JP7181760B2 - Protection control device for AC/DC converter station, protection control system for DC power transmission system, and protection control method for AC/DC converter station - Google Patents

Description

The present invention relates to a protection control device for an AC/DC converter station, a protection control system for a DC power transmission system, and a protection control for an AC/DC converter station that interconnects a power generation system such as a renewable energy power supply via a power converter and a DC line. Regarding the method.

DC power transmission systems are used for long-distance power transmission and for improving the efficiency of submarine power transmission. Since a general electric power system is an AC system, in a DC power transmission system, the power of the AC system is converted to DC by an AC/DC converter and transmitted.

In the past, DC power transmission systems were mainly one-to-one power transmission systems in which two AC/DC converters were connected by DC power transmission. As a form of a suitable DC power transmission system, a multi-terminal DC power transmission system composed of AC/DC converters at three or more locations is being developed.

As a form of operation of the multi-terminal DC transmission system, multiple wind turbines are constructed offshore to form a wind farm, the generated power is collected at an offshore substation, and the multi-terminal DC transmission system is used to transmit power to multiple onshore grids. An offshore wind farm interconnection multi-terminal DC power transmission system is attracting attention.

One of the problems in the operation of a multi-terminal DC power transmission system is protection against system faults such as ground faults or short circuits in AC systems and DC lines.

Regarding faults in the AC system, regarding fault detection and protection in the event of a ground fault in the AC transmission line, faulty lines are detected by protective relays, and faulty lines are opened, cleared, and reclosed by AC circuit breakers. techniques are already in common use. In the case of the high-speed reclosing method, the fault detection and protection of the AC system is about 3 to 5 cycles of the commercial frequency, and the time is about 50 to 100 milliseconds, and the fault detection and fault line opening are completed. Then, the reclosing can be completed in about one second after the occurrence of the accident.

On the other hand, when looking at faults in DC lines, multi-terminal DC power transmission systems in particular are configured using AC/DC converters that use semiconductor devices. Detection and fault point isolation should occur within milliseconds of fault occurrence.

Regarding this point, Patent Document 1 describes "a power converter incorporating a current detector connected to each terminal of a DC power transmission network, an AC current circuit breaker connected to the AC side of the power converter, and the DC power transmission A DC transmission system comprising a DC current circuit breaker and a current detector connected to a node of a network, and a DC transmission line connecting the power converter and the node, in the event of a grid fault, It proposes a highly reliable DC power transmission system that realizes high-speed resumption of power flow control operation or continuation of power flow control operation at the healthy end at low cost.

JP 2018-46642 A

In recent years, as a method of disconnecting faulty lines in the event of a ground fault on a DC line, technological development has been progressing toward the practical use of DC circuit breakers. The length of a DC line can be 100 km or more, and due to the severe time constraints including communication delays, it can be said that the technical barriers are high compared to fault detection and protection in AC systems.

Regarding the configuration of the DC line, Patent Document 1 describes a configuration in which the DC power transmission network has a branch point like a Y-shape, but the configuration of the DC power transmission network does not always have a branch point. do not have. For example, in the case of a four-terminal DC power transmission system, a loop configuration in which a power converter is located at each vertex of a square and a power transmission network is configured to draw a square does not have a branch point. Moreover, the power converter is not necessarily connected to only one DC line, and the output of the power converter may be branched to a plurality of DC lines for transmission.

Assuming that the configuration of the DC power transmission network is diverse in this way, especially in the case of configuring a multi-terminal DC power transmission system, a ground fault that occurs in any of the complex DC power transmission networks will cause the DC line to be cut off. In addition, it is necessary to avoid a situation that spreads to other DC lines.

In view of the above, the present invention provides an AC/DC converter station, a protection control device for an AC/DC converter station that can reliably protect a DC line within an appropriate range in the event of an accident in a DC power transmission system, a protection control system for a DC power transmission system, and an AC/DC converter. The purpose is to provide a protection control method for the place.

