CN107069654B - A kind of two-way hybrid dc circuit breaker and cutoff method for middle voltage distribution networks - Google Patents

Abstract

A bidirectional hybrid DC circuit breaker and breaking method for medium voltage distribution network are disclosed, the bidirectional hybrid DC circuit breaker includes a circuit breaker body, a signal acquisition system, a signal processing system, a control system, an operating mechanism and a human body In the computer interaction interface, the circuit breaker shown has added a negative feedback link, which feeds back the ambient temperature and the capacitance voltage signal of the driving circuit to the control system, so that the contacts can be opened at the expected time accurately, and the accurate opening and closing operations can be realized. The integration of the loop and the bridge circuit realizes the purpose of a group of oscillating circuits to achieve bidirectional breaking, and solves the demand for bidirectional breaking in the new energy power supply system.

Description

A bidirectional hybrid DC circuit breaker and breaking method for medium voltage distribution network

technical field

The invention relates to a bidirectional hybrid DC circuit breaker and a breaking method thereof for a medium-voltage distribution network, in particular to a circuit breaker which realizes opening and closing by controlling an electromagnetic repulsion operating mechanism through a DC loop current signal.

Background technique

With the gradual depletion of fossil energy and the further aggravation of environmental pollution, the development of clean and renewable energy has gradually become a hot issue in the power industry. However, compared with traditional energy sources, new energy sources have obvious defects such as unstable output characteristics and scattered energy distribution. According to the different capacity of new energy in my country, medium and high voltage lines are connected to the transmission network, and low-voltage lines are connected to the distribution network. No matter which method is used, the impact on the traditional AC power grid will be huge, causing a series of problems, such as relay protection problems, voltage and frequency stability of the power grid, and so on. The best solution to these problems at this stage is to isolate the new energy power generation system from the traditional AC system through a DC transmission system. However, the new energy DC system has bidirectional flow of power flow, so the circuit breaker used in this DC power supply system must have bidirectional breaking capability.

In recent years, with the continuous development of power electronics technology, a solid-state DC circuit breaker based on a gate-turn-off device has appeared. It has the characteristics of short operating time and can achieve arc-free breaking, so it has been applied in certain occasions. However, compared with the traditional mechanical circuit breaker, its disadvantages of large on-state loss, limited carrying capacity, and weak anti-inrush and overvoltage capabilities make it have greater limitations in application.

The current DC circuit breaker mainly includes three schemes: mechanical DC circuit breaker, hybrid DC circuit breaker, and all-solid-state DC circuit breaker. Mechanical circuit breakers have limited breaking capacity and long breaking time, which makes it difficult to meet the development needs of high voltage and high current in the current power system. The all-solid-state DC circuit breaker has large on-state loss and limited current capacity, and it is also difficult to adapt to the high current demand of the DC system.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

Contents of the invention

In order to solve the requirement of bidirectional breaking in the medium-voltage DC distribution network system, the present invention designs a bidirectional hybrid DC circuit breaker based on an electromagnetic repulsion mechanism. Through the integration of the oscillating circuit and the bridge circuit, a group of oscillating circuits can achieve the purpose of two-way breaking, and solve the demand for two-way breaking in the new energy power supply system.

In order to achieve the above advantages, the present invention provides a bidirectional hybrid DC circuit breaker, which is used to control the on-off of the DC power transmission and distribution system, including the circuit breaker body, signal acquisition system, signal processing system, control system, operating mechanism and man-machine user-interface.

The purpose of the present invention is to be achieved through the following technical solutions.

In one aspect of the present invention, a bidirectional hybrid DC circuit breaker for medium voltage distribution network includes a circuit breaker body, a signal acquisition system, a signal processing system, a control system, an operating mechanism and a human-computer interaction interface, the circuit breaker body Including the main current circuit, bridge circuit, oscillation branch, overvoltage limiting branch and isolation switch V1, the main current circuit is composed of two mechanical switches S1 and S2 connected in series, where one end of S1 is loaded on the outgoing terminal A1, and one end of S2 is connected to On the outgoing terminal A2.

