CN112751330A - Low-voltage direct-current continuous power supply system and control method thereof - Google Patents

Low-voltage direct-current continuous power supply system and control method thereof Download PDF

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Publication number
CN112751330A
CN112751330A CN202110034205.1A CN202110034205A CN112751330A CN 112751330 A CN112751330 A CN 112751330A CN 202110034205 A CN202110034205 A CN 202110034205A CN 112751330 A CN112751330 A CN 112751330A
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voltage
low
current
direct
short
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CN112751330B (en
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王一
王继慷
刘树
操丰梅
梅红明
王皆庆
游涛
王立超
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Beijing Sifang Project Co ltd
Beijing Sifang Automation Co Ltd
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Beijing Sifang Project Co ltd
Beijing Sifang Automation Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/109—Scheduling or re-scheduling the operation of the DC sources in a particular order, e.g. connecting or disconnecting the sources in sequential, alternating or in subsets, to meet a given demand

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Abstract

A low-voltage direct current continuous power supply system and a control method thereof are disclosed, the system comprises a direct current transformer, a low-voltage energy storage device and a low-voltage direct current limiter, the high-voltage side of the direct current transformer is connected with the medium-voltage side of a direct current distribution network, the low-voltage side of the direct current transformer is connected with the input end of the low-voltage energy storage device and the input section of the low-voltage direct current limiter, the output end of the low-voltage direct current limiter is connected with a low-voltage direct current bus, and a low-voltage; and detecting the operation condition of the direct current power distribution network in real time according to the current and the voltage of the system, and switching the control mode of the low-voltage direct current continuous power supply system according to the real-time detection result. The low-voltage direct-current distribution system is guaranteed to rapidly clear faults and continuously supply power when faults occur on the medium-voltage side and the low-voltage side, the possibility of power failure of a low-voltage direct-current load is reduced to the minimum when the faults occur, the power supply reliability of low-voltage direct current is effectively improved, and the continuous power supply requirement of the low-voltage direct-current distribution network load is met.

Description

Low-voltage direct-current continuous power supply system and control method thereof
Technical Field
The invention relates to the technical field of reliable power supply in a low-voltage direct-current power distribution system, in particular to a low-voltage direct-current continuous power supply system and a control method thereof.
Background
The urban direct-current distribution network is connected with a medium-voltage direct-current distribution network and a low-voltage direct-current load through a direct-current transformer. The low-voltage direct-current loads in the city comprise a data center, an office building, a charging pile, a residential building and the like, and the multi-path loads are connected in parallel to a low-voltage direct-current bus through a load switch to form a low-voltage direct-current power utilization network.
The direct current distribution network short-circuit fault is larger in current and wide in spread range compared with the alternating current distribution network fault, and once the fault occurs, the whole direct current distribution network is easily powered off. The low-voltage direct-current power system has a high possibility of failure due to the fact that the types and the number of connected loads are large. For sensitive direct current loads such as a data center and the like, the requirement on the continuity of power supply is high, and the low-voltage power supply interruption caused by the fault of a medium-voltage direct current power distribution network can also cause bad influence.
In the prior art, a direct current power distribution network fault protection coping scheme generally adopts a direct current circuit breaker, and fault isolation is performed when a fault occurs. On one hand, the direct current circuit breaker is high in manufacturing cost, and meanwhile, the fault processing mode can cause that the system is interrupted once each-level branch circuit in the urban low-voltage power distribution network has a short-circuit fault, so that although equipment in the system is protected, the reliability and the continuity of power supply of a user are greatly reduced, and the direct current circuit breaker cannot be applied to a data center and other occasions needing continuous power supply.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a low-voltage direct-current continuous power supply system and a control method thereof, which can ensure that a low-voltage direct-current power distribution system can quickly clear faults and continuously supply power when the medium-voltage side and the low-voltage side have faults, and meet the load continuous power supply requirement of a low-voltage direct-current power distribution network.
The invention adopts the following technical scheme.
The control method of the low-voltage direct-current continuous power supply system comprises the following steps:
step 1, acquiring inlet end current and voltage of a direct current transformer, inlet end current and voltage of a low-voltage energy storage device and outlet end current and voltage of a direct current limiter in a low-voltage direct current continuous power supply system in a current sampling period;
step 2, according to the collected current and voltage at the inlet end of the direct current transformer and the collected current and voltage at the outlet end of the direct current limiter, the operation condition of the direct current distribution network is detected in real time, and the method comprises the following steps: medium-voltage side short-circuit fault, medium-voltage side short-circuit fault recovery, low-voltage side short-circuit fault recovery and steady-state operation; switching the control mode of the low-voltage direct-current continuous power supply system according to the real-time detection result;
and 3, under the steady-state operation condition of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a low-voltage direct current bus voltage control mode, the low-voltage direct current limiter operates in a bypass mode, and the low-voltage energy storage device operates in a hot standby mode;
and 4, under the working condition of short circuit fault of the medium-voltage side of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a high-voltage side capacitor voltage control mode, and the low-voltage direct current limiter operates in a bypass mode; controlling the low-voltage energy storage device to operate in a low-voltage direct-current bus voltage control mode according to the collected current and voltage at the inlet end of the low-voltage energy storage device;
and 5, under the condition that the short-circuit fault of the medium-voltage side of the direct-current power distribution network is recovered, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a high-voltage side capacitor voltage control mode, the low-voltage direct current limiter operates in a bypass mode, and the low-voltage energy storage device operates in a hot standby mode;
and 6, under the working condition of short circuit fault of the low-voltage side of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the DC transformer operates in a low-voltage DC bus voltage control mode, the low-voltage DC current limiter operates in a current limiting mode, and the low-voltage energy storage device operates in a hot standby mode;
and 7, operating the low-voltage direct-current continuous power supply system in a control mode under a steady-state operation condition under the low-voltage side short-circuit fault recovery condition of the direct-current power distribution network.
