DC power transmission driving circuit and control method thereof

Abstract

The invention provides a direct-current transmission driving circuit and a control method thereof, relates to the technical field of direct-current transmission driving circuits, and can freely switch the direct-current transmission driving circuit when the direct-current transmission driving circuit needs to be overhauled or breaks down, thereby simplifying the switching difficulty of the operation mode of the direct-current transmission circuit, and improving the reliability of the direct-current transmission driving circuit. In the switching process of the operation modes, waste of electric energy is avoided, the operation cost of the direct-current power transmission circuit is reduced, and the switching efficiency of the direct-current power transmission circuit is improved. The direct current transmission driving circuit comprises a negative electrode metal loop, a ground loop and a positive electrode metal loop, and a first conduction unit is used for controlling connection and disconnection between the negative electrode metal loop and the ground loop according to the voltage of the first end of the ground loop and the voltage of the second end of the negative electrode metal loop, the anode metal return wire comprises a second conduction unit which is used for controlling the connection and disconnection between the cathode metal return wire and the anode metal return wire, and the first conduction unit and the second conduction unit are alternately conducted.

Description

Technical Field

[0001] The present application relates to the technical field of direct current transmission drive circuits, and in particular to a direct current transmission drive circuit and a control method thereof. Background Art

[0002] In a DC transmission system, when line maintenance or line faults occur, it is necessary to switch the system operation mode to ensure that the DC transmission system can avoid faulty circuits and circuits to be repaired to transmit electricity, thereby ensuring the normal operation of the DC transmission system.

[0003] However, in the process of switching the operating mode of the traditional DC transmission system, the switching method is complicated, and the traditional DC transmission circuit has problems such as wasting electric energy during the operation process, which further wastes electric energy. It is necessary to install electrical components such as lightning protection groups to ensure the normal operation of the DC transmission system. The lightning protection group will further absorb the electric energy in the DC power, increase the cost of DC transmission and increase the difficulty of switching the DC transmission system, thereby reducing the switching efficiency of the DC transmission system. Summary of the invention

[0004] Based on this, it is necessary to provide a DC transmission drive circuit and a control method thereof to address the above technical issues.

[0005] In a first aspect, the present application provides a direct current transmission drive circuit, comprising:

[0006] Negative metal return line;

[0007] an earth return line, wherein a first end of the earth return line is electrically connected to a first end of the negative metal return line, and a second end of the earth return line is electrically connected to a second end of the negative metal return line;

[0008] A positive metal loop line, wherein the first end of the positive metal loop line is connected between the first end of the earth loop line and the first end of the negative metal loop line, and the second end of the positive metal loop line is connected between the second end of the earth loop line and the second end of the negative metal loop line;

[0009] A first conduction unit, located between the first end of the earth return line and the first end of the positive metal return line, is used to control the connection between the negative metal return line and the earth return line according to the voltage of the first end of the earth return line and the voltage of the second end of the negative metal return line;

[0010] Wherein, the positive metal loop line includes a second conduction unit for controlling the connection and disconnection between the negative metal loop line and the positive metal loop line;

[0011] The first conducting unit and the second conducting unit are alternately turned on.

[0012] In one of the embodiments, when the voltage at the first end of the earth return line is less than the voltage at the second end of the negative metal return line, the first conduction unit is disconnected;

[0013] When the voltage at the first end of the positive metal loop is lower than the voltage at the second end of the negative metal loop, the second conduction unit is turned off.

[0014] In one embodiment, the DC power transmission drive circuit further includes:

[0015] A first rectifier, wherein an output end of the first rectifier is electrically connected to a first end of the first conductive unit away from the earth return line, an input end of the first rectifier is electrically connected to a first end of the negative metal return line, and the first rectifier is used to convert an input AC voltage into a DC voltage output;

[0016] A second rectifier, wherein an input end of the second rectifier is electrically connected to a first end of the first conductive unit away from the earth return line and an output end of the first rectifier, and an output end of the second rectifier is electrically connected to an end of the second conductive unit away from the earth return line;

[0017] a first inverter, wherein an input end of the first inverter is electrically connected to a second end of the earth return line, and an output end of the first inverter is electrically connected to a second end of the negative metal return line;

[0018] A second inverter, wherein the input end of the second inverter is electrically connected to the second end of the positive metal return line, and the output end of the second inverter is electrically connected to the second end of the earth return line and the input end of the first inverter.

