Grid Stability Enhancement by LVRT Retrofitting of Existing Wind and Solar Power Plants Kristoffer Qvist Nielsen Vice President Global R&D, KK Wind Solutions A/S 1
Contents 1. Introduction 2. Grid codes: why grid codes 3. Impact on grid stability 4. Possible solutions 5. Conclusions 6. Acknowledgments 2
Specialised systems supplier for wind power solutions +35 Years of experience Building on more than 35 years of experience, KK Wind Solutions is a strong partner in electrical systems for wind turbines
Grid Code regulation for wind Grid code determines how a generator or a customer load should react to a grid disturbance, with its objective being secure and stable operation of power system Grid code in the past • Old technology, limited controllability and no observability LVRT Requirement • Allowed simple ON/OFF operation Impact at higher peneteration • A severe fault in the grid can lead to outage of significant wind power generation, potentially leading to a fault V(pu) 1.0 blackout Steady state operation 0.9 • Due to a sudden frequency event, 0.8 0.7 Dynamic reactive power compensation generation of as high as 50% can trip 0.6 0.5 0.4 0.3 WTG may disconnect 0.2 0.1 0 0.5 3 1.0 1.5 2 2.5 Time(s) 4
Impact on grid stability A Danish Case Study Onshore capacity per technology 1 Fault at Vester Hassing substation 0.8 Voltage (pu) 0.6 Impact on grid security 0.4 0.2 4 4.5 5 5.5 6 6.5 7 7.5 Time (sec) 5
Possible solutions to address diminishing reactive power 1. Must run conventional power 2. Synchronous condensers plants (interim measure) (new and refurbished) • Short circuit power 3. FACTS devices (STATCOM, SVC etc) • Dynamic voltage control • Reactive power consumption from old wind 4. More stringent grid code regulation turbines and commutation of HVDC LCC • Continuous voltage control (Active power reserves are bought in separate markets and do not give rise to must-run) 5. Retrofitting of wind turbines Must-run is costly • Help in LVRT grid code compliance • Dynamic reactive power support • Ancillary services Source: Energinet.dk (Danish TSO) 6
Retrofitting of wind turbines Wind Turbine Blades/Drivetrain Transformer DFIG/ Grid SCIG Retrofit Unit 7
Dynamic voltage stability considering dynamic reactive power compensation 1.1 1 0.9 Voltage (pu) 0.8 Fault at Vester Hassing substation 1 Fault at Vester Hassing substation 0.7 0.8 Voltage (pu) 0.6 0.6 0.4 0.5 0.2 4 4.5 5 5.5 6 6.5 7 7.5 Time (sec) 4 4.5 5 5.5 6 6.5 7 7.5 Time (sec) 8
Conclusions Wind integration leads to diminishing sources of dynamic reactive power in the grid thus voltage instability/insecurity Retrofitting of wind turbines can be a potential cost effective solution to address the grid stability issue by: • Grid code compliance of wind turbines, particularly old ones • Supplying dynamic reactive power beyond grid code requirement • Supplying grid support ancillary services (steady state and dynamic reactive power) 9
Thank you for your attention Learn more at kkwindsolutions.com Acknowledgements: Zakir Rather (IIT Bombay); Bjørn Rannestad, Kenneth Damm Hansen, Rene Balle (KK Wind Solutions); Flemming Abrahamsen (PowerCon) Energinet.dk (Danish TSO); Aalborg University Denmark; ALSTOM GRID (UK)
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