Photovoltaic Systems Engineering - Ferdowsi University...

lecture 2

Photovoltaic Systems Engineering

Ali KarimpourAssistant ProfessorAssistant Professor

Ferdowsi University of Mashhad

Reference for this lecture:Photovoltaic Systems Engineering Third Edition CRC

Ali Karimpour Apr 2012

Photovoltaic Systems Engineering Third Edition CRCRoger Messenger, Jerry Ventre

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Lecture 8Lecture 8

PV System Loads and Electronicsy

PV System Loads

System AvailabilitySystem Availability

Introduction

System Electronic C t

Charge ControllersComponents

MPPT circuits


2Inverters

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V-I characteristic of a PV

Ideal LoadIdeal LoadBattery Load

Resistive LoadResistive Load

Battery LoadFan Load

Fan Load


3

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MPPTMPPT


4But How is it possible?

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MPPTMPPT

MPPT: Variable resistorsMPPT: Variable resistors

Is it acceptable to pay more initial cost?


5Is it acceptable to pay for a MPPT?

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MPPTMPPT

AV5.2

10PV LoadR=4 Ω

W25

?WW 6025

?→

240

ConverterA

V4.2

25

A

V

15

240PV Load

R=4 ΩR=10.4 Ω


6

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System Availabilityy y

Downtime reasons in conventional power systems:

Sc in the systemFailure of a generatorOverloadFailure in the turbine…….

Downtime reasons in PV systems:

Loose or corroded connectionsBattery failure Controller failure…….


7And also unpredictable cloud cover Enough battery storage.

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Availability definition

m∑T

mtyAvailabili ∑=

Critical loads: 99% availability


8Noncritical loads: 95% availability

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Critical loads: 99% availability

Noncritical loads: 95% availability


9

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Storage days required for a system

247262.42976.0 min2

min +−= TTDcrit


10

minmincrit

4286.9869.11071.0 min2

min +−= TTDnon

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Price of system availability

B li t l tit d i d 44°Burlington latitude is around 44°

Albuquerque latitude is around 35°


11

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System Electronic Components

Introduction

Charge ControllersSystem Electronic Components

g

i iMPPT circuits

Inverters


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Introduction

Di d ( ll bl )

Power

Diode (uncontrollable)

Power semiconductor

switchesThyristors ( Half control)

Power BJT

Transistors (Full control) Power MOSFETTransistors (Full control)

IGBT

Turn on and off by G or B

BJT: Bipolar Junction Transistor.MOSFET: Metal–Oxide Semiconductor Field-Effect Transistor.


13IGBT: Isolated Gate Bipolar Transistor.

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Transistors (Power BJT)


14

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Transistors (Power BJT)


15

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Transistors (Power MOSFET)


16

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Transistors (Compare BJT and MOSFET)

BJTMOSFET BJTMOSFET

كنترل شونده با ولتاژ-باال ورودي امپدانسكنترل شونده با جريان-ورودي كم امپدانس

باال كليدزنيفركانس متوسط فركانس كليدزني

ولتاژ كمترافت مستقيم هدايتهدايت ولتاژ بيشترمستقيمافت بيشترمستقيمافت ولتاژ هدايتهدايت مستقيم كمترافت ولتاژ

بيشتر نويزپذيريكمتر نويزپذيري

كنترل راحت تركنترل مشكل تر

هاي پايين تر موجود استدر قدرتقدرت هاي باالتر موجود استدر

مثبتحرارتيضريبمنفيضريب حرارتي


17

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Transistors (IGBT)

)تلفات هدايت کم(يعني افت ولتاژ مستقيم کوچکBJTدر خروجي داراي مزاياي ي ي ز ي ر روجي وچJر يم ژ و ي م(ي )ييعني جريان ناچيز و سادگي مدار گيت MOSFETدر ورودي داراي مزاياي يضريب حرارتي مثبت

موازي شدن سادگي

MOSFETو BJTسرعت کليدزني بين طگ در قدرت هاي متوسط و باالBJTجايگزين


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Losses in Transistors


19

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Charge controllers

SOC (state of charge) can be measured by VB

Is VB available in charging condition?

Can one estimate VB by knowing RB?

Both V and R are temperature dependent


20

Both VB and RB are temperature dependent. RB is age dependent too.

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Charge Controllers

Let V=14 (C/20)

DisconnectDisconnect

V decreasesV decreases

Connect

V increases


21

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Charge Controllers

Hysteresis can help and solve the problem.

In the charging period:

In the discharging period:In the discharging period:


22

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Charge Controllers

Three stage battery charge control


23

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MPPT circuits

One must A Amax this is possible by an electronic circuit.

V must decrease and I must increase


24Use a buck convertor (Linear Current Booster)

Vp must decrease and Ip must increase.

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MPPT circuits

A buck convertor (Linear Current Booster)


25MOSFET ofcycleduty is where,/, DDIIDVV inoutinout ==

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MPPT circuits

A boost convertor

1


26MOSFET ofcycleduty is where,)1(,

11 DIDIVD

V inoutinout −=−

=

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MPPT circuits

A buck-boost convertor

MOSFETofcycleduty iswhere,)1(, DIDIVDV inoutinout−

==


27

yy,,1 DD inoutinout −

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Inverters

Square Wave Inverters

Different type Of Inverters Modified Sine Wave Inverters

Pulse Width Modulated Inverters


28

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Square Wave Inverters

Conventional Inverter (Square wave inverters)

Harmonics?


29

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Modified Square Wave Inverters

Modified square wave inverters

Harmonics?


30

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Modified Square Wave Inverters

Multi Level Converters

Harmonics?


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Harmonics?

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PWM Inverters

Unipolar SPWM, ma = 0.8 :p , a


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PWM Inverters

Basis of PWM is shifting harmonic frequency and filtering them.


33

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PWM Inverters

Basis of PWM is shifting harmonic frequency and filtering them.


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PWM Inverters


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Photovoltaic Systems Engineering - Ferdowsi University...

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