JP2634692B2 - Secondary overvoltage protection device for AC-excited synchronous machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary overvoltage protection device for an AC-excited synchronous machine in a variable-speed pumped-storage power generation system that performs pumped-storage power generation using a secondary AC-excited synchronous machine. Things.

[Conventional technology]

FIG. 3 is a circuit diagram showing a secondary overvoltage protection device of a conventional secondary AC excitation type synchronous machine (hereinafter abbreviated as AESM). In the figure, reference numeral 1 denotes AESM which connects the primary side to the system. , 2
The secondary side is connected to a secondary excitation device 2 described later. Reference numeral 2 denotes a secondary excitation device that controls the amount of AC excitation to the AESM1 by controlling the firing angle, and 3 denotes an arrester (lightning arrester) for protecting the secondary excitation device 2 with the overvoltage value of the AESM1 when a secondary overvoltage occurs. Device), 4 is a secondary resistance circuit for suppressing transfer energy to the secondary excitation device 2 when a secondary overvoltage occurs,
5 is a thyristor switch for controlling ON / OFF of the secondary resistance circuit 4; 6 is a secondary short circuit breaker for short-circuiting the secondary circuit of the AESM1 to cut off energy transferred to the secondary excitation device 2; Reference numeral 7 denotes an overvoltage detection device that detects an overvoltage value when a secondary overvoltage occurs and supplies an ignition signal to the thyristor switch 5. Reference numeral 20 denotes a transformer whose primary side is the system side. Reference numeral 30 denotes a converter that converts AC to DC. Is a capacitor for smoothing the DC voltage of the converter 30.

Next, the operation will be described. First, the AESM 1 normally performs the AC excitation operation by converting the DC voltage that has been exchanged and directly converted by the converter 30 into AC again by the secondary excitation device 2. In such a state, if an abnormal phenomenon such as short circuit or unbalanced load occurs on the primary side, the secondary side of AESM1
As a reaction to the abnormal phenomenon, a back electromotive force is generated and appears as a large abnormal voltage. Since this abnormal voltage is a high voltage, when the voltage value exceeds the limit voltage value of the arrester 3, the arrester 3 immediately performs a discharging operation and suppresses the voltage applied to the secondary excitation device 2 to the limit voltage value of the arrester 3. I do. Thereafter, an overvoltage is detected by the overvoltage detector 7, and the thyristor switch 5 is operated to insert the secondary resistance circuit 4 so as to extinguish the energy. If the abnormal phenomenon is still intermittent, the secondary short circuit breaker 6 is turned on to shut off the energy transferred to the secondary excitation device 2 to protect it from high voltage breakdown. If the abnormal phenomenon is eliminated before the operation of the secondary short-circuit breaker 6, the current flowing through the thyristor switch 5 that has been operated once becomes zero, so that natural commutation starts. Therefore, the thyristor switch 5 returns to the normal state, and returns to the AC excitation operation by the secondary excitation device 2.

[Problems to be solved by the invention]

The secondary overvoltage protection device of the conventional AC-excited synchronous machine is configured as described above. If an abnormal phenomenon occurs on the primary side of the AESM, the energy of the secondary overvoltage generated on the secondary side is converted to a thyristor. The switch must be turned on instantaneously and consumed by the secondary resistance circuit. For that purpose, a large-capacity secondary resistance circuit is required. In addition, there are cases where the overvoltage induced on the secondary side of the AESM becomes an alternating current including a DC component. In such a case, the thyristor switch may not commutate. At this time, there was a problem that the secondary AC excitation operation could not be restarted even though the abnormal state had already been resolved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and can eliminate a thyristor switch and a secondary resistance circuit, and can solve a case where an abnormal state is resolved before the operation of a secondary short circuit breaker. To obtain a secondary overvoltage protection device for an AC-excited synchronous machine that can restart the secondary AC excitation operation immediately after the abnormal condition is resolved by forcibly interrupting the current flowing to the secondary side of the AESM With the goal.

[Means for Solving the Problems] The secondary overvoltage protection device for an AC-excited synchronous machine according to the present invention includes a short-circuit diode that flows in a reverse direction through a GTO (gate turn-off transistor) for each phase of the secondary excitation device. Two units are installed in series, the midpoint of the short-circuit diode for each phase is connected in common, and when an abnormal voltage occurs, a part of the GTO is ignited by the overvoltage detection device according to the voltage between the lines. To short-circuit the secondary circuit of AESM and use GTO
Is forcibly extinguished to enable the restart of the secondary AC excitation operation.

