Elimination of Harmonic Disturbances in Softstarters
(2021) EITM02 20182Department of Electrical and Information Technology
- Abstract
- Power system infrastructure has been facing many challenges when it comes to
harmonics distortion, and power electronic devices are no exception considering
their wide usage in the system. In this thesis the focus is on the impact of these
system harmonics on the electrical motors which are vastly used in industry for
different applications. Motors usually come with a softstarter, and are connected
to the grid. Softstarters are used to avoid mechanical stress and voltage drops in
the network while starting up motors and being connected as a group with the
motor to the grid means that they will also be affected by the system harmonics.
Softstarter consists of various power electronics components, such as Switches in
shape of... (More) - Power system infrastructure has been facing many challenges when it comes to
harmonics distortion, and power electronic devices are no exception considering
their wide usage in the system. In this thesis the focus is on the impact of these
system harmonics on the electrical motors which are vastly used in industry for
different applications. Motors usually come with a softstarter, and are connected
to the grid. Softstarters are used to avoid mechanical stress and voltage drops in
the network while starting up motors and being connected as a group with the
motor to the grid means that they will also be affected by the system harmonics.
Softstarter consists of various power electronics components, such as Switches in
shape of thyristors, resistor and capacitor. An important part of a softstarter is the
snubber circuits which is sensitive against high-frequency harmonics. The snubber
circuit is mainly composed of a snubber resistor and a capacitor. In fact, presence
of high-frequency harmonics in the system, would reduce the impedance of the
snubber circuit’s capacitor. Thus the overall impedance of the snubber circuit
would drop and accordingly current passing the snubber resistor would increase.
The snubber resistor would become too hot and most probably melt. As a result,
this phenomena in many cases, causes faults in the facility or even it causes a
failure in the system. Considering the consequences of failure, it is necessary to
cope with the destructive harmonics in an effective way. In this thesis, we are
purposing a new strategy and a novel solution to maintain a reliable performance
of the softstarter’s while facing high frequency harmonics of the system. As the
source of the issue are the high frequency harmonics, the best solution would be
to eliminate them when they show up. That can be done by a properly designed
and adjusted high pass-filter. In this work we tried to consider a cost effective
solution that can also eliminates the harmonics. We are proposing using an extra
indicator that is fine tuned and is adjusted in a way that together with the rest of
the components it shapes high-pass filter, which would block the high frequency
harmonics as they appear. To be able to do that the existing circuit was deeply
measured and analyzed and with the gathered information regarding the current
behaviour of the system under high frequency harmonics, an inductor was adjusted
and added to the circuit. Various tests to verify the performance are done and are
presented in this report. From the result it can clearly be seen that the inductor
together with the rest of the system could properly act as a high- pass filter and
eliminate the destructive high frequency harmonics. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9041365
- author
- Mahdivand Avilagh, Raheleh LU
- supervisor
- organization
- course
- EITM02 20182
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- report number
- LU/LTH-EIT 2020-806
- language
- English
- id
- 9041365
- date added to LUP
- 2021-03-10 09:47:07
- date last changed
- 2021-03-10 09:47:07
@misc{9041365,
abstract = {{Power system infrastructure has been facing many challenges when it comes to
harmonics distortion, and power electronic devices are no exception considering
their wide usage in the system. In this thesis the focus is on the impact of these
system harmonics on the electrical motors which are vastly used in industry for
different applications. Motors usually come with a softstarter, and are connected
to the grid. Softstarters are used to avoid mechanical stress and voltage drops in
the network while starting up motors and being connected as a group with the
motor to the grid means that they will also be affected by the system harmonics.
Softstarter consists of various power electronics components, such as Switches in
shape of thyristors, resistor and capacitor. An important part of a softstarter is the
snubber circuits which is sensitive against high-frequency harmonics. The snubber
circuit is mainly composed of a snubber resistor and a capacitor. In fact, presence
of high-frequency harmonics in the system, would reduce the impedance of the
snubber circuit’s capacitor. Thus the overall impedance of the snubber circuit
would drop and accordingly current passing the snubber resistor would increase.
The snubber resistor would become too hot and most probably melt. As a result,
this phenomena in many cases, causes faults in the facility or even it causes a
failure in the system. Considering the consequences of failure, it is necessary to
cope with the destructive harmonics in an effective way. In this thesis, we are
purposing a new strategy and a novel solution to maintain a reliable performance
of the softstarter’s while facing high frequency harmonics of the system. As the
source of the issue are the high frequency harmonics, the best solution would be
to eliminate them when they show up. That can be done by a properly designed
and adjusted high pass-filter. In this work we tried to consider a cost effective
solution that can also eliminates the harmonics. We are proposing using an extra
indicator that is fine tuned and is adjusted in a way that together with the rest of
the components it shapes high-pass filter, which would block the high frequency
harmonics as they appear. To be able to do that the existing circuit was deeply
measured and analyzed and with the gathered information regarding the current
behaviour of the system under high frequency harmonics, an inductor was adjusted
and added to the circuit. Various tests to verify the performance are done and are
presented in this report. From the result it can clearly be seen that the inductor
together with the rest of the system could properly act as a high- pass filter and
eliminate the destructive high frequency harmonics.}},
author = {{Mahdivand Avilagh, Raheleh}},
language = {{eng}},
note = {{Student Paper}},
title = {{Elimination of Harmonic Disturbances in Softstarters}},
year = {{2021}},
}