Ulf Häger

A Multiagent System for Adaptive Power Flow Control in Electrical Transmission Systems

Large-scale integration of renewable energies causes a higher degree of volatility and uncertainty of power flows in the electrical transmission system in Europe, and thus a higher risk of cascading line outages possibly leading to blackouts. At the same time, the transformation of the power system into a cyber-physical system deploying evolved information and communication technology (ICT) solutions offers the opportunity to meet this challenge efficiently by intelligent control approaches instead of ample security reserves. In this paper, a novel approach for a distributed real-time coordination of power flow control is presented. For this, a multiagent system located decentrally at the substation level has been developed only relying on local measurements and interagent communication in contrast to global system models and centralized computations. Based on updated information received from neighboring agents, the agents quickly adapt to changing network situations and relieve overloads by coordinated action of power flow controlling (PFC) devices. For smoothing control behavior and for avoiding excitation of system oscillations, the extent of control actions also adapts to the severity of the network situation. For two study cases-examining the control system in the IEEE 39-bus 10-machine reference system and a large-scale model of the Western European transmission system-the performance of the multiagent system and ICT requirements is evaluated based on a co-simulation of the multiagent system and an electromechanical power system simulation.

New applications for wide-area monitoring, protection and control

As operation of electrical transmission systems faces new challenges due to liberalization and integration of renewable energies, novel solutions for power system management are needed. At the same time, the development of smart grids also pushes high performance communication and information technology that contribute decisively in enabling a dynamic monitoring, protection and control of large-scale and wide-spread power systems. The potential offered by smart grids and new fast controllable power systems equipment needs to be exploited by development of valuable applications for power system operation. Moreover, first experiences with selected dedicated applications call for the design of an integrated wide-area monitoring, protection and control (WAMPAC) system. This paper presents recent progress of research unit FOR1511 in the development of WAMPAC applications for stability monitoring, protection schemes based on wide-area information, and real-time congestion management. The research unit aims at developing a coherentWAMPAC system taking into account interdependencies and synergies of newly developed applications and conventional local systems in place.

Influences of wind energy on the operation of transmission systems

In this work the impact of wind energy on the power flow is analyzed. After the development of a reduced sample network, possible network congestions are identified and the costs for the required redispatch of the generation are evaluated. To avoid or reduce the probability of congestions, different network upgrades can be installed. The efficiency of additional lines and power flow controlling devices is discussed on the basis of power flow calculations and dynamic simulations.

Coordinated wide area control of FACTS for congestion management

This paper presents an approach to evaluate the benefits of an autonomous wide area control as coordination method for a fast power flow controlling device. This device, called dynamic power flow controller (DPFC), is introduced together with its control scheme and the coordination method. Simulations are performed to determine the transfer capability that can be reached by using the DPFC compared to an usual phase shifting transformer at different congestions corridors.

Multi-Agent System for Coordinated Control of Facts Devices

This chapter targets on a multi-agent approach for an automated coordination and control of power flow controllers (PFC). In comparison to chapter 10 no central instance is required for the topology analysis. The agents derive the relevant actual topology through local communication and perform coordinated control actions according to the present situation. Therefore the approach can be implemented easily under the condition that a fast communication network between all network elements is available.

Exchangeability of power flow simulators in smart grid co-simulations with mosaik

Power flow simulators are indispensible when simulating and assessing future energy system scenarios potentially comprising vast numbers of actors, devices, markets, environmental phenomena etc. While open source power flow simulators are an appealing choice - as they come free of charge - commercially available power flow simulation and optimization suites have the clear benefit of being well established and trusted by the industry. Open source implementations often lack validation against these “trusted” outputs. In this paper we will demonstrate and discuss the integration and exchange of different (commercial as well as open source) power flow simulators with the co-simulation framework mosaik for the sake of comparing and possibly benchmarking the output of open source simulators.

Autonomous distributed coordination of fast power flow controllers in transmission networks

With the liberalization of the power markets the average distance between power generation and consumption increases which leads to an increase in utilization of certain transmission corridors connecting e.g. off-shore wind parks to areas of high demand (industrial and urban districts). Together with rising power demand and the integration of high-capacity unpredictable renewable resources (e.g. volatile wind power) these factors pose a challenge to todays transmission networks. Operators have to guarantee a stable and efficient operation of the grid. One way to improve the stability and efficiency of the existing network - aside from expensive and most often very time-consuming reconstruction - is the integration of power flow controllers (PFCs) in order to dynamically redirect power flows away from critically loaded resources that may be threatened by an overload and thus (with the obvious drawback of higher transmission losses) accomplish a higher degree of available capacity utilization. In this paper we outline our current work on the development of a multi-agent-based real-time operation of PFCs that allows for an autonomous distributed coordination of fast power flow control actions across (international) control areas without the need for global information.

ICOEUR project results on improving observability and flexibility of large scale transmission systems

Interstate connection of power grids provides multiple advantages concerning operational security, integration of renewable energies as well as electricity trading. Based on these boundary conditions, the ICOEUR Project (supported by EU-FP7 and the Russian federal agency of science and innovation) studies smart technologies, to enhance the transmission capability, observability and security level of large scale transmission grids, such as a possible future interconnection of the European and Russian transmission systems. In this paper we present a selection of results of the ICOEUR project including case studies, such as an autonomous real-time coordination system for Power Flow Controlling devices. All case studies in the ICOEUR project are carried out on a common network model, which was developed by the project partners based on publicly available data. This network model consists of 545 nodes and includes a reduced dynamic model of an interconnected transmission system of European Network of Transmission System Operators for Electricity (ENTSO-E) and Integrated Power System/Unified Power System (IPS/UPS).

Applicability of coordinated power flow control based on multi-agent systems

An overall increase in power demand together with the liberalization of the power markets and the integration of high capacity unpredictable renewable resources (e.g. wind power) pose a challenge to transmission networks. Network operators have to guarantee a stable and efficient operating of the grid. A way to improve the stability and efficiency of the existing network — aside from expensive reconstruction — is the integration of fast power flow controllers in order to dynamically redirect power flows away from critically loaded resources that may be threatened by an overload. In this paper we present a multi-agent based algorithm that allows for an autonomous distributed coordination of fast power flow controllers without the need for global information.

Application of self-organizing systems in power systems control

The European electrical transmission network is operated increasingly close to its operational limits due to market integration and increased feed-in by renewable energies. For this reason, innovative solutions for a reliable, secure and efficient network operation are requested. The application of self-organizing systems promises significant potential in real-time control. This paper outlines the challenges of power system operation, gives a brief overview of relevant system characteristics and discusses the applicability of self-organizing systems for different fields of power system control. As a result of current research, the application of an agent-based decentralized power flow control system is presented and discussed in comparison to current practice based on central decision making.