JPH10323047A - Controller for alternating-current-to-direct-current converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for alternating-current-to-direct-current converters which allows a direct-current link to be operated with stability even if the state of an alternating-current system varies. SOLUTION: The frequency of the axial torsional vibration components in an alternating-current system is detected using a frequency detecting means 201A. The axial torsion component is extracted from the output of the frequency detecting means 201A through a frequency filtering means 202A, and phase correction is performed. It is added to the output of a first control block through a limiting means 203A using an adding means 30A. The added signal acts to cancel out the influence of the axial torsion, thus preventing the resonance phenomenon due to interaction with a generator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an AC / DC converter connected to an AC system whose state greatly changes in a DC interconnection system such as a DC transmission system and a frequency converter.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram of a conventional DC interconnection system of a DC transmission system. The main circuit configuration is the converter 1A
And the DC side of the converter 1B are connected via the reactor 2, respectively, and the AC side of each converter 1A, 1B is connected to the AC system 6A, 6B via the converter transformers 4A, 4B and the circuit breakers 5A, 5B, respectively. It is connected to the.

As various detecting means, a DC voltage detecting circuit 7 for detecting a DC voltage, DC current detecting circuits 8A and 8B for detecting a DC current, AC current detecting circuits 9A and 9B for detecting an AC current, AC voltage detection circuits 10A and 10B for detecting a voltage are provided, and are used in a control circuit described below.

The control system includes a constant power control circuit 11, constant voltage control circuits 12A and 12B, a constant margin angle control circuit 13A,
13B and constant current control circuits 14A and 14B.

Next, each control circuit will be described. The constant power control circuit 11 is an active power setting device that sets the outputs of the active power detectors 15A and 15B that determine active power based on the AC current detection circuits 9A and 9B and the AC voltage detection circuits 10A and 10B and a power reference signal. The output of the adder 17 for obtaining a deviation from the output of the input 16 is input, and a current reference signal to be given to the constant current control circuits 14A and 14B is determined so that the active power follows the power reference signal. At this time, the constant power control circuit 11
The output of the active power detector is selected by the selection switch 18 from among the active power detectors 15A and 15B, the output of the active power detector on the side of the converter performing the reverse conversion operation.

The constant voltage control circuits 11A and 11B convert the DC voltage detected by the DC voltage detection circuit 7 into a value which can be easily handled by the control circuit. The output of the voltage / voltage conversion circuit 19 and a DC voltage for setting a voltage reference signal. The outputs of the adders 21A and 21B for obtaining the deviation from the outputs of the setting devices 20A and 20B are input and controlled so that the DC voltage follows the voltage reference signal.

[0007] The constant margin angle control circuits 13A and 13B are based on the outputs of the margin angle setting units 22A and 22B for setting the margin angle reference signal so that the margin angles of the converters 1A and 1B follow the margin angle reference signal. To control.

The constant current control circuits 14A and 14B are provided with a current / voltage conversion circuit 23 for converting the DC current detected by the DC current detection circuits 8A and 8B into a value which can be easily handled by the control circuit.
A current margin setting device for determining the deviation between the outputs of the A and 23B and the current reference signal from the constant power control circuit 11 and selecting the selection switches 24A and 24B on the converter side performing the reverse conversion operation to set the current margin. 25A, 25B
The outputs of the adders 26A and 26B that add the outputs of the above are input, and the DC current flowing through the DC reactor 2 is controlled so as to follow the current reference signal.

The control lead angle priority circuits 27A and 27B include:
The outputs of the constant voltage control circuits 12A, 12B, the outputs of the constant margin angle control circuits 13A, 13B, the constant current control circuits 14A,
The output of the converter 14B is input and the output having the most advanced control angle of the converter is selected and output. Assume that the converter 1
Assuming that B is performing the reverse conversion operation, the control advance angle priority circuit 27A selects the output of the constant voltage control circuit 12A, and the control advance angle priority circuit 27B selects the output of the constant voltage control circuit 12B and the constant margin angle control circuit. The one that advances as the control angle of the output of 13B is selected. Generally, the constant voltage control circuit 12
The output of B is selected.

The outputs of the control lead angle priority circuits 27A and 27B are input to phase control circuits 28A and 28B, where they are converted into pulse signals for determining the firing timing of the converter.
A gate pulse signal is provided to each converter via the pulse amplifier circuits 29A and 29B. Configuring the control circuit in this way is a known technique.