From the above, in the present invention, "one end of an AC/DC converter that mutually converts AC and DC is connected to an AC power transmission system, and the other end is connected to one or more DC lines via a DC circuit breaker. A protection control device for an AC/DC converter station, in which interconnected AC/DC converter stations are connected to each other to form a DC power transmission system, wherein the protection control device controls one or more DC lines connected to the AC/DC converter station. It is characterized by judging the fault in each, opening the DC circuit breaker of the DC line that detected the fault earliest , and preventing the opening of the DC circuit breaker of the DC line other than the DC line that detected the fault earliest. A protection control device for an AC/DC converter station that

Further, in the present invention, "one end of an AC/DC converter for mutually converting AC and DC is connected to an AC transmission system, and the other end is connected to one or more DC lines via a DC circuit breaker. A protection and control system for a DC transmission system in which AC/DC converter stations are connected to each other , and each AC/DC converter station is equipped with a protection control device for the AC/DC converter station. and

Further, in the present invention, "one end of an AC/DC converter for mutually converting AC and DC is connected to an AC transmission system, and the other end is connected to one or more DC lines via a DC circuit breaker. AC /DC converter stations are connected to each other to form a DC power transmission system, wherein a fault is determined in each of one or more DC lines connected to the AC/DC converter station, and the most A protection control method for an AC/DC converter station characterized by opening a DC circuit breaker of one DC line on which a fault is detected early and preventing opening of DC circuit breakers of DC lines other than the one DC line on which a fault is detected earliest. ”.

According to the present invention, when a ground fault or short-circuit fault occurs in a DC line, only information measurable at the AC/DC converter station is used to detect the DC fault, identify the faulty line, and open the DC circuit breakers at both ends of the faulty line. , the spread of accidents to the entire system can be suppressed as much as possible.

The figure which shows the structural example of the multi-terminal DC transmission system which concerns on the Example of this invention. The figure which shows the structural example of the DC circuit breaker DCCB which concerns on the Example of this invention. FIG. 3 is a diagram showing a protective operation sequence of an AC/DC converter station according to an embodiment of the present invention; The figure which shows the structural example of the DC circuit breaker control part 203 in the Example of this invention. The figure which shows that the direct current|flow fault generate|occur|produced in the fault point F1 in direct current line Ld3. The figure which shows the electric current path|route from AC-DC converter CONA when a DC fault occurs in fault point F1 in DC line Ld3. The figure which shows the electric current path|route from AC/DC converter CONB, when a DC fault occurs in fault point F1 in DC line Ld3. The figure which shows the electric current path|route from AC/DC converter CONC when a direct-current fault generate|occur|produces in fault point F1 in direct-current line Ld3.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The following examples show one embodiment of the present invention, and the present invention includes other embodiments as long as they do not deviate from the gist of the invention. Also, in the following description, unless otherwise specified, "AC" refers to three-phase AC. Furthermore, in the explanation below, the notation of opening and closing the DC circuit breaker is used. Opening refers to electrically disconnecting both ends of the DC circuit breaker, and closing refers to electrically disconnecting both ends of the DC circuit breaker. means to connect.

In Embodiment 1 of the present invention, a multi-terminal DC transmission system will be described as an object to be protected. As an example of this, a three-terminal DC transmission system will be illustrated in FIG. 1 and described. Here, when a ground fault occurs in a DC line in a three-terminal DC power transmission system, only the information measurable at the AC/DC converter station, which is an electrical station, is used to detect the DC fault, identify the faulty line, and identify the faulty line. A series of operations for opening the DC circuit breaker and restarting the operation of the DC power transmission system will be described.

FIG. 1 shows an example in which an AC/DC converter station, which is an electrical station, has configured a three-terminal DC power transmission system with terminals TA, TB, and TC. The AC/DC converter stations TA, TB, and TC of each terminal are connected at one end to the AC system G via the AC transmission line La, and at the other end to the DC line Ld.

The AC/DC conversion stations TA, TB, and TC of each terminal perform AC/DC conversion in an AC/DC converter CON arranged between the AC transmission line La and the DC bus line Bus, and connect the DC bus line Bus to the DC line Ld. A DC circuit breaker DCCB and a DC reactor DCL are connected in series to each DC line Ld.

In FIG. 1 and subsequent figures, A, B, and C attached to each of the above symbols indicate to which terminal of AC/DC conversion stations TA, TB, and TC the equipment with this symbol belongs. In addition, the numerical value attached to each symbol is used to distinguish between multiple devices. Therefore, the symbols and numerical values of A, B, and C are omitted when there is no need to distinguish between each terminal, or when there is no need to distinguish between multiple devices. and

As is clear from FIG. 1, the three AC systems GA, GB, and GC in FIG. 1 are connected to AC/DC converter stations TA, TB, and TC via AC transmission lines LaA, LaB, and LaC, respectively.

