DE2622043A1 - PROCESS FOR IMPROVING THE NETWORK RETURN EFFECTS IN SERIES OF SELF-COMMUNICATED AND LINE-COMMUNICATED RENTER BRIDGES - Google Patents

Description

Licentia Patent-Verwaltungs-GmbH Frankfurt / Main, Theodor-Stern-Kai 1

Hamilton / se B I 76/29 Ham

Process to improve the network perturbations in series-connected self-commutating and line-commutating converter bridges

The invention relates to a method for controlling a rectifier formed from several converter bridges, at least one of whose converter bridges is self-guided.

It is known that the system perturbations are improved with the help of erasable and thus self-commutated converters can be (see German Offenlegungsschrift 21 26 or 21 34 598). The network perturbations are twofold To optimize in terms of:

1. the reactive current should be minimized, i.e. the apparent current

adjusted to the active current, which is the case if the power factor A and the fundamental oscillation shift _{factor cos ψ 1 are increased} to the value 1 if possible

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will. Especially lagging, i.e. inductive reactive current is to be avoided. As is known, this reduces the voltage at the converter input, which is required for the same Active power increases the grid current.

2. The network harmonics of the current should be minimized because they do not provide any real power, on the other hand Put additional strain on the network and the environment. These harmonics, also known as interference currents, are particularly evident in Bahn-r systems are critical because signals and telephone systems can be influenced or disturbed.

The invention is based on the object of improving the network perturbations taking into account both aspects to undertake. In addition, the task should be carried out with the least possible effort in terms of weight, volume and cost of the converter bridges and their wiring can be solved.

This task is given for a method of the above Type solved in that first the DC voltage specification is carried out with the or a self-commutated converter bridge, which is operated section- or sector-controlled, and then when the other is commissioned, with gate control operated converter bridges through the self-commutated converter bridge through the gate control conditionally lagging fundamental oscillation current compensated in this way

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becomes that the fundamental oscillation shift factor at the value or remains capacitive. This improves the network perturbations at the origin of reactive current and harmonics (Fighting causes) and especially achieved with arrangements of several converters connected in series.

In order to implement such a method with the least amount of effort, an arrangement is proposed which is characterized in that the erasable converter bridge has one or more extinguishing branches consisting of extinguishing capacitor (s) and
-thyristor (s) exist and which ensure the closed time of the valve branches to be deleted, and also has one or more storage capacitors that are in the to be deleted
Intermediate storage of magnetic energy present in electric circuits, which is passed on to the consumer on the DC voltage side at a suitable phase point in time.

The self-commutated, ie erasable converter bridge is preferably an asymmetrically half-controlled (branch-pair-controlled) with two extinguishing branches and one exclusively
Storage capacitor coupled via diodes is provided, which is discharged completely or partially at the same time as the ignition of both controllable bridge arms onto the load, eg a motor. On the one hand, this inherently guarantees
that the storage capacitor with the next erasure the

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can absorb the energy to be converted without overcharging voltage. On the other hand, the is dated during the deletion process Mains fed energy minimal, so that this limiting or storage capacitor can be kept small.

This coincident ignition for the purpose of discharging the memory on the one hand and switching on the positive DC voltage half-wave on the other hand runs very simply in the way from that the controllable branch with a negative half-wave goes out again by itself when the discharge current on zero has decayed because the normal negative reverse voltage is then present.

In a further development of the inventive concept, the ignition of both branches takes place with the usual ignition delay angle oC up to a value oC = 0, which is identical to the transition from sector control to section control the extent to which the capacitor discharge current decays. This has a favorable effect on reducing the interference current, which is evaluated in particular psophometrically.

The start of erasable converters, especially when feeding a DC or mixed current motor from the rest position

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can be problematic if, in order to avoid lagging current, start-up control is not used if possible shall be. When starting with section control, the DC voltage jump value is so high that it becomes too high Current surge in the motor results, which makes a soft start impossible. Therefore, in further development of the procedure According to the invention, initially only the extinguishing branches of the self-commutated bridge operated with phase control and after reaching the maximum achievable mean DC voltage, the controllable main branches in the above-described Way ignited shortly before the ignition of the extinguishing branches, whereupon their ignition delay angle gradually is adjusted towards zero. At the same time or later, the ignition delay of the extinguishing branches should mirror-image so far can be increased so that there is a minimum line current value at a certain section angle.

