CH638348A5 - Audio-frequency ripple-control system having an invertor as the audio-frequency ripple-control transmitter - Google Patents

Description

The invention relates to an audio frequency ripple control system with an inverter as an audio frequency ripple control transmitter, the output phase voltages of which can be fed into a supply network via a series inductor, a filter circuit and a current transformer, as well as with a telecontrol unit for generating audio frequency pulses and clock pulses, whereby a start-up control with a modulator for pulse width modulation of the audio frequency pulses is connected between the telecontrol unit and the control unit of the inverter, the modulation inputs of which are acted upon by synchronized control pulses with a decreasing pulse width.

Such an audio frequency ripple control transmitter based on the pulse converter principle, which is known from German Offenlegungsschrift 24 56 344, is designed with regard to the safe commutation of a maximum permissible current. If the maximum commutation capability is reached, the audio frequency ripple control transmitter must be switched off. An overcurrent trip circuit is usually used to monitor for overcurrent and to switch off. For this, reference is made to the Siemens magazine 50th vol., Issue 3,1976, pages 144 to 147, in particular section “pulse inverters as ripple control transmitters”, where such a trigger circuit is explained - however not in detail. An overcurrent trip circuit protects against a dangerously high short-circuit current by switching off. However, it usually also responds to a transient overcurrent, which can be caused by a transient process at the output of the inverter; For example, fluctuations in the load can be felt in the form of brief overcurrents. Switching off the audio frequency ripple control transmitter can result in errors in the transmission of an information telegram to the receiving end, which leads to wrong actions on the part of the consumer. For this reason, it should only be switched off in extreme emergencies.

From the magazine "Elektrizitätswirtschaft", vol. 70 (1971), number 9, pages 237 to 241, in particular page 238, left column, 1st paragraph, it is already known to produce an audio frequency ripple control transmitter which is connected via a coupling unit with parallel and the series resonant circuit is connected to a supply network in order to protect against overload in that the AC output voltage is reduced very quickly in the event of danger by gating. The circuit for gate control is to be regarded as a device for current limitation. It protects the audio frequency ripple control transmitter when the parallel resonant circuit of the coupling unit is charged for the first time at the start of each pulse of the information telegram to be transmitted and against any type of short circuits and earth faults behind the series resonant circuit. The known device for current limitation accordingly accordingly ensures that, in the event of an overcurrent of any cause, a transition is made to the gate control. As with the known overcurrent trip circuit, this ensures with certainty that the commutation limit of the inverter is not reached or even exceeded. But even here, if there is only a short-term fault (transient overcurrent), there may be a fault in the transmission mode. The transmitted information can also be garbled in this case, i.e. Provide misinformation, arrive at the receiving end and lead to consumer misconduct. Errors in the information telegram should be avoided if possible.

The present invention is based on the object of equipping the audio frequency ripple control system mentioned at the outset with a device for current limitation which, when a transient overcurrent occurs at the output of the inverter, still provides perfect information transmission

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guaranteed, thus avoiding the usual shutdown. or that a feedback from the network side affects the sound frequency. This object is achieved according to the invention by influencing quenz ripple control transmitters. The current limitation of the starting control, in addition a device for current intervention, is therefore only assigned above the adjustable limit mentioned, which is released when a transient minimum value for the AC output voltage occurs. Overcurrent at the output of the inverter due to a current 5 If the output limiting intervention signal drops the output phase voltages AC voltage during the current limiting intervention, it is ensured that it does not fall below the minimum value of this inverter within a short intervention time of. If at this minimum value the resulting 180 ° rectangular current at the output of the inverter is still too large, the audio frequency ripple control transmitter is switched off, and the modulated rectangular shape is converted into the pulse-width used in the final phase of the startup and the subsequent 10 further developments of the invention are characterized in the dependent during a transition period, the pulse-width-modulated legal claims.

corner shape in the same way as when starting up in the 180 ° right angle. With the audio frequency ripple control corner shape (ie the publishers of pulse width modulation it is guaranteed that no mutilated information pulses control pulses a decreasing pulse width can be emitted from the transmission side Either it is specified so that the voltage amplitude gradually reaches 15 again due to the current limiting intervention, that the over-into is converted to the rectangular amplitude) and that the set-up current is reduced and the information transmission error for current limiting contains a limiting circuit is freely guaranteed , or the audio frequency ripple control system which switches off the current limiting intervention signal only after an unsuccessful attempt by the additionally adjustable minimum value of the output phase voltages, the existing overcurrent trigger circuit,

releases and which falls below this minimum value, which means that information is not transmitted. Shutdowns based on current limiting intervention that triggers the output phase surge overcurrent are limited to the minimum value. avoided.

