A plug-in hybrid electric vehicle is a hybrid electric vehicle in its own right, with the difference being that its on-board power battery pack can be supplementally recharged using the electric power grid (including household power outlets), has a longer electric-only range, and can still operate in hybrid mode if necessary.

As a result, it has a larger-capacity power pack, a higher-power motor-drive system and a smaller-displacement engine than a hybrid electric vehicle.

This type of electric vehicle is characterized by:

Plug-in hybrid electric vehicles have the advantages of low noise and low emissions.

Plug-in hybrid electric vehicles are in between conventional hybrid electric vehicles and pure electric vehicles, with internal combustion engine-based hybrid modes for long trips (e.g., weekend excursions) and pure electric modes for short trips (e.g., normal commuting).

The on-board power battery can be recharged using the external power grid during evening lows, which not only improves the efficiency problem of power plant generator sets, but also greatly reduces dependence on petroleum; at the same time, the use of electricity is cheaper than fuel, which reduces the cost of use.

Because of the driving characteristics of plug-in hybrid electric vehicles, the power battery SOC must fluctuate in a wide range, belonging to the deep charging and deep discharging, so the cycle working life is affected to a certain extent, which requires the power battery to have the ability of deep charging and deep discharging.

Plug-in hybrid electric vehicles (PHEVs) are similar to power-holding hybrid electric vehicles, but they have a higher-capacity energy storage system and are connected to the grid through a power electronic interface.PHEVs have an energy storage system that can be recharged on-board as well as through a power strip. PHEVs can operate in battery-powered mode for longer periods of time than charge-holding hybrids.

For certain distances in the daily commute, PHEVs can operate in electric-only mode, with the internal combustion engine used to provide the extra power needed for longer distances. Sometimes called a "range extender," this type of vehicle replaces the fuel-burning energy of the internal combustion engine with energy from the external power grid. PHEVs have the potential to make better use of alternative fuels than other hybrids that derive their energy entirely from mineral fuels.

PHEV structures are similar to power-holding hybrids. The series structure is the simplest and highly suitable for PHEVs. due to the high energy storage capacity of the batteries, the internal combustion engine and generator do not need to be sized to match the peak power of the traction motors. The on-board charging interface is similar to that of a pure electric vehicle and needs to be connected to the grid. The structure of a series-connected PHEW is shown in the figure below. The parallel and series configurations are similar to conventional hybrid configurations, but PHEVs can be connected to the grid.

PHEVs use a battery pack to store energy for most of the drive, which reduces air and noise pollution as well as emissions.PHEVs are primarily electric and have low maintenance costs. PHEWs can also level the demand for electricity when the grid is at peak load. The extra power from plug-in hybrids can fill the grid when it is in high demand. This is known as "vehicle-grid" capability. When the grid is at a low load, the vehicle recharges.