JPH0880057A - Protective system of ac-dc converter - Google Patents

Abstract

PURPOSE: To prevent the damage of a thyristor valve and peripheral equipments by forming constitution, in which preceding protection dependence is prior even when protective devices for converters at both ends simultaneously output protective dependence signals. CONSTITUTION: The protective dependence signal of a converter from a converter controller 17B at an opposed end and a protective dependence signal at the time of the detection of short AC voltage or overvoltage from a protective device 18A at its own end are input to a protective interlocking circuit 15A, the signals are output because a time-limit protective dependence signal is continued when the signals are input to an on-delay circuit 22A, and whether or not the converters are brought to the state of a bypass pair is decided. When there is an output from the on-delay circuit 22A and the converters are not brought to the state of the bypass pair, a flip-flop 26A is set by an output from an AND circuit 21A, and the operation of the bypass pair is conducted. Accordingly, even when protective devices for the converters at both ends simultaneously output the protective dependence signals, both ends are not brought to the state of the operation of the bypass pair at the same time, thus preventing the damage of a thyristor valve and peripheral equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection system for an AC / DC converter which controls an AC / DC converter for converting AC power to DC power or DC power to AC power.

[0002]

2. Description of the Related Art A system diagram of a conventional asynchronous interconnection using an AC / DC converter is shown in FIG. As shown in the figure, the AC / DC converters 1A and 1B are connected to each other via a smoothing reactor 2, while they are connected to AC systems 6A and 6B via converter transformers 4A and 4B and breakers 5A and 5B, respectively. It is connected and used for frequency converter, asynchronous interconnection converter, etc.

Now, a control device in the case where the converter is applied to a DC interconnection system will be described with reference to FIG. As shown in the figure, the control device 17A includes a start / stop sequence circuit 14A that controls cooperative control of start and stop of the forward converter and the inverse converter, and a DC power transmission system of the DC transmission system in response to a command from the start / stop control circuit 14A. A control arithmetic circuit 13A for controlling a direct current, a DC voltage and the like to be constant, a phase control circuit 12A for determining an ignition phase of a converter by an output signal of the control arithmetic circuit 13A, and outputting an optimum protection command at the time of an accident. It is composed of a protection interlocking circuit 15A and an abnormality monitoring circuit 16A for monitoring the occurrence of an abnormality in each circuit. Further, the output signal of the phase control circuit 12A in the control device 17A is sent to the pulse amplification circuit 30A, and the pulse amplification circuit 30A
Applies a sequential ignition pulse to the AC / DC converter 1A.

Next, a case where an accident occurs will be described with reference to FIG. 6 showing a system configuration of a conventional AC / DC converter. When an accident occurs, the protective device 18A at the end of the accident
The protection request signal of the protection interlocking circuit 15 of the control device 17A.
The pulse signal is input to A and the protection interlocking circuit 15A outputs a pulse operation signal to the phase control circuit 12A. The protection request signal is also input to the converter control device 17B at the other end. In response to the protection request signal, the protection interlocking circuit 15B outputs a pulse operation signal to the phase control circuit 12B. Here, the movement when the protection device 18A outputs the protection request signal has been described, but the movement when the protection device 18B outputs the signal is the same.

However, the protection interlocking mode differs depending on the aspect of the accident. Here, the protection interlocking when an accident occurs in the AC system will be described. When an accident occurs in the AC system and the AC voltage drops, the AC transmission line is normally closed again after the accident is removed, so the converter stops operating once the accident occurs, that is, when the AC voltage drops. Then, it restarts after reclosing the AC transmission line. The control device of the conversion device receives the protection request signal from the protection device that has detected the AC voltage drop, and stops the operation of the conversion device by the protection interlocking operation. The modes are generally (1) Gate shift (G
After S), the gate block (GB) and restart after accident removal (RESTA), or (2) bypass pair (BPP) and restart after an accident removal (RESTA) are common methods. .

By the way, in the method of (1), since the converter is once blocked, the converter on the accident side outputs a protection request signal to the converter on the sound side, and the converter on the sound side is also stopped. Further, in the method of (2) above, the converter is not blocked, so the converter on the sound side continues to operate. In recent years, there is an increasing need for continuous operation, and more and more systems adopt the protection method of (2) above not only when AC voltage drops but also when overvoltage occurs.

