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Technical Note: TN0071 - Rev 04


Introduction
This technical note shows how one SP PRO inverter can be configured into a Solar Hybrid system to allow parallel insertion of the battery energy into the power system.

The advantages of this configuration are:

  • Allows energy storage to be added to any PV solar grid system, up to 1000A per phase.

  • Provides backup of either critical loads within the system or of the entire system as required.

  • Allows for the installation of a suitable amount of PV solar (either Generic or Managed AC

    coupled) that will remain connected to the system during backup.

  • Power Flow control at the point of connection.


System Overview

Read this Technical Note in conjunction with TN0057 - SP PRO External AC Source Contactor Option available here. 

The system is configured the same as an external contactor according to TN0057 with the exception that the main loads within the installation do not flow through the external contactor.

The External CT is wired back to the connection point to allow the SP PRO to measure and control all the energy flows within the system.

When the grid fails, the external contactor opens and the SP PRO runs the backup loads from the battery bank and any grid inverters that are connected to the backup circuit.

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Fig 1: Basic configuration single line diagram



SP PRO Configuration

Configure the SP PRO and carry out the testing as per TN0057. The system will operate the same as specified in TN0057 with the exemption that the main AC loads will not be backed up and power will be lost to these circuits when the grid fails.

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The following needs to be considered during system design and installation:

  • The grid inverter(s) connected to the grid side of the AC source contactor (Grid Inverters off during backup) can be any grid inverter or combinations of grid inverters.
  • The External Current Transformer (CT) must be rated for the maximum total load current (backup AC load current plus Main AC load current plus SP PRO maximum ac charge current.) and the maximum export current from ALL connected PV inverters.
  • The AC source contactor must be rated for the maximum total backup load current (backup AC load current plus SP PRO maximum ac charge current.) and the maximum export current from all the backup connected PV inverters.

If the system has grid inverters connected to the load side of the system (Grid Inverters on during backup) then install these according to one of the following Installation notes:

  • Generic AC coupled solar: TB0006_xx SP PRO Generic AC Coupling.

  • Selectronic Managed AC coupled Solar: IN0049_xx 005273 Installing a Fronius SCERT in a Managed AC Coupled system Installation Notes OR IN0053_xx 005312 SP PRO ABB UNO Managed AC Coupling Installation Notes.


System Operation

Net Export from the PV
The PV inverters are connected downstream of the SP PRO inverter. When the excess PV generated (net of the load power) is greater than the Grid Export limit setting of SP PRO then SP PRO will use this excess power to charge the battery bank.

Net Power from the Grid
When the load power is in excess of the generated PV, and the excess load power is greater than the Grid Input Limit setting of SP PRO, then SP PRO will start to support the load.

Grid Failure
When the Grid fails, the external contactor will open and the SP PRO will run in stand-alone mode and continue to run the Backed-up AC loads from the battery bank. The PV inverters that are wired into the backup load circuit (Grid Inverters on during backup) will stay connected and run the loads and/or charge the battery bank as required during a grid outage.


Additional Information
Visit the Selectronic: Knowledge Base or contact Selectronic via Customer Portal