JP6848041B2 - Overvoltage protection device for variable speed pumped storage power generation system - Google Patents

Description

An embodiment of the present invention relates to an overvoltage protection device for a variable speed pumped storage power generation system.

In the overvoltage protection device of the secondary excitation type variable speed pumping power generation system, in the case of a serious failure with a large accident current such as a three-phase short circuit failure at the point where the power generation system is connected to the power system or its immediate end, two The overvoltage is suppressed by short-circuiting the excessive voltage induced in the secondary circuit using a short circuit provided in the secondary circuit.

The AC exciter (secondary exciter) of the variable speed pumping power generation system is composed of a frequency converter, and if the operation is continued during the short circuit, damage may occur due to the short circuit current. Stops the secondary exciter.

If the short-circuited state of the secondary circuit continues, the power generation motor of the variable-speed pumping power generation system becomes a secondary short-circuited induction machine, receives exciting power from the system, and transfers a large amount of active power to and from the system. Therefore, in order to stabilize the system, it is necessary to disconnect the main circuit breaker connected to the system at an early stage and to protect and stop the variable speed pumping power generation system that has lost the excitation source due to the continuous short circuit of the secondary circuit.

However, even in such a serious accident at the nearest end, after the accident is eliminated by the system circuit breaker, it is possible to continue the operation without interrupting the main circuit breaker, which is a large-capacity power generation facility. This was an important issue in the variable speed pumped storage power generation system.

To solve such a problem, after the system accident is removed by the system circuit breaker, the short-circuited state by the short-circuiter of the secondary circuit is forcibly released by the frequency converter used as the secondary exciter. An overvoltage protection device for a variable speed pumped storage power generation system capable of restarting stable operation by a secondary exciter at an early stage and continuing operation of the main engine has been proposed (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 7-193882

However, in the conventional method, since the short circuit is composed of a thyristor having a high current withstand, it is necessary to apply a reverse voltage with a converter for secondary excitation to forcibly reduce the current of the short circuit to zero, so that the short circuit state is caused. In order to release the short circuit, it is necessary to wait until the large short circuit current including the transient DC component flowing through the short circuit becomes less than the steady current of the secondary excitation converter, and the stable normal operation state is restarted by releasing the short circuit earlier. In some cases it was necessary to implement it.

On the other hand, even if the current including the transient DC component flowing through the short-circuit is larger than the steady-state current of the secondary exciter, a reverse voltage is applied by the secondary exciter converter to cause the short-circuit state of the short-circuit, provided that the current withstand is within a short time. If you try to release it early, the large short-circuit current may flow into the secondary excitation converter, raise the DC voltage, and restart the overvoltage protection function of the overvoltage protection device. In order to release the short-circuit state quickly and stably, it is necessary to provide a converter having a large capacity that exceeds the current capacity of the secondary exciter that exceeds the capacity required for normal operation.

It is economically burdensome to spend hundreds of millions of yen or more on an overvoltage protection device that operates only a few times a year or less to secure an installation area and increase the capacity of the converter, and it is a variable speed pumped storage power plant. It could be a major obstacle to the introduction.

The present invention has been made to solve the above-mentioned problems, and even in the case of a three-phase short-circuit failure near a power plant interconnection point where the influence of a fault current is large, the short-circuit state of the circuit breaker of the secondary circuit is speeded up. A variable speed pumping power generation system that does not require disconnection from the system or stop of the main engine by the parallel circuit breaker after the accident is successfully eliminated by the system circuit breaker by canceling with and restarting the stable operation by the AC exciter. It is an object of the present invention to provide an overvoltage protection device.