Preferably, the first and second electrodes are formed of a metal,
the step 2 comprises the following steps:
step 2.1, in the current sampling period, comparing the voltage at the inlet end of the direct current transformer with a medium-voltage short-circuit voltage threshold value and comparing the current at the inlet end of the direct current transformer with a medium-voltage short-circuit current threshold value respectively, and when a medium-voltage side short-circuit fault occurs, satisfying the following relational expression:
UA<UMFand IA>IMF
In the formula (I), the compound is shown in the specification,
UAthe voltage at the inlet terminal of the dc transformer is shown,
UMFthe medium-voltage short-circuit voltage threshold value is represented as 80 percent of the rated voltage of the medium-voltage system of the direct-current distribution network,
IArepresenting the inlet side current of the dc transformer,
IMFthe medium-voltage short-circuit current threshold value is represented and is 1.3 times of the rated current of the medium-voltage system of the direct-current power distribution network;
step 2.2, in the current sampling period, comparing the voltage at the outlet end of the direct current limiter with a low-voltage short-circuit voltage threshold value and comparing the current at the outlet end of the direct current limiter with a low-voltage short-circuit current threshold value respectively, and when a low-voltage side short-circuit fault occurs, satisfying the following relational expression:
UC<ULFand IC>ILF
In the formula (I), the compound is shown in the specification,
UCthe voltage at the outlet of the dc current limiter is shown,
ULFthe low-voltage short-circuit voltage threshold value is represented and is 80 percent of the rated voltage of the low-voltage system of the direct-current distribution network,
ICrepresenting the outlet end current of the dc current limiter,
ILFthe low-voltage short-circuit current threshold value is represented and is 1.3 times of the rated current of the low-voltage system of the direct-current power distribution network;
step 2.3, detecting a medium-voltage side short-circuit fault in the last sampling period, comparing the voltage of the inlet end of the direct-current transformer with a medium-voltage short-circuit recovery voltage threshold value in the current sampling period, and when the medium-voltage short-circuit fault is recovered, satisfying the following relational expression:
UA>UMFO
in the formula (I), the compound is shown in the specification,
UAthe voltage at the inlet terminal of the dc transformer is shown,
UMFOthe medium-voltage short circuit recovery voltage threshold is represented and is 90% of the rated voltage of the medium-voltage system of the direct-current power distribution network;
step 2.4, detecting a low-voltage side short-circuit fault in the last sampling period, comparing the current at the outlet end of the direct current limiter with a low-voltage short-circuit recovery current threshold value in the current sampling period, and when the low-voltage short-circuit fault is recovered, satisfying the following relational expression:
IC<ILFO
in the formula (I), the compound is shown in the specification,
ICrepresenting the outlet end current of the dc current limiter,
ILFOthe low-voltage short circuit recovery current threshold is represented and is 50% of the rated current of the low-voltage system of the direct-current distribution network.
Preferably, the first and second electrodes are formed of a metal,
step 2.1 also includes:
detecting the short-circuit fault of the medium-voltage side in the current sampling period, comparing the inlet end voltage of the low-voltage energy storage device with an input voltage threshold value and the inlet end current of the low-voltage energy storage device with the rated current of the low-voltage side, and inputting the low-voltage energy storage device when the following relational expression is satisfied:
UB<ULFand IB≤ILMF
In the formula (I), the compound is shown in the specification,
UBrepresenting the voltage at the inlet end of the low voltage energy storage device,
ULFthe input voltage threshold value is represented as 80% of the rated voltage of the low-voltage system of the direct-current distribution network,
IBrepresenting the inlet side current of the low voltage energy storage device,
ILMFand represents the rated current value of the low-voltage side of the direct-current transformer.
Preferably, the first and second electrodes are formed of a metal,
when the direct current transformer operates in a low-voltage direct current bus voltage control mode, controlling the voltage of the low-voltage direct current bus to be 0.9-1.1 times of the rated voltage value of the low-voltage direct current bus;
and when the direct current transformer operates in a high-voltage side capacitor voltage control mode, controlling the voltage of the high-voltage direct current capacitor to be 0.9 times of the voltage rated value of the high-voltage direct current capacitor.
