EP0763833A2 - Transformer for an electrically driven vehicle - Google Patents

Abstract

The transformer has an integral noise current filter winding (FiW) which uses one or more layers of the high voltage winding adjacent to the low voltage winding, whereby an autotransformer circuit is formed involving the noise filter winding. At least one filter connected to the filter winding connections (Fi) consists of a series circuit contg. at least one filter resistance and a filter capacitor. The filter winding can be separately arranged between the high and low voltage windings with a filter connected to its connections.

Description

The invention relates to a transformer for an electrically driven vehicle.

Electric locomotives and railcars for AC railways usually have a transformer on the input side. Modern vehicles have power converters for drive control, which are connected to the secondary side of the transformer. Vehicles with three-phase drive technology usually also have converters on the network side (four-quadrant controller = 4QS), with which an almost sinusoidal network current curve can be achieved. However, the clock frequency of the line-side converters results in undesirable higher harmonics in the line current of the vehicle, the frequency of which extends into the audio frequency range. They must be limited with regard to possible adverse effects on railway signal systems and telephone cables.

Drehstromantriebstechnik: Entwicklung und Bewährung neuer elektrischer Komponenten am Beispiel der Lokomotiven der Baureihe (BR) 120 der DB" oder aus der AEG/ABB/Siemens-Druckschrift VT 62.89/26

Triebköpfe der Baureihe 401 des Hochgeschwindigkeitszuges ICE für die Deutsche Bundesbahn (siehe Seite 2, Bild 2) bekannt und in Fig. 9 dargestellt ist. Darin ist die Wirkung der taktenden Vierquadrantensteller in einer resultierenden, auf die Primärseite umgerechneten Stellerspannung Ust' zusammengefaßt (U0 = Netzspannung, U1 = Eingangsspannung). Ohne weitere Filterelemente werden die Harmonischem im Netzstrom im wesentlichen nur durch die Kurzschlußinduktivität LT zwischen Ober- und Unterspannungsseite (OS und US) des Transformators bestimmt. Dabei sei die Netzimpedanz Z0 klein gegen LT. Um sie abzuschwächen, wird dem Transformator der Filterquerzweig, bestehend aus Filterkondensator (Filterkapazität) CF*, Filterwiderstand (Dämpfungswiderstand) RF*, vorgeschaltet. Bei kleiner Netzimpedanz ZO kann eine Filterwirkung nur erzielt werden, wenn zusätzlich noch eine Filterdrossel (Filterinduktivität) LF* in den Längszweig geschaltet wird. Da sie vom vollen Eingangsstrom I1 (Netzstrom) durchflossen wird, läßt sich mit vertretbarem Aufwand nur eine Induktivität LF* realisieren, die wesentlich kleiner ist als LT. Abschwächend wirkt das Filter nur für Frequenzen, die hinreichend oberhalb der durch LF* und CF* bestimmten Filtereigenfrequenz liegen. Daraus folgt eine Mindestgröße für CF*. Der Filterwiderstand RF* ist notwendig, um die Neigung des Filters zu Resonanzen zu begrenzen. Nachteilhaft an diesem bekannten Filterkonzept sind folgende Gesichtspunkte:

• Alle Filterelemente sind auf der Primärseite des Transformators und müssen also hochspannungsmäßig ausgelegt und gestaltet werden. Dies ist besonders aufwendig für die vom Hauptstrom durchflossene Filterdrossel.
• Die kleine realisierbare Filterinduktivität LF* zieht eine entsprechend große Filterkapazität CF* nach sich, um die gewünschte Eigenfrequenz zu erreichen. Sie bedingt entsprechend große Verluste im Dämpfungswiderstand RF* schon allein durch den Grundschwingungs-Ladestrom.
• Das Filter erniedrigt die Eingangsimpedanz des Fahrzeuges und kann beim Vorhandensein von Harmonischen in der Netzspannung den Störstrom sogar erhöhen.

