CH661383A5 - THYRISTOR DEVICE. - Google Patents

Description

The invention relates to a thyristor device according to the preamble of patent claim 1.

DE-A-2 552 414 discloses such a thyristor device with n thyristors Ti ... T "connected in series in each thyristor arm. For the purpose of synchronizing the firing of the thyristors, light pulses from light emitters are supplied to pulse generators for generating a gate signal for the respective thyristor.

From DE-A-2 443 279 a device for overvoltage protection of thyristors is known, in which surge arresters are provided in parallel with the thyristors, thereby protecting them. From DE-A-2 530 789 a circuit for the protection of rectifier systems for direct current lines with an arrester, a non-linear resistor and a current generator on the direct current side of the rectifier system is known, in which the arrester is discharged when the direct current output signal of the rectifier system takes the form of an overvoltage, whereby the gate signals of all thyristors of the rectifier system are blocked.

Thyristor devices are widely used in DC power transmission systems, in starters for starting synchronous motors, etc.

FIG. 1 shows a block diagram of a DC power transmission system of known type. The system shown contains, in short, a rectifier 1, an inverter 2, transformers 3 and 7 and DC power transmission lines 5. The input AC voltage of the rectifier 1 is supplied by the latter Transformer 3 supplied via AC reactances 4. The DC output voltage of the rectifier 1 is supplied to one end of each of the DC power transmission lines 5 via DC reactances 14. The other end of each of these lines 5 is connected to the DC voltage input of the inverter 2 via DC reactances 14. The rectifier 1 and the inverter 2 each consist of a three-phase bridge circuit with six thyristor arms 10. Each of the thyristor arms 10 contains a plurality of thyristors 11, which are connected to one another in series and / or in parallel.

An alternating voltage supplied to the transformer 3 is transformed into an alternating voltage of a different size and supplied to the rectifier 1 via the alternating current reactances 4. The AC voltage transformed in this way is converted into a DC voltage in the rectifier 1. This DC voltage is transmitted via the DC power transmission lines 5 and fed to the inverter 2. In this, the DC voltage is converted back into an AC voltage. This AC voltage is fed via the AC reactances 6 to the transformer 7, in which the voltage is transformed again. So a DC power transmission is carried out.

Such a system usually contains a protective device, e.g. an impulse voltage damper, an Abieiter or the like. to the described thyristors 11 before impulse voltages, e.g. To protect lightning overvoltages, switching overvoltages or the like. In particular, the system shown in FIG. 1 contains a line surge voltage damper 8 with a series connection of a capacitor and a resistor in each of the three phases between the AC voltage supply conductor to the rectifier 1 and earth. Element-shock voltage dampers 13, each with a series connection of a capacitor and a resistor, are connected in parallel to a plurality of thyristors 11, which form a thyristor arm 10. Arm arresters 12 are each connected in parallel to an assigned thyristor arm 10. The inverter 2 is likewise equipped in a similar way with line surge dampers 9, arm arresters 12 and element surge dampers 13.

The line surge voltage dampers 8 serve to suppress surge voltages that are supplied to the rectifier 1 via the transformer 3. The arm arresters 12 serve to suppress surge voltages which are applied to the relevant thyristor arms 10. The element surge voltage dampers 13 serve to suppress surge voltages which are applied to the relevant thyristors 11. The line surge dampers 9, the arm arresters

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12 and the element impulse voltage damper 13 of the inverter 2 act in the same way.

The relationships between the number of thyristors 11 in a series circuit, the repeatedly permissible blocking peak voltage of the thyristors 11 and the discharge trigger voltage of the arm arresters 12 described will now be explained. 1, the nominal voltage of the transformers is 110 kVeff and each of the thyristor arms 10 contains a series circuit of 120 thyristors with a blocking peak voltage 10 of 4 kV. If the discharge trigger voltage (upper limit) of the arm arrester 12 is 355 kV and assuming that the irregularity of the voltage distribution among the 120 series-connected thyristors is 20%, then the voltage Vs which occurs when the arm 15 In the worst case, conductor 12 is applied to one of the thyristors 11, expressed by the following equation:

vs =

355 120

X 1.2 = 3.5 (kV)

(1)

In other words, when the arm arrester 12 is discharged by an external lightning overvoltage or the like at 355 kV, a voltage of at most 3.55 kV is applied to a single thyristor 11. However, since the repeatedly permissible reverse peak voltage of the thyristors is 4 kV, as stated above, the thyristors 11 are not destroyed. The relationships described above are shown in detail in the table.

