Cheap smart grids with ripple control technology

Project state
Set-up in the SmartEnergyLab of Fraunhofer ISE. The laboratory offers an optimal simulation and test environment for smart building energy systems. As part of the project, a ripple control system will be integrated to test the communication line and the smart controllers.

In addition to grid expansion, controllable loads and generators are prerequisites for an affordable energy transition. So far, smart grids have failed due to the high costs of smart meters. There does not seem to be any cheap option for small systems in the medium term. The grid can still be operated as a smart grid using other technologies, however. Applying these alternative technologies is a declared goal of CheapFlex.

This research project intends to implement audio frequency ripple control technology. Already a proven element of grid control technology, it enables the core functions of smart grids to be implemented in a cost-effective and timely manner. This is already a reality for photovoltaic feed-in management. Essential functions for the distribution grid operation and an optimisation of the overall energy system are made possible:

© Fraunhofer ISE
  • Feed-in management of renewable energy systems
  • Remote parameterisation of decentralised reactive power controllers
  • Blocking periods for “critical grid operation”
  • Flexible tariff switching times for generators, loads and storage systems

The research project aims to create non-discriminatory and dynamic tariffs based on tariff switching schedules. In contrast to the currently usual rigid high- and low-rate tariffs or blocking periods determined by the grid operator, incentives can be set to dynamically adapt the loads to the supply situation. For an energy supply system characterised by renewable electricity generation, only the transmission of dynamic tariff switching times yields sufficient degrees of freedom for meaningful incentives for decentralised, automated and system-serving electricity procurement and infeeds. The proposed utilisation of ripple control technology for dynamic tariffing accords with both the smart market and smart grid concepts:

  1. During regular operation, end-consumers and decentralised generators can automatically contribute to system-serving behaviour based on dynamic incentives.
  2. In emergency or extreme situations, regular operation can be influenced during the course of network operations management to include even direct control actions.

Local grid problems can be counteracted with the aid of blocking times and a blocking signal that can prohibit consumer operation. In addition, this makes it possible to economically optimise the grid operation, shed loads and power, and also offer ancillary services.

Schema des Systemaufbaus. Ein Verteilnetzstrang mit unterschiedlichen Gebäudetypen und unterschiedlichen Endgeräten wird modelliert. Die dynamischen Tarife werden mit Hilfe der Rundsteuertechnik als Broadcastsignal von der Leitwarte aus in den Netzstrang geschickt.
Schematic illustration of the system set-up. A distribution grid line with differing building types and consumers is being modelled. Using ripple control technology, the dynamic tariffs are transmitted from the control room to the grid line in the form of broadcast signals.

Simulation and field test to confirm the function

In collaboration with TU Kaiserslautern, Fraunhofer ISE is developing algorithms in the CheapFlex project that make it possible to address not just customer groups but also individual grid lines with a high resolution. To this end, existing algorithms and protocols for ripple control technology are being further developed by Swistec GmbH to define smaller address ranges and to increase the information density.

The concept's potential flexibility will be initially investigated in CheapFlex using a simulation, and its ability to be implemented will be verified based on functional models in field trials. A qualitative and quantitative comparison with the corresponding high-end solutions will be made using grid simulations. The algorithm developed to adapt the operational management to the dynamic tariff switching times is being implemented prototypically in an energy management system. This will then be integrated into Fraunhofer ISE's SmartEnergyLab and used for the operational management of a cogeneration plant. The hardware-in-the-loop simulation in the SmartEnergyLab secures the development of efficient and stable algorithms, thus ensuring successful testing of the functional models. In a final step, these models will be set up and tested in a field test at customers with controllable generation systems and loads (CHP, heat pumps, batteries, photovoltaic systems, etc.) in the grid area belonging to the Stadtwerke Ahaus municipal utility company.

By significantly widening the deployment of ripple control technology, the aim is to realise partial aspects of the smart grid in a cost-effective and economically beneficial manner. The scientists consider this approach to be particularly promising given the current development of smart metering technology.

Project duration

05/2015 – 10/2017


Raphael Hollinger
Project co-ordinator
Fraunhofer-Institut für Solare Energiesysteme ISE
Heidenhofstraße 2
79110 Freiburg

+49 761 4588 5179


Presentation of the project on the website of project partners

Fraunhofer ISE

Basic information

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