Therefore, the method (2) will be described with reference to the protection interlocking circuit shown in FIG. As shown in the figure, the protection device 18A includes an AC undervoltage relay 31A and an AC overvoltage relay 32A. AC undervoltage relay 31A
Outputs a protection request signal when the AC voltage has dropped, and the AC overvoltage relay 32A outputs a protection request signal when the AC voltage has risen. As a result, the flip-flop circuit 26A of the protection interlocking circuit 15A of the converter control device is set, and when the flip-flop circuit 26A is set,
Bypass pair (B
PP) Generate command. The flip-flop circuit 26A is reset by the protection reset signal. This protection reset signal is output when there is no protection request signal from the protection device after a predetermined time period from the generation of the normal protection request signal.

[0008]

FIG. 8 shows an example of a system configuration in which DC power transmission is performed in a state where the AC systems on the forward converter operation side and the inverse converter operation side are connected. In the figure, AC-DC converters 1A and 1B are connected to AC busbars 10A and 10B via converter transformers 4A and 4B and breakers 5A and 5B, respectively. Further, the AC buses 10A and 10B are connected to the AC systems 6A and 6B via the boosting transformers 7A and 7B and the circuit breakers 8A and 8B, respectively. Further, the AC systems 6A and 6B are also connected to a distant AC bus.

However, in the system configuration as described above, an AC system fault may be detected at both ends at the same time.
The problem at that time will be described below. If the two AC grids connected to the converter are not connected to each other, the AC grid fault only affects either the forward converter side or the inverse converter side. When the protection interlock when detecting the AC voltage drop or the AC overvoltage is BPP-RESTART, the converter on the healthy side continues to operate and suppresses the DC current. However, when two AC systems connected to the converter are connected, if an accident occurs in the AC system, the converters at both ends may detect the accident at the same time. in this case,
If the protection interlock is BPP → RESTART, both ends are in the bypass pair operation state, and the direct current flows back in a state where the current cannot be suppressed. During normal operation, the energizing period of the thyristor valve is 1/3 of one cycle (120
However, in the bypass pair operation state, continuous energization is performed. For this reason, if the flow of direct current exceeds a certain level relative to the rating of the thyristor, severe stress is applied to the thyristor valve, which may damage the thyristor valve and peripheral equipment.

The present invention has been made in order to solve the above-mentioned conventional inconvenience, and an object thereof is to provide a protection request signal to the protection devices of the converters at both ends at the same time in the protection system of the control device for controlling the AC / DC converter. Since the converters at both ends have the function of avoiding the bypass pair operation even when the output is output, the current cannot be suppressed and the direct current flows back, causing severe stress to the thyristor valve and peripheral devices. Another object of the present invention is to provide a highly reliable AC / DC converter protection method that prevents damage to the AC / DC converter.

[0011]

In order to achieve the above object, the first aspect of the present invention provides a protection request in a protection system of an AC / DC converter for converting AC power into DC power or DC power into AC power. An on-delay circuit that receives a signal and an AND circuit that performs a logical product of the output of the on-delay circuit and the protection request signal of the converter connected to the opposite end, and the protection devices for the converters at both ends are Even if the protection request signal is output, the first protection request signal is prioritized and the converters at both ends are prevented from entering the bypass pair state together.

According to a second aspect of the present invention, in a protection system of an AC / DC converter for converting AC power into DC power or DC power into AC power, a reverse converter operation signal, a protection request signal and a forward converter operation end are provided. A first AND circuit for taking the logical product of the protection request signal of the converter, a second AND circuit for taking the logical product of the forward converter operating signal and the protection request signal, and the output of the second AND circuit are input. An AND delay circuit, a third AND circuit that ANDs the output of the ON delay circuit and the protection request signal of the inverter end, and the first AND circuit and the third AND circuit. It consists of an OR circuit that takes the sum, and even if the protection devices of the converters at both ends output protection request signals at the same time, priority is given to the bypass pair at the reverse converter operating end to prevent both converters from entering the bypass pair state together. Characterized by That.

According to a third aspect of the present invention, in a protection system of an AC / DC converter for converting AC power to DC power or DC power to AC power, conversion of a converter signal not on the weak system side, a protection request signal, and an opposite end is performed. A first AND circuit for obtaining a logical product of the protection request signal of the protection device, a second AND circuit for obtaining a logical product of the weak small system side converter signal and the protection request signal, and the second
An on-delay circuit that receives the output of the AND circuit of
A third AND circuit that takes the logical product of the output of the on-delay circuit and the protection request signal at the opposite end, and an OR circuit that takes the logical sum of the first AND circuit and the third AND circuit, Even if the converter protection device outputs the protection request signal at the same time, it is characterized in that both converters at both ends are prevented from entering the bypass pair state as a priority of the bypass pair of the converters connected to the side that is not a weak system. .