In particular, the minimum value that can be used to maintain the shark. As a particular advantage of the invention, it is considered that the information transmission is just at least that a large part of the output AC voltage that was previously only required during start-up is provided. 25 components are now also used in normal operation,

When operating the audio frequency round according to the invention, there is therefore a double use.

Control system can be reached when a current peak value is set (on an adjusting device). An exemplary embodiment of the invention is described below, which is described in more detail below with reference to 5 figures. As the audio frequency commutation limit, with the current limiting ripple control system, the exemplary embodiment of an audio frequency voltage explained in DE-OS 24 45 344 in the handle signal in the form of the audio frequency output change 30 is intervened. If - as in the case of the ripple control system in DE-OS 24 56 344 in the example of DE-OS 24 56 344 - those components of the known ripple control system shown in normal operation as control signals are given a predetermined reference voltage, this becomes closer and closer described, which, due to the arrangement of a current limiting intervention signal, the additional device according to the invention for the current, in particular a synchronous digital signal, can experience a change during limitation. The remaining components can continue to be used unchanged by reducing the engagement time by a certain amount. Show it :

puts. The reset takes place during the mentioned Fig. 1 the basic structure of the known Tonfre-

Intervention time in the direction of modulated operation instead. The time-ripple ripple control system with start-up control, with a slight increase in the reference signal when resetting, additional device according to the invention for current limits, preferably parallel to the sawtooth comparison, is shown.

2, a block diagram of the changed start-up control hen. The intervention time can be predefined. 3, a more detailed circuit diagram of a device for using the modulation method as when starting, current limiting according to FIG. 2, which, in conjunction with that also with a correspondingly reduced one, works with the connection to a device for current limiting, frequency ripple control transmitter known frequency ripple control system works, AC gear voltage. 4 a modified gate circuit shown in detail,

on start-up time the start-up control during the so-called which is used within the start-up control, and th transition time automatically from the modulated to the unmodified operation; in doing so, it tries the full starting system according to FIGS. 1 to 4.

1 shows an audio frequency ripple control system in which if this is not permitted by a renewed current peak, the audio frequency ripple control transmitter provides an inverter 1 with a new current limiting intervention. With the targeted hen is. This inverter 1 is a current limiting intervention for pulse width modulation, e.g. to the set up in the embodiment. It comprises a power section 1 a and a reference voltage used in DE-OS 24 45 344, so it becomes control unit lb. The inverter 1 is fed on the input side by reducing the mean value of the output AC voltage 55 of a DC voltage, which causes a rectifier device 2 to switch off the inverter completely, which forms another three-phase supply voltage UN. An intermediate would be prevented if an overcurrent trip circuit required rectifier device 2 and inverter 1. circuit capacitor 3. The inverter 1, the rectifier

In the audio frequency ripple control device 2 according to the invention and the intermediate circuit capacitor 3, however, the limiting circuit also provides a converter with a constant intermediate circuit voltage. It is also ensured that the inverter 1 still forms three tone outputs with a sufficient audio frequency level even with a transient overcurrent Supply network phase voltages with a rectangular time profile. That arrives. When a current limiting intervention audio frequency is preferably in the range between 150 Hz, the modulated range is not too far and 500 Hz. The three output phase voltages are transferred; in the exemplary embodiment of DE-OS 2456344, 65 a transformer 4 is not reset too far via three series inductors 5R, 5S. In the case of a 5T, via a filter circuit 7 and via three current transformers 6R, 6S, resetting too far would run the risk that no 6T feeds a sufficient audio frequency level into the supply network into phases N, R, S, T. The current transformers 6R, 6S, 6T are

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special coupling transformers. The filter circuit 7 is modified as a few components. The device for three-phase filters from capacitors CI to C6 and from inductor current limit 100 then works with components of the anyway LI to L3 built up in the start-up control 8 shown in the drawing.