TABLE 30

maximum design voltage 480 kV

(4 kV x 120s = 400 kV x 1.2)

Dielectric strength of the

Thyristor converter 400 kV 35

(= 355 kV x 1.13)

Discharge trigger voltage

(upper limit) the arm

Arrester 355 kV

40

Peak value of the maximum repetitive voltage (switching oscillation voltage) 205 kV

(= 171 kV x 1.2) 45

Peak value of the nominal alternating voltage in the event of voltage fluctuations of the source 171 kV

(= 155 kV x 1.1)

Peak value of nominal 50

AC voltage 155 kV (110 kVeff x] / l)

Nominal AC voltage 110k

Conventional thyristor devices have already been built 55 so that the thyristors 11 can be turned on when a repetitive 4kV reverse peak voltage is applied, in a case where a gate signal is applied to the thyristors 11 to turn on while the Arm arrester 12 have been discharged by an external lightning surge or 60 or the like. Switching on all thyristors 11 requires a certain amount of time, with the result that a voltage loss occurs, which is referred to as switching loss. The higher the voltage that is present on the thyristors 11 when the thyristors 11 are switched on, the greater the switching loss. 65 Ordinary thyristors can only be switched on

if the voltage across them is less than half the repeatable blocking peak voltage. In order for the thyristors 11 to be switched on while a voltage close to 100% of the repeatedly permissible reverse peak voltage is applied to them, the thyristors must be built strong enough to withstand the switching loss. This has disadvantages in that the internal structure of the gate electrodes of the thyristors is complicated and the thyristors are large. This in turn leads to the disadvantage that the thyristor device as a whole becomes large and bulky.

The object of the invention is to design a thyristor device according to the preamble of patent claim 1 in such a way that the thyristors can have a lower resistance to switching losses and can therefore be geometrically smaller and have a simple gate structure,

The object is achieved by the features specified in the characterizing part of patent claim 1.

In the thyristor device according to the invention, each thyristor can perform its task in normal operation, controlled by the gate signal emitted by the associated gate signal generating means, e.g. perform a specific stress transformation. However, if a surge voltage deriving means is applied by a surge voltage applied to a thyristor arm, e.g. an external lightning overvoltage is discharged, then the discharge is detected by the relevant arrester discharge detection means, and the gate signal blocking means responsive to the output signal of the arrester discharge detection means deactivates the relevant gate signal generating means. In such a case, no gate signal is supplied to the thyristor arm by the gate signal generating means, so that the thyristors are not switched on. The thyristors are therefore not switched on when an abnormally high voltage is applied to the thyristor arm, so that there is no excessive switching loss. It is therefore not necessary for the thyristors to have a very high resistance to switching losses.

The thyristors and thus the entire thyristor device can thereby be relatively cheap and also of relatively small size. The smaller and simpler thyristors can generally also be obtained more easily, so that the maintenance of the thyristor device is easier.

The thyristor device according to the invention can be used for many different applications, e.g. in DC power transmission systems, in frequency converters, in starters for synchronous motors, etc.

An embodiment of the invention is explained below with reference to the drawings.

Fig. 1 shows a block diagram of a known DC power transmission system in which the invention can be used with advantage, and

2 shows a block diagram of an embodiment of the invention.

2 shows a block diagram of the thyristor arm 10 of the system of FIG. 1 with an associated gate signal generating circuit. The connection points A and B in FIG. 2 correspond to the connection points A and B in FIG. 1.

