Practical experiments
In this chapter, experimental tests will be carried out to investigate the properties of the solar module optimizer and compare the performance of the implemented algorithms. Various measurements are performed and the results are evaluated to analyze the operation and properties of the optimizer. The chapter is divided into two main sections. In the first section, the basic operation of the solar module optimizer is reviewed, while in the second section a comparison of the algorithms is performed. The aim is to show the advantages and disadvantages of the different algorithms in order to identify the optimal method for the application of the solar module optimizer. For the experiments, an ohmic heating mat with a resistance of $R_{L}=24\Omega$ is connected to the output of the module optimizer.
Basic PV emulator
In order to keep the experiments comparable and to always have the same laboratory conditions, no experimental trial with a PV-module under environmental conditions is performed, instead a PV emulator based on the principles of the paper Simple and Fast Dynamic Photovoltaic Emulator based on a Physical Equivalent PV-cell Model by Khawaldeh et al. is used. The emulator is based on the single-diode equivalent circuit of a PV-module, here a current source and a series connection of power diodes are connected together in the flux direction, and a series and a parallel resistor are also added, as shown in Basic PV emulator. The number of diodes, the maximum current of the source and the resistor values can be varied to change the characteristic.
Shaded PV emulator
For this experimental setup, power devices designed for higher heat generation are used, such as the power diode P600D with a number of $N=30$ as well as a parallel resistance of $R_{p}=220 \Omega$ and a series resistance of $R_{s}= 0.4 \Omega$, and active air cooling is also required.
Another experiment is to record a VI-characteristic curve from a solar module under partial shading, but for this the PV emulator must be wired slightly differently. The partial shading is emulated with an additional lower current source, which affects only a small part of the series connection from the diodes. Both current sources are wired according to pv emulator shaded. Also, two bypass diodes must be added to allow current to flow through the circuit even if some diodes become shaded. The same diodes are used for this as for the series connection. The PV emulator should now exhibit very similar behavior to a standard solar module that is one-third shaded, with an open circuit voltage $V_{oc}=21V$, the short circuit current of $I_{sc}=5A$, and two bypass diodes.
PV emulator picture
