1. A NOVEL MAXIMUM POWER TRACKING CONTROLLER FOR A STAND-ALONE PHOTOVOLTAIC DC MOTOR DRIVE A.M. Sharaf, SM IEEE, and Liang Yang Department of Electrical and Computer Engineering University of New Brunswick

2. PRESENTATION OUTLINE Introduction System Model Description Novel Dynamic Error Driven Self Adjusting Controller (SAC) Digital Simulation Results Conclusions Future Work

3. 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/W peak ) Almost has no environmental polluting impact Modular and flexible in terms of size, ratings and applications

4. 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)

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

6. The performance of any stand-alone PV system depends on: Electric load operating conditions/Excursions/ Switching Ambient/junction temperature (T x ) Solar insolation/irradiation variations (S x )

7. System Model Description Key components: PV array module model Power conditioning filter: ♦ Blocking Diode ♦ Input filter (R f & L f ) Storage Capacitor (C 1 ) Four-Quadrant PWM converter feeding the PMDC (Permanent Magnet Direct Current) motor (1-15kW size)

8. Photovoltaic powered Four-Quadrant PWM converter PMDC motor drive system

9. Novel Dynamic Error Driven Self Adjusting Controller (SAC) Three regulating loops: The motor reference speed (ω m -reference) trajectory tracking loop The first supplementary motor current (I m ) limiting loop The second supplementary maximum photovoltaic power (P g ) tracking loop

10. Dynamic tri-loop self adjusting control (SAC) system

11. The global error signal (e t ) comprises 3-dimensional excursion vectors (e w, e i, e p ) The control modulation ΔV c is β is the specified squashing order (2~3) │Re│ is the magnitude of the hyper-plane error excursion vector at time instant k

12. The loop weighting factors ( γ w, γ I and γ p ) and the parameters k 0 and β are assigned to minimize the time-weighted excursion index J 0 where N= T 0 /T sample T 0 : Largest mechanical time constant (10s) T sample : Sampling time (0.2ms) t(k)=k·T sample : Time at step k in seconds

13. Digital Simulation Results Photovoltaic powered Four-Quadrant PWM converter PMDC motor drive system model using the MATLAB/Simulink/SimPowerSystems software

14. Test Variations of ambient temperature and solar irradiation Variation of ambient temperature (T x ) Variation of solar irradiation (S x )

15. For trapezoidal reference speed trajectory I g vs. time P g vs. time V g vs. time V g vs. I g

16. For trapezoidal reference speed trajectory (Continue) P g vs. I g & V g ω ref & ω m vs. time I am vs. time ω m vs. T e

17. For sinusoidal reference speed trajectory I g vs. time P g vs. time V g vs. time V g vs. I g

18. For sinusoidal reference speed trajectory (Continue) P g vs. I g & V g ω ref & ω m vs. time I am vs. time ω m vs. T e

19. The digital simulation results validate the tri-loop dynamic error driven Self Adjusting Controller (SAC), ensures: Good reference speed trajectory tracking with a small overshoot/undershoot and minimum steady state error The motor inrush current I m is kept to a specified limited value Maximum PV solar power/energy tracking near knee point operation can be also achieved

20. 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.

21. Future Work Other PV-DC, PV-AC and Hybrid PV/Wind energy utilization schemes New control strategies

22. Future Work (Continue) Novel Dynamic Error Driven Sliding Mode Controller (SMC) Three regulating loops: The motor reference speed (ω m -reference) trajectory tracking loop The first supplementary motor current (I m ) limiting loop The second supplementary maximum photovoltaic power (P g ) tracking loop

23. Dynamic tri-loop error-driven Sliding Mode Control (SMC) system

24. The loop weighting factors ( γ w, γ i and γ p ) and the parameters C 0 and C 1 are assigned to minimize the time-weighted excursion index J 0 where N= T 0 /T sample T 0 : Largest mechanical time constant (10s) T sample : Sampling time (0.2ms)