Aggregation of plug-in electric vehicles in electric power systems for primary frequency control

Transcription

1 Aggregation of plug-in electric vehicles in electric power systems for primary frequency control Seyedmahdi Izadkhast Researcher at Delft University of Technology

2 Outline Introduction Plug-in electric vehicles Power system ancillary services like primary frequency control Primary frequency control by plug in electric vehicles Case study and simulation scenarios Simulation results Conclusions References

3 Introduction - PEVs Over the past years, new plug-in electric vehicles (PEVs) registrations have been notably increased in Europe 3/23

4 Introduction - PEVs Currently, 1000 charging points in Amsterdam Expected to have 4000 charging points by 2018 in the city This largely affects the operation and control of electric power infrastructure within cities like Amsterdam 4/23

5 Introduction - PEVs From electrical grid point of view, a single PEV consists of two main components: Battery pack Battery charger system Battery pack Battery charger system Plug-in electric vehicle Grid 5/23

6 Introduction - PEVs PEVs are interesting options for electricity services 1. PEVs store a considerable amount of electrical energy using battery pack PEVs become viable options for energy-based services 2. PEVs using battery charger system control active and reactive power within a few tens of milliseconds PEVs become interesting options for power-based services 6/23

7 Introduction Ancillary Services PEVs have a great potential to proivde a wide range of power system ancillary services from short time scale to long time scale Electricity services provided by PEVs Very short time scale ~milliseconds Short time scale ~seconds Medium time scale ~minutes Long time scale ~hours Transient voltage stability Ancillary service time scale Capacity power based service Black start Primary frequency control Local voltage management Secondary frequency control Power & energy based service Energy based service Islanded operation and emergency backup Tertiary frequency control Congestion and local operational constraint management 7/23

8 Introduction Frequency Control Frequency is an indicator of energy balance in power systems If total electricity supply is less than the total demand Frequency drops If total electricity supply is greater than the total demand Frequency rises 8/23

9 Introduction Frequency Control Frequency control in power systems Inertia Primary frequency control Instantaneous balance Secondary frequency control Tertiary frequency control 9/23

10 Introduction Primary Frequency Control Over the past decades, PFC has been only procured by conventional generating units In the past years, PFC response has been notably reduced in power systems due to large-scale introduction of renewable energy sources GRID OPERATOR 10/23

11 Introduction Primary Frequency Control Nowadays, PFC can be provided by PEVs next to conventional generating units PEVs are much faster compared to conventional generating units GRID OPERATOR 11/23

12 Introduction Primary Frequency Control PEVs versus conventional generating units Battery charger s time constant (e.g., 30 ms) Thermal unit s time constant (e.g., 4 s) Gas unit s time constant (e.g., 0.4 s) Thanks to the fast-controlled battery charger of PEVs, they are much more promising technologies (ten times faster) for the PFC compared to the conventional generating units 12/23

13 Introduction Primary Frequency Control Typical Frequency control scheme of power systems Frequency deviations due to the mismatch between power production and consumption Load ΔP l f LFC ΔP LFC, c ΔP LFC, pevs Wind farms and solar units Conventional Power Plants PEV Fleets ΔP w ΔP cp ΔP pevs Hs+ D 13/23

14 Primary Frequency Control by PEVs Research Challenge Modelling a large number of plug-in electric vehicles for PFC can significantly be time-consuming and computationally complex. Research Objective To reduce computational complexity, an aggregate model of PEVs are introduced and developed. 14/23

15 PEV Characteristics for PFC Three essential PEV operation modes: Disconnected mode Idle mode Charging mode A single PEV technical characteristics: Minimum desired state of charge (SOC) of PEV owners Battery charger maximum power (unidirectional or bidirectional) Constant current and constant voltage charging modes of PEVs 15/23

16 An Equivalent Model of A Single PEV To incorporate the PEV characteristics, a participation factor according to PEV state of charge was introduced and calculated for a single PEV 16/23

17 An Aggregate Model of A Single PEV An average participation factor of PEVs has been calculated taking into account the probability distribution functions of SOC in the fleet 17/23

18 Case Study Of Spanish Power System Including PEVs The worst case for PFC analysis has been defined when the system primary reserve is minimum The frequency disturbance of 0.05 pu (1 GW in Spain) is applied at t=0 s PEV fleet parameters 5.14 kw 55% 0.5% Number of PEVs 22,800 Battery charger topology Bidirectional 18/23

19 Scenario 1 For Spanish Power System To evaluate the performance of the PEV fleet compared to the conventional units: Simulation scenario 1.1 PEVs do not participate in PFC, and the conventional units mainly provide the PFC. Simulation scenario 1.2 PEVs along with the conventional units participate in the PFC. 19/23

20 Simulation Results of Scenario 1 PEV fleet participation improved the minimum system frequency: Scenario 1.1: fmin = 0.33> 0.3 Hz Scenario 1.2: fmin = 0.19 Hz. 0 x 10-3 Without participation of PEVs in PFC Scenario 1.1 With participation of PEVs in PFC Scenario F (pu) Time (s) 20/23

21 Scenario 2 For Spanish Power System To evaluate the effect of PEV battery charger topology: Simulation scenario 2.1 PEVs participate in PFC with unidirectional battery chargers. Simulation scenario 2.2 PEVs participate in PFC with bidirectional battery chargers. 21/23

22 Simulation Results of Scenario 2 PEV fleet participation improved the minimum system frequency: Scenario 2.1: fmin = Hz > 0.3 Hz Scenario 2.2: fmin = 0.15 Hz > 0.3 Hz F (pu) x Scenario 2.1: 0 % bidirectional - 100% unidirectional Scenario 2.2: 100% bidirectional - 0% unidirectional Time (s) 22/23

23 Conclusions PEVs can effectively improve the system frequency response following the disturbance, and furthermore show better performance than conventional units for PFC. PEV constraints such as battery charger s power limitations, battery state of charge, and constant current and constant voltage charging modes of PEVs can remarkably affect PEV fleet performance for PFC. The average participation of PEVs might be significantly reduced during the day. 23/23

24 Conclusions The unidirectional or bidirectional battery charger topologies affects the performance of the PEV fleet for PFC, and PEVs equipped with BBC have better performance than PEVs equipped with UBC. An aggregate model of PEVs, which could flexibly incorporate the aggregate PEV technical constraints, was proposed and formulated based on the arithmetic average technique to notably reduce computational complexity. 24/23

25 References P. Kundur, N. J. Balu, and M. G. Lauby, Power system stability and control, vol. 4. McGraw-hill New York, S. Izadkhast, P. Garcia-Gonzalez, and P. Frías, L. Ramirez-Elizondo, and P. Bauer, An aggregate model of plug-in electric vehicles including distribution network characteristics for primary frequency control, IEEE Transactions on Power Systems, vol. 31, no. 4, pp Jul S. Izadkhast, P. García-González, and P. Frías, An aggregate model of plug-in electric vehicles for primary frequency control, IEEE Transactions on Power Systems, vol. 30, no. 3, pp May S. Izadkhast, P. García-González, and P. Frías, L. Ramirez Elizondo, and P. Bauer, Aggregation of Plug-in Electric Vehicles in Distribution Networks for Primary Frequency Control, IEEE International Electric Vehicle Conference, Florence, Italy, DEC 2014.

26 Thank you!