Preferably, the first and second electrodes are formed of a metal,
when the low-voltage energy storage device operates in a hot standby mode, the low-voltage direct-current bus charges the low-voltage energy storage device;
and when the low-voltage energy storage device operates in a low-voltage direct-current bus voltage control mode, controlling the voltage of the low-voltage direct-current bus to be 0.9-1.1 times of the rated voltage value of the low-voltage direct-current bus, and supplying power to the low-voltage direct-current bus.
Preferably, the first and second electrodes are formed of a metal,
when the low-voltage direct current limiter operates in a bypass mode, the low-voltage direct current limiter is in a direct-through state;
when the low-voltage direct current limiter operates in a current limiting mode, the current of the low-voltage direct current bus is limited to be not more than 1.2 times of the rated current of a low-voltage system of the direct current distribution network.
Preferably, the first and second electrodes are formed of a metal,
the voltage of the low-voltage direct-current bus is controlled by voltage-power droop, and the following relational expression is satisfied:
E＝E0+kEP×P
in the formula (I), the compound is shown in the specification,
e is the voltage target value, and E is the voltage target value,
E0in order to obtain the droop control reference value,
kEPin order to obtain the sag factor,
and P is the DC output power value.
A low-voltage direct-current continuous power supply system comprises a direct-current transformer, a low-voltage energy storage device and a low-voltage direct-current limiter;
the high-voltage side of the direct-current transformer is connected to the medium-voltage side of the direct-current distribution network, the low-voltage side of the direct-current transformer is connected with the input end of the low-voltage energy storage device and the input section of the low-voltage direct-current limiter, the output end of the low-voltage direct-current limiter is connected with a low-voltage direct-current bus, and a low-voltage load is connected to the low-voltage.
Preferably, the first and second electrodes are formed of a metal,
the direct current transformer comprises N cascaded submodules, and a single submodule comprises: the high-voltage side isolation switch module, the high-voltage side active bridge module, the low-voltage side active bridge module and the low-voltage side isolation switch module are arranged in the transformer substation;
each submodule is connected in series at the high-voltage side isolating switch module to form the high-voltage side of the direct-current transformer, and each submodule is connected in parallel at the low-voltage side isolating switch module to form the low-voltage side of the direct-current transformer;
under the steady-state operation working condition and the low-voltage side short-circuit fault working condition of the direct-current power distribution network, the power direction of the direct-current transformer is that the high-voltage side flows to the low-voltage side;
under the condition of short circuit fault of the medium-voltage side of the direct-current power distribution network, the high-voltage side isolating switch module of the direct-current transformer is switched off, and the power direction of the direct-current transformer is that the low-voltage side flows to the high-voltage side.
Preferably, the first and second electrodes are formed of a metal,
the low-voltage energy storage device comprises an energy storage element and a DC-DC converter;
under the steady-state operation working condition of the direct-current power distribution network and the low-voltage side short-circuit fault working condition, the power direction of the low-voltage energy storage device is from the low-voltage direct-current bus to the low-voltage energy storage device;
under the working condition of short circuit fault at the medium-voltage side of the direct-current power distribution network, the power direction of the low-voltage energy storage device is from the low-voltage energy storage device to the low-voltage direct-current bus.
Compared with the prior art, the method has the advantages that the faults can be rapidly cleared and power can be continuously supplied when the medium-voltage side and the low-voltage side of the low-voltage direct-current power distribution system have faults, the possibility of power failure of a low-voltage direct-current load when the faults occur is reduced to the minimum, the power supply reliability of the low-voltage direct current is effectively improved, and the continuous power supply requirement of the low-voltage direct-current power distribution network load is met.
Drawings
FIG. 1 is a flow chart of a control method of a low-voltage DC continuous power supply system according to the present invention;
FIG. 2 is a flow chart of the detection of the short-circuit fault at the medium-voltage side of the control method of the low-voltage DC continuous power supply system according to the present invention;
FIG. 3 is a flow chart of the low-voltage side short-circuit fault detection of the control method of the low-voltage DC continuous power supply system according to the present invention;
FIG. 4 is a block diagram of the low voltage DC continuous power supply system of the present invention;
FIG. 5 is a topology diagram of a DC transformer in the low voltage DC continuous power supply system according to the present invention;
fig. 6 is a topological diagram of a low-voltage dc current limiter in the low-voltage dc continuous power supply system according to the present invention.
Detailed Description
The present application is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present application is not limited thereby.
Referring to fig. 1, a method for controlling a low-voltage dc continuous power supply system includes the following steps:
step 1, in a current sampling period, acquiring inlet end current and voltage of a direct current transformer, inlet end current and voltage of a low-voltage energy storage device and outlet end current and voltage of a direct current limiter in a low-voltage direct current continuous power supply system.