[0019] In one embodiment, the DC power transmission drive circuit further includes:

[0020] a third conducting unit, one end of the third conducting unit being electrically connected to the input end of the second rectifier, and the other end of the third conducting unit being electrically connected to the first end of the first conducting unit away from the earth return line and the output end of the first rectifier;

[0021] When the voltage value of the first end of the positive metal loop is less than the voltage value of the second end of the negative metal loop, the third conduction unit is turned off.

[0022] In one embodiment, the DC power transmission drive circuit further includes:

[0023] a fourth conduction unit, one end of the fourth conduction unit being electrically connected to the output end of the second inverter, and the other end of the fourth conduction unit being electrically connected to the second end of the earth return line and the input end of the first inverter;

[0024] When the voltage value of the first end of the positive metal loop is less than the voltage value of the second end of the negative metal loop, the fourth conduction unit is turned off.

[0025] In one embodiment, the first conduction unit, the second conduction unit, the third conduction unit and the fourth conduction unit are all vacuum switches.

[0026] In one embodiment, the positive metal return line further includes:

[0027] a fifth conducting unit, wherein a first end of the fifth conducting unit is electrically connected to the second conducting unit, and a second end of the fifth conducting unit is electrically connected to a second end of the earth return line;

[0028] A sixth conducting unit is located between the fifth conducting unit and the second end of the earth return line.

[0029] In a second aspect, the present application provides a control method for a DC power transmission drive circuit, which is applied to the DC power transmission drive circuit described in any one of the first aspects, and the method includes:

[0030] closing the first conduction unit;

[0031] Disconnecting the second conduction unit;

[0032] Acquire a first control instruction of the DC power transmission drive circuit, wherein the first control instruction is used to control the earth return line to be electrically connected to the negative metal return line, and to control the positive metal return line to be disconnected from the negative metal return line;

[0033] According to the first control instruction, the voltage value of the first end of the positive metal loop is controlled to be smaller than the voltage value of the second end of the negative metal loop, so that the third conduction unit and the fourth conduction unit are disconnected, so that the earth loop and the negative metal loop form a loop.

[0034] In one embodiment, the control method of the DC power transmission drive circuit further includes:

[0035] closing the second conducting unit;

[0036] Acquire a second control instruction of the DC power transmission drive circuit, wherein the second control instruction is used to control the electrical connection between the positive metal return line and the negative metal return line, and to control the disconnection between the negative metal return line and the earth return line;

[0037] According to the second control instruction, the voltage value of the first end of the earth return line is controlled to be smaller than the voltage value of the second end of the negative metal return line, so that the first conduction unit is disconnected, so that the positive metal return line and the negative metal return line form a loop.

[0038] In one embodiment, the control method of the DC power transmission drive circuit further includes:

[0039] closing the third conducting unit and the fourth conducting unit;

[0040] closing the first conducting unit;

[0041] A third control instruction of the DC power transmission drive circuit is obtained, wherein the third control instruction is used to control the voltage value of the first end of the positive metal loop to be less than the voltage value of the second end of the negative metal loop, so that the second conduction unit is disconnected, so that the positive metal loop and the negative metal loop form a loop.

