Rm. Hilloowala et Am. Sharaf, A RULE-BASED FUZZY-LOGIC CONTROLLER FOR A PWM INVERTER IN A STAND-ALONE WIND ENERGY-CONVERSION SCHEME, IEEE transactions on industry applications, 32(1), 1996, pp. 57-65
The paper presents a rule-based fuzzy logic controller to control the
output power of a pulse width modulated (PWM) inverter used in a stand
alone wind energy conversion scheme (SAWECS). The self-excited induct
ion generator used in SAWECS has the inherent problem of fluctuations
in the magnitude and frequency of its terminal voltage with changes in
wind velocity and load. To overcome this drawback the variable magnit
ude, variable frequency voltage at the generator terminals is rectifie
d and the de power is transferred to the load through a PWM inverter.
The objective is to track and extract maximum power from the wind ener
gy system (WES) and transfer this power to the local isolated load. Th
is is achieved by using the fuzzy logic controller which regulates the
modulation index of the PWM inverter based on the input signals: the
power error e = (P-ref - P-o) and its rate of change over dot e. These
input signals are fuzzified, that is defined by a set of linguistic l
abels characterized by their membership functions predefined for each
class. Using a set of 49 rules which relate the fuzzified input signal
s (e.overdot e) to the fuzzy controller output U, fuzzy set theory and
associated fuzzy logic operations, the fuzzy controller's output is o
btained. The fuzzy set describing the controller's output (in terms of
linguistic labels) is defuzzified to obtain the actual analog (numeri
cal) output signal which is then used to control the PWM inverter and
ensure complete utilization of the available wind energy. The proposed
rule-based fuzzy logic controller is simulated and the results are ex
perimentally verified on a scaled down laboratory prototype of the SAW
ECS.