Step 2, according to the collected current and voltage at the inlet end of the direct current transformer and the collected current and voltage at the outlet end of the direct current limiter, the operation condition of the direct current distribution network is detected in real time, and the method comprises the following steps: medium-voltage side short-circuit fault, medium-voltage side short-circuit fault recovery, low-voltage side short-circuit fault recovery and steady-state operation; and switching the control mode of the low-voltage direct-current continuous power supply system according to the real-time detection result.
In particular, the amount of the solvent to be used,
the step 2 comprises the following steps:
step 2.1, in the current sampling period, comparing the voltage at the inlet end of the direct current transformer with a medium-voltage short-circuit voltage threshold value and comparing the current at the inlet end of the direct current transformer with a medium-voltage short-circuit current threshold value respectively, and when a medium-voltage side short-circuit fault occurs, satisfying the following relational expression:
UA<UMFand IA>IMF
In the formula (I), the compound is shown in the specification,
UAthe voltage at the inlet terminal of the dc transformer is shown,
UMFthe medium-voltage short-circuit voltage threshold value is represented as 80 percent of the rated voltage of the medium-voltage system of the direct-current distribution network,
IArepresenting the inlet side current of the dc transformer,
IMFand the medium-voltage short-circuit current threshold is represented and is 1.3 times of the rated current of the medium-voltage system of the direct-current distribution network.
Step 2.1 also includes:
detecting the short-circuit fault of the medium-voltage side in the current sampling period, comparing the inlet end voltage of the low-voltage energy storage device with an input voltage threshold value and the inlet end current of the low-voltage energy storage device with the rated current of the low-voltage side, and inputting the low-voltage energy storage device when the following relational expression is satisfied:
UB<ULFand IB≤ILMF
In the formula (I), the compound is shown in the specification,
UBrepresenting the voltage at the inlet end of the low voltage energy storage device,
ULFthe input voltage threshold value is represented as 80% of the rated voltage of the low-voltage system of the direct-current distribution network,
IBrepresenting the inlet side current of the low voltage energy storage device,
ILMFand represents the rated current value of the low-voltage side of the direct-current transformer.
Step 2.2, in the current sampling period, comparing the voltage at the outlet end of the direct current limiter with a low-voltage short-circuit voltage threshold value and comparing the current at the outlet end of the direct current limiter with a low-voltage short-circuit current threshold value respectively, and when a low-voltage side short-circuit fault occurs, satisfying the following relational expression:
UC<ULFand IC>ILF
In the formula (I), the compound is shown in the specification,
UCthe voltage at the outlet of the dc current limiter is shown,
ULFthe low-voltage short-circuit voltage threshold value is represented and is 80 percent of the rated voltage of the low-voltage system of the direct-current distribution network,
ICrepresenting the outlet end current of the dc current limiter,
ILFand the low-voltage short-circuit current threshold is represented and is 1.3 times of the rated current of the low-voltage system of the direct-current distribution network.
Step 2.3, detecting a medium-voltage side short-circuit fault in the last sampling period, comparing the voltage of the inlet end of the direct-current transformer with a medium-voltage short-circuit recovery voltage threshold value in the current sampling period, and when the medium-voltage short-circuit fault is recovered, satisfying the following relational expression:
UA>UMFO
in the formula (I), the compound is shown in the specification,
UAthe voltage at the inlet terminal of the dc transformer is shown,
UMFOthe medium-voltage short circuit recovery voltage threshold is represented and is 90% of the rated voltage of the medium-voltage system of the direct-current distribution network.
Step 2.4, detecting a low-voltage side short-circuit fault in the last sampling period, comparing the current at the outlet end of the direct current limiter with a low-voltage short-circuit recovery current threshold value in the current sampling period, and when the low-voltage short-circuit fault is recovered, satisfying the following relational expression:
IC<ILFO
in the formula (I), the compound is shown in the specification,
ICrepresenting the outlet end current of the dc current limiter,
ILFOthe low-voltage short circuit recovery current threshold is represented and is 50% of the rated current of the low-voltage system of the direct-current distribution network.
And 3, under the steady-state operation condition of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a low-voltage direct current bus voltage control mode, the low-voltage direct current limiter operates in a bypass mode, and the low-voltage energy storage device operates in a hot standby mode.
In particular, the amount of the solvent to be used,
when the direct current transformer operates in a low-voltage direct current bus voltage control mode, controlling the voltage of the low-voltage direct current bus to be 0.9-1.1 times of the rated voltage value of the low-voltage direct current bus;
when the low-voltage direct current limiter operates in a bypass mode, the low-voltage direct current limiter is in a direct-through state;
when the low-voltage energy storage device operates in the hot standby mode, the low-voltage direct-current bus charges the low-voltage energy storage device.
And 4, under the working condition of short circuit fault of the medium-voltage side of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a high-voltage side capacitor voltage control mode, and the low-voltage direct current limiter operates in a bypass mode; and controlling the low-voltage energy storage device to operate in a low-voltage direct-current bus voltage control mode according to the collected current and voltage at the inlet end of the low-voltage energy storage device.
