Stability of decentralized generators in the electrical power supply network when providing ancillary services
The transition of the electrical energy system requires adaptable operational management concepts with regard to the large number of decentralized generators (DGs) in order to ensure, among other things, the maintenance of frequency and voltage. Nowadays, for example, one actively intervenes in the reactive power budget of networks by specifying centrally optimized operating points. However, passive methods such as Q(U)-control continue to serve as a fallback level since they are very easy to use and can locally influence the system voltage by adaptively providing reactive power. DGs are subject to technical fluctuations due to the source of primary energy and are increasingly exposed to economic fluctuation. They are more and more being used in direct marketing so that the increased adherence to schedules at the crossover between the 15-minute marketing intervals can lead to high gradients in available power. Accordingly, the plant control should be able to safely handle frequency and voltage jumps (due to time-synchronous DG behavior) in order to exclude undesirable overshooting or even unstable behavior. However, the problem in this setup is that each plant controller works for itself, i.e., it only monitors and processes the controlled quantity at its own measurement point in the grid. The overall impact of all control activities is not considered by the plant controllers. This leads to highly interesting and challenging control theoretic problems.
The aim of the project is to develop application- oriented guidelines for the evaluation of the robust stability of control systems for DGs in electrical power supply networks. On the one hand side, it is important to have the control-theoretically exact definition and, thus, ensure stability - even in the event of subsystem failures - and on the other hand side, the practical applicability of the criteria in the form of guidelines and easy-to-use formulas. In addition, questions on robust stability as well as the detection and identification of incorrect plant controls will be addressed. To this end, methods are going to be developed that allow the grid operator to carry out an evaluation of the current system stability margin within a limited grid area and with minimal effort. Against the background of the expanding digital interconnection the role of improved communication structures with low latency for the control system performance will be investigated. E.g., if the DG controllers are able to communicate the control system performance and stability margin could be greatly improved. The results can serve as a basis for future research projects in the field of automated network operation management. They can further motivate the utilization of such appropriate communication structures in reality if necessary. The algorithms and concepts developed during the project will be tested on a powerful network model which is physically available at the applicants of this proposal.
This project is a cooperation of the Institute of Control Theory with the Institute of Electrical Power Systems and High Voltage Engineering at TU Dresden.
This project is funded by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation - project number 442893506.
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