The energy transition is increasingly shifting to low-voltage grids: photovoltaics, electric mobility, heat pumps, and home storage systems are driving up both feed-in and peak loads. This poses growing challenges for grid stability, but at the same time creates significant economic potential through the smart use of flexibility.
A new position paper from the WARAN project consortium—which was also coordinated with the SISSY consortium (both projects are funded by the BMWE)—shows how the existing infrastructure of the intelligent metering system (iMSys) can be further developed from a primarily reactive to a proactive, market-oriented control system. Central to this is the concept of the envelope curve.
From Ad Hoc Control to Preventive Flexibility Management
To date, grid-oriented control in the low-voltage sector has primarily been used as a last resort, for example under Section 14a of the Energy Economy Act (EnWG) or Section 9 of the Renewable Energy Sources Act (EEG). These instruments enable immediate power limitation in congestion situations.
The power envelope takes effect earlier: It defines a power framework (maximum and optional minimum consumption or feed-in values) for future time intervals, within which an energy management system can optimize the connected installations. Technically, the concept is based on the EEBUS use case “Power Envelope (POEN)” and utilizes the standardized, cyber-secure infrastructure consisting of a smart meter gateway and a control device.
This makes iMSys a platform for the proactive, coordinated use of flexibility that is both grid- and market-oriented.
Added Value for Distribution Utilities: Predictability Instead of Disruption
The envelope curve gives distribution system operators the ability to address congestion as early as the day-ahead horizon. Instead of taking short-term action, a forecast-based capacity limit can be communicated that:
- proactively prevents grid overloads
- Increases predictability in grid management
- Is taken into account in a binding manner in grid planning when incorporated into contracts (e.g., via Flexible Connection Agreements)
The envelope curve is clearly prioritized below ad hoc emergency control—curative signals always take precedence. This creates transparency and traceability for all parties involved.
New Options for Suppliers and Flexibility Marketers
The iMSys also provides energy suppliers and aggregators with a scalable, standardized control path. The envelope curve can be used for:
- Schedule optimization on the spot market
- Physical balancing group management (in the future)
- Direct marketing of smaller generation facilities
- System services such as minute-by-minute reserve
The key advantage: no additional proprietary hardware is required. Control is handled via the meter point operator’s secure infrastructure, which is already in place. Especially against the backdrop of regulatory liberalization and growing flexibility markets, this creates an attractive playing field for new business models.
The Role of the Metering Point Operator: Coordinator and Conflict Resolver
As a neutral control administrator, the metering point operator plays a key role. It verifies authorizations, processes control requests, and creates a so-called residual profile when there are concurrent demands from the grid and the market.
This ensures that multiple envelope curves are merged without conflict—with clear prioritization and transparent feedback to the market participants involved.
Our Contribution to the Industry Discussion
The WARAN and SISSY projects bring together key companies from a wide range of industries, which contribute their expertise to advancing the concept of control.
- EWE Netz and TMZ , with their experience gained directly from working with customers and operating power grids and metering points
- KEO and EEBUS as innovators in digital control signal transmission
- BTC and Robotron, service providers in the energy industry specializing in large-scale data processing and analysis
- Lumenaza, a SaaS provider offering innovative end-customer solutions
- Viessmann, an experienced expert in the heating industry, specializing in innovations in the heat pump sector and HEMS
- FfE, the supporting research institute focusing on key areas of the energy sector
- PPC as the leading manufacturer of smart meter gateways in Germany
This position paper is intended as a technical contribution to the discussion on the further development of iMSys-based control systems. It demonstrates how technical standards, regulatory frameworks, and practical project experience can be integrated to harness flexibility efficiently, safely, and cost-effectively.
The envelope curve is thus more than just a technical detail: It is a building block for the system-oriented and market-integrated orchestration of household-level flexibility and another step toward further developing the smart meter gateway into the central sensor and control node in the grid.