In particular, the amount of the solvent to be used,
when the direct current transformer operates in a high-voltage side capacitor voltage control mode, controlling the voltage of the high-voltage direct current capacitor to be 0.9 times of the voltage rated value of the high-voltage direct current capacitor;
when the low-voltage direct current limiter operates in a bypass mode, the low-voltage direct current limiter is in a direct-through state;
and when the low-voltage energy storage device operates in a low-voltage direct-current bus voltage control mode, controlling the voltage of the low-voltage direct-current bus to be 0.9-1.1 times of the rated voltage value of the low-voltage direct-current bus, and supplying power to the low-voltage direct-current bus.
And 5, under the condition that the short-circuit fault of the medium-voltage side of the direct-current power distribution network is recovered, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a high-voltage side capacitor voltage control mode, and the low-voltage direct current limiter operates in a bypass mode; and controlling the low-voltage energy storage device to operate in a hot standby mode according to the collected voltage of the inlet end of the direct-current transformer.
As shown in fig. 2, in the operation process of the low-voltage direct-current continuous power supply system, the occurrence of the medium-voltage side power grid short-circuit fault is detected, and at this time, the control method switches the control mode of the power supply system in time, that is, the steady-state operation condition control mode in step 3 is switched to the medium-voltage side short-circuit fault condition control mode in step 4; at the moment, the power requirement of the low-voltage direct-current bus load is met by the low-voltage energy storage equipment, and the power supply interruption of the power load cannot be caused.
And (3) detecting the recovery of the medium-voltage side short-circuit fault in the medium-voltage side power grid short-circuit fault process of the low-voltage direct-current continuous power supply system, and switching the control mode of the power supply system in time by the control method at the moment, namely switching the medium-voltage side short-circuit fault working condition control mode in the step (4) to the steady-state operation working condition control mode according to the description in the step (5).
In the preferred embodiment, as shown in fig. 2, when the medium-voltage side short-circuit fault is detected to be recovered in the current sampling period, the voltage at the inlet end of the dc transformer is compared with the rated voltage of the medium-voltage system in the dc distribution network, and the low-voltage energy storage device is exited when the following relational expression is satisfied:
|UA-UM|<0.03p.u.
in the formula (I), the compound is shown in the specification,
UMand the rated voltage of a low-voltage system of the direct-current distribution network is represented.
And 6, under the working condition of short circuit fault of the low-voltage side of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a low-voltage direct current bus voltage control mode, the low-voltage direct current limiter operates in a current limiting mode, and the low-voltage energy storage device operates in a hot standby mode.
In particular, the amount of the solvent to be used,
when the direct current transformer operates in a low-voltage direct current bus voltage control mode, controlling the voltage of the low-voltage direct current bus to be 0.9-1.1 times of the rated voltage value of the low-voltage direct current bus;
when the low-voltage direct current limiter operates in a current limiting mode, the current of a low-voltage direct current bus is limited to be not more than 1.2 times of the rated current of a low-voltage system of a direct current distribution network;
when the low-voltage energy storage device operates in the hot standby mode, the low-voltage direct-current bus charges the low-voltage energy storage device.
And 7, operating the low-voltage direct-current continuous power supply system in a control mode under a steady-state operation condition under the low-voltage side short-circuit fault recovery condition of the direct-current power distribution network.
As shown in fig. 3, in the operation process of the low-voltage dc continuous power supply system, the occurrence of the short-circuit fault of the low-voltage side power grid is detected, and at this time, the control method switches the control mode of the power supply system in time, that is, the control mode is switched from the steady-state operation condition control mode in step 3 to the low-voltage side short-circuit fault condition control mode in step 6; at the moment, the low-voltage direct-current bus is continuously supplied to the load through the current-limiting and voltage-limiting control, so that the power supply interruption of the electric load can not be caused.
And (3) detecting the recovery of the low-voltage side short-circuit fault in the low-voltage side power grid short-circuit fault process of the low-voltage direct-current continuous power supply system, and switching the control mode of the power supply system in time by the control method, namely switching the low-voltage side short-circuit fault working condition control mode in the step (6) to a steady-state operation working condition control mode according to the description in the step (7).
In particular, the amount of the solvent to be used,
the voltage of the low-voltage direct-current bus is controlled by voltage-power droop, and the following relational expression is satisfied:
E＝E0+kEP×P
in the formula (I), the compound is shown in the specification,
e is the voltage target value, and E is the voltage target value,
E0in order to obtain the droop control reference value,
kEPin order to obtain the sag factor,
and P is the DC output power value.
Referring to fig. 4, a low-voltage dc continuous power supply system includes a dc transformer, a low-voltage energy storage device, and a low-voltage dc current limiter.
The high-voltage side of the direct-current transformer is connected to the medium-voltage side of the direct-current distribution network, the low-voltage side of the direct-current transformer is connected with the input end of the low-voltage energy storage device and the input section of the low-voltage direct-current limiter, the output end of the low-voltage direct-current limiter is connected with a low-voltage direct-current bus, and a low-voltage load is connected to the low-voltage.
