DE2601263A1 - POWER CONVERTER - Google Patents

Description

P AT ε N TA N WÄ LT U.

SHIP v. FUN ER STREHL SCHÜBEL-HOPF EfBBiTJGJHAUS

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DA-11973

DE / bi

15th January 1976

Priority: IG. January $ 197, Japan, Kr, 6326/75

The invention relates to an Lc; i6tiingöv; andlc-r-Anoi'-dnung for converting alternating voltage into direct voltage, with several Rectifier circuits, each controlled rectifier contain.

Service modifier arrangements of this kind are particularly important as electrical Fshrzcugcpuisungen i) in the following particular reference is made and in which V / achselspanmmgsleistungs in DC power to the drive of a DC motor converted by means of a power converter system, the controlled rectifier, for example contains thyristors that control the non-contact allow the main circuit.

Here, the power switch arrangement usually contains

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a rectifier circuit which contains a bridge circuit made up of thyristors or of thyristors and diodes. With this arrangement, the phase control of the thyristors in the input fi-alternating current creates harmonic components in relation to the L power converter arrangement. Ede Harnonischen vrorden over the Retrfoitung to. Electrically transmitted vehicle, whereby inductive disturbances arise in news transmission lines and the like, which are arranged in the vicinity of the power line.

To reduce dec? EiiifluDses the harmonics became a Power converter arrangement proposed that instead of one single rectifier bridge contains several, for example three to four rectifier bridges, whose DC currents are connected to each other in grater.

In the proposed arrangement, a specific one controls Rectifier bridge sequentially and cyclically your output DC voltage, and the remaining rectifier bridges control their output DC voltages in on ~ off operation.

Bai the power converter arrangement formed from several rectifier bridges however, there is a problem that the output direct current flowing through a direct current motor overshoots because when the particular rectifier bridge for sequential control of the output voltage reaches the extreme value, the equalizing voltage is commutated on the rectifier bridges, which can be controlled in on-off mode. The reason for this is as follows:

In general, a power converter arrangement is connected to the network via a transformer. The transformer is therefore provided with a secondary winding which is divided into several groups of coils, which in turn are connected to the AC terminals of the respective rectifier bridges of the power converter arrangement. On the other hand, it is to avoid the overshoot

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Current is necessary when switching the output voltage, the voltage regulation of the respective rectifier bridges leads to the input ^: s-AC voltage to be completely equalized before and after the voltage configuration. The relative coordination reactances of the individual coils in the transformer secondary winding must be completely equal if the relative communication reactance is defined according to the following equation:

Commutation reactance χ Ncnnstroin

rel. Commutation reactance = - * ■■ - »———« ——

Open circuit voltage on the secondary coil

However, it is practical to manufacture an ideal transformer in which the relative commutation reactances of the Secondary coils are completely the same, im possible because the relative commutation reactance is inevitable from manufacturing errors in terms of the number of turns of the coils and the magnetic coupling between the coils and the core of the transformer is dependent. As a result, the relative coordination reactances of the secondary coils become irregular, so that when the relative commutation reactance of the secondary winding of the rectifier bridge to the sequential Control that the rectifier bridge controlled in on-off mode exceeds, an overshooting current or power surge is generated.

The overshooting current generated in this way results in the following components:

1. There is a surge of current flowing through the DC motor that generates the. Can destroy engine;

2. the elements forming the power converter arrangement, such as thyristors, diodes and the like, can be thermal be destroyed;

3. the proportion of harmonic components in the input alternating current to the power converter arrangement increases, which entails the difficulty of inductive interference;

4. the torque of the DC motor increases rapidly,

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causing the wheels of the electric vehicle to spin; and 5. the driving comfort is adversely affected.

The invention is based on the object of specifying a power converter arrangement in which the then resulting overshooting current or current surge is avoided if a voltage commutation between a rectifier bridge for sequential and cyclical control of their Equalizing DC voltage and a rectifier bridge to control your output DC voltage in on-off operation takes place, whereby a steady and smooth voltage control should be guaranteed.

The power converter according to the invention contains a transformer with a transformer with an alternating voltage source connected primary winding and a secondary winding divided into several groups of coils, and several rectifier bridges with controlled rectifiers, the AC voltage terminals of which are connected to the Individual groups of secondary coils are connected and their DC voltage terminals are connected in series with one another where a particular rectifier bridge controls its output DC voltage sequentially and cyclically and the remaining rectifier bridges have their output DC voltages control in on-off operation, the voltage control range of the particular rectifier bridge for sequential control is selected so that the voltage control ranges of the remaining rectifier bridges be overlapped with on-off control.