obviously are switched. The further description of FIGS. 2 to 4 is based on the fact that it has signal curves for the tone-frequency output phase voltages in FIG. 5. In order to make it clear that when recorded, it has a high AC resistance, so that the occurrence of an overcurrent practically only the final phase of an audio frequency power is carried out by the inverter 1 with little loss via the starting process, is fed into the left part L of the current transformer 6R, 6S, 6T into the supply network N, FIG. 5 of FIG. 9 of the DT-OS 24 56 344 known approaches. The LC circuit of the capacitors C4 to C6 and the gear shown again for comparison. In the right-hand part R, inductors LI to L3 are designed so that the alternating "> shows that a matching signal curve arises, selc-resistance for the mains-frequency alternating voltage of the supply network N when a current limiting intervention is carried out, so that this LC- Circuit Fig. 2 shows a block diagram of a starting control 8 slightly modified for the current transformers 6R, 6S, 6T and DT-OS 24 56 344 slightly different from that shown in FIG. 2, so that a short change for the mains frequency AC voltage a facility

represents conclusion. 's together to limit the current 100. 2 and 5

In order not to receive an impermissibly high switch-on when the telecontrol unit 9 receives clock pulses up current at a terminal 9a, the control unit 1b of the alternating - for the duration of the audio frequency transmission pulses and at three Kiem Richter 1 - is acted upon by a start-up control 8, which Men 9R, 9S, 9T sound frequency pulses uR, us, uT for forwarding which is supplied with signals by a remote control unit 9. to the start control 8. The audio frequency pulses uR, us, The circuit part of Fig. 1 described so far is from 20 uT are known in a modulator 17 in modulated audio frequency German laid-open specification 24 56 344. 1, pulses uR *, us *, uT * are implemented, which can be seen at three terminals 8r, 8s, 8t that the known circuit part occurs due to further construction of the control unit 1b of the inverter 1. An initial element is added. It is a device generator unit, consisting of a stage 10 for generating current limitation 100, which is associated with the start-up control 8 - an output signal with triple audio frequency, from a net. This device for current limitation 100 is an integrating integrating unit 11 and a reversing device that, when an overcurrent occurs at the output of amplifier 12, two terminals 1 aa and 12 a are generated by two opposite-phase inverters 1 a through a symmetrical signal from the output terminal Triangular voltages Udi and Ud2 of dreifa-100a given to the start-up control 8 current limiting rather audio frequency, which are synchronized with the audio frequency pulses uR, us, uT intervention signal w, the output phase voltage of this alternating. A second generator unit consisting of rectifier la within a short intervention time te from the 180 ° rectangular shape used in 30 from a syn-normal transmission mode emitting a release signal at terminal 13a into the chronization stage 13 and from a further integration stage 14, in the final phase of the start-up pulse width modulated generates a reference voltage Uref at a terminal 14a, which converts to a rectangular shape. That initially decreases linearly in time at the output terminal 100a when starting. The current limiting intervention level 13 supplied by the device 100 is acted upon by the clock pulses up and the signal w sets the duration of a current limit output signal of the level 10. Two comparison handles firmly. The device 100 is also set up in such a way that fen 15 and 16 compare the two triangular voltages in each case - that they then connect the gen Udi and \ Ji2 with the reference voltage Uref during a transition time tf and form pulse-width-modulated rectangular shape - in the same manner and from them pulses Ii and I2 at two terminals 15a and 16a. The way as when starting - back into the 180 ° rectangular shape - pulses Ii and I2 are guided into a gate circuit 18, where leads to. 40 two further terminals 18a and 18b control pulses Ii * and I2 *

With the designation “overcurrent”, an output occurs that controls the modulator 17. Modulator 17 and gate alternating current IR, Is, Ir are meant, the amount of which is above a circuit 18 is also from the terminal 13a with the maximum permissible current I *. To determine whether a target signal is applied.

Rather, there is “overcurrent”, which are with current transformers for the purpose of connecting the additional device 100

101, 102, 103 measured alternating output currents IR, Is, It are fed to a total of three devices 100 compared to the known start-up control 8 and have been carried out there by means of a modification (in FIG. 3) the maximum current I * additionally compared to the tap 14a. This can be connected to an on device 100, and thirdly, the gate actuator 105, which is shown as a potentiometer, is set. circuit 18 from the output terminal 100a with the device for current limiting 100 is still acted upon 50 current limiting intervention signal w. The interior direction that it has a limit structure (shown in more detail in FIG. 3) of the gate circuit 18 has also changed, cf. control circuit. This gives the current limiting input Fig. 4.

Handle signal w only above an adjustable minimum value. Details of the unit 100 are shown in FIG. 3.

