NAME : S. RAPOPORT COUNTRY : BELGIUM REGISTRATION NUMBER : C2-203 GROUP REF. : C2 PREF. SUBJECT : PS2 QUESTION N : 2.6

Transcription

1 PEGASE R&D project: Advanced algorithms for state estimation and simulation of the Pan European power system The PEGASE project has produced new tools to enhance the cooperation among transmission system operators for the real time control and operational planning of the Pan-European transmission network. New powerful algorithms and full-scale prototypes have been developed that run the whole European Transmission Network model for state estimation, dynamic security analysis, steady state optimization and dispatcher training simulator. PEGASE is a four-year R&D project funded by the 7th Framework Program of the European Union. It is implemented by a consortium composed of 22 Partners which includes Transmission System Operators, expert companies and leading research centres in power system analysis and applied mathematics. 1

2 State Estimation A new Two-Step State Estimation (TSSE) algorithm has been developed, dividing the ETN into TSO areas, for which decoupled SEs are locally run. Then, boundary coupling among areas is taken care of by means of a coordination process. Compared to the state of the art, the proposed TSSE makes use of the minimum area overlapping that allows all raw measurements to be processed during the first stage, which means that the coordination stage becomes linear. Furthermore, sparse weighting matrices are handled throughout the process, reducing the computational effort without sacrificing accuracy. Tests have demonstrated that the proposed scheme involves a very modest amount of data exchange, while retaining essentially the same accuracy and capability for bad data identification as the conventional estimation of the entire ETN. The TSSE prototype is capable of solving any number of TSOs, arbitrarily interconnected, for any type of available measurements, including those provided by PMUs and Ampere measurements. In addition to conventional network models, it considers advanced components, such as phase shifters and HVDCs. The TSSE prototype has been extensively tested to ensure the quality of results provided by this kind of algorithms, while minimizing the exchange of data between TSOs. The case study is representative of European and Turkish systems together: 9200 nodes (640 of them being border buses), lines and 2500 transformers, over measurements, covering 26 countries (28 TSOs). The total solution time on a laptop (Intel Core i5) for the whole UCTE network was just about 4 sec. Steady State Optimization Treatment of potentially huge number of contingencies The enormous challenge given to the PEGASE project was to be able to solve problems with networks consisting of more than nodes, more than contingencies. In the new approach proposed by the project, called ISCOPF, a potentially huge amount of post-contingency constraints is treated by two complementary methods: 2

3 In order to reduce the number of contingencies that need to be analyzed simultaneously in a constrained optimization problem, a small superset of the binding contingencies is identified in a sequential manner, by using concepts of constraint domination or umbrella contingencies recently developed in the literature. In order to reduce the number of variables introduced by each contingency and thus to increase the number of contingencies that may be analyzed simultaneously in a constrained optimization problem an original network compression method has been implemented, which exploits the property that the impact of a contingency is limited to a localized region of the network and allows to replace the rest of the system by an equivalent network. They proved that the SCOPF algorithm is able to solve optimization problems of an unprecedented size, involving large systems and numerous contingencies. Indeed, a SCOPF on the ETN with more than 6000 contingencies has been solved in less than 45 minutes. Treatment of discrete behaviour of equipment for very large system A prototype has been developed, which implements optimization for different objective functions (minimal deviation of generated active powers, active losses) taking into account the discrete behaviour of equipment: taps of OLTC and PST, switching of capacitors/reactors banks, shutdown/startup of generators for very large system like the ETN but without contingency constraints. In order to reduce the complexity of the problem, a solution based on a sequence of optimization problems, relaxing at each step integrality constraint for some discrete variables has been proposed and combined with the use of a solution based on MPEC constraints, which consists in substituting the discrete variables by continuous variables with complementary constraints. This approach doesn t strictly guarantee optimum values for discrete variables but at least provides a feasible solution, improved values of discrete variables, and a local optimum for continuous variables. The associated performances on European network sizes are of less than 30 minutes of computation time. 3

4 Real Time Dynamic DTS The PEGASE project has developed a real time simulation prototype capable of simulating the entire ETN with high fidelity, whatever the electromechanical behaviour of the system, up to the complete blackout and the subsequent restoration. The main characteristics of the developed prototype are as follows: First real time dynamic simulation engine allowing the simulation with good accuracy of a European size power system. The produced results are of very good accuracy (validated by comparison with the results produced by the EUROSTAG reference variable step-size software). The following graphs represented the performances reached by the prototype in terms of accuracy. Except minor time shifts the solutions are undistinguishable. The possibility for the user to define the controllers using block-diagram. This functionality is very important for a DTS used in production environment where the models must be easy to maintain to follow the evolution of the real system. A modern communication protocol. The integration of the OPC/UA communication protocol allows to easily connect the DTS engine to various modern MMI and/or SCADA. All models handled by the DTS prototype can be exported to the Full Accuracy Prototype to validate the solution of the DTS and to provide greater flexibility to set up complex scenarios. 4

5 The DTS has been tested on a European size system: busbars, lines, 3800 generators, variables and is able to reproduce typical phenomena of the European grid. Difference with real time is barely noticeable as shown on the following graph: 5