The further increase in the output DC voltage U, through the addition of the converter bridge that can only be controlled can take place differently, depending on whether the reactive or interference current should have the attainable minimum value in this DC voltage or power range. What in particular As far as the psophometrically weighted interference current is concerned, this is mainly dependent on the commutation current steepnesses, which have an effect on the network side. These are at con-

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conventional gate control large, which can excite parasitic vibrations. However, if one neglects the requirement for an optimal voltage curve with regard to the interference current and only strives for a voltage curve that is favorable with regard to the reactive current and that can be easily implemented, then the following method is advantageous after a further development of the inventive concept: If, for example, two follow-up bridges are used, one of which is self-guided, the DC voltage component emitted by the erasable bridge is kept constant with a section angle of 30 - 90 °, so that the upper 50 % of the total voltage can be set by adjusting the converter bridge, which can only be cut.

A voltage curve that is favorable overall with regard to interference and reactive current is obtained if each of them is controllable Converter bridge suddenly opened or almost fully opened. is switched on and the self-guided bridge is initially down by an equally abrupt increase in the section angle and then gradually increased again by decreasing the section angle. The transition can take place abruptly also gradually overlapped.

The defaults for ignitions and deletions can be set after a fixed setting of the control units for the converter.

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bridge or take place in a controlled manner so that the possible minimum of the mains current is achieved with the required active power or maximum of the power factor λ.

The method according to the invention can also be used with an asymmetrically half-controlled converter bridge with only Realize a quenching and two limiting (storage) capacitors, in which in the free-wheeling main branches, the normally non-controllable valves, i.e. diodes, contain also controllable valves, in order to reverse the direction of energy enabled by inverter operation.

The method according to the invention can also be used if symmetrical (single-pole) semi- or fully controllable converter bridges self-operated and mains-operated.

The method according to the invention will be explained in examples below with reference to the drawing. Show it

Figure 1 is a basic circuit diagram with two subsequent converter bridges,

Figure 2 to 5 in the diagram the course of the voltages on the two bridges over the total DC voltage,

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FIG. 6a shows the time profile of the total DC voltage output when the erasable converter bridge is only switched on and

FIG. 6b shows the time course of the total DC voltage output, when both converter bridges work.

In Figure 1 is a self-commutated, so erasable converter bridge marked with I. The bridge is asymmetrically half-controlled and with two extinguishing branches (extinguishing thyristors LT 1, LT 2, quenching capacitors CL 1, CL 2) and one coupled exclusively via non-controlled valves KD 1, KD 2 Storage capacitor C 3 provided. With D 1, D 2 the diodes of the uncontrolled valve pair branch and with HT 1, HT 2 denotes the controlled valve pairs of the converter bridge I. The charging diodes LD 1, LD 2 are used for charging the quenching capacitors CL 1, CL 2 via a charging resistor RL, BD 1 and BD 2 are block diodes. Such a converter bridge is described in German patent application P 22 09 293.

In series with the erasable, for the inventive method

or

drive sector-I section-controlled converter bridge I is connected to a converter bridge II that can only be controlled by the gate. The bridges are over

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Al

Feed windings SP 1, SP 2 are fed from an alternating current network and work on a motor M.

In FIGS. 2 to 5, the bridge DC voltages U, are plotted against the total DC voltage U, which is applied to the motor M. With U. ^ in a dashed curve, the direct voltage of the erasable sector or section-controlled converter bridge I and with U ₃₁ - denotes the direct voltage of the section-controlled converter bridge II.

In Figure 2, a voltage curve is shown, according to which first the converter bridge I takes over the direct current output (increase in U j) and then the upper 50 % of the total DC voltage U are set by adjusting the angle of the converter bridge II, while the output from the erasable bridge DC voltage component Uj is kept constant with a section angle of 30 - 90 °. As already mentioned above, this course of the voltage distribution on the converter bridges is only favorable with regard to the reactive current, but not with regard to the psophometrically assessed interference current.