[0014]

According to claim 1 of the present invention, even if the protection devices for the converters at both ends simultaneously output protection request signals, the converters do not immediately perform the bypass pair operation due to the on-delay circuit, and the opposite ends do not operate. After confirming that is not in the bypass pair state, operate the bypass pair. Since this operation is performed by the converters at both ends, it is possible to avoid the bypass pair operation at both ends simultaneously.

According to the second aspect of the present invention, even if the protection devices for the converters at both ends output the protection request signals at the same time, the on-delay circuit on the forward converter side causes the converters to immediately bypass the bypass pair. Do not operate, and after confirming that the opposite end is not in the bypass pair state, operate the bypass pair. On the other hand, the inverse converter side performs the bypass pair operation at the same time when the protection request signal is generated. Therefore, only the inverse converter side operates the bypass pair,
It is possible to avoid operating the bypass pair at both ends simultaneously.

According to claim 3 of the present invention, even if the protection devices for the converters at both ends output protection request signals at the same time, the weak delay system side uses the on-delay circuit and the converters immediately bypass the bypass pair. Do not operate, and after confirming that the opposite end is not in the bypass pair state, operate the bypass pair. On the other hand, the non-weak system side operates the bypass pair at the same time when the protection request signal is generated. Therefore, it is possible to avoid that only the inverse converter side performs the bypass pair operation and the both ends simultaneously perform the bypass pair operation.

[0017]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment (corresponding to claim 1) of the present invention. The difference between this embodiment and FIG. 6 already described is that
Since this is a protection interlocking circuit, and other points are the same, the same parts are denoted by the same reference numerals and the description thereof is omitted. In addition,
Since the protection interlock circuits 15A and 15B are the same, only one protection interlock circuit 15A will be described.

As shown in the figure, the protection interlocking circuit 15A
Is an on-delay circuit 22A, an AND circuit 21A,
It is composed of a flip-flop circuit 26A and a bypass pair command generation circuit 27A.

Next, the operation of this embodiment will be described.
The protection interlocking circuit 15A includes a converter control device 17 at the opposite end.
The protection request signal from the converter connected to the opposite end from B and the protection request signal from the protection device 18A at the self end when the AC voltage shortage or the AC overvoltage is detected. When the protection request signal is input to the on-delay circuit 22A, the on-delay circuit 22A outputs a signal because a certain timed protection request signal continues. During this time period, it is determined whether the converter at the opposite end has entered the bypass pair. When the output of the on-delay circuit 22A is present and the converter connected to the opposite end is not in the bypass pair state, the output of the AND circuit 21A sets the flip-flop 26A to perform the bypass pair operation. That is, it is determined that the converter at the opposite end does not operate in the bypass pair even after waiting for a certain period of time, and it is determined that the converter is the bypass pair only in the self end, and at this time, the bypass pair operation starts. In this way, both converters at both ends are prevented from entering a bypass pair state.

As described above, according to this embodiment, in order to prevent the converters at both ends from being in the bypass pair operation state, the output of the on-delay circuit to which the protection request signal is input and the protection request signal are Since it has a first-come-first-served request signal priority function consisting of an AND circuit that takes the logical product of the output of the on-delay circuit that is the input and the protection request signal of the converter connected to the opposite end, the converter at both ends Protector of
Even if the protection request signal is output at the same time, both ends are not in the bypass pair operation state, so the current cannot be suppressed and the current flows back, causing severe stress on the thyristor valve and damage to the thyristor valve and peripheral equipment. Prevent.

FIG. 2 is a block diagram of another embodiment (corresponding to claim 2) of the present invention. The difference from the above-described embodiment is the protection interlocking circuit, and the other points are the same, so the same parts are assigned the same reference numerals and explanations thereof are omitted. Since the protection interlock circuits 15A and 15B are the same, only one protection interlock circuit 15A will be described.

As shown in the figure, the protection interlocking circuit 15A
Is an on-delay circuit 22A and AND circuits 21A and 2A.
3A and 24A, an OR circuit 25A, a flip-flop circuit 26A, and a bypass pair command generating circuit 27A.

