CN115021227A - Fault protection system, method and device suitable for bipolar direct current power distribution network - Google Patents

Fault protection system, method and device suitable for bipolar direct current power distribution network Download PDF

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Publication number
CN115021227A
CN115021227A CN202210761186.7A CN202210761186A CN115021227A CN 115021227 A CN115021227 A CN 115021227A CN 202210761186 A CN202210761186 A CN 202210761186A CN 115021227 A CN115021227 A CN 115021227A
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current
phase
distribution network
power distribution
fault
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金莉
雷二涛
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Guangdong Power Grid Co Ltd
Electric Power Research Institute of Guangdong Power Grid Co Ltd
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Guangdong Power Grid Co Ltd
Electric Power Research Institute of Guangdong Power Grid Co Ltd
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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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

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Abstract

The invention discloses a fault protection system, a method and a device suitable for a bipolar direct current power distribution network, wherein the system comprises: the system comprises a bipolar direct-current power distribution network, a control module and two circuit breakers; the first circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the input end of the sending end converter, the second circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter, and the control module is respectively connected with the two circuit breakers and connected with the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter. According to the invention, the fault type judgment can be realized by detecting the current amplitude change of the alternating current side circuit of the sending end converter and the magnitude of the positive and negative sequence components of the current, and the system fault removal and fault protection during the network side fault are realized by additionally arranging the alternating current breaker on the alternating current side of the sending end converter.

Description

Fault protection system, method and device suitable for bipolar direct-current power distribution network
Technical Field
The invention relates to the technical field of power grid fault protection, in particular to a fault protection system, method and device suitable for a bipolar direct-current power distribution network.
Background
As each power transmission device in a remote rural area ages, the voltage at the power transmission end is seriously insufficient, and the problem of the voltage qualification rate of the remote rural area is increasingly prominent. In order to solve the problem of low voltage at the tail end, the current common mode extends the power supply radius by properly increasing the power transmission and distribution voltage through direct current power distribution.
One commonly used power distribution device is a bipolar dc power distribution system, which introduces a power electronic converter to implement low-voltage dc power distribution. Because the bipolar direct-current power distribution system is expensive in manufacturing cost, once a fault occurs in the using process, the whole machine stops running, and technicians detect the fault on the spot to determine the fault reason and carry out corresponding maintenance.
However, the above-mentioned fault protection method has the following technical problems: the complete machine stops operating, can cause the terminal power supply not enough, is difficult to satisfy user's user demand, and artifical verification trouble reason carries out maintenance protection moreover, and is inefficient and cost of maintenance is high.
Disclosure of Invention
The invention provides a fault protection system, a method and a device suitable for a bipolar direct current power distribution network.
A first aspect of an embodiment of the present invention provides a fault protection system suitable for a bipolar dc power distribution network, where the system includes: the system comprises a bipolar direct-current power distribution network, a control module and two circuit breakers;
the first circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the input end of the sending end converter, the second circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter, and the control module is respectively connected with the two circuit breakers and the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter;
the control module is used for detecting the current change amplitude and the current positive and negative sequence components of a sending end converter of the bipolar direct current power distribution network on an alternating current side circuit, determining whether a circuit fault occurs or not based on the current change amplitude and the current positive and negative sequence components, and controlling the circuit breaker to start if the circuit fault occurs.
In a possible implementation manner of the first aspect, the control module includes: a current inner loop unit, a synchronous phase lock unit (PLL), a pulse modulation unit (PWM) and two proportional-integral regulator units (PI);
the output end of the first PI unit is connected with the input end of the current inner loop unit, the output end of the PLL unit is connected with the connecting end of the first PI unit and the current inner loop unit, the input end of the PLL unit is connected with the current inner loop unit, the output end of the second PI unit, the output end of the current inner loop unit and the output end of the PLL unit are connected, and line signals of the connecting end are added and then connected with the input end of the PWM unit.
In a possible implementation manner of the first aspect, the current inner loop unit includes: and the current inner loop signal intersection point is respectively connected with the output end of the first PI unit and the input end of the PLL unit, and the output end of the current inner loop signal intersection point is connected with the input end of the proportional regulator unit.
