EMR'11 Summer School, July 4-6, 2011 EPF Lausanne (Switzerland)

Simulation of the Photovoltaic Panel

Objective – The aim of this simulation session is to realize a control using a Maximum Power Point Tracking (MPPT) strategy for a photovoltaic system to charge the batteries. Working steps – This simulation session is divided into seven steps: – Entering the equation for the studied system; – Building the EMR of the studied system; – Implementing the EMR into MATLAB-SimulinkTM software; – Analyzing and testing; – – –

first day

Step-by-step realization of the inversion-based control; Implementation of the inversion-based control from EMR into Simulink; Analyzing the performances.

second day

The available materials at your disposal are: – The structural scheme of the studied system; – The associated parameters; – The voltage/current characteristics of the photovoltaic panels entered into Simulink. Description of the studied system – The studied system is composed of solar panels, a DC bus, a single phase filter and a boost converter (Fig. 1). solar panels

filter

iL

batteries

ibc

L

ipv uC DC bus

ubc

ubat

boost converter

Fig. 1. Structural scheme of the studied photovoltaic system

Photovoltaic panels – 6 Solarex MSX-83 solar panels (cf. appendix 1) are connected in parallel to represent the solar generator. The non-linear electrical characteristics of a panel are shown in the Fig. 2 and Fig. 3. I (A)

I (A) G = 1000 W/m2

1

T = 75°C

G = 800 W/m2

T = 50°C

G = 600 W/m2

T = 25°C

G = 400 W/m2

T = 0°C

G = 200 W/m2 V (V)

V (V)

Fig. 2. Characteristic I=f(V) of a panel MSX-83 [1] in function of the temperature for a solar irradiance1 of 1 kW/m2

Fig. 3. Characteristic I=f(V) of a panel MSX-83 [1] in function of the solar irradiance for a panel temperature of 25°C

The solar irradiance corresponds to the solar radiation power by surface unit. 1/5

DC bus and filter – The MPPT strategy is commonly used (cf. appendix 2) for the efficient usage of solar cells. The objective of this strategy is to extract the maximum power points of the solar generator (Fig. 4 and Fig. 5). A solar panel is a passive component that generates a DC current. Thanks to the boost converter, the voltage and power of the panels can be controlled easily. For this reason a DC bus is required. The inductor is used to filter the harmonics generated by the boost converter. The characteristics of the DC bus and the filter are the following: – Capacity of the DC bus: 200 µF; – Leakage resistance of the DC bus: 50 kΩ; – Inductance of the filter: 10 mH; – Series resistance of the filter: 25 mΩ. P (W)

P (W) MPPT

T = 0°C

MPPT

G = 1000 W/m2 T = 25°C

G = 800 W/m2 G = 600 W/m2

T = 50°C

G = 400 W/m2 G = 200 W/m2

T = 75°C V (V)

V (V)

Fig. 4. Characteristic P=f(V) of a panel MSX-83 [1] in function of the temperature for a solar irradiance of 1 kW/m2

Fig. 5. Characteristic P=f(V) of a panel MSX-83 [1] in function of the solar irradiance for a panel temperature of 25°C

Converter – The boost converter is considered with a constant efficiency of 90 %. Its modeling will be made in mean value. Batteries – The batteries are considered as ideals with a constant voltage of 40 V.

References [1]

Christian GLAIZE, « Caractéristiques d’un panneau photovoltaïque, recherche du point de puissance maximale, intérêt d’un convertisseur », data of the solar panel MSX-83 available on the website (reference of June 2011): http://www.geea.org/

2/5

Appendix 1 – Photovoltaic module MSX-83 (www.solarex.com)

3/5

4/5

Appendix 2 – MPPT Strategy: Perturb and Observe The Fig. 4 and Fig. 5 shows the generated power of the panels strongly depend on the temperature and the solar irradiance. The MPPT (Maximum Power Point Tracking) strategy is commonly used to extract the maximum power of the photovoltaic panels. Different strategies exist. The most known and the simplest is called “Perturb and Observe” (P&O). This strategy consists to vary the voltage of the panels around its initial value and to notice the power variation which results from it. If a positive increase of voltage leads to a power increase this means the obtained operating point is on the left of its Maximum Power Point (MPP, Fig. 6). If, otherwise, a positive increase of voltage leads to a power decrease then the operating point is on the right of the PPM. The Fig. 7 shows the classical algorithm to use to realize this MPPT strategy.

MPP PMPP

The system coves near of MPP

The system moves away from MPP

VMPP Fig. 6. Characteristic PPV=f(VPV) of a photovoltaic panel

Measurement of

Calculation of PPVn

YES

NO

YES

Decrementation of Vref

YES

NO

NO

Incrementation of Vref

Decrementation of Vref

YES

Incrementation of Vref

Fig. 7. Classical algorithm of the strategy MPPT P&O The figures of this page are from: C. Cabal, « Optimisation énergétique de l’étage d’adaptation électronique dédié à la conversion photovoltaïque », décembre 2008, Thèse de Doctorat de l’Université de Toulouse III – Paul Sabatier.

5/5