[0011]

The AC system 6A is usually composed of a large number of power plants, transmission lines, substations, etc.
Due to an accident such as a lightning strike, there is a possibility that the converter 1 </ b> A transmits the power of the power plant 61 alone as shown in FIG. 11. Further, when the mechanical torque and the electric torque of the generator cannot be transiently balanced due to the influence of the AC system accident, mechanical stress is applied to the shaft of the generator and the shaft is twisted. If the attenuation of the shaft torsion phenomenon is slow, the attenuation of the frequency component of the shaft torsion vibration in the generator output voltage will be slow.

Further, since the power plant 61 is disconnected from the other part 62 of the AC system due to the AC system accident, the AC bus voltage to which the converter 1A is connected is determined by the output voltage of the generator. Therefore, since the converter inputs an AC voltage in which the axial torsional vibration component is superimposed on the fundamental wave component,
The DC voltage output oscillates with a torsional vibration component, and the DC current also oscillates. Constant current control circuit 14A of converter 1A
Changes the phase control angle of the converter 1A according to the DC current vibration. When the phase control angle of the converter 1A fluctuates, the power of the converter 1A changes, and the effect is transmitted to the generator of the power plant 61. If the power fluctuation of the converter 1A promotes the torsion of the generator, a resonance phenomenon appears and the generator is damaged, and the DC power conversion cannot be performed stably. This phenomenon cannot always be prevented only by the control block of the converter.

An AC system 6 to which the DC interconnection equipment is connected.
When the short-circuit capacity of A becomes small, the resonance point of the circuit composed of the capacitive impedance of the AC filter 63 and the phase adjustment capacitor 64 of the DC interconnection equipment and the system impedance becomes the secondary of the fundamental frequency of the AC system, It appears in the frequency region near the third harmonic. In such a case, problems such as harmonic instability occur as described below, and there is a possibility that stable operation of the DC interconnection facility cannot be performed.

That is, when a harmonic is generated in the voltage of the AC system 6, the converter 1A rectifies the distorted AC voltage, so that a harmonic component is generated in the DC voltage. Further, a harmonic component is generated in the DC current, and conversely, the harmonic current flows out to the AC system 6 via the converter 1A. At this time, the converter 1
If the output of the constant current control circuit 14A of A fluctuates according to the movement of the DC current, the harmonic current flowing out to the AC system 6 may further increase. A voltage harmonic component is generated by the product of the impedance of the AC system 6 and the harmonic current. However, when the short-circuit capacity of the AC system 6 decreases and its resonance point approaches the frequency of the harmonic current flowing out of the converter, the frequency increases. Large harmonic voltage is generated. When such a loop becomes positive feedback, harmonics increase. This phenomenon may be unavoidable in a rigid DC interconnection operation method in which the configuration of the equipment does not change and the control characteristics do not change even when the state of the system changes as in the related art.

As described above, the conventional method has a disadvantage that when the state of the AC system changes and the impedance to the harmonics increases, the harmonics increase and the DC interconnection may not be operated stably. there were. Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a control device for an AC / DC converter capable of stably operating a DC interconnection even when a state of an AC system changes.

[0016]

According to a first aspect of the present invention, there is provided a control device for an AC / DC converter according to the first aspect of the present invention, wherein when a shaft torsion occurs in a generator in an AC system, a shaft torsion vibration component is generated. As a result, the voltage of the AC system fluctuates around the fundamental frequency, and this frequency is detected by the frequency detecting means. At this time, the voltage of the AC system includes harmonics generated from devices other than the generator and the load, and the frequency also fluctuates due to the harmonics. Just take out. The frequency filtering means extracts a torsional component from the output of the frequency detecting means and performs phase correction. The output of the limiter means is added to the output of the control lead angle priority means by the adding means. The added signal cancels the influence of the shaft torsion, so that the resonance phenomenon due to the interaction with the generator can be suppressed. If the output of the frequency filter means is too large, the DC output voltage of the converter fluctuates greatly, and the converter cannot fulfill its original role. Limit the amplitude of the output of the means.

In the control device for an AC / DC converter according to a second aspect of the present invention, when a shaft twist occurs in the generator in the AC system, the voltage of the AC system fluctuates around the fundamental frequency due to the shaft torsional vibration component. Therefore, this frequency is detected by the frequency detecting means. At this time, the voltage of the AC system includes harmonics generated from devices other than the generator and the load, and the frequency also fluctuates due to the harmonics. Just take out. In each frequency filter means,
Different axial torsional components are extracted from the output of the frequency detecting means to perform phase correction. The output of each limiter means is added to the output of the control lead angle priority means by the addition means. The added signal cancels the influence of the shaft torsion, so that the resonance phenomenon due to the interaction with the generator can be suppressed. If the output of the frequency filter means is too large, the DC output voltage of the converter fluctuates greatly, and the converter cannot fulfill its original role. Limit the amplitude of the output of the means.

