Abstract
Large-scale integration of renewable generation into power systems invariably affects the system ramping capability. However, the vehicle-to-grid (V2G) concept that allows for using electric vehicles (EVs) as energy storages with the capability of bidirectional energy transfer between the EVs and the grid, can be employed to mitigate the above adverse effect. This paper proposes a game-theory-based V2G coordination strategy that uses EV clusters to improve ramping flexibility in power systems. In the proposed strategy, the V2G concept, representing the interactions between the distribution system operator (DSO) and EV clusters, is formulated as a Stackelberg game. The DSO acts as a leader who decides the charging prices for the buses to which the EV clusters are connected, while the EV clusters simply serve as followers, scheduling their own charging and discharging. This bi-level model is further reduced to a single-level, mixed-integer second-order cone programming (MISOCP) problem based on the Karush-Kuhn-Tucker (KKT) conditions, the strong duality theorem and second-order cone (SOC) relaxation. The performance of the proposed V2G coordination strategy on a modified IEEE 33-bus system connecting EV clusters and PV generations is investigated through simulations, and the results demonstrate that the largest ramp of the system can be reduced by up to 39% when EV clusters are providing flexibility, while the EV clusters can also have greatly reduced charging costs.
Highlights
Power systems have been experiencing a fast increase in renewable energy integration all over the world
In order to study V2G coordination, we propose a dynamic pricing mechanism, which models the distribution system operator (DSO) as a leader deciding the electricity trading prices at the electric vehicles (EVs)-cluster-connected buses, and models the EVs as followers responding to the prices by scheduling their V2G charging and discharging
Such an interaction between the DSO and the communication infrastructure allow the bidirectional flows of power and information between the EV clusters constitutes a Stackelberg game, in which the DSO sets the transaction price to guide the distribution system and the EV clusters
Summary
Power systems have been experiencing a fast increase in renewable energy integration all over the world. Reference [5] depicts California’s daily net load curves, known as “duck curves”, from 2012 to 2020 Such duck curves highlight the rapid ramping of net demand under high penetration of renewables and illustrates that the system, with increasing integration of renewables, confronts the problem of a shortage of ramping capability, threatening the stable operation of power systems. An aggregator is introduced in [16] to integrate a group of small demand response participants into the electricity market for ramping regulation, where the aggregator minimizes its cost by autonomously selecting appropriate programs These studies have shed light on the demand-side approaches for addressing the ramp shortage issue. With the recent advances in vehicle-to-grid (V2G) technology, a cluster of electric vehicles (EVs), with controlled charging and discharging, can act as an energy storage to improve the ramping flexibility of the power system that experiences the aforementioned ramping shortage issue under high renewable penetration scenarios. In order to study V2G coordination, we propose a dynamic pricing mechanism, which models the DSO as a leader deciding the electricity trading prices at the EV-cluster-connected buses, and models the EVs as followers responding to the prices by scheduling their V2G charging and discharging
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