A second aspect of the embodiments of the present invention provides a fault protection method for a bipolar dc power distribution network, the method being applied to the fault protection system for a bipolar dc power distribution network as described above, the method including:
collecting the current amplitude of a sending end converter of a direct current distribution network at an alternating current side;
when the current amplitude is larger than a preset value, acquiring a three-phase voltage value of the sending end converter on the alternating current side;
and determining whether a line fault occurs or not based on the three-phase voltage value, and triggering the circuit breaker to start when the line fault occurs.
In one possible implementation form of the second aspect, the line fault comprises a three-phase short-circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the three-phase voltage value suddenly drops to zero, determining that the line fault is a three-phase short circuit fault.
In one possible implementation form of the second aspect, the line fault comprises a two-phase short-circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if one of the three-phase voltage values suddenly drops and the remaining two-phase voltage values are normal, determining that the line fault is a two-phase short circuit fault.
In one possible implementation form of the second aspect, the line fault comprises a single-phase short-circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the two-phase voltage values of the three-phase voltage values are equal, the amplitude of the voltage value is half of the rated voltage, and the remaining one-phase voltage value is normal, determining that the line fault is a single-phase short-circuit fault.
In a possible implementation manner of the second aspect, the acquiring a current amplitude of a sending end converter of the dc power distribution network on an ac side includes:
collecting a three-phase current value of a sending end converter of a direct current distribution network at an alternating current side;
carrying out coordinate conversion on the three-phase current value to obtain a two-phase current value;
and calculating the current amplitude based on the two-phase current value.
In a possible implementation manner of the second aspect, the coordinate converting the three-phase current value to obtain a two-phase current value includes:
obtaining a three-phase static coordinate system of the three-phase current value, and converting the three-phase static coordinate system into a two-phase static coordinate system, wherein a conversion formula is as follows:
Figure BDA0003724282030000031
in the above formula, α represents a numerical value of an α axis in the two-phase stationary coordinate system, β represents a numerical value of a β axis in the two-phase stationary coordinate system, and a, b, and c represent three phases in the three-phase stationary coordinate system, respectively.
A third aspect of the embodiments of the present invention provides a fault protection device suitable for a bipolar dc power distribution network, the device being suitable for a fault protection system suitable for a bipolar dc power distribution network as described above, the device including:
the current acquisition module is used for acquiring the current amplitude of a sending end converter of the direct-current power distribution network on an alternating-current side;
the voltage acquisition module is used for acquiring a three-phase voltage value of the sending end converter on the alternating current side when the current amplitude value is larger than a preset value;
and the fault protection module is used for determining whether a line fault occurs or not based on the three-phase voltage value and triggering the circuit breaker to start when the line fault occurs.
Compared with the prior art, the fault protection system, method and device suitable for the bipolar direct current power distribution network provided by the embodiment of the invention have the beneficial effects that: the invention can realize fault type judgment (three-phase short circuit, two-phase short circuit and single-phase grounding) by detecting the current amplitude change of the alternating current side circuit of the sending end converter and the magnitude of the positive and negative sequence components of the current, can realize system fault removal when a network side fault occurs by additionally arranging the alternating current breaker on the alternating current side of the sending end converter, and can realize fault protection of the sending end converter by locking a switching tube of the sending end converter.
Drawings
Fig. 1 is a schematic structural diagram of a fault protection system suitable for a bipolar dc power distribution network according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a fault protection system suitable for a bipolar dc power distribution network according to an embodiment of the present invention;
fig. 3 is a schematic flowchart of a fault protection method applied to a bipolar dc power distribution network according to an embodiment of the present invention;
fig. 4 is an operation flowchart of a three-phase short detection process according to an embodiment of the present invention;
FIG. 5 is a waveform diagram of voltage and current at the three-phase short-circuited AC side according to an embodiment of the invention;
FIG. 6 is a flowchart illustrating the operation of a two-phase short detection process according to an embodiment of the present invention;
FIG. 7 is a diagram of voltage and current waveforms at the two-phase short-circuited AC side according to an embodiment of the present invention;
fig. 8 is an operation flowchart of a single-phase short circuit detection process according to an embodiment of the present invention;
FIG. 9 is a waveform diagram of voltage and current at the single-phase short-circuited AC side according to an embodiment of the invention;
FIG. 10 is a graph of the voltage and current waveforms after the three phases are shorted and the converter is locked according to one embodiment of the present invention;
FIG. 11 is a graph of voltage and current waveforms after two phases are shorted and the converter is locked according to an embodiment of the present invention;
FIG. 12 is a voltage-current waveform diagram after a single-phase short circuit and a locked converter according to an embodiment of the present invention;
fig. 13 is a schematic structural diagram of a fault protection device suitable for a bipolar dc power distribution network according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
One commonly used power distribution device is a bipolar dc power distribution system, which introduces a power electronic converter to implement low-voltage dc power distribution. Because the bipolar direct-current power distribution system is expensive in manufacturing cost, once a fault occurs in the using process, the whole machine stops running, and technicians detect the fault on the spot to determine the fault reason and carry out corresponding maintenance.
