DE1902079A1 - Control device for AC-DC or DC-AC converters connected to DC power lines - Google Patents

Description

PATENT LAWYERS 1902073

DIPL.ING. H. LEINWEBER dipl-ing. H. ZIMMERMANN

MUnchen2, Ro ** ntal7, 2nd ed.

Ti addr. Lelnpat MQnchen Tifon (B811) 2 <1flt

<ι η January 16, 1969

Z / We / Wy / Ho F ° 3495 GOMPAGHIE GENERALE D »ELECTRICITE, Paris, France

Control device for AC-DC or DC-AC converters connected to DC power lines

The invention relates to a control device for generating control pulses for different cells of rectifier and inverter bridges of a direct current line having a three-phase rectifier bridge equipped with six cells at each end has, of which the one upstream of the direct current line is fed with alternating current and one in the line rectified current feeds, and the downstream of the direct current line and this direct current absorbing a consumer supplies an alternating current. This device is intended for installation in a direct current line, regardless of the Regulations of the program and possible operational disruptions a correct implementation of a given energy transport program is guaranteed with excellent efficiency and mode of operation as well as a high level of safety. With the invention A bridge can also be controlled in the same way, either as an inverter bridge or as a rectifier bridge is working.

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Fig. 1 shows a known direct current line with an alternating current source, which is shown schematically by a secondary winding 2 'of a three-phase converter 1. The three-phase converter 1 has a primary winding 3, a rectifier bridge 6 (in this case a three-phase Graetz bridge with six rectifier elements 6a to 6f), a double line with two conductors 7a and 7b for the transmission of direct current, and at the end j of the line an inverter bridge 8 with six rectifier elements 8a to 8 connected in the form of a Graetz * bridge! 8f, which feeds a primary winding 11 of a converter 10, the secondary winding 12 of which feeds a network 13. '■

In this example, the energy is conducted from the rectifier bridge 6 to the inverter bridge 8. The device However, the device can also be operated in such a way that the energy is passed in the opposite direction. The inverter bridge j 8 then acts as a rectifier and the rectifier bridge 6 j as an inverter.

In the following description, for the sake of simplicity, reference is made to the case where the rectifier bridge 6 works as a rectifier and the inverter bridge 8 works as an inverter. However, since 4 pounds? Bridge with an inventive Device is equipped, the system can also work in the opposite direction.

As is well known, one can, for example, with a semiconductor (thyristor) or with mercury vapor when operating in the same direction (Thyratron) controlled rectifier device a cell can only be ignited if its terminal voltage is positive is.

The minimum delay is used as the rectifier stop £

Ö09336 / 0325

denotes the - as described below - from the theoretical Moment of zero crossing of the terminal voltage of a cell is calculated and it enables this cell with one hundred percent Ignite Security. Reference is made to this definition in the following.

It is known that when a bridge is operated as an inverter, the command to ignite an element must be given in good time waden that the previous element is extinguished, because otherwise the switchover fails, which in turn causes the bridge to stadsj can be damaged.

For this reason, a protective bracket is provided for operation as an inverter, also known as the inverter stop, which corresponds to the minimum electrical angle that the ignition of a given element of the inverter bridge and the point in time the zero crossing of the voltage of the element separates from each other during operation.

r-ei these definitions it must be taken into account that a Three-phase network can have the following operating irregularities;

1. in original operation:

a) it came: there was a frequency migration;

^) the i.eti: can uiiao ^ e ^ lichen, i.e., the three phases stiLu.eix in amplitude and content of the harmonics no longer match;

c) piston oscillations of the voltage of one or more fnasen ui ~ ,: time of _.ulldurch _ö "angs this voltage or voltages to tr et en.

2. Lei exceptional: operation:

a) the "e :. Can 70llstä.ndi _{o be} unbalanced, what the ' "" asa "; ..: .. üi-Lruc' .: or the failure of one or more phases after j

SIC- L13..6: 1 jLäl.;. J ■;

909836/0925 ^BAD

b) there may be a sudden change in the system error angle with respect to its immediately preceding value;

c) the zero crossing of the voltage of one or more phases may disappear during a period corresponding to one or more periods;

d) the zero crossings can occur uncertainly and not at the correct times.

