CN214707152U

CN214707152U - Direct current fault current limiter

Info

Publication number: CN214707152U
Application number: CN202121061457.5U
Authority: CN
Inventors: 李春鹏; 贾科
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-05-18
Filing date: 2021-05-18
Publication date: 2021-11-12
Anticipated expiration: 2031-05-18

Abstract

The utility model relates to a direct current fault current limiter, including a plurality of current-limiting branch roads that connect in parallel each other, controller and set up the current measurement sensor on the output, every current-limiting branch road is provided with solid state switch respectively and the current-limiting resistance who establishes ties with solid state switch, and the current-limiting resistance of each current-limiting branch road is different, controller communication connection current measurement sensor and the solid state switch of every current-limiting branch road of connection control. The utility model discloses can install the direct current side of locating DC power or transverter, through setting up the different current-limiting branch road of a plurality of current-limiting resistance values, can switch over each current-limiting branch road according to output current change, make output current remain throughout the electric current within range of settlement, the electric current rises to too high when can preventing the trouble from taking place, can last the fault current who provides low amplitude for low reaches again, need not to cut off whole DC network power supply when breaking down, current-limiting state is relieved automatically to the current-limiting after the excision trouble, resume the normal power supply of other loads of DC electric wire netting, reducible loss.

Description

Direct current fault current limiter

Technical Field

The utility model relates to a direct current distribution technical field, especially a direct current fault current limiter.

Background

A Fault Current Limiter (FCL) for a low-voltage Direct Current (DC) distribution network. The direct current distribution network system can be connected with a plurality of power supplies, energy storage batteries and loads, can be independently operated by being separated from a power grid, and can provide a more efficient and compatible platform for the application of new energy equipment. However, the protection of dc systems still presents technical difficulties, the main difficulty of which is that dc faults present different fault characteristics. Power sources such as ac grids, photovoltaics, and wind turbines are usually required to be incorporated into a DC network through an inverter, and a large filter capacitor is generally provided on the DC side of the inverter. Fig. 1 shows a typical AC-DC converter configuration, in which when a DC short fault occurs, the capacitor discharges in the R, L, C path, the current rises rapidly and the voltage drops rapidly; when the voltage drops to the diode turn-on voltage, the fault current path switches to R, L, the diode, and the larger fault current may burn the diode directly. In addition, if the DC power source is a battery, the short circuit fault also causes the current to rise sharply. For whatever reason, excessive fault currents should be avoided.

Although it is possible to detect excessive current, directly blocking the inverter or switching off the battery when a fault occurs, this can result in the entire DC network losing power. There is a need for a better approach, namely: a fault current limiter is additionally arranged on the direct current side of a battery or a current converter, so that the current can be prevented from rising to be too high when a fault occurs, low-amplitude fault current can be continuously provided for the downstream, and after other relays trip to cut off the fault, the current limiter automatically relieves the current limiting state and restores the normal power supply of other loads of a DC power grid.

SUMMERY OF THE UTILITY MODEL

The main objective of the utility model is to overcome prior art's shortcoming, provide one kind and make output current can remain throughout in the electric current within range of setting for, the electric current rises to too high when can preventing the trouble from taking place, can last the fault current who provides the low amplitude again for low reaches, need not to cut off the power supply of whole DC network when breaking down, the direct current fault current limiter of reducible loss.

The utility model adopts the following technical scheme:

a direct current fault current limiter comprises at least two current limiting branches connected in parallel and a controller, wherein an input end and an output end are respectively led out from two ends of the plurality of current limiting branches after the current limiting branches are connected in parallel, a current measuring sensor is arranged on the output end, each current limiting branch is respectively provided with a solid-state switch used for controlling the current limiting branch to be connected or disconnected and a current limiting resistor connected with the solid-state switch in series, the resistance value of the current limiting resistor is larger than or equal to zero, the resistance values of the current limiting resistors of the current limiting branches are different, the controller is in communication connection with the current measuring sensor and is connected with the solid-state switch used for controlling each current limiting branch, and the output current of the output end of the controller is switched to connect each current limiting branch so as to keep the output current within a set current range.

Further, the current limiting resistor of the current limiting branch with the largest resistance value of the current limiting resistor is set to be the maximum current value which ensures that the output current of the output end is always less than or equal to the set current range when the current limiting branch is switched on.