[Action]

The GTO according to the present invention suppresses the occurrence of overvoltage by short-circuiting the secondary circuit of the AESM by partially igniting when an abnormal voltage occurs, and forcibly extinguishes the GTO during energization to thereby reduce the secondary AC. Excitation operation can be restarted.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as those in FIG. 3 are denoted by the same reference numerals, and in FIG. 1, 2X is a secondary excitation device according to the present invention.
Details are shown in FIG. 2 (A). Reference numeral 8 denotes a short-circuit diode connected in series in the opposite direction to a GTO described later that generates the output voltage of the secondary exciter 2X. Reference numerals 9 and 11 denote GTOs connected in series to the positive electrode of the secondary exciter 2X. , 10 and 12 are GTOs connected in series to the negative electrode side. The short-circuit diode 8 is
These two positive-electrode GTOs 9 and 11 and the negative-electrode GTO
The intermediate points of the diodes 10 and 12 are connected to each other so that a current flows in a direction opposite to that of the GTO, and the intermediate point of the diode is commonly connected to each phase.

Next, the operation will be described. First, when an abnormal phenomenon such as short circuit or unbalanced load occurs on the primary side of AESM1,
The back electromotive force is generated on the secondary side of SM1, and appears as a large abnormal voltage. When the voltage value of the abnormal voltage becomes equal to or higher than the limit voltage of the arrester 3, the arrester 3 performs a discharging operation. Therefore, the applied voltage to the secondary excitation device 2X is limited to the limited voltage of the arrester 3. Thereafter, an overvoltage is detected by the overvoltage detection device 7, and a part of the positive and negative GTOs 9, 11, 10, and 12 is ignited according to the potential difference between the phases, and
The secondary side of AESM1 is short-circuited via TO and short-circuit diode 8. FIG. 2A shows the situation of this short circuit. This second
Figure (A), during the time t ₁ shown in FIG. 2 (B), a diode for short-circuiting the GTO circuit current to the V-phase and W-phase from the U-phase is turned ON when the flow as indicated by arrow (fill Only the element that has been turned on is turned on, and all other GTOs are turned off. When the short-circuit current flows instantaneously, the energy transferred to the secondary side is completely consumed. Thereafter, when the abnormal condition on the primary side is resolved, the GTO being energized is forcibly extinguished to shut off the fault current and restart the secondary AC excitation operation. Further, even after the transition to the secondary-side short-circuit state by the GTO, if the abnormal state on the primary side still continues, the short-circuit breaker 6 is turned on.

[Effects of the Invention] As described above, according to the present invention, a diode is connected between the intermediate points of the series GTOs on the positive electrode side and the negative electrode side that constitute the secondary excitation device, so that the secondary side is connected to the secondary side when the primary side is abnormal. GTO is forcibly extinguished after suppressing the back electromotive force (secondary overvoltage) induced, and after the abnormality is eliminated, so that the equipment can be inexpensive and the primary side abnormal phenomenon regardless of the accident situation There is an effect that the secondary AC excitation operation after the removal can be reliably restarted.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of a secondary overvoltage protection device according to one embodiment of the present invention, FIG. 2 (A) is a detailed diagram of a secondary AC excitation device, and FIG. 2 (B) is a three-phase waveform diagram. FIG. 3 is a schematic diagram showing a conventional secondary overvoltage protection device. In the figure, 2X is a secondary excitation device, 7 is an overvoltage detection device,
8 is a short-circuit diode, and 9 to 12 are GTOs. In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H02P 9/00 H02P 9/00 E

Claims (1)

(57) [Claims] 1. A secondary overvoltage protection device for an AC-excited synchronous machine for coping with a primary-side abnormality by connecting a primary side to a system and a secondary side to a secondary excitation device. Two GTOs connected in series on the positive electrode side of the excitation device for each phase;
GT for each phase connected in series to the negative pole side of the next excitation device
O, two series intermediate points of the GTO on the positive electrode side, and GT on the negative electrode side.
O, two series diodes are provided for each phase in a direction opposite to the GTO between the two series midpoints, and a short-circuit diode in which the series midpoints of the diodes are connected in common; When a back electromotive force is generated on the secondary side due to a side abnormality, an overvoltage is detected, a part of the positive side and the negative side GTO is ignited, and the secondary side is short-circuited through the GTO and a short-circuit diode, A secondary overvoltage protection device for an AC-excited synchronous machine, comprising: an overvoltage detection device that outputs a control signal for forcibly extinguishing the GTO when the abnormality is resolved.