The following circuit diagram shows the circuit that has been used. Moving from left to right, we can recognize the various elements of the circuit. The current source, Ipv, the forward-biased diode Dpv, and the shunt and series resistors Rsh and Rs together represent the PV panel. The value of Ipv is proportional to the incident light radiation. Diode characteristics are chosen to reasonably approximate the I-V characteristic of the panel.
Shunt resistance is ignored, and a fairly small value is chosen for the series resistance.
To the right of this is a circuit that represents the motor. Ra represents the series resistance of the motor, and below that is a voltage source, Vb , which represents the back-emf of the motor. This is a controlled voltage source, to be described better later. In parallel with this voltage source is a controlled current source Ifr which represents the current required to overcome the frictional torque of the motor. To the right of this is the circuit that represents the mechanical system.