SE543149C2

SE543149C2 - Electrical power buffer unit for use in railway systems

Info

Publication number: SE543149C2
Application number: SE1850865A
Authority: SE
Inventors: Jonas Persson
Original assignee: Vattenfall Ab
Priority date: 2018-07-09
Filing date: 2018-07-09
Publication date: 2020-10-13
Also published as: EP3820761A1; WO2020013744A1; SE1850865A1

Abstract

An electrical power buffer unit for supplying electrical power to a railway train is provided. The electrical power buffer unit comprises connection means, charging means, supplying means and a control unit. The connection means is arranged to connect to an electrical feed. The electrical feed is arranged to provide electrical power to the railway train. The charging means is arranged to charge the electrical power buffer unit from the electrical feed. The supplying means is arranged to supply electrical power from the electrical power buffer unit to the electrical feed. The control unit is arranged to switch the electrical power buffer unit from a first mode of operation to a second mode of operation. The first mode of operation comprise charging the electrical power buffer unit from the electrical feed. The second mode of operation comprise supplying electrical power from the electrical power buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed.

Description

1 Electrical power buffer unit for use in railway systems TECHNICAL FIELD The present invention generally relates to the field of powering railways and more particularlyto an electrical power buffer unit, a system and a method for supplying electrical power to a railway train and associated use.

BACKGROUND ART Transportation is an occurring aspect in all historical and modern societies. People transportingthemselves or goods from one location to another are present in numerous aspects of life, suchas trade, commuting, vacation etc. Multiple transportations form complex logistical networkswith several connection transports, thereby putting and increasing demands on reliability and efficiency on the transportations.

One mode of transportation is by trains on railway tracks. By using dedicated infrastructure,railways, trains have become a reliable mode of transportation. Historically, trains have beenusing internal combustion engines. These internal combustion engines demands that a fuelsupply is transported by the train, thereby limiting the amount of load for goods. Further, aninternal fuel supply demands infrastructure for re-fuelling. Further still, combustion engines strain the environment.

By using trains with an internal electrical engine and providing electricity to the trains fromexternal power generation stations, additional improvements in the railways have been made.For example electrical trains are more environmentally friendly, have a higher degree of reliability etc.

However, since the electrification of the railway, the load on the railways have increased. Thisincreased load results in that parts of the power delivery infrastructure are lacking capacity.Thereby, some trains do not receive enough power to maintain a high level of utility with following problems relating to reliability and efficiency. 2Thus, the inventor of the present invention has identified a need for improvements in poweringrailways that is designed to improve the su pplying of power to a railway train or at least mitigatethe problems in association with the increased load stated above, and which provides a method with an improved functionality that provides reliability benefits.

Electricity is distributed to trains by transmission lines in a regional or distribution network. Eachpart of the regional or distribution network is arranged to provide power to a section of therailway tracks via a feeding transformer and a rotating converter (or static converter), see figure6a. For each section the power is supplied to the railway train by a catenary, this may be by asuspended overhead line, a fixed structu res above, below or next to the tracks, a fixed structu ressuch as a third rail and sometimes also a fourth rail. The power from the power distributionnetwork is provided to the catenaries from a transformer station including a feeding transformer and a rotating converter (or static converter) for each section of the railway tracks.

One or several trains at the same section demands a lot of power, sometimes more than thepower supplying infrastructure can provide. Since the trains strain each of the plurality sectionfor a limited time, and the high cost involved for infrastructure, the power supply infrastructureis adapted to an intermediate level, i.e., dimensioned for a probable peak. instead of being adapted for the maximum strain that one or several trains can provide.

Since the power is provided from the power distribution network to each section at one point,the voltage delivery capacity at remote parts of the section drops even more during load.Thereby the power deliverable to the train varies over a section as a function of the voltage level.

SUMMARY OF THE INVENTION While the voltage delivery capacity at remote parts of a section may be improved by havingshorter section, such solutions demand a lot of additional hardware and an added complexityto the railway infrastructure, i.e., several new feeding stations. For example shorter sectionswould demand a reroute of the catenaries, new branches in the power distribution network andadditional transformer stations to transform the power in the power distribution networks to the power in the catenaries. 3ln addition, the big difference in load from not having a train on the section to having a train on the section strains the power delivery system.

An object of the present invention is to provide a system for providing electrical power to a railway train which overcomes the problems stated above.

A further object of the present invention is to provide a system with advantages relating to the reliability of the power supply method.

Aspects of the present invention are defined in to the independent claims. Preferred embodiments are set forth in the dependent claims.

The invention is based on an insight that an electrical power buffer may be implemented inconnection with the electrical feed of a railway section, by this the electrical power buffer maybe charged by the electrical feed when the demands are low and emit power to the electricalfeed when the demands are high. Typically, the demands are low when no train is powered inthe railway section and the demands are high when a train is powered in the railway section. Bythis, the electrical power buffer may provide additional power, the capacity of the electrical feed ofthe railway section will be improved. ln addition, since the electrical power buffer may provide additional power, the load on thetransformer powering the electrical feed of the railway section and the demands on the power distribution network may be decreased.

Further, by charging the electrical power buffer from the power distribution network when thedemands are low, the consumption when the demands are low will be increased. Thereby thedifference between high and low load on the power distribution network will be further decreased. By this, the transformer station will be relieved and the wear will be decreased.

According to one aspect of the invention, an electrical power buffer unit for supplying electricalpower to a railway train is provided. The electrical power buffer unit comprises connectionmeans, charging means, supplying means and a control unit. The connection means is arrangedto connect to an electrical feed. The electrical feed is arranged to provide electrical power tothe railway train. The charging means is arranged to charge the electrical power buffer unit fromthe electrical feed. The supplying means is arranged to supply electrical power from the electrical power buffer unit to the electrical feed. The control unit is arranged to switch the 4electrical power buffer unit from a first mode of operation to a second mode of operation. Thefirst mode of operation comprise charging the electrical power buffer unit from the electricalfeed. The second mode of operation comprise supplying electrical power from the electricalpower buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed.

An electrical power buffer unit according to the present invention overcomes the problemsstated previously and improves the supplying of power to a railway train. Suitable applicationsfor a unit according to the present invention may be a situation where an improved supply of electrical power to a railway train is requested.

