ABB UNITROL 1020 - Page 61

 Chapter 3 - Device Overview
UNITROL 1020 User Manual 3BHS335648 E82 53
SM SM
SM SM
Load A Load B
AVR 1 AVR 2 AVR 3
AVR 4
RS-485
SM SM
Load C
AVR 5
AVR 6
RS-485
RS-485
Figure 3-9 VDC application example of six machines and two nets.
When the Secondary Net is required, it should be configured using a digital input. This
input determines whether the AVR uses data for VDC calculation from the devices
configured in the Primary or Secondary Net. The user can select 4 different net IDs
depending on two digital inputs. The load sharing takes place between AVRs with the
same net IDs. The list below shows an example of how to set the net IDs for each AVR in
relation to the digital input.
Net type
Net ID
default
Digital input
Secondary Net 1
Secondary Net 2
AVR 1+2
Net ID
AVR 3+4
Net ID
AVR 5+6
Net ID
Net 2
Net 1
Primary Net
1
0
0
11
12
13
Secondary Net
2
0
1
2
2
13
Secondary Net
3
1
0
11
3
3
Secondary Net
4
1
1
4
4
4
Note that the net IDs are chosen in a way to represent the possible load sharings:
 Net ID1: Load sharing only in the same bus segment
 Net ID 2: Load sharing between Load A and B
 Net ID 3: Load sharing between Load B and C
 Net ID 4: Load sharing between all machines
The Primary and Secondary Net ID numbers should be different from each other and
unique for each load sharing group.
When no digital input is configured for Secondary Net 1 nor Net 2, the VDC net ID is set
to the primary net ID.
3.4.3.3 Voltage Droop Compensation for Ring Configuration
VDC mode can also be used in a ring structure, where the ring can be split up and the
AVR automatically shares load with the connected machines.
A ring is based on segments with a left (decreasing) and right (increasing) breaker. The