Life Needs Power, Hannover Messe 2017 Inertia in Future Electrical Power Systems Challenges and Solutions Dr. Ervin Spahic siemens.com/energy-management
Motivation Challenge of reduced synchronous generators Current situation: Conventional power plants deliver energy & ancillary services Future development: Significant increase of energy from renewables Thermal and nuclear power plants retirements and shut down due to new environmental policies Transmission system stability requirements: Frequency control i.e. inertia Voltage control i.e. reactive power Short circuit power Higher volatility and potential instabilities of the system need to be mitigated by transmission grid strengthening Page 2
Frequency Stability and Inertia challenge Today s Trends Frequency Stability Examples ᐅ Disconnection of large synchronous generation ᐅ Large frequency deviations can cause severe supply interruptions ᐅ Renewable generation do not contribute to system inertia and frequency control today ᐅ Reactive power reserve for voltage control is reducing Inertia Generation Load ᐅ Over- and underfrequency situations can be critical ᐅ Low inertia systems are sensitive to power unbalances due to high rate-of-rise of frequency (ROCOF) Frequency Time Example: Germany Generation trip Example: Ireland Trip of interconnecting lines Page 3
Inertia in Germany, Great Britain, Italy and Spain today and 2030 Inertia (GWs) 3000 2500 2000 1500 1000 500 Germany, Great Britain, France, Italy and Spain year 2030 year 2015 0 0 8760 sorted hours per year Page 4 Inertia (GWs) 450 400 350 300 250 200 150 100 50 0 year 2030 Great Britain year 2015 0 sorted hours per year 8760
Operation philosophies of today s networks are based on synchronous generation and their rotating masses Frequency stability ᐅ Generation and load has to be balanced ᐅ Frequency has to be controlled within operation limits after large disturbances ᐅ Power plants with synchronous generators naturally contributes to inertia and participate in frequency control ᐅ Three types of mandatory frequency response services ᐅ Inertial response (few seconds) ᐅ Primary response (tens of seconds) ᐅ Secondary response (up to minutes) Page 5
Exemplary critical frequency trajectory National Grid, UK, 27 th of April 2014 Frequency stability limitations ᐅ Large unbalances cause positive and negative frequency deviations ᐅ Under- and overfrequency fnadir leads to ᐅ load shedding ᐅ generator trip ᐅ black out ᐅ High rate of change of frequency ROCOF leads to ᐅ tripping of ROCOF relays of generators to avoid pole transient instability and subsequent black out 50,1 50,0 49,9 49,8 49,7 49,6 49,5 49,4 Frequency (Hz) normal operation Critical ROCOF fnadir disturbance event primary frequency control response 11:37:15 11:37:21 11:37:27 11:37:33 11:37:39 11:37:45 11:37:51 11:37:57 11:38:03 11:38:09 11:38:15 11:38:21 11:38:27 11:38:33 11:38:39 11:38:45 11:38:51 11:38:57 11:39:03 11:39:09 11:39:15 11:39:21 11:39:27 11:39:33 Time (hh:mm:ss) secondary frequency Control response Page 6
First Swing Frequency Stability In future much severe situation Frequency stability limitations Frequency (Hz) ᐅ Large unbalances cause positive and negative frequency deviations ᐅ Under- and overfrequency fnadir leads to ᐅ load shedding 50 Hz 49 Hz ROCOF df/dt today fnadir tomorow load shedding I 10-15 % ᐅ generator trip load shedding II 10-15 % ᐅ black out load shedding III 10-15 % ᐅ High rate of change of frequency ROCOF leads to ᐅ tripping of ROCOF relays of generators to avoid pole transient instability and subsequent black out 48 Hz 47,5 Hz tomorow generator disconnection (blackout)!!! Page 7 Time (s)
First Swing Frequency Stability improvement by: 1. Reducing ROCOF 2. Increasing fnadir Frequency stability limitations ᐅ Large unbalances cause positive and negative frequency deviations ᐅ Under- and overfrequency fnadir leads to ᐅ load shedding ᐅ generator trip ᐅ black out ᐅ High rate of change of frequency ROCOF leads to ᐅ tripping of ROCOF relays of generators to avoid pole transient instability and subsequent black out Page 8