A curve as shown in FIG. 3 is more favorable, for which the gate-controlled converter ^{bridge II g} _{709849/0069 after the 50% limit of the total DC voltage U d has been reached}

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is suddenly almost fully opened, so that the voltage Uj Jj rises abruptly. In the same way, the erasable Converter bridge I controlled down by a sudden increase in the section angle, so that the voltage U j drops. The converter bridge II then becomes full opened up, whereupon the voltage gradually increases by reducing the section angle at the converter bridge I. U, to the maximum value of the total DC voltage U, is increased.

FIG. 4 shows a curve for the bridge voltages U, _ and U, j, which is even more favorable with regard to the criteria of reactive and interference current. Here, too, the gate-controlled converter bridge II is opened suddenly, but this is already happening _; before the converter bridge I is initially fully controlled, ie at U, <50 %.

FIG. 5 shows that the voltage setting transition can also be carried out instead of suddenly overlapping in order to reduce the reactive and interference currents to minimum values. By gradually turning down the converter bridge I and at the same time gradually turning up the converter bridge II, when the gate-controlled bridge II is added, the voltage U, ^ until the voltage U, ^ ₁ has risen to its maximum. Only then is the converter bridge I gradually turned on again, so that the voltage u " _d ^ rises again.

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In FIGS. 6a and 6b, the course over time of the total direct voltage U output is shown in an idealized manner, during a half-cycle of the alternating voltage being supplied. The ignition of the controllable branches and the discharge of the storage capacitor can be clearly seen at, for example, an ignition delay angle C ^ = 0. In the course of FIG. 6a, only the converter bridge I is in operation (U _d < 50%); .

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Claims (11)

Licentia Patent-Verwaltungs-GmbH Frankfurt / Main, Theodor-Stern-Kai 1 Hamilton / se BI 76/29 Ham Claims ί 1. / Method for controlling a rectifier formed from several converter bridges connected in series, at least one of whose converter bridges is self-guided,
characterized, that first the DC voltage specification takes place with the or a self-commutated converter bridge, the is operated section- or sector-controlled, and then when commissioning the others, with Gate control operated converter bridges through the self-commutated converter bridge of the the basic oscillation current caused by the gating control is compensated in such a way that the basic oscillation shift factor remains at the value 1 or capacitive. 709849/0069 - ² - ORSGSHAL INSPECTED - 2 - BI 76/29 Ham 2. Arrangement for performing the method according to claim 1, characterized, that the erasable converter bridge with one or more extinguishing branches from extinguishing capacitor (s) and Quenching thyristor (s) to ensure the closed season of the valve branches to be deleted and with one or more storage capacitor (s) for intermediate storage of the in the circuits are provided with magnetic energy. 3. Arrangement according to claim 2,
characterized, that the diodes present in the main branches of the converter bridges are replaced by controllable valves are. 4. Arrangement according to one of claims 2 or 3, characterized in that that symmetrical (single-pole) semi-controllable converter bridges are provided as self-commutated converter bridges are. 5. The method of claim 1 using a self-commutated asymmetrical single-phase bridge with two Arcing branches and a storage capacitor, 709849/0069 - 3 - BI 76/29 Ham characterized in that each time the two controllable branches are ignited Bridge the discharge of the storage capacitor coupled via diodes takes place. 6. The method according to claim 5, characterized in that the ignition of both controllable branches takes place with an ignition delay angle cC which is reduced to the value oC = 0. 7. The method according to claim 6, characterized in that initially only the extinguishing branches of the bridge with phase control are operated and then the controllable main branches are ignited shortly before the extinguishing branches and finally their ignition delay angle is reduced to zero. 8. The method according to claim 7, characterized in that that the variable-speed converter bridge (s) that can be controlled by the section are controlled by the direct voltage output the self-commutated converter bridge is kept constant with a section angle of 30 - 90 °. 709849/0069 - 4 - BI 76/29 Ham 9. The method according to claim 7,
characterized, that every gate controllable converter bridge is suddenly almost fully opened or switched on and the self-guided bridge by increasing the section angle in an equally abrupt manner, first down and then gradually increased again by decreasing the section angle. 10. The method according to claim 9,
characterized, that the transition is not made abruptly, but gradually overlaps. 11. The method according to any one of claims 1 or 5 to 10, characterized in, that the converter bridges that can be controlled at and cut off according to the minimum of the mains current and / or the maximum of the power factor can be regulated. 709849/0069