In particular, the amount of the solvent to be used,
as shown in fig. 5, the dc transformer includes N cascaded sub-modules, and a single sub-module includes: high side isolator module S1, high side active bridge module, low side isolator module S2.
The submodules are connected in series at a high-voltage side isolating switch module S1 to form the high-voltage side of the direct-current transformer, and the submodules are connected in parallel at a low-voltage side isolating switch module S2 to form the low-voltage side of the direct-current transformer.
Under the steady-state operation working condition of the direct-current distribution network and the short-circuit fault working condition of the low-voltage side, the power direction of the direct-current transformer is that the high-voltage side flows to the low-voltage side.
Under the condition of short circuit fault of the medium-voltage side of the direct-current power distribution network, the high-voltage side isolating switch module of the direct-current transformer is switched off, and the power direction of the direct-current transformer is that the low-voltage side flows to the high-voltage side.
In the preferred embodiment, the dc transformer has three operation modes: the system comprises a low-voltage direct current bus voltage control mode, a high-voltage side capacitor voltage control mode and a shutdown mode;
under the high-voltage side capacitor voltage control mode, a high-voltage side isolation switch module S1 of the direct current transformer is in an on-off state, and isolation of the direct current transformer from a medium-voltage side short-circuit fault is achieved;
and in the shutdown mode, the direct current transformer is locked and shut down, so that the isolation of the direct current transformer and the direct current distribution network system is realized.
In particular, the amount of the solvent to be used,
the low-voltage energy storage device comprises an energy storage element and a DC-DC converter;
it is to be noted that those skilled in the art select the energy storage elements of the low-voltage energy storage device and the DC-DC converter with different topologies according to actual situations; energy storage elements including, but not limited to, batteries, supercapacitors; DC-DC converters including, but not limited to, Boost-configuration converters, Buck-Boost-configuration converters; the choice in the preferred embodiment is a non-limiting preferred choice.
Under the steady-state operation working condition of the direct-current power distribution network and the low-voltage side short-circuit fault working condition, the power direction of the low-voltage energy storage device is from the low-voltage direct-current bus to the low-voltage energy storage device;
under the working condition of short circuit fault at the medium-voltage side of the direct-current power distribution network, the power direction of the low-voltage energy storage device is from the low-voltage energy storage device to the low-voltage direct-current bus.
In the preferred embodiment, the low-voltage energy storage device has three operating modes: the method comprises the following steps of (1) controlling the voltage of a low-voltage direct current bus, and performing a hot standby mode and a shutdown mode;
under the voltage control mode of the low-voltage direct-current bus, the low-voltage energy storage device supplies power to the low-voltage direct-current bus;
in the hot standby mode, the low-voltage direct-current bus charges the low-voltage energy storage device;
and in the shutdown mode, the low-voltage energy storage device is locked and shut down, so that the low-voltage energy storage device is isolated from the direct-current distribution network system.
As shown in fig. 6, the low-voltage dc current limiter has two operation modes: a bypass mode and a current limit mode;
in the bypass mode, the switching tubes of the low-voltage direct current limiter are all in conduction, so that the low-voltage direct current limiter is in a straight-through state in a system;
in the current limiting mode, a switching tube of the low-voltage direct current limiter is alternately conducted under PWM control, and the current limiter adjusts the PWM duty ratio according to the current magnitude, so that the current magnitude flowing through the current limiter is limited.
Compared with the prior art, the method has the advantages that the faults can be rapidly cleared and power can be continuously supplied when the medium-voltage side and the low-voltage side of the low-voltage direct-current power distribution system have faults, the possibility of power failure of a low-voltage direct-current load when the faults occur is reduced to the minimum, the power supply reliability of the low-voltage direct current is effectively improved, and the continuous power supply requirement of the low-voltage direct-current power distribution network load is met.
The present applicant has described and illustrated embodiments of the present invention in detail with reference to the accompanying drawings, but it should be understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for limiting the scope of the present invention, and on the contrary, any improvement or modification made based on the spirit of the present invention should fall within the scope of the present invention.

