GB2527881A

GB2527881A - Drive system

Info

Publication number: GB2527881A
Application number: GB1505107.1A
Authority: GB
Inventors: Yuta Oura; Satoru Inarida; Kento Mochizuki; Yoshitaka Nishimura; Takahiro Yamauchi; Motomi Shimada
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2014-04-03
Filing date: 2015-03-26
Publication date: 2016-01-06
Anticipated expiration: 2035-03-26
Also published as: GB201505107D0; JP6232331B2; GB2527881B; JP2015198544A; DE102015205846A1; DE102015205846B4

Abstract

A drive system for a formation-train having an applied phase difference control comprises a main transformer 2 for stepping down AC electric power from a catenary 3, a plurality of power converters each having a converter 11 for converting AC power from the transformer 2 into DC power and an inverter 13 for converting the DC power into AC power, and a main electric motor 4 to be driven by power from the inverter 13, wherein the number of power converters in operation or the output thereof is altered on the basis of a threshold current limit from the catenary 3. Alternatively the number of operable power converters is decided on the basis of a threshold current limit from the catenary 3 and the power converter reduces power supplied to the motor 4 on the basis of the number of operable power converters. On the basis of an electric car performance at the power converters, either the number of converters in operation or their output may be changed.

Description

DESCRIPTION

TITLE OF THE INVENTION

DRIVE SYSTEM

FIELD OF THE INVENTION

The invention relates to a drive system for a formation-train provided with a power converter.

BACKGROUND OF THE INVENTION

A train formed by use of railway cars, with an inverter drive systemusingapower converter, appliedthereto, has since become prevalent. In general, the power converter used in the inverter drive system is of a configuration in which a converter for convorting ac into dc is usod. For tho convortor, a PM'4 converter adopting PWM is in widespread use, the PWM converter being made up of bridge-connected diodes, each of the diodes with a self turn-off type switching element, connected in inverse-parallel thereto.

Upon execution of a switching operation in the PM"J converter, harmonics centering on a freguency corresponding to an integral multiple of a carrier frequency (hereinafter referred to as "integral multiple harmonics") appear on the power supply side of the PWM converter. In the case of a train with a large number of the PWM converters mounted therein, the integral multiple harmonics are multiplexed by the number corresponding to the number of the units of the PWM converter, and those harmonics appear on the power supply side to thereby affect the operation of an infrastructure, such as a signal, etc. In the case of a drive systemwith a large number of railway cars mounted therein, a converter being used in each of the railway cars, the system is operated with a phase-difference in carrier, provided among plural units, each thereof being made up of a PWM converter provided on the secondary winding side of a transformer for receiving a single-phase electric current from a catenary, between transformers for receiving an electric power from the catenary, andbetween the fornations, respectively, in order to reduce harmonics generated. In Japancsc Uncxamincd Patcnt Application Publication No. Hci 7 (1995) -308004 (Patent Document 1) , it has been disclosed that appearance of integral multiple harmonics is controlled by application of a carrier phase-difference operation.

Because the maximum electric power supply of a substation has a threshold limit value upon starting the operation of a train, if all the power converters in the formed-train are operated at the maximum output, this will cause a catenary current to be restricted due to the case where the threshold limit value of the substation is exceeded, and so forth, thereby leading to the case where control of the power converters in the formation is altered. Tn the case where a train with the carrier phase-difference operation applied thereto is in such a state as above, if the control of the power converters in the formation-train is altered without taking the phase-difference control into consideration in order to satisfy the thresholdlimitvalueof the catenarycurrent, arelationship in phase-difference between respective equipment, set in order to control the appearance of the integral multiple harmonics, and it is presumed that the harmonic component on the power supply side will increase.

However, in Patent Document 1, how to cope with the case where the relationship in phase-difference no longer holds is not taken into consideration. As a result, an increased harmonic frequency on the power supply side, and a frequency of an infrastructurc signal ovorlap cachothcr, thcrcby raising the risk of adversely affecting actions of the infrastructure.

It is an object of the present invention to provide a method for selecting a power converter whose control is to be changed in the case of altering the control of a power converter, while controlling an increase in a harmonic component on a power supply side.