In order to weaken the mains current harmonics in the audio frequency range, an interference current filter was previously connected upstream of the transformer on the primary side, such as from the BBC publication DVK 1357 85D,

Three-phase drive technology: Development and testing of new electrical components using the example of locomotives of the series (BR) 120 of the DB "or from the AEG / ABB / Siemens publication VT 62.89 / 26

Driving heads of the 401 series of the ICE high-speed train for the Deutsche Bundesbahn (see page 2, figure 2) are known and shown in Fig. 9. The effect of the clocking four-quadrant actuators is summarized in a resulting actuator voltage Ust 'converted to the primary side (U0 = mains voltage, U1 = input voltage). Without further filter elements, the harmonics in the mains current are essentially only due to the short-circuit inductance LT between the high and low voltage side (OS and US) of the transformer certainly. The network impedance Z0 is small against LT. In order to weaken them, the filter cross branch, consisting of filter capacitor (filter capacitance) CF *, filter resistor (damping resistor) RF *, is connected upstream of the transformer. With a low line impedance ZO, a filter effect can only be achieved if a filter choke (filter inductance) LF * is also connected in the series branch. Since it is traversed by the full input current I1 (mains current), only an inductance LF * can be realized with reasonable effort, which is significantly smaller than LT. The filter has a weakening effect only for frequencies that are sufficiently above the filter natural frequency determined by LF * and CF *. This results in a minimum size for CF *. The filter resistor RF * is necessary to limit the tendency of the filter to resonate. The following aspects are disadvantageous in this known filter concept:

• All filter elements are on the primary side of the transformer and must therefore be designed and designed for high voltage. This is particularly complex for the filter choke through which the main flow flows.
• The small realizable filter inductance LF * results in a correspondingly large filter capacitance CF * in order to achieve the desired natural frequency. It causes correspondingly large losses in the RF * damping resistor simply because of the fundamental oscillation charging current.
• The filter lowers the input impedance of the vehicle and can even increase the interference current if there are harmonics in the mains voltage.

The invention has for its object to provide a transformer for an electrically driven vehicle with interference current filter, with which the effort for interference current filtering is reduced.

This object is alternatively achieved in connection with the features of the preamble according to the invention by the features specified in the characterizing part of claims 1 and 2.

The advantages that can be achieved with the invention are, in particular, that the large inductance implemented in the transformer is used for interference current filtering. The filter capacity required to achieve the desired natural frequency can be selected to be correspondingly smaller. This reduces the losses. The components of the interference current filter no longer have to be designed for high voltage. Overall, there are considerable advantages due to the reduction in space requirements, the weight reduction and the cost reduction.

Further advantages result from the description.

Advantageous embodiments of the invention are characterized in the subclaims.

Fig. 1

ein Ersatzschaltbild für einen Transformator mit Filter an einer eigenen Filterwicklung,

Fig. 2a, b,c

Filterschaltungen zur Figur 1,

Fig. 3

ein Wicklungsschema mit besonderer Filterwicklung (

Zweiwickler"),

Fig. 4

die Benutzung einer Lage der Oberspannungswicklung für den Filteranschluß (Sparschaltung),

Fig. 5

ein Schema eines Transformators mit Filteranschlüssen in Sparschaltung (

Zweiwickler"),

Fig. 6

einen Filteranschluß über Saugdrosseln an einen Transformator (

Vierwickler") in Sparschaltung,

Fig. 7a, b, c

eine Integration von Saugdrossel und Filterdrossel,

Fig. 8a, b

ein Einfachfilter für einen Transformator mit Filterwicklungssparschaltung,

Fig. 9

ein Ersatzschaltbild für einen Transformator mit separatem Störstromfilter (= Stand der Technik),

Fig. 10

eine Alternative zur Anordnung nach Fig. 7a ohne Saugdrossel.

The invention is explained below with reference to the embodiments shown in the drawing. Show it:

Fig. 1

an equivalent circuit diagram for a transformer with filter on its own filter winding,

2a, b, c

Filter circuits for FIG. 1,

Fig. 3

a winding scheme with a special filter winding (

Two-winder "),

Fig. 4

the use of one layer of high-voltage winding for the filter connection (economy circuit),

Fig. 5

a diagram of a transformer with filter connections in economy circuit (

Two-winder "),

Fig. 6

a filter connection via suction throttles to a transformer (

Four-winder ") in economy mode,

7a, b, c

an integration of suction throttle and filter throttle,

8a, b

a single filter for a transformer with filter winding saving circuit,

Fig. 9

an equivalent circuit diagram for a transformer with a separate interference current filter (= state of the art),

Fig. 10

an alternative to the arrangement of FIG. 7a without a suction throttle.

