CN112865055B - Inductive coupling type direct current fault current limiter and control method thereof - Google Patents
Inductive coupling type direct current fault current limiter and control method thereof Download PDFInfo
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- CN112865055B CN112865055B CN202110056307.3A CN202110056307A CN112865055B CN 112865055 B CN112865055 B CN 112865055B CN 202110056307 A CN202110056307 A CN 202110056307A CN 112865055 B CN112865055 B CN 112865055B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
Abstract
The invention discloses an inductive coupling type direct current fault current limiter and a control method thereof, wherein the structure comprises a bridge arm I, a bridge arm II and an H-bridge circuit formed by the bridge arm I, the bridge arm II, the bridge arm IV and the bridge arm III, wherein a series branch formed by the bridge arm I and the bridge arm II is connected in series with a series branch formed by the bridge arm III and the bridge arm IV in parallel; the control method for the inductance coupling type direct current fault current limiter comprises the steps of initializing, turning off an IGBT group when a fault signal is detected, and enabling the current consumption of an inductance loop to be zero; triggering the IGBT group again; the current limiter recovers in preparation for the next failure. Compared with the prior art, the method is used for the low-voltage flexible direct-current power distribution network, and 1) when the system is in normal operation, the transient response characteristic and the operation stability of a direct-current system are not adversely affected; 2) After the direct current fault occurs, the rapid rise of the fault current can be effectively limited, and sufficient action time is created for protection and fault isolation.
Description
Technical Field
The invention relates to the field of multi-end flexible direct-current power distribution networks, in particular to a direct-current fault current limiter topological structure based on the matching of a coupling inductor and a lightning arrester and a control strategy thereof.
Background
In recent years, with the increase of the number of distributed power sources and new energy, a low-voltage dc power distribution network has the advantages of small line loss, high power supply reliability, and convenience for accessing the distributed power sources, energy storage devices, and the like, and therefore, a flexible dc power distribution system based on a Voltage Source Converter (VSC) has become an important subject of current research. When a bipolar short-circuit fault occurs in a flexible direct-current power distribution system based on the VSC-type converter, the capacitor in the converter discharges to a fault point, the discharging current rises quickly, the amplitude is large, the voltage of the whole system drops, and if the fault is not isolated timely, the damage of a power electronic device can be caused, so that the whole power grid is broken down. In order to solve the problem, circuit breakers are required to be installed at two ends of a line, when a fault occurs, the fault line is cut off, a fault point is isolated, and then normal operation of the rest lines is guaranteed. In a low-voltage direct-current power distribution network, a fault is generally required to be removed within a few milliseconds after the fault occurs, but a traditional mechanical circuit breaker cannot meet the requirement, and therefore, a current limiter needs to be installed in a circuit to limit the rising rate and the current amplitude of current, so that the circuit breaker is provided with enough time for fault isolation. The traditional current limiter generally adopts a mode of directly connecting an inductor in series into a line for current limiting, although the method can play a role in limiting the rising rate of current, when a system normally operates, the dynamic response characteristic of the system can be influenced by connecting the inductor in series in the line, and meanwhile, the clearing time of fault current can also be increased. When short-circuit fault occurs in a direct current system, the fault current rises rapidly and the direct current voltage drops rapidly due to capacitor discharge, so that the whole direct current power grid is seriously endangered. In order to solve the problem, the dc fault current limiter needs to quickly limit the current after the line current rises to a threshold value after a fault occurs in the line, and cannot affect the system when the line normally operates.
Disclosure of Invention
In order to guarantee safe operation and reliable power supply of a direct current system, the invention provides an inductive coupling type direct current fault current limiter and a control method thereof.