The bridge circuit is composed of power diodes D1, D2 and thyristors T1, T2, T3, T4, among which, D1 is connected in parallel at both ends of mechanical switch S1, D2 is connected in parallel at both ends of S2, the positive pole of D1 is connected with the outgoing terminal of A1, and the positive pole of D2 is isolated through isolation. The switch V1 is connected to the outlet terminal of A2, the negative poles of D1 and D2 are connected to the common terminal of the mechanical switch, the positive poles of the thyristors T1 and T2 are connected, the negative poles are respectively connected to the outgoing terminal A1 and the isolation switch V1, the negative poles of the thyristors T3 and T4 are connected to each other, and the positive poles are respectively connected to the On the outlet terminal A1 and the isolating switch V1.

The oscillating branch is composed of a transfer capacitor C and an oscillating inductance L in series, wherein the non-common terminals of the oscillating inductance L are connected to the common terminals of the thyristors T3 and T4, and the non-common terminals of the transfer capacitor C are connected to the thyristors T1 and T2.

The overvoltage limiting branch is connected in parallel to both ends of the mechanical switches S1 and S2, and connected to the outgoing terminal A1 and the isolation switch V1 respectively.

A signal acquisition system, the signal acquisition system collects the voltage value, current value, and current direction of the circuit breaker body, the voltage value, current value, and working environment temperature of the drive circuit of the repulsion mechanism as the operating mechanism, and the breakdown of the circuit breaker mechanism. Brake, closing status and contact displacement information.

A signal processing system, the signal processing system processes the signal collected by the signal collection system, including filtering, amplification and/or A/D conversion.

A control system, the control system receives the signal processed by the signal processing system, completes the analysis of the voltage signal, current signal, and current rise rate, and detects the system short-circuit fault, and controls the opening and closing operations of the operating mechanism according to the analysis results.

An operating mechanism, the operating mechanism performs an opening or closing operation on the circuit breaker body according to the instructions received from the control system circuit.

A human-computer interaction interface, the interaction interface includes an LCD display, control buttons and a communication system, which are used to display the status of the circuit breaker and control the action of the circuit breaker.

In the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the signal acquisition system includes a first voltage sensor for measuring the line voltage signal of the DC transmission system, a first sensor for measuring the line current signal of the DC transmission system Current sensor, displacement sensor for measuring the opening and closing state of the contacts of the circuit breaker body and contact displacement information, the second voltage sensor for respectively measuring the capacitive voltage signal of the drive circuit of the repulsion mechanism as the operating mechanism, and measuring the drive of the repulsion mechanism as the operating mechanism The second current sensor for the current signal of the loop and the temperature sensor for measuring the working environment temperature of the circuit breaker.

In the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the mechanical switch is a high-speed mechanical switch based on electromagnetic repulsion, a high-speed motor-driven mechanical switch or an explosion-driven high-speed mechanical switch.

In the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the driving circuit of the repulsion mechanism uses LC oscillation mode as the driving repulsion mechanism movement, wherein the DC power supply is connected in series with the charging resistor Rq and then connected in parallel with the discharge capacitor At both ends of Cq, the freewheeling diode Dq is connected in parallel to both ends of the discharge capacitor, where the diode cathode is connected to the capacitor anode, and the diode anode is connected to the capacitor cathode; the control thyristor Tq anode is connected to the discharge capacitor anode, the cathode is connected to the discharge coil, and the other end of the coil is connected to The negative terminal of the discharge capacitor is connected.

In the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the repulsion mechanism is controlled by the controller optical fiber, and the opening and closing operations of the DC circuit breaker are completed according to the command of the control system, and the mechanical delay is 450us within.

In the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the control system includes a digital signal input circuit, a processor, a digital signal output circuit, a photoelectric signal output circuit, a drive circuit, a relay and a power supply circuit.

In the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the signal processing system includes a filter circuit, an amplifier circuit, an A/D converter and a power supply, and the AD converter is a high-speed AD, sampling The frequency is above 650k.

In the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the signal acquisition system collects voltage and current signals in real time, and after signal processing by the signal processing system, they are input into the control system in real time through parallel communication.

