IEEE Power Electronics Magazine - June 2018 - 71

Summary
Fixed Voltage
Regulation

Source

Constant Current
Regulation

Bidirectional
Preregulator Module

Battery

Forward
Reverse

FIG 8 An example of a bidirectional regulator. This can operate in one of two
modes at any given time: constant current regulation, a constant voltage trickle
charge mode capability available at the battery-connected port in forward mode;
and fixed voltage regulation mode at the source/load-based port, achieved in
reverse preregulator module operation.

being made to the way in which the control, switching, and
sensing is done, rather than by having to change the power
train itself. One anticipates that new power components will
be devised that exhibit the ability to move power implicitly
without the need to consider which port needs excitation
during an initial start-up.
There is another challenge that needs to be tackled involving the control of power going into storage elements, such as
chemical batteries and supercapacitors. When charging is
required, current limiting is applied until a predetermined
voltage level is attained and is the preferred means of maintaining a charging system within its safe operating limits.
Consistent battery conditioning, which involves monitored
two-way power flow, also extends battery life. The introduction of voltage and current regulators into bidirectional
power scheme enables precise control at critical partitions
in any useful system.
Figure 7 outlines a way of providing regulation capability that can be interchanged between the two ports
shown, these being a 384-V dc bus and a 48-V battery
bank. At any given time, only one of the two regulators is
used, while the other remains in a standby state. A better
approach would involve making what amounts to a purpose-designed single bidirectional regulator. The power
train is left intact, but the sensing and control elements
are designed for automatic start-up and on-the-fly reconfiguration of the power train to provide the seamless
interchange of ports. Digital control provides this muchneeded layer of programmability, allowing reuse of the
same power hardware in exchange for taking on a small
digital control overhead. Essentially, we now have a regulator to complement the SAC's ability to provide isolated,
transformed dc voltages and currents. An example of this
concept is shown in Figure 8.

Principles, definitions, and a number of
bidirectional power conversion examples
have been presented. Proposals for bidirectional regulators are made on the basis
of the functionality of solutions that were
shown here.
Bidirectional power conversion is a vital
part of any system where alternative sources,
energy storage, and load management are in
contention. In energy terms, the applications
that are served need to be viewed as closed
systems. The more remote the application,
the more important this aspect of power
design and provision becomes.

About the Author

David Bourner (dbourner@vicr.com)
received his B.S. degree in electrical and
electronic engineering from the University of Bath, United
Kingdom, in 1981. He received his master of philosophy
degree from the University of Southampton in 1991 and his
postmaster's certificate in microwave and optimal systems
from the Whiting School of Engineering at the Johns Hopkins University Applied Physics Lab. He is currently a senior
field applications engineer with Vicor Corporation at the
Andover Technical Sales Center, Massachusetts, and has
had varied assignments at Hughes Network Systems, Analog Devices, National Semiconductor, Micrel Corp, and the
University of Maryland, Baltimore County, as a professor of
computer engineering. His research interests include MOS
analog integrated circuit data converter system design, for
which he received a grant in 1990 from the United Kingdom
Ministry of Defense.

References
[1] R. W. Erickson, Fundamentals of Power Electronics, Norwell, MA:
Kluwer, 1999.
[2] U. Ghisla, "A novel, non-isolated bus converter enables high efficiency
energy transport to supply high power loads in cars," in Proc. Electric/
Electronic Systems in Hybrid and Electric Vehicles and Electrical Energy
Management Conf., Wiesloch, Germany, 2016, pp. 453-461.
[3] M. Salato, "The sine amplitude converter topology provides superior efficiency and power density in intermediate bus architecture converters," Vicor
Corp., Andover, MA, White Paper, 2011.
[4] Point of load sine amplitude converters and methods, by P. Vinciarelli.
(2016, Dec). U.S. Patent 7,145,786. [Online]. Available: https://patents.google
.com/patent/US7145786
[5] A. Patel, "A new bidirectional dc-dc converter for fuel cell, solar cell,
and battery systems," in Proc. 2016 IEEE Applied Power Electronics Conf.,
Long Beach, CA, 2016, pp. 150-155.

June 2018

z IEEE PowEr ElECtronICS MagazInE

https://patents.google.com/patent/US7145786 https://patents.google.com/patent/US7145786

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - June 2018