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Electric Vehicle Offboard Charging Stations Headed In the Right (Bi)direction

Can a car battery that “gives back” to the grid help spur a greater adoption of plug-in electric vehicles (PEVs)? Or lead to more urban development?

Those are some of the possibilities to consider as a team of researchers at Bilecik University in Turkey continues to work on commercializing a first-of-its-kind charger that allows PEVs to deliver excess capacity to the power grid and recharge during off-peak hours.

As world transportation energy usage is predicted to increase by up to 44% by 2035, PEVs are becoming more widespread for their ability to reduce pollution and save hundreds of dollars on annual gas consumption. What many people don’t realize is that, beyond their sustainability, PEVs could offer significant power input/output (I/O) control and economic benefits to utilities operations.

Onboard chargers directly attached to PEVs are commonly used in the marketplace right now, but immobile offboard fast-charging stations are quickly gaining interest in the field. Despite their high overhead, offboard stations promise to lighten vehicle weight, charge at higher power levels faster, and create new contract opportunities between utility companies and station sites, such as shopping malls and restaurants.

An international team of researchers proves yet another benefit, which could perhaps be enough to convince investors to get on board with offboard charging: vehicle-to-grid (V2G) reactive power capabilities.

V2G is the act of sending power from a vehicle back into the grid to help manage I/O demands. In other words, it’s a two-way energy transfer where vehicles serve as a distributed system to buffer power. For example, the PEV batteries – which provide large energy reserve – can deliver excess capacity to the grid in response to peak load demand times, and then be recharged during off-peak hours at cheaper rates to help absorb excess night-time generation. With thousands of batteries connected to the grid via bidirectional chargers, they have the broad potential to fulfill the grid’s energy storage needs.

In 2014, researchers proposed, designed and tested the first-ever bidirectional offboard PEV charger with responsive V2G capabilities. To successfully respond to changing power commands, their control strategy involved a series of transformation equations, active and reactive power calculations, low-pass filters, and a phase-locked loop algorithm to maintain synchronization with the supply voltage.

Their simulated three-phase controller was then applied for real design and testing using a Vacon X series ac motor-drive unit. Different cases were tested to make sure the controller responded quickly and accurately to dynamic power commands, and in each case, the charger met those commands.

Furthermore, the battery was not affected from the reactive power operations.

“Offboard fast-charging stations are a key factor for the widespread market penetration of electric vehicles,” said Metin Kesler, lead researcher. “With reactive V2G power operations, they can now benefit utilities as well as consumers, and become an even more sustainable alternative to traditional gas-fuelled transportation.”

Even though Turkey’s plug-in electric vehicle market (PEV) may be young, it could be poised to deliver one of the industry’s most-impactful innovations.

Source: IEEE

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