In the bidirectional hybrid DC circuit breaker for medium-voltage distribution network, the control system judges the short-circuit fault by comparing the current and the short-circuit threshold, analyzes the current direction of the main current loop, and outputs an optical signal to control the circuit breaker to open and close Operate and record fault current and voltage waveforms and communicate with the host computer, the man-machine interface, control keys and communication system. The LCD display screen displays system voltage, current state and/or drive circuit capacitor voltage state in real time, and the control buttons include an opening instruction button, a closing instruction button and/or a discharge button.

According to another aspect of the present invention, a breaking method using the bidirectional hybrid DC circuit breaker for medium voltage distribution network includes the following steps:

In the first step, current flows through the mechanical switches S1 and S2 in the normal on-current state.

In the second step, when a short-circuit fault occurs in the system, an opening command is issued, the operating mechanism starts to open, the thyristor T2 and thyristor T3 are triggered to conduct, and the current starts to transfer to the bridge circuit.

In the third step, after a certain delay, the mechanical switch S2 is turned on to generate an arc, and the oscillating current generated by the oscillating circuit forces the current of the main current circuit to cross zero. When the current of the main current circuit crosses zero, the mechanical switch turns off the arc and the main current circuit is broken open.

In the fourth step, the system begins to charge the transfer capacitor of the bridge circuit, and the voltage across the circuit breaker continues to rise. When the voltage exceeds the conduction threshold of the overvoltage limiting branch, the overvoltage limiting branch is turned on. Due to the overvoltage The homomorphic impedance of the limiting branch is very small, and the current begins to transfer to the overvoltage limiting branch.

In the fifth step, as the current is gradually transferred to the overvoltage limiting branch, the current of the bridge circuit gradually decreases, and after decreasing to zero, the thyristors T2 and T3 are turned off at zero crossing, and the current is completely transferred to the overvoltage limiting branch , because the system voltage is less than the conduction threshold of the overvoltage limiting branch, the overvoltage limiting branch will soon return to the high-impedance state, and the entire breaking process is completed.

The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer, to the extent that those skilled in the art can implement it according to the contents of the description, and to enable the above and other purposes of the present invention, The features and advantages can be more obvious and understandable, and the specific implementation manners of the present invention are illustrated below for illustration.

Description of drawings

Various other advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings in the description are for the purpose of illustrating preferred embodiments only and are not to be considered as limiting the invention. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to these drawings without creative efforts. Also throughout the drawings, the same reference numerals are used to denote the same parts.

In the attached picture:

Fig. 1 is an overall block diagram of a bidirectional hybrid DC circuit breaker for a medium voltage distribution network according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of the overall work flow of a bidirectional hybrid DC circuit breaker for a medium voltage distribution network according to an embodiment of the present invention;

Fig. 3 is a schematic structural view of a circuit breaker body of a bidirectional hybrid DC circuit breaker for a medium voltage distribution network according to an embodiment of the present invention;

Figure 4(a)-Figure 4(e) is a schematic diagram of the breaking process of a bidirectional hybrid DC circuit breaker according to an embodiment of the present invention;

Fig. 5 is a schematic diagram of steps of a breaking method using a bidirectional hybrid DC circuit breaker for a medium voltage distribution network according to an embodiment of the present invention.

The present invention will be further explained below in conjunction with the accompanying drawings and embodiments.

Detailed ways

Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and is not limited to the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art should understand that they may use different terms to refer to the same component. The specification and claims do not use differences in nouns as a way of distinguishing components, but use differences in functions of components as a criterion for distinguishing. "Includes" or "comprises" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". The subsequent description in the specification is a preferred implementation mode for implementing the present invention, but the description is for the purpose of the general principles of the specification, and is not intended to limit the scope of the present invention. The scope of protection of the present invention should be defined by the appended claims.

In order to facilitate the understanding of the embodiments of the present invention, several specific embodiments will be taken as examples for further explanation below in conjunction with the accompanying drawings, and each drawing does not constitute a limitation to the embodiments of the present invention.

Fig. 1 is an overall block diagram of a bidirectional hybrid DC circuit breaker for a medium voltage distribution network according to an embodiment of the present invention. The embodiment of the present invention will be described in detail with reference to Fig. 1 .

As shown in Figure 1, an embodiment of the present invention provides a bidirectional hybrid DC circuit breaker for medium voltage distribution network, a bidirectional hybrid DC circuit breaker for medium voltage distribution network, the bidirectional hybrid Type DC circuit breaker includes circuit breaker body, signal acquisition system, signal processing system, control system, operating mechanism and human-computer interaction interface.