According to a third aspect of the present invention, there is provided a control device for an AC / DC converter according to the first or second aspect, wherein the AC / DC converter is connected to an AC system by a generator operating state detecting means. The operation state of the generator is monitored, the transmission line state of the AC system is monitored by the transmission line state detection means, and the output of the generator operation state detection means and the output of the transmission line state detection means are determined under predetermined conditions. Is determined by the logic means, and if the condition is satisfied, a signal is output from the limiter means. For example, by obtaining information that the generator being operated by the generator operation state detecting means is a generator that is likely to cause shaft twisting, the generator being operated by the transmission line state detecting means can be output from another AC system. When the information that the connection is disconnected is obtained, a signal is output from the limiter means that the condition is satisfied. The condition of the logic means is to judge whether the state of the AC system is a state where the vibration due to the shaft torsion is naturally attenuated or not, and the limiter is only used when the vibration due to the shaft torsion cannot be naturally attenuated. Since the signal of the means is output, the output of the limiter means is unnecessarily added to the output of the control lead angle priority means in a situation where the state of the AC system is normal and the shaft torsional vibration is naturally attenuated. And can be operated under normal control.

According to a fourth aspect of the present invention, in the control device for an AC / DC converter according to any one of the first to third aspects, the AC state is detected by the system state detecting means. Judgment is made as to whether the state is likely to cause instability, and if the system state detection means determines that the state is likely to cause instability of harmonics, the impedance characteristic of the AC system is controlled to cause instability of harmonics. Switch to difficult characteristics.

According to a fifth aspect of the present invention, in the control device for an AC / DC converter according to the fourth aspect of the present invention, the system status detecting means is operated by a generator connected to an AC system. Generator operation state detection means for monitoring the state, transmission line state detection means for monitoring the transmission line state of the AC system, and the output of the generator operation state detection means and the output of the transmission line state detection means are predetermined. And logic means for determining whether or not the above condition is satisfied, and determines whether or not the AC system is in a state in which harmonic instability is likely to occur.

According to a control device of an AC / DC converter according to a sixth aspect of the present invention, in the control device of the AC / DC converter according to the fourth aspect of the present invention, the system state detecting means is provided with a frequency component of AC voltage waveform distortion of the AC system. A harmonic detecting means for detecting the magnitude is used to determine whether the AC system is in a state where harmonic instability is likely to occur.

According to a seventh aspect of the present invention, in the control device for an AC / DC converter according to the fourth aspect, the system status detecting means is controlled by an operation of a generator connected to an AC system. Generator operation state detection means for monitoring the state, transmission line state detection means for monitoring the transmission line state of the AC system, and harmonic detection means for detecting the frequency component and magnitude of the AC voltage waveform distortion of the AC system. Logic means for judging whether the output of the generator operating state detecting means, the output of the transmission line state detecting means, and the output of the harmonic detecting means satisfy a predetermined condition. It is determined whether the state is likely to cause instability.

According to a control device of an AC / DC converter according to claim 8 of the present invention, in the control device of the AC / DC converter according to claim 4, the impedance characteristic control means includes a phase control for opening and closing a phase control capacitor of an AC system. It is constituted by control means, and by changing the magnitude of the capacitive impedance connected to the AC system by turning on and off the phase adjusting capacitor, the impedance characteristics of the AC system can be controlled and the harmonic resonance phenomenon can be avoided.

According to a ninth aspect of the present invention, in the control device for an AC / DC converter according to any one of the first to third aspects, the generator operating state detecting means connects to the AC system. The operating state of the connected generator is monitored, the transmission line state of the AC system is monitored by the transmission line state detection unit, and the output of the generator operation state detection unit and the output of the transmission line state detection unit are monitored. Is determined by logic means to determine whether the condition satisfies a predetermined condition. When the condition is satisfied, the control parameter of each control means is changed by the control parameter changing means to change the characteristic with respect to the harmonic, thereby reducing harmonic instability. Can be avoided.

According to a tenth aspect of the present invention, there is provided a control device for an AC / DC converter according to any one of the first to third aspects, wherein the generator operating state detection means connects to the AC system. The operating state of the connected generator is monitored, the transmission line state of the AC system is monitored by the transmission line state detection unit, and the output of the generator operation state detection unit and the output of the transmission line state detection unit are monitored. Is determined by a logic means whether the predetermined condition is satisfied, and when the condition is satisfied, each control means is switched to any one of the plurality of control means to change the characteristic with respect to the harmonic, thereby obtaining the harmonic. Instability can be avoided.