The invention is explained in more detail using the exemplary embodiments shown in the drawing. Show it:

1 shows the schematic circuit diagram of the main circuit a power converter to which the invention is applicable;

FIG. 2 shows different voltage curves for explaining the mode of operation of the power converter shown in FIG. 1 ;

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Fig. 3 is a current-voltage Kerm line of the power converter of Fig. 1;

4 shows the schematic winding arrangement of an inventive Transformer;

5 shows a current-voltage Kerm line of a power converter with the transformer of FIG. 4;

Fig. 6 the see mat is before representation of the winding arrangement a modified transformer according to the invention;

7 shows a current-voltage characteristic curve of a power converter ride the transformer of Fig. 6;

8 shows the schematic circuit diagram of a further exemplary embodiment of the performance modifier according to the invention; and

9 shows the schematic circuit diagram of a third exemplary embodiment of the service modifier.

According to FIG. 1, the primary winding 11 is a transformer 1 via terminals u1 and v1 to an alternating voltage source, not shown connected. The secondary winding of the transformer 1 is divided into three coils 12, 13 and 14, whose The winding and thus the voltage ratio is 1: 1: 2. Of the a total of 2 designated power converters (or rectifier arrangement) contains three rectifier bridges 21, 22 and 23. The individual rectifiers 21, 22 and 23 contain One bridge circuit each made up of thyristors and diodes (Fig. 1). The AC voltage terminals of the bridge circuits are connected to terminals u12 - v12, u13 - v13 or ui4 v14 connected to the associated secondary coil 12, 13 or 14. The DC voltage outputs of the rectifier bridges 21, 22 and 23 are connected in series with each other; a DC motor 3 is as a load between the rectifier bridges 21 and 23 are connected. The firing of the thyristors of the individual rectifier bridges is controllable by means of a phase control device (not shown).

The rectifier bridges can also be used exclusively

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Thyristors can also be built in three Coils 12, 13 and 14 with unequal tension ratio (1: 1: 2) split 3 secondary winding in four coils with equal tension ratio of 1: 1: 1: 1 divided v / earth «

In operation, the output DC voltage of the rectifier bridge 21 is controlled sooucntiell and cyclically (Fig. 2 (c)), while the output DC voltages of the rectifier bridges 22 and 23 are only switched on and off (Fig. 2 (b) and 2 (a)).

If the rectifier bridge 21 for sequential control and the activated and deactivated rectifier bridges 22 and 23 is operated as shown in Fig. 2 (d) on Output of the power converter 2 is a sum output DC voltage Ed that changes sequentially through the stages or steps (1), (2), (3) and (4) and the DC motor 3 is supplied.

Step 1):

The rectifier bridges 22 and 23 are turned off and only the rectifier bridge 21 is sequentially controlled. Correspondingly, the output DC voltage Ed of the converter or rectifier 2 is equal to the output DC voltage the rectifier bridge 21.

Step 2):

The rectifier bridge 22 is switched on, the rectifier bridge 23 switched off, and the rectifier bridge 21 is controlled sequentially or continuously. Accordingly, the DC output voltage Ed of the converter 2 becomes the same the sum of the output DC voltages of bridges 21 and 22.

Step 3):

The rectifier bridge 22 is switched off, the rectifier bridge 23 is turned on, and the rectifier bridge 21 is sequentially controlled. The

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DC output voltage Ed of the power converter 2 is the same the sum of the output DC voltages of bridges 21 and 23.

Step (4):

The rectifier bridges 22 and 23 are switched on, and the rectifier bridge 21 is controlled sequentially, see above that the output DC voltage Ed of the power converter 2 equals the sum of the output DC voltages of bridges 21, 22 and 23.

As shown in Fig. 3, switching from one arises Step to the other a rush current when the relative commutation reactance of the coil is sequentially controlled Rectifier bridge 21 is greater than the relative commutation reactance of the due to a manufacturing error remaining, switched on and off secondary coils of the rectifier bridges 22 and 23.

Referring to Fig. 3, during the step (1), the DC output voltage is sequentially controlled between the point O and the point P along a straight line 11 at a predetermined accelerating current by sequentially controlling the rectifier bridge 21. Immediately after the output voltage of the rectifier bridge 21 reaches a maximum value at the point P, it falls to 0 and the rectifier bridge 22 is switched on. The control step (2) follows. However, since the secondary coil 13 of the rectifier bridge 22 has a smaller relative commutation than the secondary coil 12 of the rectifier bridge 21, the current-voltage characteristic follows immediately after the switching from the step (1) to step (2) of a straight line I ^ · The operating point jumps consequently suddenly from point P to point-Q, creating a current surge.

A similar surge can occur if the

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next steps in the next following step unpeeled v, ^r ird (Fig. 3).

