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Minimizing power pulsations in a free piston energy converter
KTH, School of Electrical Engineering (EES).
KTH, School of Electrical Engineering (EES).ORCID iD: 0000-0002-0744-2552
KTH, School of Electrical Engineering (EES).
2005 (English)In: 2005 European Conference on Power Electronics and Applications, 2005Conference paper, Published paper (Refereed)
Abstract [en]

A Free Piston Energy Converter (FPEC) is a combination of a linear combustion engine and a linear electrical machine. This type of converter has many potential advantages like high efficiency, low fuel consumption and low emissions, which make it suitable for a series hybrid vehicle. However, the generated power pulsates due to the reciprocating motion of the translator. This paper presents a comparative study on how different generator force profiles affect the electric power pulsations produced by the FPEC. In addition, the influence of these profiles on translator motion and the needed power converter current is investigated. A dynamic free piston model is used for the investigation. Results show that the generator force profile has a major impact on the power pulsation amplitude and peak current demand. Thus the chosen force profile will affect dimensioning of power converter, electrical machine and energy storage. Furthermore, loading the translator heavily in the beginning or end of the stroke seems to affect the peak translator velocity more than evenly distributed load profiles.

Place, publisher, year, edition, pages
2005.
Keyword [en]
Converter machine interactions, Distributed power, Emerging technology, Energy converters for HEV, Generation of electrical energy, Hybrid Electric Vehicle (HEV), Linear drive
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6429Scopus ID: 2-s2.0-33947636523ISBN: 978-907581508-5 (print)OAI: oai:DiVA.org:kth-6429DiVA: diva2:11138
Conference
2005 European Conference on Power Electronics and Applications; Dresden; 11 September 2005 through 14 September 2005
Note
QC 20101116Available from: 2006-11-27 Created: 2006-11-27 Last updated: 2010-11-16Bibliographically approved
In thesis
1. Analysis and control of a hybrid vehicle powered by free-piston energy converter
Open this publication in new window or tab >>Analysis and control of a hybrid vehicle powered by free-piston energy converter
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The introduction of hybrid powertrains has made it possible to utilise unconventional engines as primary power units in vehicles. The free-piston energy converter (FPEC) is such an engine. It is a combination of a free-piston combustion engine and a linear electrical machine. The main features of this configuration are high efficiency and a rapid transient response.

In this thesis the free-piston energy converter as part of a hybrid powertrain is studied. One issue of the FPEC is the generation of pulsating power due to the reciprocating motion of the translator. These pulsations affect the components in the powertrain. However, it is shown that these pulsations can be handled by a normal sized DC-link capacitor bank. In addition, two approaches to reduce these pulsations are suggested: the first approach is using generator force control and the second approach is based on phase-shifted operation of two FPEC units. The latter approach results in higher frequency and lower amplitude of the pulsations, which reduce the capacitor losses.

The FPEC start-up requirements are analysed and by choosing the correct amplitude of the generator force during start-up the energy consumption can be minimised.

The performance gain of utilising the FPEC in a medium sized series hybrid electric vehicle (SHEV) is also studied. An FPEC model suitable for vehicle simulation is developed and a series hybrid powertrain, with the same performance as the Toyota Prius, is dimensioned and modelled.

Optimisation is utilised to find a lower limit on the SHEV's fuel consumption for a given drivecycle. In addition, three power management control strategies for the FPEC system are investigated: two load-following strategies using one and two FPEC units respectively and one strategy based on the ideas of an equivalent consumption minimisation (ECM) proposed earlier in the literature.

The results show a significant decrease in fuel consumption, compared to a diesel-generator powered SHEV, just by replacing the diesel-generator with an FPEC. This result is improved even more by using two FPEC units to generate the propulsion power, as this increases the efficiency at low loads. The ECM control strategy does not reduce the fuel consumption compared to the load-following strategies but gives a better utilisation of the available power sources.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 111 p.
Series
Trita-EE, ISSN 1653-5146 ; 2006:047
Keyword
free-piston energy converter, FPEC, series hybrid electric vehicle, SHEV, power management, energy management, powertrain evaluation, equivalent consumption minimisation, ECMS, linear engine
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4189 (URN)91-7178-485-3 (ISBN)
Presentation
2006-11-27, H1, Teknikringen 33, Stockholm, 15:00
Opponent
Supervisors
Note
QC 20101116Available from: 2006-11-27 Created: 2006-11-27 Last updated: 2010-11-16Bibliographically approved

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Leksell, Mats

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