The invention relates to an inductive coupling type direct current fault current limiter, which structurally comprises bridge arms from one to four and an H-bridge circuit formed by the bridge arms, wherein:
the bridge arm I is connected with the bridge arm II in series, the bridge arm IV is connected with the bridge arm III in series, and a series connection branch formed by the bridge arm I and the bridge arm II is connected with a series connection branch formed by the bridge arm III and the bridge arm IV in parallel; connecting IGBT groups in series between the bridge arm first connecting point, the bridge arm second connecting point, the bridge arm third connecting point and the bridge arm fourth connecting point, and connecting a lightning arrester in parallel on the IGBT groups;
the bridge arm I and the bridge arm III are respectively formed by connecting a diode and a resistor in series; the second bridge arm and the fourth bridge arm are respectively composed of a coupling inductor, and the inductance values of the coupling inductors are equal.
The invention discloses a control method of an inductive coupling type direct current fault current limiter, which comprises the following steps:
firstly, initializing a current limiter;
when a short-circuit fault is detected, the trigger signal to the IGBT group is immediately removed, and then fault current passes through the fourth bridge arm, then flows through the third bridge arm through one branch circuit, and then flows through the lightning arrester A through the other branch circuit and then is fed into a fault point together with the second bridge arm;
in the current limiting stage, the voltage at the two ends of the current limiter is the voltage at the two ends of the lightning arrester A; under the action of residual voltage at two ends of the lightning arrester, the rising rate and amplitude of fault current are effectively limited;
when the short-circuit fault is detected and a tripping signal is sent to the DCCB, the DCCB starts to act, the fault current in the fault line starts to fall, the current of the inductive loop of the bridge arm II quickly falls to zero, and the lightning arrester A is not conducted any more; the continuous current flowing through the fourth bridge arm forms a circulating current through the third bridge arm, the second bridge arm and the first bridge arm, the fault current is conducted through the load branches of the fourth bridge arm and the third bridge arm, finally the fault current is cut off to zero under the action of the breaker, and a fault point is effectively isolated;
after the fault current is cut off, the current of the inductance loop of the bridge arm four is consumed to be zero by the load branches of the bridge arm one and the bridge arm three; and triggering the IGBT group, and recovering the current limiter to prepare for the next failure.
The coupling inductance type direct current fault current limiter provided by the design of the invention is suitable for a low-voltage flexible direct current distribution network. Compared with the direct current reactor for current limiting, the invention mainly has the following advantages:
1) When the direct current system normally operates, current flows through the coupling inductors connected with the two different name ends, and external equivalent inductance is zero, so that the transient response characteristic and the operation stability of the direct current system cannot be adversely affected;
2) After the direct current fault, the lightning arrester can be quickly connected into a fault loop, the current flows through the lightning arrester, and residual voltages at two ends of the current play a role in limiting the current, so that the fault current can be effectively limited from rapidly rising, and sufficient action time is created for protection and fault isolation;
3) After the direct current breaker trips, the fault current in the direct current line begins to drop, when the current drops below the starting current of the lightning arrester, the lightning arrester automatically quits running, the energy stored in the inductor is finally absorbed by the resistor in the loop, and the lightning arrester in the breaker only needs to absorb the energy in the fault loop without consuming the energy stored in the inductor, so that the fault current clearing time is greatly shortened;
4) In a non-fault line, when a lightning arrester in a current limiter limits current to make the current drop below an operating current, the current is automatically transferred to a resistor R 2 And the branch circuit does not interrupt power transmission between non-fault lines.
Drawings
Fig. 1 is a topology structure diagram of an inductive coupling type dc fault current limiter according to the present invention;
fig. 2 is a schematic diagram of a current path (dotted line portion) of the inductive coupling type dc fault current limiter according to the present invention when the system is in normal operation;
fig. 3 is a schematic diagram of a current path (dotted line portion) in the current limiting process of the inductively coupled dc fault current limiter according to the present invention;
fig. 4 is a current path (dotted line portion) in the fault current clearing process of the inductive coupling type dc fault current limiter of the present invention; the light dotted line represents the circulating current of the continuous current in the inductor inside the current limiter; dark colored dashed lines indicate fault currents in the line);
fig. 5 is an overall flowchart of a method for controlling an inductively coupled dc fault current limiter according to the present invention.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings and examples.