According to a control device for an AC / DC converter according to claim 11 of the present invention, in the control device for an AC / DC converter according to any one of claims 1 to 3, the generator operating state detection means connects to the AC system. The operating state of the connected generator is monitored, the transmission line state of the AC system is monitored by the transmission line state detection unit, and the output of the generator operation state detection unit and the output of the transmission line state detection unit are monitored. Is determined by logic means to determine whether the condition satisfies a predetermined condition. When the condition is satisfied, the control parameter of the constant current control means is changed by the control parameter changing means to change the characteristic with respect to the harmonic, thereby making the harmonic unstable. Can be avoided.

According to a control device for an AC / DC converter according to a twelfth aspect of the present invention, in the control device for an AC / DC converter according to any one of the first to third aspects, the generator operating state detecting means connects to the AC system. The operating state of the connected generator is monitored, the transmission line state of the AC system is monitored by the transmission line state detection unit, and the output of the generator operation state detection unit and the output of the transmission line state detection unit are monitored. The logic means determines whether the condition satisfies a predetermined condition. When the condition is satisfied, the constant current control means is switched to any one of the constant current control means, and the harmonic instability is changed by changing the characteristic with respect to the harmonic. Can be avoided.

According to a control device for an AC / DC converter according to a thirteenth aspect of the present invention, in the control device for an AC / DC converter according to the eleventh aspect, the control parameter changing means controls the control parameters of the constant current control means. Gain, advance time constant,
By changing any one of the delay time constants and changing the characteristics with respect to the harmonics, it is possible to avoid harmonic instability.

According to a fourteenth aspect of the present invention, in the control device for an AC / DC converter according to any one of the first to thirteenth aspects, the output of the limiter means is controlled by the constant current control means. Add to output. Normally, when the converter is performing the forward conversion operation, the output of the constant current control means is selected as the output of the control advance angle priority means,
The same effect can be obtained by adding the output of the limiter means to the output of the control lead angle priority means or to the output of the constant current control means.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of the present invention, and here, only a main part of the first embodiment is shown. The first embodiment is shown in FIG.
First control block 100A of the conventional control device shown in FIG.
Control block 200A newly provided at the output of
The second control block 200A detects and processes a shaft torsion generated in a generator in the AC system, and outputs the first control block 100A.
The addition to the output of A cancels the converter operation due to the effect of the shaft torsion, and suppresses the resonance phenomenon due to the interaction with the generator.

A newly added configuration in the first embodiment is a frequency detecting circuit 201A for detecting the frequency of the AC system 6A based on the output of the voltage detecting converter 10A connected to the AC system 6A, and a frequency detecting circuit 201A. The second control block 200A includes a frequency filter circuit 202A that processes the frequency detected by the detection circuit 201A and a limiter circuit 203A that limits the output of the frequency filter circuit 202A.
And an adder 30A for adding the output of the second control block 200A and the output of the first control block.

Next, each element will be described. The frequency detection circuit 201A includes a harmonic filter circuit 211A and a frequency detector 212A.

The harmonic filter circuit 211A is configured by combining filters such as a low-pass filter, a band-pass filter, and a high-pass filter, and extracts only a frequency component close to the fundamental frequency of the input AC voltage, and The second and third harmonics or higher frequency components that appear as distortions are removed. The frequency fluctuation is caused not only by the torsional vibration component of the generator but also by a harmonic generated from a device and a load other than the generator. However, the harmonic component is removed by the harmonic filter circuit 211A to fluctuate around the fundamental frequency. It is possible to take out only the frequency fluctuation due to the twist of the generator.

Without the harmonic filter circuit 211A, the output of the frequency detector 212A described below contains components other than the shaft torsional component due to the harmonic components superimposed on the AC voltage, and the shaft torsional vibration of the generator Control becomes difficult. For example, when the second harmonic is superimposed on the AC voltage,
Depending on the phase of the second harmonic, the period of the positive half-wave of the voltage may be long and the period of the negative half-wave may be short. In such a case, the output of the frequency detector that counts the zero-cross interval has a low frequency in a positive half-wave and has a high frequency in a negative half-wave. Therefore, a high frequency and a low frequency are repeatedly output from the frequency detector every cycle, and it is detected as if the vibration source of the fundamental frequency is in the AC system.

The frequency detector 212A detects the frequency of the AC voltage based on the output of the harmonic filter circuit 211A. The frequency detector 212A counts a zero-cross interval of a signal to detect a frequency, samples and stores a prior waveform, and calculates a phase difference between the waveform and the current waveform. Any detector may be used, such as a detector that uses a lock oscillator to detect synchronization with an AC voltage.

