Use case

For this use case we would like to calculate the conversion efficiency of an inverter. The PV-system is equipped with 12 PV-modules, that are connected as one string to the inverter we want to analyze.

The conversion efficiency is defined as follows:

\[
Eff=100\% \cdot \frac{\text{AC energy [kWh]}}{\text{DC energy [kWh]}}
\]

We will need to measure both the DC output power and the AC output power. We will setup a PV-Blocks system that will allow for these measurements.

Each PV-Blocks system uses the PV-Base pack. We will start the configuration by adding that.

PV-Base pack

The PV-Base pack is the heart of any PV-Blocks system. It is responsible for computing(PV-LINK), power(PV-PSU) and communications(PV-BASE). Without these 3 DIN-rail components a PV-Blocks system cannot be used.

PV-Blocks to use

AC Output

The first parameter to measure is the AC output of the system. The AC output has to be measured ‘behind’ the inverter.  PV-Blocks supports 1-phase and 3 phase AC networks. In this use case our inverter generates AC power in a single phase. The AC meter will be a B21-112-100 from ABB (accuracy class 1.0). This meter can be directly connected to the PV-MOD-AC PV-Block by means of its digital interface.

ABB AC meter

Configuration

We will add the PV-MOD and PV-KWH-1P electricity meter to the system:

DC Output

The second parameter to measure is the DC output of the PV-string. The DC output will be measured ‘before’ the micro-inverter. To measure this DC output, we will use a  ReRa Solutions PV-MON. The PV-MON is a high precision instrument that can be connected directly to a PV-string (up to 1500V) or between a single PV-Module and the rest of the PV-string. It will measure the current and voltage continuously. The PV-MON has a fixed temperature sensor that can be used to measure the PV temperature, however that is not required for this specific use case.

The PV-MON is connected to the PV-Blocks system using a PV-MOD-DC block. Up to 12 PV-MON’s can be connected to one single PV-MOD-DC

Configuration

We will add the PV-MOD-DC and 1 PV-MON DC meter to the system:

The resulting system to measure the AC/DC conversion efficiency is now ready to install. It has a PV-BASE pack, a PV-MOD-DC, PV-MOD-AC, PV-KWH-1P and a PV-MON.

Web interface

The operator can setup the PV-Blocks system by means of an ethernet connection using any web browser. Setting up the system in completely handled by the internal webserver. The PV-Blocks system runs standalone and does not need any maintenance besides a regular backup. The measured values are stored locally on the internal computer. Depending on the amount of PV-Blocks connected, about 10 years of data can be stored locally. Measured data can be downloaded from the web-interface directly.

Application Programming Interface (API)

The PV-Blocks system is completely open to developers by means of an extensive API. Developers can create their own programs to retrieve the data and analyze it in any possible way. An example python script is included with the system that should help a developer to get started.

PV-Blocks Cloud

You can use the PV-Blocks cloud to off-load all data automatically online. Dashboards (Grafana) can be build directly and shown to any audience. Of course the cloud solution complies to the highest security standards.