REALISEGRID. Improving network controllability by coordinated control of HVDC and FACTS devices

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1 REALISEGRID Improving network controllability by coordinated control of HVDC and FACTS devices Contributors: Ulf Häger, Johannes Schwippe, Christian Rehtanz, Technical University Dortmund WP1 Workshop Arnhem, 29 th September, 2010

2 Influence of FACTS devices Power Flow Controlling devices have influence on several lines in their neighbourhood Shunt controlled FACTS devices have only local influence G G G 2

3 Local controls vs. Coordinated control The combination of several local controls can lead to inefficiencies for the overall transmission system Coordinated control searchs for optimal control settings with respect to the overall transmission system G G G 3

4 PST Installations in Europe The European TSOs have constructed almost 20 PST during the last decade The number of PSTs is expected to increase further in the future Currently there exist several regions with PSTs having mutual influence: Benelux (Eight PSTs operated by four different TSOs) Border between France and Italy (Three PSTs operated by two different TSOs) Austria (Three PSTs operated by Verbund APG) Many PST installations are located at the border between neighboring TSOs 4

5 Current approach for coordinating PSTs in Europe d-3 d-2 d-1 d Capacity allocation Security planning Real time operation Capacity allocation process: Based on NTC values, calculated twice a year Coordination is not possible with the current frequency of calculations Operational day ahead security planning: Finding globally optimal PST settings is only possible by performing joint security analysis of all involved TSOs In the past each TSO made individual security analysis First joint security centres are being established (compare next slide) Real time operation: Forecast errors of security planning, detected by online measurements, can require modification of PST control values Coordination is only possible by online exchange of data between all involved TSOs (not yet implemented) 5

6 Coreso Security centres Joint regional security center of ELIA (B), National Grid (UK) and RTE (F) Collects forecast data of the involved TSOs in a common data format to perform joint security analysis The establishment of a quasi real time security analysis is envisaged Security service center (SSC) Joint regional security center of Amprion (D) and Tennet (NL) Collects forecast data of the involved TSOs in a common data format to perform joint security analysis Transmission System Operator Security Cooperation (TSC) Global security center of 50Hertz Transmission GmbH (D), Amprion (D), CEPS a.s. (CZ), ENBW (D), PSE Operator S.A. (PL), Swissgrid (CH), Tennet (NL), Tiwag Netz (A), Transpower Stromübertragungs GmbH (D), Verbund APG (A), VKW-Netz AG (A) Collects forecast data of the involved TSOs in a common data format to perform joint security analysis The establishment of a quasi real time security analysis is envisaged 6

7 Example of Benelux Eight PSTs with mutual impact, operated by four different TSOs 380 kv 220 kv PST Meeden Netherlands (NL) Zwolle Diele Niederlangen Conneforde Hengelo Gronau TSO Voltage Smax Gronau Amprion 380 kv 1250 MVA Meeden Tennet 380 kv 1000 MVA Meeden Tennet 380 kv 1000 MVA Diele Transpower 380 kv 1425 MVA Diele Transpower 380 kv 1425 MVA Zandvliet ELIA 380 kv 1400 MVA Van Eyck ELIA 380 kv 1400 MVA Van Eyck ELIA 380 kv 1400 MVA Avelin Avelgem Lonny France (F) Zandvliet Belgium (B) Siersdorf Gramme Achene Aubange Lux. Moulaine Vigy Germany (D) Van Eyck Oberzier Uchtelfangen 7

8 Principle of Optimal Power Flow for coordination of PSTs In Optimal Power Flow the settings of PSTs or FACTS devices are selected so that the chosen objective function is minimized i, k Power flow equations ( V, θ, V ) f ( x) = Pik, loss i i k, θk g( x) = Constraints of control devices ϕ 0 ϕ ϕ PST, min PST PST,max Constraints of network devices I ik I ik,max 8

9 Approach for coordinated capacity allocation and security planning Optimal Power Flow approaches are most convenient for these applications Maximization of TTC values 1 Decentralized Optimal Power Flow Control for Overlapping Areas 2 Load flow equations Linear Non linear Linear Allows for coordination of... PSTs FACTS, PSTs PSTs Objective function of the optimization - Maximization of TTC - Minimization of system losses - Minimization of active power losses - Minimization of bus voltage deviations - Prevention of line overloads Minimal Reduction of Unscheduled Flows 3 - Minimization of power losses - Minimum change of PST angles Consideration of N-1 contingencies Several Several Complete N-1 criterion preventive or Preventive Preventive Corrective corrective? Local control - X (X) Wide area control X X X Multi-area optimization - X - Computation time Several minutes Several minutes Several minutes 1 J. Verboomen, Optimisation of Transmission Systems by use of Phase Shifting Transformers 2 G. Hug-Glanzmann, Coordinated Power Flow Control to Enhance Steady-State Security in Power Systems 3 A. Marinakis, M. Glavic and T. Van Cutsem, Minimal Reduction of Unscheduled Flows for Security Restoration: Application to Phase Shifter Control 9

10 Approaches for coordinated real time control of FACTS and HVDC Requirements: Automatic control system is needed Fast online exchange of system data is needed (Possibly by PMU measurements) The amount of data to be exchanged between involved TSOs must be as small as possible The control must adapt to changes in the grid (topology changes, changing power flow situation) Control must be robust during any system event Approaches: Hierarchical coordinated control of multiple FACTS devices 1 2 Coordinated control of power flow controlling devices based on multiagent systems 3 Time horizon for implementation: medium- or long term 1 C. Rehtanz, Autonomous Systems and Intelligent Agents in Power System Control and Operation 2 A. Oudalov, Coordinated Control of Multiple FACTS Devices in an Electric Power System 3 U. Häger, S. Lehnhoff, C. Rehtanz, H. F. Wedde, Multi-Agent System for Coordinated Control of Facts Devices 10

11 Hierarchical control Management Co-ordination network control level Execution Response time Degree of decentralization Management Management Co-ordination Co-ordination Execution Execution Management Management Management Co-ordination Co-ordination Co-ordination Execution Execution Execution substation control level bay control level Sensor / Actuator Sensor / Actuator Sensor / Actuator 11

12 Multi-Agent Control Each serial device in the power system is represented by an agent. Messages are sent along the network topology Agents of Power Flow Controlling (PFC) devices evaluate the messages to determine Network topology A PFCs expected impact Necessity of control actions i; l 3, l 2, l 1, c 1 i; l 3, l 4, l 5, c 1 12

13 Conclusions In the last decade several PSTs were constructed in Europe Several regions in Europe have PSTs with mutual influence Most PSTs are located at the border between TSOs Local control of PSTs with mutual influence shifts the bottleneck to another place Coordination of PSTs with mutual influence is necessary to reduce bottlenecks First joint security centres are being established by some TSOs in Europe to implement a quasi real time coordination 13

14 Research questions Short term horizon: Coordination in security analysis by use of Optimal Power Flow methods Medium or long term horizon: Coordinated online control requires new approaches. Further research is necessary, e.g. based on hierarchical control structures or Multi-Agent systems To assure robustness of online control systems is of highest importance 14