Approximation of Optimized Fuzzy Logic Controller for Shunt Active Power Filter - Complex System Modelling and Control Through Intelligent Soft Computations - page 567

technique to approximate the control actions of a 49-rule FLC by a simplest 4-rule
FLC. The proposed approximation results in a less complex fuzzy structure, with
tremendously reduced memory requirement and computational time.

3 Fuzzy Logic Controller

Fuzzy logic is a branch of arti cial intelligence that deals with the reasoning

algorithms used to emulate human thinking and decision making in machines. The
fuzzy logic controller (FLC) based on fuzzy logic provides a method of converting
a linguistic control strategy using expert knowledge into an automatic control
strategy. The primary thrust of this novel control paradigm is to utilize the human
operator s knowledge and experience to develop controllers intuitively. In this

chapter, an FLC is designed to improve the dynamic response of shunt APF. The
conventionally designed FLCs use large number of rules to provide precise control,
but with an increased complexity, memory requirement and computation time.

'

3.1 Basic Structure of Fuzzy Logic Controller

The basic structure of fuzzy logic controller (FLC) is shown in Fig. 5 . In general, a
fuzzy logic system maps crisp input into crisp output and in such case contains
three major modules:

1. Fuzzi cation,

2. Knowledge Base and Inference engine, and
3. Defuzzi

cation

Input Output

Fuzzification
Interface

Defuzzification
Interface

Inference Engine

Knowledge Base

Data base Rule base