JULY 2008 Campus da FEUP Rua Dr. Roberto Frias, 378 4200-465 Porto Portugal T +351 222 094 000 F +351 222 094 050 www@inescporto.pt www.inescporto.pt Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids J. Peças Lopes / A. Guimarães Madureira 2008
Introduction: What Has to Change? Driving forces for the future development of the electric power systems: 1) Environmental issues: meet Kyoto protocol targets (reduce emissions by replacing fossil generation by zero emission generation, reduce network losses), increase social responsibility and sustainability, minimize visual impacts and land use. 2) Replacement of old infrastructures (generation and grid) 3) Security of Supply 4) Increase quality of service (more automation and remote control) 5) Electricity market liberalization (energy and services) 1) Increase renewable generation,, exploit clean coal technologies, CCGT and others 2) Increase Distributed Generation 3) Demand Side Management (increase load consumption efficiency) 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 2
What Has to Change? Increasing Renewable Generation Stabilized technologies 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 3
What Has to Change? Increasing Renewable Generation Some promising technologies 750 kw 750 kw 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 4
Expected Contribution of Renewable Energies for Electricity Generation Some scenarios: Prospects for renewable electricity generation in EU 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 5
What Has to Change? New Grid Management New paradigms are under development Breaking the Rules Central power station Yesterday Tomorrow: distributed/ on-site generation with fully integrated network management Trans mis s ion Network House Dis tributio n Network Storage Storage Power Local CHP plant quality device Photovoltaics power plant Flow Control Storage Storage Wind power plant Power quality device House with domestic CHP Current distribution grid Management practice needs to be changed from passive to active DG control paradigm Factory Commercial building 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 6
New Solutions: New management / Control Structures Wind park dispatch centers acting as virtual power plants should be developed and installed Solution already adopted for Portugal: Wind Generation Tender 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 7
Storage as Way to Help Managing the System Storage technologies: Short term storage: flywheels, super-capacitors, SMES devices Medium term storage (to keep energy balance, help in frequency control, costumer peak shaving): Compressed air, flow batteries, hydro pumping storage Long term storage (transferring energy from one period to another): hydro pumping storage 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 8
New Solutions: MicroGrid - A Flexible Cell of the Electric Power System MG Hierarchical Control: MGCC, LC, MC Communication infrastructure PV MC LC MC LC Microturbine MC LC LC Micro Wind Generator MGCC MC Storage Device LC MC Fuel Cell 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 9
Test System in the MATLAB/Simulink Simulation Platform SSMT Grid Side Converter SSMT Mechanical Part VSI + STORAGE Machine Side Converter Frequency Control SOFC Microturbine WI D GE ERATOR PV PMSG LOAD 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 10
Results from Simulations Islanding Operation MicroGrid Frequency and VSI Active Power MicroGrid Frequency and VSI Active Power 50.2 50 Frequency (Hz) 49.8 49.6 49.4 49.2 0 50 100 150 200 250 50 VSI Active Power (kw) 40 30 20 10 0-10 -20 0 50 100 150 200 250 Time (s) 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 11
Results from Simulations Islanding Operation Active Power from Controllable Microsources Active Power from Controllable Microsources 30 25 20 Active Power (kw) 15 10 SSMT1 & SSMT2 5 SSMT3 SOFC 0 0 50 100 150 200 250 Time (s) 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 12
MicroGrids Black Start Sequence of Actions During MicroGrid Black Start Disconnect all loads and sectionalize the MG so that some microgenerators may feed its own loads Creation of small islands inside the MG Start energizing the LV cables and the distribution transformer (using the storage device) to comply with MG safety earthing guidelines Synchronize the other microsources with the LV network Verify the synchronization conditions Connect controllable loads taking into account the available storage capability (including motor load start-up) Connect non-controllable generators Connect as much load as possible Reconnect to the main grid 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 13
Results from Simulations Black Start An Overview of the Service Restoration Procedure An Overview of the Service Restoration Procedure Frequency (Hz) Active Power (kw) Active Power (kw) 50.4 50.2 50 49.8 49.6 90 100 110 120 130 140 150 160 170 180 190 200 210 220 40 20 0 MG main storage -20 90 100 110 120 130 140 150 160 170 180 190 200 210 220 SSMT 1 60 SSMT 2 SSMT 3 40 20 0 load connection WG connection PVs connection Motor load start up 90 100 110 120 130 140 150 160 170 180 190 200 210 220 Time (s) 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 14
Multi-MicroGrids New concept Multi-Microgrids 150 kv Sk=3000 MVA 150/21 kv, 50 Hz, 40 MVA uk=16%, Dyn1 12 Ω 630 kva 630 kva Central storage MW, MWhr to be determined 630 kva 2x630 kva 630 kva 2x630 kva 400 kva 400 kva 250 kva 20 kv Typical rural MV/ LV substation LV network with CHP 400 kva 630 kva 1000 kva 400 kva 630 kva 1000 kva 400 kva 400 kva 250 kva 400 kva LV network with CHP 400 kva 250 kva 160 kva 0.4 kv 630 kva 630 kva 1000 kva 1000 kva 250 kva 20 kv 0.4 kv Typical urban MV/ LV substation 400 kva 2000 kva 400 kva Loop section (N.O. switch) 160 kva 250 kva 160 kva 160 kva 250 kva 160 kva GS 2.5 MVA GS 0.75 MW 1.5 MW Small hydro Wind farm G GS GS CHP 6x1.5 MW 1 MVA 2x1 MW Requires a higher level structure, at the MV level, consisting of LV Microgrids and DG units connected on several adjacent MV feeders Microgrids, DG units and MV loads under DSM control can be considered as active cells, for the purpose of control and management 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 15
Dynamic Equivalents for MicroGrids External subsystem Study subsystem MicroGrid Dynamic equivalent 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 16
Results from Simulations Dynamic Equivalents MG total active power (kw) MG total reactive power (kvar) MG slow dynamics active power (kw) Frequency (Hz) 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 17
Impact of MicroGrids on Local Reliability Indices Reliability indices Influenced by The ratio between the internal generation and load Consumers inside µgrids λ is reduced U is reduced NDE is reduced The probability of unsuccessful isolation from Distribution Network The probability of shutting down the whole µgrid after an internal fault Consumers outside µgrids λ is not affected U may be reduced NDE may be reduced The time to restore the µgrid after a complete shut down U is reduced when µgrids help in the reconfiguration of the MV network after a fault 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 18
Influence of Microgeneration in Generation Adequacy Adding up µchp capacity obviously reduces risk 2.5 LOLE (h/yr) 2 1.5 1 0.5 0 0 250 500 750 1000 1250 1500 1750 2000 uchp (MW) 3 kw - f = 0.10 We may calculate the possible reduction in reserve to maintain the previous risk level Capacity Credit 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 19
Vehicle-2-Grid (V2G) Concept Electric vehicles plugged in a dispersed manner over the LV grid The Vehicle Controller (VC) has to regard the vehicle as a storage device that responds to both technical and economic signals constrained use VC MC LC MGCC Electric Vehicles used as storage Bidirectional power exchange with the grid Charging can be controlled accordingly with the markets Provision of ancillary services 2008 Large Scale Integration of Renewable Power Sources and Microgeneration / Microgrids 20