Fig. 3 is a schematic structural diagram of a circuit breaker body of a bidirectional hybrid DC circuit breaker for a medium voltage distribution network according to an embodiment of the present invention. As shown in Fig. 3, the circuit breaker body includes a main current circuit, a bridge circuit , an oscillation branch, an overvoltage limiting branch and an isolation switch V1, wherein the main current circuit is composed of two mechanical switches S1 and S2 in series, wherein one end of S1 is loaded on the outlet A1, and one end of S2 is connected to the outlet A2.

The bridge circuit is composed of power diodes D1, D2 and thyristors T1, T2, T3, T4, among which, D1 is connected in parallel at both ends of mechanical switch S1, D2 is connected in parallel at both ends of S2, the positive pole of D1 is connected with the outgoing terminal of A1, and the positive pole of D2 is isolated through isolation. The switch V1 is connected to the outlet terminal of A2, the negative poles of D1 and D2 are connected to the common terminal of the mechanical switch, the positive poles of the thyristors T1 and T2 are connected, the negative poles are respectively connected to the outgoing terminal A1 and the isolation switch V1, the negative poles of the thyristors T3 and T4 are connected to each other, and the positive poles are respectively connected to the On the outlet terminal A1 and the isolating switch V1.

The oscillating branch is composed of a transfer capacitor C and an oscillating inductance L in series, wherein the non-common terminals of the oscillating inductance L are connected to the common terminals of the thyristors T3 and T4, and the non-common terminals of the transfer capacitor C are connected to the thyristors T1 and T2.

The overvoltage limiting branch is connected in parallel to both ends of the mechanical switches S1 and S2, and connected to the outgoing terminal A1 and the isolation switch V1 respectively.

Figure 2 is a schematic diagram of the overall working process of a bidirectional hybrid DC circuit breaker for medium voltage distribution network according to an embodiment of the present invention, as shown in Figure 2, the signal acquisition system, the signal acquisition system collects the circuit breaker body The voltage value, current value, current direction, the voltage value, current value, working environment temperature of the driving circuit of the repulsion mechanism as the operating mechanism, the opening and closing status of the circuit breaker mechanism, and the contact displacement information.

A signal processing system, the signal processing system processes the signal collected by the signal collection system, including filtering, amplification and/or A/D conversion.

A control system, the control system receives the signal processed by the signal processing system, completes the analysis of the voltage signal, current signal, and current rise rate, and detects the system short-circuit fault, and controls the opening and closing operations of the operating mechanism according to the analysis results.

An operating mechanism, the operating mechanism performs an opening or closing operation on the circuit breaker body according to the instructions received from the control system circuit.

A human-computer interaction interface, the interaction interface includes an LCD display, control buttons and a communication system, which are used to display the status of the circuit breaker and control the action of the circuit breaker.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the signal acquisition system includes a first voltage sensor for measuring the line voltage signal (U ₁ ) of the DC transmission system, a first voltage sensor for measuring the DC transmission system The first current sensor for the line current signal (I ₁ ) of the system, the displacement sensor for measuring the opening and closing state of the contacts of the circuit breaker body and the displacement information of the contacts, and the capacitance voltage signal (U ₂ ) the second voltage sensor, the second current sensor for measuring the current signal (I ₂ ) of the driving circuit of the repulsion mechanism as the operating mechanism, and the temperature sensor for measuring the working environment temperature of the circuit breaker.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the mechanical switch is a high-speed mechanical switch based on electromagnetic repulsion, a high-speed motor-driven mechanical switch or an explosion-driven high-speed mechanical switch. switch.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the driving circuit of the repulsion mechanism uses LC oscillation mode as the driving repulsion mechanism, wherein, after the DC power supply is connected in series with the charging resistor Rq It is connected in parallel at both ends of the discharge capacitor Cq, and the freewheeling diode Dq is connected in parallel at both ends of the discharge capacitor, wherein the cathode of the diode is connected to the positive electrode of the capacitor, and the anode of the diode is connected to the negative electrode of the capacitor; the positive electrode of the control thyristor Tq is connected to the positive electrode of the discharge capacitor, and the negative electrode is connected to the discharge coil. The other end of the coil is connected to the negative pole of the discharge capacitor.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the repulsion mechanism is controlled by the optical fiber of the controller, and the opening and closing operations of the DC circuit breaker are completed according to the command of the control system. The mechanical delay is within 450us.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the control system includes a digital signal input circuit, a processor, a digital signal output circuit, a photoelectric signal output circuit, a drive circuit, a relay and power supply circuit.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the signal processing system includes a filter circuit, an amplification circuit, an A/D converter and a power supply, and the AD converter is High-speed AD, the sampling frequency is above 650k.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the signal acquisition system collects voltage and current signals in real time, and after signal processing by the signal processing system, the signals are input and controlled in real time by means of parallel communication. system.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker used in the medium voltage distribution network, the control system judges the short circuit fault by comparing the current and the short circuit threshold, analyzes the current direction of the main current loop, and outputs an optical signal to control the circuit breaker Perform opening and closing operations, record fault current and voltage waveforms, and communicate with the host computer. The human-computer interaction interface controls buttons and communication systems. The LCD display screen displays system voltage, current state and/or drive circuit capacitor voltage state in real time, and the control buttons include an opening instruction button, a closing instruction button and/or a discharge button.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the control system includes a processor, and the processor is a general processor, a digital signal processor, an application specific integrated circuit ASIC or Field Programmable Gate Array FPGA.

