ROLE OF RESONANCES IN THE OPERATION AND EXPANSION OF POWER GRIDS

Transcription

1 1 ROLE OF RESONANCES IN THE OPERATION AND EXPANSION OF POWER GRIDS Walter Sattinger, Swissgrid Olga Galland, HES-SO Fribourg 2015 SCCER-FURIES Annual Conference 25 Nov Lausanne, Switzerland

2 2 Content 1. Transmission System Operation Challenges a. Operation of Highly Meshed Power Systems b. Current Experience c. System Expansion Impact d. Impact of New Devices 2. Analysis Tools and Mitigation Solutions

3 Transmission System Operation Challenges

4 4 Operation of Highly Meshed Power Systems A high number of players exchange information and power flows Transmission infrastructure with life cycle periods of years is the result of a historical development Operation has to be adapted to changing system expansion design criteria Quality of supply on the interface between different partners within the interconnected power system has to be guaranteed at all times Impact of harmonics within the transmission system is increasing due to increased use of underground cables and power electronics

5 5 Current Experience 1 Due to violation of EN and IEC standard limits active filter operation in one substation was required Unfavourable system impedance with respect to critical resonance frequencies

6 6 Current Experience 2 Harmonic measurements due to industrial consumer impact High inter-harmonics level, high flicker level

7 7 Current Experience 3 Measurement of current harmonics level for system expansion preparation Low THD margin 2.14% / 3%

8 8 Current Experience 4 Converter behaviour during island tests 5 Hz oscillations due to power electronic and low short circuit power

9 9 Summary Detailed observation and analysis of each system change is required: New connections consumer, generation System expansion Collaboration with all partners Continuous impact analysis of different equipment is required

10 Analysis Tools and Mitigation Solutions

11 11 Objectives To analyze possible resonance problems in mixed power systems related to the addition of underground (UG) cables and integration of HVDC line; To investigate the impact of different voltage levels on each other.

12 12 Proposed Solutions Implemented frequency dependent models: Overhead line Underground cable Power transformer Power converter (e.g. modular multilevel converter) Used methods: Frequency scan Resonance mode analysis

13 13 Proposed Solutions Used methods: Frequency scan

14 14 Proposed Solutions Used methods: Resonance mode analysis

15 15 Proposed Solutions Used methods: Real case study - Swiss EHV transmission power system

16 16 Contributions Presented frequency analysis enables identification of weak nodes (in sense of resonance) in a transmission power system and provides valuable information to avoid resonance frequency shift to lower critical regions in the case of undergrounding transmission lines in the system; No dramatic resonance frequency drop NO OH Line No resonance after undergrounding High PF YES Dramatic resonance frequency drop NO NO UG Cable Resonance before undergrounding YES PF 0 YES No significant resonance after undergrounding The impact of harmonic sources such as voltage source converter (e.g. modular multi-level converter) on different voltage levels of the AC power system is investigated.

17 17 Collaborations and Acknowledgments HES-SO Valais EOS Holding SCCER FURIES Swissgrid Groupe-E

18 18 Thank you for your attention