JP2557488B2 - Variable speed generator motor controller - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for performing a variable speed operation by secondary excitation of a secondary winding of a variable speed generator-motor using a cycloconverter, and particularly when the power supply is fluctuating. The present invention relates to a control device for a variable-speed generator-motor that can continue operation stably without stopping even when a secondary winding transient phenomenon occurs.

[Conventional technology]

Generally, an inverter or a cycloconverter is used as a frequency converter for secondarily exciting the secondary winding of the generator motor at a slip frequency. In particular, when applied to a pumped-storage power plant that performs a power generation operation or a pumping operation on an electric power system, it is general to use a cycloconverter capable of performing a wide range of reactive power control. When the cycloconverter that constitutes the frequency converter has a large capacity, it is preferable to use the non-circulation cycloconverter because the equipment capacity and the cost can be reduced. However, in a power plant where the secondary winding is subjected to secondary excitation to perform variable speed operation, if a three-phase imbalance occurs due to power system disturbance or power fluctuation due to charging of the main transformer of another power plant, the transient DC The rotation frequency component induced in the secondary winding by the current component is superimposed on the slip frequency component. Therefore, there occurs a period in which the current is flowing in the direction opposite to the conduction direction of the cycloconverter. The cycloconverter cannot pass the current in the reflection direction, and as a result, the secondary circuit is opened, and the overvoltage is applied to the cycloconverter, which damages the thyristor. Protecting a cycloconverter with this kind of overvoltage
No. 62-71496.

[Problems to be Solved by the Invention]

The cycloconverter is configured by connecting a positive side thyristor converter and a negative side thyristor converter in anti-parallel, and both thyristor converters are switched depending on the current direction. The switching of the thyristor converter is performed after performing the gate block operation of the thyristor converter which has been flowing. However, during transients such as power fluctuations, even if the gate block is operated, the current flows again without extinguishing the arc. The above-mentioned prior art does not consider the failure of the gate block operation at the time of switching between the two thyristor converters during such a transition. If the gate block operation fails, the cycloconverter does not commutate and the transient current continues to flow in an unlimited state only in the thyristor immediately before the gate block, resulting in thermal destruction of the thyristor. In addition, since there is no commutation, the excitation transformer has a problem that it corresponds to a direct current that allows only two phases of the three-phase winding to flow, and causes a DC bias of the transformer.

It is an object of the present invention to provide a control device for a variable speed generator-motor, which is capable of self-recovering and stable operation when a gate block failure of the above phenomenon occurs.

[Means for solving the problem]

The above object is achieved by performing gate shift operation of the thyristor converter when the thyristor converter to be extinguished by the gate block operation continues to flow, and narrowing the current to perform switching of both thyristor converters again. It

[Action]

When the gate block operation fails, the thyristor converter gate block in one of the flow direction is performed, and at the same time, the gate shift operation of the other thyristor converter that failed the commutation is performed to reduce the current. When the current becomes zero, the other thyristor converter is gate-blocked to switch to the one thyristor converter and the current is controlled to the current according to the exciting current command value, so that the normal operation can be restored.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows an embodiment applied to a hydroelectric power plant that performs variable speed pumped storage power generation by a pump turbine.

In FIG. 1, the primary side of a variable speed generator-motor 1 (hereinafter abbreviated as variable speed machine) directly connected to a pump turbine 2 is connected to a power system 5 through a circuit breaker 8 and a main transformer 4. . The secondary side of the variable speed machine 1 is connected to the main transformer 4 by a non-circulation type cycloconverter 3-1 to 3-3 (hereinafter abbreviated as CYC) and a transformer for excitation 7-1 to 7-3. Has been done. Here, subscripts 1 to 3 are the first phase in the three-phase winding,
It represents the second phase and the third phase. The cycloconverter 3 is a thyristor converter which is connected by Graetz as shown in FIG.
It is configured by connecting SP and SN in anti-parallel. An instrument current transformer CT is installed between the CYC3 and the excitation transformer 7 to convert the CYC3 converter current I.
Detect _fb . The voltage detectors 14-1 to 14-3 detect the voltage between the anode and the cathode of the thyristor that composes CYC3 across all the arms, and by the logical product of them, the voltage establishment signal VFD
Is output. When the voltage establishment signal VFD is at "1" level, it means that the voltage is applied to all the arms of CYC3 and no current is flowing. The power control calculator 15 performs active power and reactive power control calculations, is directly connected to the rotor shaft of the variable speed machine 1, and is connected to the rotor shaft of the variable speed machine 1 by the phase signal θ of the phase detector 6 and the slip frequency sf. Set I _ref1 -1 to I _ref -3 to C
Output to the YC control circuits 9-1 to 9-3. CYC control circuit 9
Is the current control calculator 11 that controls the current based on the excitation current command I _ref and the actual current detection value I _fb and outputs the control phase angle α to the automatic pulse phase shifter 10, and the current that detects zero current of the actual current I _fb. Zero control 13, zero detection IZ of current zero detector 13, voltage establishment signal VFD, and gate control that outputs gate switching signal PG, NG that switches thyristor converter SP, SN of CYC3 from excitation current command I _ref It is composed of a circuit 12 and an automatic pulse phase shifter 10 for applying a trigger pulse to the thyristor of CYC from the gate switching signals PG, NG and the control phase angle α. The power control calculator 15, the current control calculator 11, and the gate control circuit 12 can also be configured by a microcomputer.

 Next, the operation will be described with reference to FIGS.

