A Multi Charging Station for Electric Vehicles and Its Utilization for Load Management and the Grid Support IEEE Transactions on Smart Grid, Vol. 4, No. 2, June 2013 Mukesh Singh, Student Member, IEEE, Praveen Kumar, Member, IEEE, and Indrani Kar, Member, IEEE Pei-Chi Hsieh

Outline Introduction Modelling of The System Problem Definition Result and Discussion Conclusion 2

Outline Introduction Modelling of The System Problem Definition Result and Discussion Conclusion 3

Introduction This intelligent interaction between the grid and EVs is coined as Vehicle to Grid (V2G). The V2G concept facilitates a large pool of EV batteries to store the energy during off-peak hours and inject it back to the grid during peak hours. The authors have proposed the concept of a charging station to support the grid in terms of valley filling and peak shaving through an aggregation of EVs. 4

Outline Introduction Modelling of The System Problem Definition Result and Discussion Conclusion 5

Modelling of The System Vehicle-to-grid based MCS connected to the distribution grid. 6 (Multi Charging Station) PCC: Point of common coupling Positive Power / Negative Power

Modelling of The System Block diagram representation of a CS and the individual battery control. 7

Modelling of The System Battery The model of the battery is taken from the simpower of the matlab simulink library. The batteries are charged when the node voltage is high and the batteries are discharged when the voltage of the node is low taking into account their SOC. 8

Modelling of The System Distribution Network Radial distribution system of a substation of Guwahati city. 9 (500 kVA) (5 MVA)(500 kVA)

Outline Introduction Modelling of The System Problem Definition Result and Discussion Conclusion 10

Battery Control Individual Battery Control and Its Algorithm for Charging and Discharging 11 The power required/available to charge/discharge the jth battery of ith CS The voltage of the jth battery of ith CS The current Ampere Hour (AHR) of the jth battery of ith CS The rated AHR of the battery The difference of the current SOC and SOC limit The current SOC The SOC limit The current which flows between the battery and the grid

Battery Control (cont.) Flow chart for controlling the flow of power in individual battery 12

Power Distribution Distribution of Power Among CSs and Batteries 13 The power which should be drawn/supplied from/to the node The net power exchanged at the ith CS The available/required batteries energy of the ith CS The total energy available/required by the MCS The charging/discharging efficiency of the system The energy available/required by the jth battery of the ith CS the power available/required by the jth battery of ith CS

Fuzzy Logic Fuzzy Logic Based V2G Controller Linguistic variables : L(Low), M(Medium), H(High) NL(Negative Low), NM(Negative Medium), NH(Negative High) PL(Positive Low), PM(Positive Medium), PH(Positive High) 14

Fuzzy Logic (cont.) Membership functions for three inputs and one output of the V2G Controller

Fuzzy Logic (cont.) Membership functions for three inputs and one output of the V2G Controller If node voltage is 0.95 p.u, energy availability is high and the duration is high, then FLC will decide the power flow to be negative. It infers that the batteries have to discharge their stored energy

Critical Cases Some Critical Cases For The V2G Controller 17

Assumption and Background The total number of EVs: 200 (CS: 150, transit/idle: 50) 18 (40 EVs) Low: SOCinit < 40% Medium: 40% <= SOCinit < 70% High: SOCinit >= 70% In real scenario, EV’s battery may arrive below user’s specified SOC limit due to extra driving.

Assumption and Background(cont.) 19 x km 10% of SOC is assumed to be consumed when an EV moves from one CS in previous time slot to the other CS in next time slot. EVs coming from ‘Transit’ have same SOC initial. Off-peak hour Peak hour

Outline Introduction Modelling of The System Problem Definition Result and Discussion Conclusion 20

Result and Discussion Case I: three time slot Case II: variable load on 24 hours 21

Case I(a): Off-peak hours (9:00~17:00) 22

Case I(b): Peak hours (17:00~22:00) 23

Case I(c): Off-peak hours (22:00~09:00) 24

Case I(d) 25

Case I(e) 26

Case II 27

Outline Introduction Modelling of The System Problem Definition Result and Discussion Conclusion 28

Conclusion The purpose of designing the MCS is to coordinate the flow of power between the grid and the batteries in a controlled fashion using FLC. A suitable algorithm has been designed which takes into consideration and SOC of the batteries. The proposed MCS can stabilize the grid by valley filling and peak shaving. 29

Thanks for your listening. 30