Electric vehicles (EVs) are becoming mobile power stations capable of energizing everything from camping equipment to entire buildings. Vehicle-to-Everything (V2X) technologies, including Vehicle-to-Equipment (V2E) applications, are changing how engineers design EV power architectures. Bidirectional charging is the core concept of EV power architectures for V2X and V2E applications.
This article looks at how bidirectional charging systems are progressing, including types of converters and improvements in semiconductor technologies.
What is V2X, and how does V2E fit?
V2X consists of five primary applications, including Vehicle-to-Grid (V2G), Vehicle-to-Home (V2H), Vehicle-to-Building (V2B), Vehicle-to-Load (V2L), and Vehicle-to-Vehicle (V2V). Each application places unique demands on the vehicle’s power architecture, as shown in Figure 1.
Figure 1. The five V2X applications driving bidirectional power architecture evolution in EVs. (Image: ResearchGate)
However, V2E/V2L stands out for its relative simplicity and immediate practicality. Here’s what makes it particularly appealing.
Unlike V2G, which requires complex grid synchronization and external bidirectional chargers, V2E operates independently. It functions through the vehicle’s integrated power conversion systems.
The V2X applications overview shows these different ways to connect. They build a complete ecosystem where EVs can be used for more than just transportation.
The easiest way to get into this ecosystem is through V2E/V2L. It does not need much external infrastructure and can be used right away for powering equipment and applications, as shown in Figure 2.
V2E technology lets EVs power external devices and equipment with standard ac power. This feature operates through built-in inverters and ac outlets. EVs can now be turned into mobile power stations that can provide continuous power between 2.4 and 9.6 kW thanks to this technology.
The technology uses the EV’s large battery, which is usually 65 kWh or more. It can power everything from camping gear to backup power systems for emergencies.
Figure 2. Vehicle-to-Equipment (V2E) configuration showing 240 V ac power delivery to appliances and loads. (Image: Clean Energy Reviews)
How have EV power architectures evolved to support V2X capabilities?
EV power architectures have undergone significant changes due to the addition of V2X and V2E capabilities. Earlier EVs had power flow systems that were only unidirectional and were ideal for propulsion. But applications that work in bidirectional mode need more complex power management systems. To be safe, efficient, and work with the grid, these systems must be able to handle energy flow in both directions.
Modern EV power architectures use multistage conversion stages where each stage is best for a certain type of operation. The powertrain architecture in
Figure 3. An EV powertrain architecture featuring bidirectional onboard charger with multi-stage power conversion. (Image: ResearchGate)
Figure 3 shows that the first stage is usually made up of an ac/dc converter that fixes the power factor so that EVs can be charged from the grid. Dc/dc converters are used in the second stage to manage the batteries and keep the voltage stable.
For V2E uses, an extra dc/ac inverter changes the dc voltage from the battery to a normal ac output. In this configuration, the vehicle can work as a power source on its own.
From an engineering point of view, this is where things really get interesting. Because of how complicated the architecture is, converter topology design has come a long way.
Two-stage bidirectional onboard chargers (OBCs) are being used by more and more manufacturers. These systems keep the functions of the grid interface and battery management separate.
With this separation, performance can be optimized in each operational mode. Totem-pole power factor correction circuits and isolated dc-dc converters are common parts of these systems, while dual active bridge (DAB) or CLLC resonant converters are two common types of converters.
The detailed architecture of the bidirectional charger in Figure 4 shows that it has complex control systems. These systems control the direction of power flow, the charging profiles for batteries, and the synchronization of the grid.
This level of integration is a big step up from older charging systems that only worked unidirectionally. It has advanced safety protocols and power management algorithms that are needed for V2X to work reliably.
How are dc-dc converter technologies advancing to support V2E?
As V2X and V2E capabilities have grown, they have sped up development in dc-dc converter technologies. Hybrid energy storage systems in EVs need complex power management. They have to work together with different energy sources, like supercapacitors, main traction batteries, and other systems.
What does this mean for system designers? Because of this need, more advanced bidirectional dc-dc converter topologies have been used. These topologies make it easy for power to flow between different types of energy storage elements.
Figure 4. Bidirectional battery charger architecture with advanced control systems for V2X power management. (Image: ResearchGate)
The detailed classification of topologies in Figure 5 shows the wide range of converter architectures used in EVs. It has become more popular to use non-isolated topologies like interleaved buck-boost and three-level converters. They are very efficient and have a small size.
These converters lower the voltage stress on power switches and make the whole system more reliable. When galvanic isolation is needed, isolated topologies offer better safety and voltage transformation abilities. Dual active bridge and bidirectional forward converters are two examples.
Engineers who work in power electronics will understand how important new developments are. Coupled inductors and soft-switching technologies have been added to make converters even better. These new ideas cut down on switching losses and current ripple.
Figure 5. Bidirectional dc-dc converter topologies classification for hybrid energy storage systems. (Image: MDPI)
These changes are especially important for V2E applications where power quality and efficiency have a direct effect on the user experience and battery life in V2E systems.
Why have SiC and GaN become essential for V2X power architectures?
The use of wide bandgap (WBG) semiconductors has been a major force in the evolution of power architecture, with silicon carbide (SiC) and gallium nitride (GaN) as the main materials. When compared to regular silicon, these materials have better properties, such as higher breakdown voltage, thermal conductivity, and switching speeds.
The noteworthy aspect about this change is how quickly it happened. The industry data (Figure 6) makes it clear that there has been a big change in how semiconductor technology is used. The data shows a change from designs that used silicon to ones that used WBG semiconductors.
From 2010 to 2016, silicon devices dominated most implementations. On the other hand, there was a big change from 2017 to 2023. In advanced two-way charger designs, SiC and GaN technologies have taken up big shares of the market.
Figure 6. WBG semiconductor adoption trends in bidirectional OBCs, demonstrating the transition from Si-dominated to SiC/GaN-dominated designs. (Image: ResearchGate)
Summary
From simple unidirectional charging to complex bidirectional power management, the change is more than just a technical one. It changes everything about how we think about EVs and power systems. V2X and V2E technologies are making a leap in all kinds of converter topologies, from simple ac/dc systems to complicated two-way designs with DAB and CLLC converters.
Moving toward WBG semiconductors like SiC and GaN has made worthy gains in efficiency and power density. We can expect integration and modularity trends to continue in the future, with power densities getting close to 5 to 10 kW/L and efficiency levels going over 98%.
Most importantly, EVs are becoming more and more integrated into our energy ecosystem. This is changing how we make, store, and use electricity in fundamental ways.
References
- Bidirectional DC-DC Converter Topologies for Hybrid Energy Storage Systems in Electric Vehicles: A Comprehensive Review, Energies, MDPI
- Power flow control with bidirectional dual active bridge battery charger in low-voltage microgrids, ResearchGate
- The state-of-the-art of power electronics converters configurations in electric vehicle technologies, ScienceDirect
- On-Board Chargers for Electric Vehicles: A Comprehensive Performance and Efficiency Review, Energies, MDPI
- A Review on Implementation of Vehicle to Everything (V2X): Benefits, Barriers and Measures, ResearchGate
- Bidirectional On-Board Chargers for Electric Vehicles: State-of-the-Art and Future Trends, ResearchGate
- Vehicle-to-load Explained – V2L for off-grid or backup power, Clean Energy Reviews
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Filed Under: Charging, FAQs, Vehicle-to-Grid (V2G)