The invention relates to a device with which in a direct current line connected at each end with a bridge is provided from controlled rectifier cells, taking into account the mandatory requirements of the program for energy transfer, the optimal moments for igniting the cells are determined and the corresponding impulses can be delivered, with the best possible degree of efficiency (especially low energy consumption), flawless characteristics of the network and cells as well as extremely low operating deviations in the normal and abnormal range. Such a device consists of an angle calculator which is assigned to a pulse generator controlled by it is.

A first major requirement for the device is that it generates trigger pulses that are outside the It is essential to keep the same distances between the laying periods.

Another prerequisite is the generation of pulses within those time periods in which ignition is possible (Rectifier) or is safe (inverter).

These time periods must also be chosen in such a way that security is guaranteed without the for the Energy transfer applicable characteristics are unfavorable: so it is known that the degree of transferred through the line

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909836/09 25

Energy is a function that grows with the value of the inverter stop and the start of the ignition of the cells of the inverter bridges indicates. The object of the invention is to produce a device with which the ignition angle with a Tolerance range can be calculated which is sufficiently large to guarantee the ignition reliability of the cells of the inverter bridges ensure, and sufficiently small to keep energy consumption to a minimum. i

Another object of the invention is to produce a device which, regardless of the rules of the program and the possibly occurring time deviations (frequency drift, completely unbalanced state, change in the phase angle, Omission of the zero crossing of the voltage), pulses with exact time periods generated.

Another object of the invention is a device with which numerically, so with very great precision, the ignition angle of the bridge cells can be calculated.

The invention relates to a device for generating of control pulses for different cells of rectifier | and inverter bridges of a DC line connected to each! The end has a three-phase rectifier bridge equipped with six cells, one of which is connected upstream of the direct current line is fed with alternating current and feeds a rectified current into the line, and that of the direct current

and this direct current receiving line downstream ^/ supplies an alternating current to a consumer, and which is characterized in that at each end of the line a detector for the passage of the gauze of the terminal voltage of one of the cells of the bridge located at this end is provided, as well as devices for measuring the Period of this voltage, devices for sending out

-6-9Ό9836 / 0926 bad original

Pulses that are separated from one another by a time interval corresponding to the sixth part of this period, determine the theoretical zero crossing moments of the terminal voltage of the various bridge cells and of which the first pulse coincides with the zero crossing, devices for measuring the actual zero crossing moments of the terminal voltages of the bridge cells, devices for measuring the gröffec M time interval between each actual zero crossing of the terminal voltage of a cell and the corresponding theoretical Bull passage means starting to calculate the periods between the theoretical lulldurchgang the terminal voltage of each cell and its moment of ignition of the value of the largest interval of the bridge control angle, the Peionisierungswinkels or - the erasure time of the cells and the bridge clearance angle, devices for generating pulses to control the ignition of the cells at the calculated times, as well as devices services for redirecting the impulses in sighting to the corresponding cell.

Further advantages, details and features of the invention emerge from the following description. On the Drawing the invention is shown by way of example, namely show

Fig. 1 schematically shows a direct current line, Fig. 2 schematically that attached to one end of the line device according to the invention for generating pulses,

3a to 3c and 4a to 4e representations of the mode of operation the zero crossing detector and the calculator for the theoretical zero crossings, and 5 shows an illustration of the ignition area for the bridges

in rectified or inverter operation.

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The shown in Fig. 2 schematically in its unit
Device is located at one end of the direct current line; the other end is provided with an identical device.

The apparatus comprises a voltage zero crossing detector connected to the terminals of one of the cells of the; Bridge is connected (21, Fig. 2). The detector speaks to the! Zero crossing with increasing value and includes a blocking; device that the detector immediately after the first Hull; the passage of the voltage is blocked, so in the case of approximate-; th zero crossings (oscillations) only the first zero crossing _;

is being considered. \

In the schematic representations of FIGS. 5a to 5c: the mode of operation of this detector is shown. Fig. 5a; shows the changes in the terminal voltage of the cell as a function of-! from the time. This tension can be near definite; Zero crossings oscillations 51 and 52 have, the detector
are at the voltage imlldurchgang a pulse 55, and at the same time a blocking signal sen det 54 adjustable ^duration: from that during the entire tlockierungszeit each pulse ^t: emission prevented. In this way, the ^{"parasitic zero crossings" based on oscillations 1} can be switched off, since the anomalous zero crossings of the voltage in the course of the \