According to the embodiment, the high voltage side is connected to the circuit between the rotor winding of the winding type inducer in which the stator winding is connected to the power source on the low pressure side of the transformer connected to the power system and the AC exciter. A short-circuiting device for short-circuiting the circuit when an overvoltage occurs in the circuit is provided, and the energizing current during the short-circuiting operation of the short-circuiting device is equal to or less than a predetermined current specified value and the short-circuiting operation of the short-circuiting device is performed. In the overvoltage protection device of the variable speed pumping power generation system equipped with a control device that forcibly releases the short-circuited state of the short-circuiter on condition that the elapsed time is equal to or longer than the predetermined operation duration specified value. wherein the control device, on condition that the operation duration of the overvoltage protection device is an overvoltage protector continuous operation specified time or more previously defined, have row control for disconnecting the variable-speed pumped-storage power generating system from the power system, the Overvoltage protection device Provided by the overvoltage protection device of the variable speed pumping power generation system, which defines the continuous operation specified time as a function of the sliding or sliding frequency or rotation speed before the system accident of the variable speed pumping power generation system or as a function of the active power. Will be done.

According to the present invention, even in the case of a three-phase short-circuit failure near a power plant interconnection point where the influence of a fault current is large, the short-circuit state of the circuit breaker of the secondary circuit is released at high speed, and stable operation is performed by the AC exciter. By restarting, it is possible to provide an overvoltage protection device for a variable speed pumping power generation system that does not require disconnection from the system or stoppage of the main engine by a parallel circuit breaker after the accident is successfully eliminated by the system circuit breaker.

The figure which shows an example of the structure of the variable speed pumped storage power generation system which includes the overvoltage protection device which concerns on one Embodiment. The figure which shows an example of the circuit structure of a short circuit. The figure which shows an example which made the overvoltage protection device continuous operation specified time as a function of slip. The figure which shows an example which made the overvoltage protection device continuous operation specified time as a function of active power. A time chart showing an example of the operation of the overvoltage protection device. A time chart showing another example of the operation of the overvoltage protection device.

Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a configuration of a variable speed pumped storage power generation system including an overvoltage protection device according to an embodiment.

As shown in FIG. 1, the variable speed pumped storage power generation system according to the present embodiment includes a winding type inducer 1, a frequency converter 4, a control device 5, a short circuiter 6, a main transformer 8, a parallel circuit breaker 9A, and the like. Includes an exciting transformer 16 and a current detector 11. The frequency converter 4 corresponds to an AC exciter (secondary exciter) of the winding induction machine 1, includes a self-excited converter 2 and a self-excited inverter 3, a DC link capacitor 12, a resistor 13, and a resistor 13. A chopper 15 composed of a power semiconductor element 14 is included. Here, a self-excited frequency converter is described as an example, but a separately-excited converter such as a cycloconverter may be used. The control device 5 controls the inverter 3 and the converter 2 of the frequency converter 4 so as to give a secondary exciting current corresponding to the operating state of the winding type induction machine 1 during the normal operation of the variable speed pumping power generation system, and controls the system. When an overvoltage occurs in the secondary circuit at the time of an accident, the short-circuiter 6 is immediately short-circuited, and the short-circuiter 6 is opened after the conditions described later are satisfied. The control device 5 and the short-circuit device 6 constitute an overvoltage protection device (hereinafter, may be referred to as “OVP”) of the variable speed pumped storage power generation system according to the present embodiment. The overvoltage protection device may be composed of, for example, a frequency converter 4, a short circuit 6, a control device 5, and a current detector 11, and the control thereof is an inverter output current detected by a variable speed pumping power generation system. The next circuit voltage and DC link voltage can also be used.

The main transformer 8 is connected to the stator winding terminal (primary winding terminal) of the winding type inducer 1 via a parallel circuit breaker 9A, and the voltage of the stator winding terminal of the winding type inducer 1 is adjusted. After being boosted to the voltage of the power system 10 by the main transformer 8, it is connected to the power system 10 via the system circuit breaker 9.

On the other hand, the frequency converter 4 is connected to the rotor winding terminal (secondary winding terminal) of the winding type inducer 1. The frequency converter 4 is connected to the circuit between the rotor winding terminal of the winding type inducer 1 and the main transformer 8 via an exciting transformer 16 and takes in a three-phase AC voltage.

