CN112234585A - Medium-voltage direct-current power distribution network protection control system and method - Google Patents
Medium-voltage direct-current power distribution network protection control system and method Download PDFInfo
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- CN112234585A CN112234585A CN201910634500.3A CN201910634500A CN112234585A CN 112234585 A CN112234585 A CN 112234585A CN 201910634500 A CN201910634500 A CN 201910634500A CN 112234585 A CN112234585 A CN 112234585A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0061—Details of emergency protective circuit arrangements concerning transmission of signals
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Abstract
The invention discloses a medium-voltage direct-current power distribution network protection control system, which comprises a direct-current protection device and a fault recovery system, wherein the direct-current protection device comprises a direct-current bus differential protection device configured on a medium-voltage direct-current power distribution network bus, a direct-current line differential protection device configured on a looped network cable and a direct-current feeder line protection device configured on a feed-out line, and the fault recovery system and a converter station are arranged in a one-to-one correspondence manner and are used for executing the function of power supply recovery after a fault; the starting end of the converter is provided with a breaker, and the rest of the converter is provided with a load switch; the direct current protection devices are communicated with one another by adopting point-to-point optical fibers, and GOOSE networks are constructed among the current converter, the power electronic transformer, the circuit breaker, the load switch, the direct current protection devices and the fault recovery system so as to communicate with one another. The system adopts differential protection as main protection, and adopts the scheme that the circuit breaker is configured at the initial end of the circuit, and the load switches are configured on the other ends of the circuit, thereby saving investment. The invention also discloses a medium-voltage direct-current power distribution network protection control method.
Description
Technical Field
The invention belongs to the field of direct-current power distribution networks of power systems, and particularly relates to a medium-voltage direct-current power distribution network protection control system and method.
Background
At present, a medium-voltage direct-current power distribution network is in an exploration phase, which type of converter is selected, a pseudo-bipolar or true-bipolar operation mode is adopted, a connection variable grounding mode is selected, the technical performance and the matching of a breaker and a load switch, the processing of a single-pole grounding fault, the communication protocol of primary and secondary equipment, the communication network between the primary and secondary equipment, a fault isolation and fault recovery method and the like are not mature, and the invention provides a solution for the problems.
Disclosure of Invention
The invention aims to provide a medium-voltage direct-current power distribution network protection control system and a medium-voltage direct-current power distribution network protection control method, wherein differential protection is adopted as main protection, and the scheme that a circuit breaker is configured at the initial end of a line and load switches are configured at the rest of the line is adopted, so that the investment is saved.
In order to achieve the above purpose, the solution of the invention is:
a medium-voltage direct-current power distribution network protection control system is characterized in that a medium-voltage direct-current power distribution network is composed of a plurality of converter stations, and a pseudo-bipolar operation mode is adopted to support closed-loop operation and open-loop operation; a current limiting reactor is configured at the starting end of the converter; the distributed power supply and the direct current load are respectively connected to a medium-voltage direct current power distribution network through a power electronic transformer; the protection control system comprises a direct current protection device and a fault recovery system, wherein the direct current protection device comprises a direct current bus differential protection device configured on a medium-voltage direct current distribution network bus, a direct current line differential protection device configured on a looped network cable and a direct current feeder line protection device configured on a feed-out line, and the fault recovery system and the converter station are arranged in a one-to-one correspondence manner and are used for executing the function of power supply recovery after a fault; the starting end of the converter is provided with a breaker, and the rest of the converter is provided with a load switch; the direct current protection devices are communicated with one another by adopting point-to-point optical fibers, and GOOSE networks are constructed among the current converter, the power electronic transformer, the circuit breaker, the load switch, the direct current protection devices and the fault recovery system so as to communicate with one another.
When the medium-voltage direct-current power distribution network operates in a closed loop, one set of fault recovery system serves as a main system, and the rest systems serve as standby systems; when the protection control system operates in an open loop mode, each set of fault recovery system operates independently.