[0042] The DC power transmission drive circuit and control method provided in the embodiment of the present application are electrically connected through the first end of the negative metal loop to the first end of the earth loop, and the second end of the negative metal loop to the second end of the earth loop, so that the negative metal loop and the earth loop form a loop. When the DC power transmission drive circuit needs to be repaired or fails, the current in the negative metal loop can be derived through the earth loop to facilitate the repair of the positive metal loop. The first end of the positive metal loop is connected between the first end of the earth loop and the first end of the negative metal loop, and the second end of the positive metal loop is connected between the second end of the earth loop and the second end of the negative metal loop, so that the positive metal loop can form a loop with the earth loop and the negative metal loop respectively, and the positive metal loop and the negative metal loop are used to transmit electricity. At the same time, the DC power transmission circuit can be grounded, which can ensure the normal operation of the DC power transmission circuit. Furthermore, a first conduction unit is provided between the first end of the earth loop and the first end of the positive metal loop, and a second conduction unit is provided in the positive metal loop. The first conduction unit can be used to automatically control the on-off between the negative metal loop and the earth loop by the voltage of the first end of the earth loop and the voltage of the second end of the negative metal loop. The switching of different conduction loops in the DC transmission circuit can also be achieved by controlling the alternating conduction of the first conduction unit and the second conduction unit. Thus, the difficulty of switching the operation mode of the DC transmission circuit can be simplified through the automatic control function of the first conduction unit, and in the process of switching the operation mode, the waste of electric energy can be avoided, the cost of the operation of the DC transmission circuit can be reduced, and the switching efficiency of the DC transmission circuit can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the conventional technology, the drawings required for use in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 is a schematic circuit diagram of a direct current transmission drive circuit provided in an embodiment of the present application;

[0045] Figure 2 is a flow chart of a control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0046] Figure 3 is a circuit diagram of a control method for a DC power transmission drive circuit provided in an embodiment of the present application;

[0047] Figure 4 is a circuit diagram of another control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0048] Figure 5 is a current variation diagram in a control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0049] Figure 6 is a flow chart of another control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0050] Figure 7 is a circuit diagram of another control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0051] Figure 8 is a circuit diagram of another control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0052] Fig. 9 is a current variation diagram in another control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0053] Fig.10 is a flow chart of another method for controlling a DC power transmission drive circuit provided in an embodiment of the present application;

[0054] Fig.11 is a circuit diagram of another control method of a DC power transmission drive circuit provided in an embodiment of the present application;

[0055] Fig.12 is a circuit diagram of a control method for a DC power transmission drive circuit provided in an embodiment of the present application;

[0056] Fig.13 This is a current variation diagram in another control method of a DC power transmission drive circuit provided in an embodiment of the present application.

[0057] Description of reference numerals:

[0058] 100, negative metal return line; 200, earth return line; 300, positive metal return line; 400, first rectifier; 500, second rectifier; 600, first inverter; 700, second inverter; 800, neutral bus. DETAILED DESCRIPTION

[0059] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0061] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that when the terms "consisting of" and / or "comprising" are used in this specification, the presence of the features, integers, elements and / or components may be determined, but the presence or addition of one or more other features, integers, elements, components and / or groups is not excluded. At the same time, when used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0062] In the DC transmission system, when the line is under maintenance or when a line fault occurs, the system operation mode needs to be switched to ensure that the DC transmission system can avoid the faulty circuit and the circuit to be repaired for power transmission, thereby ensuring the normal operation of the DC transmission system. During the switching process of the operation mode of the traditional DC transmission system, each transmission line is electrically connected to the isolating switch through a DC conversion switch. According to the different installation positions of the switches, the DC conversion switches in the UHV conventional DC transmission project can be divided into metal return line conversion switches, earth return line conversion switches, multiple neutral bus switches and neutral bus grounding switches. The metal return line conversion switch is installed between the neutral bus and the grounding pole of the rectifier station, and can convert the load current from the grounding pole to the positive or negative metal return line. The earth return line conversion switch is installed between the neutral bus and the positive metal return line and the negative metal return line of the rectifier station, and can convert the load current from the positive metal return line or the negative metal return line to the grounding pole line. Multiple neutral bus switches are installed between the neutral bus and the positive and negative converters of the rectifier station and the inverter station. When the circuit is out of service, the converter will reduce the current to zero, and the neutral bus switch will open without arcing. When there is a grounding fault inside the converter, the fault pole bypass pair is locked, and the neutral bus switch converts the current injected into the fault point by the normal pole to the grounding pole line. Two neutral bus grounding switches are installed between the neutral bus and the grounding grid of the rectifier station and the inverter station respectively. When the grounding pole line is disconnected due to a fault, the neutral bus grounding switch is closed to provide a grounding point for the DC system, so that the unbalanced current of the positive and negative poles flows through the grounding grid. When the grounding pole line returns to normal, the neutral bus grounding switch converts the unbalanced current to the grounding pole line. In addition, multiple isolating switches are installed between the neutral bus and the positive and negative metal return lines of the rectifier station and the inverter station respectively. The isolating switches can cooperate with the earth return line conversion switch to complete the current conversion between the earth return line and the positive and negative metal return lines.