1 shows an equivalent circuit diagram for a transformer with a filter on a special filter winding. Due to a special interference current filter winding FiW between primary and secondary windings, the large transformer-implemented inductance can be used for filtering. The voltage on this particular filter winding can be selected (preferably ≤ 1000 V) so that the filter no longer has to be designed for high voltage. In the T-shaped equivalent circuit diagram of the transformer, the transformer short-circuit inductance LT of FIG. 9 is now replaced by the inductors L1 + L2. The proportion L1 should be in the range from 30% to 70% of LT. Then L1 is a multiple of the previously achievable additional filter inductance LF * according to FIG. 9. The filter capacitance can be dimensioned correspondingly smaller and, in addition, a lower natural filter frequency and thus a further attenuation of the interference currents can be achieved. The input impedance of the overall circuit is reduced less by this filter.

The third inductance Lfi assigned to the filter branch in the transformer equivalent circuit diagram should be as small as possible (Fi = filter winding connection). The equivalent circuit diagram according to FIG. 1 then has the same structure as that according to FIG. 9. Depending on the coupling conditions present in the transformer, the inductance Lfi can even be weakly negative.

Possible configurations of the filter are shown in FIGS. 2a to 2c. The equivalent circuit diagram refers to the primary side, in reality all filter elements used are to be thought of as the square of the gear ratio between the filter winding and the high-voltage winding.

, mit dem die Harmonischen in der OS-bezogenen Stellerspannung Ust' in Stromharmonische des Eingangsstromes I1 umgesetzt werden. Ohne Filter verläuft es als $\text{TR(f)=1/(2π·f·LT)}$

, also mit 1/f (f= Frequenz).The filter effect is described by the transmission behavior $\text{TR (f) = I1 (f) / USt '(f)}$

, with which the harmonics in the OS-related actuator voltage Ust 'are converted into current harmonics of the input current I1. Without a filter, it runs as $\text{TR (f) = 1 / (2πf LT)}$

with 1 / f (f = frequency).

Fig. 2a shows the simple CF-RF filter, with filter capacitor CF and filter resistor RF. If the inductance Lfi is almost zero, the filter causes a drop TR (f) with 1 / f ² above its natural frequency. At the natural frequency into which ZO << L1 the parallel connection of the inductors L1, L2 and the filter capacitor CF are included, TR is increased by the filter, and the more, the less the filter is damped by the filter resistor RF.

a)

bei einer Transformatorkonstruktion mit negativer Induktivität Lfi diese Induktivität zu kompensieren und so auf die mit Fig. 9 gleichwertige Struktur zu kommen (also $\text{LF+LFi=0}$

),

b)

dem Filter Saugkreisverhalten zu verleihen und damit bei der durch LF+LFi mit CF gegebenen Frequenz bereits eine besonders große Abschwächung zu erzielen. Diese Frequenz kann in den Bereich gelegt werden, in dem die Harmonischen besonders groß sind oder besonders stören. Erkauft wird dies damit, daß oberhalb dieser Frequenz die Abschwächung zwar auf einem niedrigeren Niveau als ohne Filter, aber nur noch mit TR(f)∼1/f geht.

FIG. 2b shows a further embodiment of the filter with a filter choke LF, but in comparison with LF * according to FIG. 9 in the shunt arm and thus advantageously designed for only a very low current load. The filter choke LF can be used to

a)

in the case of a transformer construction with a negative inductance Lfi, to compensate for this inductance and thus to arrive at the structure equivalent to FIG. 9 (ie $\text{LF + LFi = 0}$

),

b)

to give the filter suction circuit behavior and thus to achieve a particularly large attenuation at the frequency given by LF + LFi with CF. This frequency can be placed in the range in which the harmonics are particularly large or particularly disturbing. This is bought by the fact that above this frequency the attenuation is at a lower level than without a filter, but only with TR (f) ∼1 / f.

A combination of the suction circuit effect with a stronger attenuation to higher frequencies is achieved by equipping the filter with a parallel resistance RP to LF according to FIG. 2c.

The desired effect of the filter winding and the filter on the network side can be completely derived from the equivalent circuit diagram in FIGS. 1 and 2a to 2c. Instead of the individual actuator voltages of the n four-quadrant actuators operating with offset timing on the same transformer, only the mean value of the n voltages is to be used as the resulting actuator voltage USt '. If necessary, asymmetries due to slightly different evaluations of the individual voltages must also be taken into account when averaging. The number n of four-quadrant actuators and associated transformer windings can usually be 2, 3, 4 or 6. However, the equivalent circuit diagram does not show the circuits of the n individual four-quadrant actuators and the influence of the filter on them.