In the frequency converter 4, the three-phase AC voltage is converted into a DC voltage by the converter 2, and the DC voltage of the DC link capacitor 12 is maintained. The DC voltage is converted into a three-phase AC voltage having a frequency corresponding to the slip frequency via the inverter 3. Further, the frequency converter 4 is combined with the resistor 13 in order to suppress an increase in the DC link voltage at the time of a system accident in which the failure current induced in the secondary winding is relatively small and to enhance the operation continuation ability of the converter 2 / inverter 3. It includes a chopper 15 composed of a power semiconductor element 14 (for example, GTO, IGBT).

The short circuit 6 is connected to a circuit between the rotor winding terminal of the winding inducer 1 and the frequency converter 4, and when an overvoltage exceeding a predetermined value occurs in the circuit or the DC link circuit, the short circuit 6 is said to be concerned. The circuit is short-circuited under the control of the control device 5. Specifically, the short-circuiter 6 is electrically connected between each line of the exciting power supply line connecting the frequency converter 4 and the rotor winding terminal of the winding type inducer 1, for example, FIG. As shown, it is configured by using a separately excited element such as a thyristor. In the example of FIG. 2, a case where one thyristor is provided between each of the U phase, the V phase, and the W phase is shown, but the present invention is not limited to this example.

The control device 5 passes through various sensors installed in various places to measure the voltage (capacitor voltage) or secondary circuit voltage of the DC link capacitor 12, the measured value of the current flowing from the frequency converter 4, and the short circuit. Acquire the measured value of the current flowing through the capacitor 6. For example, the current flowing through the short circuit 6 can be detected through the current detector 11. The control device 5 drives and controls each element constituting the short-circuiter 6, the converter 2 / the inverter 3, based on the acquired various measured values. More specifically, as shown in FIG. 2, the current detectors 11 are a plurality of current detectors 11a and 11b that detect currents flowing through short-circuit switches such as thyristors provided between the lines of the short-circuiter 6. , 11c may be configured.

In particular, the control device 5 of the present embodiment transmits the overvoltage of the secondary circuit of the winding induction machine 1 through the above-mentioned sensor in response to the occurrence of an accident in the power system 10 (for example, a short-circuit accident in the transmission line near the power plant). When it is detected, the short-circuiter 6 is short-circuited, and then the energizing current during the short-circuit operation of the short-circuiter 6 is equal to or less than the predetermined current specified value Ith, and the elapsed time of the short-circuit operation of the short-circuiter 6 is predetermined. Control to forcibly release the short-circuited state of the short-circuited device 6 by applying a reverse voltage to the thyristers constituting the short-circuited device 6 by the frequency converter 4 on condition that the specified operation duration is equal to or higher than the specified value Tth. (Hereinafter, referred to as "feature 1").

Here, the above-mentioned current specified value Ith is a value that exceeds the rated current of the frequency converter 4 as long as the frequency converter 4 does not cause any trouble such as element destruction (hereinafter, referred to as “feature 2”). ). In this way, the short-circuited state of the short-circuiter 6 can be released more quickly. In this case, the specified current value Ith is set to a value equal to or less than the maximum breaking current of the element provided in the frequency converter 4 (hereinafter referred to as “feature 3”), or is caused by an overcurrent with respect to the frequency converter 4. The level that guarantees protection is set to a value equal to or less than the preset overcurrent protection set value (hereinafter referred to as "feature 4").

On the other hand, the above-mentioned operation duration specified value Tth is set to be equal to or longer than the accident elimination time, which is the time required to eliminate the system accident of the power system 10 (hereinafter, referred to as “feature 5”). The accident elimination time at this time can be set to the maximum time until the system circuit breaker 9 that eliminates the system accident is disconnected and the accident is eliminated when the system protection relay device is operating normally. By doing so, it is possible to control the return of the short circuit device 6 after the accident has been reliably eliminated. Here, the operation duration specified value Tth may be equal to or longer than the time (shortest accident removal time) at which the removal is completed earliest in the system accident removal process of the power system 10 (hereinafter referred to as "feature 6"). .. For example, the time for actually opening the protection relay or circuit breaker until the system accident is eliminated is usually earlier than the above-mentioned longest time, and Tth can be set as the shortest accident elimination time.