[0063] The DC conversion switch in traditional technology consists of a flow branch, a commutation branch and an energy absorption branch. The flow branch is generally composed of an AC circuit breaker, the commutation branch is composed of an inductor-capacitor oscillation circuit, and the energy absorption branch is composed of a lightning arrester group. The working process of the DC conversion switch to convert current is as follows: in response to the trip signal, the AC circuit breaker starts the contact separation, the internal arc resistance undergoes a nonlinear change, and an unstable arc voltage is generated. The inductor-capacitor loop generates an oscillating current with a gradually increasing amplitude. When the current superimposed on the flow branch passes through zero, the arc is extinguished and the load current is transferred to the commutation branch. The commutation branch current charges the capacitor, and the voltage across the lightning arrester continues to rise. When the voltage rises to the arrester action threshold, the arrester is activated, and the load current is transferred to the energy absorption branch. The arrester absorbs energy, the load current is reduced to zero, and the current conversion is completed.

[0064] However, the traditional DC conversion switch relies on the negative resistance characteristics of the SF6 arc and the passive self-induced oscillation of the inductor-capacitor oscillation circuit to make the arc current pass through the zero point, forcing the current to be disconnected, which is not environmentally friendly and causes waste of electric energy. Limited by the speed of recovery of the dielectric strength of SF6 gas after the arc, the inductor-capacitor resonant frequency in the DC conversion switch is low (generally <5kHz), requiring a larger capacitor inductance, resulting in the overall bulkiness and high cost of the switch, which in turn makes the switching method complicated. At the moment of current interruption, the electric energy stored in the inductor-capacitor oscillation circuit forms an overvoltage at the switch break. In order to release this part of the electric energy, the arrester group is connected in parallel with the circuit breaker branch and the inductor-capacitor oscillation circuit to release the electric energy generated by the overvoltage. At the same time, the arrester will also absorb the electric energy contained in the DC line, thereby increasing the cost of DC transmission and reducing the switching efficiency of the DC transmission system.

[0065] The present application embodiment provides a DC power transmission drive circuit. Figure 1 The DC power transmission drive circuit includes: a negative metal loop 100, an earth loop 200, a positive metal loop 300 and a first conduction unit K1, wherein a first end of the earth loop 200 is electrically connected to a first end of the negative metal loop 100, a second end of the earth loop 200 is electrically connected to a second end of the negative metal loop 100, a first end of the positive metal loop 300 is connected between a first end of the earth loop 200 and a first end of the negative metal loop 100, and a second end of the positive metal loop 300 is connected between a second end of the earth loop 200 and a negative metal loop The first conduction unit K1 is located between the first end of the earth return line 200 and the first end of the positive metal return line 300, and is used to control the connection and disconnection between the negative metal return line 100 and the earth return line 200 according to the voltage of the first end of the earth return line 200 and the voltage of the second end of the negative metal return line 100, wherein the positive metal return line 300 includes a second conduction unit K2, which is used to control the connection and disconnection between the negative metal return line 100 and the positive metal return line 300, and the first conduction unit K1 and the second conduction unit K2 are alternately turned on.

[0066] Exemplarily, the negative metal loop 100 may include a resistor Rn and an inductor Ln connected in series. The earth loop 200 may include a resistor Re and an inductor Le connected in series. Specifically, in this embodiment, the earth loop 200 includes a resistor Re1 and an inductor Le1 connected in series, and a resistor Re2 and an inductor Le2 connected in series. The positive metal loop 300 may include a resistor Rp and an inductor Lp connected in series.