How do we solve the challenges today? Challenges ᐅ Reduced system inertia ᐅ Reduced spinning reserve and primary reserve ᐅ Increasing absolute positive and negative frequency deviations ᐅ Higher ROCOF values Today s solutions ᐅ Increase number of must-run units ᐅ Increase primary reserve power ᐅ Curtailment of renewable generation ᐅ Increasing costs for frequency response measures Disadvantages ᐅ Costs for power plants ᐅ Start-up ᐅ Maintenance ᐅ Fuel costs ᐅ Efficiency & losses ᐅ Environmental impact ᐅ CO2 ᐅ Use of fossil fuels Page 9
Alternative new solution: SVC PLUS Frequency Stabilizer (FS) - Synthetic/Virtual Inertia - siemens.com/energy-management
SVC PLUS Frequency Stabilizer Very fast active power continuous reactive power Page 11
SVC PLUS Frequency Stabilizer Supercapacitors as an add-on to the proven technology of SVC PLUS Technology Proven Technology SVC PLUS (Modular multilevel STATCOM) Add-On: Supercapacitors +/- 50 MW for rated power output up to several seconds Principle Platform: SVC PLUS (STATCOM) based on VSC 1) -technology Supercapacitor tower Features Use Cases @ Transmission Grid 52 kv, 25 MVA Scalable multi-level converter design Storage based on Supercapacitors Rated power output: several seconds discharge Programmable control algorithms, independent from frequency deviation Fast dynamic voltage & frequency control and providing synthetic inertia Support HVDC LCC @ weak AC grids Grid code compliance for grid access of non-synchronous power generation (e.g. wind, PV) Power oscillation damping Page 12 1) Voltage Source Converter
SVC PLUS Frequency Stabilizer Layout of entire 50 MW station Cooling Supercapacitor towers Converter incl. building HV switchyard Power HV/MV transformer Reactors MV switchyard Supercapacitor s building Control room incl. building 50 MW solution SVC PLUS Frequency Stabilizer Battery storage Footprint (p.u.) 3300 m2 20000 m2 Significantly smaller footprint and costs compared to battery solution with same rated power Page 13
SVC PLUS Frequency Stabilizer Impact on primary reserve and possible benefits ᐅ Example on the detailed All-Island grid of Ireland for summer 2022. Load at ~2500 MW. Renewables 65%. Tripp of 500 MW HVDC connection) ᐅ SVC PLUS FS of 50 MW has the same impact on the first swing frequency as a coal power plant of 550 MVA! ᐅ fnadir improvement of >0,1 Hz! ᐅ ROCOF reduction ᐅ SVC PLUS Frequency Stabilizer can reduce level of must run units (required for secure operation of the system) and reduce primary reserve ᐅ Fast response time. Time needed for synthetic/virtual inertia: ᐅ For 4 Hz/s full power at 49,6 Hz means activation time of 100 ms!!! Fulfilled!!! 48,9 Frequency (Hz) 50,1 49,9 49,7 49,5 49,3 49,1 base case 2 3 4 5 6 7 8 9 10 Time (s) Coal power plant (550 MVA) SVC PLUS FS (50 MW) Gas power plant (200 MVA) Synchronous condenser - SynCon (225 MVA) Page 14
SVC PLUS FS Frequency Stabilizer Main advantages ᐅ Proven high-end technology SVC PLUS and innovative application of supercaps 50,0 49,8 ᐅ Cost effective solution increase security of supply 49,6 ᐅ Very fast response, rated active power output of several seconds ᐅ Reduce costs for must run units and primary reserve Frequency (Hz) 49,4 49,2 49,0 SVC PLUS FS for frequency suppport ᐅ Improve power quality and dynamic voltage support 48,8 0 10 20 30 40 Time (s) ᐅ Simultaneous active and reactive power contribution ᐅ Environmental friendly featuring no CO 2 emissions ᐅ Prevent blackouts ᐅ Enabler for the Energiewende Page 15
Thanks for Your attention! Dr. Ervin Spahic Head of Future Technologies Transmission Solutions EM TS PLM TSP FT Siemens AG Freyeslebenstr. 1 91058 Erlangen Phone: +49 (9131) 7 26 099 ervin.spahic@siemens.com Page 16