SU1'ThJARY OF THE INVENTION To that end, in accordance with one aspect of the present invention, there isprovidedadrive systemof a formation-train with a phase-difference control applied thereto, and the drive system includes a main transformer for stepping down an ac electric power supplied from a catenary, a converter for converting the ac electric power supplied from the main transformer into a do electric power, an inverter for oonverting the do eleotrio power supplied from the oonverter into an ac electric power, and a main electric motor to be driven by the ac electric power supplied fron the inverter. Further, the drive system includes a plurality of power converters, each thereof being made up of the converter and the inverter, and the number of the units of the power converters in operation or an output of the plurality of power converters is altered on the basis of a threshold limir value of an electric current from a catenary.

Or, in accordance with another aspect of the present invontion, thoro isprovidodadrivo systomof a formation-train with a phase-difference control applied thereto, and the drive system includes a main transformer for stepping down an ac electric power supplied from a catenary, a converter for converting the ac electric power supplied from the main transformer into adc electric power, aninverter for converting the dc electric power supplied from the converter into an ac electric power, and a main electric motor to be driven by the ac electric power supplied fron the inverter. Further, the drive system includes a plurality of power converters, each thereof being made up of the converter and the inverter, and the number of operatable units of The power converters is decided onthebasisofthethresholdlimitvalueofthecatenarycurrent, and the power converter by itself reduces an electric power supplied to the main electric motor on the basis of the number of the operatable units of the power converters, and formation-information.

The application of the present invention will render it possible to control an increase in the harmonic component on the power supply side even if the control of the power converter is altered in the case where the catenary current is restricted.

BRIEF DFSCRTPTTON CF THE DRWTNGS

Fig. 1 is a view for illustrating an example of a formation-train with a phase-difference control applied thereto; Fig. 2 isaviowfordoscribingadovicoinwhichsoloction according to the present invenilon is executed; Fig. 3 is a view for describing a generation state of a harmonic centering on a frequency corresponding to an integral multiple of a carrier frequency, in an example of the formation of Fig. 1, with the phase-difference control applied thereto; Fig. 4 is a view for describing a method of selecting operatable units of the power converters, according to the present invention; Fig. 5 is a view for describing the generation state of harmonics in the case of the selection method according to the present invention being applied to an example of the formation train with the phase-difference control applied thereto, (case (1)); Fig. 6 is a view for describing the generation state of harmonics in the case of the selection method according to the present invention being applied to an example of the formation train with the phase-difference control applied thereto, (case (2) Fig. 7 is a view for describing the generation state of harmonics in the case where the selection method according to the present invention is not applied to an example of the formation-train with the phase-difference control applied thereto; Fig. 8 is a view for describing a method of selecting thc powcr convcrtcr, roprcscnting anothcr mcthod according to the present invention; Fig. 9 is a view for describing the generation state of harmonics in the case where the selection method as the other method according to the present invention is applied to an exampleof the formationtrainwith thephase-difference control applied thereto; and Fig. 10 is a view for describing the generation state of integral multiple harmonics in a formation-train in which the formation is made up of two groups of the converters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Ernbcdiments of the present invention are described below with reference to the accompanying drawings.

Embodiment 1 Fig. 1 is a view for illustrating an example of a formation-train (hereinafter referred to as formation") with a phase-difference control applied thereto. With the train shown in Fig. 1, the formation is made up of nine cars, including cars, numbered 2, 3, 5, 7, 8, respectively, as drive cars, (the carwiththepcwerconvertermountedtherein) andcars, numbered 1, 4, 6, 9, respectively, as trail cars (the car without the power converter mounted therein) A power converter with three elements (a converter, an inverter, and a filter capacitor) mounted therein, together withamainelectricmotor, ismountedin the drive car. Further, a currcnt colloctor and a main transformor arc mountod in cach of the cars 1, 4, and 9. still further, a drive system having a means for controlling the power converter is mounted in the formation.

The drive system mounted in the formation is described below with reference to Fig. 2. An onboard contrcller is provided with a means for deciding the number of operatable units of the power converters on the basis of the threshold limit value of the cateriary current delivered to the onboard controller, and a means for selecting a power converter to be operated on the basis of the number of the operatable units of the power converters, and formation-information. The formation-informationincludesthenurnberofthecars formaking

B

up the formation-train, information on equipment provided, running time running speed between stations, and so forth.