Further, the current limiting resistor value of the current limiting branch with the smallest current limiting resistor value is set to be the smallest current value which ensures that the output current of the output end is always larger than or equal to the set current range when the current limiting branch is switched on.

Further, the set current range is 1 to 1.2 times of rated current.

Further, the direct current fault current limiter is also provided with a temperature sensor, and the temperature sensor is in communication connection with the controller.

Further, the solid-state switch adopts an IGBT or a Power MOSFET.

Further, the current measuring sensor adopts a Hall current sensor.

Further, the direct current fault current limiter comprises six current limiting branches which are connected in parallel, wherein one current limiting branch is only provided with a solid-state switch, and equivalently, the resistance value of the current limiting resistor of the current limiting branch is zero, and the other five branches are respectively connected with current limiting resistors in series, and the resistance values of the current limiting resistors are rated resistors which are 1/6 times, 2/6 times, 3/6 times, 4/6 times and 5/6 times respectively.

It can be known from the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are:

the utility model discloses a direct current fault current limiter can install in the direct current side of DC power or transverter, through setting up the current-limiting branch road that a plurality of current-limiting resistance values are different, can switch over each current-limiting branch road according to output current change, when power output current is less than the minimum current of settlement, reduce current limiter resistance, when the electric current is greater than the maximum current of settlement, improve current limiter resistance, make output current remain throughout the electric current range of settlement, the electric current rises to too high when can preventing the trouble from taking place, again can be for the low amplitude's of low reaches fault current that continuously provides, other relay tripping operation in low reaches cuts off after the trouble, the current-limiting state can be relieved automatically to the fault current limiter, resume the normal power supply of other loads of DC electric wire netting, and need not to cut off the power supply of whole DC network, reducible loss. Meanwhile, by arranging the temperature sensor, when the temperature sensor detects that the temperature of the current limiter is too high, all current limiting branches are cut off to serve as a backup protection mechanism, and the current limiter is prevented from being damaged.

Drawings

Fig. 1 is a circuit configuration of a prior art inverter and its fault response schematic;

fig. 2 is a schematic circuit diagram of a dc fault current limiter according to embodiment 1 of the present invention in a use state;

fig. 3 is a flow chart of a controller algorithm of a dc fault current limiter according to embodiment 1 of the present invention;

fig. 4 is an electrical control schematic diagram of a dc fault current limiter according to embodiment 1 of the present invention;

fig. 5 is a characteristic diagram of "output current-DC circuit equivalent resistance" of the DC fault current limiter according to embodiment 1 of the present invention.

Detailed Description

The present invention will be further described with reference to the following detailed description.

Example 1

Referring to fig. 2 to 5, the utility model discloses a direct current fault current limiter, including six current-limiting branch roads and controller that connect in parallel each other, input and output are drawn forth respectively at six parallelly connected back both ends of current-limiting branch road to set up current measurement sensor on the output, every current-limiting branch road sets up respectivelyThe controller is in communication connection with the current measuring sensor and is connected with the solid-state switch for controlling each current-limiting branch, the output current of the output end of the controller is switched in magnitude to conduct each current-limiting branch, so that the output current iFCL is kept in a set current range, namely 1 pu-1.2 pu, pu is a unit and represents a standard value, and the rated current of the DC power supply system is 1 pu. In this embodiment, the first current-limiting branch is provided with a solid-state switch S0, which is equivalent to zero resistance of the current-limiting resistor of the current-limiting branch; the second current limiting branch is provided with a solid-state switch S1 and a resistance value of 1/6R_LCurrent limiting resistor of R_LIs the rated resistance value of the DC power supply system; the third current limiting branch is provided with a solid-state switch S2 and a resistance value of 2/6R_LThe current limiting resistor of (1); the fourth current-limiting branch is provided with a solid-state switch S3 and a resistance value of 3/6R_LThe current limiting resistor of (1); the fifth current-limiting branch is provided with a solid-state switch S4 and a resistance value of 4/6R_LThe current limiting resistor of (1); the sixth current-limiting branch is provided with a solid-state switch S5 and a resistance value of 5/6R_LThe current limiting resistor of (1). The solid-state switches S0, S1, S2, S3, S4, and S5 are IGBTs. Levels S0-S5 are set from low to high, S0 is the lowest level switch, and S5 is the highest level switch. The current measuring sensor adopts a Hall current sensor.

