Oliver Gehrke

An overview of demand side management control schemes for buildings in smart grids

The increasing share of distributed energy resources and renewable energy in power systems results in a highly variable and less controllable energy production. Therefore, in order to ensure stability and to reduce the infrastructure and operation cost of the power grid, flexible and controllable demand is needed. The research area of demand side management is still very much in flux and several options are being presented which can all be used to manage loads in order to achieve a flexible and more responsive demand. These different control schemes are developed with different organization of the power sector in mind and thus can differ significantly in their architecture, their integration into the various markets, their integration into distribution network operation and several other aspects. This paper proposes a classification of load control policies for demand side management in smart buildings, based on external behavior: direct, indirect, transactional and autonomous control; internal operation: decision support system scope, control strategy, failure handling and architecture. This classification assists in providing an overview of the control schemes as well as different ways of representing a building.

A clearinghouse concept for distribution-level flexibility services

Flexibility resources on the demand side are anticipated to become a valuable asset for balancing renewable energy fluctuation as well as for reducing investment needs in distribution grids. To harvest this flexibility for distribution grids, flexibility services need to be defined that can be integrated with distribution grid operation and that provide a benefit that can be traded off against other grid investments. Two key challenges are here that the identification of useful services is still ongoing and that the transaction cost for the individually small contributions from the demand side could be prohibitive. This paper introduces a flexibility clearinghouse (FLECH) concept and isolates FLECH key functionality: to facilitate flexibility services in distribution grids by streamlining the relevant business interactions while keeping technical specifications open.

Fault tolerant aggregation for power system services

Exploiting the flexibility in distributed energy resources (DER) is seen as an important contribution to allow high penetrations of renewable generation in electrical power systems. However, the present control infrastructure in power systems is not well suited for the integration of a very large number of small units. A common approach is to aggregate a portfolio of such units together and expose them to the power system as a single large virtual unit. In order to realize the vision of a Smart Grid, concepts for flexible, resilient and reliable aggregation infrastructures are required. This paper presents such a concept while focusing on the aspect of resilience and fault tolerance. The proposed concept makes use of a multi-level election algorithm to transparently manage the addition, removal, failure and reorganization of units. It has been implemented and tested as a proof-of-concept on the distributed smart grid test bed SYSLAB at the Technical University of Denmark.

Asynchronous control of Distributed Energy Resources using behaviour descriptions

The activation of power system services from small DER is a key to building electrical power systems with a high penetrations of renewable generation. Reliable, real-time and low-cost communication to a large number of DER units is required for controlling these resources, but difficult to achieve. This paper presents an alternative to traditional closed-loop control which has the potential to relax the real-time requirements on the communication link between supervisory controller and DER unit. Examples are given, and experimental results are provided as a proof-of-concept.