By this, a device, a method and a system for supplying electrical power to a railway train may be established. ln one embodiment, the electrical power buffer unit may comprise a transformer arranged tosupply electrical power from the electrical power buffer to the electrical feed of similar specifications as the electrical feed. ln one embodiment, the electrical power buffer unit may be connected via a buffertransformer.The buffer transformer may be arranged to convert between the power characteristics suitablefor the electrical power buffer unit and the grid or feed to which the electrical power buffer unit may be connected to. ln one embodiment, the electrical power buffer unit may be connected via a buffer transformer and a rotating converter. ln one embodiment, the control unit may be arranged to detect a railway train in connectionwith the electrical feed. On detecting the railway train the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation. ln one embodiment, the control unit may be arranged to measure an electrical property on theelectrical feed and detecting the railway train in connection with the electrical feed based onthe electrical property. On detection of the railway train, the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation. 5ln one embodiment, the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation based on a position of the train. ln one embodiment, the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation based on a GPS-position of the train. ln one embodiment, the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation based on a timetable of the train. ln one embodiment, the electrical power buffer unit may further comprise communicationmeans arranged to receive and transmit information. The communication means may forexample be used to receive information relating to the position of the electrical power bufferunit, a position of a train, a speed of a train, a timetable of a train, a command to switch modeof operation and/or a combination thereof. The communication means may further be used tosend information relating to the position ofthe electrical power buffer unit, a position ofa train,a speed of a train, a timetable of a train, the present mode of operation, a command to switch mode of operation and/or a combination thereof.ln one embodiment, the control unit may be arranged inside the electrical power buffer unit.ln one embodiment, the control unit may be arranged outside the electrical power buffer unit. ln one embodiment, the control unit and the electrical buffer unit may communicate via a datacommunication link. The data communication link may for an example utilize one or a pluralityof different types of wired links or wireless links, such as for example xDSL, 2G, 3G, 4G, 5GTCP/IP, WiFi, Bluetooth, WiI\/lax, WLL, PSTN, optical fibre or a combination thereof. ln one embodiment, the data communication link between the control unit and the electricalbuffer unit may for an example utilize one or a plurality of different types of wired links orwireless links, such as for example xDSL, 2G, 3G, 4G, 5G TCP/IP, WiFi, Bluetooth, WiMax, WLL, PSTN, optical fibre or a combination thereof. ln one embodiment, the electrical power buffer unit may further comprise a powertransformation unit. The power transformation unit may be arranged to transform alternating current from the electrical feed to direct current for the electrical power buffer unit and to 6transform direct current from the electrical power buffer unit to alternating current for the electrical feed. ln one embodiment, the control unit may be arranged to detect a railway train in connectionwith the electrical feed by that a catenary voltage of the electrical feed is below a predefined level. ln one embodiment, the control unit may be arranged to detect a railway train in connectionwith the electrical feed by that a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the control unit may be arranged to detect a railway train in connectionwith the electrical feed by that a catenary voltage of the electrical feed is below a predefinedlevel and that a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the predefined level of the catenary voltage to detect a railway train in connection with the electrical feed may be in the span of 80% and 95% of a nominal voltage. ln one embodiment, the predefined level of the catenary voltage to detect a railway train in connection with the electrical feed may be 90% of a nominal voltage. ln one embodiment, the predefined level of power sent through the existing feedingtransformer ofthe track section to detect a railway train in connection with the electrical feed may be in the span of 30% and 50% of a nominal voltage. ln one embodiment, the predefined level of power sent through the existing feedingtransformer ofthe track section to detect a railway train in connection with the electrical feed may be 40% of a nominal voltage.

The term ”catenary voltage” in this context means the input voltage to the railway train, for example from the electrical feed or some other defined point along the catenary wire.

The term ”nominal voltage” in this context means the rated voltage of the component.

The term ”nominal power” in this context means the rated power of the component. 7ln one embodiment, the control unit may be arranged to detect a railway train is not inconnection with the electrical feed by that a catenary voltage of the electrical feed is over a predefined level. ln one embodiment, the control unit may be arranged to detect a railway train is not inconnection with the electrical feed by that the power sent through the existing feeding transformer of the track section is below a predefined level. ln one embodiment, the control unit may be arranged to detect that a railway train is not inconnection with the electrical feed by that a catenary voltage of the electrical feed is over apredefined level or that the power sent through the existing feeding transformer of the track section is below a predefined level. ln one embodiment, the predefined level of the power sent through the existing feedingtransformer of the track section to detect that a railway train is not in connection with the electrical feed may be in the span of 3% and 10%. ln one embodiment, the predefined level of the power sent through the existing feedingtransformer of the track section to detect that a railway train is not in connection with the electrical feed may be less than 5%. ln one embodiment, the predefined level of the power sent through the existing feedingtransformer of the track section to detect that a railway train is not in connection with the electrical feed may be 5%. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the first mode of operation to the second mode of operation when a catenary voltage of the electrical feed is below a predefined level. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the first mode of operation to the second mode of operation when a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unit from the first mode of operation to the second mode of operation when a catenary voltage of 8the electrical feed is below a predefined level and a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the predefined level ofthe catenary voltage to switch the electrical powerbuffer unit from the first mode of operation to the second mode of operation may be in the span of 80% and 95% of a nominal voltage. ln one embodiment, the predefined level ofthe catenary voltage to switch the electrical powerbuffer unit from the first mode of operation to the second mode of operation may be 90% of a nominal voltage. ln one embodiment, the predefined level ofthe catenary voltage to switch the electrical powerbuffer unit from the first mode of operation to the second mode of operation may be a threshold or a predefined level of a nominal voltage. ln one embodiment, the predefined level of power sent through the existing feedingtransformer of the track section to switch the electrical power buffer unit from the first modeof operation to the second mode of operation may be in the span of 30% and 50% of a nominal voltage. ln one embodiment, the predefined level of power sent through the existing feedingtransformer of the track section to switch the electrical power buffer unit from the first mode of operation to the second mode of operation may be 40% of a nominal voltage. ln one embodiment, the predefined level of power sent through the existing feedingtransformer of the track section to switch the electrical power buffer unit from the first modeof operation to the second mode of operation may be a threshold or a predefined level of a nominal voltage. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the second mode of operation to the first mode of operation when a catenary voltage of the electrical feed is over a predefined level. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unit from the second mode of operation to the first mode of operation when the electrical feed by 9that the power sent through the existing feeding transformer of the track section is below a predefined level. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the second mode of operation to the first mode of operation when a catenary voltage ofthe electrical feed is over a predefined level or that the power sent through the existing feeding transformer of the track section is below a predefined level. ln one embodiment, the predefined level of the power sent through the existing feeding transformer ofthe track section may be in the span of 3% and 10%. ln one embodiment, the predefined level of the power sent through the existing feeding transformer of the track section may be less than 5%. ln one embodiment, the predefined level of the power sent through the existing feeding transformer of the track section may be 5%. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the second mode of operation to the first mode of operation when the charge of the electrical power buffer unit is below a threshold or a predefined level. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the second mode of operation to the first mode of operation when the charge of theelectrical power buffer unit is below a value between 5% and 20% ofthe power capacity ofthe electrical power buffer unit. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the second mode of operation to the first mode of operation when the charge of theelectrical power buffer unit is below 10% of the power capacity of the electrical power buffer unit. ln one embodiment, the control unit may be arranged to maintain the electrical power bufferunit in the first mode of operation when the charge of the electrical power buffer unit is below a threshold or a predefined level. ln one embodiment, the control unit may be arranged to maintain the electrical power bufferunit in the first mode of operation when the charge of the electrical power buffer unit is below a value between 5% and 20% ofthe power capacity of the electrical power buffer unit. ln one embodiment, the control unit may be arranged to maintain the electrical power bufferunit in the first mode of operation when the charge of the electrical power buffer unit is below % of the power capacity of the electrical power buffer unit. ln one embodiment, the first mode of operation may further comprise detecting if the electricalpower buffer unit is charged over a threshold or a predefined level, and on detecting that the electrical power buffer unit is fully charged quit charging from the electrical feed. ln one embodiment, the first mode of operation may further comprise detecting if the electricalpower buffer unit is fully charged, and on detecting that the electrical power buffer unit is fully charged quit charging from the electrical feed.

