Coordinated Power Control of Electric Vehicles for Grid Frequency Support: MILP-Based Hierarchical Control Design

Abstract

Frequency regulation is one of the most crucial ancillary services that strives to maintain the demand and supply in smart grid setup. The deviations in grid's frequency can be managed efficiently by adjusting the power generation and consumption of supply and demand sides, respectively. Traditionally, frequency support is provided using conventional generators but their usage leads to the emission of harmful gases, degraded heat rate, and associated wear and tear. However, electric vehicles (EVs) can play a significant role in managing demand and supply imbalances in the near future; with their penetration expected to reach 400 billion by 2020. Moreover, EVs have large charging and discharging capacities due to which they can provide instantaneous frequency support. Motivated by these factors, in this paper, a power management scheme has been presented to leverage the participation of EVs for secondary frequency regulation. The proposed scheme uses a 2-level hierarchical control mechanism to attain the following objectives: (1) to minimize the frequency deviations at the grid level; (2) to support bi-directional vehicle-to-grid in accordance with users' power requirements; (3) to generate an optimal schedule for EV's charging and discharging needs; (4) to reduce battery degradation; and (5) to maximize EV's revenue. Using these objectives, the problem of frequency support has been formulated as a mixed integer linear programming problem. The proposed scheme has been evaluated using Mosek solver on real-time data acquired from PJM and CAISO. The results obtained demonstrate the effectiveness of the proposed scheme for providing frequency support in comparison to the existing scheme.