Dynamic Reactive Power issue in Wind Integrated Power Systems and LVRT Compliance of WPPs

Transcription

1 Dynamic Reactive Power issue in Wind Integrated Power Systems and LVRT Compliance of WPPs RE integration workshop, Chennai January 23, 2018 Zakir H Rather, IIT Bombay zakir.rather@iitb.ac.in Wind farm in chitradurga-pic taken from IREDA ppt

2 Journey of wind power at global level 2 Source: GWEC

3 Indian Power System and 2022 RE target 3 Installed capacity 330 GW (1.36 GW in 1947) ; Peak demand 150 GW 300 million people do not have access to electricity. Small Hydro, 5 GW Biomass, 10 GW RE GW at 100 m height Target by 2022 is 60 GW of wind and 100 GW of solar PV 90% of wind potential is in the Southern and the Western region Growth path of wind power (GW) Wind, 60 GW Solar, 100 GW Large scale solar Solar rooftop

4 Challenges of variable RE (vre) integration 4 Technical Lack of transmission infrastructure, grid stability, variability of RE sources, weak grid, estimation of effective turbine capacity etc. Regulatory Complexity of subsidy structure and involvement of too many agencies Industrial barriers Lack of investment, skilled manpower Wind resource data collection Wind potential calculation requires proper data of wind speed at site. Social and environmental issues Noise pollution from wind farm affects the local region. Deforestation for carrying wind turbine and blades

5 vre integration-technical issues 5 Increased Flexibility requirement (variability issue) Wind-driven displacement of conventional synchronous power plant low synchronous inertia and possibly increased operating reserves Diminishing reactive power reserve and short circuit power Renewable Energy curtailment Emerging issues: Post-fault delayed active power recovery from wind turbine/plant

6 Impact on reactive power capability: Ireland 6

7 Evolution of LVRT 7 LVRT curve is representative of worst case realistic voltage recovery profile that may occur once a power system recovers from lowest voltage point. Factors affecting LVRT requirements: Current and anticipated wind penetration levels Strength of grid Type of load in the system (predominance of induction motor load leads to poor voltage recovery) Islanding of system Dynamic voltage support devices in the system and plant reactive power headroom LVRT requirement

8 LVRT priority Voltage (p.u.) Voltage (p.u.) LVRT curve for Energinet.dk, Denmark Time(ms) Time (ms) LVRT curve for Tennet TSO, Germany LVRT curve as per EirGrid and Indian wind grid code EirGrid: T= 625 ms, Vpf=0.9 pu; Vf= 0.15 pu IEGC (CERC): T =table below, Vpf= 0.8 pu; Vf= 0.15 pu Table: T for various voltage levels in India Nominal rated voltage (kv) Fault clearing Time (millisecond) V post fault (kv) V fault (kv)

9 LVRT Issues 9 IEC /IEC Field testing? What about old WTGs? How to ensure WTGs are LVRT compliant after a period of operation? How to monitor LVRT compliance? Which LVRT priority?

10 Wind driven displacement of Conventional Power Plants (CPPs)-Danish power system 10 Offshore WF Source: Energinet.dk

11 Impact on grid security: Danish case study kv Vester Hassing substation 1 Fault at Vester Hassing substation V oltage (pu) DCHPs trip VSWTGs trip Old wind turbines trip Rather et al., 2015 Chengxi liu et al., Time (sec)

12 Reactive power support from must run CPPs in the Danish grid 12 Short circuit power Dynamic voltage control Reactive power consumption by old wind 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) Must-run was costly Source: Energinet.dk (Danish TSO)

13 Voltage stability considering dynamic reactive power compensation in 2030 Danish grid Voltage (pu) Refurbished SCs 0.9 New SCs 0.8 STATCOM, SVCs 0.7 Dynamic Q support from WPPs 0.6 Fault at Vester Hassing substation Time (sec) Rather et al., 2015

14 14 Potential solutions to address lack of dynamic reactive power reserve in RE integrated system Infrastructure reinforcement: synchronous condensers, FACTS devices such as SVC, STATCOM, TSSC Procurement of dynamic reactive power through ancillary service market Energinet.dk

15 Operating WPP beyond grid code requirement 15 Asynchr onous Motor 345 MW M 6.6 kv Static Load 207 M W, 80 M VAR 26.4 kv 345 kv 345 kv PCC 154 kv fault 33 kv 13.8 kv WTG 5 WTG 1 0 WTG 1 5 SG 1 SG 2 SG 3 SG 4 SG 5 SG MVA 150 MVA 200 MVA 5 M W WTG 4 WTG 9 WTG kv 2.3 kv 33 kv WTG 3 WTG 8 WTG 1 3 P Wind WPP angle 90 V PCC 0 WTG 2 WTG 7 WTG 1 2 WTG 1 WTG 6 WTG 1 1 Qca p V P V PCC _ Σ V com Deadband Q WPP_cap Π K Qmin limiter Qmax Q WPP_ref K 1 K 2... Q WTG1_ref Q WTG2_ref Q K n Q WTGn_ref ΔVP CC

16 Post-fault delayed active power recovery Rather et. al, 2017

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18 LVRT priority: active or reactive power? Voltage at TW1(WPP1 terminal) Grid frequency Active power from WPP Active and reactive current 19