However, the above-mentioned fault protection method has the following technical problems: the complete machine stops operating, can cause the terminal power supply not enough, is difficult to satisfy user's user demand, and artifical verification trouble reason carries out maintenance protection moreover, and is inefficient and cost of maintenance is high.
In order to solve the above problem, a fault protection system suitable for a bipolar dc power distribution network according to the embodiments of the present application will be described and illustrated in detail by the following specific embodiments.
Referring to fig. 1-2, a schematic structural diagram of a fault protection system suitable for a bipolar dc power distribution network according to an embodiment of the present invention and a schematic structural diagram of a fault protection system suitable for a bipolar dc power distribution network according to an embodiment of the present invention are respectively shown.
The fault protection system suitable for the bipolar direct current power distribution network can comprise:
the system comprises a bipolar direct-current power distribution network, a control module and two circuit breakers;
the first circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the input end of the sending end converter, the second circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter, and the control module is respectively connected with the two circuit breakers and the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter;
the control module is used for detecting the current change amplitude and the current positive and negative sequence components of a sending end converter of the bipolar direct current power distribution network on an alternating current side circuit, determining whether a circuit fault occurs or not based on the current change amplitude and the current positive and negative sequence components, and controlling the circuit breaker to start if the circuit fault occurs.
Referring to fig. 1-2, in one embodiment, the control module includes: a current inner loop unit, a synchronous phase lock unit (PLL), a pulse modulation unit (PWM) and two proportional-integral regulator units (PI);
the output end of the first PI unit is connected with the input end of the current inner loop unit, the output end of the PLL unit is connected with the connecting end of the first PI unit and the current inner loop unit, the input end of the PLL unit is connected with the current inner loop unit, the output end of the second PI unit, the output end of the current inner loop unit and the output end of the PLL unit are connected, and line signals of the connecting end are added and then connected with the input end of the PWM unit.
Specifically, the current inner loop unit includes: and the current inner loop signal intersection point is respectively connected with the output end of the first PI unit and the input end of the PLL unit, and the output end of the current inner loop signal intersection point is connected with the input end of the proportional regulator unit (P).
In this embodiment, an embodiment of the present invention provides a fault protection system suitable for a bipolar dc power distribution network, which has the following beneficial effects: the current parameter of the sending end converter of the bipolar direct current power distribution network can be monitored in real time through the control module, whether the power distribution network has faults or not and the fault type of the power distribution network are determined based on the current parameter, and the breaker can be controlled to break the circuit immediately after the faults are determined, so that the power distribution network is protected, on one hand, the fault type does not need to be overhauled manually, the detection accuracy is improved, on the other hand, the power distribution network can be protected quickly, the protection efficiency is improved, and the equipment damage is avoided.
Referring to fig. 3, a schematic flow chart of a fault protection method suitable for a bipolar dc power distribution network according to an embodiment of the present invention is shown.
In one embodiment, the method is applied to the fault protection system applicable to the bipolar direct current power distribution network of the above embodiment.
As an example, the fault protection method applied to the bipolar dc power distribution network may include:
and S11, collecting the current amplitude of the sending end converter of the direct current distribution network on the alternating current side.
Referring to fig. 1, the current amplitude of the sending-end converter on the ac side may be collected by the control module.
In order to accurately calculate the current amplitude of the sending-end converter on the ac side, step S11 may include the following sub-steps, as an example:
and S111, collecting a three-phase current value of a sending end converter of the direct-current distribution network on an alternating-current side.