As already explained, the thyristor arm 10 contains a series connection of, for example, 120 thyristors 11. The cathode of the thyristor 11 at one end of this row is connected to the connection point A, and the anode of the thyristor 11 at the other end of the row is connected to the connection point B. . A series and / or parallel connection of a plurality of thyristors 11 is referred to as a thyristor power converter. An element surge suppressor 13, which includes a series connection of a capacitor and a resistor, is connected in parallel with each thyristor 11. Furthermore, an element bridging resistor 15 is connected in parallel to each thyristor 11. The resistors 15 reduce the uneven

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speed of the distribution of the voltages across the various thyristors 11. One end of the arm arrester 12 is connected to the connection point A, and the other end of the arm arrester 12 is connected to one end of a voltage dividing resistor 16. The other end of the voltage divider resistor 16 is connected to the connection point B. A circuit 19 for generating electrical gate signals is connected to the gate electrode and the cathode of each of the thyristors 11. Each electric gate signal generating circuit contains a light receiving element 19a. A circuit 17 for generating optical gate signals is connected to each electrical gate signal generating circuit 19 via a respective light guide 18. The optical gate signal generating circuit 17 includes a series circuit of light emitting devices 17a in a number equal to the number of the electric gate signal generating circuits 19. A gate activation signal generation circuit 25 is connected via an AND gate 24 to the input of the optical gate signal generation circuit 17.

A circuit 20 for detecting a discharge and generating an optical signal is connected to the voltage divider resistor 16 described above. This circuit 20 contains a light-emitting element 20a. The output signal of the circuit 20 is fed to the input of a receiver circuit 22 for optical signals via an optical fiber 21. The receiver circuit 22 includes a light receiving element 22a. The output signal of the receiver circuit 22 is fed to one of the inputs of the AND gate 24 via an inverter 23. The receiver circuit 22, the inverter 23 and the optical gate signal generation circuit 17 together form a low-voltage circuit arrangement 26. Similarly, the electrical gate signal generation circuit 19, the thyristors 11, the element surge dampers 13, the element bypass resistors 15, the arm Arrester 12, the voltage divider resistor 16 and the circuit 20 together form a high-voltage circuit arrangement 27.

The mode of operation of the circuits according to FIG. 2 is explained below. The operation in the normal state in which the arm arrester 12 is not discharged is first described. For example, as shown in FIG. 1, the thyristor arm 10 is arranged in a three-phase bridge circuit, so that a rectifier operation for converting an AC voltage into a DC voltage or vice versa, an inverter operation for converting a DC voltage into an AC voltage can be carried out. The gate activation signal generation circuit 25 generates a gate activation signal S1 with a predetermined phase for performing a rectifier operation or an inverter operation and supplies this signal to the AND gate 24. The gate activation signal generation circuit 25 can e.g. an ignition signal generator with a voltage controlled oscillator of the type described in U.S. Patent Nos. 2,467,765, 3,047,789 and 3,197,691 and U.S. Patent Application No. 382,015.

The AND gate 24 forms a logical product of the gate activation signal S1 and the output signal of the inverter 23 in such a way that it sends the gate activation signal S1 supplied by the gate activation signal generating circuit 25 to the optical gate signal Generation circuit 17 passes on when the output of inverter 23 is high. Depending on the gate activation signal S1, the optical gate signal generating circuit 17 simultaneously emits light from all light-emitting elements 17a, and the optical gate signals S2 are supplied to the relevant electrical gate signal generating circuits 19 via the light guides 18. Due to the simultaneous emission of light from all light-emitting elements 17a, all thyristors 11

be switched on simultaneously in the row. The purpose of using the light guides 18 is to electrically isolate the low-voltage circuit arrangement 26 described above from the high-voltage circuit arrangement 27. When the electrical gate signal generation circuits

19, the optical gate signals S2 are supplied, then the optical gate signals are converted into electrical signals by the light receiving elements 19a, and as a result, electrical gate signals S3 are applied to each of the thyristors 11 between the gate electrode and the cathode. If the electrical gate signals S3 are supplied to the thyristors 11, then these are switched on at the same time. As a result, the thyristor arm 10 operates in the rectifier operation or inverter operation described above.

The operation of the circuits according to FIG. 2 for the case where the arm arrester 12 is discharged by an external lightning surge voltage or the like will now be described. If a surge voltage is supplied to the thyristor arm 10 which is higher than the pulse discharge triggering voltage of the arm arrester 12 (355 kV as described above in the exemplary embodiment shown), then the arm arrester 12 is discharged. As a result of the discharge of the arm arrester 12, a discharge current flows through the voltage divider resistor 16, the voltage which is produced divided by the voltage divider resistor 16 to a value which is suitable for the operation of the circuit 20 for detecting a discharge and generating an optical signal. If the electrical signal is applied in the form of the divided voltage, then the circuit initiates

