SMART FUNCTIONS & GRID AUTOMATION
Grid automation relies on a set of technologies that can enhance distribution grid management, for example by stabilizing the grid voltage through autonomous power control, by remotely managing distributed generation units and by deploying control boxes associated to smart meters that can contribute to relieving grid constraints.
InterFlex experimented the local trade of flexibilities for distribution grid purposes. In the French and the Dutch demonstrations, the respective DSOs developed dedicated IT platforms to share actual and potential flexibility demands with commercial service providers, the aggregators. The DSOs aimed at sourcing flexibilities on local markets to optimize the operational performance of the gridmanagement.
The Swedish and French demonstrators included Smart Functions and Grid Automation elements in order to achieve their microgrid and islanding targets, based on 100% RES supply in Sweden. Such microgrids require several system balancing services for successful islanding where frequency and voltage control are vital. The seamless switching to and from islanding constitutes an automated function with a direct impact on power quality and customer comfort. In the village of Simris in Sweden the automated functions also stretched into residential homes where battery-state-of-charge dependent Demand Side Management algorithms helped to modulate the power of customer assets. This was done within set boundaries to ensure residential comfort. Similarly, wind and solar resources could be automatically curtailed during islanding, if power output exceeded the consumption and the batteries were fully charged.
The German demonstrator achieved fully automated control of distributed renewable energy resources connected to low voltage networks. The newly developed “Smart Grid Hub” connected directly to the DSO grid control system and served to disaggregate flexibility requests by the DMS. In this architecture the main DMS system is not burdened with the required large number of decisions to be taken when small scale flexibilities are involved. Instead the Smart Grid Hub takes the burden of controlling small flexibilities in response to bulk-requests from the DMS. Use cases that have been investigated include an integrated approach to smart curtailments across voltage levels and dynamic steering of flexible loads in response to price signals or stress on the grid.
The Dutch demonstrator achieved a forecasting model based on historical and real-time asset data which provided autonomous input to the algorithms of the demo’s EV charging stations, thereby procuring a source of flexibility and enriching its Local Flexibility Market.
The Czech InterFlex demonstrator combined several Grid Automation technologies and Smart Functions to increase the DER hosting capacity. This included:
- Autonomous active and reactive power regulation (Volt-VAr) in LV networks: smart PV inverter functions – without any communication with the DSO – were tested together with the consortium’s inverter manufacturers in order to stabilize voltage levels and thus significantly increase the DER hosting capacity in LV grids.
- Volt-VAr control in MV networks: voltage control functions have been implemented in 5 existing renewable power systems – two small hydro plants, a PV, CHP and Wind Park. The DERs received voltage set points from the DSO’s Distribution Management System depending on grid conditions.
- Residential PV systems with storage batteries: the main tested function was the permanent feed-in limitation of active power into the grid which was set to 50 % of the installed PV capacity. The systems were furthermore designed to support the grid by discharging the battery in case of under-voltage, under-frequency (autonomous control) or based on a ripple control signal sent by the DSO through one way simple PLC.
The French and Swedish demonstrators successfully implemented the control of islanded microgrid operation and assets via an islanding master. Another successfully tested smart function was related to the control of the islanding switch designed to perform seamless MV islanding for enhanced power quality for local customers.
The Czech InterFlex demonstrator successfully increased the distribution grid’s DER hosting capacity at close to zero equipment or marginal cost, allowing also to establish recommendations for global replication and large-scale implementation, as well as for an integration of the results in the regulatory framework or grid code. This can also be a valuable contribution to standardize new autonomous functions, for example in the field of EV Smart Charging.
The German demonstrator could deliver the blueprint for the operational integration of grid control and a smart meter infrastructure. This approach enables more flexibility in distribution networks with very low installation costs and delivers efficiency gains in several areas of operation, for example reduced curtailments and improved balancing capabilities.
CHALLENGES & RECOMMENDATIONS
ČEZ Distribuce’s work on the autonomous Volt-VAr functions in LV networks and Volt-VAr control in MV networks has already been translated into national grid codes in order to secure smoother integration of the smart solutions in the future.
The implementation of these solutions at a wider scale could avoid massive investments in the distribution grid reinforcements, while most regions are expected to have insufficient DER hosting capacity.
However, some results also need to be adapted to country-specific parameter settings for autonomous solutions, in order to optimize the specifications that manufacturers need to integrate. Furthermore, it might be necessary to foresee country-specific rules for the activation of PV inverter’s smart functions depending on the installation site.