Claims (10)

1. A control method of a low-voltage direct-current continuous power supply system is characterized in that,
the control method comprises the following steps:
step 1, acquiring inlet end current and voltage of a direct current transformer, inlet end current and voltage of a low-voltage energy storage device and outlet end current and voltage of a direct current limiter in a low-voltage direct current continuous power supply system in a current sampling period;
step 2, according to the collected current and voltage at the inlet end of the direct current transformer and the collected current and voltage at the outlet end of the direct current limiter, the operation condition of the direct current distribution network is detected in real time, and the method comprises the following steps: medium-voltage side short-circuit fault, medium-voltage side short-circuit fault recovery, low-voltage side short-circuit fault recovery and steady-state operation; switching the control mode of the low-voltage direct-current continuous power supply system according to the real-time detection result;
and 3, under the steady-state operation condition of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a low-voltage direct current bus voltage control mode, the low-voltage direct current limiter operates in a bypass mode, and the low-voltage energy storage device operates in a hot standby mode;
and 4, under the working condition of short circuit fault of the medium-voltage side of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a high-voltage side capacitor voltage control mode, and the low-voltage direct current limiter operates in a bypass mode; controlling the low-voltage energy storage device to operate in a low-voltage direct-current bus voltage control mode according to the collected current and voltage at the inlet end of the low-voltage energy storage device;
and 5, under the condition that the short-circuit fault of the medium-voltage side of the direct-current power distribution network is recovered, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the direct current transformer operates in a high-voltage side capacitor voltage control mode, the low-voltage direct current limiter operates in a bypass mode, and the low-voltage energy storage device operates in a hot standby mode;
and 6, under the working condition of short circuit fault of the low-voltage side of the direct-current power distribution network, the control mode of the low-voltage direct-current continuous power supply system comprises the following steps: the DC transformer operates in a low-voltage DC bus voltage control mode, the low-voltage DC current limiter operates in a current limiting mode, and the low-voltage energy storage device operates in a hot standby mode;
and 7, operating the low-voltage direct-current continuous power supply system in a control mode under a steady-state operation condition under the low-voltage side short-circuit fault recovery condition of the direct-current power distribution network.
2. The control method of a low-voltage DC continuous power supply system according to claim 1,
the step 2 comprises the following steps:
step 2.1, in the current sampling period, comparing the voltage at the inlet end of the direct current transformer with a medium-voltage short-circuit voltage threshold value and comparing the current at the inlet end of the direct current transformer with a medium-voltage short-circuit current threshold value respectively, and when a medium-voltage side short-circuit fault occurs, satisfying the following relational expression:
UA＜UMFand IA＞IMF
In the formula (I), the compound is shown in the specification,
UAthe voltage at the inlet terminal of the dc transformer is shown,
UMFthe medium-voltage short-circuit voltage threshold value is represented as 80 percent of the rated voltage of the medium-voltage system of the direct-current distribution network,
IArepresenting the inlet side current of the dc transformer,
IMFthe medium-voltage short-circuit current threshold value is represented and is 1.3 times of the rated current of the medium-voltage system of the direct-current power distribution network;
step 2.2, in the current sampling period, comparing the voltage at the outlet end of the direct current limiter with a low-voltage short-circuit voltage threshold value and comparing the current at the outlet end of the direct current limiter with a low-voltage short-circuit current threshold value respectively, and when a low-voltage side short-circuit fault occurs, satisfying the following relational expression:
UC＜ULFand IC＞ILF
In the formula (I), the compound is shown in the specification,
UCthe voltage at the outlet of the dc current limiter is shown,
ULFthe low-voltage short-circuit voltage threshold value is represented and is 80 percent of the rated voltage of the low-voltage system of the direct-current distribution network,
ICrepresenting the outlet end current of the dc current limiter,
ILFthe low-voltage short-circuit current threshold value is represented and is 1.3 times of the rated current of the low-voltage system of the direct-current power distribution network;
step 2.3, detecting a medium-voltage side short-circuit fault in the last sampling period, comparing the voltage of the inlet end of the direct-current transformer with a medium-voltage short-circuit recovery voltage threshold value in the current sampling period, and when the medium-voltage short-circuit fault is recovered, satisfying the following relational expression:
UA＞UMFO
in the formula (I), the compound is shown in the specification,
UAthe voltage at the inlet terminal of the dc transformer is shown,
UMFOthe medium-voltage short circuit recovery voltage threshold is represented and is 90% of the rated voltage of the medium-voltage system of the direct-current power distribution network;
step 2.4, detecting a low-voltage side short-circuit fault in the last sampling period, comparing the current at the outlet end of the direct current limiter with a low-voltage short-circuit recovery current threshold value in the current sampling period, and when the low-voltage short-circuit fault is recovered, satisfying the following relational expression:
IC＜ILFO
in the formula (I), the compound is shown in the specification,
JCrepresenting the outlet end current of the dc current limiter,
ILFOthe low-voltage short circuit recovery current threshold is represented and is 50% of the rated current of the low-voltage system of the direct-current distribution network.
3. The control method of a low-voltage DC continuous power supply system according to claim 2,
step 2.1 also includes:
detecting the short-circuit fault of the medium-voltage side in the current sampling period, comparing the inlet end voltage of the low-voltage energy storage device with an input voltage threshold value and the inlet end current of the low-voltage energy storage device with the rated current of the low-voltage side, and inputting the low-voltage energy storage device when the following relational expression is satisfied:
UB＜ULFand IB≤ILMF
In the formula (I), the compound is shown in the specification,
UBrepresenting the voltage at the inlet end of the low voltage energy storage device,
ULFthe input voltage threshold value is represented as 80% of the rated voltage of the low-voltage system of the direct-current distribution network,
IBrepresenting the inlet side current of the low voltage energy storage device,
ILMFand represents the rated current value of the low-voltage side of the direct-current transformer.