In the preferred embodiment of the bidirectional hybrid DC circuit breaker for medium voltage distribution network, the processor includes a memory, and the memory may include one or more read-only memory ROM, random access memory RAM, Flash memory or Electronically Erasable Programmable Read Only Memory EEPROM.

Fig. 4(a) - Fig. 4(e) are schematic diagrams of the breaking process of a bidirectional hybrid DC circuit breaker according to an embodiment of the present invention, and the breaking process will be described below in conjunction with Fig. 4(a) - (e).

As mentioned in the previous background, the bidirectional hybrid DC circuit breaker applied to the DC transmission system does not have a current zero-crossing point during the breaking process. Compared with the general power frequency AC system, it is more difficult to break. The invention creates artificial current zero-crossing point by connecting LC oscillation branches in parallel, and realizes direct current breaking. The following will describe the DC breaking process when the current flows from the outlet terminal A1 to the outlet terminal A in combination with the specific circuit diagram:

(1) As shown in Fig. 4(a), in the normal flow-through state, the current flows through the mechanical switches S1 and S2, and the on-state loss is small.

(2) As shown in Figure 4(b), when a short-circuit fault occurs in the system and the control system detects a short-circuit fault in the DC system, it issues an opening command, the operating mechanism starts to open, and the thyristor T2 and thyristor T3 trigger conduction , the current begins to divert to the bridge circuit.

(3) As shown in Figure 4(c), after a certain delay, the mechanical switch S2 is turned on to generate an arc, and the oscillating current generated by the oscillating circuit forces the current of the main current circuit to cross zero. When the current of the main current circuit crosses zero, the mechanical switch The arc is extinguished and the main current circuit is disconnected.

(4) As shown in Figure 4(d), the DC system begins to charge the transfer capacitor of the bridge circuit, and the voltage across the circuit breaker continues to rise. When the voltage exceeds the conduction threshold of the overvoltage limiting branch, the overvoltage limiting The branch is turned on, because the homomorphic impedance of the overvoltage limiting branch is very small, the current begins to transfer to the overvoltage limiting branch.

(5) As shown in Figure 4(a)-Figure 4(e), as the current gradually shifts to the overvoltage limiting branch, the current of the bridge circuit gradually decreases, and after decreasing to zero, the thyristors T2 and T3 overshoot Zero turn-off, the current is completely transferred to the overvoltage limiting branch;

(6) Since the system voltage is lower than the conduction threshold of the overvoltage limiting branch, the arrester quickly returns to the high-impedance state, and the entire breaking process is completed. At this time, after detecting that the system current is zero, open the mechanism S1 and the isolation switch V1.