Further, in order to shorten the operation duration specified value Tth, for example, the operation time that the overvoltage protection device applies to the overvoltage protection process (the overvoltage protection device detects the overvoltage of the secondary circuit and then short-circuits the short circuit 6). In consideration of the time lag required for the overvoltage protection, the operation duration specified value Tth may be set to be equal to or longer than the time obtained by subtracting the operation time required for the overvoltage protection process by the overvoltage protection device from the above-mentioned short-circuit accident elimination time (hereinafter, "" It is called "feature 7"). In this way, the forced release operation of the short-circuit state after the short-circuit operation of the short-circuit device 6 can be performed earlier after the system accident is eliminated. The reason why the forced release operation is performed earlier is that it is preferable for the stable operation of the variable speed pumped storage power generation system to restart the stable operation using the frequency converter 4 as soon as possible.

When the current specified value Ith is increased and the operation duration specified value Tth is shortened, even if the short-circuited state of the short-circuiter 6 is forcibly released by the frequency converter 4, the secondary circuit and the DC link voltage are overvoltageed again. It may occur and the short circuit 6 may restart. Therefore, in the control device 5, after the short-circuit state of the short-circuiter 6 is forcibly released by the frequency converter 4, the overvoltage protection function of the overvoltage protection device restarts within the predetermined overvoltage protection device restart specified time Tr. If this is the case, the energizing current during the short-circuit restart of the short-circuit device 6 is set to a time shorter than the specified current value Ith and the elapsed time of the short-circuit restart of the short-circuit device 6 is shorter than the specified operation duration Tth. Control is performed to forcibly release the short-circuited state of the short-circuiter 6 on the condition that the restart operation duration is Tth2 or more (hereinafter, referred to as "feature 8"). By doing so, even if the overvoltage protection function of the overvoltage protection device is restarted before the accident is eliminated, the short-circuit operation and short-circuit state of the short-circuit device 6 are within the range of the current-carrying capacity of the frequency converter 4 or the short-circuit device 6. The forced release operation of can be repeatedly performed.

Further, when the control device 5 repeats the short-circuit operation of the short-circuiter 6 and the forced release operation of the short-circuited state, the number of times and the energization time for guaranteeing the energization withstand capacity of the short-circuiter 6 or the frequency converter 4 are performed. Alternatively, it is carried out within the element temperature (hereinafter referred to as "feature 9"). By doing so, it is possible to prevent a device failure from occurring due to endless repetition.

Further, the operation duration specified value Tth may be shorter than the time required for removing the accident that is completed earliest among the system accidents of the power system 10 (shortest accident removal time) (hereinafter, "feature 10"). Called). In this case, the operation duration specified value Tth can be set to be earlier than the time when the system circuit breaker 9 is disconnected and the accident is eliminated. Since the system accident is ongoing, there is a high possibility that the short-circuit operation of the overvoltage protection device will be repeated. It is possible to drive in.

Further, the control device 5 opens the parallel circuit breaker 9A and uses the variable speed pumped storage power generation system on the condition that the operation duration of the overvoltage protection device is equal to or longer than the predetermined continuous operation specified time Tc of the overvoltage protection device. Control is performed to disconnect from the power system 10 (hereinafter, referred to as "feature 11"). By doing so, it is possible to prevent the occurrence of problems such as device failure in the variable speed pumped storage power generation system.

In this case, the overvoltage protection device continuous operation specified time Tc is, for example, the operation duration Ta that guarantees the energization withstand capacity of the short circuit device 6, or, for example, the time for the frequency or voltage system protection relay to reach the operation level. The operation duration Tb that guarantees that the variable speed pumped storage power generation system can be operated stably may be set, or the shorter of both may be used (hereinafter, referred to as “feature 12”). Further, the overvoltage protection device continuous operation specified time Tc may be a constant value, but instead, for example, it is specified as a function of the slip or slide frequency or rotation speed of the variable speed pumped storage power generation system before a system accident, or as a function of active power. It may be (hereinafter, referred to as "feature 13").