. Es ist nun offensichtlich, daß bei Parallelschaltung der Filterwicklung alle n im Ersatzschaltbild den Vierquadrantenstellern zugewandten Induktivitäten n·L2 in dem Filterknoten verbunden sind. Die n Vierquadrantensteller werden gleichmäßig versetzt getaktet, so daß sich ihre niedrigen Taktfrequenz-Harmonischen (unterhalb der n-fachen Frequenz eines Vierquadrantenstellers) zum Netz hin weitestgehend auslöschen. Jedoch in den einzelnen Vierquadrantenstellern selbst und den ihnen zugeordneten Transformatorenwicklungen bilden sich am ausgeprägtesten die niederen Stromharmonischen aus. Die sie begrenzende Induktivität ist in diesem Fall nur noch n·L2 zwischen Vierquadrantensteller und Filterknoten, während sie ohne den Filterknoten n·LT ist. Das heißt, diese dominierenden Stromharmonischen werden durch den Filterknoten etwa doppelt so groß.The desired good decoupling of the n windings for the individual four-quadrant actuators makes it easier to understand, instead of thinking n individual transformers for the n four-quadrant actuators, each of which has its own filter winding. The n filter windings can now be connected in parallel or in series and connected to the common filter. If the inductance of the overall transformer is LT and is divided into L1 and L2, then the n individual transformers have accordingly $\text{nLT = nL1 + nL2}$

. It is now evident that when the filter winding is connected in parallel, all n inductances n.L2 facing the four-quadrant actuators in the equivalent circuit diagram are connected in the filter node. The n four-quadrant controllers are clocked with an even offset, so that their low clock frequency harmonics (below n times the frequency of a four-quadrant controller) largely cancel each other out towards the network. However, the lower current harmonics are most pronounced in the individual four-quadrant actuators themselves and the transformer windings assigned to them. The inductance that limits it in this case is only n · L2 between the four-quadrant controller and the filter node, while it is n · LT without the filter node. This means that these dominant current harmonics are about twice as large through the filter node.

This disadvantage is avoided by connecting the filter windings in series. Then the filter only affects the harmonics, which do not cancel each other out anyway, but appear on the network. The full inductance n · LT is effective for the extinguishing harmonics as without a filter. The filter thus hardly leads to an increase in the effective harmonic current in the four-quadrant actuators and transformer windings.

Zweiwickler"). Mit US1, US2 sind die Unterspannungswicklungen bezeichnet. Der eine der Filterwicklungsanschlüsse Fi liegt z.B. auf Erdpotential.3 shows, using the example n = 2, the circuit and winding arrangement of such a transformer with the filter winding FiW1, FiW2 (

US1, US2 denote the undervoltage windings. One of the filter winding connections Fi is, for example, at ground potential.

Zweiwickler", F1, F2 = Filterabgriffe an Oberspannungswicklung = Filterwicklungsanschlüsse).The filter winding takes up space in the winding window and thus enlarges the transformer if necessary. In the event that the OS winding is designed as a layer winding, instead of an additional filter winding, the first layer of the OS winding opposite to the US winding and to be connected to earth potential can also be used as a filter winding. 4 shows this use of a position of the high-voltage winding for the filter connection (economy circuit, Fi = filter tap on high-voltage winding = filter winding connection). 5 shows a diagram of a transformer with filter connections in an economy circuit (

Two winders ", F1, F2 = filter taps on high voltage winding = filter winding connections).

Vierwickler") in Sparschaltung (F1, F2, F3, F4 = Filterabgriffe an Oberspannungswicklung = Filterwicklungsanschlüsse).With this economy circuit of the filter windings, as outlined for n = 2 in FIG. 5, the possibility of series connection is initially denied. However, it can be replaced by connecting the filter taps F1, F2 .... via flow divider chokes (= suction chokes) SD, because this largely forces the currents to be the same as in series connection. 6 shows a filter connection via suction throttles to a transformer (

Four-winding ") in economy mode (F1, F2, F3, F4 = filter taps on high-voltage winding = filter winding connections).

In a system with n = 4 windings and four-quadrant actuators, however, as shown in FIG. 6, three suction throttles SD1, SD2, SD3 are required. This alternative is therefore most advantageous when n = 2. 7a, 7b show some configurations in this case.

Fig. 7a stands for all filter modifications, as shown in Fig. 2a, 2b, 2c.

In Fig. 7b the functions of the filter throttle LF and the suction throttle SD are combined to form a throttle LF ''.

In Fig. 7c this approach is generalized for n> 2 (F1, F2, F3, F4 ... Fn = filter taps on high-voltage winding = filter winding connections).