U * min of the output phase voltage free; Afterwards, the alternating output currents IR, Is, IT of the current are fed to a limit value signaling unit 104 during the time of falling below this minimum value U * mi "during which a current limiting intervention compares the output phase voltage with the predetermined maximum current I *. The three the predetermined minimum value U * min. A further setting element 111 is provided for specifying this minimum resultant output signal, an OR gate minimum value U * min. 106 supplied, which is used for the summary and as half This is also shown as a potentiometer. A measure for diode bridge is shown. This OR gate 106 is the amount of the output phase voltage which is followed by a time or delay element 107 from the tap 60, the reference voltage Uref which is taken from FIG. 14a and is used in the start-up definition of the engagement time te. The timing element 107 as control 8 is formed. If the output phase voltage is therefore a flip-flop circuit 108 which is also connected to the inverter 1 a below the set minimum value of the output signal of the tes U * min stage present at terminal 10 a, the device for current limitation 100 is not acted upon . This flip-flop circuit 108 serves to engage more. there is a synchronization with the edges of the just mentioned

The device for current limiting 100 can - as shown - produce an output signal. In the device 100, the reference signal tapped at the terminal 14a is also carried as an additional device for the start control 8. The known start-up control 8 only has to supply Uref to a further limit value detector 110. Here will

5

compare it with the specified minimum value U * min. The output signal of the limit value detector 110 is fed together with the output signal of the flip-flop circuit 108 to a NAND gate 112, from whose output terminal 100a the current limiting intervention signal w can already be tapped 5. The signal w provides a current limiting intervention when an overcurrent spike occurs; it also suppresses such a current limiting intervention if the output phase voltage falls below the minimum voltage U *. 10th

Fig. 4 shows the basic structure of the gate circuit 18. This gate circuit 18 has been changed in two points compared to the gate circuit 18 in Fig. 7 of DE-OS 24 56 433: NAND elements 38A and 38B have been added. The current limiting intervention signal w is here fed from the terminal 15 100a to the one input of the NAND stage 38B. The other input is connected to terminal 13a and is thus acted upon by the release signal. The output signal of the NAND stage 38B is applied to the terminal 39a and at the same time also supplied to the one input of the NAND stage 38A and the one input of the flip-flop 39. The NAND stage 38B ensures that the aforementioned change in the signal shape and thus a current reduction takes place not only when starting (pending signal u), but also in the event of overcurrent (pending signal w). 25th

The other input of NAND stage 38A is connected to the output of NAND stage 38. Its output is connected to the other input of flip-flop 39. In conjunction with the flip-flop 39, the NAND stage 38A ensures that modulation pulses which are smaller than a minimum time set on the monostable 30 time stage 32 are suppressed. The flip-flop 39 is reset with the output signal of the NAND stage 38B.

4, the pulses II and 12 are fed to two NAND elements 34 and 33, which are followed by a common NAND element 35, which acts on a monostable multivibrator 32 with an adjustable minimum time. The minimum time determines a minimum permissible pulse width. Each NAND gate 34, 33 is connected to a terminal 18a or 18b via an inverter 37 or 36. The outputs of both NAND gates 33, 34 are also connected to a NAND gate 38, which is followed by a flip-flop 39. The output of flip-flop 32 acts on the third input of NAND gate 38.

If a pulse II or 12 corresponding to the modulation pulses falls below the minimum duration tmin set on the monostable multivibrator 32, an output signal is output from its output terminal 38a to the NAND gate 38A. This results in a signal change at the downstream flip-flop 39, and the modulation pulses Ii *, I2 * are so with the help of the two NAND elements 34 and 33

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Output signal at the terminal 39b of the flip-flop 39 blocked. In the event of a current limiting intervention via the signal w at the terminal 100a, the flip-flop 39 is reset again via the output signal of the NAND stage 38B, and the modulation pulses 11 * and 12 * are released again. At the same time, the reference voltage Uref is reset from the output 39a during the time period te, as a result of which the pulses II and 12 subsequently exceed the minimum duration train again. The release at flip-flop 39 acts until the set minimum duration tmin is again undershot and the flip-flop 39 is set via the signal from terminal 38a and the modulation pulses are thus blocked via the signal at terminal 39b.

The mode of operation of the pulse control results in detail from the diagrams in FIG. 5. The designation of the individual diagrams corresponds to that in DE-OS 24 56 344, with the difference that the signal at terminal 39a, on the one hand, controls the voltage Uref Generating generator 14 is used and on the other hand, in the event of an overcurrent intervention, the pulse lock on the flip-flop 39 is reset. The modulation pulses are blocked when the minimum time train is reached by the signal at terminal 39b.