[0067] Exemplarily, the first conduction unit K1 and the second conduction unit K2 are alternately turned on in two cases. In one case, the first conduction unit K1 is turned on, and the second conduction unit K2 is turned off, and the negative metal loop 100 forms a loop with the earth loop 200. In another case, the first conduction unit K1 is turned off, and the second conduction unit K2 is turned on, and the positive metal loop 300 forms a loop with the negative metal loop 100. Therefore, by alternately turning on the first conduction unit K1 and the second conduction unit K2, it is possible to switch between the positive metal loop 300 and the negative metal loop 100 forming a loop, and the negative metal loop 100 and the earth loop 200 forming a loop.

[0068] The DC power transmission drive circuit provided in the embodiment of the present application is electrically connected to the first end of the earth return line 200 through the first end of the negative metal return line 100, and the second end of the negative metal return line 100 is electrically connected to the second end of the earth return line 200, so that the negative metal return line 100 and the earth return line 200 form a loop. When the DC power transmission drive circuit needs to be repaired or a fault occurs, the current in the negative metal return line 100 can be derived through the earth return line 200 to facilitate the repair of the positive metal return line 300. By connecting the first end of the positive metal loop 300 between the first end of the earth loop 200 and the first end of the negative metal loop 100, and connecting the second end of the positive metal loop 300 between the second end of the earth loop 200 and the second end of the negative metal loop 100, the positive metal loop 300 can form a loop with the earth loop 200 and the negative metal loop 100 respectively, and the positive metal loop 300 and the negative metal loop 100 can be used to transmit electricity, and the DC power transmission circuit can be grounded at the same time, so as to ensure the normal operation of the DC power transmission circuit. Further, a first conduction unit K1 is set between the first end of the earth loop 200 and the first end of the positive metal loop 300, and a second conduction unit K2 is set in the positive metal loop 300, and the first conduction unit K1 can be used to automatically control the connection and disconnection between the negative metal loop 100 and the earth loop 200 according to the voltage of the first end of the earth loop 200 and the voltage of the second end of the negative metal loop 100. The switching of different conduction loops in the DC power transmission circuit can also be achieved by controlling the alternating conduction of the first conduction unit K1 and the second conduction unit K2. Thus, the difficulty of switching the operation mode of the DC power transmission circuit can be simplified through the automatic control function of the first conduction unit K1, and in the process of switching the operation mode, the waste of electric energy can be avoided, the cost of the operation of the DC power transmission circuit can be reduced, and the switching efficiency of the DC power transmission circuit can be improved.

[0069] In some embodiments, please refer to Figure 1When the voltage at the first end of the earth return line 200 is lower than the voltage at the second end of the negative metal return line 100, the first conduction unit K1 is disconnected. When the voltage at the first end of the positive metal return line 300 is lower than the voltage at the second end of the negative metal return line 100, the second conduction unit K2 is disconnected.

[0070] Exemplarily, when the voltage at the first end of the earth return line 200 is lower than the voltage at the second end of the negative metal return line 100, a loop current in the opposite direction to the original current in the loop is formed in the loop formed by the earth return line 200 and the negative metal return line 100, and the reverse direction of the loop current rapidly reduces the DC current in the loop formed by the earth return line 200 and the negative metal return line 100. When the DC current drops below the cutoff current of the first conduction unit K1, the first conduction unit K1 is automatically disconnected.

[0071] Exemplarily, when the voltage at the first end of the positive metal loop 300 is less than the voltage at the second end of the negative metal loop 100, a circulation current in the opposite direction to the original current in the loop is formed in the loop formed by the positive metal loop 300 and the negative metal loop 100. The circulation current in the opposite direction causes the DC current in the loop formed by the positive metal loop 300 and the negative metal loop 100 to decrease rapidly. When the DC current drops below the cutoff current of the second conduction unit K2, the second conduction unit K2 is disconnected.