Here, an example in which the overvoltage protection device continuous operation specified time (OVP reset time) Tc is expressed as a function of slip before a system accident of the variable speed pumped storage power generation system is shown in the graph of FIG. In the graph of FIG. 3, the current flowing in the secondary circuit at the time of a system accident at the nearest end of the system during pumping operation is obtained by instantaneous value analysis such as EMTP, and when it becomes Ith or less, the frequency converter 4 is used. The maximum time when the short circuit 6 is forcibly opened by applying a reverse voltage is plotted as a function of slip and obtained. By using such a function, it is possible to immediately determine the success or failure of the operation continuation of the variable speed pumped storage power generation system by forcibly opening the short circuit device 6, and if the operation cannot be continued, the variable speed pumped storage power generation system is powered. It can be immediately separated from the system 10 to reduce the influence on the system, and stable operation of the system becomes possible.

Further, the overvoltage protection device continuous operation specified time Tc specified as a function of the slip or the slide frequency or the rotation speed is the operation duration Ta that guarantees the energization withstand capacity of the short circuiter 6, or the variable speed pumping power generation system can be operated stably. If the operation duration Tb that guarantees the above is longer than whichever is shorter, the overvoltage protection device continuous operation specified time Tc at that time may be set to the shortest time among the above operation durations Ta and Tb (hereinafter, Called "feature 14"). By doing so, it is possible to more appropriately determine whether or not the variable speed pumped storage power generation system should be separated from the power system 10 by the parallel circuit breaker 9A. Further, in this case, that is, when there is a range in which the overvoltage protection device continuous operation specified time Tc is shorter than the time specified as a function of slip or slip frequency or rotation speed or as a function of active power, the slip or A function (hereinafter referred to as "feature 15") that prescribes the operation limit range of the sliding frequency, rotation speed, or active power and excludes operation in the operation limit range, or during operation in the operation limit range. In the event of a system accident, a function to open the parallel circuit breaker 9A and immediately disconnect the variable speed pumping power generation system from the power system 10 without forcibly releasing the short circuit breaker 6 (hereinafter, "feature 16"). ) Can be provided.

Further, an example in which the overvoltage protection device continuous operation specified time (OVP reset time) Tc is expressed as a function of the operating output (active power) before the system accident of the variable speed pumped storage power generation system is shown in the graph of FIG. In the graph of FIG. 4, the current flowing in the secondary circuit at the time of a system accident at the nearest end of the system during power generation operation is obtained by instantaneous value analysis such as EMTP, and when it becomes Ith or less, the frequency converter 4 is used. The maximum time when the short circuit 6 is forcibly opened by applying a reverse voltage is plotted as a function of the operating output (active power) and obtained. By using such a function, even if there is the above-mentioned operation restriction area, while avoiding the operation in the operation restriction area, even if an accident occurs while passing through the operation restriction area, the short circuit device 6 The variable speed pumped storage power generation system can be instantly disconnected from the system without waiting for the opening of the system to reduce the impact on the system, and stable operation of the system becomes possible.

Next, the operation of the overvoltage protection device of the winding type induction machine 1 configured in this way will be described with reference to FIG. FIG. 5A is a time chart of various signals generated by the control device 5, FIG. 5B is a waveform of the voltage of the DC link circuit of the frequency converter 4, and FIG. 5C is energization of the short circuit device 6. The waveforms of the current (magnitude) are shown respectively.

As shown in FIG. 5A, when an accident occurs in the power system 10 at time T1 and an accident current flows in the primary winding of the winding induction machine 1, the secondary winding of the winding induction machine 1 also flows. The accident current is induced. When this accident current charges the DC link capacitor 12 via the inverter 3 and exceeds the capacity of the chopper 15 having sufficient voltage suppression capability in a minor system accident, the frequency converter 4 is shown in FIG. 5 (b). DC voltage rises significantly.

