A NOVEL MAXIMUM POWER A NOVEL MAXIMUM POWER TRACKING CONTROLLERTRACKING CONTROLLER

FOR A STAND-ALONE FOR A STAND-ALONE PHOTOVOLTAIC DC MOTOR PHOTOVOLTAIC DC MOTOR

DRIVEDRIVE

A.M. Sharaf, SM IEEE, and Liang YangA.M. Sharaf, SM IEEE, and Liang YangDepartment of Electrical and Computer EngineeringDepartment of Electrical and Computer Engineering

University of New BrunswickUniversity of New Brunswick

PRESENTATION OUTLINEPRESENTATION OUTLINE

• Introduction• System Model Description• Novel Dynamic Error Driven Self Adjusting

Controller (SAC)• Digital Simulation Results• Conclusions• Future Work

IntroductionIntroduction

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

Maximum Power Point Tracking Maximum Power Point Tracking (MPPT)(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)

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

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)

System Model DescriptionSystem 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)

Photovoltaic powered Four-Quadrant PWM converter PMDC motor drive system

Novel Dynamic Error Driven Novel Dynamic Error Driven Self Adjusting Controller (SAC)Self Adjusting Controller (SAC) Three regulating loops: • The motor reference speed (ωm-reference)

trajectory tracking loop• The first supplementary motor current (Im) limiting loop • The second supplementary maximum photovoltaic power (Pg) tracking loop

Dynamic tri-loop self adjusting control (SAC) system

• The global error signal (et) comprises

3-dimensional excursion vectors (ew, ei, ep)

• The control modulation ΔVc is

• β is the specified squashing order (2~3) • │Re│ is the magnitude of the hyper-plane error

excursion vector at time instant k

The loop weighting factors (γw, γI and γp) and the parameters k0 and β are assigned to

minimize the time-weighted excursion index J0

where• N= T0/Tsample

• T0: Largest mechanical time constant (10s)• Tsample: Sampling time (0.2ms)• t(k)=k·Tsample: Time at step k in seconds

Digital Simulation ResultsDigital Simulation Results

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

MATLAB/Simulink/SimPowerSystems software

Test Variations of Test Variations of ambient temperature and solar irradiationambient temperature and solar irradiation

Variation ofambient temperature (Tx)

Variation of solar irradiation (Sx)

For trapezoidal reference speed trajectory

Ig vs. time

Pg vs. time

Vg vs. time

Vg vs. Ig

For trapezoidal reference speed trajectory(Continue)

Pg vs. Ig & Vg

ωref & ωm vs. time

Iam vs. time

ωm vs. Te

For sinusoidal reference speed trajectory

Ig vs. time

Pg vs. time

Vg vs. time

Vg vs. Ig

For sinusoidal reference speed trajectory(Continue)

Pg vs. Ig & Vg

ωref & ωm vs. time

Iam vs. time

ωm vs. Te

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 Im is kept to a specified limited value • Maximum PV solar power/energy tracking near knee point operation can be also achieved

ConclusionsConclusions• 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.

Future WorkFuture Work

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

Future Work (Continue)Future Work (Continue)Novel Dynamic Error DrivenNovel Dynamic Error Driven

Sliding Mode Controller (SMC)Sliding Mode Controller (SMC) Three regulating loops: • The motor reference speed (ωm-reference)

trajectory tracking loop• The first supplementary motor current (Im) limiting loop • The second supplementary maximum photovoltaic power (Pg) tracking loop

Dynamic tri-loop error-drivenSliding Mode Control (SMC) system

The loop weighting factors (γw, γi and γp) and the parameters C0 and C1 are assigned to minimize the time-weighted excursion index J0

where• N= T0/Tsample

• T0: Largest mechanical time constant (10s)• Tsample: Sampling time (0.2ms)

Thank You!Thank You!&&

Questions?Questions?