A NOVEL EFFICIENT STAND-A NOVEL EFFICIENT STAND-ALONE PHOTOVOLTAICALONE PHOTOVOLTAIC

DC VILLAGE ELECTRICITY DC VILLAGE ELECTRICITY SCHEMESCHEME

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 PI Controller

• 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 (Rf1 & Lf1)

♦ Storage Capacitor (C1)

♦ Output filter (Rf2 & Lf2 and C2)

• SPWM controlled MOSFET or IGBT DC/DC dual converter (chopper)

• Loads

Stand-alone photovoltaic DC/DC chopper scheme for village electricity use

Novel Dynamic Error DrivenNovel Dynamic Error DrivenPI ControllerPI Controller

Three regulating loops:

• The motor speed trajectory tracking loop• The The first supplementary photovoltaic current

tracking loop• The second supplementary photovoltaic

reference voltage tracking loop

Dynamic tri-loop error driven Proportional plus Integral control system

• The global error signal (et) comprises

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

The loop weighting factors (γw, γi and γv)

are assigned to minimize the time-weighted excursion index J0

where

• │Re(k)│: Magnitude of the hyper-plane error excursion vector

• N= T0/Tsample

• T0: Largest mechanical time constant (10s)

• Tsample: Sampling time (0.2ms)

Digital Simulation ResultsDigital Simulation Results

• Stand-alone photovoltaic scheme model using the MATLAB/Simulink/SimPowerSystems software

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

Variation of

ambient temperature (Tx)

Variation of

solar irradiation (Sx)

Without / with dynamic controller

Ig vs. time

Vg vs. time

Ig vs. time

Vg vs. time

Without / with dynamic controller

Pg vs. Time

the increase of

Pg vs. time

PV power

The digital simulation results validate the tri-loop dynamic error driven PI Controller, ensures:

• Good speed trajectory tracking with a small overshoot/undershoot and minimum steady state error • Good photovoltaic current tracking• Good photovoltaic reference voltage tracking• 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 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 speed trajectory tracking loop

• The dynamic photovoltaic power tracking loop

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

The loop weighting factors (γw andγp) 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?