Since the operation during steady operation is described in detail in the above-mentioned JP-A-62-71496, it is omitted, and the operation of the thyristor converter SP is omitted.
SN switching and operation when a gate fault operation fails due to a system fault will be explained.

 An example of the processing of the microcomputer will be described.

Now, _assume that the exciting current command I _ref changes from negative to positive at time t ₁ in FIG.

The process proceeds from step 16 to step 17 in FIG. 3 and the gate control circuit 12 gives a gate shift command GS to the current control calculator 11. The current control calculator 11 narrows down the current to the automatic pulse phase shifter 10 using the control phase angle α as the gate shift phase. Current at time t ₂ is is the current zero signal IZ of zero current detector 13 to zero to perform the gate block operation of CYC3 proceeds to step 19 becomes "1" level. Next, in step 20, it is detected that the voltage establishment signal VFD of CYC3 is ON (“1” level), and in step 21, gate switching is executed at time t ₃ . Then, in step 22, the gate shift command GS is reset. Performing these operations, the negative side thyristor converter SN
To the positive side thyristor converter SP.

Next, it is assumed that an accident occurs in the power system 5 at time t ₀ and an accident current is induced in the secondary circuit of the variable speed machine 1. At time t ₄ , the excitation current command I _ref becomes zero and at time t ₅ , the current zero signal
Since IZ is turned on (“1” level), the gate block operation is performed by the processing of step 18. However, the current in the positive side thyristor converter SP is not cut off by the induced voltage induced in the variable speed machine due to a power system accident, and the current in the positive side thyristor converter SP increases again at time t ₅ . The current zero signal IZ becomes OFF “0” level, and the voltage establishment signal VFD does not become “1” level.
If the voltage establishment signal VFD does not go to "1" level, go to step 24 with a time limit set by the timer in step 23.
At t _{6, the} positive side thyristor converter SP deblocks (gate on) and re-commits. As a result, it is possible to prevent problems such as DC bias magnetization of the excitation transformer 7. Then step 17
Return to and set the gate shift phase of the positive side thyristor converter SP to narrow the current. At time t ₇ , when the current zero signal IZ becomes “1” level again, the gate block is performed.
At t ₈ , the gate is switched to the negative side thyristor converter SN where the voltage establishment signal VFD becomes “1” level. As a result, it is possible to return to the steady operation and continue the operation, so that stable operation can be performed.

By the way, the chain double-dashed line from time t _{7 in} FIG. 4 indicates that the gate block has failed again. If such a phenomenon occurs continuously, a considerable abnormality has occurred in the main circuit. It is expected to be. In this case, as shown in FIG. 5, steps 25 to 27 are added to the steps shown in FIG. 3, and a process of stopping the gate blocks when they successively occur is added. As a result, damage to the variable speed machine 1 can be prevented.

〔The invention's effect〕

According to the present invention, the variable speed generator / motor device can be quickly restored even if the gate block of the cycloconverter for secondary excitation of the variable speed generator / motor, which occurs in the event of a power system accident or fluctuation, can be promptly restored and stable operation can be continued. It is effective in improving the performance and reliability.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a detailed circuit diagram of a cycloconverter, FIG. 3 is a flow chart for explaining the operation, FIG. 4 is a waveform diagram for explaining the operation, and FIG. 6 is a flowchart in another embodiment of the present invention. 1 ... Variable speed generator motor, 2 ... Pump turbine, 3 ... Cyclo converter, 4 ... Main transformer, 5 ... Electric power system,
6 ... Phase detector, 7 ... Excitation transformer, 8 ... Circuit breaker, 9 ... Cyclo converter control circuit, 10 ... Automatic pulse phaser, 11 ... Current control calculator, 12 ... Gate control Circuit, 13 ... current zero detector, 14 ... cycloconverter element voltage detector, 15 ... power control calculator, SP ... positive side thyristor converter, SN ... negative side thyristor converter.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hiroshi Sugisaka 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Omika factory (72) Inventor Hiroshi Kashiwazaki 3-chome, Saiwai-cho, Hitachi-shi, Ibaraki No. 1 inside Hitachi factory, Hitachi Ltd. (72) Inventor Takashi Kano 3-1-1, Saiwaicho, Hitachi city, Ibaraki prefecture Inside Hitachi factory, Hitachi Ltd. (72) Inventor Main tax Tanaka, 3-chome, Hitachi city, Ibaraki prefecture No. 1-1 Hitachi Ltd., Hitachi Plant (72) Inventor Eizo Kita 3-3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Inventor Hiroto Nakagawa Kita-city, Osaka-city, Osaka Prefecture 3-3-22 Nakanoshima-ku, Kansai Electric Power Co., Inc. (72) Inventor Taisho Ohno 3-3-22 Nakanoshima 3-32 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture (56) Visit References JP 63-140697 (JP, A) JP 62-254698 (JP, A)

Claims (2)

(57) [Claims] 1. A secondary excitation control is performed by connecting a non-circulation type cycloconverter constituted by connecting a positive side thyristor converter and a negative side thyristor converter in antiparallel to each secondary side phase of a generator motor. In the control device of the variable speed generator-motor to perform, when switching between the positive side thyristor converter and the negative side thyristor converter, when the thyristor converter to be extinguished by gate block operation continues to flow, the gate of the thyristor converter A control device for a variable-speed generator-motor, characterized in that a shift operation is performed to reduce the current and the switching operation is executed again. 2. The control device for a variable speed generator-motor according to claim 1, wherein when the gate-block operation of the thyristor converter to be extinguished by the gate-block operation reaches a predetermined number of times, the generator-motor is stopped.