According to one aspect of the invention a system for supplying electrical power to a railwaytrain, which takes advantage of at least one electrical power buffer unit is provided. The systemcomprises an electrical feed, an electrical power buffer and a control unit. The electrical feed isarranged to provide electrical power to the railway train. The electrical power buffer unit is inconnection with the electrical feed. The control unit is arranged to switch the electrical powerbuffer unit from a first mode of operation to a second mode of operation. The first mode ofoperation comprise charging the electrical power buffer unit from the electrical feed. Thesecond mode of operation comprise supplying electrical power from the electrical power bufferunit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed. ln one embodiment, the system for supplying electrical power to a railway train, takesadvantage of one electrical power buffer unit is provided. The system comprises an electricalfeed, an electrical power buffer and a control unit. The electrical feed is arranged to provideelectrical power to the railway train. The electrical power buffer unit is in connection with theelectrical feed. The control unit is arranged to switch the electrical power buffer unit from a firstmode of operation to a second mode of operation. The first mode of operation comprise charging the electrical power buffer unit from the electrical feed. The second mode of operation 11comprise supplying electrical power from the electrical power buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed. ln one embodiment, the electrical power buffer unit may supply power to the regional ordistribution network. The supply of power from the regional or distribution network may be via the feeding transformer. ln one embodiment, the feeding transformer may be arranged in connection via a rotating COnVe Fte F. ln one embodiment, the electrical feed may be arranged to be powered by a power distribution line. ln one embodiment, the electrical feed use an alternating current to supply electrical power toa railway train. By this, higher voltage may be used. By using higher voltages the losses are reduced. ln one embodiment, the electrical feed may be connected to the power distribution line via a transformer unit. The transformer unit is a feeding transformer of the track section. ln one embodiment, the electrical power buffer unit may be connected to the electrical feed viaa transformer unit. The transformer unit is arranged to supply electrical power from the electrical power buffer unit of similar specifications as the electrical feed. ln one embodiment, the system may further comprise one or more further electrical powerbuffer units and one or more further control units. The one or more further electrical powerbuffer unit may be in connection with the electrical feed. The one or more further control unitsmay be arranged to switch at least one ofthe one or more further electrical power buffer unitsfrom a first mode of operation to a second mode of operation. The first mode of operationcomprise charging the at least one of the one or more further electrical power buffer unit fromthe electrical feed. The second mode ofoperation comprise supplying electrical power from the at least one ofthe one or more further electrical power buffer unit to the electrical feed. ln one embodiment, the system may further comprise one or more further electrical powerbuffer units. The one or more further electrical power buffer unit may be in connection with the electrical feed. The control unit may further be arranged to switch at least one of the one or 12more further electrical power buffer units from a first mode of operation to a second mode ofoperation. The first mode of operation comprise charging the at least one of the one or morefurther electrical power buffer unit from the electrical feed. The second mode of operationcomprise supplying electrical power from the at least one of the one or more further electrical power buffer unit to the electrical feed. ln one embodiment, the system may further comprise one or more further control units. Theone or more further control units may be arranged to switch at least one or more furtherelectrical power buffer units from a first mode of operation to a second mode of operation. Thefirst mode of operation comprise charging the at least one or more further electrical powerbuffer units from the electrical feed. The second mode of operation comprise supplyingelectrical power from the at least one or more further electrical power buffer units to the electrical feed. ln one embodiment, the system may further comprise one or more further control units. Theone or more further control units may be arranged to switch the electrical power buffer unitfrom a first mode of operation to a second mode of operation. The first mode of operationcomprise charging the electrical power buffer unit from the electrical feed. The second mode ofoperation comprise supplying electrical power from the electrical power buffer unit to the electrical feed.ln one embodiment, the control unit may be arranged inside the electrical power buffer unit.ln one embodiment, the control unit may be arranged outside the electrical power buffer unit. ln one embodiment, the control unit and the electrical buffer unit may communicate via a datacommunication link. The data communication link may for an example utilize one or a pluralityof different types of wired links or wireless links, such as for example xDSL, 2G, 3G, 4G, 5GTCP/IP, WiFi, Bluetooth, WiI\/lax, WLL, PSTN, optical fibre or a combination thereof. ln one embodiment, the data communication link between the control unit and the electricalbuffer unit may for an example utilize one or a plurality of different types of wired links orwireless links, such as for example xDSL, 2G, 3G, 4G, 5G TCP/IP, WiFi, Bluetooth, WiMax, WLL, PSTN, optical fibre or a combination thereof. 13ln one embodiment, the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation based on a position of the train. ln one embodiment, the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation based on a GPS-position of the train. ln one embodiment, the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation based on a timetable of the train. ln one embodiment, the electrical power buffer unit may further comprise communicationmeans arranged to receive and transmit information. The communication means may forexample be used to receive information relating to the position of the electrical power bufferunit, a position of a train, a speed of a train, a timetable of a train, a command to switch modeof operation and/or a combination thereof. The communication means may further be used tosend information relating to the position ofthe electrical power buffer unit, a position ofa train,a speed of a train, a timetable of a train, the present mode of operation, a command to switch mode of operation and/or a combination thereof. ln one embodiment, the electrical buffer unit may communicate via a data communication link.The data communication link may for an example utilize one or a plurality of different types ofwired links or wireless links, such as for example xDSL, 2G, 3G, 4G, 5G TCP/IP, WiFi, Bluetooth, WiI\/lax, WLL, PSTN, optical fibre or a combination thereof. ln one embodiment, the electrical buffer unit may communicate with other electrical bufferunits via a data communication link. By this, information relating to the position ofthe electricalpower buffer unit, a position of a train, a speed of a train, a timetable of a train, the presentmode of operation, a command to switch mode of operation and/or a combination thereof maybe communicated. The data communication link may for an example utilize one or a plurality ofdifferent types of wired links or wireless links, such as for example xDSL, 2G, 3G, 4G, 5G TCP/IP,WiFi, Bluetooth, WiI\/lax, WLL, PSTN, optical fibre or a combination thereof. ln one embodiment, the electrical buffer unit may communicate with other electrical bufferunits via a data communication network. By this, information relating to the position of theelectrical power buffer unit, a position of a train, a speed of a train, a timetable of a train, the present mode of operation, a command to switch mode of operation and/or a combination 14thereof may be communicated. The data communication network may for an example utilizeone or a plurality of different types of wired links or wireless links, such as for example xDSL,2G, 3G, 4G, 5G TCP/IP, WiFi, Bluetooth, WiI\/lax, WLL, PSTN, optical fibre or a combination thereof.ln one embodiment, the power distribution network may use alternating current. ln one embodiment, the voltage in the power distribution network may be in the span of 10 kV and 132 kV. ln one embodiment, the voltage in the power distribution network may be 10 kV.ln one embodiment, the voltage in the power distribution network may be 20 kV.ln one embodiment, the voltage in the power distribution network may be 130 kV.ln one embodiment, the voltage in the power distribution network may be 132 kV. ln one embodiment, the frequency in the power distribution network may be in the span of 12.5 Hz and 60 Hz.ln one embodiment, the frequency in the power distribution network may be 50 Hz.ln one embodiment, the frequency in the power distribution network may be 16 2/3 Hz. ln one embodiment, the power in the power distribution network may have a voltage of 10 kV and a frequency of 50 Hz. ln one embodiment, the power in the power distribution network may have a voltage of 20 kV and a frequency of 50 Hz. ln one embodiment, the power in the power distribution network may have a voltage of 130 kV and a frequency of 50 Hz. ln one embodiment, the power in the power distribution network may have a voltage of 132 kV and a frequency of 16 2/3 Hz. ln one embodiment, the electrical feed may use alternating current. ln one embodiment, the frequency in the electrical feed may be 50 Hz. By this, the integration with other electrical infrastructure can be improved. ln one embodiment, the frequency in the electrical feed may be 60 Hz. By this, the integration with other electrical infrastructure can be improved. ln one embodiment, the power in the electrical feed may have a catenary voltage of 25 kV and a frequency of 50 Hz. ln one embodiment, the power in the electrical feed may have a catenary voltage of 12,5 kV or kV and a frequency of 60 Hz. ln one embodiment, the frequency in the electrical feed may be lower than the frequency usedin the power distribution network. By using lower frequencies difficulties with inductive reactance and losses due to eddy currents may be limited.ln one embodiment, the electrical feed may use low-frequency alternating current.

