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AC-coupled connection with Solis: The operation and application of the Smart Port

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The demand for battery storage is growing rapidly, also for installations that were installed years ago. In practice, installers are increasingly encountering existing PV systems where the customer wants to expand without replacing everything. AC coupling with a Solis hybrid inverter offers a smart and practical solution, especially in combination with the Smart Port.

Instead of making adjustments on the DC side, AC coupling operates via the alternating current side. The existing PV inverter remains in operation and is effectively placed “behind” the hybrid inverter. This allows storage to be added without major modifications to the existing installation.

What does the installation look like?

In practice, the existing PV inverter remains completely intact, regardless of whether it is a string inverter, optimizer system, or microinverters. A Solis hybrid inverter is added and connected to the rest of the system. The setup is as follows:

  • The existing PV inverter remains connected as it is
  • The AC cable of this inverter is connected to the Smart Port of the Solis

  • The Solis hybrid inverter is connected to:

    • a battery
    • an energy meter (via signal cable)
    • optionally additional PV modules via the PV DC inputs

In this setup, the Smart Port functions as a PV generator port.

What happens to the energy?

The existing PV inverter supplies its energy to the internal AC network of the installation. The hybrid inverter continuously determines what happens to this energy. In practice, this means the energy is used for:

  • direct consumption in the building
  • charging the battery (AC to DC)
  • feeding back to the grid, if permitted

When the battery is full and, for example, a zero-export setting is active, the hybrid inverter intervenes automatically. This is done via frequency control on the Smart Port. By increasing the frequency, the existing PV inverter is curtailed. This process is known as PV limiting and prevents unwanted feed-in.

The Smart Port in practice

The Smart Port is a multifunctional AC connection and plays a central role in this solution. Depending on the configuration, this port can be used in three ways:

  • Generator port For automatically starting and stopping a generator at low battery status
  • Additional backup port For supplying non-critical loads such as a boiler, EV charger or air conditioning, depending on the battery status
  • PV generator port for grid-tied inverter For connecting an existing PV installation, as described in this article

This flexibility makes the system widely applicable in various situations.

Advantages for installers

In practice, the main advantages lie in the simplicity and flexibility of this solution. Existing installations can be upgraded without major modifications.

The key advantages at a glance:

  • Add battery storage without replacing the existing PV inverter
  • No modifications required to the AC circuit or distribution board*
  • Reduced installation time and lower costs
  • Option to fully switch to the hybrid inverter at a later stage
  • Additional commercial opportunities with existing customers
  • No system responsibility for the existing grid-tied inverter and PV modules
  • In the event of a grid outage, the backup loads can also use solar energy from the existing PV system

Important considerations

Although the installation is relatively straightforward, there are several points to consider:

  • The power of the existing inverter must remain within the limits of the Solis

    • 3-phase: maximum equal to the nominal power of the hybrid inverter
    • 1-phase: maximum approximately 1/3 of the power when connected to a 3-phase inverter with generator port
  • The energy meter must be correctly installed and configured
  • The correct Smart Port function must be selected (AC coupling)
  • Zero export and PV limiting must be correctly configured where applicable

Supported inverters AC coupling via the Smart Port (generator port) is supported on the following models:

  • S6-EH1P(3-10)K-L-PLUS
  • S6-EH3P(8-18)K02-NV-YD-L
  • S6-EH3P(12-20)K-H
  • S6-EH3P(30-50)K-H
  • S6-EH3P(80-125)K10-NV-YD-H

Via the backup port, this is also possible on:

  • S6-EH3P(5-10)K-H-EU
  • S6-EH3P(5-10)K2-H

Why this is interesting in practice

What stands out in discussions with installers is that this solution is often underestimated. Once they become familiar with it, enthusiasm quickly follows. Not only because it is technically interesting, but especially because it offers an accessible way to re-engage existing customers.

In a market where grid congestion and feed-in limitations are increasingly common, AC coupling offers a practical and future-proof solution that installers will use more frequently.

AC coupling via the Smart Port makes it possible to quickly and efficiently expand existing PV systems with storage, without major modifications. For installers, this means less work, more flexibility, and above all, new opportunities in a growing market.

* If the current installation is connected to a PV distribution board, it must be verified whether this is feasible in terms of protection, as an additional load is introduced when the battery needs to be charged from the grid.