S112, carrying out coordinate conversion on the three-phase current value to obtain a two-phase current value;
specifically, the two-phase current value is calculated as follows:
obtaining a three-phase static coordinate system of the three-phase current value, and converting the three-phase static coordinate system into a two-phase static coordinate system, wherein a conversion formula is as follows:
Figure BDA0003724282030000071
in the above formula, α represents a numerical value of an α axis in the two-phase stationary coordinate system, β represents a numerical value of a β axis in the two-phase stationary coordinate system, and a, b, and c represent three phases in the three-phase stationary coordinate system, respectively.
And S113, calculating the current amplitude based on the two-phase current value.
Specifically, the current amplitude may be obtained by adding the square of α to the square of β and then squaring the sum.
And S12, when the current amplitude is larger than a preset value, acquiring a three-phase voltage value of the sending end converter on the alternating current side.
Comparing the current amplitude with a preset value, if the current amplitude is smaller than or equal to the preset value, determining that the power distribution network is normal, and if the current amplitude is larger than the preset value, the power distribution network possibly breaks down; the three-phase voltage value of the sending-end converter on the alternating current side can be collected.
And S13, determining whether a line fault occurs or not based on the three-phase voltage values, and triggering the circuit breaker to start when the line fault occurs.
In one embodiment, the determination of whether a line fault has occurred based on the three-phase voltage values and the determination of the type of line fault for the power distribution network based on the voltage magnitudes of the three-phase voltage values may be performed. When a fault occurs, the circuit breaker can be started immediately to break the circuit, so that the damage of the power distribution network is avoided, and meanwhile, technicians can be informed to carry out corresponding maintenance according to the type of the circuit fault.
Referring to fig. 4 to 5, an operation flow chart of a three-phase short circuit detection process according to an embodiment of the present invention and a three-phase short circuit ac side voltage and current waveform chart according to an embodiment of the present invention are respectively shown.
In one embodiment, the line fault comprises a three-phase short circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the three-phase voltage value suddenly drops to zero, determining that the line fault is a three-phase short circuit fault.
Specifically, a three-phase current value of a sending end converter of the direct-current power distribution network on an alternating-current side can be collected in real time, the three-phase current value is converted into a two-phase current value, a current amplitude value is calculated by adopting the two-phase current value, when the current amplitude value is larger than a preset value, a three-phase voltage value can be collected, and when the three-phase voltage value suddenly drops to zero, a line fault is determined to be a three-phase short-circuit fault.
Referring to fig. 5, it can be seen that fig. 5 shows simulated waveforms of voltage and current on the primary side of the transformer and on the ac side of the transmitting converter in the case of a three-phase short circuit on the grid side. The simulation is that when 1s, three-phase short circuit occurs on the primary side of the transformer, the voltage of the primary side of the transformer is immediately reduced to zero, and at the moment, the current on the alternating current side of the sending end converter begins to rise, and the maximum current of the sending end converter is limited due to the action of the current inner loop of the control system. Meanwhile, the alternating current side current of the sending-end converter generates a current with a reduced equal transformation ratio on the primary side through the transformer.
Referring to fig. 6 to 7, an operation flow chart of a two-phase short circuit detection process according to an embodiment of the present invention and a voltage-current waveform diagram of an ac side of a two-phase short circuit according to an embodiment of the present invention are respectively shown.
In one embodiment, the line fault comprises a two-phase short circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if one of the three-phase voltage values suddenly drops and the remaining two-phase voltage values are normal, determining that the line fault is a two-phase short-circuit fault.
Specifically, a three-phase current value of a sending end converter of the direct-current power distribution network on an alternating-current side can be collected in real time, the three-phase current value is converted into a two-phase current value, a current amplitude value is calculated by adopting the two-phase current value, when the current amplitude value is larger than a preset value, a three-phase voltage value can be collected, and when one phase voltage value of the three-phase voltage value suddenly drops and the remaining two-phase voltage value is normal, a line fault is determined to be a two-phase short-circuit fault.
Referring to fig. 6, when two-phase short circuit occurs on the grid side, the secondary side of the transformer is equivalent to a single-phase short circuit. The alternating voltage can be decomposed into a positive sequence component and a negative sequence component. For the DC side voltage of the sending-end converter, the AC side voltage contains a negative sequence component, so the current of the AC side voltage also contains a negative sequence component, and the capacitor voltage fluctuates at double frequency of the fundamental wave.
