Chapter 4 Solar Energy ppsx

Chapter 4

Solar Energy II

4.1 Introduction

In this chapter, we will discuss a more accurate equivalent circuit for a PV cell. This

circuit helps us to have better prediction and understanding of PV cell current-voltage

characteristics as well as at different types of load connected to the PV panel, which is

made up of an array of PV cells. Later in this chapter we will discuss the concept of

maximum power point tracker (MPPT).

4.2 More Accurate Equivalent Circuit for a PV Cell

If we connect two simple PV cell model as described in Fig. 3.7 in series and simulate

the situation when one of the PV cell is shaded while the other is under strong sun

rays, the current source is essentially of zero current. However, in the real PV panel

with PV cells connected in series , such as the BP SX10 with 36 PV cells connected in

series, measurable current is recorded when some of the cells are shaded. This implies

that the simple PV cell is insufficient to model the PV panel I-V characteristics. We

need some path to be added to the model to show the current flow within the PV cells.

Fig. 4.1 shows a more accurate PV cell equivalent circuit using one parallel resistor,

Rp, and one series resistor, Rs, to realize the extra current paths. Let us first derive a

mathematical expression for this equivalent circuit. By KCL, the current enters node

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