Communication Requirements for Flexible Control of Distr. Pow. Systems

In order to meet the challenges posed by the distribution of energy resources, the liberalisation of energy markets and increasing generation from renewable sources, a variety of new concepts for power system structure and control are being discussed and actively researched on. These range from simple aggregation - for example through virtual power plants - towards more radical approaches, such as replacing traditional distribution systems by collections of microgrids, or the decentralisation of control. It is an open question how future grids will be operated, and what kind of new features will be feasible and desirable. Given the 1ong-term nature of infrastructure investments, it is of utmost importance that the devices and technologies deployed in the short term do not restrict progress in the medium and long term. With respect to communication and data exchange between power system components, it is important to ensure that the communication standards are able to grow and be extended as new intelligent devices, control paradigms and power system components appear. Communication standards should therefore avoid assumptions about the structure of the control system.



The three main limitations of the current standards are:



• Insufficient separation of concerns. Immutable properties (such as nameplate information), configuration (such as device-subdevice relations), state (such as the cycle count of a circuit breaker) role (such as the present operating mode of a power plant) and application scope (such as substation automation) are mixed.
• The lack of a single, unified model of the power system and its components.
In today's power system, communication protocols are tightly tied to an application (see Figure 1). lnterfacing between the device-centric view of SCADA systems (for which the IEC61850 family of standards was created) and the system-oriented view of EMS applications is still a challenge, because the underlying data model is different.
• Limited extensibility. The growing number of DER connected to the power system will create a need to delegate control tasks away from the system level towards local control structures (The different operating modes of the Horns Rev windfarm are an example for such a delegation). The protocols of the IEC61850 series use predefined
lists (enumerations) to describe types of behaviour, which is difficult to adapt to new developments.


The project aims at producing a conceptual framework for the unified and extensible representation and exchange of power system information and data. While the development of a standard is explicitly not one of the goals of the project, a proof-of-concept implementation will be undertaken for demonstration purposes.


It is very difficult to test the full functionality of a new communication protocol on a real power system. as e.g. results from the NextGen project have shown. Not all potential operating modes of a unit can be tested without interfering with the control of the overall grid. Therefore, the implementation will be tested in the isolated environment of the SYSLAB grid at Risø.


Results from the project will be published as a technical report, to provide input to the standardization work under IEC TC57.