FIG. 10 shows an alternative to the arrangement according to FIG. 7a without a suction throttle. Starting from a circuit according to FIGS. 5 and 7a, the suction throttle SD is omitted and each filter tap F1, F2 of the high-voltage winding is connected to its own filter (filter modifications see FIGS. 2a to 2c). Each of the two filters affects all harmonics of the assigned actuator. In comparison to the circuits according to FIGS. 5 and 7a, higher losses occur in the filter resistors.

For applications that get by with a small filter, e.g. Because attenuation is mainly necessary in the higher frequency range, the suction throttle and filter throttle can be dispensed with entirely. According to FIG. 8a, the filter becomes very simple when the filter resistor is split into two parts each with 2 · RF and at the same time takes on the task of dividing the current. It is accepted that the differential voltage of the taps F1 and F2 due to the offset timing is present across the series circuit 4 · RF and generates additional losses. Since the filter resistance RF can be comparatively large for a small filter, this is justifiable.

This idea can also be transferred well to systems with n> 2, as shown in FIG. 8b. The filter resistor is divided into n parts, each with n · RF.

Claims (14)

Transformer for an electrically powered vehicle, characterized by at least one interference current filter winding (FiW) integrated in the transformer, which uses one or more layers of the high-voltage winding which are adjacent to the undervoltage winding, whereby an autotransformer circuit is formed with respect to the interference current filter winding, with the filter winding connections (Fi, F1 .... Fn) at least one filter is connected, which consists of the series connection of at least one filter resistor (RF) and a filter capacitor (TF). Transformer for an electrically powered vehicle, characterized by an interference current filter winding (FiW) integrated in the transformer, which is arranged separately between the high-voltage and low-voltage winding, a filter being connected to the filter winding connections (Fi) and consisting of at least one filter resistor (RF) connected in series. and a filter capacitor (TF). Transformer according to Claim 2, characterized in that the interference current filter winding is divided into a plurality of individual windings connected in series, each undervoltage winding being assigned its own individual winding (FiW1, FiW2) (Fig. 3). Transformer according to Claim 1, characterized in that two filter taps (F1, F2) formed by the autotransformer circuit are connected to one another via a suction throttle (SD), the connection for the filter being formed by the center tap of the suction throttle (Fig. 7a). Transformer according to Claim 1, characterized in that in the case of four filter taps (F1, F2, F3, F4) formed by the autotransformer circuit, two filter taps (F1 and F2, F3 and F4) are connected to one another via a suction throttle (SD1, SD2) and in that the center taps of these two suction throttles are connected to a third suction throttle (SD3), the center tap of which forms the connection for the filter (FIG. 6). Transformer according to Claim 1, characterized in that with n (n = 2,3,4, ...) filter taps (F1, F2, F3, F4 .... Fn) formed by the autotransformer circuit, the n filter taps in each case via a choke (D1 .... Dn) with a common node are connected, the connection for the filter being formed by the common connection point of all the chokes (FIG. 7c). Transformer according to Claim 1, characterized in that two filter taps (F1, F2) formed by the autotransformer circuit are connected to one another via two identical partial resistors (2RF), the connection for the filter being formed by the common connection point of the two partial resistors (Fig. 8a) . Transformer according to Claim 1, characterized in that, in the case of n (n = 3,4, ..) filter taps (F1, F2, F3, F4 ... Fn) formed by the autotransformer circuit, the n filter taps in each case via n equal partial resistances (nRF) are connected to a common node, the connection for the filter being formed by the common connection point of all partial resistors (FIG. 8b). Transformer according to claim 7 or 8, characterized in that the partial resistors (2RF, nRF) simultaneously fulfill the function of the filter resistor (RF). Transformer according to Claim 1, characterized in that at least two filter taps (F1, F2, F3, F4 ... Fn) formed by the autotransformer circuit are connected directly to one another in order to form the connection for the filter. Transformer according to one of Claims 1 to 10, characterized in that the filter additionally has a filter choke (LF) connected in series (Fig. 2b). Transformer according to claim 11, characterized in that a parallel resistor (RP) is arranged parallel to the filter choke (LF) (Fig. 2c). Transformer according to one of Claims 1 to 12, characterized in that different filters or filters dimensioned for different frequencies are connected in parallel. Transformer according to Claim 4, 5 and 6, characterized in that the at least one suction throttle or throttle (SD, SD1, SD2, SD3, D1 ... Dn) also fulfills the function of the filter throttle (LF) (Fig. 7a).

Images