Of these, AC/DC converter station TA is connected to AC/DC converter station TB via DC line Ld1, and to AC/DC converter station TC via DC lines Ld2 and Ld3. As a result, the AC/DC converter station TA transmits power through three DC lines. The AC/DC converter station TB carries out power transmission through a single DC line, and the AC/DC converter station TC carries out power transmission through a two-circuit DC line.

In the present invention, the AC/DC conversion station, which is an electrical station configured to transmit power through a plurality of DC lines Ld, from the output of the power converter CON, that is, the AC/DC conversion station, which is an electrical station performing DC power transmission with a multi-circuit configuration. place is subject to control. In this sense, the DC power transmission system protection control device of the present invention is intended to protect the AC/DC converter stations TA and TC. The AC/DC converter station TB, which transmits power through a single DC line, is protected according to the existing concept, but the protection device of the present invention can be applied as it is.

In the equipment of FIG. 1, the AC/DC converter CON is composed of a self arc-extinguishing element and a capacitor. This configuration is called an excitation type AC/DC converter, and for example, a two-level converter or a modular multi-level converter can be applied.

In FIG. 1, the DC circuit breaker DCCB is described as having a DC line protection function including a measurement unit and a protection control unit in addition to the breaking unit, but it is not necessarily configured as a device attached to the DC circuit breaker DCCB. Needless to say, it is sufficient that each line is installed near each line.

Here, the measurement unit in the DC line protection function measures the physical quantity of the power system for determining the occurrence of an accident. DC line side voltage of the reactor DCL). Based on the current and voltage of each line, the protection control unit is composed of an overcurrent relay or an undervoltage relay that determines an accident based on the amount of change or the time rate of change exceeding a predetermined threshold value. The breaker opens the DC line according to the determination result of the line protection controller.

Further, although not shown in FIG. 1, the DC line Ld may be partially grounded. In addition, the DC line Ld may be installed on the seabed or on an overhead wire on land. In order to protect the DC line Ld, it is preferable to distinguish between the submarine installation and the overhead wire installation, in particular, whether or not the reclosing process can be executed. In the case of installation on the seabed, it is appropriate to define a ground fault as a permanent accident, so reclosing processing should not be executed, and reclosing processing should be executed only in the case of overhead line installation.

In FIG. 1, each protection control unit monitors the operating state of all the DC circuit breakers DCCB connected to the DC bus Bus in the AC/DC converter station, and when an abnormality is detected in the DC line Ld, the converter station central protection device Function to transmit the open state of the DC circuit breaker DCCB in the self-protection device to C, receive the command to open the DC circuit breaker DCCB in the self-protection device from the conversion station central protection device C, and open or close the DC circuit breaker DCCB have

As a result, each DC circuit breaker DCCB transmits the state of its own protection control unit and breaking unit to the conversion station central protection device C, and the breaking unit operates according to a command from the conversion station central protection device C to break the DC. Open or turn on the device DCCB. As a result, the converter station central protection device C controls the opening of only one DC circuit breaker DCCB among the plurality of DC circuit breakers DCCB connected to the plurality of lines, and the other DC circuit breakers DCCB are controlled to open. definitely prevent.

1, the current flowing from the DC circuit breaker DCCBA1 toward the DC line Ld1 in the AC/DC converter station TA is denoted as IA, and the current flowing from the DC circuit breaker DCCBA2 toward the DC line Ld2 is denoted as IB. , and the current flowing from the DC circuit breaker DCCBA3 toward the DC line Ld3 is denoted as IC.

Each device in AC/DC converter stations TA, TB, and TC is installed in one AC/DC converter station, and since the communication distance is short, it is possible to communicate with each other in real time within one converter station. be.

In FIG. 1, the DC bus Bus is connected to one end of the DC reactor DCL, the other end of the DC reactor DCL is connected to one end of the DC circuit breaker DCCB, and the other end of the DC circuit breaker DCCB is connected to the DC line Ld. The DC bus line Bus is connected to one end of the DC circuit breaker DCCB, the other end of the DC circuit breaker DCCB is connected to one end of the DC reactor DCL, and the other end of the DC reactor DCL is connected to It may be configured to be connected to the DC line Ld.

Next, a configuration example of the DC circuit breaker DCCB will be described with reference to FIG. The DC circuit breaker DCCB is composed of a DC circuit breaker 201 that is a circuit breaker, a current sensor 202 that is a measurement unit, and a DC circuit breaker controller 203 that is a protection controller. It should be noted that around the DC circuit breaker DCCB in FIG. 2, only the devices necessary for explaining the present invention are illustrated, and there are also harmonic filters, voltage sensors, disconnecting switches, lightning arresters, etc. of the present invention. Other devices may be included without departing from the scope.

