CN110880745A - Active resistance-capacitance type direct current limiter based on double-capacitance oscillation and control method - Google Patents

Abstract

The invention discloses an active resistance-capacitance DC current limiter based on double-capacitor oscillation and a control method, comprising a parallel current-passing branch and a resistance-capacitance branch. Capacitor branch, low-voltage arm capacitor branch and semiconductor components are connected in series; high-voltage arm capacitor branch includes parallel high-voltage capacitor, arrester and controllable discharge branch, low-voltage arm capacitor branch includes parallel low-voltage capacitor and controllable charging power supply, semiconductor The component is composed of a thyristor and a diode in anti-parallel connection, the negative electrode of the low-voltage capacitor is electrically connected with the high-voltage capacitor, and the positive electrode of the low-voltage capacitor is electrically connected with the anode of the semiconductor component. The beneficial effects of the present invention are: in the present invention, the current limiter is mainly composed of conventional power equipment such as mechanical switches, high-voltage capacitors, low-voltage capacitors, thyristors and diodes, and the cost is low. The daily operation and maintenance of the flow device is easier.

Description

Active Resistor-Capacitor DC Current Limiter and Control Method Based on Dual Capacitor Oscillation

technical field

The invention relates to the technical field of power equipment, and in particular, to an active resistance-capacitor DC current limiter based on dual-capacitor oscillation and a control method.

Background technique

Hybrid multi-terminal DC transmission system is an important part of my country's long-distance transmission system. After a short-circuit fault occurs in the hybrid multi-terminal DC transmission system, the voltage source converter will feed the fault current to the fault point. For the fault current component fed by the voltage source converter, the flow path has small damping, and the rising speed is fast and stable. It cannot be cleared quickly by controlling the inverter. Voltage source converters are mainly composed of fully-controlled power electronic devices (IGBTs), and their ability to withstand surge currents is weak. Therefore, this part of fault current may damage key equipment such as converters, thereby posing a serious threat to the system. In order to ensure the safe and reliable operation of the hybrid multi-terminal DC transmission system, its primary task is to quickly limit the fault current component fed by the voltage source converter, so as to obtain a longer response time for the relay protection and reduce the current and voltage of the DC circuit breaker. stress requirements.

In order to slow down the rising speed of the voltage source feed-in fault current and limit the peak value of the fault current, it is considered to be an effective measure to install a current limiter in the DC system. According to the different input methods, the current limiter can be divided into passive type and active type current limiter. For the active type current limiter, according to the different key switching elements, it can be divided into solid-state current limiter and superconducting current limiter. Such current limiters do not affect the normal operation of the system, the response speed is millisecond, and the current limiting effect is good, but due to the use of fully controlled power electronic devices or superconducting materials, the cost is expensive, and the operation and maintenance are troublesome.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention proposes an active RC current limiter based on dual capacitor oscillation and a control method, which mainly solves the problems of high cost and difficult operation and maintenance of the active DC current limiter. The active RC current limiter in the present invention is mainly composed of traditional power equipment such as mechanical switches, high-voltage capacitors, low-voltage capacitors, and arresters, and has the characteristics of fast response speed, low cost, and simple operation and maintenance.

For solving the above-mentioned technical problems, the technical scheme of the present invention is as follows:

An active resistance-capacitor DC current limiter based on double-capacitor oscillation includes a parallel current-passing branch and a resistance-capacitance branch, the current-passing branch is formed by a mechanical switch, and the resistance-capacitance branch is formed by a high-voltage arm capacitor branch. circuit, the low-voltage arm capacitor branch and the semiconductor component are connected in series; the high-voltage arm capacitor branch includes a parallel high-voltage capacitor, a surge arrester and a controllable discharge branch, and the low-voltage arm capacitor branch includes a parallel low-voltage capacitor and a controllable charging power supply , the semiconductor component is composed of a thyristor and a diode in anti-parallel connection, the negative electrode of the low-voltage capacitor is electrically connected to the high-voltage capacitor, and the positive electrode of the low-voltage capacitor is electrically connected to the anode of the semiconductor component. In the present invention, the current limiter is mainly composed of conventional power equipment such as mechanical switches, high-voltage capacitors, low-voltage capacitors, thyristors and diodes, and the cost is low.