The frequency filter circuit 202A is constituted by a combination of various transfer functions, extracts a frequency change from the fundamental wave frequency, extracts a shaft torsion frequency component included in the change, and furthermore, calculates a vibration phase of the shaft torsion frequency component. To compensate for the phase. In this way, a signal having the same frequency component as the original torsion of the generator and having a certain phase difference is obtained.

The limiter circuit 203A limits the output signal of the frequency filter circuit 202A so as not to be excessive. The output of the first control block 100A is the phase control angle of the converter, and its range is usually about 10 to 160 degrees. However, the output signal of the frequency filter circuit 202A becomes excessive, which corresponds to several tens degrees. In such a signal, the DC output voltage of the converter fluctuates greatly, and the converter cannot fulfill its original role. Therefore, the limiter circuit 203A limits the output signal of the frequency filter circuit 202A to such a size that it can continue to fulfill the original role of the converter.

The adder 30A includes a first control block 10
The output of 0A and the output of the second control block 200A are added. The added signal is input to the phase control circuit 28A, and the phase of the converter is controlled by this signal.

As described above, according to the first embodiment, the phase control of the converter is performed in a fixed relationship with the torsional vibration of the generator, and the power handled by the converter is transferred to the shaft of the generator. It is possible to move in a direction to cancel the torsional vibration.

Next, a second embodiment of the present invention will be described. FIG. 2 is a configuration diagram of a second embodiment of the present invention. The difference from the first embodiment shown in FIG.
The output of the second control block 200A is connected to the constant current control circuit 1
3A.

When the power of the power plant is transmitted by the DC interconnection equipment alone, the converter 1A performs the forward conversion operation. In the forward conversion operation, the DC voltage fluctuates and further the DC current fluctuates due to the influence of the frequency fluctuation of the AC voltage due to the shaft twisting phenomenon of the generator, so that the output of the constant current control circuit 14A fluctuates.

Normally, in the forward converter, the constant current control circuit 14
Since the output of A is selected as the output of the first control block 10A, the same effect as in the first embodiment can be obtained even if the output of the second control block is added to the output of the constant current control circuit 14A. Can be

Next, a third embodiment of the present invention will be described. FIG. 3 is a configuration diagram of the third embodiment of the present invention. The difference from the first embodiment shown in FIG. 1 is that a frequency filter circuit 252A and a limiter circuit 253A having different characteristics are newly added. Adder 3 that adds the output of the second control block 200A and the output of the limiter circuit 253A.
1A.

Although a plurality of generators are connected to the AC system, the mechanical and electrical characteristics of the generators are different from each other, and the torsional vibration frequencies of the generators are naturally different from each other. Therefore, when there are a plurality of generators, it is necessary to adjust the control block for the torsional vibration frequency of each generator.

Therefore, the output of the frequency detection circuit 201A is input to frequency filter circuits 202A and 252A having characteristics suitable for the shaft torsional vibration frequency of each generator, and the adder 31A is provided via limiter circuits 203A and 253A, respectively.
The first control block 100 is added by the adder 30A.
The output of A and the output of the adder 31A are added.

In this manner, even when there are a plurality of shaft torsional vibration frequencies of the generator, the vibration can be suppressed. Here, the case where the adder 30A is provided at the output of the first control block 100A has been described.
Similar effects can be obtained by providing the output of the constant current control circuit 14A as in the embodiment. In addition, even when there is one generator, if there are a plurality of shaft torsional vibration frequencies, a frequency filter circuit suitable for a plurality of shaft torsional vibration frequencies can be provided in the same manner. Also, here, the case where there are two shaft torsional vibration frequencies is shown,
When there are two or more shaft torsional vibration frequencies, it can be handled by providing a frequency filter circuit according to the number of shaft torsional vibration frequencies.

Next, a fourth embodiment of the present invention will be described. FIG. 4 is a configuration diagram of a fourth embodiment of the present invention. The difference from the first embodiment shown in FIG. 1 is that a shaft twist is generated by newly detecting the state of the AC system. Second control block 2 for determining whether the state is easy
The point is that a third control block 300A for controlling the output of 00A is provided.

The third control block 300A includes a generator state detection circuit 301A, a transmission line state detection circuit 302A, and a logic circuit 303A. The generator state detection circuit 301A detects what kind of generator is connected to the AC system and is operating, and is configured by a circuit that receives generator operation state information from the power plant. And
It is determined whether the operating generator is a generator that easily generates shaft torsion or a generator that is unlikely to generate twist.

