Interfaces and Control for Direct Marketers and Grid Operators

Starting point

As renewables entered the power market, a new requirement emerged for plant operators: wind farms, solar installations and combined heat-and-power units no longer just have to produce — they have to react to market signals and grid conditions, within seconds, in an auditable way, and in a regulated environment.

In response to customer demand, the data acquisition gateway was extended with exactly that capability: a secure, standardised channel for external market participants and grid operators into the connected generation assets, combined with an integrated control layer. The gateway became bidirectional: it delivers real-time measurements to direct marketers and grid operators and accepts their control signals in return. Over roughly ten years I developed and owned the control algorithms as well as the interfaces to direct marketers and grid operators.

The challenge

Direct marketing and grid operation are two different worlds with their own requirements, which have to come together in one system:

• Direct marketers need to operate plants according to the power market price — ramping output up or down, or following ramps, when the market demands it.
• Transmission and distribution system operators need access for load management: setpoints for active and reactive power, emergency intervention, and contributions to grid stability.
• Both worlds speak classic energy industry protocols, with high demands on availability, determinism and traceability.
• Operationally the system has to work both as a compact hardware setup at the plant and as a fully integrated software solution inside the data gateway.

My responsibility

For around ten years I owned the control layer and the market-side interfaces of this product:

• Implementation of the control algorithms for active and reactive power — open-loop control for market-side setpoints as well as closed-loop control for grid services.
• Real-time control at 10 Hz: the system computes new setpoints ten times per second — the prerequisite for contributions to frequency and voltage stabilisation, and for controlled ramp-up and ramp-down along defined ramps.
• Interfaces to direct marketers such as Next Kraftwerke, energy & meteo systems and Integrasun — both for delivering real-time measurements and for accepting market-side setpoints.
• Interfaces to German transmission and distribution operators, including TenneT, Avacon, Bayernwerk, Mitnetz Strom and Wesernetz, as well as further European grid operators.
• Hardware and software variants: delivered both as a compact hardware solution based on Siemens LOGO and Wago Ethernet controllers with IO modules, and as a pure software solution inside the integrated data gateway that brings plants, grid operators and direct marketers into one system.

Architectural decisions with business impact

Integration into an existing platform instead of an island solution

The control and interface layer wasn’t built as a stand-alone product, but as an extension of the existing data acquisition middleware. This had direct business impact: existing customers could use the new capabilities without running a parallel system, and the overall product offered direct marketers and grid operators a single, consistent point of access to all connected assets — regardless of manufacturer or asset type.

Two variants for different deployment scenarios

Some sites need a dedicated controller at the point of connection; others benefit from a fully integrated software solution. We offered both: a compact hardware variant (Siemens LOGO, Wago Ethernet controller and IO) for on-site use, and a complete software variant that uses every capability of the data gateway. With the same technical foundation, sales could address very different use cases.

The Siemens LOGO also ran a custom control program implementing the regulatorily required priority logic between grid operator and direct marketer: when both setpoints arrive at the same time, the grid operator’s signal takes precedence and overrides the market-driven setpoint. Current generation was read in via S0 pulse interfaces. The solution therefore covered cases where classical automation hardware is required directly at the point of connection — including the correct mapping of the legal intervention hierarchy in the German grid.

Multi-protocol capability as a standard

Direct marketers and grid operators speak different protocols, with country-specific quirks. The interface layer supports IEC 60870-5-101/104, Modbus, OPC XML-DA, OPC UA and ICCP/TASE.2. With that, the system was connectable to virtually every relevant market participant and grid operator in the German and European power market, with no per-integration custom development.

Outcome

• Scale: Several thousand plants — wind, photovoltaic and CHP — actively participate in direct marketing and grid services through the system.
• Market coverage: Connected to the leading German direct marketers and to multiple transmission and distribution operators. With some operators the solution is used as a standard tool.
• Business impact: Built on customer demand, the product in turn brought new customers to the underlying data acquisition platform — an example of how a focused technical extension can carry the whole product portfolio commercially.
• Technical maturity: Second-critical closed-loop control at 10 Hz, multi-protocol, and shippable in two variants for different deployment profiles.

Technologies used

• Languages: C++
• Control engineering: Open- and closed-loop for active and reactive power, 10 Hz setpoint computation, ramp control, contributions to frequency and voltage stabilisation
• Protocols: IEC 60870-5-101/104, Modbus, OPC XML-DA, OPC UA, ICCP/TASE.2
• Hardware platform (compact variant): Siemens LOGO, Wago Ethernet controllers and IO modules
• Market participants (selection): Direct marketers (Next Kraftwerke, energy & meteo systems, Integrasun); transmission and distribution operators (incl. TenneT, Avacon, Bayernwerk, Mitnetz Strom, Wesernetz)

What this experience transfers to

This case study shows a profile that is rare in the market: deep understanding of both control engineering and the organisational and protocol realities of the German and European power market — combined with the ability to translate both into production-grade software that runs reliably 24/7.