A Perturb and Observe Method using Fuzzy Logic
Control for PV pumping system *
Abdourraziq Sarah
EI Bachtiri Rachid
LESSI Lab FSDM, REEPER Group, EST Sidi Mohammed Ben Abdellah University, Fez, Morocco
[email protected]
LESSI Lab FSDM, REEPER Group, EST Sidi Mohammed Ben Abdellah University, Fez, Morocco
[email protected]
Abstract-This paper provides a theoretical study of the P&O maximum power point tracking
(MPPT)
technique, using fuzzy
logic control applied to a standalone PV pumping system.
With
conventional P&O algorithm using fixed iteration step-size, it is impossible to satisfy both performance of fast dynamic response and good accuracy under irradiance and temperature changing. To overcome these limitations a new adaptive P&O method with fuzzy logic control
(FLC)
is presented. The influence of the
proposed method parameters on system behavior is investigated and compared with the traditional P&O method. The studied system consists of a PV panel, a DC-DC boost converter, and a
and modeling of the system, and comparative study between traditional P&O technique and the novel improved P&O method using fuzzy logic control (FLC). The proposed method was tested in MATLAB/SlMULINK environment. The obtained results indicate the feasibility and improved functionality of the system. The studied system consists of the PV array, the DC-DC boost converter, and the DC motor-pump. The block diagram of the PV pumping system proposed is shown in Figure 1.
PMDC motor-pump. To evaluate the proposed method, we use the simulation with Matlab/Simulink and we compare it with the traditional P&O method under different insolation. The obtained results illustrate the effectiveness of the proposed technique.
Keywords-component; maximum power point tracking (MPPT); P&O; fuzzy logic control (FLC); photovoltaic pumping system (PVPS)
I.
PVarray
Figure 1.
INTRODUCTION
A standalone photovoltaic pumping system (PVPS) is one of the most promising application of photovoltaic (PV) systems, specifically in the remote areas, that have an important insulation and have no access to an electric grid. To operate in the maximum power point (MPP) of the PV panel, and improve the efficiency of the system, we use the technique of tracking of the MPP. Several papers has studied a directly connected of the PV array and the motor-pump set for PV pumping system [1], the intersection point of the voltage-current curve and curve of motor-pump can be far from the (MPP) which decrease an important proportion of the available solar power. An adapter DC-DC boost converter controlled by MPPT algorithm can be used between the PV generator and motor-pump. In the literature, a variety MPPT algorithms have been proposed including fractional open circuit voltage [2], fractional short circuit current [3], perturb and observe (P&O) [4]-[5], incremental conductance (INC) [6]-[7], and artificial intelligence-based algorithms [8]-[9]. These algorithms vary in their complexity, efficiency, cost, and potential applications. In this paper, a simple and efficient photovoltaic water pumping system is presented. It provides a theoretical study
DC·DC Boost COIl\-erter
DC motor
pump
General configuration of a photovoltaic pumping system
II.
PY PANEL MODEL
The PV array is a p-n junction semiconductor, which converts light into electricity. In the literature, it exists several mathematical models which describe the I - V characteristics [10]. The equivalent circuit of the PV cell is shown in the following figure:
ip
illph
Figure 2.
Equivalent circuit of PY cell
The behavior of the PV array may be described by equations follows: 1= Iph id ip (1) -
978-1-4799-3824-7/14/$31.00 ©2014 IEEE
-
v:
1
=
.
id =lO(exp( J q )) KO·T V +Rsl . Ip = Rp
With
Vj.q lph- lO(exp( )) KO·T
-
1)
-
(2)
1)
(3)
V +Rsl
(6)
Pen) = V(n)·len) The flowchart of the traditional algorithm P & in Fig. 4.
0
is shown
(4)
---
Rp
Where V is the PV output voltage, I is the PV output current, Iph is the photocurrent, 10 is the saturation current, Rs is the series resistance, Rp is the shunt resistance, and q is the electronic charge, n is the diode factor, Ko is the Boltzmann's constant, T is the junction temperature. The output simulation results of the I-V and P-V curves of the PV cell for different values of radiation are presented in Figure 3 a, b.
P(w) 250 ,-----�-�--�-�___'_':;��-____, 200 150 100
10 I(A)
20
30
50
40
60V(
V)
(a) 6
1000w/m2
5
4
Figure 4. Traditional Perturb & Observe (P&O) Method
700w/m2 3
500w/m2
2
10
20
30
40
(b) Figure 3. Output characteristics of PV array (a) V-P, (b) V-I
III.
TRADITIONAL P&O METHOD
The P&O MPPT method is the most commonly algorithm used for PV systems. However, this method has several drawbacks such as slow tracking speed and oscillations around MPP, making it less favorable for rapidly changing environmental conditions. dP Pen) - Pen -1) (5) (n) dV V(n) - V(n -1) =
The tracker operates periodically by comparing the actual value of the power with the previous value to determine the search direction (incrementing or decrementing) on the solar array voltage or current curve. If the voltage of the PV generator is perturbed in one direction and dP / dV> 0, the algorithm P & 0 could then continue to disrupt the PV voltage in the same direction. If (dP / dV)