The transmission line state detection circuit 302A detects the state of the transmission line, and determines, for example, whether the power plant has been disconnected from other parts of the AC system due to an AC system accident.

The logic circuit 303A determines whether the outputs of the generator state detection circuit 301A and the transmission line state detection circuit 302A satisfy the conditions, and if the conditions are satisfied, the limiter circuit 203A of the second control block. Is output.

Thus, even if shaft torsion occurs, the second control block 200A is unnecessarily used in a situation where the shaft torsion vibration naturally attenuates in the normal state of the AC system.
Is not added to the output of the first control block 100A, and the DC interconnection can be continued by the normal converter control.

Next, a fifth embodiment of the present invention will be described. FIG. 5 is a configuration diagram of a fifth embodiment of the present invention. In the fifth embodiment, the state of the AC system is determined,
When the harmonic is easily generated, the impedance characteristic of the AC system to which the converter is connected is changed.

In the fifth embodiment, a generator state detection circuit 301A, a transmission line state detection circuit 302A, and a logic circuit 30
3A and a phase control circuit 600A.

The fourth control block 400A is the same as the third embodiment described in the fourth embodiment.
It is determined whether the state of the AC system is in a state where harmonics are likely to occur. For example, if an accident occurs in the AC system, the power plant 61 is disconnected from the other part 62 of the AC system, and the power plant 61 is operating only with a small-capacity generator, It can be determined that harmonic instability is likely to occur.

In the phase control circuit 600A, when the fourth control block 400A detects a state in which harmonic instability is likely to occur, it receives an interrupt signal and
01A operates to turn on and off the circuit breaker of the phase adjustment capacitor 64, thereby switching the frequency-impedance characteristic of the AC system to a characteristic in which harmonic instability does not easily occur.

As a result, it is possible to avoid instability of harmonics in the AC system. Next, a sixth embodiment of the present invention will be described. FIG. 6 is a block diagram of the sixth embodiment of the present invention. The difference from the fifth embodiment shown in FIG. 5 is that the fourth control block 400A is used to determine the frequency component of the AC voltage waveform distortion. The point is that the harmonic instability of the AC system is determined from the size.

The harmonic detection circuit 410A provided in the fourth control block 400A determines whether the harmonic component of the frequency causing the instability phenomenon in the AC voltage is increased and the harmonic instability is likely to occur. Judgment is made from the frequency component and magnitude during voltage distortion.

By operating the interrupt control circuit 601A with the signal from the harmonic detection circuit 410A, the same effect as in the fifth embodiment can be obtained. Next, a seventh embodiment of the present invention will be described.

FIG. 7 is a block diagram of the seventh embodiment of the present invention. The difference from the fifth embodiment shown in FIG. 5 is that the fourth control block 400A is different from the state of the AC system. The point is that the harmonic instability of the AC system is determined from the frequency component and the magnitude of the AC voltage waveform distortion.

The fourth control block 400A includes a generator state detection circuit 301A for detecting what kind of generator is connected to and operating on the AC system, and a transmission line state detection circuit for detecting the state of the transmission line. 302A, a harmonic detection circuit 410A for judging the instability of the harmonics from the frequency component and magnitude of the AC voltage distortion for detecting the state of the transmission line, a generator state detection circuit 301A and a transmission line state detection circuit 302A. The logic circuit 303A determines whether the output from the wave detection circuit 410A satisfies the condition.

As a result, since the information for judging the situation in which more harmonic instability is generated is used than in the fifth and sixth embodiments, the occurrence situation of the harmonic can be judged more accurately.
Next, an eighth embodiment of the present invention will be described.

FIG. 8 is a block diagram of an eighth embodiment of the present invention. The difference from the fourth embodiment shown in FIG. 4 is that the constant voltage control of the first control block 100A is newly performed. Circuit 12A, constant margin angle control circuit 13A, and constant current control circuit 1
The point is that a control parameter changing circuit 700A for changing the control parameter of 4A is provided.

As described in the fourth embodiment, the third
In the control block 300A, it can be determined whether or not the situation is such that the shaft torsion easily occurs. In a situation where shaft torsion is likely to occur, the AC system is very weak and harmonic instability is likely to occur.

Therefore, the limiter circuit 203A is opened by the output signal of the third control block 300A, and the constant voltage control circuit 12A and the constant margin angle control circuit 13A of the first control block 100A are fixed by the control parameter changing circuit 700A. By changing the control parameters of the current control circuit 14A, the characteristics of the converter with respect to harmonics change, and harmonic instability can be avoided.