The term ”low-frequency” in this context means a frequency that is lower than the frequency used in local power distribution networks. ln one embodiment, the power in the electrical feed may have a catenary voltage of 12.5 kV or kV and a frequency of 25 Hz. ln one embodiment, the voltage in the electrical feed may be in the span of 10 kV and 20 kV.ln one embodiment, the voltage in the electrical feed may be 10 kV. ln one embodiment, the voltage in the electrical feed may be 12 kV. ln one embodiment, the voltage in the electrical feed may be 15 kV. ln one embodiment, the voltage in the electrical feed may be 16 kV. ln one embodiment, the frequency in the electrical feed may be in the span of 10 Hz and 25 Hz.ln one embodiment, the frequency in the electrical feed may be 12.5 Hz. ln one embodiment, the frequency in the electrical feed may be 16 2/3 Hz. 16 In one embodiment, the frequency in the electrical feed may be 25 Hz.

In one embodiment, the power in the electrical feed may have a catenary voltage of 15 kV and a frequency of 16 2/3 Hz.

In one embodiment, the power in the electrical feed may have a catenary voltage of 16 kV and a frequency of 16 2/3 Hz.

In one embodiment, the frequency in the electrical feed may be other than an even part ofthefrequency used in the power distribution network. By avoiding even parts ofthe frequency usedin the power distribution network, rotary converters can be used in transformers to generate power for the electrical feed while limiting overheating issues.

In one embodiment, the frequency in the electrical feed may be 16.7 Hz. By this overheating issues in transformers with rotary converters.In one embodiment, the electrical feed may use direct current.In one embodiment, the voltage in the electrical feed may be 800 V direct current.

In one embodiment, the voltage in the electrical feed may be 1500 V direct current. By this, theembodiment may be used in additional locations, such as for example parts ofJapan, Indonesia, Hong Kong, Ireland, etc.

In one embodiment, the voltage in the electrical feed may be 3000 V direct current. By this, theembodiment may be used in additional locations, such as for example parts of Belgium, Spain, Italy, Poland, Slovakia, Chile, etc.

In one embodiment, the voltage in the electrical feed may be between 600 V and 800 V directcurrent. By this, the embodiment may be used in additional locations, such as for example some tramways, trolleybus networks and subway systems.

In one embodiment, the electrical feed may use polyphase alternating current, such as for example a three phased alternating current system comprising two electrical feeds and a return.

In one embodiment, the electrical feed may use a non-contact system that provides the powerto the train by inductive coupling. This may be combined with a frequency in the electrical feed that is higher than the frequency in the power distribution network. 17According to one aspect of the invention a method for supplying electrical power to a railwaytrain, which takes advantage of an electrical power buffer unit is provided. The methodcomprises the steps of detecting a railway train, switching an electrical power buffer unit froma first mode of operation to a second mode of operation. The detection is of a railway train inconnection with an electrical feed. The switching of the electrical power buffer unit from a firstmode of operation to a second mode of operation is done on detecting the railway train. Thefirst mode of operation comprise charging the electrical power buffer unit from the electricalfeed. The second mode of operation comprise supplying electrical power from the electricalpower buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed. ln one embodiment, the method comprise the step oftransforming electrical power to a similarspecification as the electrical feed. By this, the supplied electrical power from the electrical power buffer unit is integrated in the electrical feed. ln one embodiment, the method may further comprise detecting a railway train not inconnection with the electrical feed and switching the electrical power buffer unit from thesecond mode of operation to the first mode of operation based on detecting the railway train not in connection with the electrical feed. ln one embodiment, the railway train may be detected by that the catenary voltage of the electrical feed is below a predefined level. ln one embodiment, the railway train may be detected by that a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the railway train may be detected by that the catenary voltage of theelectrical feed is below a predefined level and that a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the railway train in connection with the electrical feed may be detected by that a catenary voltage of the electrical feed is below a predefined level. ln one embodiment, the railway train in connection with the electrical feed may be detected bythat a predefined level of power is sent through the existing feeding transformer of the track section. 18ln one embodiment, the railway train in connection with the electrical feed may be detected bythat a catenary voltage of the electrical feed is below a predefined level and that a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the predefined level of the catenary voltage to detect a railway train in connection with the electrical feed may be in the span of 80% and 95% of a nominal voltage. ln one embodiment, the predefined level of the catenary voltage to detect a railway train in connection with the electrical feed may be 90% of a nominal voltage. ln one embodiment, the predefined level of power sent through the existing feedingtransformer ofthe track section to detect a railway train in connection with the electrical feed may be in the span of 30% and 50% of a nominal power. ln one embodiment, the predefined level of power sent through the existing feedingtransformer ofthe track section to detect a railway train in connection with the electrical feed may be 40% of a nominal power.

The term ”catenary voltage” in this context means the input voltage to the railway train from the electrical feed.

