Such a converter must have bidirectional power flow capability with flexible control in all operating modes. In HEV applications, BDCs are required to link different dc voltage buses and transfer energy between them. For example, a BDC is used to exchange energy between main batteries (200-300V) and the drive motor with 500V dc link.
AC/DC topologies Bi-directional converters use the same power stage to transfer power in either directions in a power system. Helps reduce peak demand tariff. Reduces load transients. V2G needs “Bi-Directional” Power Flow. Ability to change direction of power transfer quickly. High efficiency >97% (End to End) at power levels up to 22KW.
Figure 1 shows a block diagram of a classical DC-coupled energy storage system, in which the bidirectional DC/DC is responsible for charging and discharging the battery. For safety, low-voltage battery pack systems (40V to 60V) require bidirectional isolation DC/DC due to the high bus voltage (360V to 550V).
Bidirectional dc-dc converters (BDC) have recently received a lot of attention due to the increasing need to systems with the capability of bidirectional energy transfer between two dc buses.
For DHB configuration it will lead to Similar to DAB configuration, the maximum power transfer is at |φ|=90 degrees. So the converter full range of bidirectional power transfer can be gained by controlling phase shift in -90 to +90 range.
As energy transfer in either direction is required for the system, each dc-ac converter must also have bidirectional energy transfer capability. With the same token, the dc buses in this structure must also be able to either generate or absorb energy.