Feed-in management with Fronius Tauro
How to regulate and control PV systems while taking account of feed-in limits and external
control
© Fronius International GmbH
Version 1.0, 02/2021, Peter Schmidhuber, Jasmin Gross
Solar Energy
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CONTENTS
1 Feed-in management with multiple inverters ............................................................................................................... 3
1.1SOLUTION A – Simple power reduction of an individual inverter ............................................................................................. 4
1.1.1 Feed-in limiting according to PV generator output ..................................................................................................................... 4
1.1.2 Feed-in limit according to nominal inverter output ..................................................................................................................... 5
1.1.3 System monitoring with Fronius Solar.web ................................................................................................................................ 5
1.2SOLUTION B – INTEGRATION OF A PLANT CONTROLLER ...................................................................................................... 6
1.2.1 System monitoring with Solar.web ............................................................................................................................................. 6
2 SAMPLE SCENARIOS .................................................................................................................................................... 7
2.1Systems with inverters from the same product family ............................................................................................................... 7
2.1.1 Single Fronius Tauro External control ............................................................................................................................ 7
2.1.2 Single Fronius Tauro External control .......................................................................................................................... 7
2.1.3 Multiple Fronius Tauro External control ......................................................................................................................... 8
2.1.4 Multiple Fronius Tauro External control ........................................................................................................................ 8
2.1.5 Multiple Fronius Tauro External control Feed-in limit ............................................................................... 9
2.1.6 Multiple Fronius Tauro External control Feed-in limit ................................................................................ 9
2.2Systems with inverters from different product series .............................................................................................................. 10
2.2.1 Tauro/SnapINverter combination External control .......................................................................................................... 10
2.2.2 Tauro/SnapINverter combination External control ......................................................................................................... 10
2.2.3 Tauro/SnapINverter combination External control Feed-in limit ................................................................... 11
2.2.4 Tauro/SnapINverter combination External control Feed-in limit ................................................................... 11
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1 FEED-IN MANAGEMENT WITH MULTIPLE INVERTERS
If the grid operator requests a feed-in limit (e.g. maximum power of feeding in must not exceed 70% of the total
PV generator output), appropriate output control measures must be put in place to ensure that the
corresponding parameters are adhered to at the grid feed-in point.
To provide the optimum levels of feed-in management for a PV system with multiple inverters, it is essential that
communication between the installed system components is functioning correctly. What is especially important
in terms of the specifications issued by grid operators (e.g. zero feed-in) is that the control response of the
inverter is precise.
Fronius Tauro inverters have an integrated energy and feed-in management system, paving the way for efficient
system design. Power reduction is implemented in both the software and hardware and provides a
straightforward way of satisfying and implementing the grid operator's specifications.
Automatic communication between individual inverters (I2I) does not exist at market launch.
PV systems with multiple Fronius inverters are designed and controlled differently according to the type of
requirement of the grid operator.
This document examines the various scenarios and requirements of grid operators, and the interaction between
multiple inverters of the same product family and within mixed systems (e.g. Fronius Tauro + Fronius
SnapINverter). The following sections offer solutions for a variety of grid requirements.
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1.1 SOLUTION A – Simple power reduction of an individual inverter
In systems containing multiple Fronius inverters, just reducing the power of a single inverter by installing a
Fronius Smart Meter at the grid connection point may, under certain circumstances, suffice to meet the power
limitation requirements.
The requirements will be met if the following formula applies:
0% of P
This means that if it is possible to reach the specified feed-in limit by reducing the power of a single inverter in
the system to >=0%, solution A can be used.
Example: A system contains 3 inverters: one Fronius Tauro 100 kW and two Fronius Tauro 50 kW
The specified feed-in limit at the transfer point must not exceed 100 kW
Solution: The output power of the Fronius Tauro 100 kW can be lowered to 0% to meet the feed-in limit
requirement. The power levels of the two other inverters are not reduced and can continue to feed-in without
any restrictions.
If reducing the power of a single inverter to 0% of the output power is not enough for the system to meet the
feed-in limit, then solution B (see page 6) must be used.
+ 100% of P
INV1
+ 100% of P
INV2
INV3….
<= feed-in limit
1.1.1 Feed-in limiting according to PV generator output
The following scenario involves a PV system with two inverters. The grid operator has issued strict instructions
regarding the maximum permitted power that can be fed into the grid.
PV generator output: 200 kWp
Overdimensioning: 0%
Nominal inverter output: Inverter 1 = 100 kWac, Inverter 2 = 100 kWac
Feed-in limit: max. 60% of PV generator output
Solution:
With maximum irradiation and at full power, only 120 kWp (200 kWp x 60%) may be fed into the grid
Setting on inverter 1: max. feed-in 120 kWp at transfer point
Setting on inverter 2: no special settings
Once this setting has been made, inverter 2 can feed in as much power
as required, whereas inverter 1 is limited by a Fronius Smart
Meter at the grid connection point and, when inverter 2 is
operating at full power, would feed in 20 kWp.
This simple control algorithm in the Fronius inverters ensures that the grid
operator's specifications can be satisfied.
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