In some embodiments, the mechanical switch is a fast mechanical switch, and the fast mechanical switch is driven by an electromagnetic repulsion mechanism, and the operation time of the electromagnetic repulsion mechanism is 5ms.

In some embodiments, the turn-on time of the semiconductor device is 1 μs.

In some embodiments, the controllable discharge branch is formed of a resistor and a mechanical switch in series, and the controllable charging power source is a DC power source with an adjustable output voltage.

In some embodiments, the capacitance ratio of the low voltage capacitor and the high voltage capacitor is greater than 100:1.

At the same time, the present invention also provides a control method compatible with the above-mentioned active resistance-capacitor DC current limiter based on dual-capacitor oscillation,

Detecting the DC line state where the active resistance-capacitor DC current limiter based on dual-capacitor oscillation is located;

According to the state of the DC line, control the on-off state of the mechanical switch, the controllable discharge branch and the semiconductor component in the current limiter;

When the DC line is operating normally, the mechanical switch is closed, the voltage across the high-voltage capacitor is zero, the controllable discharge branch is in an open state, the low-voltage capacitor is precharged with a voltage of 3-5kV, and the semiconductor component is turned off , the normal load current flows in the current branch, the current is turned on by the mechanical switch, and the current limiter exhibits a zero impedance state to the outside;

When the DC line fails to limit the current, the mechanical switch receives the opening command, and after the dynamic and static contacts of the mechanical switch are opened, the semiconductor component receives the conduction command, the semiconductor component is turned on, and the high-voltage capacitor and the low-voltage capacitor are turned on. The oscillation between the two causes the mechanical switch to cross zero and extinguish the arc, the fault current is transferred from the current branch to the RC branch, the fault current charges the RC branch, the controllable discharge branch is in an open state, and the current is limited. The voltage at both ends of the arrester continuously rises to the residual voltage of the arrester, and the current limiter presents a high impedance state to the outside, limiting the rise rate and peak value of the fault current;

When the DC line recovers after the fault current is limited, wait for the DC circuit breaker to clear the fault current and completely isolate the fault point, close the controllable discharge branch, the voltage across the high-voltage capacitor is reduced to zero, and the conduction command of the semiconductor component is cancelled, The semiconductor components are turned off, the mechanical switch is closed, and the current limiter returns to a zero impedance state.

The beneficial effects of the present invention are:

1. In the present invention, the current limiter is mainly composed of conventional power equipment such as mechanical switches, high-voltage capacitors, low-voltage capacitors, thyristors and diodes, and the cost is low. During normal operation, it is in a zero-impedance state, with no operating loss, and will not affect the normal operation of the system. Compared with the IGBT switch tube of the existing DC current limiter, the operating loss of several tens of kW will often be generated. The present invention saves energy. , no additional heat generation, no special cooling device is needed to cool the restrictor. At the same time, because no superconducting materials or power electronic devices are used, the daily operation and maintenance of the current limiter is easier.

2. In the present invention, the current limiter is in a zero impedance state during normal operation, and will not affect the normal operation of the system.

3. Since mechanical switches, thyristors and diodes all use fast-response components, the current limiter in the present invention can switch from a low-impedance state to a high-impedance state within a few milliseconds, with fast response speed and good current limiting effect.

Description of drawings

1 is a schematic structural diagram of a specific embodiment of an active RC current limiter based on dual-capacitor oscillation according to the present invention;

FIG. 2 is a flowchart of a control method of an active RC current limiter based on dual capacitor oscillation according to the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer and clearer, the content of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the drawings only show some but not all of the contents related to the present invention.