4. The control method of a low-voltage DC continuous power supply system according to claim 1,
when the direct current transformer operates in a low-voltage direct current bus voltage control mode, controlling the voltage of the low-voltage direct current bus to be 0.9-1.1 times of the rated voltage value of the low-voltage direct current bus;
and when the direct current transformer operates in a high-voltage side capacitor voltage control mode, controlling the voltage of the high-voltage direct current capacitor to be 0.9 times of the voltage rated value of the high-voltage direct current capacitor.
5. The control method of a low-voltage DC continuous power supply system according to claim 1,
when the low-voltage energy storage device operates in a hot standby mode, the low-voltage direct-current bus charges the low-voltage energy storage device;
and when the low-voltage energy storage device operates in a low-voltage direct-current bus voltage control mode, controlling the voltage of the low-voltage direct-current bus to be 0.9-1.1 times of the rated voltage value of the low-voltage direct-current bus, and supplying power to the low-voltage direct-current bus.
6. The control method of a low-voltage DC continuous power supply system according to claim 1,
when the low-voltage direct current limiter operates in a bypass mode, the low-voltage direct current limiter is in a direct-through state;
when the low-voltage direct current limiter operates in a current limiting mode, the current of the low-voltage direct current bus is limited to be not more than 1.2 times of the rated current of a low-voltage system of the direct current distribution network.
7. The control method of a low-voltage DC continuous power supply system according to claim 4 and 5,
the voltage of the low-voltage direct current bus is controlled by voltage-power droop, and the following relational expression is satisfied:
E＝E0+kEP×P
in the formula (I), the compound is shown in the specification,
e is the voltage target value, and E is the voltage target value,
E0in order to obtain the droop control reference value,
kEPin order to obtain the sag factor,
and P is the DC output power value.
8. The low voltage DC continuous power supply system of the control method of the low voltage DC continuous power supply system according to any one of claims 1 to 7,
the low-voltage direct-current continuous power supply system comprises a direct-current transformer, a low-voltage energy storage device and a low-voltage direct-current limiter;
the high-voltage side of the direct-current transformer is connected to the medium-voltage side of the direct-current distribution network, the low-voltage side of the direct-current transformer is connected with the input end of the low-voltage energy storage device and the input section of the low-voltage direct-current limiter, the output end of the low-voltage direct-current limiter is connected with a low-voltage direct-current bus, and a low-voltage load is connected to the low-voltage direct.
9. The low voltage DC continuous power supply system according to claim 8,
the direct current transformer comprises N cascaded sub-modules, and a single sub-module comprises: the high-voltage side isolation switch module, the high-voltage side active bridge module, the low-voltage side active bridge module and the low-voltage side isolation switch module are arranged in the transformer substation;
each submodule is connected in series at the high-voltage side isolating switch module to form the high-voltage side of the direct-current transformer, and each submodule is connected in parallel at the low-voltage side isolating switch module to form the low-voltage side of the direct-current transformer;
under the steady-state operation working condition and the low-voltage side short-circuit fault working condition of the direct-current power distribution network, the power direction of the direct-current transformer is that the high-voltage side flows to the low-voltage side;
under the condition of short circuit fault of the medium-voltage side of the direct-current power distribution network, the high-voltage side isolating switch module of the direct-current transformer is switched off, and the power direction of the direct-current transformer is that the low-voltage side flows to the high-voltage side.
10. The low voltage DC continuous power supply system according to claim 8,
the low-voltage energy storage device comprises an energy storage element and a DC-DC converter;
under the steady-state operation working condition of the direct-current power distribution network and the low-voltage side short-circuit fault working condition, the power direction of the low-voltage energy storage device is from the low-voltage direct-current bus to the low-voltage energy storage device;
under the working condition of short circuit fault at the medium-voltage side of the direct-current power distribution network, the power direction of the low-voltage energy storage device is from the low-voltage energy storage device to the low-voltage direct-current bus.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017202165A1 (en) * 2016-05-26 2017-11-30 珠海格力电器股份有限公司 Method of identifying fault in dc microgrid power line, device, and dc microgrid system
CN108539776A (en) * 2018-05-10 2018-09-14 国网江苏省电力有限公司徐州供电分公司 One kind being used for low pressure flexibility supplying power allocation system coordination control method
CN108879623A (en) * 2018-06-13 2018-11-23 南京南瑞继保电气有限公司 A kind of multi-voltage grade DC grid system and control guard method
CN110021925A (en) * 2019-05-05 2019-07-16 国网江苏省电力有限公司 DC power-supply system and its control method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017202165A1 (en) * 2016-05-26 2017-11-30 珠海格力电器股份有限公司 Method of identifying fault in dc microgrid power line, device, and dc microgrid system
CN108539776A (en) * 2018-05-10 2018-09-14 国网江苏省电力有限公司徐州供电分公司 One kind being used for low pressure flexibility supplying power allocation system coordination control method
CN108879623A (en) * 2018-06-13 2018-11-23 南京南瑞继保电气有限公司 A kind of multi-voltage grade DC grid system and control guard method
CN110021925A (en) * 2019-05-05 2019-07-16 国网江苏省电力有限公司 DC power-supply system and its control method

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