Here, the DC circuit breaker 201 has a function of opening or closing its own circuit breaker based on an operation command from the DC circuit breaker control unit 203 . The current sensor 202 measures the current flowing through the self-current sensor, but may be a voltage sensor.

The DC circuit breaker control unit 203 has a function of determining whether or not an accident has occurred in the self-DC line Ld based on the current detection value of the current sensor 202, and provides the operating state of the DC circuit breaker to the conversion station central protection device C. a function to transmit a request for permission to open the self-DC line protection device to the converter station central protective device C when it is determined that a DC accident has occurred; It has a function to open or close the DC circuit breaker in the self-DC line protection device based on the command to open or close the DC circuit breaker.

Next, a protection operation sequence at the time of a DC fault will be described with reference to FIGS. 1 to 4. FIG. In the embodiment of the present invention, the three AC/DC converter stations TA, TB, TC in FIG. 1 independently carry out DC fault elimination and protection operations. In the following description, the protection operation sequence at the time of a DC fault will be described using the protection operation sequence of the AC/DC converter station TA as an example.

FIG. 3 shows a series of protective operation sequences in the AC/DC converter station TA, including an accident occurrence processing step S301, a DC line Ld1 accident determination processing step S302A, a DC line Ld2 accident determination processing step S302B, a DC line Ld3 accident determination processing step S302C, It consists of a circuit breaker opening judgment processing step S303, an accident removal confirmation processing step S304, a circuit breaker reclosing processing step S305, a circuit breaker opening inhibition state release processing step S306, and a completion processing step S307.

Accident occurrence processing step S301 indicates that a DC accident has occurred.

In the DC line Ld1 accident determination processing step S302A, the DC circuit breaker control unit 203 of the DC circuit breaker DCCBA1 in the AC/DC converter station TA determines whether a DC accident has occurred on the DC line Ld1. In the DC line Ld2 accident determination processing step S302B, the DC circuit breaker control unit 203 of the DC circuit breaker DCCBA2 in the AC/DC converter station TA determines whether a DC accident has occurred on the DC line Ld2. In the DC line Ld3 accident determination processing step S302C, the DC circuit breaker control unit 203 of the DC circuit breaker DCCBA3 in the AC/DC converter station TA determines whether a DC accident has occurred on the DC line Ld3.

The DC line Ld1 accident determination processing step S302A, the DC line Ld2 accident determination processing step S302B, and the DC line Ld3 accident determination processing step S302C basically use the same determination method to determine whether a DC accident has occurred.

The DC line Ld3 accident determination processing step S302C will be described below as an example.

In the DC line Ld3 accident determination processing step S302C, when it is determined that a ground fault has occurred based on the information of the current IC detected by the DC circuit breaker DCCBA3, the conversion station central protection device C self-interrupts. send a device release request.

As a criterion for determining a ground fault, for example, there is a method of determining an accident when the time rate of change of the ground fault current IC exceeds a predetermined threshold value dIth.

FIG. 4 shows a configuration example of the DC circuit breaker control section 203 in the embodiment of the present invention, for example, the configuration example of the DC circuit breaker control section 203 of the DC circuit breaker DCCBA3. The DC breaker control section 203 is composed of an adder 401 , a differentiator 402 and a threshold decision 403 .

Regarding the symbols in FIG. 4, Imeas is the DC current value detected by the DC circuit breaker DCCBA3, I ^* is the planned value of the DC current flowing through the DC circuit breaker DCCBA1, and If is the DC current flowing through the DC circuit breaker DCCBA3. dIf/dt is the rate of change of If over time, and dIth is the determination threshold value for determining a DC current fault. . As a result, an event in which the direct current increases rapidly is grasped and determined as an accident.

In addition, as the operation principle of accident detection in the DC circuit breaker control unit 203, the variation of the ground fault current IC may be evaluated. Also, the voltage drop of the line voltage may be evaluated in terms of the rate of change over time or the amount of change.

The above is the description of FIG. The conversion station central protective device C in the AC/DC converter TB and the AC/DC converter TC is the same as that shown in FIG.

In the following description, of the DC current flowing through the DC circuit breaker DCCB, the current component flowing due to a ground fault in the DC line is referred to as a fault current flowing through the DC circuit breaker DCCB.

The above is the description of the operation of the DC line Ld3 accident determination processing step S302C. Based on the current information, a similar judgment and a request to open the own circuit breaker are sent to the central protection device C.