As shown in FIG. 5A, the control device 5 detects the overvoltage at the timing (time T2) when the DC voltage of the frequency converter 4 exceeds the specified value, operates the short circuit device 6 by the OVP gate signal, and operates the short circuit device 6. At the same time, an OVP operation continuation request signal is output to start counting the operation duration specified value Tth (for example, 60 ms). As a result, an energizing current flows through the short circuit 6 as shown in FIG. 5 (c), and the DC voltage of the frequency converter 4 drops as shown in FIG. 5 (b).

After that, when the system protection relay system operates, the system circuit breaker 9 in the power system 10 opens, and when the elimination of the system accident is completed at time T0, the system voltage returns to near the rated voltage and the fault current once. Although it becomes smaller, it increases rapidly thereafter if the short circuit breaker 6 is kept short-circuited.

Next, in the control device 5, the operation duration specified value Tth shown in FIG. 5 (a) has elapsed, and the energization current during the short-circuit operation of the short-circuit device 6 shown in FIG. 5 (c) is specified in advance. At the timing (time T3) when the value becomes Ith or less, a command to restart the frequency converter 4 is issued by the OVP reset control signal, and the current flowing in each phase of the short circuit 6 is observed by the current detector 11 to generate a current. By acquiring information on the polarity of the frequency converter 4 and appropriately determining the arm to ignite the frequency converter 4, a DC voltage is applied in the direction of canceling the current, and the current energized in the short circuit 6 is instantly reduced to zero. As a result, the short-circuit state of the short-circuit device 6 is released, and the release of the short-circuit state of the short-circuit device 6 is completed at time T4. As a result, as shown in FIG. 5C, the energizing current does not flow through the short circuiter 6, and as shown in FIG. 5B, the DC voltage of the frequency converter 4 drops for a moment and then returns to a steady value.

By setting the frequency converter 4 to normal operation when the short-circuit state is normally released, an AC voltage having a frequency equivalent to the slip frequency is output from the frequency converter 4 as before the accident, and the accident point is eliminated. At that point, the variable speed pumping power generation system is returned to the normal operating state.

The above-mentioned features 1 to 4 show the features related to the setting of Ith of the overvoltage protection device operating in this way, and short-circuit by increasing the set value which is the maximum current during normal operation in the prior art. There is an effect that the ability to release the vessel 6 from the short-circuited state can be improved. Further, the above-mentioned features 5 to 7 show the features related to the setting of Tth, and improve the ability to release the short-circuit device from the short-circuit state by accelerating the release of the short-circuit device 6 from the short-circuit state. It has the effect of being able to.

Next, the operation when the short-circuit operation of the short-circuit device 6 and the forced release operation of the short-circuit state are repeatedly performed will be described with reference to FIG. FIG. 6A is a time chart of various signals generated by the control device 5, FIG. 6B is a waveform of the voltage of the DC link circuit of the frequency converter 4, and FIG. 6C is energization of the short circuit device 6. The waveforms of the current (magnitude) are shown respectively.

The operation from time T1 to T4 shown in FIG. 6A is the same as that in FIG. 5A. However, coupled with the fact that Ith was made larger and Tth was made shorter, the effect of the transient direct current after the short-circuit state was released was large, and the frequency converter 4 resumed normal operation in the processing after the timing T4. Later, the rise of the DC voltage cannot be completely suppressed, and as shown in FIG. 6 (b), an overvoltage may occur at time T5, and as shown in FIG. 6 (c), the short circuit 6 may restart and the energizing current may flow again. .. In this case as well, since the AC component of the approximate system frequency exists in the secondary current, it may become Ith or less again in the next cycle, and if the timing (time T6) can be captured, the converter 4 will be used again. By applying a reverse voltage to the short circuit 6 to forcibly reduce the energizing current to zero, the short circuit state can be released at time T7, and then the normal operation can be restarted by the converter 4.

Since the restart of the short circuit device 6 is not due to a large fault current due to a system accident, it is not necessary to wait for the same time as the first operation as Tth for restarting the operation, but the restart of the short circuit device 6 is performed. Occasionally, it should be done after the time or more that the element of the frequency converter 4 that has been temporarily stopped due to the occurrence of overvoltage or overcurrent can be safely restarted.

