EV/PHEV Bidirectional Charger Assessment for V2G Reactive Power Operation

TLDR

The study reviews single‑phase AC‑DC topologies for EV/PHEV level‑1 and –2 on‑board charging and reactive power support, classifies chargers for future V2G use, and compares charging‑only versus capacitive reactive‑power operation. It evaluates the pros and cons of each topology, classifies chargers by V2G suitability, and analyzes how reactive‑power operation affects dc‑link capacitor demand and ripple current. Reactive‑power operation increases dc‑link capacitor cycling and second‑harmonic ripple but preserves battery state‑of‑charge, yet requires limiting converter output below its rating to avoid excess capacitor stress.

Abstract

This paper presents a summary of the available single-phase ac–dc topologies used for EV/PHEV, level-1 and -2 on-board charging and for providing reactive power support to the utility grid. It presents the design motives of single-phase on-board chargers in detail and makes a classification of the chargers based on their future vehicle-to-grid usage. The pros and cons of each different ac–dc topology are discussed to shed light on their suitability for reactive power support. This paper also presents and analyzes the differences between charging-only operation and capacitive reactive power operation that results in increased demand from the dc-link capacitor (more charge/discharge cycles and increased second harmonic ripple current). Moreover, battery state of charge is spared from losses during reactive power operation, but converter output power must be limited below its rated power rating to have the same stress on the dc-link capacitor.