Impact on Power System Flexibility by Electric Vehicle Participation in Ramp Market

Abstract

This paper investigates electric vehicle (EV) participation in the flexible ramp market. We take into account EV stochastic mobility, and evaluate impact on power system reliability and flexibility. Based on dynamic programming, the model deals with uncertainties and variations of net load, as well as EV charging requirements. Markov process is utilized in estimating the aggregated power capacity of EVs. Two participation modes are analyzed: 1) EV direct provision of the ramp product; and 2) EV cooperation with the conventional generator. Moreover, we propose new indices to evaluate power system flexibility. Finally, numerical experiments are conducted to validate the proposed approach and illustrate how EV involvement into the ramp market can improve power system reliability and flexibility.Index Terms-Electric vehicles (EVs), flexibility, ramp market, reliability. NOMENCLATURE λVehicles' arrival rate into the traffic system. μ Reciprocal of the mean travel time. m Maximum capacity of the traffic system. γ ij Transition rate from states i to j of the Markov model. E sij+ Discharging energy per electric vehicle (EV) under states i or j. ω sij+ Mean discharging energy per EV under states i or j. σ sij+ Standard deviation of the discharging energy per EV under states i or j. F Z+ (z) Cumulative distribution of EV available discharging energy. f Z+ (z) Probability density function of EV aggregated discharging energy. C EVtotal EV total battery capacity in one large area. q Average energy per EV to finish the travel. Energy + EV aggregated energy capacity for discharging. Energy − EV aggregated energy capacity for charging. h Time duration of EV charging/discharging. Power + EV aggregated discharging power. r + max Maximum discharging rate for one EV. p max EV+ EV aggregated discharging power capacity. p EVG+ EV discharging power in the market. p EVG− EV charging power in the market. FRU EV EV ramp up service in the market. FRD EV EV ramp down service in the market. G Set of the on-line generators. p t Gi Generation output of generator i at time t. FRU t i Ramp up service of generator i at time t. FRD t i Ramp down service of generator i at time t. C FRUi Cost of the ramp up service for generator i. C FRDi Cost of the ramp down service for generator i. C EVG Cost for EVs to provide the energy service. C EVFRU Cost for EVs to provide the ramp up service. C EVFRD Cost for EVs to provide the ramp down service. P t L Net load at time t. p t EVG− EV charging load at time interval t. p min Gi Minimum generation of the generator i. p max Gi Maximum generation of the generator i. R i Ramp rate of the generator i. t Time interval period to ramp up or down. D t FRU System requirement for ramping up at time t. D t FRD System requirement for ramping down at time t. E t EV EV aggregated energy at time t. η + EV discharging coefficient. η − EV charging coefficient. C req EV energy requirement.

Towards Flexibility Trading at TSO-DSO-Customer Levels: A Review

“…However, recent studies proved that large-scale aggregators aggregating EVs, prosumers, DR, storage-based resources as well as WPPs could also provide the needed flexibility at TSO-level. For example, it has been proven proved that the use of EV aggregators as flexible resources would help the system deal with more uncertainty and variability within the probability of 99% [26], and according to results obtained by [30], participation of WPPs as flexible resources can reduce the overall cost of the system by 5.5%. Flexibility products at the TSO level could be divided into FRPs and ancillary services.…”

“…EV's contribution to flexibility services provision has been considered [26]. Two different types of EV participation have been considered [26]. In the first case, aggregated EVs only participated in the ramp markets.…”

“…Also, customers' responsiveness to time-varying prices was analyzed to show how much these resources could contribute to ancillary service requirements. EV's contribution to flexibility services provision has been considered [26]. Two different types of EV participation have been considered [26].…”

“…Storages are also very potential flexibility providers for future TSO needs. References [26,33] stated that the battery energy storage (BES) and plugged-in EVs might be the most suitable options to produce flexible ramping products due to their frequent usage and time-related constraints. Since ramp-based markets are cleared sub-hourly, the time-related limitations of batteries would be relieved.…”

Quantification of Intra-hour Security-Constrained Flexibility Region

“…The provision of flexibility comes from institutional enablers (such as market design [3] and interconnection [5]), flexible generation technology [6], energy storage [7], [8], spinning reserves [9], and additional sources of flexibility (e.g., electric vehicles [10] and demand response (DR) [11], [12]). Especially, hourly DR program is beneficial in reducing the cost of security-based power system scheduling [13], in lowering load payment [14], and in improving the thermal generation flexibility [15].…”