In the present invention, the opening process is further described with reference to FIGS. 1 and 2 . The invention includes a signal acquisition system, a signal processing system, a control system, a human-computer interaction interface and a circuit breaker body. The signal acquisition system includes the first voltage sensor for collecting the voltage U1 of the DC transmission system, the first current sensor for collecting the line current information I1 of the system, the displacement sensor for collecting the opening and closing information of the circuit breaker contacts, and the second sensor for collecting the driving circuit voltage U2 A voltage sensor, a second current sensor for collecting current information I2 of the drive circuit, and a temperature sensor for collecting ambient temperature information around the circuit breaker. The signal processing system processes the collected physical information, including filtering and amplifying the signal, and then performs analog-to-digital conversion through a high-speed AD converter with a sampling path of up to 650K. After the analog-to-digital conversion is completed, the processing result is output to control system for processing. The control system separately calculates the voltage, current amplitude, current flow direction, and current rise rate of the DC transmission system, and analyzes whether the system is short-circuited by comparing the current with the set threshold value and analyzing the current rise rate. The control system includes but not limited to the following parts: digital signal input circuit, processor, digital signal output circuit, relay and power supply. The operating mechanism includes an electromagnetic repulsion mechanism. The thyristor T2 of the driving circuit of the repulsion mechanism is controlled by the optical signal of the controller to trigger the opening and closing operation of the control mechanism, and the mechanical delay is within 450us.

Changes in ambient temperature will cause fluctuations in the output voltage of the DC power supply. As the voltage and current of the drive circuit change, the delay of the repulsion mechanism will change accordingly. Therefore, the control of the compensation mechanism through the ambient temperature and the voltage value of the discharge capacitor can be accurately controlled. Control the action of the repulsion mechanism to achieve more accurate opening and closing operations. This process includes: the signal acquisition system collects the driving circuit voltage signal and the circuit breaker temperature signal through the driving capacitor voltage, current sensor and ambient temperature sensor, and outputs them to the signal processing system. After the signal processing system receives the signal, it completes the filtering, amplification, and A/D conversion operations, and outputs it to the control system. After the control system receives the temperature and voltage signals, it compares the delay characteristics of the repulsion mechanism stored in the control system with the delay curve of the voltage and current corresponding to the ambient temperature, and calculates the action delay of the repulsion mechanism accurately through linear interpolation. At the same time, according to the delay of the repulsive force mechanism, as well as the current and voltage values, and the current rising rate, the accurate opening time of the mechanism is calculated to realize accurate control of the mechanism.

The signals collected by the above three sensors are the same as other signals of the above-mentioned signal acquisition circuit, and are also input to the signal processing circuit. The filter circuit, amplifier circuit and AD in the signal processing system can be connected to multiple channels of acquisition at the same time. signal is processed. After processing, the signal is sent to the control system. The control system circuit combines the measured voltage value of the driving circuit and the collected ambient temperature of the circuit breaker to compensate the predicted line current zero-crossing time, and then adjust the delay time of the mechanism action to achieve precise control of the repulsion mechanism and drive the circuit breaker The contacts open at a given moment.

Fig. 5 is a schematic diagram of steps of a breaking method using a bidirectional hybrid DC circuit breaker for a medium voltage distribution network according to an embodiment of the present invention, a kind of said bidirectional hybrid DC circuit breaker for a medium voltage distribution network The breaking method includes the following steps:

In a first step S1, in a normal flow-through state, current flows through the mechanical switches S1 and S2.

In the second step S2, when a short-circuit fault occurs in the system, an opening command is issued, the operating mechanism starts to open, the thyristor T2 and the thyristor T3 are triggered to conduct, and the current starts to transfer to the bridge circuit.

In the third step S3, after a certain delay, the mechanical switch S2 is turned on to generate an arc, and the oscillating current generated by the oscillating circuit forces the current of the main current loop to cross zero. When the current of the main current loop crosses zero, the mechanical switch extinguishes the arc, and the main current loop disconnect.

In the fourth step S4, the system starts to charge the transfer capacitor of the bridge circuit, and the voltage across the circuit breaker continues to rise. When the voltage exceeds the conduction threshold of the overvoltage limiting branch, the overvoltage limiting branch is turned on. The homomorphic impedance of the voltage limiting branch is very small, and the current begins to shift to the overvoltage limiting branch.