Referring to Fig. 3, there isdescribedbelowageneration state of low-order harmonics in the formation of Fig. 1, with the phase-difference control applied thereto. In the case of executing the phase-difference control by imparting a 900 phase-difference in carrier between the power converters, provided in respective main transformers of the cars 1, 9, a 450 phase-difference in carrier between the respective main transformers of the cars 1, 9, and a 22. 5° phase-difference in carrier between the respective main transformers of the cars 1, 4 as well as between the respeotive main transformers of thc cars 4, 9, this will causo frcquoncycompononts, oachthoroof oentering on a frequency component 2fs at a frequency twice ashighas acarrier frequencyfs cohavea 180°phase-difference therebetween, thereby cancelling each other out. Furthermore, frequency components, each thereof centering on a frequency component 4fs at a frequency four times as high as the carrier frequency fs will also cancel each other out, and a frequency component 8fs, that is, a frequency component at a frequency eight times as high as the carrier frequency fs will appear on the power supply side.

The frequency component Bfs at the frequency eight times as high as the carrier frequency fs is reduced due to the 22.5° phase-difference between the respective main transformers of the car 4 and the car 1 as well as between the respective main transformers of the oar 4 and the oar 9. However, beoause both the frequency oomponent 2fs at the frequenoy twioe as high as the carrier frequency fs, and the frequency component 4fs at the frequency four times as high as the carrier frequency fs, generated by the car 5, cannot be cancelled out, the frequency component 2fs, at the frequency twice as high as the carrier frequency fs, and the frequency component 4fs, at the frequency four times as high as the carrier frequency fs, which are generated from the power converter of the carS, will each appear on the power supply side.

Referring to steps (1) to (6) infig.4, there is described bolow tho moans for solocting a powor convortor to bo oporatcd on the basis of the number of the operatable units of the power converters, and the formation-information.

Inthestep (1) ofprocessing, thenumberoftheoperatable units of the power converters is compared with the number of the units of the power converters in operation at present, and if formula of the number of the operatable units of the power converters »= the number of the units of the power converters in operation at present" is satisfied, selection is conpleted, and if not, the processing proceeds to the step (2) If the main transformer provided with only one unit of the power converter exists in the formation in the step (2), the only one unit of the power converter provided in the main 10' transformer is stopped in the step (3) On the other hand, if the main transformer provided with only one unit of the power converter does not exist in the step (2) , all the power converters in respective units made up of thepowerconvertersprovidedinthemaintransformerarestopped by the processing in the step (4) In the step (5) after the processing in the steps (3) (4) , check is made on whether or not the present electric-car performance is insufficient against the electric-car performance necessary for the operation of the train. If the present electric-carperformance is sufficient, the processing reverts to the step (1) again.

Onthoothorhand, ifthoprcsontoloctric-carporformancc is determined insufficient, all the power converters stopped in the immediately preceding steps (3), (4), respectively, are operated in the step (6) . Subsequently, the electric-car characteristics of the power converter in operation at the present time is altered in such a way as to satisfy the threshold limit value of the catenary current, thereby conpleting selection.

With the formation-train having such a configuration as described above, if the number of the operatable units of the power converters, against the threshold limit value of the catenary current, is three, a selection flow in the case of adopting a selection method according to the present invention is described below with reference to Fig. 4.

In the step (1), the number of the units of the power converters in operation at present is five, which is more than the number of the operatable units of the power converters, that is, three, and therefore, the processing proceeds to the step (2) In the step (2) , there is described the case of "the main transformer provided with only one unit of the power converter exists in the formation", and the main transformer of the car 4 is reievant thereto, the processing therefore proceeding to the step (3) , and the power converter of the car 5 is stopped.

The processing proceeds to the step (5) , and if tho oloctnic-car porformanco is dotorminod as sufficiorit against "the electric-car performance is sufficient", the processing reverts to the step (1) again.

In the step (1), the number of the units of the power converters in operation at present is four, which is more than the number of the operatable units of the power converters, that is, three, and therefore, the processing proceeds to the step (2) Because the main transformer provided with only one unit of the power converter in the formation does not exist in the step (2) , the processing proceeds to the step (4) In the step (4) , there is described the case of "the main transformer provided with the power converters, the number of theunitsthereofbeingthesmallest", andbecausetherespective main transformers of the cars 1, 9, are each provided with two units ofthepowerconverters, identical innumberto eachother, the respective main transformers of the cars 1, 9, are relevant thereto, aridtherefore, eitherof the cars 1, 9, maybe selected.