As an example, the first Tth from T2 to T3 is set to 50 ms in consideration of the operation guarantee time of the system circuit breaker 9, and the specified value Tth2 at the time of the second restart from T5 to T6 is set to 5 ms.

The specified value Tth2 for the duration during restart is not the time when the large fault current induced in the case of a system accident becomes sufficiently small due to the elimination of the accident or the attenuation of the transient DC component. If the short circuit is forcibly released, it is quite possible that an overvoltage will occur again. Therefore, the period for adopting this time should be limited to the necessary and sufficient period. In the above example, the overvoltage protection device restart specified time Tr, which is this period, is set to 30 ms or less as a period equal to or less than a period in which a margin is added as necessary to one cycle of the general system frequency component included in the secondary current. In this case, after the short-circuiting device 6 is operated again, the control device 5 has elapsed the re-operation duration specified value Tth2, which is shorter than the above-mentioned operation duration specified value Tth, and the short-circuiting operation of the short-circuiting device 6 has elapsed. By issuing a command to restart the frequency converter 4 at the timing T6 when the energizing current inside becomes equal to or less than the predetermined current specified value, and further observing the current flowing in each phase of the short circuit 6 with the current detector 11. By acquiring information on the polarity of the current and appropriately determining the arm to ignite the frequency converter 4, a DC voltage is applied in the direction of canceling the current, and the current energized in the short circuit 6 is instantly reduced to zero. By doing so, the short-circuit state is released.

By setting the frequency converter 4 to normal operation at the timing (time T7) when the short-circuit state is normally released, an AC voltage having a frequency equivalent to the slip frequency is output from the frequency converter 4 as before the accident, resulting in an accident. When the points are removed, the variable speed pumping power generation system is returned to the normal operating state.

The above-mentioned features 8 and 9 show the characteristics of control when the short-circuiter 6 restarts in this way, and the short-circuiting of the short-circuiter 6 is accelerated as in the above-mentioned features 1 to 7. Even if the short circuit 6 is restarted due to this, the short circuit is released again within about one cycle of the system frequency after that, and the operation can be continued. Therefore, Ith used in the control including the features 1 to 7. Can be selected to be larger and Tth to be shorter.

Further, if the above-mentioned re-operation occurs continuously a plurality of times, the temperature of the short-circuiter 6 and the converter 4 composed of semiconductor elements may rise, resulting in malfunction or damage. It is also possible to limit the number of repetitions within a predetermined time, the energization time, or the element temperature within a predetermined time that can guarantee the energization withstand capacity.

According to the above-mentioned features 8 and 9, since the short-circuiting device 6 can be safely operated and released at high speed within the withstand capacity of the overvoltage protection device, the short-circuiting device 6 may be restarted. Even during a system failure with a high frequency, once the secondary circuit current falls below Ith, the short circuit device 6 is forcibly released, and the possibility that normal operation can be resumed earlier can be increased. For example, according to the above-mentioned feature 10, the operation duration specified value Tth at the time of the occurrence of a system failure can be shortened without limiting after the system accident is removed, and the forced release operation during the continuation of the system accident can be performed.

In the above-described operation, the control device 5 detects if the short circuit cannot be released within a predetermined time according to the slip with respect to the power supply voltage from the short-circuited state of the circuit breaker 6, and affects the power system 10. In order to avoid adverse effects, the parallel circuit breaker 9A can be opened to disconnect the variable speed pumping power generation system from the power system 10. Further, whether the control device 5 avoids operation by setting a predetermined slip range (operating range) as an operation prohibition zone, which may not be able to recover even after the overvoltage protection device continuous operation specified time Tc has elapsed. Alternatively, it can be controlled to pass at high speed within a predetermined time. Although the overvoltage protection device continuous operation specified time Tc is not shown in FIGS. 5 and 6, the above state is when the Tc is earlier than the reset completion timing in the figure, and the operating state is shown in FIG. An example of an operating range is shown in which control is performed to avoid the situation or to pass the vehicle at a high speed within a predetermined time.