Only the right-hand part R is considered in the following, from which a current limiting intervention can be seen.

The signal at terminal 39a indicates with its falling edge f that there is an overcurrent and that a reset intervention should begin. During the intervention time te, the reference voltage Uref is raised linearly. It is important that the reference voltage Uref starts up relatively quickly. The increase must not be flatter than an increase in one of the sawtooth voltages Udi, Ud2, so that the minimum time tmin for the pulses Ii *, I2 * is not undercut. In other words: the rising edge of the reference voltage Uref must not cut out part of the lower part of a sawtooth tip. The reference voltage Uvef may only run up to a predeterminable value, this value corresponding to the minimum value U * min set on the setting element 111.

After the intervention time te, the output phase voltage is converted into the pulse-width-modulated rectangular shape. From this point on, the reference voltage Uref drops linearly with a relatively slow time course until it has reached the value zero. In the transition time tf until the minimum time tmin is undershot, the pulse-width-modulated rectangular shape is returned to the 180 ° rectangular shape used in normal operation. This return takes place in the same way as in the starting process; therefore the corresponding transition time tf is also shown in the left part L. From the last four diagrams it is clear that the pulse patterns of the audio frequency pulses uR *, Us *, uT * and uRS * in the right part R are identical to those shown for the start-up in the left part L.

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4 sheets of drawings

Claims (8)

638 348 PATENT CLAIMS 1.Audio frequency ripple control system with an inverter as an audio frequency ripple control transmitter, the output phase voltages of which can be fed into a supply network via a series inductor, a filter circuit and a current transformer, as well as with a telecontrol unit for generating audio frequency pulses and clock pulses, with between the telecontrol unit and the control unit of the inverter is connected to a start-up control with a modulator for pulse-width modulation of the audio frequency pulses, the io modulation inputs of which are assigned synchronized control pulses with decreasing pulse width, characterized in that the start-up control (8) is additionally assigned a device (100) for current limitation, which when a transient overcurrent occurs at the output of the inverter (la), the output phase voltages of this inverter (la) are within a short intervention time (te) from that in the norm by a current limiting intervention signal (w) len operation used 180 ° rectangular shape in the pulse width-modulated rectangular shape 20 used in the final phase of the start-up and then during a transition period (tf) the pulse-width-modulated rectangular shape - in the same way as when starting up - returns to the 180 ° rectangular shape, and that Device (100) for current limiting contains a limiting circuit (104 to 112) which only releases the current limiting intervention signal (w) above an adjustable minimum value (U * min) of the output phase voltages and which drops below this minimum value (U * min) limits the output phase voltages to the minimum value (U * min) during the current limiting intervention. 30th 2. audio frequency ripple control system according to claim 1, characterized in that the minimum value (U * m; n) is the output AC voltage which is just still required to maintain the information transmission. 35 3. audio frequency ripple control system according to claim 1 or 2, characterized in that the device (100) for current limitation contains a limit indicator (104) which is acted upon by current transformers (101, 102, 103) which are located in the output lines of the inverter (1 a), wherein the 40 limit indicator (104) is provided with an adjusting element (105) for setting the maximum permissible current (I *), and that the limit indicator (104) is followed by an OR gate (106). 4. audio frequency ripple control system according to claim 3, 45 characterized in that the OR gate (106) is followed by a timing element (107) for determining the engagement time (te). 5. audio frequency ripple control system according to claim 4, characterized in that the timing element (107) is followed by a flip-50 flop circuit (108) for edge synchronization at the beginning of the engagement time (te). 6. audio frequency ripple control system according to one of claims 1 to 5 with a reference signal for determining the output phase voltage, characterized in that a 55 further limit indicator (110) is provided, which is acted upon by the reference signal (Uref) and with an adjusting member (111) is provided for setting the minimum value (U * m; n). 7. audio frequency ripple control system according to claim 5 and 6, characterized in that the outputs of the flip-flop 60 circuit (108) and the further limit indicator (110) are connected to a NAND stage (112) which is used to prevent the current limiting intervention in the event that the minimum value (U * min) is undershot, is provided. 8. audio frequency ripple control system according to claim 7, 65 characterized in that the NAND stage (112) is a logic element downstream of a NAND stage (38B).