IXU ¹ Cb, the invention is the formation dos StröiTästor-ses ^bo:; n Switching over without the control steps being prevented.

FIG. 4 shows an arrangement according to the invention of the windings of the transformer 1 in FIG. 1. The primary winding 11 of the transformer 1 in FIG. 1 is divided into several groups of coils 111 to 114 (FIG. 4). The transformer 1 is also provided with secondary coils 12, 13 and 14 for the rectifier bridges 21, 22 and 23 in a manner similar to that in FIG. 1. The primary coils 111 and 112 are connected in series; the secondary coil 12 is between them. The magnetic primary-secondary coupling between the primary coils 111 and 112 on the one hand and the secondary coil 12 is therefore better than is the case between the primary coil 113 and the secondary coil 13 or the primary coil 114 and the secondary coil 14. Therefore, even if the transformer 1 has irregular manufacturing defects, the relative commutation reactance of the secondary coil 12 of the rectifier bridge is smaller than that of the secondary coils 13 and 14 of the rectifier bridges 22 and 23, respectively.

FIG. 5 shows, similarly to FIG. 3, a current-voltage characteristic curve the power converter arrangement of FIG. 1, in which the windings of the transformer 1 are arranged according to FIG. 4 are. In the transformer of FIG. 4, the controllable voltage range therefore exceeds and overlaps the rectifier bridge 21 that of the rectifier bridges 22 and 23 which can be switched on and off during the control step (1 to 4). Accordingly, when the DC motor is accelerated from the point O, the acceleration occurs within step (1) and reaches point P.

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The output voltage of the rectifier bridge then drops 21 to O, and the cloakroom bridge 22 is switched on, so that this makes its starting point; produced «to this Time becomes the working point from point P to point 0 along the dashed line Ip shifted. However, since the rectifier bridge 21 middle] s of a not shown ntro ^ tax- · device is phase-controlled, the operating point is shifted immediately from point 0 to point P.

In this way, by placing the secondary winding 12 for the GleichricliterbrUcke 21 with a lower relative Komi.nutierungsreakbanz than that of the secondary windings 13 and Vi for the remaining rectifier bridges 22 and 23 is equipped, prevents when switching between the individual control steps a »current surge is generated. Through this the disadvantages of the known performance; transducer arrangements avoided. The reduction in the relative commutation reactance to the extent that the manufacturing error is largely compensated, leads to a satisfactory mode of operation.

As for the desirable reduction in the proportion of harmonics in the input alternating current as a result of the phase control As concerns the relative commutation reactance of the winding of the coil 12 for the Rectifier bridge 21 to increase. This is because the current rate of change di / dt after ignition of the thyristors, which is a major cause of the generation of harmonic components, is thereby minimized can that the relative commutation reactance is chosen as high as possible.

In this regard, reference is made to Figure 6, which a modified arrangement of the transformer windings shows as a further embodiment of the invention. In this embodiment, the primary winding 11 is the Transformer 1 of Fig. 1 in coils 111 to 115 under-

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shares while, as well as in Pig. 1, the secondary winding is divided into coils 12 to 14, which- from the power converter 2 and the DC motor 3 are loaded. The windings Doß Tranri / ormators 1 are arranged so that the secondary spu'l.e 12 ci ^ c? greater relative koiranutation reaction than the remaining- *: has secondary winding on 13 and 14. However, since a pure increase in the relative commutation reactance the overlap of the controllable voltage range Prevents the respective generation steps of the output voltage, the Sekurjdärspule 12 is placed so that it is with a higher voltage is fed. Reference is made to FIG. 7 in this regard.

Fig. 7 shows the Stroa-voltage characteristic that can be achieved in a power supply arrangement, the transformer of which has the windings of FIG 12 a voltage E _{Q1 is} supplied for sequential control, which is greater than one of the secondary coil 13, which is only switched on and off Electricity surge is generated. Furthermore, the secondary coil 12 for sequential control can have a high relative commutation reactance in order to reduce the harmonics due to the phase control of the thyristors.

In the exemplary embodiments described above (FIGS. 4, 6), an attempt was made to prevent the current surge when switching between the individual control steps by means of the winding arrangement of the transformer 1. Alternatively, as shown in FIG. 8, chokes 41, 42 and 43 can be connected between the secondary coils 12, 13 and 14 and the AC voltage terminals of the rectifier bridges 21 ₅ 22 and 23. The throttle 41 is for the

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Rectifier bridge 21 for sequential or continuous Control designed so that their reactance is smaller than the reactances of the throttles 42 or 43 for the Rectifier bridges 22 and 23, which are only switched on and off will.