Period occur and only the first IV passage of a short one! Sequence of vibrations is scanned. j

The .'ill passage of the terminal voltage as a reference: Cello chosen, bright, which darch tapped the task 21: is. arucht? i at the output of the device 21 as a pulse i 55 from and "-units the calculation of the five theoretical Hull

909836/0925 BATH ORIGINAL

crossings of the voltages at the terminals of the five other cells of the bridge, and on the basis of this calculation the value T is measured and the value Φ- calculated. This is effected by a counter 23 which counts the number of periods of an auxiliary oscillator 22, the frequency of which depends on the accuracy required by the counter. The counter 23 is set to the zero value by each zero crossing detector pulse of the terminal voltage of the reference cell supplied by the device 21 and

Meanwhile, Ψ counts a period of voltage. 4a and 4b show the changes in the terminal voltage ■ of the reference cell as a function of time and the changes χ in the content of the counter 23 as a function of time. The calculation of the theoretical zero crossings is carried out by an element 7. This receives the zero-crossing pulses as one of the input variables, which through their chronological sequence determine the period T of the terminal voltage of the reference cell. The value of the last period measured by the counter before it was reset to zero is called the instantaneous period. The calculator calculates the sixth part of the instantaneous period, which corresponds to the theoretical time interval between the zero crossings of the terminal voltage of the remaining five cells of the bridge.

If - based on a device 2

established zero crossing - after a time has elapsed

T is six times as long as the calculated value 7 · the content

of the counter 23 has not changed, the network is in the balanced state. If this is not the case, the instantaneous frequency has changed changed * and the counter shows a larger or smaller | ner number.

The theoretical zero crossings are used for the determination

909836/0925 BAD original

the theoretical instantaneous values of the zero crossing from organ 7

miy τ is calculated with a counter, the contents of which are compared to the value ^ - will. This counter is determined by the reference zero crossing and each time coincidence determined by the comparator returned to the zero value.

In a first time span, the voltage has a constant period T ₁ . The counter of the organ 7 is fed and emptied in a period -r-, the resets to the zero value in the diagram 4c by the points I ₁ , Ip, .. I ₁ ; IV, IV .. IV are shown. When the voltage period changes to a value Tp which is higher than 1 ', the values provided by the calculator are sent to the counter of organ 7, which for one period still has the period -A (J ₁ , Jo ·· * J ^) ^ d- then works in the following period with the new period 7- · (JV ... JV) (Fig. 4c).

If the period of the terminal voltage of the reference cell changes to a value T i, which is less than IV, the counter of the organ 7 operates during the first period T, with the value 7- = · and is at the end of the voltage period of the reference cell by the organ 21 reset to zero. This iiückstellen to the zero value, however, blocks are delivered to the five pulses of the theoretical zero crossings _e This can be done by means of an additional counter which is contained at 7 also in Or ^ and counts the pulses of the theoretical zero crossings; then sawtooth waves with a period of - ^ - are delivered, namely KV, KV ...

In a modified embodiment, the counter ν de £ Organ / after the fifth pulse of the calculated zero crossing

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be automatically returned to the zero value if there is no actual zero crossing or if it is excessively delayed, with an adjustable value r ~ which clearly exceeds the normal value r. Devices are actuated in case of errors (lack of a reference zero-crossing, missing calculation of r, ^etc.): This allows the Schutz--. If there is no zero crossing, the calculation of the zero crossings is carried out

»With the exception of the first round, the one in the predetermined ο Τ

Value -7- takes place with the last calculated value of -r 6 '6

performed.

Figures 4d and 4e show a graph of a voltage with sudden fading. The period, on the other hand, is constant and equal to the value Tp-, and the status of the counter of the organ 7 set to the value ■ £ ■ is higher than the value

6 ~ Tp-

On the saw teeth whose distance τ ~ - , M _1. “. I ^V L; IL

Ng, after the loss T of the voltage, saw teeth P ₁ ... P ^ follow, namely after an interval JM?. ,, during which

ID T ₀ D 1

\ the counter has reached its maximum level -r- if there is no actual zero crossing of the voltage. The restoration of the voltage is determined by the zero crossing S, and the theoretical calculations of the zero crossings take place again as before.