The converter is connected with the variable neutral point and is grounded through a first resistor, the converter is connected with the variable neutral point and is grounded through a switch and a second resistor in sequence, and the resistance value of the first resistor is larger than that of the second resistor; when the medium-voltage direct-current power distribution network operates in an open loop mode, if a single-pole ground fault occurs, the converter station with the single-pole ground fault is thrown into a second resistor; and when the medium-voltage direct-current power distribution network operates in a closed loop mode, if a single-pole ground fault occurs, the second resistor of any station is switched in.
The method for protecting and controlling the system based on the medium-voltage direct-current distribution network comprises the following steps when the medium-voltage direct-current distribution network has a bipolar short-circuit fault:
step 2, the direct current protection device sends a command to a breaker configured at the starting end of the converter to trip off a line;
step 3, the direct current protection device trips off load switches at two ends of a fault point to isolate the fault;
and 4, recovering power supply by the fault recovery system.
The specific content of the step 2 is as follows:
step 21, judging that the direct current protection device at the fault point sends a tripping command to a breaker configured at the initial end of the converter, and disconnecting the power supply;
and step 22, locking the power electronic transformer at the distributed power supply and disconnecting the distributed power supply.
The specific content of the step 4 is as follows:
step 41, after isolating the fault in step 3, the direct current protection device sends the fault isolation information to the fault recovery system;
step 42, after receiving the fault isolation information, the fault recovery system commands a breaker configured at the initial end of the converter to close, and recovers the power supply of the converter;
step 43, the fault recovery system commands the tie switches between the converter stations to close;
step 44, the fault recovery system commands the power electronic transformer at the distributed power supply to restart and recover the distributed power supply;
and step 45, the power electronic transformer on the load side is restarted after detecting that the voltage on the medium voltage side is recovered to be normal, and the normal power supply of the load side is recovered.
When a single-pole ground fault occurs, the method comprises the following steps:
step A, when a single-pole ground fault occurs in a medium-voltage direct-current power distribution network, a fault point is judged by a direct-current protection device;
and step B, the direct current protection device directly trips off the load switches at two ends of the fault point to isolate the fault, and then normal operation is recovered.
After the scheme is adopted, the invention has the following improvements:
(1) because the direct-current circuit breakers are high in price, the direct-current circuit breakers are poor in economical efficiency and do not have popularization, the direct-current circuit breakers are arranged at the initial ends of the circuits, the load switches are arranged on the rest of the circuits, when a bipolar short-circuit fault occurs, the circuit breakers at the initial ends of the circuits are tripped firstly when the fault occurs, and then the load switches are used for isolating the fault, so that the investment is greatly saved;
(2) the current converter is fragile, when a distribution line has a fault, the current converter can be quickly locked, the time is only hundreds of microseconds at the fastest speed, the distribution line is short, the fault current at each position is similar, the fault selectivity is difficult to realize through the matching of the time and the level difference of the fault current, the fault point can be accurately positioned by adopting differential protection, the strategy of fault isolation and fault recovery is easy to realize, and the sensitivity can be improved by adopting differential protection due to the fact that the fault current is small for a single-pole grounding fault, so that the differential protection with high sensitivity and accurate positioning is used as the main protection of the system;
(3) because only the initial end of the line is provided with the direct current breaker and the rest are provided with the load switches, when the bipolar short circuit occurs, the fault current is larger, and the direct current protection can not directly trip the load switches, the invention provides a method for tripping the breaker at the initial end of the line by sending a command after a fault point is positioned by differential protection and then tripping the load switches to isolate the fault, thereby well solving the problem;
(4) for a pseudo bipolar line, when a monopolar earth fault occurs, bipolar voltage unbalance occurs, fault current is very small, and if the voltage unbalance is used as main protection, fault location cannot be carried out, so that the invention provides a method for connecting a variable neutral point and connecting a small resistor in parallel, and carrying out fault isolation of the monopolar earth fault by adopting differential protection with higher sensitivity;
(5) when the single-pole grounding fault occurs, the system can normally operate in a short time, and because the fault current is small, the differential protection can directly trip the load switch to isolate the fault, the fault recovery after the fault isolation basically does not influence the normal operation of the system, and most of the faults are the single-pole grounding faults, so the method can improve the power supply reliability;
(6) the current converter, the power electronic transformer, the circuit breaker, the load switch, the direct current protection device and the fault recovery system need to communicate with each other.