In the case of a two-phase short circuit, the ac output voltage of the transmitting converter is a positive-sequence voltage when the dc side voltage does not fluctuate, and the secondary voltage of the transformer contains a negative-sequence component, so that an overcurrent is generated in the negative-sequence network. In practice, the overcurrent is much smaller than the three-phase short circuit because, on the one hand, the converter output ac voltage contains a negative sequence component due to the dc-side voltage fluctuation of the converter, and, on the other hand, the negative sequence component in the secondary voltage of the transformer has a smaller magnitude.
Fig. 6 is a graph of a voltage and current waveform of a grid side under a simulated two-phase short circuit, and it can be seen from the graph that the two-phase short circuit occurs at 1s, and thereafter, the voltages of the primary side and the secondary side of the transformer are changed as analyzed and calculated previously, and three-phase unbalanced currents are generated.
In actual operation, when a two-phase short circuit occurs on the primary side of the transformer, current increase occurs on the alternating current side of the sending-end converter, and a large amount of unbalanced current is transmitted to a power grid. If the current carrying capacity of the line can meet the current, the current is not enough to cause danger, and when the current does not sufficiently flow through the line, the alternating current breaker is opened to isolate the fault.
Referring to fig. 8 to 9, an operation flowchart of a single-phase short circuit detection process according to an embodiment of the present invention and a voltage-current waveform diagram of a single-phase short circuit ac side according to an embodiment of the present invention are respectively shown.
In one embodiment, the line fault comprises a single-phase short-circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the two-phase voltage values of the three-phase voltage values are equal, the amplitude of the voltage value is half of the rated voltage, and the remaining one-phase voltage value is normal, determining that the line fault is a single-phase short-circuit fault.
Specifically, a three-phase current value of a sending end converter of the direct-current power distribution network on an alternating-current side can be collected in real time, the three-phase current value is converted into a two-phase current value, a current amplitude value is calculated by adopting the two-phase current value, when the current amplitude value is larger than a preset value, a three-phase voltage value can be collected, when two phase voltage values of the three-phase voltage value are equal, the amplitude value of the voltage value is half of a rated voltage, and the remaining one-phase voltage value is normal, the line fault is determined to be a single-phase short-circuit fault.
Referring to fig. 9, since the neutral point is grounded in the bipolar dc power distribution, no overvoltage occurs when a single-phase short circuit occurs on the grid side, and the fault voltage is equivalent to a single-phase disconnection, but a single-phase overcurrent occurs.
Under bipolar type direct current distribution, when a single-phase short circuit occurs on the network side, the voltage on the primary side of the transformer becomes:
Figure BDA0003724282030000101
therefore, assuming that the transformation ratio of the transformer is k, the voltage of the secondary side of the transformer is obtained as follows:
Figure BDA0003724282030000102
therefore, a large amount of zero sequence components and negative sequence components are introduced into the secondary side of the transformer at the moment, and fig. 9 can be obtained by simulating the situation, wherein the voltage and the current are respectively the voltage and the current on the primary side of the transformer and the alternating current side of the transmitting-end converter after the single-phase grounding of the network side.
When the single-phase grounding appears on the network side, the voltage of the direct current side can not be reduced, the transmission of electric energy can still be carried out on the line, and the load voltage can be maintained to be normal. However, because the voltage and the current on the line have double frequency fluctuation, the loss on the line can be increased, the fault can be judged by detecting the current and the voltage fluctuation on the line, and the whole system is isolated from a fault point by the circuit breaker.
Specifically, after the line fault is determined, the circuit breaker can be triggered to start immediately to disconnect the connection line of the power distribution network, so that the sending-end converter does not transmit electric energy to the short-circuit point any more, and the converter is locked to ensure the safety of the power grid.
Referring to fig. 10 to 12, a voltage-current waveform diagram after three-phase short circuit and blocking converter provided by an embodiment of the present invention, a voltage-current waveform diagram after two-phase short circuit and blocking converter provided by an embodiment of the present invention, and a voltage-current waveform diagram after single-phase short circuit and blocking converter provided by an embodiment of the present invention are respectively shown.
After the circuit breakers are started, a bipolar low-voltage direct-current power distribution system has a network side fault, the fault is isolated by adopting a scheme of additionally arranging the circuit breakers on a line, the protection structure diagram of the whole system is shown in figures 10-12, and six groups of circuit breakers in the figures can be used for fault isolation and alternating current-direct current switching. When a fault on the grid side is detected, the circuit breaker S1 is opened to protect the converter and S2 is opened to prevent overcurrent from flowing into the line, at which point the entire distribution network has been disconnected from the main network and the energy source is lost.