[0072] The DC power transmission drive circuit provided in the embodiment of the present application can realize the circuit automatically switching from the loop formed by the earth loop 200 and the negative metal loop 100 to other operation modes by reducing the voltage of the first end of the earth loop 200 so that the voltage of the first end of the earth loop 200 is less than the voltage of the second end of the negative metal loop 100, thereby disconnecting the first conduction unit K1, and the switching process will not cause loss of electric energy, thereby improving the switching efficiency of the circuit. By reducing the voltage of the first end of the positive metal loop 300 so that the voltage of the first end of the positive metal loop 300 is less than the voltage of the second end of the negative metal loop 100, thereby disconnecting the second conduction unit K2, the circuit can automatically switch from the loop formed by the positive metal loop 300 and the negative metal loop 100 to other operation modes, and the switching process will not cause loss of electric energy, thereby improving the switching efficiency of the circuit.

[0073] In some embodiments, please refer to Figure 1The DC power transmission drive circuit further includes: a first rectifier 400, wherein the output end of the first rectifier 400 is electrically connected to the first end of the first conductive unit K1 away from the earth return line 200, and the input end of the first rectifier 400 is electrically connected to the first end of the negative metal return line 100, and the first rectifier 400 is used to convert the input AC voltage into a DC voltage output. A second rectifier 500, wherein the input end of the second rectifier 500 is electrically connected to the first end of the first conductive unit K1 away from the earth return line 200 and the output end of the first rectifier 400, and the output end of the second rectifier 500 is electrically connected to an end of the second conductive unit K2 away from the earth return line 200. A first inverter 600, wherein the input end of the first inverter 600 is electrically connected to the second end of the earth return line 200, and the output end of the first inverter 600 is electrically connected to the second end of the negative metal return line 100. The second inverter 700 has an input end electrically connected to the second end of the positive metal return line 300 , and an output end of the second inverter 700 is electrically connected to the second end of the earth return line 200 and the input end of the first inverter 600 .

[0074] Exemplarily, the first rectifier 400 and the second rectifier 500 can convert the input AC power into DC power output. Specifically, in this embodiment, the first rectifier 400 is a negative rectifier, the second rectifier 500 is a positive rectifier, and the first rectifier 400 and the second rectifier 500 can both be diodes.

[0075] Exemplarily, the first inverter 600 and the second inverter 700 can convert the input direct current into alternating current for output. Specifically, in this embodiment, the first inverter 600 is a negative pole inverter, the second inverter 700 is a positive pole inverter, and the first inverter 600 and the second inverter 700 can both be diodes.

[0076] The DC power transmission drive circuit provided in the embodiment of the present application can realize mutual conversion between DC power and AC power by setting a first rectifier 400 and a second rectifier 500, as well as a first inverter 600 and a second inverter 700, so as to ensure the output of different forms of electrical energy and improve the conversion efficiency of the circuit.

[0077] In some embodiments, please refer to Figure 1 The DC power transmission drive circuit further includes: a third conduction unit K31, one end of the third conduction unit K31 is electrically connected to the input end of the second rectifier 500, and the other end of the third conduction unit K31 is electrically connected to the first end of the first conduction unit K1 away from the earth return line 200 and the output end of the first rectifier 400. When the voltage value of the first end of the positive metal return line 300 is less than the voltage value of the second end of the negative metal return line 100, the third conduction unit K31 is disconnected.

[0078] Exemplarily, when the voltage at the first end of the positive metal loop 300 is less than the voltage at the second end of the negative metal loop 100, a circulation current in the opposite direction to the original current in the loop is formed in the loop formed by the positive metal loop 300 and the negative metal loop 100. The circulation current in the opposite direction causes the DC current in the loop formed by the positive metal loop 300 and the negative metal loop 100 to decrease rapidly. When the DC current drops below the cutoff current of the third conduction unit K31, the third conduction unit K31 is disconnected.

[0079] The DC power transmission drive circuit provided in the embodiment of the present application reduces the voltage at the first end of the positive metal loop 300 so that the voltage at the first end of the positive metal loop 300 is less than the voltage at the second end of the negative metal loop 100, thereby disconnecting the third conduction unit K31. This can achieve the circuit automatically switching from a loop formed by the positive metal loop 300 and the negative metal loop 100 to other operating modes, and the switching process will not cause loss of electric energy, thereby improving the switching efficiency of the circuit.

