A Simple and Efficient MPPT Scheme for PV Module ...

A Simple and Efficient MPPT Scheme for PV Module Using 2-Dimensional Lookup Table By

Venkata Reddy Kota Jawaharlal Nehru Technological University Kakinada Kakinada, Andhra Pradesh, India, www.jntuk.edu.in

01-May-16

1

Mathematical Modeling of PV module:

Fig. 1: Electrical Equivalent Circuit of a PV Module

From Kirchhoff’s Current law, current (I) of the PV module can be expressed as

I  I ph  I d  I sh

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(1)

2

Mathematical Modeling of PV module Contd… : Using Shockley equation, equation (1) can be rewritten as

  q(V  IRs )   V  IRs   1  I  I ph  I O exp  Rsh  N s AKT   

(2)

The photo generated current Iph is given as a function of irradiance and temperature on the device surface as

I ph  ( I sc,r

G  K I (T  298)) 1000

(3)

The diode saturation current is expressed in terms of temperature as 3  qE g  1 1  T   I O  I rsc     exp    298   AK  298 T 

(4)

where the reverse saturation current Irsc is given by

I rsc 

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I sc,r   qVoc exp   N s KAT 

    1  

(5)

3

Parameters of PV system:

Table 1: PV module (KC200GT) parameters at STC

Imp Vmp Pmax Isc=Ipv Voc Io Rs Rsh

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7.61A 26.3V 200.143W 8.21A 32.9V 9.825*10-8A 415.405Ω 0.221Ω

Table 2: Boost Converter parameters Filter Capacitor Filter Inductor DC bus capacitor Switching Frequency Switching Element R-Load

2mF 10mH 800μF 1kHz MOSFET 100Ω

4

Characteristics of PV module : 250 1200W/m2 200

Power(W)

1000W/m2 150

800W/m2

100 50 0

600W/m2

20 30 Voltage(V) Fig.2: PV curve at a 30°C temperature with different Irradiance

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0

10

5

Characteristics of PV module Contd… : 10 1200W/m2

Current (A)

8

1000W/m2

6

800W/m2

4 600W/m2

2 0

0

10

20 Voltage (V)

30

40

Fig.3: IV curve at a 30°C temperature with different Irradiances

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6

Characteristics of PV module Contd… : 250 25°C

Power (W)

200 150

30°C

100

35°C

50 0

40°C 0

5

10

15

20

25

30

35

Voltage (V) Fig.4: PV curve at 1000 W/m2 Irradiance with different temperatures

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7

Characteristics of PV module Contd… :

10

Current (A)

25°C 30°C

5 35°C

0

40°C 0

5

10

15

20

25

30

35

Voltage (V) Fig.5: IV curve at 1000 W/m2 Irradiance with different temperatures

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8

Different MPPT schemes: • • • • • • • • • • • 01-May-16

Perturb & Observe Hill Climbing method Incremental Conductance method Constant Voltage / current method Fixed duty cycle method Beta method Parasitic capacitor / dc- link capacitor droop control dP/dV or dP / dI feedback control Fuzzy logic controller Artificial Neural Networks Genetic Algorithm 9

Perturb and Observe MPPT Scheme: Flowchart: Advantages: Low cost  Implemented using analog and digital circuits.  Computation process doesn’t depend on weather conditions.

Disadvantages: Low efficiency  Slow Tracking  Confuses operating point (MPP)  Oscillations (wastage of Power)  Neglects change in irradiance and temperature.

Fig.6: Flowchart of P&O scheme 01-May-16

10

Proposed 2-Dimentional Lookup table based MPPT Scheme: Main Features:  The MPPT voltages of KC200GT PV module are calculated for different irradiance and temperature levels.  The pre-calculated MPV values stored in a 2-dimentional lookup table shown in Table 3  Using extrapolation and interpolation technique MPV values can be calculated for any irradiance and temperature values other than pre-stored values. Table 3: Maximum Power Voltages at different irradiances and temperatures

t ᵒC

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16 20 24 28 32 36 40

400 26.86 26.24 25.84 25.31 24.78 24.45 23.99

500 26.93 26.43 26.43 25.61 25.11 24.72 24.19

600 27.26 26.63 26.3 25.94 25.51 24.95 24.55

700 27.36 26.96 26.47 26 25.54 25.05 24.65

Irradiance, W/m2 800 900 1000 27.42 27.32 27.26 26.9 27.03 27.09 26.5 26.57 26.6 26.14 26.1 26.2 25.57 25.64 25.71 25.21 25.18 25.34 24.78 24.62 24.72

1100 27.29 26.96 26.7 26.07 25.71 25.31 24.85

1200 27.52 27.09 26.63 26.17 25.67 25.34 24.88

1300 27.39 26.99 26.57 26.24 25.71 25.34 24.82

1400 27.29 26.93 26.53 26.04 25.67 25.25 24.78

11

Three-Dimensional view of Lookup table data:

28

Voltage(V)

27 26 25 24 23 1500 1200 900 600 300 Irradiance W/m²

0

15

21 17 19

23

29 25 27

31

temperature

37 33 35

3940

C

Fig. 7: 3-D view of a 2-Dimensional Lookup table data 01-May-16

12

Matlab/Simulink Implementation of the Proposed Scheme: i + -

1000

C in

v -

Mosfet

Vpv

irradiance

G

25

T

C

R-load

S

-

s

CCS

Diode

g

+

V

Temperature

Lin

D

+

Ipv

I

PV Panel

PI(z)

Lookup Table (2-D)

Add4