Induction

Topics: Direct current, PIC microcontroller, Induction generator Pages: 6 (2776 words) Published: May 5, 2014
S. Ünal, M. Özdemir, S. Sünter, “Voltage and Frequency Control of a Single-Phase Self-Excited Asynchronous Generator” International Aegean Conference on Electrical Machines and Power Electronics (ACEMP), İstanbul-Turkey, May, 2004, pp.509-514.

Voltage and Frequency Control of a Single-Phase Self-Excited Asynchronous Generator
Sencer Ünal

Mehmet Özdemir

Sedat Sünter

Department of Electrical and Electronic Engineering,
Fırat University
Elazığ, 23119 Turkey
Email:sencerunal@firat.edu.tr Tel : +90 (424) 237 00 00 Fax : +90 (424) 241 55 26

Abstract
In this paper, voltage and frequency control of a
single-phase self-excited asynchronous generator
driven by a dc machine with variable speed has been
proposed. Here, an IGBT based single-phase PWM
inverter controlled by a PIC microprocessor was
used to adjust the output frequency of a single-phase
self-excited
asynchronous
generator.
PIC
microprocessor produces SPWM signals by
implementing the asymmetrical regular-sampled
sine-PWM technique and then frequency of the
output voltage is adjusted by controlling IGBT
devices in the inverter.
Condenser group is controlled by PIC controller to
keep the output voltage of the generator constant at
variable operating conditions. In this method, the
microprocessor samples the voltage data from the dc
link and then turns the condenser on or off into the
system depending on variations in the voltage. In
this way the dc link voltage is kept constant.
The complete system has been simulated by using
Matlab/Simulink package program. Comparison of
the simulation and experimental results has shown
the satisfactory operation of the single-phase selfexcited asynchronous generator.

1 Introduction
Recently increase in energy demand and limited
energy sources in the world caused the researchers
to make effort to provide new and renewable energy
sources for the usage in an economical and safe way.
The use of the asynchronous generators which can
produce electricity in variable speeds has become a
proper way for the renewable energy sources such as
wind, natural gas and rivers with low flow. In
addition rapid developments in power electronics
and microprocessors have made the use of
asynchronous generators more popular in this
application. Especially, load sharing can be
performed easily by using them in single or threephase micro-grid systems with the aid of power electronic circuit arrangements such as inverters and
converters [1, 2, 3].

In order to run a single-phase asynchronous machine
as a self-excited generator the machine must be
driven by another driver and a condenser, which will
provide a required magnetizing current, must be
connected across the terminals. When the machine is
excited at the required speed, remnant magnetization
in the rotor will induce a small emf in the stator
windings. The condenser at the terminals of
generator causes a continuous increase in the
induced voltage and hence produced voltage until
the generator reaches to saturation due to magnetic
saturation of the machine [4]. The speed of the drive
system and value of the condensers connected to the
generator affect the self excitation time of the
generator, the produced voltage and its frequency. In
addition, the load to be connected to the terminals of
the generator, depending on the load characteristic,
will also change the magnetizing current of the
generator and hence the terminal voltage will also be
affected. The main purpose of this kind of systems is
to produce and keep constant voltage and frequency
if there is a change in the speed of the drive system
and loading conditions.
Many researches are being carried on keeping the
voltage and frequency level of the generator constant
[5-7]. In these studies, systems such as bipolar PWM
inverters and battery groups are used. Whilst the
auxiliary winding of the single phase asynchronous
generator is supplied by a dc-ac inverter fed by...
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