JPH0965665A - Power converter and its control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter and its method wherein BPP does not occur at both end portions and switching element and DC circuit may be protected even if the same type of fault occurs at both end portions of both systems. SOLUTION: In a method of controlling a power converter, each corresponding phase of different power systems 3, 3 or the power system related to AC is respectively connected via the primary coils of transformers 2, 2 for conversion, a control voltage is applied to a secondary coil of this transformer for conversion and phase and amplitude of this control voltage are controlled via switching elements 1, 1 and a DC circuit having a DC reactor 4 in order to control the flow of power between the power systems. When the voltage of both systems drops, an energy of the DC circuit is forced to exhaust to the AC side and this operation is continued until recovery of the system voltage and thereby the converter is stopped after attenuation of the DC current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter and its control method.

[0002]

2. Description of the Related Art In a power converter of this type which has been generally adopted in the past, corresponding phases of different power systems (or power systems interconnected with alternating current) are respectively connected to primary windings of a transformer for conversion. Connected to the secondary winding of the conversion transformer, while applying a control voltage to the secondary winding, the phase and magnitude of the control voltage is controlled via a DC circuit having a switching element and a DC reactor, It is usual to control the power flow between electric power systems.

Then, the following operation is performed as protection of the converter of the power conversion device. That is,
Operation to forcibly fix the control angle of the switching element to the inverse converter side and to output the energy of the DC circuit to the AC side,
The so-called GS (gate shift) operation, the operation that normally turns on the switching element so as to short-circuit the DC side by ignoring the commutation order, the so-called BPP (bypass pair) operation, and the ON pulse to the switching element is locked. However, the three operations of turning off all phases, the so-called GB (gate block) operation, are used depending on the accident mode, and the circuit breaker is opened (CBT) as the final backup to prevent equipment protection and spread of the accident. I am trying to do it.

In this case, in general, the AC system is generally separated at both ends, the same failure at both ends is not taken into consideration, and the accident end is one end and is protected by the accident aspect of the accident end. The interlocking is determined, the protection interlocking request (GS to GB to CBT) is output to the other end, and the protection is stopped.

[0005] As a related article, there is JP-A-60-241717.

[0006]

[Problems to be Solved by the Invention]
And in the controlled power converter, during normal operation,
Also, it does not cause any particular problem in a normal accident.For example, the AC system to which the converter is connected is connected to the AC system in the vicinity, or a system failure at one end occurs at the other end. If a system fault occurs in a system that also affects the system, this conventional control method links both sides of the BPP for protection, and the direct current continues to flow between the direct current reactor and the switching element, exceeding the withstand capability of the equipment. I hate to deteriorate equipment.

As described above, in the conventional system, when both ends of both systems have the same failure, both ends of the BPP are broken due to the failure.
Therefore, there is a possibility that both ends will be short-circuited while the direct current remains, resulting in loss of control. That is, in the past,
No consideration has been given to the protection operation when the same failure occurs at both ends, and there is a problem in that the BPP is applied at both ends, resulting in an uncontrolled state when a direct current remains.

The present invention has been made in view of the above, and an object thereof is to prevent the switching elements and the DC circuit from being BPP at both ends even when both ends of both systems have the same failure. An object of the present invention is to provide a power converter of this type and a control method thereof.

[0009]

That is, according to the present invention, corresponding phases of different electric power systems or AC-connected electric power systems are connected through primary windings of conversion transformers, respectively, and the conversion is performed. A control voltage is applied to the secondary winding of the power transformer, and the phase and magnitude of the control voltage are controlled via a DC circuit having a switching element and a DC reactor to control the power flow between the power systems. In the control method of the power conversion device to be controlled, when the voltage of the both systems is reduced, the operation of forcibly ejecting the energy of the DC circuit to the AC side is performed, and this operation is continued until the system voltage is restored. By doing so, the direct current is attenuated and then the system is stopped to achieve the intended purpose.

Further, a conversion transformer for connecting corresponding phases of different power systems or AC-connected power systems via respective primary windings, and a secondary winding side of this conversion transformer. And a DC circuit having a switching element for applying a control voltage and a DC reactor, and a control device for controlling the switching element of this DC circuit, wherein the control device includes both When the voltage of the system drops, a means for forcibly ejecting the energy of the DC circuit to the AC side, and this operation is continued until the system voltage is restored, and the converter is stopped after the DC current has decayed. And means for performing it.

[0011]

That is, according to such a power converter and its control method, the protection interlocking sequence in the controller is controlled so as not to be BPP at both ends, and further, when the voltage drops at both ends due to a system failure, On the protection interlocking side of the GS, the GS control is performed to restore the system voltage and continue until the DC current is sufficiently attenuated. Therefore, after the accident, the converter can be stopped stably without leaving energy on the DC side. Therefore, even if both ends of both systems have the same failure, both ends do not become BPP, and the switching element and the DC circuit are sufficiently protected.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows the whole of the power converter in a system, and FIG. 2 shows the action of a direct current when the present invention is applied. There are different power systems, namely system A and system B, and the corresponding phases of these power systems are connected via the primary windings of the conversion transformers 2 and 2, respectively. A control voltage is applied to the next winding side, and the phase and magnitude of the control voltage are controlled by a DC circuit having a switching element (thyristor) 1, 1 and a DC reactor 4 and a converter control device, and a power system. Control the tidal current between. In the figure, 3 is a bus bar, 13 is an arithmetic processing unit, and 14 is a direct current voltage detector.