The term ”nominal power” in this context means the rated power of the component. ln one embodiment, that the railway train is not in connection with the electrical feed may be detected by that a catenary voltage of the electrical feed is over a predefined level. ln one embodiment, that the railway train is not in connection with the electrical feed may bedetected by that the power sent through the existing feeding transformer of the track section is below a predefined level. ln one embodiment, that the railway train is not in connection with the electrical feed may bedetected by that a catenary voltage of the electrical feed is over a predefined level or that thepower sent through the existing feeding transformer of the track section is below a predefined level. 19ln one embodiment, the predefined level of the power sent through the existing feedingtransformer of the track section to detect that a railway train is not in connection with the electrical feed may be in the span of 3% and 10%. ln one embodiment, the predefined level of the power sent through the existing feedingtransformer of the track section to detect that a railway train is not in connection with the electrical feed may be less than 5%. ln one embodiment, the predefined level of the power sent through the existing feedingtransformer of the track section to detect that a railway train is not in connection with the electrical feed may be 5%. ln one embodiment, switching from the first mode of operation to the second mode of operation may be when a catenary voltage of the electrical feed is below a predefined level. ln one embodiment, switching from the first mode of operation to the second mode ofoperation may be when a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, switching from the first mode of operation to the second mode ofoperation may be when a catenary voltage ofthe electrical feed is below a predefined level and a predefined level of power is sent through the existing feeding transformer of the track section. ln one embodiment, the predefined level ofthe catenary voltage to switch the electrical powerbuffer unit from the first mode of operation to the second mode of operation may be in the span of 80% and 95% of a nominal voltage. ln one embodiment, the predefined level of the catenary voltage to switch from the first mode of operation to the second mode of operation may be 90% of a nominal voltage. ln one embodiment, the predefined level of power sent through the existing feedingtransformer of the track section to switch the electrical power buffer unit from the first modeof operation to the second mode of operation may be in the span of 30% and 50% of a nominal power. ln one embodiment, the predefined level of power sent through the existing feedingtransformer of the track section to switch from the first mode of operation to the second mode of operation may be 40% of nomina| power. ln one embodiment, switching from the second mode of operation to the first mode of operation may be when a catenary voltage ofthe electrical feed is over a predefined level. ln one embodiment, switching from the second mode of operation to the first mode ofoperation may be when the electrical feed by that the power sent through the existing feeding transformer of the track section is below a predefined level. ln one embodiment, switching from the second mode of operation to the first mode ofoperation may be when a catenary voltage of the electrical feed is over a predefined level orthat the power sent through the existing feeding transformer of the track section is below a predefined level. ln one embodiment, the predefined level of the power sent through the existing feeding transformer ofthe track section may be in the span of 3% and 10%. ln one embodiment, the predefined level of the power sent through the existing feeding transformer ofthe track section may be less than 5%. ln one embodiment, the predefined level of the power sent through the existing feeding transformer of the track section may be 5%. ln one embodiment, switching from the second mode of operation to the first mode ofoperation may be when the charge ofthe electrical power buffer unit is below a threshold or a predefined level. ln one embodiment, the control unit may be arranged to switch the electrical power buffer unitfrom the second mode of operation to the first mode of operation when the charge of theelectrical power buffer unit is below a value between 5% and 20% ofthe power capacity ofthe electrical power buffer unit. ln one embodiment, switching from the second mode of operation to the first mode ofoperation may be when the charge ofthe electrical power buffer unit is below 10% ofthe power capacity of the electrical power buffer unit. 21ln one embodiment, the method may further comprise maintaining the first mode of operation when the charge of the electrical power buffer unit is below a threshold or a predefined level. ln one embodiment, the control unit may be arranged to maintain the electrical power bufferunit in the first mode of operation when the charge of the electrical power buffer unit is below a value between 5% and 20% ofthe power capacity of the electrical power buffer unit. ln one embodiment, the method may further comprise maintaining in the first mode ofoperation when the charge of the electrical power buffer unit is below 10% of the power capacity of the electrical power buffer unit. ln one embodiment, the first mode of operation may further comprise detecting if the electricalpower buffer unit is charged over a threshold or a predefined level, and on detecting that the electrical power buffer unit is fully charged quit charging from the electrical feed. ln one embodiment, the first mode of operation may further comprise detecting if the electricalpower buffer unit is fully charged, and on detecting that the electrical power buffer unit is fully charged quit charging from the electrical feed. ln one embodiment, the first mode of operation may further comprise detecting a railway train,switching an electrical power buffer unit from a first mode of operation to a second mode ofoperation or from a second mode of operation to a first mode of operation. The detection is ofa railway train in connection with an electrical feed. The switching ofthe electrical power bufferunit from a first mode of operation to a second mode of operation may be done on detectingthe railway train. The switching of the electrical power buffer unit from a second mode ofoperation to a first mode of operation may be done on not detecting the railway train. The firstmode of operation comprise charging the electrical power buffer unit from the electrical feed.The second mode of operation comprise supplying electrical power from the electrical powerbuffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed.

The electrical power buffer unit may be adapted to carry out any method described in disclosed embodiments.

The system may be adapted to carry out any method described in disclosed embodiments. 22 BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in the following illustrative and non-limiting detailed description of exemplary embodiments, with reference to the appended drawings, wherein: Figure 1 is a schematic illustration of an electrical power buffer unit according to a first aspect of the present invention.

Figure 2 is a schematic illustration of a system according to a second aspect of the invention.Figure 2b is a schematic illustration of a system according to one embodiment ofthe invention.Figure 2c is a schematic illustration of a system according to one embodiment of the invention.Figure 3 is a schematic illustration of a system according to one embodiment of the invention.

Figure 4 is a schematic illustration of a method according to a third aspect of the present invention.

Figure 5 is a schematic illustration of a method according to one embodiment ofthe invention.Figure 6a is a schematic illustration of a system according to known technology.

Figure 6b is a schematic illustration of a system according to one embodiment ofthe invention.Figure 6c is a schematic illustration of a system according to one embodiment of the invention.Figure 6d is a schematic illustration of a system according to one embodiment ofthe invention.

All figures are schematic, not necessarily to scale, and generally only show parts that arenecessary in order to elucidate the invention, wherein other parts may be omitted or merelysuggested. Throughout the figures the same reference signs designate the same, or essentially the same features.

DETAILED DESCRIPTION 23The present invention can be used to supplying electrical power to a railway train at least partlyusing an electrical power buffer unit which overcome or at least mitigate the problems of theprior art and with an improved functionality in a more robust construction that provides reliability benefits.

The invention is described in the following illustrative and non-limiting detailed description of exemplary embodiments, with reference to the appended drawings, wherein: Figure 1 shows a schematic illustration of an electrical power buffer unit 110 for supplyingelectrical power to a railway train, according to an embodiment of the present invention. Theelectrical power buffer unit 110 comprises connection means 111, charging means 112,supplying means 113 and a control unit 114. The electrical power buffer unit 110 is arranged toconnect to an electrical feed via the connection means 111. The electrical feed is in turnarranged to provide electrical power to the railway train. The control unit 114 is arranged toswitch the electrical power buffer unit 110 from a first mode of operation to a second mode ofoperation. The first mode of operation comprise using the charging means 112 to charge theelectrical power buffer unit 110 from the electrical feed via the connection means 111. Thesecond mode of operation comprise using the supplying means 113 to supply electrical powerfrom the electrical power buffer unit 110 to the electrical feed via the connection means 111, thereby providing electrical power to the railway train in connection with the electrical feed.

Figure 2 shows a schematic illustration of a system 200 for supplying electrical power to arailway train, according to an embodiment ofthe present invention. The system 200 comprisesan electrical feed 230, an electrical power buffer unit 210, a control unit 214 and connectionmeans 211. The electrical feed 230 is arranged to be able to provide electrical power to a railwaytrain. The electrical power buffer unit 210 is arranged in connection with the electrical feed 230 via the connection means 211.