[0080] In some embodiments, please refer to Figure 1 , further comprising: a fourth conduction unit K32, one end of the fourth conduction unit K32 is electrically connected to the output end of the second inverter 700, and the other end of the fourth conduction unit K32 is electrically connected to the second end of the earth return line 200 and the input end of the first inverter 600. When the voltage value of the first end of the positive metal return line 300 is less than the voltage value of the second end of the negative metal return line 100, the fourth conduction unit K32 is disconnected.

[0081] Exemplarily, when the voltage at the first end of the positive metal loop 300 is less than the voltage at the second end of the negative metal loop 100, a loop current in the opposite direction is formed in the loop formed by the positive metal loop 300 and the negative metal loop 100. The loop current in the opposite direction causes the DC current in the loop formed by the positive metal loop 300 and the negative metal loop 100 to decrease rapidly. When the DC current drops below the cutoff current of the fourth conduction unit K32, the fourth conduction unit K32 is disconnected.

[0082] The DC power transmission drive circuit provided in the embodiment of the present application reduces the voltage at the first end of the positive metal loop 300 so that the voltage at the first end of the positive metal loop 300 is less than the voltage at the second end of the negative metal loop 100, thereby disconnecting the fourth conduction unit K32. This can achieve the circuit automatically switching from a loop formed by the positive metal loop 300 and the negative metal loop 100 to other operating modes, and the switching process will not cause loss of electric energy, thereby improving the switching efficiency of the circuit.

[0083] In some embodiments, please refer to Figure 1The first conduction unit K1, the second conduction unit K2, the third conduction unit K31 and the fourth conduction unit K32 are all vacuum switches.

[0084] It should be noted that the vacuum switch can be automatically disconnected when the voltage value in the circuit drops to a preset voltage value, and thus the DC power transmission drive circuit can be automatically disconnected by controlling the automatic disconnection of the first conduction unit K1, the second conduction unit K2, the third conduction unit K31 and the fourth conduction unit K32 when the circuit needs to be switched, thereby automatically controlling the current flow direction of the DC power transmission drive circuit. At the same time, the vacuum switch can use vacuum as an insulating and arc-extinguishing medium, and can quickly extinguish the arc when the circuit is disconnected, thereby safely cutting off the current.

[0085] The DC power transmission drive circuit provided in the embodiment of the present application can automatically control the current flow direction of the DC power transmission drive circuit by setting the first conduction unit K1, the second conduction unit K2, the third conduction unit K31 and the fourth conduction unit K32 as vacuum switches, and can quickly extinguish the arc when the circuit is disconnected, thereby safely cutting off the current and improving the reliability and switching rate of the DC drive circuit.

[0086] In some embodiments, please refer to Figure 1 The positive metal loop 300 further includes: a fifth conduction unit K51, a first end of the fifth conduction unit K51 is electrically connected to the second conduction unit K2, and a second end of the fifth conduction unit K51 is electrically connected to the second end of the earth loop 200. A sixth conduction unit K52 is located between the fifth conduction unit K51 and the second end of the earth loop 200.

[0087] Exemplarily, the fifth conduction unit K51 and the sixth conduction unit K52 can be isolating switches. When the DC drive circuit is switched to form a loop between the positive metal return line 300 and the earth return line 200, and when the positive metal return line 300 and the negative metal return line 100 form a loop, the fifth conduction unit K51 and the sixth conduction unit K52 can be put into a conduction state to connect the positive metal return line 300 to the circuit.

[0088] The DC power transmission drive circuit provided in the embodiment of the present application, by setting the fifth conduction unit K51 and the sixth conduction unit K52, can make the fifth conduction unit K51 and the sixth conduction unit K52 in a conduction state when the DC drive circuit is switched to form a loop with the positive metal return line 300 and the earth return line 200, and when the positive metal return line 300 and the negative metal return line 100 form a loop, so that the positive metal return line 300 is connected to the circuit, further control the connection state of the positive metal return line 300 in the circuit, and improve the reliability of the DC power transmission drive circuit.

