Abstract
In photovoltaic (PV) water pumping systems, a maximum
power point tracking (MPPT) controller is extremely
important. Since PV generators exhibit nonlinear I-V
characteristics and their maximum power point varies with
solar insolation. Therefore, the MPPT controller optimises the
solar energy conversion by ensuring that the PV generator
runs at the maximum power point at all times under different
illumination conditions. In this paper, a new artificial neural
network (ANN) based searching algorithm is proposed for
maximum power point tracking (MPPT). The system is
composed of solar array, buck converter and centrifugal pump
load driven by a permanent magnet DC motor. The proposed
ANN controller uses the output power of the PV generator
and speed of the DC motor as input signals and generates the
pulse width modulation (PWM) control signal to adjust the
operating duty ratio of a buck converter to match the load
impedance to the internal impedance of the PV array; thus
maximizing the motor speed and the water discharge rate of a
centrifugal pump. A complete dynamic simulation of the
system is developed in MATLAB/SIMULINK to demonstrate
the feasibility of the ANN control scheme under different
sunlight insolation levels. The results obtained verify that the
proposed ANN controller shows a significant improvement in
the power extraction performance under different sunlight
conditions, when compared with a directly-connected PVgenerator
energized pumping system. Moreover, the
simulation results match the calculated improvement.
1 Introduction
The standalone photovoltaic (PV) water pumping system has
received increasing attention in the last 20 years because of
the ongoing cost reductions in PV arrays. It is important to
operate the PV energy conversion systems at the MPP or near
to it to increase the efficiency of the PV system. The PV array
has non-linear. The output current and power of the PV array
depends on its operating terminal voltage. Also, the output
power of PV array is fluctuating with the change in the
ambient temperature and solar irradiation. Therefore, for most
of the time under varying irradiation levels the DC motor and
pump are operating the PV array far from the MPP. Due to