In the circuit breaker open determination processing step S303 of FIG. 3, which is the processing in the central protection device C, it is transmitted from the DC line Ld1 accident determination processing step S302A, the DC line Ld2 accident determination processing step S302B, and the DC line Ld3 accident determination processing step S302C. The circuit breaker to be opened is selected based on the opening request command of each circuit breaker, and the opening command is sent to the corresponding DC circuit breaker DCCB.

In the embodiment of the present invention, among one or more DC circuit breakers DCCB provided in one AC/DC converter station, only the DC circuit breaker that detected the DC fault earliest is opened. As a result, in the AC/DC converter station TA with a three-line configuration or the AC/DC converter station TC with a two-line configuration, only the DC circuit breaker DCCB that has detected a DC fault the earliest is opened to prevent the opening of the other DC circuit breakers DCCB. . In addition, in the AC/DC converter station TB having a single line configuration, the corresponding DC circuit breaker DCCB is opened as it is.

In the present invention, when one DC circuit breaker DCCB is opened due to the occurrence of an accident, the opening of the other DC circuit breakers DCCB is prevented. For this reason, in the following description, the state in which all one or more DC circuit breakers DCCB provided in the AC/DC converter station are closed will be referred to as a "circuit breaker open permission state", and even if only one DC circuit breaker DCCB The open state is referred to as "breaker open prohibition state".

Note that the state in which one or more DC circuit breakers DCCB provided in the AC/DC converter station are all closed means the state in which all the DC circuit breakers that were closed immediately before the occurrence of the DC accident are in a closed state. However, the DC circuit breaker DCCB, which is opened systematically for purposes such as switching of the power transmission path of the DC power transmission system and maintenance, is not subject to the discrimination between the circuit breaker opening permission state and the circuit breaker opening prohibition state.

Therefore, for example, when the three DC circuit breakers DCCBA1, DCCBA2, and DCCBA3 in the AC/DC converter station TA are all closed, the central protection device C recognizes that the circuit breakers are permitted to open. When the DC circuit breaker control unit 203 detects a DC accident and sends a request to open the DC circuit breaker DCCBA3, the central protection device C is currently in the circuit breaker opening permission state, so immediately opens the DC circuit breaker DCCBA3. Allow open requests. At the same time, since one DC circuit breaker DCCB is in an open state, the central protection device C recognizes the current state as a circuit breaker open prohibition state, and thereafter transmits opening requests from the other DC circuit breakers DCCBA1 and DCCBA2. does not allow this release request even if

As a result, after the accident occurs, the AC/DC converter station TA with a three-line configuration will be operated with two lines, and the AC/DC converter station TC with a two-line configuration will be operated with one line. AC/DC converter station TB will be out of operation thereafter.

Returning to FIG. 3, in fault removal confirmation processing step S304, it is determined that the DC fault has been removed as a result of the DC circuit breaker opening processing in circuit breaker opening command processing step S303. Specifically, in the processing of the fault removal confirmation processing step S304, for example, it is preferable to monitor the entire DC power transmission system. A DC power transmission system overall control device (not shown) monitors the state of each DC line Ld and determines whether to remove the fault based on the information on the current and voltage of the DC line.

In the circuit breaker reclosing process step S305, in order to restore the configuration of the DC power transmission system to the state before the occurrence of the ground fault, a closing command is given to the DC circuit breaker opened in the circuit breaker open determination process step S303. Execute the process. In addition, when a permanent fault is assumed in advance in the DC line fault (such as in the case of submarine power transmission), or when reclosing is unnecessary for the operation of the DC power transmission system, the circuit breaker reclosing processing step S305 is unnecessary. is.

In the step S306 of canceling the breaker-opening prohibition state, the breaker-opening prohibition state is canceled when there is an AC/DC converter station in which the breaker-opening prohibition state exists in the DC power transmission system. As a result, the central protection device C recognizes that the current state has returned to the circuit breaker opening permission state.

After the circuit breaker opening prohibition state release processing step S306, the series of sequences in FIG. 3 is completed in a completion processing step S307. The above is the protection operation sequence of the AC/DC converter station TA in the first embodiment of the present invention. The same protective operation sequence is applied to AC/DC converter station TB and AC/DC converter station TC.

Next, the fault current when the DC fault F1 occurs in the DC power transmission system of FIG. 1 will be described with reference to FIGS. 6 to 8. FIG. The configuration and equipment arrangement of the DC power transmission system are the same as in FIG. 1, and it is assumed that a ground fault F1 has occurred in the DC line Ld3.