20, the light-emitting element 20a to emit light, and the optical signal S4 thus generated is fed via the light guide 21 to the receiver circuit 22 for optical signals. The purpose of using the light guide 21 is to electrically isolate the low voltage circuitry 26 from the high voltage circuitry 27. When the optical signal S4 is supplied, the receiver circuit 22 causes the optical signal S4 to be converted into an electrical signal by the light receiving element 22a, and this electrical signal is supplied to the inverter 23. Depending on the high value of the signal from the receiver circuit 22, the inverter 23 generates a low output signal. When the output of the inverter 23 goes low, the logic product disappears as the output of the AND gate 24, blocking the gate activation signal S1 from the gate activation signal generating circuit 25 through the AND gate 24 and not the optical gate signal - Generation circuit 17 can arrive. The gate activation signal S1 is not a continuous signal, but a pulse signal that is generated with a predetermined phase; however, the period between the discharge of the arm arrester 12 and the blocking of the AND gate 24 is very short, for example a few microseconds, and therefore the gate activation signal S1 will not reach the optical gate signal generation circuit 17 within this period.

Thus, in a case where an abnormal voltage is applied to the thyristor 10 due to an external lightning overvoltage or the like, the thyristors 11 are not turned on even if the gate activation signal generating circuit 25 generates the gate activation signal S1 delivers. Therefore, there are no extremely large switching losses in the thyristors 11. The thyristors 11 therefore do not need to have a high resistance to switching losses.

Although an embodiment of the invention has been described above in a DC power transmission system, the invention is of course not limited to this application, but also finds numerous other applications, e.g. in frequency converters, thyristor starters for synchronous motors, etc.

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Claims (4)

661 383 2nd PATENT CLAIMS 1. Thyristor device, having a plurality of thyristor arms (10), each of which contains at least one thyristor (11), and having a plurality of gate signal generating means (25, 17, 19) assigned to each of the thyristor arms (10) for emitting one Gate signal to each individual thyristor (11), characterized by a plurality of surge voltage deriving means (12) connected in parallel to one of the thyristor arms (10) for protecting the thyristors from surge voltages, a plurality of each with one of the surge voltage deriving means ( 12) associated discharge discharge detection means (16, 20) for detecting a discharge of the surge voltage discharge means (12) and a plurality of each with one of the discharge discharge detection means (16, 20) and one of the gate signal generating means (25, 17, 19 ) related gate signal blocking means (22, 23, 24), each responsive to an output signal of the discharge discharge detection means (16, 20) to the Render gate signal generating means (25, 17, 19) ineffective, each arrester discharge detection means (16, 20) each having a light emitting means (20) which emits light when the respective surge voltage discharge means (12) is discharged, and each gate signal Blocking means (22, 23, 24) each have a light receiver (22) for converting the light signal into an electrical signal. 2. Thyristor device according to claim 1, characterized in that each thyristor arm (10) has two or more series and / or parallel connected thyristors (11). 3. Thyristor device according to claim 1 or 2, characterized in that each gate signal generating means (25, 17, 19) each have a gate activation signal generating means (25) for generating a gate activation signal which enables the generation of the gate signal, and each includes a gate signal generating circuit (17, 19) responsive to the gate activation signal to generate the gate signal, and each gate signal blocking means (22, 23, 24) includes a gate signal blocking circuit (23, 24) for preventing the gate activation signal from being forwarded to the gate signal generating circuit (17, 19). 4. Thyristor device according to claim 3, characterized in that each discharge discharge detection means (16, 20) each have a voltage divider (16) connected in series with the respective discharge means (12) for dividing a voltage caused by a discharge current of the discharge means (12). is generated, that the respective light-emitting means (20) is connected to the voltage divider (16) and is set up to convert the divided voltage into a light signal, and that each gate signal blocking means (22, 23, 24) each have a respective one Light receiver (22), the respective gate activation signal generation means (25) and the respective gate signal generation circuit (17, 19) in connection blocking gate circuit (23, 24) which responds to an output signal of the light receiver (22), in order to prevent the gate activation signal from being forwarded to the respective gate signal generating circuit (17, 19), and also to prevent a plurality of optical fibers means (22) is present, each of which connects one of the light emitting means (20) with one of the light receivers (22).