In this embodiment, an embodiment of the present invention provides a fault protection method suitable for a bipolar dc power distribution network, which has the following beneficial effects: the invention can realize fault type judgment (three-phase short circuit, two-phase short circuit and single-phase grounding) by detecting the current amplitude change of the alternating current side circuit of the sending end converter and the magnitude of the positive and negative sequence components of the current, can realize system fault removal when a network side fault occurs by additionally arranging the alternating current breaker on the alternating current side of the sending end converter, and can realize fault protection of the sending end converter by locking a switching tube of the sending end converter.
An embodiment of the present invention further provides a fault protection device suitable for a bipolar dc power distribution network, and referring to fig. 13, a schematic structural diagram of the fault protection device suitable for the bipolar dc power distribution network according to an embodiment of the present invention is shown.
The device is suitable for the fault protection system suitable for the bipolar direct current power distribution network according to the embodiment.
The fault protection device suitable for the bipolar direct current power distribution network can comprise:
the current acquisition module 301 is used for acquiring the current amplitude value of a sending end converter of the direct-current power distribution network at the alternating-current side;
the voltage acquisition module 302 is used for acquiring a three-phase voltage value of the sending end converter on the alternating current side when the current amplitude is larger than a preset value;
and the fault protection module 303 is configured to determine whether a line fault occurs based on the three-phase voltage value, and trigger the circuit breaker to start when the line fault occurs.
Optionally, the line fault comprises a three-phase short circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the three-phase voltage value suddenly drops to zero, determining that the line fault is a three-phase short circuit fault.
Optionally, the line fault comprises a two-phase short circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if one of the three-phase voltage values suddenly drops and the remaining two-phase voltage values are normal, determining that the line fault is a two-phase short-circuit fault.
Optionally, the line fault comprises a single-phase short-circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the two-phase voltage values of the three-phase voltage values are equal, the amplitude of the voltage value is half of the rated voltage, and the remaining one-phase voltage value is normal, determining that the line fault is a single-phase short-circuit fault.
Optionally, the current collection module is further configured to:
collecting a three-phase current value of a sending end converter of a direct current distribution network at an alternating current side;
carrying out coordinate conversion on the three-phase current value to obtain a two-phase current value;
and calculating the current amplitude based on the two-phase current value.
Optionally, the current collection module is further configured to:
acquiring a three-phase stationary coordinate system of the three-phase current value, and converting the three-phase stationary coordinate system into a two-phase stationary coordinate system, wherein a conversion formula is as follows:
Figure BDA0003724282030000121
in the above formula, α represents a numerical value of an α axis in the two-phase stationary coordinate system, β represents a numerical value of a β axis in the two-phase stationary coordinate system, and a, b, and c represent three phases in the three-phase stationary coordinate system, respectively.
It can be clearly understood by those skilled in the art that, for convenience and brevity, the specific working process of the apparatus described above may refer to the corresponding process in the foregoing method embodiment, and is not described herein again.
Further, an embodiment of the present application further provides an electronic device, including: the fault protection method for the bipolar direct current power distribution network comprises the following steps of storing a program, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor executes the program to realize the fault protection method suitable for the bipolar direct current power distribution network according to the embodiment.
Further, the present application also provides a computer-readable storage medium storing computer-executable instructions for causing a computer to execute the fault protection method for a bipolar dc power distribution network according to the foregoing embodiment.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims (10)

1. A fault protection system suitable for use in a bipolar dc power distribution network, the system comprising: the system comprises a bipolar direct-current power distribution network, a control module and two circuit breakers;
the first circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the input end of the sending end converter, the second circuit breaker is arranged on a connecting line between the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter, and the control module is respectively connected with the two circuit breakers and the primary side of the bipolar direct-current power distribution network and the output end of the sending end converter;
the control module is used for detecting the current change amplitude and the current positive and negative sequence components of a sending end converter of the bipolar direct current power distribution network on an alternating current side circuit, determining whether a circuit fault occurs or not based on the current change amplitude and the current positive and negative sequence components, and controlling the circuit breaker to start if the circuit fault occurs.