(7) For bipolar short-circuit faults, a processing method of firstly tripping a breaker to remove faults and then isolating the faults by a load switch is provided, for unipolar ground faults, a processing method of directly isolating the faults by the load switch is provided, the efficiency of fault isolation and fault recovery is considered, meanwhile, investment is greatly saved, and a feasible technical scheme is provided for construction of a medium-voltage direct-current power distribution network.
Drawings
FIG. 1 is a system architecture diagram of the present invention.
Detailed Description
The technical solution and the advantages of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, the present invention provides a medium voltage dc distribution network protection control system, which is introduced from the following aspects:
1. mode of operation
The medium-voltage direct-current distribution network is composed of two converter stations H1 and H2, and a pseudo-bipolar operation mode is adopted to support closed-loop operation and open-loop operation.
2. Grounding mode of system
The inverter is connected with a neutral point and is grounded through a resistor with a larger resistance, and the neutral point is connected with resistors Z1 and Z2 with a smaller resistance in series through a switch.
And (4) open-loop operation, and when a single-pole earth fault occurs, the converter station with the single-pole earth fault is put into parallel connection with a small resistor.
And (4) closed-loop operation, and switching into a small resistor Z1 of the H1 converter station or a small resistor Z2 of the H2 converter station when a unipolar ground fault occurs.
3. Configuration of primary devices
The medium-voltage direct-current power distribution network is composed of two converter stations H1 and H2 and supports closed-loop operation and open-loop operation modes; the head end of the converter is provided with current limiting reactors X1 and X2; the head end of the converter is provided with breakers D1 and D2, and the rest switches are provided with load switches; the distributed power supply is connected to a medium-voltage direct-current power distribution network through a power electronic transformer DB 1; the DC load is connected to a medium-voltage DC distribution network through power electronic transformers DB2 and DB 3.
4. Direct current protection
A medium-voltage direct-current power distribution network bus is provided with a direct-current bus differential protection device MB11, and the protection range is corresponding bus; the looped network cable is provided with direct-current line differential protection devices XB111, XB112, XB211 and XB212, and the protection range is corresponding looped network cable; the feed-out line is provided with direct current feed line protection devices K11, K12 and K21, and the protection range is corresponding feed lines.
The single-pole grounding fault problem is solved by connecting the neutral point and the small resistor in parallel. When a single pole breaks down, the voltage is detected to be unbalanced, then the small resistance of the neutral point is connected, the fault current is increased, and the fault isolation is carried out through direct current differential protection.
For the single-pole grounding fault, the system can normally operate in a short time due to small fault current, and the fault is recovered after the direct current differential protection directly trips load switches at two ends of a fault point to isolate the fault.
For the single-pole grounding fault, the system can normally operate in a short time due to small fault current, the direct current differential protection directly trips load switches or circuit breakers at two ends of a fault point to carry out fault isolation, and then the fault is recovered.
For the double-pole short-circuit fault of the power distribution direct-current line, due to the fact that fault current is large, after the fault is located through direct-current protection, a command is sent to a breaker at the outlet of a current converter to trip off the line, then the fault is isolated through load switches at two ends of a direct-current protection tripping fault point, and finally power supply is recovered through a fault recovery system.