As described above, in the eighth embodiment,
The harmonic instability of the AC system can be avoided, and the synergistic effect with the suppression of shaft torsional vibration can suppress the inconvenient phenomenon when the power of the power plant is transmitted by DC interconnection alone and stable conversion. Operation of the vessel becomes possible.

Here, the case where the control parameters of the constant voltage control circuit 12A, the constant margin angle control circuit 13A, and the constant current control circuit 14A of the first control block 100A are changed has been described. When the operation is performed, the constant current control circuit 14A is normally selected, so that the same effect can be obtained by changing only the control parameters of the constant current control circuit 14A. Further, when the constant current control circuit 14A is configured by a lead-lag transfer function,
There are three types of control parameters: gain, lead time constant, and delay time constant. Any of these parameters can be changed to change the harmonic response characteristics of the converter.

Next, a ninth embodiment of the present invention will be described. FIG. 9 is a block diagram of a ninth embodiment of the present invention. The difference from the eighth embodiment shown in FIG. 8 is that a control circuit having a plurality of different control parameters is used to change the control parameters. The point is that switching is performed.

In the ninth embodiment, the constant voltage control circuit 12A, the constant margin angle control circuit 13A, and the constant current control circuit 14A of the first control block 100A are provided in a plurality, respectively, and the output thereof is controlled by the control block selection circuit 721A. 722A, 723
Input to A. Control block selection circuits 721A, 722
A and 723A switch the output according to the output of the third control block 300A.

With this configuration, the same effect as in the eighth embodiment can be obtained. Further, here, the constant voltage control circuit 12A, the constant margin angle control circuit 13A, and the constant current control circuit 14A of the first control block 100A are all provided with a plurality of control circuits. When the operation is performed, the constant current control circuit 14A is normally selected, so that a similar effect can be obtained even if only a plurality of constant current control circuits 14A are provided.

[0070]

As described above, according to the control device for an AC / DC converter of the present invention, the torsional vibration of the generator can be prevented and the harmonic resonance can be avoided. In the case where power is transmitted from a power station, stable power transmission can be continued, the reliability of power supply can be improved, and DC interconnection can be used to maintain the stability of the AC system. .

[Brief description of the drawings]

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

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

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

FIG. 4 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of a seventh embodiment of the present invention.

FIG. 8 is a configuration diagram of an eighth embodiment of the present invention.

FIG. 9 is a configuration diagram of a ninth embodiment of the present invention.

FIG. 10 is a block diagram of a conventional DC interconnection system of a DC transmission system.

FIG. 11 is an explanatory diagram of an AC system at the time of an AC system accident.

[Explanation of symbols]

 1A ... Converter 6A ... AC system 12A ... Constant voltage control circuit 13A ... Constant margin angle control circuit 14A ... Constant current control circuit 27A ... Control lead angle priority circuit 30A ... Adder 64 ・ ・ ・ Phase adjusting capacitor 100A ・ ・ ・ First control block 200A ・ ・ ・ Second control block 201A ・ ・ ・ Frequency detection circuit 202A, 252A ・ ・ ・ Frequency filter circuit 203A, 253A ・ ・ ・ Limiter Circuit 211A: Harmonic filter circuit 212A: Frequency detector 300A: Third control block 301A: Generator status detection circuit 302A: Transmission line status detection circuit 303A: Logic circuit 400A ... 4th control block 410A ... harmonic detection circuit 600A ... phase control circuit 601A ... interrupt control circuit 7 0A · · · control parameter changing circuit 721A · · · control parameters switching circuit

Claims (14)