FIG. 5 illustrates a case where a DC fault occurs at fault point F1 in DC line Ld3. 6 to 8 classify the fault current flowing through the AC/DC converter station TA into three components I0, I1, and I2 when a DC fault occurs at the fault point F1 of the DC line Ld3, and each current The route is illustrated.

I0 in FIG. 6 is the fault current that flows from the AC/DC converter CONA of the AC/DC converter station TA through the bus BusA, the DC reactor DCLA3 connected to the DC line Ld3, and the DC circuit breaker DCCBA3 toward the fault point F1. be.

I1 in FIG. 7 is from the AC/DC converter CONB of the AC/DC converter station TB to the bus line BusB, the DC reactor DCLB1, the DC circuit breaker DCCBB1, the DC line Ld1, the DC circuit breaker DCCBA1, the DC reactor DCLA1, and the bus line BusA of the AC/DC converter station TA. , the DC reactor DCLA3 connected to the DC line Ld3 and the DC circuit breaker DCCBA3 toward the fault point F1.

I2 in FIG. 8 is from the AC/DC converter CONC of the AC/DC converter station TC to the bus line BusC, the DC reactor DCLC1, the DC circuit breaker DCCBC1, the DC line Ld2, the DC circuit breaker DCCBA2, the DC reactor DCLA2, and the bus line BusA of the AC/DC converter station TA. , the DC reactor DCLA3 connected to the DC line Ld3 and the DC circuit breaker DCCBA3 toward the fault point F1.

Comparing the current paths of the fault current I0 and the fault currents I1 and I2, the fault current I0 is the current that passes through one DC circuit breaker DCCB, whereas the fault currents I1 and I2 are the DC line and the three DC circuit breakers. is the current through DCCB.

As described above, when a DC fault occurs, the fault current flowing through a certain AC/DC converter station is transferred from the AC/DC converter station connected to the DC line where the DC fault occurred to one DC line protection line, such as I0. One or more DC lines and 3 There are two types of fault current Ify that flow through one or more DC line protection devices to the fault point. The fault current Ifx is called the direct fault current, and the fault current Ify is called the wraparound fault current.

Since the DC line Ld has a DC reactor DCCL, the current path of the direct fault current Ifx has only one DC reactor, whereas the current path of the intrusion fault current Ify has at least three DC reactors. is a circuit connected in series.

Further, in the case of FIG. 4, the direct fault current Ifx flows only to the AC/DC converter stations TA and TC connected to both ends of the DC line Ld3 where the DC fault occurred.

As the number of DC reactors DCCL included in the current path increases, the time rate of change of the fault current becomes smaller due to the inductance of the DC reactor DCCL. , it can be said that the direct fault current Ifx is larger. In addition, it can be said that the direct fault current Ifx is larger in terms of the magnitude and variation of the fault current.

As described above, when a DC fault occurs, the fault current flowing through an AC/DC converter station is such that both the direct fault current Ifx and the loop fault current Ify flow in the same direction, as in the IC in FIG. 1, and a fault current in which only the wraparound fault current Ify flows like IA and IB in FIG.

Comparing the direct fault current Ifx and the sneak fault current Ify with IA, IB, and IC in FIG. , both the direct fault current Ifx and the detour fault current Ify flow in the same direction.

In other words, it can be said that IC is the largest when the time rate of change of IA, IB, and IC is compared when a DC fault occurs. In addition, it can be said that the IC has the largest magnitude and change in the fault current.

The magnitudes of the direct fault current Ifx and the detour fault current Ify are determined by the inductance of the DC reactor DCL, the impedance of the DC line, and the fault point, and can be evaluated in advance by off-line analysis or the like.

For example, the inductance of the DC reactor DCL is set such that the time rate of change dIfx/dt of the direct fault current Ifx is greater than a predetermined dIth, and the time rate of change dIfy/dt of Ify is less than a predetermined dIth. , it is possible to identify the fault line at the DC fault based on the difference in the rate of change with time between the direct fault current Ifx and the detour fault current Ify.

These facts mean that the line fault detection that directly detects the fault current Ifx can be detected at an earlier stage than the line fault detection that detects the loop fault current Ify.

In the embodiment of the present invention, when a DC fault F1 occurs, each DC circuit breaker follows DC line Ld1 accident determination processing step S302A, DC line Ld2 accident determination processing step S302B, and DC line Ld3 accident determination processing step S302C in FIG. The DC circuit breaker control unit 203 of the DCCB determines a DC accident, and when it determines that an accident has occurred, it transmits a request to open its own circuit breaker.