5. Fault recovery system
The converter station H1 is provided with a fault recovery system GH1 and the converter station H2 is provided with a fault recovery system GH2 to perform the function of power supply recovery after a fault.
When the closed loop operates, two sets of fault recovery systems are unified to be primary and secondary.
When the open loop is operated, each set is independently operated.
6. Communication network
And special point-to-point optical fibers are adopted for communication between the direct current line differential protection.
GOOSE networks are constructed among the current converter, the power electronic transformer, the circuit breaker, the load switch, the direct current protection device and the fault recovery system for mutual communication.
The invention also provides a medium-voltage direct-current power distribution network protection control method, which comprises a bipolar short-circuit fault processing method and a unipolar ground fault processing method, wherein the contents of the methods are respectively as follows:
the bipolar short-circuit fault processing method comprises the following steps:
when a bipolar short-circuit fault occurs, because the fault current is large, the fault needs to be positioned by direct current protection, then a command is sent to a breaker at the outlet of the current converter to trip off a circuit, then load switches at two ends of a fault point are tripped by the direct current protection, the fault is isolated, and finally power supply is recovered by the fault recovery system.
The method for processing the single-pole ground fault comprises the following steps:
the single-pole grounding fault problem is solved by connecting the neutral point and the small resistor in parallel. When a single pole breaks down, a small resistor of a connection neutral point is put into the voltage detection circuit after voltage unbalance is detected, fault current is increased, and fault isolation is carried out through direct current differential protection;
when the single-pole earth fault occurs, the system can normally operate in a short time due to small fault current, and the fault is recovered after the direct current differential protection directly trips load switches at two ends of a fault point to isolate the fault.
1. Fault isolation and fault recovery for bipolar short-circuit fault during open-loop operation (similar to fault isolation and fault recovery during closed-loop operation):
step 1: when a bipolar short-circuit fault occurs at the point f1 in the medium-voltage direct-current power distribution network, judging the fault point by direct-current line differential protection devices XB111 and XB 112;
step 2: the direct-current line differential protection device XB111 sends a command to a breaker D2 to trip, and a half-bridge end power supply is disconnected;
and step 3: the power electronic transformer DB1 at the photovoltaic distributed power supply is locked, and the distributed power supply is disconnected;
and 4, step 4: the direct current protection device trips off a load switch F1 around a fault point to isolate the fault;
and 5: the direct current protection sends the fault isolation information to a fault recovery system GH 1;
step 6: after receiving a fault isolation signal, the fault recovery system GH1 sends a command to the circuit breaker D1 to close, and a half-bridge end power supply is recovered;
and 7: the fault recovery system GH1 sends a command to close the tie switch F4;
and 8: the fault recovery system sends a command to a power electronic transformer DB1 at the distributed power supply to restart and recover the distributed power supply;
and step 9: the power electronic transformer DB2 is restarted after detecting that the medium-voltage side voltage is restored to normal, and the inter-electrode voltage and the load-side normal power supply are restored.
2. Fault isolation and fault recovery for single-pole ground fault on open-loop operation (similar steps for fault isolation and fault recovery on closed-loop operation):
step 1: when a single-pole ground fault occurs at a point f1 of the medium-voltage direct-current distribution network, judging a fault point by using direct-current line differential protection devices XB111 and XB 112;
step 2: because the fault current is small, the direct current distribution system can run in a short time, the direct current line differential protection devices XB111 and XB112 break away the circuit breakers D1 and the load switches F1 at two ends of a fault point to isolate faults, and then the system recovers to run normally.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.