In the fifth step S5, as the current gradually shifts to the overvoltage limiting branch, the current of the bridge circuit gradually decreases, and after decreasing to zero, the thyristors T2 and T3 are turned off at zero crossing, and the current is completely transferred to the overvoltage limiting branch. Since the system voltage is lower than the conduction threshold of the overvoltage limiting branch, the overvoltage limiting branch will soon return to the high-impedance state, and the entire disconnection process is completed.

Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative, instructive, and not restrictive . Under the enlightenment of this description and without departing from the protection scope of the claims of the present invention, those skilled in the art can also make many forms, which all belong to the protection of the present invention.

Claims (10)

1. A bidirectional hybrid DC circuit breaker for medium voltage distribution network, the bidirectional hybrid DC circuit breaker includes a circuit breaker body, a signal acquisition system, a signal processing system, a control system, an operating mechanism and a human-computer interaction interface, It is characterized by: The circuit breaker body includes a main current circuit, a bridge circuit, an oscillation branch, an overvoltage limiting branch and an isolating switch V1, wherein: The main current circuit is composed of two mechanical switches S1 and S2 connected in series, wherein one end of S1 is loaded on the outgoing terminal A1, and one end of S2 is connected to the outgoing terminal A2; The bridge circuit is composed of power diodes D1, D2 and thyristors T1, T2, T3, T4, wherein, D1 is connected in parallel at both ends of mechanical switch S1, D2 is connected in parallel at both ends of S2, the positive pole of D1 is connected with the outlet terminal A1, and the positive pole of D2 is isolated The switch V1 is connected to the outlet terminal A2, the negative poles of D1 and D2 are connected to the common terminal of the mechanical switch, the positive poles of the thyristors T1 and T2 are connected, the negative poles are respectively connected to the common terminal of the outgoing terminal A1 and the positive poles of the isolating switch V1 and D2, and the negative poles of the thyristors T3 and T4 Connected, the positive pole is respectively connected to the outlet terminal A1 and the common terminal of the positive pole of the isolation switch V1 and D2; The oscillating branch is composed of a transfer capacitor C and an oscillating inductance L connected in series, wherein the non-common terminals of the oscillating inductance L are connected to the common terminals of the thyristors T3 and T4, and the non-common terminals of the transfer capacitor C are connected to the common terminals of the thyristors T1 and T2; The overvoltage limiting branch is connected in parallel at both ends of the mechanical switch S1 and S2, respectively connected to the outgoing terminal A1 and the common terminal of the positive poles of the isolating switch V1 and D2; A signal acquisition system, the signal acquisition system collects the voltage value, current value, and current direction of the circuit breaker body, the voltage value, current value, and working environment temperature of the drive circuit of the repulsion mechanism as the operating mechanism, as well as the breakdown of the circuit breaker mechanism. Brake, closing status and contact displacement information; A signal processing system, the signal processing system processes the signal collected by the signal collection system, including filtering, amplification and/or A/D conversion; A control system, the control system receives the signal processed by the signal processing system, completes the analysis of the voltage signal, current signal, and current rise rate, and detects the system short-circuit fault, and controls the operating mechanism to open and close according to the analysis results; An operating mechanism, the operating mechanism performs opening or closing operations on the circuit breaker body according to the received instructions of the control system circuit; A human-computer interaction interface, the interaction interface includes an LCD display, control buttons and a communication system, which are used to display the status of the circuit breaker and control the action of the circuit breaker. 2. The bidirectional hybrid DC circuit breaker for medium voltage distribution network according to claim 1, characterized in that: the signal acquisition system includes a first voltage sensor for measuring the line voltage signal (U ₁ ) of the DC transmission system , the first current sensor for measuring the line current signal (I ₁ ) of the DC transmission system, the displacement sensor for measuring the opening and closing state of the contacts of the circuit breaker body and the displacement information of the contacts, and respectively measuring the capacitance of the drive circuit of the repulsion mechanism as the operating mechanism The second voltage sensor for the voltage signal (U ₂ ), the second current sensor for measuring the current signal (I ₂ ) of the driving circuit of the repulsion mechanism as the operating mechanism, and the temperature sensor for measuring the working environment temperature of the circuit breaker. 