Approximation of Optimized Fuzzy Logic Controller for Shunt Active Power Filter - Complex System Modelling and Control Through Intelligent Soft Computations - page 569

Fig. 6 Different membership functions used for performance comparison and selection of
optimized membership function

µ(e,ce)
1

NL NM NS ZE PS PM PL

0 1/3 2/3

-1 -2/3 -1/3 1

Fig. 7 Triangular membership functions for input variables error (e) and change in error (ce)of
49-rule FLC

In 49-rule FLC, seven MFs are used for both input and output variables to cover
entire UOD as shown in Figs. 7 and 8 (for triangular MFs), similar uniform dis-
tribution of UOD is used for other MFs.
The linguistic variables used to represent seven membership functions are
negative Big (NB), negative medium (NM), negative small (NS), zero (ZE),
positive small (PS), positive medium (PM) and positive big (PB). The range of
UOD is taken [

1, 1], for input as well as output variables.
Based on the performance of shunt APF in terms of dynamic and harmonic
compensation indices the optimized large rule FLC is selected for approximation.
The approximation technique is discussed in next section.

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