Zero average flux tracking algorithm for high frequency transformers in long pulse applications
(2018) 21st IEEE International Conference on Pulsed Power, PPC 2017 2017-June.- Abstract
High voltage long pulse klystron modulators typically use pulse transformers, where the length of the pulse dictates the size of the transformer. Recent advancements in power electronics applied to modulator technology, in order to facilitate multi-millisecond long pulse generation, instead suggests use of high frequency transformers in a high frequency pulse modulation/demodulation scheme, eliminating the size-pulse length dependency. The Stacked Multi-Level (SML) topology is built around this technique, where a cascaded power converters chain inverts, amplifies, rectifies and filters the voltage following a capacitor bank charging stage in order to generate high voltage pulses. In a modulator built to European Spallation Source... (More)
High voltage long pulse klystron modulators typically use pulse transformers, where the length of the pulse dictates the size of the transformer. Recent advancements in power electronics applied to modulator technology, in order to facilitate multi-millisecond long pulse generation, instead suggests use of high frequency transformers in a high frequency pulse modulation/demodulation scheme, eliminating the size-pulse length dependency. The Stacked Multi-Level (SML) topology is built around this technique, where a cascaded power converters chain inverts, amplifies, rectifies and filters the voltage following a capacitor bank charging stage in order to generate high voltage pulses. In a modulator built to European Spallation Source requirements, six such stages are connected in series at respective output, reducing stress on each module and increasing output ripple frequency, limiting the need of filtering, i.e. further reducing size, pulse rise time and stored energy. While use of this topology has demonstrated reduction in modulator footprint and cost for typical long pulse applications, use of high frequency switching obliges strict transformer core flux control in order to avoid transformer saturation due to undesired DC voltage components generated by the inverter without resorting to transformer oversizing Several methods implementing similar modes of control already exist, but commonly require additional sensors which may not be available or practical for inclusion in high voltage environments. Furthermore, available methods assume constant operation whereas the pulseforming stage needs to systematically switch off completely between pulses, creating an additional problem related to remanent core flux and saturation; it must be ensured that the core flux is properly set before the following pulse is to be generated, or pulse-to-pulse flux accumulation may entail transformer saturation. This paper describes the above problems in detail and outlines a practical algorithm, assessing its capability to control flux independent of pulse duration while minimizing rise time increase.
(Less)
- author
- Collins, Max LU and Martins, Carlos A. LU
- organization
- publishing date
- 2018-02-15
- type
- Chapter in Book/Report/Conference proceeding
- publication status
- published
- subject
- host publication
- 2017 IEEE 21st International Conference on Pulsed Power, PPC 2017
- volume
- 2017-June
- article number
- 8291244
- publisher
- IEEE - Institute of Electrical and Electronics Engineers Inc.
- conference name
- 21st IEEE International Conference on Pulsed Power, PPC 2017
- conference location
- Brighton, United Kingdom
- conference dates
- 2017-06-18 - 2017-06-22
- external identifiers
-
- scopus:85054246004
- ISBN
- 9781509057481
- DOI
- 10.1109/PPC.2017.8291244
- language
- English
- LU publication?
- yes
- id
- 6821927a-c079-4247-bb02-2de0d1e3d2f6
- date added to LUP
- 2018-11-06 12:16:25
- date last changed
- 2022-01-31 06:46:06
@inproceedings{6821927a-c079-4247-bb02-2de0d1e3d2f6,
abstract = {{<p>High voltage long pulse klystron modulators typically use pulse transformers, where the length of the pulse dictates the size of the transformer. Recent advancements in power electronics applied to modulator technology, in order to facilitate multi-millisecond long pulse generation, instead suggests use of high frequency transformers in a high frequency pulse modulation/demodulation scheme, eliminating the size-pulse length dependency. The Stacked Multi-Level (SML) topology is built around this technique, where a cascaded power converters chain inverts, amplifies, rectifies and filters the voltage following a capacitor bank charging stage in order to generate high voltage pulses. In a modulator built to European Spallation Source requirements, six such stages are connected in series at respective output, reducing stress on each module and increasing output ripple frequency, limiting the need of filtering, i.e. further reducing size, pulse rise time and stored energy. While use of this topology has demonstrated reduction in modulator footprint and cost for typical long pulse applications, use of high frequency switching obliges strict transformer core flux control in order to avoid transformer saturation due to undesired DC voltage components generated by the inverter without resorting to transformer oversizing Several methods implementing similar modes of control already exist, but commonly require additional sensors which may not be available or practical for inclusion in high voltage environments. Furthermore, available methods assume constant operation whereas the pulseforming stage needs to systematically switch off completely between pulses, creating an additional problem related to remanent core flux and saturation; it must be ensured that the core flux is properly set before the following pulse is to be generated, or pulse-to-pulse flux accumulation may entail transformer saturation. This paper describes the above problems in detail and outlines a practical algorithm, assessing its capability to control flux independent of pulse duration while minimizing rise time increase.</p>}},
author = {{Collins, Max and Martins, Carlos A.}},
booktitle = {{2017 IEEE 21st International Conference on Pulsed Power, PPC 2017}},
isbn = {{9781509057481}},
language = {{eng}},
month = {{02}},
publisher = {{IEEE - Institute of Electrical and Electronics Engineers Inc.}},
title = {{Zero average flux tracking algorithm for high frequency transformers in long pulse applications}},
url = {{http://dx.doi.org/10.1109/PPC.2017.8291244}},
doi = {{10.1109/PPC.2017.8291244}},
volume = {{2017-June}},
year = {{2018}},
}