Distribution Grid Voltage Support with Four Quadrant Control of Electric Vehicle Chargers

Conventionally, voltage control in distribution grids has been achieved through load tap changers, capacitor banks, and network switches. With the advancements in on-board electric vehicle (EV) chargers, voltage control can be achieved through control of EV charging/discharging as EVs can operate in any of the four P-Q quadrants with slight modifications to the charger. In this work, we use a high-fidelity on-board EV charger model, which has been validated using actual measurements. Then, we coordinate the four quadrant operation of EVs and distribution feeder to support voltage control in the grid. The efficacy of the developed models are demonstrated by using an LV secondary feeder. Operation of EVs in all four quadrants are shown to compensate for the feeder voltage fluctuations caused by daily time varying residential loads, while satisfying operational constraints of the feeder.

I. Introduction

Electric vehicle (EV) production from progressive manufacturers is gradually going up as the technology is increasingly adopted by customers who care about environment and energy. EV charging will soon become part of our everyday life. The challenge following this trend is that EV charging stresses the electric power grid especially when the system is at peak load. Solutions to detrimental impacts (such as transformer overloading, voltage drop, power losses) of EVs need to be investigated. To give a perspective on the adverse impact, study shows that 45% EV penetration can cause 25% more power losses and 50% transformer overloading in distribution feeders [1].