As shown in fig. 1, the topology of the inductive coupling type dc fault current limiter of the present invention is shown. The topological structure is an H-bridge structure formed by a first bridge arm and a fourth bridge arm. Wherein: bridge arm one is composed of a first diode group D 1 And a first resistor R 1 Are connected in series; bridge arm III is composed of a second diode group D 2 And a second resistor R 2 Are connected in series; the fourth bridge arm and the second bridge arm are respectively composed of a first coupling inductor L 1 And a second coupling inductor L 2 The inductance values of the two coupling inductors are equal. The dotted terminals of the coupled inductors are shown in the figure.
And an IGBT group is connected in series between the first and second connection points of the bridge arm and the third and fourth connection points of the bridge arm, and a lightning arrester is connected in parallel on the IGBT group.
When the current in the inductance loop is detected to be zero, the current limiter is recovered to trigger the IGBT.
Fig. 5 is a flowchart illustrating an overall method for controlling an inductively coupled dc fault current limiter according to the present invention. Aiming at the topological structure of the inductance coupling type direct current fault current limiter, the invention provides a corresponding control method, initializes the current limiter, applies a trigger signal to the IGBT and conducts the IGBT; when the direct current rises to an action threshold value of the current limiter, immediately turning off a trigger signal to the IGBT; the specific process is as follows:
firstly, initializing a current limiter, applying a trigger signal to an IGBT and conducting the IGBT;
when in normal operation, direct current respectively flows into mutual inductance reactance L 1 And L 2 The synonym end of (2); the equivalent inductance of the current limiter is L eq ＝L 1 +L 2 2M, if the mutual inductance value M of the two coupling inductors is equal to the two inductance values, the equivalent inductor L of the current limiter in normal operation can be ensured eq The current limiter is approximately equal to 0, namely when the power fluctuation of the system occurs, the current limiter can not cause adverse effect on the dynamic performance of the system;
when short-circuit fault occurs in the system, the direct current rises to the action threshold value of the current limiter, the trigger signal to the IGBT is immediately removed, and the fault current in the line passes through the inductor L 1 Then one branch flows through the diode D 2 And a resistor R 2 The other branch passes through the lightning arrester A and the inductor L 2 And then fed together into the failure point. In the current limiting stage, the voltage at the two ends of the current limiter is the voltage at the two ends of the arrester A, so that the residual voltage of the arrester A plays a role in limiting the current in the current limiting process. Under the effect of residual voltage at two ends of the lightning arrester, the rising rate and amplitude of the fault current can be effectively limited. When a protection device installed in the line detects the occurrence of a fault and sends a trip signal to the DCCB, the DCCB starts to operate, and the fault current in the faulty line starts to drop and flows through the inductor L 2 The current is quickly reduced to zero, the lightning arrester A is not conducted any more, and the inductorL 1 The continuous current in the capacitor passes through the resistor R 2 Inductance L 2 And R 1 A circulating current is formed when the diode D 1 And D 2 At the inductor L 1 Is conducted under the action of counter electromotive force, and fault current passes through an inductor L 1 And a resistance R 2 The branch circuit is conducted and finally is cut off to zero under the action of the breaker, and the fault point is effectively isolated. Inductor L after the fault current in the line has been cut off 1 The residual energy stored in the capacitor is controlled by a resistor R 1 And R 2 The consumption reaches zero and the current limiter is fully restored in preparation for the next failure.