With the present embodiment, the car 9 is selected, therefore, the respective power converters of the cars 7, and 8, provided in the main transformer of the car 9, are stopped as the case of "Stop all the power converters of the main transformer, the number of the units of the power converters provided in the main transformer being the smallest".

The processing proceeds to the step (5) , and if the cicotric-car porformanco is dotorminod as sufficiont, tho processing reverts to the processing in the step (1) again.

In the step (1), the number of the units of the power converters in operation at present is two, which is less than three, that is, the number of the operatable units of the power converters, completing therefore selection. As the result of the selection, the respective power converters of the cars 5, 7, 8, are stopped.

The generation state of low-order harmonics in The case of the selection being made as above is described below with reference to Fig. 5. The frequency components, each thereof centering on the frequency component 2fs at the frequency twice as high as the carrier frequency fs will have a 1800 phase-difference therebetween, due to phase-difference in carrier between the cars 2, 3, thereby canceiling each cther out, whiie the frequency component 4fs at the frequency four times as high as the carrier frequency fs will appear, as the lowest frequency component, on the power supply side.

Next, there is described below the case where the eiectric-car performance is determined as insufficient aqainst determination process step "Is the electric-car performance sufficient ?" in the step (5) subsequent to the steps (l)-* (2) -3 (3) -3 (5) -3 (1) -5 (2) -5 (4), in the selection-flow described as above. If the electric-car performance is determined as insufficient against the step "Is the electric-car porformancc sufficicnt ?", thc proccesing prococds to thc stop (6).

With the present embodiment, because the respective power converters of the cars 7, and 8, provided in the main transformer of the car 9, are stopped in the step immediately preceding step (4) / the respective power converters of the cars 7, and 8 are operated according to "Operate all the power converters stopped in the immediately preceding step", as described in the step (6) . Then, the power converters in the present state being the power converters mounted in the cars 2, 3, 7, 8, respectively, the respective electric-car performances of all the power converters are altered in such a way as to be within the threshold limit value of the catenary current, as the case of "altering electric-car characteristics of the power converter inapresent state", thereby completing the selection.

As the result of the selection, only the power converter of the car S is stopped, and the electric-car characteristics of therespectivepowerconvertersofthecars2, 3,7, 8arealtered.

The generation state of low-order harmonics in the case of the selection being made as above is described below with reference to Fig. 6. The frequency components, each centering on the freguency component 2fs at the frequency twice as high as the carrier frequency fs, will have a 1800 phase-difference therebetween, due to carrier phase-difference among the cars 2, 3, 7, 8, thereby cancelling each other out, and the frequency componont 4fs at tho froquoncy four timos as high as tho carrior frequency fs is cancelled out, while the frequency component 8fsatthe frequencyeighttimesashighas thecarrierfrequency fs, as the lowest frequency component, will appear on the power supply side.

Referring to Fig. 7, the generation state of low-order harmonics inthecaseof stoppingtherespectivepowerconverters ofthecars3, 7withouttheuseoftheselectionmethodaccording to the present invention is described.

Because the number of the units of the power converters provided in the respective main transformers of the cars 1, 4, 9 is only one unit, the freguency components, each thereof centering on the frequency component 2fs at the frequency twice as high as the carrier frequency fs, cannot cancel each other out. More specifically, the effect of controlling appearance of the low-order harmonic, due to the phase-difference control, cannot be obtained, so that the components centering on the frequency component 2fs at the frequency twice as high as the carrier frequency fs, having appeared from the power converters of the cars 2, 5, 8, respectively, will appear after being multiplexed. Thils, by altering the output control of the power converters, without disturbing a relationship in phase-difference between the respective equipment, it is possible to control the appearance of the low-order harmonics, on the power supply side.

Embodimont 2 Subsequently, Embodiment 2 as another embodiment of the present invention is described below with reference to (1) (2), in Fig. 8.