In this way, by appropriately determining the operation method according to various operating conditions, the power system 10 may be adversely affected from the viewpoint of protecting the secondary winding of the winding type inducer 1 and the frequency converter 4. It is possible to operate safely from the ground, and it is possible to recover in a short time without leading to a prolonged short-circuit state. Such an effect can also be obtained from, for example, the above-mentioned features 11 to 16.

As described in detail above, according to the above-described embodiment, the short-circuit state of the circuit breaker of the secondary circuit is released at high speed even at the time of a three-phase short-circuit failure near the power plant interconnection point where the influence of the failure current is large. By resuming stable operation with the AC exciter, the overvoltage of the variable speed pumping power generation system that does not require disconnection from the system or stop of the main engine by the parallel circuit breaker after the accident elimination by the system circuit breaker is successful. A protective device can be provided.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Winding induction machine, 2 ... Self-excited converter, 3 ... Self-excited inverter, 4 ... Frequency converter, 5 ... Control device, 6 ... Short circuit breaker, 8 ... Main transformer, 9 ... System circuit breaker, 9A ... Parallel Circuit breaker, 10 ... Power system, 11 ... Current detector, 12 ... DC link capacitor, 13 ... Resistor, 14 ... Power semiconductor element, 15 ... Chopper, 16 ... Excitation transformer.

Claims (4)

The high-voltage side is connected to the power system. The low-voltage side of the transformer is connected to the power supply on the low-voltage side, and the stator winding is connected to the power supply. A short-circuiting device that short-circuits the circuit when it occurs is provided, the energizing current during the short-circuiting operation of the short-circuiting device is equal to or less than a predetermined current specified value, and the elapsed time of the short-circuiting operation of the short-circuiting device is specified in advance. In the overvoltage protection device of the variable speed pumping power generation system provided with a control device that forcibly releases the short-circuited state of the short-circuited device on condition that the operation duration is equal to or more than the specified value.
Wherein the control device, on condition that the operation duration of the overvoltage protection device is an overvoltage protector continuous operation specified time or more previously defined, have row control for disconnecting the variable-speed pumped-storage power generating system from the power system,
An overvoltage protection device for a variable speed pumped storage power generation system in which the specified continuous operation time of the overvoltage protection device is defined as a function of slip or slide frequency or rotation speed before a system accident of the variable speed pumped storage power generation system or as a function of active power . In the overvoltage protection device of the variable speed pumped storage power generation system according to claim 1.
The overvoltage protection device continuous operation specified time specified as a function of the slip or slide frequency or rotation speed or as a function of the active power is the operation duration that guarantees the energization withstand capacity of the short circuit or the variable speed pumped storage power generation system is stable. If the operation duration that guarantees that the system can be operated exceeds the shorter of them, the overvoltage of the variable speed pumped storage power generation system is set to the shortest of these, the specified continuous operation time of the overvoltage protection device at that time. Protective device. In the overvoltage protection device of the variable speed pumped storage power generation system according to claim 2.
If there is a range in which the specified time for continuous operation of the overvoltage protection device is shorter than the time specified as a function of the slip or slide frequency or rotation speed or as a function of active power, the slip or slide frequency or rotation speed or active power defines the operation limit zone in advance, performs control to pass to exclude or the operation restricted zone operation at the operation limit zone within a predetermined time, the overvoltage protection device of the variable speed pumped-storage power generation system. In the overvoltage protection device of the variable speed pumped storage power generation system according to claim 2 or 3.
If a system accident occurs during operation within the range where the specified time for continuous operation of the overvoltage protection device is shorter than the time specified as a function of the slip or slide frequency or rotation speed or as a function of active power, the short circuit is forced. An overvoltage protection device for a variable-speed pumped-storage power generation system that controls the variable-speed pumped-storage power generation system to be immediately disconnected from the power system without performing specific release control.

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