The device according to the invention (FIG. 2) also comprises a detector 6 for determining the zero crossing of the voltage at the terminals of each bridge cell. This detector has the same structure as the device 21.

Using these measurements, the “stop £ the Grleichrichterbrüc'ke calculates waves «The rectifier

909836/0925

Richter stop is supposed to prevent the firing sequence from reaching the cells before their terminal voltage has become positive again. For this purpose there is a computation element 8 which, on the one hand, records the theoretical zero crossings supplied by the counter of the organ 7 and, on the other hand, the actual gauze crossings determined by the device 6, for each cell! the interval £ between the theoretical and the actual! Zero crossing. This gives, in general, five numbers that do not have the value zero, the interval of the reference cell is always defined as zero, except when the actual reference zero-crossing is missing and Dahei the interval of the difference between the adjustable value - and in the computation of the theoretical zero-crossings used value corresponds to τρ; which gives a sixth number. These five or six numbers are compared with the help of a logical organ 9 and the number with the highest absolute value is then stored and used as described below.

For the operation of the bridge as an inverter, the stop or protective bracket writes the limit value of the ignition torque a given cell, so that the previous cell has time to extinguish before the zero crossing of its terminal voltage, which it would otherwise ignite again.

The wave guide stop is therefore a function of the un-I balanced state of the network, the deionization angle of cells and travel angle. The latter two angles are defined and calculated in the following way:

The state of the unaυgeglichene i.etzes, starting ¹ IgLiIi ₀ Or on the deviation between the actual and the calculated julldurC: measured ellenkleimaen li-the voltage of the, ils

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only the absolute value of this deviation is taken into account " and no distinction is made as to whether the actual zero crossing takes place before or after the calculated zero crossing. This deviation is denoted by £ and is sachsmal per period measured. For example, the following rule can be established

th
The deviation calculated at the η zero crossing is

with f and the deviation measured at the next zero crossing denoted by C -ι + 1). -deviation). If € .. is greater than £, the old value € is replaced by the new value <f -j in the formula (given below) for determining the shaft guide stop.

If € .j is less than E i , the value £ remains in the calculation. . \

If, in the course of the following zero crossings, all values of £ are less than 6 ", this value is replaced by a lower value ί . If the periodic character of the stress, even when deformed, is taken into account, the new value of £ will necessarily be the largest value of at least six consecutive values £ _, and changes that are too frequent are avoided.

These logical processes are followed by a suitable Save provided logical organ 9 carried out, based on the sizes of the organs 21, 22, 7, 23 and Ö.

The clearance angle u, which is defined as the time interval · is in which two consecutive cells at the same time a current that does not have the value zero is passed through by a function generator 24 from the instantaneous value i of the current flowing in the bridge, from the peak value V of the voltage between the phases and the

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The transformer's lust reactance X is calculated. The analog signal output by the generator 24 is replaced by an analog signal Digital converter 25 numerically encoding the analog signal via a control chopper 26, the mode of operation of which will be explained below.

As already described, the changes during the calculation of the waveguide stop is assumed by u immediately if this increases, while changing for a few periods to be seen if the fourth of u is constantly below the previously used value. A logic organ 27 determines the value of u, the value of u is calculated continuously, namely at least a few dozen times per period. In order to avoid frequent changes of the attack, the organ is 27 designed in such a way that the value assumed by u is the most unfavorable of all those determined in the course of at least one period Values is.

The angle of extinction corresponds to a fixed value Y ", the j depends only on the type of cell used and is determined by the designer. Its value is fed into an organ 5,

and a signal in the form of an ignition delay O ^- -Y is determined which corresponds to the difference between the half cycle 4 and the angle V. This gives you regardless of the fluctuations in the period. T a constant deionization time.

This calculation is made by a numerical counter 4

T men, which calculates the half-period - ~ in each period, and to which a subtracter b is connected, which supplies a number corresponding to the value i -Ύ as the output signal.

The inverter stop is calculated by adding the

T / · C
algebraic sum?> - "/ - u - c- is determined. Its value

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is common to all six cells of the bridge, so that the ignition pulses keep the same distances.

The ignition moment of the. Cells that are in the by the two Rectifier and inverter stops specific area should be included, is controlled by a controller based on an error signal, which is proportional to the deviation the measured intensity is from the current reference value.