As shown in FIG. 1 , this embodiment proposes an active RC current limiter based on dual-capacitor oscillation, which includes a parallel current-passing branch and a RC branch, and the current-passing branch is routed by a mechanical switch MS The resistance-capacitance branch is connected in series by the high-voltage arm capacitor branch, the low-voltage arm capacitor branch and the semiconductor component T;

The high-voltage arm capacitor branch includes a parallel high-voltage capacitor C _hv , a surge arrester MOV and a controllable discharge branch DP, the low-voltage arm capacitor branch includes a parallel low-voltage capacitor _Clv and a controllable charging power source S, and the semiconductor component T is composed of a thyristor SCR and a diode D in antiparallel connection, the negative electrode of the low voltage capacitor _{Clv is electrically connected to the high voltage capacitor C hv ,} and the positive electrode of the low voltage capacitor _Clv is electrically connected to the anode of the semiconductor component T.

In the present invention, the current limiter is mainly composed of conventional power equipment such as a mechanical switch, a high-voltage capacitor C _hv , a low-voltage capacitor C _lv , a thyristor SCR and a diode D, and the cost is low. During normal operation, it is in a zero-impedance state, with no operating loss, and will not affect the normal operation of the system. Compared with the IGBT switch tube of the existing DC current limiter, the operating loss of several tens of kW will often be generated. The present invention saves energy. , no additional heat generation, no special cooling device is needed to cool the restrictor. At the same time, because no superconducting materials or power electronic devices are used, the daily operation and maintenance of the current limiter is easier.

Further, the mechanical switch MS is a fast mechanical switch, the fast mechanical switch is driven by an electromagnetic repulsion mechanism, and the operation time of the electromagnetic repulsion mechanism is 5ms. .

Further, the turn-on time of the semiconductor component is 1 μs.

Since the mechanical switch MS, thyristor SCR and diode D all use fast-response components, the current limiter in the present invention can switch from a low-impedance state to a high-impedance state within a few milliseconds, with fast response speed and good current limiting effect.

Furthermore, the controllable discharge branch DP is composed of a resistor and a mechanical switch connected in series, and the controllable charging power supply S is a DC power supply with an adjustable output voltage.

Furthermore, the capacitance ratio of the low-voltage capacitor C _lv to the high-voltage capacitor C _hv is greater than 100:1, which ensures that the voltage change ratio of the high-voltage capacitor C _hv to the low-voltage capacitor C _lv is less than 1:100.

At the same time, the present invention also provides a control method compatible with the above-mentioned active resistance-capacitor DC current limiter based on dual-capacitor oscillation,

S1, detecting the DC line state where the active RC current limiter based on dual-capacitor oscillation is located;

S2, according to the state of the DC line, control the on-off state of the mechanical switch, the controllable discharge branch and the semiconductor component in the current limiter;

S101, when the DC line is operating normally, the mechanical switch MS is closed, the voltage across the high-voltage capacitor C _hv is zero, the controllable discharge branch DP is in an open state, and the low-voltage capacitor C _lv is pre-charged with 3-5kv voltage, the semiconductor component T is turned off, the normal load current flows in the current branch, the current is turned on by the mechanical switch MS, and the current limiter exhibits a zero impedance state to the outside;

S102, when the DC line is fault current limiting, the mechanical switch MS receives an opening command, and after waiting for the moving and static contacts of the mechanical switch MS to open, the semiconductor component T receives a turn-on command, the semiconductor component T is turned on, so The oscillation between the high voltage capacitor C _hv and the low voltage capacitor C _lv causes the mechanical switch MS to cross zero and extinguish the arc, the fault current is transferred from the current branch to the RC branch, and the fault current charges the RC branch, the said The controllable discharge branch DP is in the open circuit state, the voltage across the current limiter continuously rises to the residual voltage of the arrester MOV, and the current limiter presents a high impedance state to the outside, limiting the rise rate and peak value of the fault current;

S103, when the DC line is restored after the fault current is limited, wait for the DC circuit breaker to clear the fault current and completely isolate the fault point, close the controllable discharge branch DP, the voltage across the high-voltage capacitor C _hv is reduced to zero, and the semiconductor component is cancelled The conduction command of T turns off the semiconductor component T, closes the mechanical switch MS, and the current limiter returns to a zero impedance state.