The direct current fault current limiter is also provided with a temperature sensor which is in communication connection with the controller.

Referring to fig. 2 to 5, the utility model discloses during the use, install in the direct current side of DC power or transverter, through current measurement sensor real-time detection output current, controller control solid state switch S0 to S5 guarantee to only allow a single current-limiting branch road to switch on at the same moment. When the current is smaller than 1pu, the controller switches to be conducted by the lower-stage solid-state switch, and if S0 is conducted, the conduction of S0 is kept; when the current is larger than 1.2pu, the controller switches to be conducted by the higher-stage solid-state switch, and if S5 is conducted, the S5 is kept to be conducted; when the current is between 1 and 1.2pu, the current solid-state switch is kept conductive. When the current-limiting branch of the solid-state switch S5 is turned on, the current is greater than 1.2puDoes not exist, even if the equivalent resistance of the DC power supply is zero, only depends on 5/6R in the current limiter_LThe current limiting resistor of (3) may limit the current to 1.2 times or less of the rated current. When the temperature sensor detects that the temperature of the current limiter is too high to exceed a set threshold value, the controller cuts off all current limiting branches. In addition, if the current limiter continuously limits the current and cannot recover the normal state, the current limiter is proved to be failed to cut off the fault by other relays at the downstream, and the current limiter is easily overheated, and after the current limiter continuously limits the current for more than the set time, the controller controls all current limiting branches of the current limiter to be disconnected.

Example 2

This example differs from example 1 in that: the direct current fault current limiter comprises five current limiting branches which are connected in parallel, wherein one current limiting branch is only provided with a solid-state switch, the equivalent current limiting resistance value of the current limiting branch is zero, the other four current limiting branches are respectively provided with the solid-state switch and the current limiting resistor which are connected in series, and the current limiting resistance values of the current limiting branches are different. The solid state switch employs a Power MOSFET.

The aforesaid is only two concrete implementation manners of the utility model, nevertheless the utility model discloses a design concept is not limited to this, and all utilize this design right the utility model discloses carry out immaterial change, all should belong to and infringe the action of the scope of protection of the utility model.

Claims

1. A dc fault current limiter, characterized by: the current limiting device comprises at least two current limiting branches connected in parallel and a controller, wherein an input end and an output end are respectively led out from two ends of the plurality of current limiting branches after the current limiting branches are connected in parallel, a current measuring sensor is arranged on the output end, each current limiting branch is respectively provided with a solid-state switch used for controlling the conduction or disconnection of the current limiting branch and a current limiting resistor connected with the solid-state switch in series, the resistance value of the current limiting resistor is larger than or equal to zero, the resistance values of the current limiting resistors of the current limiting branches are different, the controller is in communication connection with the current measuring sensor and is connected with the solid-state switch for controlling each current limiting branch, and the output current of the output end of the controller is switched to conduct each current limiting branch so as to keep the output current within a set current range.

2. A dc fault current limiter according to claim 1, wherein: the current limiting resistor value of the current limiting branch circuit with the largest current limiting resistor value is set to be the maximum current value which ensures that the output current of the output end is always less than or equal to the set current range when the current limiting branch circuit is conducted.

3. A dc fault current limiter according to claim 1, wherein: the current limiting resistor value of the current limiting branch with the smallest current limiting resistor value is set to be the smallest current value which ensures that the output current of the output end is always larger than or equal to the set current range when the current limiting branch is conducted.

4. A dc fault current limiter according to any one of claims 1 to 3, wherein: the set current range is 1-1.2 times of rated current.

5. A dc fault current limiter according to claim 1, wherein: and a temperature sensor is also arranged and is in communication connection with the controller.

6. A dc fault current limiter according to claim 1, wherein: the solid-state switch adopts an IGBT or a Power MOSFET.

7. A dc fault current limiter according to claim 1, wherein: the current measuring sensor adopts a Hall current sensor.

8. A dc fault current limiter according to claim 1, wherein: the three-phase current limiting circuit comprises six current limiting branches which are connected in parallel, wherein one current limiting branch is only provided with a solid-state switch and is equivalent to zero in the resistance value of a current limiting resistor of the current limiting branch, and the other five branches are respectively connected with current limiting resistors in series, and the resistance values of the current limiting resistors are 1/6 times, 2/6 times, 3/6 times, 4/6 times and 5/6 times of rated resistors.