Intelligent management and control of electrical loads using microcontroller-based embedded systems
Φόρτωση...
Ημερομηνία
2015-05
Συγγραφείς
Zigkirkas, Grigorios
Ζιγκίρκας, Γρηγόριος
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
Τ.Ε.Ι. Κεντρικής Μακεδονίας
Δικαιώματα
Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 4.0 Διεθνές
Άδειες
Παραπομπή
Παραπομπή
Περίληψη
The design and implementation of an intelligent 3-phase, programmable soft-start
controller, for low voltage induction motors is presented. The controller is implemented
with a low-cost microcontroller and is based on a timer-driven, fuzzy-logic closed loop.
A TRIAC-based switching circuit in series with the line voltage is used for current flow
control during start-up. A timer-based embedded application adjusts the TRIAC
triggering angle by shifting the TRIAC ignition pulse within the voltage period at a
constant rate. Multitasking logic controls all three phases simultaneously. As a result,
the voltage is gradually increased in the three-phase system, until the motor reaches full
speed. An external user-defined setting can adjust the time frame from start to full
speed. Certain improvements are introduced with regard to former similar designs, the
most important being a closed-loop, voltage sensing, three-rule fuzzy system that
effectively balances the inductive behavior and restores a predictable time-ramp at
start-up. Because of the inductive character of three-phase asynchronous motors, the
residual current after switch-off leads to higher nominal voltage across the motor coils,
depending on the actual load. Therefore, it is found that an open-loop timer-driven
switching logic is not adequate for a reliable soft start controller, since it can result in
start-up time being unpredictably shorter than the one corresponding to user settings.
In order to adjust torque to load behavior and produce a constant ramp depending
only on user-defined time settings, a closed-loop fuzzy-logic system is introduced. A
voltage sensor acquires the residual voltage in one of the system’s phase lines at
adequate sampling rate and computes an input to a three-rule fuzzy system, in the form
of an error function. The output of the system infers the time interval to the next
ignition pulse. Both the timer logic and the fuzzy system logic are embedded in a lowcost
PIC18F252 microcontroller. The behavior of the soft-start controller is smooth and
predictable. The voltage ramp from zero to maximum voltage is very close to that
corresponding to an equivalent ohmic load.
Περίληψη
Περιγραφή
Λέξεις-κλειδιά
TEICM::ΜΙΚΡΟΕΛΕΓΚΤΕΣ::ΜΙΚΡΟΕΛΕΓΚΤΕΣ -- ΠΡΟΓΡΑΜΜΑΤΙΣΜΟΣ, ΕΝΣΩΜΑΤΩΜΕΝΑ ΣΥΣΤΗΜΑΤΑ ΗΛΕΚΤΡΟΝΙΚΩΝ ΥΠΟΛΟΓΙΣΤΩΝ