BASIC VARIANTS
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5
5.2.2
Control Structure
The figure below presents power control when the DC/DC converter is between DC-Link and the
battery.
Figure 34. Power control example
DC to DC can be used on a system where peak power shaving is desired, and grid power sources’
power sharing is done mainly through active power drooping. In such system, the power and grid
frequency behave as shown in the picture below (Figure 35).
Figure 35. Behavior of system power and grid frequency
Grid Converter operation.
•
Power control possible when operating parallel with other power sources.
o Reference is base current reference (+/-).
o If the device is operating in island mode, the power reference changes the
frequency.
•
Grid frequency variations will affect what will be actual power to the grid.
o Operates like a normal generator.
o Power reference is several times faster than a normal diesel generator.
o Frequency drop in a grid will increase grid converter power output without power refer-
ence.
•Useful in situations here PMS is not fast enough or is unable to control.
•Upper system needs to give charging and discharging limit to the DC/DC converter.
•
Upper system needs to give minimum and maximum voltage limits to the DC/DC converter.
o Grid Converter needs also under voltage limit because battery voltage can come directly
to DC-Link trough DC/DC converter, if DC-Link voltage goes below battery voltage.
U2
U3
C
DC-Link
DC/DC
Converter
T2
Q1
U1
L
L
L
Filter
Source
DC
Grid
Di
s
c
h
a
rg
e
Power
Frequency
Ge
n
e
ra
to
r
M
o
to
ri
n
g
Average
Charge
Summary of Contents for NX6
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