A NOVEL TRACKING CONTROLLER FOR A STANDALONE PHOTOVOLTAIC PVDC SCHEME

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A NOVEL TRACKING CONTROLLERFOR A STAND-ALONE
PHOTOVOLTAIC (PV-DC) SCHEME

• A.M. Sharaf, SM IEEE, and Liang Yang
• Department of Electrical and Computer Engineering
• University of New Brunswick

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PRESENTATION OUTLINE

• Introduction
• System Model Description
• Novel Dynamic Error Driven PI Controller
• Digital Simulation Results
• Conclusions
• Future Work

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Introduction

• The advantages of PV solar energy
• Clean and green energy source that can reduce
  green house gases
• Highly reliable and needs minimal maintenance
• Costs little to build and operate (2-3/Wpeak)
• Almost has no environmental polluting impact
• Modular and flexible in terms of size, ratings
  and applications

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Maximum Power Point Tracking (MPPT)

• The photovoltaic system displays an inherently
  nonlinear current-voltage (I-V) relationship,
  requiring an online search and identification of
  the optimal maximum power operating point.
• MPPT controller/interface is a power electronic
  DC/DC converter or DC/AC inverter system inserted
  between the PV array and its electric load to
  achieve the optimum characteristic matching
• PV array is able to deliver maximum available
  solar power that is also necessary to maximize
  the photovoltaic energy utilization in
  stand-alone energy utilization systems (water
  pumping, ventilation)

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• I-V and P-V characteristics of a typical PV array
  at a fixed
• ambient temperature and solar irradiation
  condition

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• The performance of any stand-alone
• PV system depends on
• Electric load operating conditions/Excursions/
  Switching
• Ambient/junction temperature (Tx)
• Solar insolation/irradiation variations (Sx)

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System Model Description

• Key components
• PV array module model
• Power conditioning filter
• ? Blocking Diode
• ? Input filter (Rf Lf)
• Storage Capacitor (C1)
• Four-Quadrant PWM converter feeding the
• PMDC (Permanent Magnet Direct Current)
• motor (1-15kW size)

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• Photovoltaic powered Four-Quadrant PWM converter
  PMDC motor drive system

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Novel Dynamic Error DrivenPI Controller

• Three regulating loops
• The motor reference speed (?m-Reference)
• trajectory tracking loop
• The first supplementary motor current (Iam)
• limiting loop
• The second supplementary
• maximum photovoltaic power (Pg) tracking loop

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• Dynamic tri-loop error driven
• Proportional plus Integral control system

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• The global error signal (et) comprises
• 3-dimensional excursion vectors (ew, ei, ep)
• The loop weighting factors (?w, ? i and ? p) and
  gains (Kp, Ki) are assigned to minimize the
  time-weighted excursion index J0

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• where
• is the total excursion error,
• N T0/Tsample,
• T0 Largest mechanical time constant (10s),
• Tsample Sampling time (0.2ms)

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Digital Simulation Results

• Photovoltaic powered Four-Quadrant PWM converter
  PMDC motor drive system model using the
  MATLAB/Simulink/SimPowerSystems software

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Test Variations of ambient temperature and solar
irradiation

• Variation of
• ambient temperature (Tx)

• Variation of
• solar irradiation (Sx)

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For trapezoidal reference speed trajectory

• ?ref ?m vs. time

• ?m vs. Te

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For trapezoidal reference speed trajectory
(Continue)

• Iam vs. time

• Pg vs. time

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For trapezoidal reference speed
trajectory(Continue)

• Vg vs. Ig

• Pg vs. Ig Vg

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For sinusoidal reference speed trajectory

• ?ref ?m vs. time

• ?m vs. Te

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For sinusoidal reference speed
trajectory(Continue)

• Iam vs. time

• Pg vs. time

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For sinusoidal reference speed
trajectory(Continue)

• Vg vs. Ig

• Pg vs. Ig Vg

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• The digital simulation results validate
• the tri-loop dynamic error driven
• PI controller, ensures
• Good reference speed trajectory tracking with
• a small overshoot/undershoot and minimum
• steady state error
• The motor inrush current Iam is kept to a
  specified
• limited value
• Maximum PV solar power/energy tracking near
• knee point operation can be also achieved

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Conclusions

• The proposed dynamic error driven controller
  requires only the PV array output voltage and
  current signals and the DC motor speed and
  current signals that can be easily measured.
• The low cost stand-alone photovoltaic renewable
  energy scheme is suitable for village electricity
  application in the range of (150 watts to 15000
  watts), mostly for water pumping and irrigation
  use in arid developing countries.

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Future Work

• Other PV-DC, PV-AC and Hybrid
• PV/Wind energy utilization schemes
• New control strategies