Working principle: After a commutation process, when the DC line fails, the fault current is transferred from the current branch to the resistance-capacitance branch, and the resistance-capacitor current-limiting reactance composed of arresters and capacitors provides a limiting effect, thereby limiting the fault current. Rise rate and peak.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose thereof is to enable those of ordinary skill in the art to understand the content of the present invention and implement them accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the essence of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. an active resistance-capacitance DC current limiter based on double-capacitor oscillation is characterized in that, comprising a parallel flow branch and a resistance-capacitance branch, the flow-through branch is formed by a mechanical switch, and the resistance-capacitance branch is formed by a mechanical switch. The branch is connected in series by the high-voltage arm capacitor branch, the low-voltage arm capacitor branch and the semiconductor component; The high-voltage arm capacitor branch includes a parallel high-voltage capacitor, a surge arrester and a controllable discharge branch, the low-voltage arm capacitor branch includes a parallel low-voltage capacitor and a controllable charging power supply, and the semiconductor component is composed of a thyristor and a diode in anti-parallel connection , the negative electrode of the low-voltage capacitor is electrically connected to the high-voltage capacitor, and the positive electrode of the low-voltage capacitor is electrically connected to the anode of the semiconductor component. 2 . The active resistance-capacitor DC current limiter based on dual-capacitor oscillation according to claim 1 , wherein the mechanical switch is a fast mechanical switch, and the fast mechanical switch is driven by an electromagnetic repulsion mechanism. 3 . The operating time of the electromagnetic repulsion mechanism is 5ms. 3 . The active resistance-capacitor DC current limiter based on dual-capacitor oscillation according to claim 1 , wherein the turn-on time of the semiconductor component is 1 μs. 4 . 4. The active resistance-capacitor DC current limiter based on dual-capacitor oscillation according to claim 1, wherein the controllable discharge branch is composed of a resistor and a mechanical switch in series, and the controllable charging power supply is DC power supply with adjustable output voltage. 5 . The active RC current limiter based on dual-capacitor oscillation according to claim 1 , wherein the capacitance ratio of the low-voltage capacitor and the high-voltage capacitor is greater than 100:1. 6 . 6. A control method for an active RC current limiter based on dual-capacitor oscillation as described in any one of claims 1-5, characterized in that, Detecting the DC line state where the active resistance-capacitor DC current limiter based on dual-capacitor oscillation is located; According to the state of the DC line, control the on-off state of the mechanical switch, the controllable discharge branch and the semiconductor component in the current limiter; When the DC line is in normal operation, the mechanical switch is closed, the voltage across the high-voltage capacitor is zero, the controllable discharge branch is in an open state, the low-voltage capacitor is precharged with a voltage of 3-5kV, and the semiconductor component is turned off , the normal load current flows in the current branch, the current is turned on by the mechanical switch, and the current limiter exhibits a zero impedance state to the outside; When the DC line fails to limit the current, the mechanical switch receives the opening command, and after the dynamic and static contacts of the mechanical switch are opened, the semiconductor component receives the conduction command, the semiconductor component is turned on, and the high-voltage capacitor and the low-voltage capacitor are turned on. The oscillation between the two causes the mechanical switch to cross zero and extinguish the arc, the fault current is transferred from the current branch to the RC branch, the fault current charges the RC branch, the controllable discharge branch is in an open state, and the current is limited. The voltage at both ends of the arrester continuously rises to the residual voltage of the arrester, and the current limiter presents a high impedance state to the outside, limiting the rise rate and peak value of the fault current; When the DC line recovers after the fault current is limited, wait for the DC circuit breaker to clear the fault current and completely isolate the fault point, close the controllable discharge branch, the voltage across the high-voltage capacitor is reduced to zero, and the conduction command of the semiconductor component is cancelled, The semiconductor components are turned off, the mechanical switch is closed, and the current limiter returns to a zero impedance state.

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