The converter control device receives the protection relay operation signal (counterpart signal) of the converter protection device 5 and performs the protection operation in the protection interlocking sequence 20, that is, the above-mentioned GS, B.
The PP / GB command output (protection interlocking command) 8 is output.
The automatic pulse phaser (APPS) 12 outputs this command output 8
Then, the gate of the switching element 1 is controlled by the control angle command value 7.

In the case where an accident occurs in the protection interlocking sequence section 20 when the AC / DC circuit breaker 10 is turned on, or in the system where the influence of the system failure in the system C spreads to the systems A and B similarly. , Another protection interlock for each of the systems A and B is performed, or a BPP signal is exchanged between the control devices, and the BPP is locked at the other end of the one end BPP. That is, both ends are prevented from becoming BPP.

Further, in the event of system failure, when the undervoltage relay operates at both ends of the voltage detector 11 and the converter protection device 5, the protection sequence 20 is used, and the GS protection interlocking operation side has the BPP operation signal at the other end. 8 or undervoltage relay operation signal 9 is input, and at the time of self-end undercurrent relay operation,
In order to sufficiently attenuate the DC current, the GS operation is continued for several tens of ms after the undercurrent relay at its own end is restored.

According to such a power converter control method, one end of the BPP does not become a BPP at both ends because the BPP is locked at the other end, and further, the voltage at both ends drops due to a system failure. In this case, the protection interlocking operation side of the GS performs control to restore the GS control to the system voltage and continue to damp the DC current sufficiently. Therefore, after the accident, the converter can be stably operated without leaving energy on the DC side. You can stop. Furthermore, there is an effect that restart control can be performed at high speed.

Further, according to the present invention, when the voltage fluctuation when the converter is stopped due to the system capacity cannot be tolerated at one end, when the other end fails, the own end continues operation, and only the other end is BPP-restart protection interlocking. Is particularly effective when is used.

[0018]

As described above, according to the present invention, even if both ends of both systems have the same failure, both ends do not become BPP, and the switching element and the DC circuit can be sufficiently protected.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of a power conversion device of the present invention.

FIG. 2 is a characteristic diagram showing the movement of a direct current when the present invention is applied.

[Explanation of symbols]

1 ... Thyristor, 2 ... Conversion transformer, 3 ... Bus bar, 4 ... DC reactor, 5 ... Converter protection device, 6 ... Converter control device, 7 ... Control angle, 8 ... Protection interlocking command (GS, BPP, G)
B), 9 ... Counterpart signal (BPP status signal, protection relay operation signal), 10 ... Interconnection circuit breaker, 11 ... Voltage detector, 1
2 ... Automatic pulse phaser (APPS), 13 ... Arithmetic processing unit, 14 ... DC current voltage detector.

Claims (5)

[Claims] 1. Corresponding phases of different electric power systems or AC-connected electric power systems are respectively connected via a primary winding of a conversion transformer, and are connected to a secondary winding of the conversion transformer. While applying a control voltage, the phase and magnitude of the control voltage are controlled via a DC circuit having a switching element and a DC reactor, and the power converter is configured to control the flow between the power systems. In the control method, when the voltage of the both systems is reduced, the operation of forcibly ejecting the energy of the DC circuit to the AC side is performed, and this operation is continuously performed until the system voltage is restored, after attenuating the DC current. A control method for a power conversion device, characterized in that a converter is stopped. 2. Corresponding phases of different power systems or power systems connected by alternating current are respectively connected via primary windings of a conversion transformer, and are connected to secondary windings of the conversion transformer. While applying a control voltage, the phase and magnitude of the control voltage are controlled via a DC circuit having a switching element and a DC reactor, and the power converter is configured to control the flow between the power systems. In the control method, by exchanging a signal that short-circuits the DC side at both ends of the both systems, when the other end is a DC short-circuit, the self-end is locked to be a DC short-circuit, and the switching element is controlled. A method for controlling a power conversion device, characterized in that the angle is fixed to the inverse converter side, and the energy of the DC circuit is discharged to the AC side. 3. The converter according to claim 2, wherein the operation of ejecting the energy of the DC circuit to the AC side is continuously performed until the system voltage is restored, and the converter is stopped after the DC current is sufficiently attenuated. Power converter control method. 4. Corresponding phases of different power systems or power systems interconnected with alternating current are respectively connected via primary windings of a conversion transformer, and are connected to secondary windings of the conversion transformer. While applying a control voltage, the phase and magnitude of the control voltage are controlled via a DC circuit having a switching element and a DC reactor, and the power converter is configured to control the flow between the power systems. In the control method, when both ends of the different power systems have the same failure, one end ignores the commutation order and turns on the switching element so as to short-circuit the DC side, and the other end is forced. Fix the control angle of the switching element to the inverse converter side, let the energy of the DC circuit flow out to the AC side, and extend the fixed control angle of the switching element until the time when the current can be sufficiently reduced after power recovery. The method of the power conversion apparatus characterized by Gosuru. 5. A conversion transformer for connecting corresponding phases of different power systems or AC-connected power systems via primary windings, respectively, and a secondary winding side of this conversion transformer. In a power converter provided with a DC circuit having a switching element for applying a control voltage and a DC reactor, and a control device for controlling the switching element of the DC circuit, the control device includes: When the voltage of the system drops, a means for forcibly ejecting the energy of the DC circuit to the AC side, and this operation is continued until the system voltage is restored, and the converter is stopped after the DC current has decayed. An electric power conversion device comprising: a means for performing the electric power conversion.