At this time, in the AC/DC converter station TA with a three-line configuration, the DC circuit breaker control unit 203 of the DC circuit breaker DCCB of each line detects the direct fault current Ifx, the loop fault current Ify, or a composite current of these, and determines the fault. , and there is a high possibility that the DC circuit breaker controllers 203 of the DC circuit breakers DCCBA1, DCCBA2, and DCCBA3 all detect the fault and send a circuit breaker opening request to the central controller CA.

Similarly, in the AC/DC converter station TC with a two-line configuration, the DC circuit breaker control unit 203 of the DC circuit breaker DCCB of each line detects the direct fault current Ifx, the wraparound fault current Ify, or a composite current of these, and determines the fault. There is a high possibility that the DC circuit breaker control units 203 of both the DC circuit breakers DCCBC1 and DCCBC2 have detected an accident and sent a circuit breaker opening request to the central controller CC.

In the AC/DC converter station TB with a single-line configuration, the DC circuit breaker control unit 203 of the DC circuit breaker DCCBB1 detects the fault current Ify to determine the fault, and requests the central controller CB to open the circuit breaker. Most likely sending.

However, in the AC/DC converter station TA with a three-circuit configuration associated with the occurrence of a DC fault, the rate of change over time of IA, IB, and IC is the largest for the reason described above. 203, among the DC circuit breaker control unit 203 of the DC circuit breaker DCCBA2 and the DC circuit breaker control unit 203 of the DC circuit breaker DCCBA3, the DC circuit breaker control unit 203 of the DC circuit breaker DCCBA3 first A release request will be sent to the central protection unit CA.

Similarly, in the AC/DC converter station TC having a two-line configuration, the DC circuit breaker control unit 203 of the DC circuit breaker DCCBC1 and the DC circuit breaker control unit 203 of the DC circuit breaker DCCBC2 will first send a request to open its own circuit breaker to the central protection device CC.

In the case of the AC/DC converter station TB with a single line configuration, the DC circuit breaker control unit 203 of the DC circuit breaker DCCBB1 is more likely to detect an intrusion current Ify and make an accident determination. If the detection time is delayed or the rate of change over time is small, it is determined whether or not the fault is at its own terminal or line, and it is detected that it is not at its own terminal or line, preventing the DC circuit breaker from opening. It is possible to

In this way, the converter station central protection devices CA and CC, which have received the opening requests from the DC circuit breakers DCCBA3 and DCCBC2 connected to the DC line Ld3, select the circuit breakers to be opened and select the corresponding DC circuit breakers DCCBA3 and DCCBC2. Sends an opening command to the other protective device to prevent the other DC circuit breakers from opening.

Thereafter, according to the sequence of FIG. 3, the series of sequences of FIG. 3 is finally completed in completion processing step S307.

In Example 2, several modified examples for carrying out the present invention will be described.

First, in Example 1, a protection control device consisting of a measurement unit, a protection control unit, and a breaker is provided on the DC circuit breaker side, and an opening request is reported from the protection control device to the central protection device, and the approval of the central protection device is obtained. This is a central control type process in which the protection control unit starts the actual shut-off operation.

Instead of this central control type processing, cooperative control type processing by a plurality of protection control devices can be used. In cooperative control type processing by a plurality of protection control devices, each protection control device exchanges open requests with each other, and if an open request comes from another before it generates its own open request, its own open operation is performed. It functions to prevent In short, in one AC/DC conversion station, it is sufficient to detect an accident for each of a plurality of lines, open only one line for which an accident is detected at the earliest point, and prevent other lines from being opened.

Further, in another embodiment of the present invention, for DC accident determination in the DC line Ld1 accident determination processing step S302A, the DC line Ld2 accident determination processing step S302B, and the DC line Ld3 accident determination processing step S302C in FIG. The method of determining an accident based on the rate of change over time is not limited to this method, and a determination method based on the amplitude of the direct current may also be used. Further, the fault may be determined using the amount of change in the undervoltage or the rate of change over time.

In another embodiment of the present invention, when a DC fault occurs, the AC/DC converter may or may not be gate blocked as long as the operation of the equipment and the overcurrent tolerance allow. If the AC/DC converter becomes gate-blocked when a DC fault occurs, the gate-deblocking is performed after the series of sequences shown in FIG. 3 are completed, and the operation can be resumed. Further, the change of the operation command for the AC/DC converter due to the DC fault may be changed arbitrarily as long as it does not deviate from the gist of the present invention.