If the number of the operatable units of the power converters, against the threshold limit value of the catenary current, isthreeinthe formationtrainhavingthe configuration of Fig. 1, this is taken as relevant to processing under (1) "Stop a power converter at random in order to satisfy formula of "the number of the operatable ilnits of the power converter against the threshold limit value of the catenary current= the number of the units of the power converters in operation at present", andtherefore, thepowerconverterisstoppedatrandom without taking a phase-difference into consideration. With the present embodiment, the number of the units of the power converters inoperationatpresent is five, andtherefore, there is the need for stopping two units of the power converters, so that respective power converters of the cars 3, 7 are stopped and processing proceeds to (2) With the present embodiment, this is taken as the case of wReset a phase-difference with respect to all the power converters in operation at present", as stated under (2) , and therefore, a 600 phase-difference is reset to carriers of the respective power converters in operation at present, with respect to the cars 2, 5, 8.

Rofcrring to Fig. 9, thoro is doscribod bclow tho generation state of low-order harmonics in the case of resetting the phase-difference, as described above.

Due to a carrier phase-difference with respect to the cars 2, 5, 8, the frequency components, each thereof centering on the frequency component 2fs at the frequency twice as high as the carrier freguencyfs, will have the 180°phase-difference therebetween, thereby cancelling each other out, while the frequency component centering on the frequency component 4fs at the frequency four times as high as the carrier frequency fs, as the lowest frequency component, will appear on the power supply side.

Although it has been described that the power converter according to the present invention is selected by use of the onboard controiler, it is to be understood that the onboard controlier is not an essential item in the present invention.

Even in the case where a means for execution of the selection is a drive system provided in the respective power converters within the formation, it goes without saying that the selection method according to the presenc invention is applicable.

As the embodiment of the present invention, the formation of Fig. 1 has been described by way of example. However, the configuration of the formation of Fig. 1 is not an essential item in the present invention. It is to be pointed out that the present invention is applicable regardless of the number of tho units of tho powor convortors providod in tho main transformer within the formation-train, the number of the units of the main transformers within the formation, and joining of the formations with eaoh other. However, the frequenoy that appears on the power supply side will vary according to the configuration of the formation. In the case of the formation of Fig. 1, the power converter is made up of one group of the converters, so that the frequency, as shown in Fig. 3, will appear. Onthe otherhand, inthe casewhere thepowerconverter in the formation is made up of two groups of the converters, the frequency will shift to a frequency higher by double the frequency generated on the power supply side in the case where the power converter is made up of only one group, as shown in Fig. 10.

List of Reference Signs 1: power converter, 11: converter, 12: filter capacitor, 13: inverter, 2: main transformer, 3: current collector, 4: main electric motor, 5: onboard conoroller

Claims

CLAIMS1. A drive system of a formation-train with a phase-difference control applied thereto, the drive system comprising: a main transformer for stepping down an ac electric power supplied from a catenary; a converter for converting the ac electric power supplied from the main transformer into a do electric power; an inverter for converting the do electric power supplied from the converter into an ac electric power; and a main electric motor to be driven by the ac electric powor suppliod from tho invortor, tho drivo systom furthor comprising a plurality of power converters, each thereof being made up of the converter and the inverter, wherein the number of the units of the power converters in operation or an output of the plurality of power converters is altered on the basis of a threshold limit value of an electric current from a catenary.
2. The drive system according to claim 1, wherein a phase-difference of the power converter in operation is reset.
3. The drive system according to claim 1 or 2, wherein, on the basis of an electric-car performance at the number of units of the power converters already in 20' operation, eitherthenumberoftheunitsortheoutputisdecided to be changed.
4. A drive system of a formation-train with a phase-difference control applied thereto, the drive system comprising: a main transformer for stepping down an ac electric power supplied from a catenary; a converter for converting the ac electric power supplied from the main transformer into a do electric power; an inverter for converting the do electric power supplied from the converter into an ac electric power; and a main electric motor to be driven by the ac electric powcr supplicd from thc invcrtcr, thc drivc systcm furthcr comprising a plurality of power converters, each thereof being made up of the converter and the inverter, wherein the number of operatable units of the power converters is decided on the basis of a threshold limit value of an electric current from the catenary, and the power converter by itself reduces an electric power supplied to the main electric motor on the basis of the number of the operatable units of the power converters, and formation-information.
5. The drive system according to claim 4, wherein the power converter reduces an output by stopping the power converter itself on the basis of the number of the operatable units of the power converters, and the formation-information, or by altering an electric-car performance of the power converter itself.
6. The drive system according to claim 5, wherein a determination is made on whether or not an electric-car performance at the number of units of the power converters already in operation is sufficient for the operation of the formation-train, and execution of either the stopping or reduction in the output is selected.C