Use Case: Control charge and discharge of multiple batteries in an installation with GEN24 Plus inverters

Prerequisites: What you should know before approaching this use case:

• Have a basic understanding of SwitchDin’s Droplet installation and commissioning principles. 
• Know how to wire an inverter to a droplet using a USB/ETH adaptor.
• Know how to set up Modbus communication protocol on an inverter.
  
  

Installation overview: The installation will typically involve Primo Hybrid GEN 24 1-Phase inverter or Symo Hybrid GEN24 3-phase inverter. In this use case we explain how to install and commission the Droplet in conjunction with the GEN24 Fronius Inverters.

Our example includes a residential solar system that has 2 Primo Gen24 inverters, 2 BYD batteries and 1 grid meter. One of these inverters will have to be connected to a Fronius Smart meter which is placed in the “feed-in” position (i.e. it's a grid meter). Both inverters will be connected to BYD batteries.

Daisy chaining Fronius GEN 24 inverters is not possible. Therefore, both inverters need to be connected to a router that will communicate with our droplet. Either WIFI or Ethernet connection can be used between inverters and the customer router.

Connection overview

Before commissioning the droplet, ensure that batteries and grid meter are serially connected to the inverters. If not done that way, battery State of Charge metric from the inverters may not be detected and to resolve this, all assets will need to be re-configured.

here are the next steps:

Step 1: Connect the droplet to the customer router. Preferably using an Ethernet connection between the droplet and the customer router, or, wirelessly connect the droplet to the router.

Step 2: Now inverters need to be wirelessly connected to the router. This can be achieved via the settings panel on Solar Web (Fronius Web Application). Note that inverters can be connected to a droplet using a USB-Ethernet converter if the Droplet has a connection to the router.

Step 3: That’s it! Download SwitchDin app and start your standard commissioning.

Because the meter and batteries are all serially connected to the inverters, once an internet connection is established between the inverters and the router, the meter should automatically become visible in the equipment section of your SwitchDin application. SwitchDin will not ‘discover’ the batteries and list them in the equipment tab but rather show a state of charge value and a charge / discharge value upon successful connection of inverter.

Step 4: Add the multi-battery self-consumption controller

Once both inverters and the meter are discovered you should see one of the inverters working in conjunction with the battery and the other inverter not working with the battery. This is due to there being no connection to a meter on the second inverter. Fronius GEN24 inverters appear to fall-back to a stand-by state when there is not grid meter connected. Thus you will need to add the multi-battery self-consumption controller which will aggregate all values between the 2 inverters and link inverter number 2 to the meter connected to inverter number 1 so that it works with the battery. The State of charge will now be an average of both batteries state of charge.

What can you directly control on this installation as an installer?

There is no need to manually control charge/discharge of the batteries.

However an override control is accessible from the equipment tab of your SwitchDin application when clicking on each inverter. It allows to state a charge or discharge value setpoint. This will override all controls and prioritise meeting that setpoint. So, for example, to forcefully charge/discharge batteries, set both inverters to (depending on the max charge rate of the batteries which can change) 5/-5.

Other configurations:

What if multiple meters are used on site? Any additional meter will need to be set as “duplicate” in the meter role section.

What if a Droplet PLUS is used? Here are options if you use this C&I grade droplet version.

What can be controlled at VPP level with SwitchDin?

• Connecting your fleet of devices to a VPP enhances monitoring and provides telemetry data which can allow for dispatch planning and response validation.
• Battery setpoint control can be managed by a VPP operator to perform wholesale market arbitrage, price risk management and utilise dynamic operating envelope (Tariff must be setup from the app).
• Setting site export limits (used by network services providers) can be used for Demand Response, load side management and peak shaving.
• Capacity to participate into the FCAS market (frequency support market)