Next, the operation of this embodiment will be described.
The protection interlocking circuit 15A includes a converter control device 17B at the opposite end.
Therefore, the bypass request signal of the converter connected to the opposite end and the protection request signal when the AC voltage shortage or the AC overvoltage is detected by the protection device 18A at the self end. When there is a protection request signal in the reverse converter running end converter and the forward converter running end converter is not in the bypass pair state, the flip-flop 26A is set by the outputs of the AND circuit 24A and the OR circuit 25A, and the reverse converter running end converter is set. Operates bypass pair. On the other hand, the protection request signal for the forward converter operating end converter is input to the on-delay circuit 22A. The on-delay circuit 22A outputs a signal when a timed request signal continues. During this time period, it is determined whether the reverse converter running end converter has entered the bypass pair. On-delay circuit 22
When the output of A is present and the reverse converter operating end converter is not in the bypass pair state, the AND circuit 23A and the OR circuit 25A
The output of the flip-flop 26A is set by the output of, and the forward converter operating end converter performs the bypass pair operation. That is, in the forward converter operating end converter, the inverse converter operating end does not perform the bypass pair operation even after waiting for a certain period of time. . In this way, both converters at both ends are prevented from entering a bypass pair state.

As described above, according to the present embodiment, in order to prevent the converters at both ends from being in the bypass pair operation state, the reverse converter operation signal, the protection request signal, and the converter at the forward converter operation end are provided. AND circuit for taking a logical product of the protection request signal of the second AND circuit, a second AND circuit for taking a logical product of the forward converter operation signal and the protection request signal, and an on-delay having the output of the second AND circuit as an input Circuit, an output of this on-delay circuit and a third AND circuit for taking the logical product of the protection request signal at the operating end of the inverse converter, and an inverse circuit consisting of an OR circuit for taking the logical sum of the first AND circuit and the third AND circuit. When the converter operating end bypass pair priority function is provided, even if the converter protection devices at both ends output protection request signals at the same time, both ends will not be in the bypass pair operating state, so the current will be suppressed. Current cannot be returned And to prevent to failure of the thyristor valve and peripherals joined by severe stress to the thyristor valve. Further, the operation end of the forward converter does not cause current interruption even when operating at the minimum current value because the operation is continued by current control, and a more reliable protection system for the AC / DC converter is provided.

FIG. 3 is a block diagram of yet another embodiment (corresponding to claim 3) of the present invention. The difference from the embodiment of FIG. 1 described above is the protection interlocking circuit, and the other points are the same, so the same parts are assigned the same reference numerals and explanations thereof are omitted. Since the protection interlock circuits 15A and 15B are the same, only one protection interlock circuit 15A will be described.

As shown in the figure, the protection interlocking circuit 15A
Is an on-delay circuit 22A and AND circuits 21A and 2A.
3A and 24A, an OR circuit 25A, a flip-flop circuit 26A, and a bypass pair command generating circuit 27A.

Next, the operation of this embodiment will be described.
The protection interlocking circuit 15A includes a converter control device 17B at the opposite end.
Thus, the protection request signal is input from the bypass pair signal of the converter connected to the opposite end and the protection device 18A at the self end when the AC voltage shortage or the AC overvoltage is detected. The converter connected to the side other than the weak system side has the protection request signal and the flip-flop 26A is set by the output of the AND circuit 24A when the opposite end is not in the bypass pair state, and the bypass pair operation is performed.

On the other hand, in the converter on the weak system side, the protection request signal is input to the on-delay circuit 22A. The on-delay circuit 22A outputs a signal when a certain timed protection request signal continues. During this time period, check whether the converter on the non-weak system side has entered the bypass pair. When the output of the on-delay circuit 22A is present and the opposite end is not in the bypass pair state, the AND circuit 23A and the OR circuit 2
The output of 5A sets the flip-flop 26A. In other words, the converter on the weak system side does not bypass the converter on the side that is not the weak system even after waiting for a certain period of time. . In this way, both converters at both ends are prevented from entering a bypass pair state.

As described above, according to the present embodiment, the first AND circuit for taking the logical product of the converter signal not on the weak system side, the protection request signal, and the protection request signal of the converter at the opposite end, the weak system conversion A second AND circuit that takes the logical product of the protection signal and the protection request signal, an on-delay circuit that receives the output of this second AND circuit, and the logical product of the output of this on-delay circuit and the protection request signal at the opposite end In the case where priority is given to the bypass pair of the converter not connected to the weak system side composed of the OR circuit that takes the logical sum of the third AND circuit and the AND circuit of the first AND circuit, Even if the protection device outputs the protection request signal at the same time, both ends will not be in the bypass pair operation state, so the current cannot be suppressed and the current flows back, causing severe stress to the thyristor valve and thyristor. To prevent that lead to damage of the lube and peripherals. Furthermore, the converter connected to the non-weak small system side is given priority to bypass pair operation, and the converter connected to the weak small system side continues operation, so overvoltage on the weak small AC system side can be suppressed and more reliable. It is possible to provide a high protection system for AC / DC converters.

