28-03-2012, 02:22 PM
GENETIC ALGORITHM BASED SOLUTION IN PWM CONVERTER SWITCHING FOR VOLTAGE SOURCE INVERTER FEEDING AN INDUCTION MOTOR DRIVE
Genetic algorithm based solution in pwm converter switching for voltage source inverter feeding an induction motor drive (Size: 304.01 KB / Downloads: 61)
INTRODUCTION
The use of power electronic equipments has increased in recent years in industrial and consumer
applications. Such loads draw nonlinear sinusoidal current and voltage from the source and
results in harmonics in the networks (1). They occur frequently in variable frequency drives or
any electronic devices using solid state switching method to convert AC or DC.
Pulse width modulation has been the subject of intensive research during the last few decades.
Different types of feed forward and backward pulse width modulation schemes having relevance
for industrial application have been widely discussed(2) .
3. GENETIC ALGORITHM METHOD TO SOLVE THE PROPOSED PWM
SWITCHING PATTERN
Genetic Algorithms (GA) are numerical optimization algorithms based on the principle inspired
from the genetic and evolution mechanisms observed in natural system and population of living
beings. Binary encoding GA is dealing with binary strings, where the number of bits of each
string simulates the genes of an individual chromosome, and the number of individuals
constitutes a population. Each parameter set is encoded into a series of a fixed length of string
symbols usually from the binary bits, which are then concatenated into a complete string called
chromosome. Substrings of specified length are extracted successively from the concatenated
string and are then decoded and mapped into the value in the corresponding search space.
Generally, GA implementation comprises the procedures of initial population generation, fitness
evaluation and genetic operations of selection, crossover and mutation.
SIMULATION RESULTS
After obtaining the switching angles through the MATLABTM using Genetic Algorithm, the proposed system was developed using Powersim. The circuit uses 230V single phase AC supply sources which was connected to the star connected primary winding of the 3 phase star/delta transformer. The 6 pulse voltage source rectifier was developed using six diodes as bridge. This rectifier is being connected to Voltage Source Inverter through the Inductor and Capacitor which was acting as a DC link between the rectifier and inverter. The load connected to the inverter is a three phase squirrel cage induction motor, where high capacity dual transformer and 12 pulse rectifier are not used to eliminate certain lower order harmonics in Genetic Algorithm approach. Simulations were carried out on a Pentium III 933-MHz, 256–MB RAM processor.
CONCLUSION
An efficient technique of calculating switching angles through the Genetic Algorithm method is illustrated. An optimized PWM-SHE switching method is proposed for 3 phase Inverter circuit with 6 pulse converter as the power circuit for 3 phase drive system. This method avoids usage of 12 pulse rectifier and the traditional complex calculations. Analysis of the Harmonics spectrum shows that, all the harmonics up to 13th are eliminated. According to the experimental and simulated results, the characteristic harmonics of six pulse rectifier, 5th, 7th, 11th and 13th are totally eliminated by Genetic Algorithm without using high capacity dual transformer connections. It remains to be a topic for further investigations to design similar real-time PWM systems.