Fig. 9 shows a further embodiment in which ' the transformer 1, similar to that in Fig. 1, secondary coils 15 »16 and 17, the stress ratio of which is the same Is 1: 1: 2. The secondary coil 15 for a rectifier bridge 24, with which it is sequentially controlled, is with provided with an intermediate tap. The remaining rectifier bridges 25 and 26, which are only switched on and off, are designed in the same way as the equalizer bridges 22 and 23 of FIG. 1. The rectifier bridge 24 for sequential control includes a bridge as shown in FIG with two thyristor branches and one diode branch. the Viechselspanrmngs -ingangεklemmeη the thyristor branches are connected to an outer terminal or the intermediate terminal of the secondary coil 15, while the AC voltage terminal of the diode branch is connected to the other external terminal of the secondary coil 15.

In operation, the rectifier bridge 24 is used for sequential control initially as a first mixed rectifier bridge, a thyristor branch being connected to the intermediate tap of the secondary coil 15 and the diode branch in order to control its output voltage sequentially. When the output voltage reaches a maximum value, the rectifier bridge 24 serves as a second mixed bridge rectifier, the other thyristor branch being connected to the one outer terminal of the secondary coil 15 and the diode branch in order to control the entire voltage on the secondary coil 15 sequentially. Then, when the output voltage of the second mixed bridge rectifier reaches a maximum value, the rectifier bridge 25

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switched on, so that an output voltage arises at this and the output voltage of the rectifier bridge drops to zero. In the sequential control of the DC motor 3 voltage to be supplied becomes a similar mode of operation repeated.

With the rectifier bridge shown in Fig. 9 for sequential.! When controlled, the number of branches of the elements forming the rectifier bridge becomes compared to two Groups of rectifier bridges used are reduced, thereby lowering costs.

The I] r; ^r indur) £ can also be applied to the performance variable arrangement 3 'of Fig. 9 in a manner similar to that in the previous exemplary embodiments.

With the invention, therefore, current surges are generated when changing over ten between the control steps in the generation of the DC output voltage and a smooth voltage control guaranteed. The elements forming the converter and the DC motor forming the load therefore become of excessive currents due to the rush current spared. In particular, when the invention is used in electrical AC drives, additional In addition to the advantages outlined above, wheel slip as a result of sudden changes in torque is avoided, whereby the comfort when driving is increased.

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Claims (2)

Power converter for converting AC voltage into DC voltage, with a transformer whose primary winding is divided into an AC voltage source and whose secondary winding is divided into several coil groups, and with a rectifier with several rectifier bridges, each containing controlled rectifier elements and having AC and DC voltage sources, the AC voltage terminals each Rectifier bridge each connected to a group of secondary coils and the DC voltage terminals of the rectifier bridges are connected in series with one another to generate an output DC voltage of the rectifier, the output DC voltage of a certain rectifier bridge sequentially and cyclically in several stages of the generation of the output DC voltage from the rectifier controllable and the remaining rectifier bridges are controllable in such a way that their output DC voltages are switched on and off during these control steps, w although in änn steps the remaining rectifier bridges are switched on and off when the output DC voltage of the specific rectifier bridges reaches a maximum value in each cycle, characterized in that the value of the output DC voltage of the rectifier (2) when the output DC voltage of the specific rectifier bridge (21, 24) reaches the final value, higher than the value of the output DC voltage of the rectifier is selected at the beginning of the next step. 2. Power converter according to claim 1, characterized in that that the secondary coil (15) of the transformer for the particular rectifier bridge (21) 609830/0276 stronger magnetic coupling than the secondary coils (16, 17) of the transformer (1) for the remaining rectifier bridges (22, 23) to carry out the choice on v / eist. Power converter according to claim 1, dadtirch g ο k e, nz e ichnet that the secondary coil (i5) of the Γ * / π-formatora (1) for the specific rectifier bridge.: 1) alL has a less strong magnetic coupling the secondary coils. (12, 13) for the remaining rectifier bridges (22, 23), and that the particular rectifier bridge (21) has a higher voltage range than the rest of the rectifier bridges to carry out the election. Power converter according to Claim 1, characterized in that that between the secondary coils (K :, 13, 14) and the rectifier bridges (21, 22, 23) Pr '■ -be (41, 42, 43) are switched, and that the Dros.s. (41) for the particular rectifier bridge (21) one Has less reactance than the rest of the Drosne -i for the remaining rectifier bridges, so that the W il perform. Power converter according to Claim 1, characterized in that that each rectifier bridge (21, 22, 23, 24, 25, 26) is a bridge circuit made of thyristor ' or thyristors and diodes on v / eist and the output ..- DC voltage of the rectifier (2) is fed to a direct current motor (3). 609830/0276 Blank page