2. The fault protection system suitable for the bipolar direct current power distribution network according to claim 1, wherein the control module comprises: the device comprises a current inner loop unit, a synchronous phase locking unit, a pulse modulation unit and two proportional-integral regulator units;
the output end of the first proportional-integral regulator unit is connected with the input end of the current inner loop unit, the output end of the synchronous phase-locking unit is connected with the connecting end of the first proportional-integral regulator unit and the current inner loop unit, the input end of the synchronous phase-locking unit is connected with the current inner loop unit, the output end of the second proportional-integral regulator unit, the output end of the current inner loop unit and the output end of the synchronous phase-locking unit are connected, and line signals of the connecting end are added and then connected with the input end of the pulse modulation unit.
3. The fault protection system suitable for the bipolar direct current power distribution network according to claim 2, wherein the current inner loop unit comprises: the phase-locked loop control circuit comprises a proportional regulator unit and a current inner loop signal intersection point, wherein the current inner loop signal intersection point is respectively connected with the output end of the first proportional-integral regulator unit and the input end of the synchronous phase-locked unit, and the output end of the current inner loop signal intersection point is connected with the input end of the proportional regulator unit.
4. A fault protection method for a bipolar dc power distribution network, wherein the method is applied to the fault protection system for the bipolar dc power distribution network according to any one of claims 1 to 3, and the method comprises:
collecting the current amplitude of a sending end converter of a direct current distribution network at an alternating current side;
when the current amplitude is larger than a preset value, acquiring a three-phase voltage value of the sending end converter on the alternating current side;
and determining whether a line fault occurs or not based on the three-phase voltage value, and triggering the circuit breaker to start when the line fault occurs.
5. The fault protection method suitable for use in a bipolar DC power distribution network according to claim 4, wherein said line fault comprises a three-phase short circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the three-phase voltage value suddenly drops to zero, determining that the line fault is a three-phase short circuit fault.
6. The fault protection method suitable for the bipolar direct current power distribution network according to claim 4, wherein the line fault comprises a two-phase short circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if one of the three-phase voltage values suddenly drops and the remaining two-phase voltage values are normal, determining that the line fault is a two-phase short-circuit fault.
7. The fault protection method suitable for the bipolar direct current power distribution network according to claim 4, wherein the line fault comprises a single-phase short-circuit fault;
the determining whether a line fault occurs based on the three-phase voltage values includes:
and if the two-phase voltage values of the three-phase voltage values are equal, the amplitude of the voltage value is half of the rated voltage, and the remaining one-phase voltage value is normal, determining that the line fault is a single-phase short-circuit fault.
8. The fault protection method for the bipolar type direct current power distribution network according to any one of claims 5-7, wherein the collecting the current amplitude of the sending end converter of the direct current power distribution network on the alternating current side comprises:
collecting a three-phase current value of a sending end converter of a direct current distribution network at an alternating current side;
carrying out coordinate conversion on the three-phase current value to obtain a two-phase current value;
and calculating the current amplitude based on the two-phase current value.
9. The fault protection method for the bipolar dc power distribution network according to claim 8, wherein the coordinate transformation of the three-phase current values to obtain two-phase current values comprises:
obtaining a three-phase static coordinate system of the three-phase current value, and converting the three-phase static coordinate system into a two-phase static coordinate system, wherein a conversion formula is as follows:
Figure FDA0003724282020000031
in the above formula, α represents a numerical value of an α axis in the two-phase stationary coordinate system, β represents a numerical value of a β axis in the two-phase stationary coordinate system, and a, b, and c represent three phases in the three-phase stationary coordinate system, respectively.
10. A fault protection device for a bipolar dc power distribution network, wherein the device is adapted for use in a fault protection system according to any one of claims 1-3 for a bipolar dc power distribution network, the device comprising:
the current acquisition module is used for acquiring the current amplitude of a sending end converter of the direct-current power distribution network on an alternating-current side;
the voltage acquisition module is used for acquiring a three-phase voltage value of the sending end converter on the alternating current side when the current amplitude value is larger than a preset value;
and the fault protection module is used for determining whether a line fault occurs or not based on the three-phase voltage value and triggering the circuit breaker to start when the line fault occurs.
CN202210761186.7A 2022-06-30 2022-06-30 Fault protection system, method and device suitable for bipolar direct current power distribution network Pending CN115021227A (en)

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