XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3849
First Attempt at Improving System Performance Using
Ridethrough
As noted in the previous section, network asymmetry, net-
work undervoltage or transformer saturation results in the
inability of the drive to provide proper current control.
The variable frequency converters at Detour Lake Mine are
equipped with three Active Rectifier Units (ARU) which
are responsible for the controlled rectification of the incom-
ing AC voltage by switching Integrated Gate Commutation
Thyristor (IGCT) modules and are responsible for keeping
the DC link voltage constant. This DC link voltage is then
converted to a variable frequency voltage by Inverter Units
(INU) that is then output to the main motors. Each motor
has one independent INU. Figure 5 provides a high-level
overview of the drive.
To improve the resilience of the drive system during
a network transient, the front end of the drive was modi-
fied to operate as a pure rectifier bridge by stopping the
modulation of the IGCT modules (ridethrough) when the
network voltage would drop below 70% of nominal. The
modulation would be restarted once the network voltage
was restored to its nominal value.
A new shared-current control algorithm was also
implemented in the ARU software to minimize current
imbalances in the transformers. The three parallel ARUs
at Detour Lake Mine are interleaved with series-connected
transformers (Figure 6). During normal operation the cur-
rents in the three transformers are the same but in non-
ideal cases, for e.g., during a voltage transient that causes
the saturation of one transformer core, one branch current
can get out of control. The new algorithm improved the
control of each individual ARU thereby reducing the inci-
dence of transformer saturation.
This approach was successful in reducing the num-
ber of trips but did not eliminate the issue completely.
Additionally, the random nature of these events made effi-
cient data gathering challenging. Any subsequent changes
in the program of the drive had to be observed and progress
on site was slow.
Modeling the System
In order to rapidly test various scenarios and to better
understand the behaviour of the drive, steps were taken
to reproduce the behaviour of the drive using a simulator.
The simulator consists of test equipment that combine real
Figure 3. Calculated in-rush current for a mill. The half peak value time is 0.491 seconds (red dotted line) and the peak value
is 5934A. Nominal current is 820A
First Attempt at Improving System Performance Using
Ridethrough
As noted in the previous section, network asymmetry, net-
work undervoltage or transformer saturation results in the
inability of the drive to provide proper current control.
The variable frequency converters at Detour Lake Mine are
equipped with three Active Rectifier Units (ARU) which
are responsible for the controlled rectification of the incom-
ing AC voltage by switching Integrated Gate Commutation
Thyristor (IGCT) modules and are responsible for keeping
the DC link voltage constant. This DC link voltage is then
converted to a variable frequency voltage by Inverter Units
(INU) that is then output to the main motors. Each motor
has one independent INU. Figure 5 provides a high-level
overview of the drive.
To improve the resilience of the drive system during
a network transient, the front end of the drive was modi-
fied to operate as a pure rectifier bridge by stopping the
modulation of the IGCT modules (ridethrough) when the
network voltage would drop below 70% of nominal. The
modulation would be restarted once the network voltage
was restored to its nominal value.
A new shared-current control algorithm was also
implemented in the ARU software to minimize current
imbalances in the transformers. The three parallel ARUs
at Detour Lake Mine are interleaved with series-connected
transformers (Figure 6). During normal operation the cur-
rents in the three transformers are the same but in non-
ideal cases, for e.g., during a voltage transient that causes
the saturation of one transformer core, one branch current
can get out of control. The new algorithm improved the
control of each individual ARU thereby reducing the inci-
dence of transformer saturation.
This approach was successful in reducing the num-
ber of trips but did not eliminate the issue completely.
Additionally, the random nature of these events made effi-
cient data gathering challenging. Any subsequent changes
in the program of the drive had to be observed and progress
on site was slow.
Modeling the System
In order to rapidly test various scenarios and to better
understand the behaviour of the drive, steps were taken
to reproduce the behaviour of the drive using a simulator.
The simulator consists of test equipment that combine real
Figure 3. Calculated in-rush current for a mill. The half peak value time is 0.491 seconds (red dotted line) and the peak value
is 5934A. Nominal current is 820A