The cone signal is then passed through an analog Kegler 28 determined. This controller is connected to an analog digital converter which, due to the intended control! chopper 26 may be the same as that for calculation the clearance angle converter 25. The bowler is such constructed so that the cone signal changes in the same sense like the delay angle to ignite the cells. In this way, a low level cone signal corresponds to an operation mode the bridge as a rectifier while a signal corresponds to an inverter operation with a high value. The control signal remains the same for every mode of operation of the bridge Sign at, and it is possible by changing uniformly of the cone signal to switch from rectifier operation to inverter operation.

The ignition angle is determined in the following way: "

Through the reference zero crossing as well as all calculated A counter 29 is triggered, the contents of which changes proportionally with time.

In addition, an addition device adds "31" on the one hand

the count _ov > the rectifier max supplied by the organ 9

stop corresponds to, and the control signal r, which numerically through the converter 25 is encoded, and on the other hand calculates the

BATH ORIGINAL -15-909836 / 0925

'Inverter stop T _n - * / - u - L · . The ignition angle must

ά max

stay within the range determined by the rectifier ' and the inverter stop is determined. This result is obtained as follows:

The content of the counter 29 is constantly and almost simultaneously on the one hand .with the sum from a comparator Rectifier stop + signal £ ~ + r compared, and

max m £>

on the other hand with the rectifier stop - - Ύ - u - <-

^to 2 max

If the value t + r is less than the inverter stop,

Max . '■ ■

the ignition sequence of the cells results when the contents of the counter 29 and this fourth match. If r is Hull or negative, the ignition torque corresponds to the rectifier stop. If r + * ~ are greater than the inverter stop, the ignition sequence is triggered when the content of the counter 29 matches the inverter stop. The ignition commands are issued to the appropriate cells by a suitable device 32. Fig. 5 shows this type of ignition. The hatched areas

are the prohibited ignition areas. The points 0 and ίί correspond

to the

the critical point of sin when operating as an inverter or / when operating as rectifier c The straight line Z (t) gives the increase in the Contents of the counter 29 as a function of the time t again.

The device is completed by an element 39 which continuously delivers six safety pulses. The ignition moment corresponds to both the rectifier and the inverter a delay of 90, namely at the terminals of the bridge, the voltage of which is assumed to be imll. These impulses be- through the appropriately chosen lüilldurehgang generated by the supply voltage. The effect of these impulses on the control electrodes of the rectifier cells is controlled by a gate system. ^ u blocks, which also ensures that the impulses

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get to the correct rectifier cell.

The gates can be either by an appropriate value £ . open pasture, which has an abnormal discrepancy between the calculated and causes the measured zero crossings, i.e. based, for example, on a power failure or incorrect calculation, or by any other selected characteristic (short circuit in the line, detection of an ignition fault, etc.). .

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Claims (1)

Claim: Device for generating control pulses for different ^! dene cells of rectifier and inverter bridges of a j DC power line with six cells at each end ^! Equipped three-phase rectifier bridge, of which the: DC line upstream is fed with alternating current. and feeds a rectified current into the line and the line connected downstream of the direct current line and receiving this direct current supplies an alternating current to a consumer, characterized in that a detector for the zero crossing of the terminal voltage of one of the cells of the bridge located at this end is provided at each end of the line , as well as devices for measuring the period of this voltage, devices for emitting pulses which are separated from one another in this time period by a time interval corresponding to the sixth part of this period, determine the theoretical zero crossing moments of the terminal voltage of the various bridge cells and of which the first pulse with the Zero crossing coincides, devices for measuring the actual zero crossing moments of the terminal voltages of the bridge cells, devices for measuring the greatest time interval between each actual zero crossing of the terminal voltage of a cell and the corresponding theoretical zero crossing, devices for calculating the BATH 909 836/09 2 5 Periods between the theoretical zero crossing of the terminal voltage of each cell and its ignition moment based on the value of the largest interval, the bridge rule angle, the deionization angle or the extinction time of the cells and the bridge clearance angle, devices for generating pulses - for controlling the toe ignition at the calculated times, as well as fixtures; gen. to redirect the impulses in the direction of the corresponding cell. 909836/0 92 5