3. The bidirectional hybrid DC circuit breaker for medium voltage distribution network according to claim 1, characterized in that: the mechanical switch is a high-speed mechanical switch based on electromagnetic repulsion, a high-speed motor-driven mechanical switch or an explosion-based actuated high-speed mechanical switches. 4. The bidirectional hybrid DC circuit breaker for medium voltage distribution network according to claim 1, characterized in that: the driving circuit of the repulsion mechanism uses LC oscillation mode as the driving repulsion mechanism movement, wherein the DC power supply and charging The resistor Rq is connected in parallel to both ends of the discharge capacitor Cq after being connected in series, and the freewheeling diode Dq is connected in parallel to both ends of the discharge capacitor Cq, wherein the negative pole of the freewheeling diode Dq is connected to the positive pole of the discharge capacitor Cq, and the positive pole of the freewheeling diode Dq is connected to the negative pole of the discharge capacitor Cq; The positive pole of the thyristor Tq is connected to the positive pole of the discharge capacitor Cq, the negative pole is connected to the discharge coil, and the other end of the coil is connected to the negative pole of the discharge capacitor Cq. 5. The bidirectional hybrid DC circuit breaker for medium voltage distribution network according to claim 1, characterized in that: the repulsion mechanism is controlled by the controller optical fiber, and the switching and closing of the DC circuit breaker is completed according to the command of the control system Gate operation, its mechanical delay is within 450us. 6. The bidirectional hybrid DC circuit breaker for medium voltage distribution network according to claim 1, characterized in that: the control system includes a digital signal input circuit, a processor, a digital signal output circuit, a photoelectric signal output circuit, Drive circuits, relays and power supply circuits. 7. The bidirectional hybrid DC circuit breaker for medium voltage distribution network according to claim 1, characterized in that: the signal processing system includes a filter circuit, an amplifier circuit, an A/D converter and a power supply, and the The AD converter is a high-speed AD, and the sampling frequency is above 650k. 8. The bidirectional hybrid DC circuit breaker for medium voltage distribution network according to claim 1, characterized in that: the signal acquisition system collects voltage and current signals in real time, and uses parallel communication after signal processing by the signal processing system The method is input into the control system in real time. 9. The bidirectional hybrid DC circuit breaker for medium-voltage distribution network according to claim 1, characterized in that: the control system judges short-circuit faults by comparing current and short-circuit thresholds, analyzes the current direction of the main current loop, and outputs light The signal controls the circuit breaker to perform opening and closing operations, record fault current and voltage waveforms, and communicate with the host computer. The human-computer interaction interface includes an LCD display, control buttons and a communication system. The LCD display displays the system voltage and current status in real time and/or the capacitor voltage state of the drive circuit, the control buttons include an opening command button, a closing command button and/or a discharge button. 10. A breaking method using the bidirectional hybrid DC circuit breaker for medium voltage distribution network according to any one of claims 1-9, comprising the following steps: In the first step (S1), the current flows through the mechanical switches S1 and S2 in a normal flow-through state; In the second step (S2), when a short-circuit fault occurs in the system is detected, an opening command is issued, the operating mechanism starts to open, the thyristor T2 and the thyristor T3 trigger conduction, and the current starts to transfer to the bridge circuit; In the third step (S3), after a certain delay, the mechanical switch S2 is opened to generate an arc, and the oscillating current generated by the oscillating circuit forces the current of the main current loop to cross zero. When the current of the main current loop crosses zero, the mechanical switch S2 turns off the arc. The main current circuit is disconnected; In the fourth step (S4), the system begins to charge the transfer capacitor, and the voltage across the circuit breaker continues to rise. When the voltage exceeds the conduction threshold of the overvoltage limiting branch, the overvoltage limiting branch is turned on. Due to the overvoltage limiting The homomorphic impedance of the branch is very small, and the current begins to transfer to the overvoltage limiting branch; In the fifth step (S5), as the current gradually shifts to the overvoltage limiting branch, the current of the bridge circuit gradually decreases, and after decreasing to zero, the thyristors T2 and T3 are turned off at zero crossing, and the current is completely transferred to the overvoltage Limiting branch, because the system voltage is lower than the conduction threshold of the overvoltage limiting branch, the overvoltage limiting branch will soon return to the high-impedance state, and the entire breaking process is completed.