost Interleaved Inverter Configuration for Multiple-Load Induction Cooking Application

Induction cooking application with multiple loads need high power inverters and appropriate control techniques. This paper proposes an inverter configuration with buck-boost converter for multiple load induction cooking application with independent control of each load. It uses one half-bridge for each load. For a given dc supply of VDC, one more VDC is derived using buck- boost converter giving 2VDC as the input to each half-bridge inverter. Series resonant loads are connected between the centre point of 2 VDC and each half-bridge. The output voltage across each load is like that of a full-bridge inverter. In the proposed configuration, half of the output power is supplied to each load directly from the source and remaining half of the output power is supplied to each load through buck-boost converter. With buck-boost converter, each half-bridge inverter output power is increased to a full-bridge inverter output power level. Each half-bridge is operated with constant and same switching frequency with asymmetrical duty cycle (ADC) control technique. By ADC, output power of each load is independently controlled. This configuration also offers reduced component count. The proposed inverter configuration is simulated and experimentally verified with two loads. Simulation and experimental results are in good agreement. This configuration can be extended to multiple loads.

Multiple-Load Induction Cooking Application with Three-Leg Inverter Configuration

Inverter configurations for multiple-load induction cooking applications need development. Inverter configurations for induction cooking applications are used in home appliances based on single coil inverters. For multiple-load configurations, multiple coils are used. They require proper inverters, which provide independent control for each load and have fewer components. This paper presents a three-leg inverter configuration for three load induction cooking applications. Each induction coil powers one induction cooking load. This configuration operates with constant switching frequency and powers individual loads. The output power of the required load is controlled with a phase-shift control technique. This configuration is simulated and experimentally tested with three induction loads. The simulation and experimental results are in good agreement. This configuration can be extended to more loads.

Class-D/E resonant inverter for multiple-load domestic induction cooking appliances

This paper presents a class - D/E resonant inverter for multiple-load domestic induction cooking appliances. Most of the induction inverter configurations used in home appliances is based on single coil inverter. In these configurations, the vessel size cannot be more than induction coil size. The proposed configuration is suitable for any size of vessel and also can be used for multiple-loads. It operates with constant switching frequency and independent control of each load. The output power of each load can be controlled with asymmetrical duty cycle control technique for class-D configuration and with asymmetrical voltage cancellation control technique for class-E configuration. The proposed configuration and control techniques are simulated and experimentally tested with two loads. Simulation and experimental results are in good agreement. This configuration can be extended to multiple-loads.

A full bridge resonant inverter with multiple loads for induction cooking application

In this paper full bridge resonant inverter with independent output power control of two loads for induction cooking application is presented. The proposed configuration can be operating with efficient ZVS by constant switching frequency and constant duty ratio of full bridge resonant inverter. By varying the duty ratio of load switch, each load output power is controlled individually. And in this proposed configuration, synchronization of load switch switching pulse with inverter output voltage is done for output power control. The proposed configuration can be extended to multiple loads. It is more reliable for multiple load induction cooking application with output power control of each load independently. For theoretical predictions, the proposed configuration of two load full bridge resonant inverter for induction cooking application with independent control of each load is simulated in MATLAB/Simulink environment.