Claims (2)
1. An inductance coupling type direct current fault current limiter is characterized in that the structure of the direct current fault current limiter comprises a first bridge arm, a second bridge arm and a fourth bridge arm, and an H-bridge circuit formed by the first bridge arm, the second bridge arm and the fourth bridge arm, wherein:
the first bridge arm is connected with the second bridge arm in series, the fourth bridge arm is connected with the third bridge arm in series, and a series connection branch formed by the first bridge arm and the second bridge arm is connected with a series connection branch formed by the third bridge arm and the fourth bridge arm in parallel; connecting IGBT groups in series between the bridge arm I and the bridge arm II and between the bridge arm III and the bridge arm IV, and connecting a lightning arrester in parallel on the IGBT groups;
the bridge arm I and the bridge arm III are respectively formed by connecting a diode and a resistor in series; the second bridge arm and the fourth bridge arm are respectively composed of a coupling inductor, and the inductance values of the coupling inductors are equal.
2. A method of controlling an inductively coupled dc fault current limiter as claimed in claim 1, wherein the method comprises the steps of:
firstly, initializing a current limiter;
when a short-circuit fault is detected, immediately removing a trigger signal to the IGBT group, and feeding a fault current into a fault point through one branch after passing through the bridge arm four and through the bridge arm three and through the other branch after passing through the arrester A and the bridge arm two;
in the current limiting stage, the voltage at the two ends of the current limiter is the voltage at the two ends of the lightning arrester A; under the action of residual voltage at two ends of the lightning arrester, the rising rate and amplitude of fault current are effectively limited;
when the breaker trips, the fault current in the fault line begins to drop, the current of the inductance loop of the bridge arm II quickly drops to zero, and the lightning arrester A is not conducted any more; the continuous current flowing through the fourth bridge arm forms a circulating current through the third bridge arm, the second bridge arm and the first bridge arm, the fault current is conducted through the load branches of the fourth bridge arm and the third bridge arm, finally the fault current is cut off to zero under the action of the breaker, and a fault point is effectively isolated;
after the fault current is cut off, the inductance loop current of the bridge arm four is consumed to be zero by the load branches of the bridge arm one and the bridge arm three; and triggering the IGBT group, and recovering the current limiter to prepare for the next fault.
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| CN112821372B (en) * | 2021-03-12 | 2022-05-31 | 南京航空航天大学 | Forward feedback type absorption circuit for improving efficiency of direct-current solid-state circuit breaker |
| CN114530836B (en) * | 2022-04-01 | 2022-11-11 | 四川大学 | Bidirectional direct current fault current limiter based on coupling inductor and control method thereof |
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| CN108418196A (en) * | 2018-01-17 | 2018-08-17 | 天津大学 | Electric current transfevent fault current limiter and its control method suitable for flexible direct current power grid |
| CN109193580A (en) * | 2018-09-12 | 2019-01-11 | 山东大学 | A kind of current-limiting type high-speed reclosure direct-current breaker topology structure and control method |
| CN110071492A (en) * | 2019-04-17 | 2019-07-30 | 天津大学 | A kind of bridge type Coupled Superconducting direct current limiter and method |
| JP2019153976A (en) * | 2018-03-05 | 2019-09-12 | 富士電機株式会社 | DC circuit breaker |
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| CN107086555B (en) * | 2017-05-31 | 2019-02-22 | 天津大学 | A kind of DC solid circuit breaker control method with adaptive throttling ability |
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| CN108418196A (en) * | 2018-01-17 | 2018-08-17 | 天津大学 | Electric current transfevent fault current limiter and its control method suitable for flexible direct current power grid |
| JP2019153976A (en) * | 2018-03-05 | 2019-09-12 | 富士電機株式会社 | DC circuit breaker |
| CN109193580A (en) * | 2018-09-12 | 2019-01-11 | 山东大学 | A kind of current-limiting type high-speed reclosure direct-current breaker topology structure and control method |
| CN110071492A (en) * | 2019-04-17 | 2019-07-30 | 天津大学 | A kind of bridge type Coupled Superconducting direct current limiter and method |
| CN111682788A (en) * | 2020-08-13 | 2020-09-18 | 山东晨宇电气股份有限公司 | Current active transfer type MMC power electronic transformer with fault blocking capability |
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