ABSTRACT:
A simple and efficient solar photovoltaic (PV) water
pumping system utilizing an induction motor drive (IMD) is presented in this
paper. This solar PV water pumping system comprises of two stages of power
conversion. The first stage extracts the maximum power from a solar PV array by
controlling the duty ratio of a DC-DC boost converter. The DC bus voltage is
maintained by the controlling the motor speed. This regulation helps in
reduction of motor losses because of reduction in motor currents at higher
voltage for same power injection. To control the duty ratio, an incremental
conductance (INC) based maximum power point tracking (MPPT) control technique
is utilized. A scalar controlled voltage source inverter (VSI) serves the
purpose of operating an IMD. The stator frequency reference of IMD is generated
by the proposed control scheme. The proposed system is modeled and its performance
is simulated in detail. The scalar control eliminates the requirement of speed
sensor/encoder. Precisely, the need of motor current sensor is also eliminated.
Moreover, the dynamics are improved by an additional speed feedforward term in
the control scheme. The proposed control scheme makes the system inherently
immune to the pump’s constant variation. The prototype of PV powered IMD
emulating the pump characteristics, is developed in the laboratory to examine the
performance under different operating conditions.
KEYWORDS:
1.
Photovoltaic
cells
2.
MPPT
3.
Water pumping
4.
Scalar control
5.
Induction motor drives
SOFTWARE:
MATLAB/SIMULINK
CONCLUSION:
The
standalone photovoltaic water pumping system with reduced sensor, has been
proposed. It utilizes only three sensors. The reference speed generation for V/f
control scheme has been proposed based on the available power the regulating
the active power at DC bus. The PWM frequency and pump affinity law have been
used to control the speed of an induction motor drive. Its feasibility of
operation has been verified through simulation and experimental validation. Various
performance conditions such as starting, variation in radiation and steady
state have been experimentally verified and found to be satisfactory. The main
contribution of the proposed control scheme is that it is inherently, immune to
the error in estimation of pump’s constant. The system tracks the MPP with
acceptable tolerance even at varying radiation.
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[3]
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[5]
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