The control unit 214 may be arranged to detect a railway train in connection with the electricalfeed 230. On detecting the railway train the control unit may switch the electrical power bufferunit from the first mode of operation to the second mode of operation. The control unit 214may be also be arranged to measure an electrical property on the electrical feed 230 and by thismeasurement detect the railway train in connection with the electrical feed based on the electrical property. The control unit 214 may also switch the electrical power buffer unit from 24the first mode of operation to the second mode of operation based on a timetable or a positionof the train, such as a GPS-position. The control unit 214 may also comprise communicationmeans arranged to receive and transmit information. The communication means may forexample be used to receive information relating to the position of the electrical power bufferunit, a position of a train, a speed of a train, a timetable of a train, a command to switch modeof operation and/or a combination thereof. The communication means may also be used tosend information relating to the position ofthe electrical power buffer unit, a position ofa train,a speed of a train, a timetable of a train, the present mode of operation, a command to switchmode of operation and/or a combination thereof. The control unit 214 and the electrical bufferunit 210 may communicate via a data communication link. The data communication link mayfor an example utilize one or a plurality of different types of wired links or wireless links, suchas for example xDSL, 2G, 3G, 4G, 5G TCP/IP, WiFi, Bluetooth, WiI\/lax, WLL, PSTN, optical fibreor a combination thereof. The control unit 214 may also be arranged to detect a railway train inconnection with the electrical feed by that a catenary voltage of the electrical feed 230 is belowa predefined level and/or by that a predefined level of power is sent through an existing feedingtransformer of a track section. The predefined level of the catenary voltage to detect a railwaytrain in connection with the electrical feed may be in the span of 80% and 95% of a nominalvoltage. The predefined level of power sent through the existing feeding transformer of thetrack section to detect a railway train in connection with the electrical feed 230 may be in thespan of 30% and 50% of a nominal voltage.The control unit 214 may also be arranged to detecta railway train is not in connection with the electrical feed 230 by that a catenary voltage oftheelectrical feed 230 is over a predefined level and/or by that the power sent through the existingfeeding transformer of the track section is below a predefined level. The predefined level of thepower sent through the existing feeding transformer of the track section to detect that a railway train is not in connection with the electrical feed may be in the span of 3% and 10%.

The control unit 214 may also be arranged to switch the electrical power buffer unit 210 fromthe second mode of operation to the first mode of operation when the charge of the electricalpower buffer unit 210 is below a threshold or a predefined level. The control unit 214 may alsobe arranged to maintain the electrical power buffer unit 210 in the first mode of operation whenthe charge ofthe electrical power buffer unit is below a predefined level. The predefined level may be in the span of 5% and 20% of the power capacity of the electrical power buffer unit. The control unit 214 may also be arranged to detect if the electrical power buffer unit 210 is fullycharged, and on detecting that the electrical power buffer unit 210 is fully charged quit charging from the electrical feed 230.

Figure 2b shows a schematic illustration of a system 200 for supplying electrical power to arailway train, according to an embodiment of the present invention, in a first mode of operation.The system 200 comprises an electrical feed 230, an electrical power buffer unit 210, chargingmeans 212 and a control unit 214. The electrical feed 230 is arranged to be able to provideelectrical power to a railway train. The electrical power buffer unit 210 is arranged in connectionwith the electrical feed 230 via connection means 211. The charging means 112 is arranged tocharge the electrical power buffer unit 110 from the electrical feed 230. The control unit 214 isarranged to operate the electrical power buffer unit 210 in a first mode of. The first mode of operation comprise charging the electrical power buffer unit 210 from the electrical feed 230.

The electrical power buffer unit 210 may comprise a transformer or a buffertransformer and/ora rotating converter that is arranged to supply electrical power from the electrical feed to theelectrical power buffer unit of similar specifications as the specifications from the electricalpower buffer unit. The electrical power buffer unit 210 may also comprise a powertransformation unit. The power transformation unit may be arranged to transform alternatingcurrent from the electrical feed 230 to direct current for the electrical power buffer unit 210.

The electrical feed 230 may use an alternating current to supply electrical power.

Figure 2c shows a schematic illustration of a system 200 for supplying electrical power to arailway train, according to an embodiment of the present invention, in a second mode ofoperation. The system 200 comprises an electrical feed 230, an electrical power buffer unit 210,supplying means 213 and a control unit 214. The electrical feed 230 is arranged to be able toprovide electrical power to a railway train, in the figure illustrated by a connection between therailway train 260 and the electrical feed 230. The electrical power buffer unit 210 is arranged inconnection with the electrical feed 230 via connection means 211. The supplying means 213 isarranged to supply electrical power from the electrical power buffer unit 110 to the electricalfeed 230. The control unit 214 is arranged to operate the electrical power buffer unit 210 in a second mode of operation. The second mode of operation comprise supplying electrical power 26from the electrical power buffer unit 210 to the electrical feed 230, thereby providing electrical power to the railway train in connection with the electrical feed.

The electrical power buffer unit 210 may comprise a transformer or a buffertransformer and/ora rotating converter that is arranged to supply electrical power from the electrical power bufferto the electrical feed of similar specifications as the specifications from the electrical feed. Theelectrical power buffer unit 210 may also comprise a power transformation unit. The powertransformation unit may be arranged to transform direct current from the electrical power buffer unit 210 to alternating current for the electrical feed 230.

Figure 3 shows a schematic illustration of a system 300 for supplying electrical power to arailway train, according to an embodiment ofthe present invention. The system 300 comprisesa power distribution line 340, an electrical feed 330, a first electrical power buffer unit 310, asecond electrical power buffer unit 320, a transformer unit 350, a railway train 360 and a railwaytrack section 370. The power distribution line 340 is arranged to transport electrical power. Theelectrical feed 330 is arranged to be able to provide electrical power from the power distributionline 340 to the railway train 360 on the railway track section 370. The electrical feed 330 isconnected to the power distribution line 340 by means of a transformer unit 350. The firstelectrical power buffer unit 310 comprises a first connection means 311, a first charging means312, a first supplying means 313 and a first control unit 314. The first control unit 314 is arrangedto switch the first electrical power buffer unit 310 from a first mode of operation to a secondmode of operation. The first mode of operation comprise using the first charging means 312 tocharge the first electrical power buffer unit 310 from the electrical feed 330 via the firstconnection means 311. The second mode ofoperation comprise using the first supplying means313 to supply electrical power from the first electrical power buffer unit 310 to the electricalfeed 330 via the first connection means 311. The second electrical power buffer unit 320comprises a second connection means 321, a second charging means 322, a second supplyingmeans 323 and a second control unit 324. The second control unit 324 is arranged to switch thesecond electrical power buffer unit 320 from a first mode of operation to a second mode ofoperation. The first mode ofoperation comprise using the second charging means 322 to chargethe second electrical power buffer unit 320 from the electrical feed 330 via the secondconnection means 321. The second mode of operation comprise using the second supplying means 323 to supply electrical power from the second electrical power buffer unit 320 to the 27electrical feed 330 via the second connection means 311. Thereby electrical power is provided to the railway train 360 in connection with the electrical feed on the railway track section 370.

The electrical power buffer units 310, 320 may also supply power to the regional or distributionnetwork 340. The supply of power from the regional or distribution network 340 may be via thefeeding transformer 350. The feeding transformer 350 may be arranged in connection via arotating converter. The electrical feed 330 may be connected to the power distribution line 340 via a transformer unit 350. The transformer unit is a feeding transformer of the track section.