Alternatively, the AC system G may be a renewable energy power supply group including a renewable energy power supply such as wind power generation and solar power generation, and a plurality of renewable energy power supplies.

G: AC system La: AC transmission lines TA, TB, TC: AC/DC converter station Ld: DC line CON: AC/DC converter Bus: DC bus C: Converter station central protection device DCL: DC reactor 201: DC breaker 202: DC Sensor 203: DC circuit breaker control unit
Ld: DC line

Claims (10)

An AC/DC converter that mutually converts AC and DC is interconnected at one end with an AC transmission system and at the other end with one or more DC lines through a DC circuit breaker. A protection control device for an AC/DC converter station that constitutes a DC power transmission system ,
The protection control device determines a fault in each of the one or more DC lines connected to the AC/DC converter station , opens the DC circuit breaker of the DC line that detected the fault earliest , and detects the fault earliest. A protection control device for an AC/DC converter station, characterized in that it prevents opening of the DC circuit breakers of the DC lines other than the one detected DC line. The protection control device for an AC/DC converter station according to claim 1,
A protection control device for an AC/DC converter station, wherein the other end of the AC/DC converter is connected to a DC line through a DC circuit breaker and a DC reactor, respectively. The protection control device for an AC/DC converter station according to claim 1 ,
A protection control apparatus for an AC/DC converter station, wherein the determination of a fault in the DC line is performed using a time rate of change or a change in an increase in current flowing through the DC line. The protection control device for an AC/DC converter station according to claim 1 ,
A protection control apparatus for an AC/DC converter station, wherein the determination of a fault in the DC line is performed using a time rate of change or a change in voltage drop in the DC line. The protection control device for an AC/DC converter station according to claim 4,
A protection control apparatus for an AC/DC converter station, wherein the determination of an accident in the DC line is performed using a time rate of change or a change in a voltage drop at the other end of a DC reactor installed in the DC line. The protection control device for an AC/DC converter station according to claim 1 ,
A measurement unit provided in each of a plurality of DC lines, which measures physical quantities of the DC lines, a protection control unit which determines an accident on the DC line from the physical quantities, and operates the DC circuit breaker according to commands from the protection control unit. a plurality of protection control devices each comprising a blocking unit that
One protection control device is selected using information on accident determination from the protection control units of the plurality of protection control devices, and the direct current is cut off via the protection control unit and the cutoff unit of the selected protection control device. A protection control device for an AC/DC converter station, comprising: a central protection device for operating a DC converter and preventing opening of a DC circuit breaker in a non-selected protection control device. The protection control device for an AC/DC converter station according to claim 1 ,
For each of a plurality of DC lines, a measurement unit for measuring the physical quantity of the DC line, a protection control unit for determining an accident in the DC line from the physical quantity, and a break that operates the DC circuit breaker according to a command from the protection control unit. a plurality of protective control devices comprising
Each protection control device mutually exchanges the information of the accident determination in the protection control unit, and when the information of the accident determination in the other protection control unit is obtained before the generation of the accident determination in the self protection control unit. 1. A protection control device for an AC/DC converter station, characterized in that it prevents opening of said DC circuit breaker of its own. An AC/DC converter that mutually converts AC and DC is interconnected at one end with an AC transmission system and at the other end with one or more DC lines through a DC circuit breaker. A protection control system for a direct current transmission system, comprising:
A protection control system for a DC transmission system, wherein each AC/DC converter station is provided with the AC/DC converter station protection control device according to claim 1 . An AC/DC converter that mutually converts AC and DC is interconnected at one end with an AC transmission system and at the other end with one or more DC lines through a DC circuit breaker. A protection control method for an AC/DC converter station that constitutes a DC power transmission system by
Determining a fault in each of one or more DC lines connected to the AC/DC converter station , opening the DC circuit breaker of the DC line that detected the fault earliest , and detecting the fault earliest A protection control method for an AC/DC converter station, characterized by preventing opening of the DC circuit breaker of the DC line other than the line. A protection control method for an AC/DC converter station according to claim 9,
When selecting one DC circuit breaker to open, the fault current detected in multiple DC lines is either a direct fault current from the AC/DC converter station, or a wraparound current from an AC/DC converter station adjacent to the AC/DC converter station. A protection control method for an AC/DC converter station, characterized by distinguishing between fault currents and selecting direct fault currents as one of the DC circuit breakers to be opened.

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