[Claims] 1. A constant current control means for controlling a DC current of an AC / DC converter to follow a DC current reference, and a constant voltage control means for controlling a DC voltage of the AC / DC converter to follow a DC voltage reference. AC / DC having constant margin angle control means for controlling the margin angle of the converter so as to follow the margin angle reference, and control advance angle priority means for selecting the output of the control means which is advanced as the control angle of these control means In the converter control device, frequency detection means for detecting the frequency of the AC system to which the AC / DC converter is connected, frequency filter means for extracting a shaft twist frequency component from the output of the frequency detection means and performing phase correction, A limiter for limiting an output of the frequency filter, and an adder for adding an output of the limiter and an output of the control lead angle priority unit. Control device for direct converter. 2. A constant current control means for controlling the DC current of the AC / DC converter to follow the DC current reference, and a constant voltage control means for controlling the DC voltage of the AC / DC converter to follow the DC voltage reference. AC / DC having constant margin angle control means for controlling the margin angle of the converter so as to follow the margin angle reference, and control advance angle priority means for selecting the output of the control means which is advanced as the control angle of these control means In a converter control device, a frequency detecting means for detecting a frequency of an AC system to which an AC / DC converter is connected, and a plurality of frequency filters for extracting a different torsion frequency component from an output of the frequency detecting means and performing phase correction. Means, a plurality of limiter means for limiting the output of the plurality of frequency filter means,
A control device for an AC / DC converter, comprising an adder for adding outputs of the plurality of limiters and an output of the control lead angle priority unit. 3. The control device for an AC / DC converter according to claim 1 or 2, wherein a generator operation state detecting means for monitoring an operation state of the generator connected to the AC system, and a transmission line of the AC system. Transmission line state detection means for monitoring a line state, and logic means for judging whether an output of the generator operation state detection means and an output of the transmission line state detection means satisfy a predetermined condition, A control device for an AC / DC converter, wherein the limiter means is opened and closed by an output of the means. 4. The control device for an AC / DC converter according to claim 1, wherein a system state detecting means for determining whether the AC system is in a state in which harmonic instability is likely to occur, A control device for an AC / DC converter, comprising: impedance characteristic control means for controlling impedance characteristics of an AC system according to an output of the system state detecting means. 5. The control device for an AC / DC converter according to claim 4, wherein the system state detecting means monitors a running state of a generator connected to an AC system, A transmission line state detection means for monitoring a transmission line state of the system, and a logic means for determining whether an output of the generator operation state detection means and an output of the transmission line state detection means satisfy a predetermined condition. A control device for an AC / DC converter, comprising: 6. The control device for an AC / DC converter according to claim 4, wherein the system state detecting means comprises a harmonic detecting means for detecting a frequency component and a magnitude of an AC voltage waveform distortion of the AC system. Characteristic control device for AC / DC converter. 7. The control device for an AC / DC converter according to claim 4, wherein the system state detecting means monitors a running state of a generator connected to an AC system, Transmission line state detection means for monitoring the state of the transmission line line of the system; harmonic detection means for detecting the frequency component and magnitude of the AC voltage waveform distortion of the AC system; output of the generator operation state detection means and the transmission A control device for an AC / DC converter, comprising: an output of an electric wire state detection means; and a logic means for determining whether an output of the harmonic detection means satisfies a predetermined condition. 8. The control device for an AC / DC converter according to claim 4, wherein said impedance characteristic control means comprises a phase adjustment control means for opening and closing a phase adjustment capacitor of an AC system. Control device. 9. The control device for an AC / DC converter according to claim 1, wherein a generator operating state detecting means for monitoring an operating state of the generator connected to the AC system, Transmission line state detection means for monitoring a transmission line state of a system, and logic means for determining whether an output of the generator operation state detection means and an output of the transmission line state detection means satisfy a predetermined condition, A control parameter changing means for changing a control parameter of each of the control means in accordance with an output of the logic means. 10. The control device for an AC / DC converter according to claim 1, wherein a generator operating state detecting means for monitoring an operating state of the generator connected to the AC system, Transmission line state detection means for monitoring a transmission line state of a system, and logic means for determining whether an output of the generator operation state detection means and an output of the transmission line state detection means satisfy a predetermined condition, A plurality of constant current control means having different control parameters, a plurality of constant voltage control means having different control parameters, a plurality of constant margin angle control means having different control parameters, and each of the control means according to an output of the logic means. A control device for an AC / DC converter, comprising: control parameter switching means for switching to any one of a plurality of control means. 11. A generator operating state detecting means for monitoring an operating state of a generator connected to an AC system in the control device for an AC / DC converter according to any one of claims 1 to 3, Transmission line state detection means for monitoring a transmission line state of a system, and logic means for determining whether an output of the generator operation state detection means and an output of the transmission line state detection means satisfy a predetermined condition, A control parameter changing means for changing a control parameter of the constant current control means in accordance with an output of the logic means. 12. The control device for an AC / DC converter according to claim 1, wherein a generator operating state detecting means for monitoring an operating state of the generator connected to the AC system, Transmission line state detection means for monitoring a transmission line state of a system, and logic means for determining whether an output of the generator operation state detection means and an output of the transmission line state detection means satisfy a predetermined condition, AC / DC conversion comprising: a plurality of constant current control means having different control parameters; and control parameter switching means for switching the constant current control means to one of the constant current control means in accordance with an output of the logic means. Control device. 13. The control device for an AC / DC converter according to claim 11, wherein the control parameter changing means is any one of a control gain, a lead time constant, and a delay time constant among the control parameters of the constant current control means. A control device for an AC / DC converter, characterized in that: 14. The control device for an AC / DC converter according to claim 1, wherein said adding means adds an output of said limiter means and an output of said constant current control means. Characteristic control device for AC / DC converter.