The electrical power buffer units 310, 320 may also be connected to the electrical feed via atransformer unit. The transformer unit is arranged to supply electrical power from the electrical power buffer units 310, 320 of similar specifications as the electrical feed 330.

Both the first control unit 314 and the second control unit 324 may be used to control both thefirst and the second electrical power buffer units 310, 320. The control units 314, 324 and theelectrical buffer units 310, 320 may communicate via a data communication link. The datacommunication link may for an example utilize one or a plurality ofdifferent types ofwired linksor wireless links, such as for example xDSL, 2G, 3G, 4G, 5G TCP/IP, WiFi, Bluetooth, WiI\/lax, WLL, PSTN, optical fibre or a combination thereof Figure 4 shows a schematic illustration of a method 400 for supplying electrical power to arailway train, according to an embodiment of the present invention. The method comprisesdetecting 410 a railway train in connection with an electrical feed and on detecting the railwaytrain, switching 420 an electrical power buffer unit from a first mode of operation to a secondmode of operation. The first mode of operation comprise charging 430 the electrical powerbuffer unit from an electrical feed. The second mode of operation comprise supplying 440electrical power from the electrical power buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed.

The method may also comprise a step oftransforming electrical power to a similar specificationas the electrical feed. By this, the supplied electrical power from the electrical power buffer unit is integrated in the electrical feed.

The railway train may also be detected by that the catenary voltage of the electrical feed is below a predefined level and/or by that a predefined level of power is sent through the existing 28feeding transformer of the track section. The predefined level of the catenary voltage to detecta railway train in connection with the electrical feed may be in the span of 80% and 95% of anominal voltage. The predefined level of power sent through the existing feeding transformerof the track section to detect a railway train in connection with the electrical feed may be in the span of 30% and 50% of a nominal power.

Figure 5 shows a schematic illustration of a method 500 for supplying electrical power to arailway train, according to an embodiment of the present invention. The method comprisesdetecting 510 a railway train in connection with an electrical feed. The railway train may bedetected by a drop in the voltage in the electrical feed, by receiving information regarding thetrain from an external source or by a schedule. On detecting the railway train, and detecting550 that a power level of an electrical power buffer unit is above a threshold, switching 520 theelectrical power buffer unit from a first mode of operation to a second mode of operation. Ondetecting 550 that a power level of an electrical power buffer unit is below a threshold, theelectrical power buffer unit is maintained or switched to a first mode of operation. The firstmode of operation comprise charging 530 the electrical power buffer unit from an electricalfeed. The second mode ofoperation comprise supplying 540 electrical power from the electricalpower buffer unit to the electrical feed, thereby providing electrical power to the railway trainin connection with the electrical feed. When the electrical power buffer operates in a first mode,a railway train may be detected 510. Similarly, when the electrical power buffer operates in a second mode, a railway train may be detected 510.

The predefined level of the power sent through the existing feeding transformer of the tracksection to detect that a railway train is not in connection with the electrical feed may be in thespan of 3% and 10%. The predefined level of the catenary voltage to detect that a railway trainis not in connection with the electrical feed may be in the span of 80% and 95% of a nominal voltage. The power level threshold may be in the span of 5% and 20%.

Figure 6a shows a schematic illustration of a system for supplying electrical power to a railwaytrain, according to known technology. The system comprises an electrical feed 630, a feedingtransformer 651, a rotating converter 652, a railway train 660 and a railway track section 670.A power distribution line is arranged to transport electrical power to the system. The electrical feed 630 is arranged to be able to provide electrical power from the power distribution line to 29the railway train 660 on the railway track section 670. The electrical feed 630 is connected tothe power distribution line by means of the feeding transformer 651 and the rotating converter652. Thereby electrical power is provided to the railway train 660 in connection with theelectrical feed on the railway track section 670. The power in the power distribution line mayfor example be 20 kV or 130 kV at 50 Hz, the power between the feeding transformer and therotating converter may for example be 16 kV at 50 Hz, and the power in the electrical feed mayfor example be 16 kV at 16.7 Hz. The track section may for example be in the span of 50 km and 100 km.

Figure 6b shows a schematic illustration of a system for supplying electrical power to a railwaytrain, according to one embodiment of the invention. The system comprises an electrical feed630, an electrical power buffer unit 610, a buffer transformer 615, a feeding transformer 651, arotating converter 652, a railway train 660 and a railway track section 670. A power distributionline is arranged to transport electrical power to the system. The electrical feed 630 is arrangedto be able to provide electrical power from the power distribution line to the railway train 660on the railway track section 670. The electrical feed 630 is connected to the power distributionline by means of the feeding transformer 651 and the rotating converter 652. The electricalpower buffer unit 610 is connected between the feeding transformer 651 and the rotatingconverter 652 via the buffer transformer 615. Thereby electrical power is provided to therailway train 660 in connection with the electrical feed on the railway track section 670. Thepower in the power distribution line may for example be 20 kV or 130 kV at 50 Hz, the powerbetween the feeding transformer and the rotating converter may for example be 16 kV at 50Hz, and the power in the electrical feed may for example be 16 kV at 16.7 Hz. Thereby electricalpower is provided to the railway train 660 in connection with the electrical feed on the railway track section 670.

Figure 6c shows a schematic illustration of a system for supplying electrical power to a railwaytrain, according to one embodiment of the invention. The system comprises an electrical feed630, an electrical power buffer unit 610, a buffer transformer 615, a feeding transformer 651, arotating converter 652, a railway train 660 and a railway track section 670. A power distributionline is arranged to transport electrical power to the system. The electrical feed 630 is arrangedto be able to provide electrical power from the power distribution line to the railway train 660 on the railway track section 670. The electrical feed 630 is connected to the power distribution line by means of the feeding transformer 651 and the rotating converter 652. The electricalpower buffer unit 610 is connected to one end of the electrical feed 630 via the buffertransformer 615. Thereby electrical power is provided to the railway train 660 in connectionwith the electrical feed on the railway track section 670. The power in the power distributionline may for example be 20 kV or 130 kV at 50 Hz, the power between the feeding transformerand the rotating converter may for example be 16 kV at 50 Hz, and the power in the electricalfeed may for example be 16 kV at 16.7 Hz. The distance on the electrical feed 630 between theconnection of the power distribution line and the end at which the electrical power buffer unit610 is connected may for example be in the span of 25 km and 50 km. Thereby electrical poweris provided to the railway train 660 in connection with the electrical feed on the railway track section 670.

Figure 6d shows a schematic illustration of a system for supplying electrical power to a railwaytrain, according to one embodiment of the invention. The system comprises an electrical feed630, an electrical power buffer unit 610, a buffer transformer 615, a first feeding transformer651, a first rotating converter 652, a second feeding transformer 653, a second rotatingconverter 654 a railway train 660 and a railway track section 670. A power distribution line isarra nged to transport electrical power to the system. The electrical feed 630 is arranged to beable to provide electrical power from the power distribution line to the railway train 660 on therailway track section 670. The electrical feed 630 is connected to the power distribution line bymeans of the first feeding transformer 651 and the second feeding transformer 653. Theelectrical power buffer unit 610 is connected to the electrical feed 630 via the buffertransformer 615 at a position between the two connections to the power distribution line.Thereby electrical power is provided to the railway train 660 in connection with the electricalfeed on the railway track section 670. The power in the power distribution line may for examplebe 20 kV or 130 kV at 50 Hz, the power between the feeding transformer and the rotatingconverter may for example be 16 kV at 50 Hz, and the power in the electrical feed may forexample be 16 kV at 16.7 Hz. The track section between the two connections to the powerdistribution line may for example be in the span of 50 km and 100 km. Thereby electrical poweris provided to the railway train 660 in connection with the electrical feed on the railway track section 670. 31When the electrical power buffer operates in the first mode, and on detecting that a power levelof the electrical power buffer unit is over a second threshold, and no train is detected, theelectrical power buffer unit may switch to a stand-by mode in which the electrical power buffer does not charges or supplies.