Claims (7)
1. A medium-voltage direct-current power distribution network protection control system is characterized in that a medium-voltage direct-current power distribution network is composed of a plurality of converter stations, and a pseudo-bipolar operation mode is adopted to support closed-loop operation and open-loop operation; a current limiting reactor is configured at the starting end of the converter; the distributed power supply and the direct current load are respectively connected to a medium-voltage direct current power distribution network through a power electronic transformer; the method is characterized in that: the protection control system comprises a direct current protection device and a fault recovery system, wherein the direct current protection device comprises a direct current bus differential protection device configured on a medium-voltage direct current distribution network bus, a direct current line differential protection device configured on a looped network cable and a direct current feeder line protection device configured on a feed-out line, and the fault recovery system and the converter station are arranged in a one-to-one correspondence manner and are used for executing the function of power supply recovery after a fault; the starting end of the converter is provided with a breaker, and the rest of the converter is provided with a load switch; the direct current protection devices are communicated with one another by adopting point-to-point optical fibers, and GOOSE networks are constructed among the current converter, the power electronic transformer, the circuit breaker, the load switch, the direct current protection devices and the fault recovery system so as to communicate with one another.
2. The medium voltage direct current distribution network protection control system of claim 1, characterized by: when the medium-voltage direct-current power distribution network operates in a closed loop mode, one set of fault recovery system serves as a main system, and the rest of fault recovery systems serve as standby systems; when the protection control system operates in an open loop mode, each set of fault recovery system operates independently.
3. The medium voltage direct current distribution network protection control system of claim 1, characterized by: the converter is connected with the variable neutral point and is grounded through a first resistor, the converter is connected with the variable neutral point and is grounded through a switch and a second resistor in sequence, and the resistance value of the first resistor is larger than that of the second resistor; when the medium-voltage direct-current power distribution network operates in an open loop mode, if a single-pole ground fault occurs, the converter station with the single-pole ground fault is thrown into a second resistor; and when the medium-voltage direct-current power distribution network operates in a closed loop mode, if a single-pole ground fault occurs, the second resistor of any station is switched in.
4. The method for protecting and controlling the medium voltage direct current distribution network according to claim 1, wherein: when a bipolar short-circuit fault occurs in a medium-voltage direct-current power distribution network, the method comprises the following steps:
step 1, judging a fault point by a direct current protection device;
step 2, the direct current protection device sends a command to a breaker configured at the starting end of the converter to trip off a line;
step 3, the direct current protection device trips off load switches at two ends of a fault point to isolate the fault;
and 4, recovering power supply by the fault recovery system.
5. The method of claim 4, wherein: the specific content of the step 2 is as follows:
step 21, judging that the direct current protection device at the fault point sends a tripping command to a breaker configured at the initial end of the converter, and disconnecting the power supply;
and step 22, locking the power electronic transformer at the distributed power supply and disconnecting the distributed power supply.
6. The method of claim 4, wherein: the specific content of the step 4 is as follows:
step 41, after isolating the fault in step 3, the direct current protection device sends the fault isolation information to the fault recovery system;
step 42, after receiving the fault isolation information, the fault recovery system commands a breaker configured at the initial end of the converter to close, and recovers the power supply of the converter;
step 43, the fault recovery system commands the tie switches between the converter stations to close;
step 44, the fault recovery system commands the power electronic transformer at the distributed power supply to restart and recover the distributed power supply;
and step 45, the power electronic transformer on the load side is restarted after detecting that the voltage on the medium voltage side is recovered to be normal, and the normal power supply of the load side is recovered.
7. The method of claim 4, wherein: when a single-pole ground fault occurs, the method comprises the following steps:
step A, when a single-pole ground fault occurs in a medium-voltage direct-current power distribution network, a fault point is judged by a direct-current protection device;
and step B, the direct current protection device directly trips off the load switches at two ends of the fault point to isolate the fault, and then normal operation is recovered.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113820562A (en) * | 2021-09-08 | 2021-12-21 | 国电南瑞科技股份有限公司 | Low-voltage direct-current power distribution network fault processing system and method |
| CN114520493A (en) * | 2022-03-10 | 2022-05-20 | 南京智汇电力技术有限公司 | Self-adaptive incomplete differential protection method for series supply line of distribution network |
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Application publication date: 20210115 |