PSO project EaseWind Enhanced ancillary services from Wind Power Plants Anca D. Hansen DTU Wind Energy
Background PSO project EaseWind (2011-2014) Enhanced Ancillary Services from Wind Power Plants Partners: Vestas Technology R&D DTU Wind Energy DTU Compute AAU IET Objective to develop and asses technical solutions for enabling wind power to have similar power plant characteristics as conventional generation units. Temporary frequency response (TFR) Synchonising power (SP) Power oscillation damping (POD) 2 1 September 2015
Ancillary services from wind power plants Until now: the stability in the power system is ensured by ancillary services from the conventional power plants Future: in order to keep the system stable without conventional power plants, wind power must be able to provide ancillary services The ancillary services from wind power plants are supported by communication and control at the power plant level. WPP Controller Communication Measurements Wind Power Plant (WPP) Point of Connection 3
Modelling of Ancillary Services Set points from grid operator Measurements in PCC WPP control level Power set points Feedback signals WT control level Ancillary services Complexity? Default Controls Frequency control Voltage control Active power control Reactive power control + New control services: Temporary frequency response Syncronising power Power system damping Adjusted IEC standard model Focus on: overall control architecture and algorithms at WPP level integrate the ancillary services in WPP level assess WPP capability to provide ancillary services within its control and mechanical limits. 4
Enhanced ancillary services Grid Frequency f df / dt TFR controller P TFR 50Hz WPP Power Output P Time P actual Time Load Angle SP controller P SP WPP power output Time Time Active Power or Current Magnitude I Q POD Time P POD controller PPOD WPP Active or Reactive Power output [ Tens of sec] Active Power Actual or Curtailed Time [ Tens of sec]
Generic 12 Bus system (adapted from IEEE & CIGRE ) G1 768 MVA Bus 9 (Slack) TG1 L1 300 MW @0.85 Bus 1 L2 250 MW @0.9 Line 1-6 Bus 2 Bus 10 TG2 G2 Area 1 L6 640 MVA Line 1-2 Line 2-5 100 km 400 km Bus 6 L5 TG4 Area 2 Bus 12 Bus 5 C5 G4 500 MVA Area 3 Bus 7 Bus 8 AT1 AT2 Line 7-8 600 km L7-100 MVAR 150 MW @0.95 Line 4-6 300 km 300 km 100 MW @0.9 Area 4 WPP1 40 MVAR Line 4-5 150 km L3 350 MW @0.95 L4 300 MW @0.85 WPP2 Bus 3 13.8-15 kv 230 kv 345 kv Bus 4 C4 200 MVAR TG3 Bus 11 Line 3-4 (double) G3 100 km 400 MVA WPP3 Ancillary Services Event TFR POD SP Test cases Focus on Power System Loss of the largest gen. unit Large frequency excursion Short circuit event Load increase event Electromechanical oscillations Voltage/Rotor angle variations Cases 0% 20% 50% CPP (GW) 2.00 2.00 1.65 Load (GW) 1.45 1.85 1.85 WPP (GW) 0.00 0.40 1.00 Different online wind power penetrations: up to 20%, the conventional generator size is kept constant while wind power and loads are increased. for more than 20% wind penetration, conventional generator units are decommissioned while the load demand is kept at 20% penetration level Online wind power penetration the amount of the load demand which is provided by online wind power Simulations are performed allowing 10% curtailment for wind turbines.
Frequency drop at different wind power penetrations Frequency (pu) 1.010 1.005 1.000 0.995 0.990 0.985 0.980 0.975 0 5 10 15 20 25 30 Time (sec) 0% wind (base case) 5% wind (100MW wind power) 10% wind (200MW wind power) 20% wind (400MW wind power) 30% wind (600MW wind power) 40% wind (750MW wind power) 50% wind (850MW wind power) Power system response during large frequency excursion due to loss of the largest in-fed unit. Frequency excursion increases with the increase in wind power penetration. System inertia decreases with displacement of conventional generator units in order to accommodate more wind power. Loss of the generation may lead to load shedding as the frequency hits the load shedding limit. To avoid the load shedding, wind power should provide additional power similar to the synchronous generators 7
Temporary frequency response from WPPs Loss of the largest unit /different wind power penetrations 20% wind power penetration: only WPP1 connected no displacement of CPPs Basic case: power system without WPPs 50% wind power penetration: WPP1, WPP2 and WPP3 connected Displacement of CPPs WPPs connection decreases inertia Freq. exceeds the allowed limit without implementing additional control
WT temporary frequency response capability
WPP synchronising power capability
WPP power oscillation damping capability I Line Q POD 50% wind power penetration P Line POD controller P POD Q POD different input/output signal pairs same POD controller parameters in all WPPs POD activated in one WPP POD activated in all WPPs Need for coordination and parameter tuning of PODs
Summary - Reflections on WPPs technical capabilities WPPs can provide enhanced ancillary services emulating synchronous generator (inertia/fast frequency response, synchronising power and power oscillating damping) but is this the optimal solution in future systems? Still many questions without answer yet need to develop algorithms for: Services allocation : o is it appropriate to run in parallel with multiple functionalities? o which service should be prioritised? o can it contribute to the overall success criteria of meeting the power system needs for stabilising features? o can it minimise the needed reserve power allocation from wind (curtailment)? Parameters tuning o how is this implemented in practice for different power system scenarios? Service algorithm o how to select the input/output pair for POD control, for a given network? Service coordination o should all WPPs provide services? o which WPP is most suitable to provide a specific service? Need for strategies for ancillary services from wind and other sources to ensure security of systems with increasing levels of non-synchronous generation
RePlan - new ForskEL project Ancillary services from renewable power plants http://www.replanproject.dk/ P, Q Offshore ReGenCon Communication Transmission Grid Partners: DTU Wind Energy DTU Elektro AAU ET AAU Wireless Communication Networks Vestas Technology R&D Onshore ReGenCon Communication P, Q P, Q Distribution Grid P, Q Overall objective: to enable a resilient power system by developing technical solutions for the provision of ancillary services by renewable power plants Focus: develops controllers for the delivery of ancillary services from WP and PV plants, incorporating communication properties suitability to coordinate the provision of the services from WP and PV plants impact of communication and power availability forecast error in providing coordination and ancillary services