When the electrical power buffer operates in the second mode, and on detecting that a powerlevel of the electrical power buffer unit is below a threshold, and a train is detected, the electrical power buffer unit may switch to the first mode of operation.

When the electrical power buffer operates in the first mode, and on detecting a railway train inconnection with an electrical feed the control unit may switch the electrical power buffer unit from the first mode of operation to the second mode of operation.

When the electrical power buffer operates in the second mode, and on detecting a railway trainin connection with an electrical feed the control unit may switch the electrical power buffer unit from the second mode of operation to the first mode of operation.

The voltage in the power distribution network may be in the span of 10 kV and 132 kV, forexample 10 kV, 20 kV, 130 kV or 132kV. The frequency in the power distribution network maybe in the span of 12.5 Hz and 60 Hz, for example 12.5 Hz, 16 2/3 Hz, 16.7 Hz, 20 Hz, 25 Hz, 30Hz, 50 Hz or 60 Hz. The power in the electrical feed may be alternative current and have avoltage in the span of 10 kV and 25 kV, for example 12.5 kV, 15 kV, 16 kV and 25 kV. Thefrequency in the electrical feed 630 may be in the span of 10 Hz and 60 Hz, for example 12.5 Hz,16 2/3 Hz, 16.7 Hz, 20 Hz, 25 Hz, 50 Hz and 60 Hz. The power in the electrical feed may also bedirect current and have a voltage in the span of 500 V and 10 kV, for example 800 V, 1.5 kV and3 kV. The electrical feed 630 may also use polyphase alternating current, such as for example a three phased alternating current system comprising two electrical feeds and a return.

The electrical feed 630 may use a non-contact system that provides the power to the train 660by inductive coupling. This may be combined with a frequency in the electrical feed 630 that is higher than the frequency in the power distribution network.

While specific embodiments have been described, the skilled person will understand thatvarious modifications and alterations are conceivable within the scope as defined in the appended claims.

Claims

1. CLAll\/IS

2. An electrical power buffer unit (110, 210, 310, 320, 610) for supplying electrical power to a railway train (260, 360, 660), wherein the electrical power buffer unit comprises: connection means (111, 211, 311) arranged to connect to an electrical feed, wherein the electrical feed is arranged to provide electrical power to the railway train; a power transformation unit (615) arranged to transform alternating current from theelectrical feed to direct current for the electrical power buffer unit and to transform direct current from the electrical power buffer unit to alternating current for the electrical feed; charging means (112, 212, 312) arranged to charge the electrical power buffer unit from the electrical feed; supplying means (113, 213, 313) arranged to supply electrical power from the electrical power buffer unit to the electrical feed; a control unit (114, 214, 314) arranged to switch the electrical power buffer unit from a first mode of operation to a second mode of operation; wherein the first mode of operation comprise charging the electrical power buffer unit from the electrical feed; and the second mode of operation comprise supplying electrical power from the electricalpower buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed.

3. Electrical power buffer unit according to claim 1, wherein the control unit is arranged todetect a railway train in connection with the electrical feed and on detecting the railwaytrain switching the electrical power buffer unit from the first mode of operation to the second mode of operation. 2Electrical power buffer unit according to claim 2, wherein the control unit is arranged tomeasure an electrical property on the electrical feed, detecting the railway train inconnection with the electrical feed based on the electrical property, and on detection ofthe railway train, switching the electrical power buffer unit from the first mode of operation to the second mode of operation.

4. A system (200, 300) for supplying electrical power to a railway train (260, 360, 660), whichtakes advantage of at least one electrical power buffer unit according to any one claim 1 to 43", wherein the system comprises: an electrical feed (230, 330, 630) that is arranged to provide electrical power to the railway train;an electrical power buffer unit (110, 210, 310, 610) in connection with the electrical feed; a control unit (114, 214, 314) arranged to switch the electrical power buffer unit from a first mode of operation to a second mode of operation; wherein the first mode of operation comprise charging the electrical power buffer unit from the electrical feed; and the second mode of operation comprise supplying electrical power from the electricalpower buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed.

5. System according to anyazmeeclaim ~1~>2 powered by a power distribution line (340).

6. System according to claim 5, wherein the electrical feed is connected to the power distribution line via a transformer unit (350, 651, 653). 3

7. System according to any one claim 4 to 6, further comprising: one or more further electrical power buffer units (320) in connection with the electrical feed; and one or more further control units (314) arranged to switch at least one of the one or morefurther electrical power buffer units from a first mode of operation to a second mode of operation; wherein the first mode of operation comprise charging the at least one of the one or morefurther electrical power buffer units electrical power buffer unit from the electrical feed; and the second mode of operation comprise supplying electrical power from the at least one of the one or more further electrical power buffer units to the electrical feed.

8. Method (400, 500) for supplying electrical power to a railway train, which takes advantageof an electrical power buffer unit according to any one claim 1 to 313, wherein the method comprises the steps of:detecting (410, 510) a railway train in connection with an electrical feed; on detecting the railway train, switching (420, 520) an electrical power buffer unit from a first mode of operation to a second mode of operation; wherein the first mode of operation comprise charging (430, 530) the electrical power buffer unit from the electrical feed; and the second mode of operation comprise supplying (440, 540) electrical power from theelectrical power buffer unit to the electrical feed, thereby providing electrical power to the railway train in connection with the electrical feed.

9. Method according to claim 8, further comprising:

10.

11.

12.

13.

14. 4detecting a railway train not in connection with the electrical feed and switching theelectrical power buffer unit from the second mode of operation to the first mode of operation. Method according to claim 8, wherein the railway train is detected by that a catenaryvoltage of the electrical feed is below a predefined level or that a predefined level of power is sent through the existing feeding transformer of the track section. Method according to claim 8, wherein switching the electrical power buffer unit from thefirst mode of operation to the second mode of operation when a catenary voltage of theelectrical feed is below a predefined level or when a predefined level of power is sent through the existing feeding transformer of the track section. Method according to claim 8 or 11, further comprising: switching the electrical power buffer unit from the second mode of operation to the firstmode of operation when a catenary voltage of the electrical feed is over a predefined levelor that the power sent through the existing feeding transformer of the track section is below a predefined level. Method according to anyf one claim 8 to 12, further comprising: switching the electrical power buffer unit from the second mode of operation to the firstmode of operation when the charge of the electrical power buffer unit is below a threshold or a predefined level. Method according to any one claim 8 to 13, further comprising: 5maintaining the first mode of operation when the charge of the electrical power buffer unit is below a threshold or a predefined level.