Page 119 - IJEEE-2022-Vol18-ISSUE-1

Jasim & Jasim
As inputs to the MPPT fuzzy logic controller, the error
E(n)=?P/?V and the change in voltage ?V (the user has the
option to choose the inputs of this Controller) were utilized.
Since dP/dV diminishes at MPP, then:
E(n) = P(n)-P(n-1)
V(n)-V(n-1)
?V(n) = V(n) - V(n - 1)
The fuzzy logic controller output, which is generally a
change in duty ratio (?D) of the power converter, may be
searched up in a rule base table if E and ?V are computed
and translated to linguistic variables. The linguistic variables
(allocated to ?D for various combinations of E and ?V) are
determined by the power converter in use as well as the user's
understanding. The fuzzy logic controller output ?D is
changed from a linguistic variable to a numerical variable
during the defuzzification stage [34].
Fuzzy logic-based MPPT controllers have proven to be
effective in a variety of atmospheric circumstances.
However, their success is heavily reliant on the user's or
control engineer's ability to select the appropriate error
computation and create the rule basis table. Whereas
increasing the number of linguistic variables improves the
output accuracy, it also increases the system's complexity.
Fuzzy technique is used to obtain the MPP in this paper, and
a Proportional Integral (PI) controller is adopted to control
the boost when a curtailment operation is required.
+_ dv Fuzzy MPPT
Fuzzification
Delay ?
Fuzzy rule
V (k) × P (k) × dp Defuzzification
I (k) +_ dv
Delay
?D
Fig.7: the fuzzy logic controller's block diagram
Fig.8: Membership Functions: (a) Change in voltage (b)
Change in dp/dv
| 115
The fuzzy rules are written as:
? If dv is Neg. and dp/dv>0 then ?D is 1
? If dv is Neg. and dp/dv<0 then ?D is -0.2
? If dv is Pos. and dp/dv>0 then ?D is 0.1
? If dv is Pos. and dp/dv<0 then ?D is -0.8
The duty ratio change (?D) is added to the PWM generator's
(3) input, which consists of an integral and comparator with a
(4) saw tooth wave as a reference voltage.
The power declines over time, with the most power
accessible at lower temperatures, as seen in (Beriber and
Talha, 2013 [35]). Furthermore, according to (Younis et al.
2012 [36]), when a PV panel is directly connected to a load,
the load impedance defines the PV module's operating state,
and only the optimal load allows the PV module to collect
the maximum power. Lodhi et al. 2017 [37] offered a
comparison of the P&O approach with the Incremental
Conductance (IC) method under stable and dynamic weather
conditions. However, as compared to the P&O technique, IC
hardware design is more difficult. While P&O systems are
straightforward, the operating point oscillates about MPP,
resulting in considerable power loss.
In current work, there are two operation modes of the
boost converter to regulate the PV array: maximum power
point tracking (MPPT) and curtailment. In mode 1, a fuzzy
logic based MPPT algorithm calculates the boost converter
duty cycle to ensure maximum power extraction from the
array for a given solar irradiation. The duty cycle of the boost
converter is adjusted to follow the active power reference in
curtailment mode as shown in Fig.9.
The boost converters' output voltage (DC bus voltage)
is 1000V. A three-level inverter (with a switching frequency
of 2340 Hz) transforms the 1000 V DC to about 500 V AC.
The inverter is regulated by a DC voltage regulator, whose
function it is to keep the DC link voltage at 1000V no matter
how much active power the PV arrays supply. To link the
inverter to the microgrid, an LC power filter can be adopted
in AC side and a 1-MVA 480V/600V three-phase coupling
transformer is utilized (see Fig.1).
Fig.9 control method of PV-connected boost converter
cascaded with inverter for MPPT and power curtailment
modes.