MPPT Testing Setup Options

Owned by Micah Black
Last updated: Oct 31, 2022
3 min read

Input Side Options

For testing MPPTs, we need to put something on the input to provide power to the MPPT. In the final application, this will be a solar panel.

The ideal input is then an real solar panel since it matches the application usage exactly, but there are some drawbacks to using it for testing.

To better understand the characteristics of a solar panel, and especially the equivalent circuit model, PLEASE read the wikipedia page and make sure you understand the Equivalent Circuit Model VERY WELL!

ALSO - if you haven’t heard of this site, its amazing! I really like their interactive view for PV Shading effects. Shading reduces the maximum current, but does not affect the voltage of the string.

Option

Pros

Cons

Option

Pros

Cons

1 - Solar Panel (with real sunlight)

  • Best approximation of the actual system

  • Cannot test whenever you want - need it to be in the summer (testing when cold is not fun), when its sunny (afternoons, when people usually have class).

2 - Solar Panel (with artificial light)

  • Provides a real I-V curve from a solar panel.

  • Can test whenever we want

  • Artificial light does not provide enough illumination for high power test.

  • Requires a lot of space (3m^2) or more for lights, panels, equipment. Cannot keep it setup all the time.

3 - Solar Panel Emulator (power supply with very fancy control algorithms)

  • Very close to the real system

  • Can test whenever we want

4 - Equivalent Circuit (create the circuit with power supply in CC mode, power diodes, and power resistors)

  • Has a real MPP without a sharp ‘knee’ in the I-V curve like a real solar panel

  • Can test whenever we want

  • Wastes energy as heat

  • Requires some research, engineering, time, money, to create

5 - Power Supply in CC with large capacitor

  • Very easy to setup - can test whenever we want

  • Note - capacitor required to remove the switching noise

  • Has a VERY sharp ‘knee’ on the I-V curve which makes tracking the MPP very difficult. The MPPTs will often not operate at the actual MPP.

 

Output Side Options

We need to do something with the power that the MPPTs create or else they’ll just charge up the output capacitor and then do nothing. In the car, we use it to power the high voltage bus. Current from the panels goes to motors or to batteries, depending on the current demand. The important thing to note is that the batteries will make the HV bus look like a constant voltage.

Option

Pros

Cons

Option

Pros

Cons

1 - Battery

  • Most realistic to the actual system

  • Actually doing something with the power (not burning it as heat)

  • Need to be careful with the batteries - Li-ions can be dangerous

  • Hard to test different voltages - need to wait for the battery to charge or discharge

2 - E-Load in CV mode

  • Very easy to simulate different voltage conditions (fully charged battery vs almost empty battery)

  • The control loop inside the E-load may cause weird things to happen with the MPPT algorithm. Generally its pretty good if a large capacitor is on the output of the MPPT though.

3 - Resistive load

  • Very simple operation

  • Not configurable

  • Current and voltage are not independent. Might need to choose a different resistor depending on input conditions.