[0030]

As described above, according to the present invention,
Even if the converter protection devices at both ends output protection request signals at the same time, both ends will not enter the bypass pair operation state, so the current cannot be suppressed and the current circulates, causing severe stress on the thyristor valve and thyristor valve. Also, damage to peripheral devices can be prevented. In addition, since the forward converter operating end continues to operate with current control, it does not cause current interruption even when operating at the minimum current value, and furthermore, it preferentially bypasses the converter connected to the side that is not a weak system. Since the converters connected to the weak system side in pair operation will continue to operate,
It is possible to suppress overvoltage on the weak AC system side and provide a more reliable protection system for the AC / DC converter.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment of the present invention.

FIG. 3 is a configuration diagram of still another embodiment of the present invention.

FIG. 4 is a system configuration diagram of an asynchronous interconnection using a conventional AC / DC converter.

FIG. 5 is a configuration diagram of a control device of a conventional AC / DC converter.

FIG. 6 is a system configuration diagram of a conventional AC / DC converter.

FIG. 7 is a partial configuration diagram of a conventional protection interlocking circuit.

FIG. 8 is a system configuration diagram of a conventional AC / DC converter to which AC systems at both ends are connected.

[Explanation of symbols]

1A, 1B ... Converter, 2 ... DC reactor, 4A, 4B
… Transformer transformer, 5A, 5B… Converter breaker, 6
A, 6B ... AC system, 7A, 7B ... Step-up transformer, 8
A, 8B ... Circuit breaker, 10A, 10B ... AC busbar, 11
A ... Transformer, 12A, 12B ... Phase control device, 13A,
13B ... Control arithmetic circuit, 14A. 14B ... Start-stop sequence circuit, 15A, 15B ... Protection interlocking circuit, 16A,
16B ... Abnormality monitoring circuit, 17A, 17B ... Converter control device, 18A, 18B ... Protection device, 21A, 23A, 24
A ... AND circuit, 22A ... ON delay circuit, 26A,
28A ... Flip-flop circuit, 25A ... OR circuit, 2
7A ... Bypass pair command generation circuit, 30A, 30B ... Pulse amplification circuit, 31A ... AC undervoltage relay, 32A ...
AC overvoltage relays, 41A, 42A, 43A, 44A ...
switch.

Claims (3)

[Claims] 1. A protection system for an AC-DC converter for converting AC power into DC power or DC power into AC power,
An on-delay circuit that receives a protection request signal, and an AND circuit that takes the logical product of the output of the on-delay circuit and the protection request signal of the converter connected to the opposite end, and a converter protection device for both ends. A protection system for an AC / DC converter, characterized in that even if the protection request signals are simultaneously output, the first-come-first-served protection request signal is prioritized and the converters at both ends are prevented from entering a bypass pair state. 2. A protection system for an AC / DC converter for converting AC power into DC power or DC power into AC power.
A first AND circuit that takes the logical product of the inverse converter operation signal, the protection request signal, and the protection request signal of the converter at the operating end of the forward converter, and a first AND circuit that takes the logical product of the forward converter operation signal and the protection request signal A second AND circuit, an ON delay circuit that receives the output of the second AND circuit, and a logical product of the output of the ON delay circuit and the protection request signal of the inverse converter operating end
Of the AND circuit and an OR circuit that takes the logical sum of the first AND circuit and the third AND circuit. Even if the protection devices for the converters at both ends simultaneously output protection request signals, the inverse converter operating end The protection method of the AC / DC converter is characterized in that the converters at both ends are prevented from entering the bypass pair state as a priority of the bypass pair. 3. A protection system for an AC / DC converter, which converts AC power to DC power or DC power to AC power,
A first AND circuit for taking the logical product of the converter signal not on the weak system side, the protection request signal, and the protection request signal of the converter at the opposite end, and a first AND circuit for taking the logical product of the converter system signal on the weak system side and the protection request signal. A second AND circuit; an ON delay circuit that receives the output of the second AND circuit as an input; a third AND circuit that ANDs the output of the ON delay circuit and the protection request signal at the opposite end; By-pass of the converter which is composed of an OR circuit for taking the logical sum of the AND circuit of 1 and the third AND circuit and which is connected to the side which is not a weak small system even if the protection devices of the converters at both ends simultaneously output protection request signals. A protection method for an AC / DC converter, characterized in that the converters at both ends are prevented from entering a bypass pair state as a pair priority.