[0089] Please refer to Figure 1 The DC power transmission drive circuit provided in the embodiment of the present application may further include a neutral bus 800, a switch K33, a switch K34, a switch K41, and a switch K42. The neutral bus 800 connects the positive metal return line 300 and the negative metal return line 100. The switch K33 is located between the first rectifier 400 and the first conduction unit K1. The switch K34 is located between the first inverter 600 and the earth return line 200. The switch K41 and the switch K42 are located between the neutral bus 800 and the ground. The switch K61 is located between the first end of the negative metal return line 100 and the first end of the positive metal return line 300. The switch K62 and the switch K61 are located between the second end of the negative metal return line 100 and the second end of the positive metal return line 300.

[0090] The present application provides a control method for a DC power transmission drive circuit. Figure 2 The method is applied to the DC power transmission drive circuit of any one of the above embodiments, and the control method of the DC power transmission drive circuit includes:

[0091] S11: Close the first conduction unit.

[0092] S12: Turn off the second conduction unit.

[0093] S13: Obtaining a first control instruction of the DC power transmission drive circuit, the first control instruction is used to control the earth return line to be electrically connected to the negative metal return line, and to control the positive metal return line to be disconnected from the negative metal return line.

[0094] S14: According to the first control instruction, the voltage value of the first end of the positive metal loop is controlled to be smaller than the voltage value of the second end of the negative metal loop, so that the third conduction unit and the fourth conduction unit are disconnected, so that the earth loop and the negative metal loop form a loop.

[0095] It should be noted that Figure 3 The circuit diagram is a conduction mode of the positive metal loop 300 and the negative metal loop 100 of the DC power transmission drive circuit. Figure 4 The circuit diagram of the DC power transmission driving circuit is switched to the conduction mode of the negative metal loop 100 and the earth loop 200. The current change curve of the DC power transmission driving circuit is switched from the conduction mode of the positive metal loop 300 and the negative metal loop 100 to the conduction mode of the negative metal loop 100 and the earth loop 200. Figure 5When the loop of the earth return line 200 and the negative metal return line 100 needs to be switched, the voltage at the first end of the earth return line 200 can be reduced, so that a loop current opposite to the original current in the loop is formed in the loop formed by the earth return line 200 and the negative metal return line 100. The reverse direction of the loop current causes the DC current in the loop formed by the earth return line 200 and the negative metal return line 100 to decrease rapidly, as shown in FIG. Figure 5 As shown. Then, the voltage at the first end of the earth return line 200 is made less than the voltage at the second end of the negative metal return line 100, so that the first conduction unit K1 is disconnected, so that the current flow in the DC transmission circuit is switched from the positive metal return line 300 to the negative metal return line 100. In the case where the first conduction unit K1 is disconnected, it is necessary to restore the current reference value of the sending-end converter station of the LCC (Line Commutated Converter) to the normal operating value after the first preset time until the DC current returns to the original value. Specifically, the first preset time can be set according to the actual situation of the first conduction unit K1. More specifically, in this embodiment, the first preset time ranges from 10s to 20s. For example, the first preset time can be 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s or 20s. Restoring the current reference value of the sending-end converter station of the line converter to a normal operating value after the first preset time can ensure that the first conduction unit K1 has sufficient recovery time to avoid current or voltage damage to the first conduction unit K1.

[0096] The control method of the DC power transmission drive circuit provided in the embodiment of the present application closes the first conduction unit K1 so that the earth return line 200 is connected to the circuit, disconnects the second conduction unit K2 so that the positive metal return line 300 is disconnected, and further obtains a first control instruction of the DC power transmission drive circuit. According to the first control instruction, the voltage value of the first end of the positive metal return line 300 is made less than the voltage value of the second end of the negative metal return line 100, and then the third conduction unit K31 and the fourth conduction unit K32 are disconnected, so that the earth return line 200 and the negative metal return line 100 form a loop, thereby realizing the DC power transmission drive circuit from the mode in which the positive metal return line 300 is connected to the negative metal return line 100 to the mode in which the negative metal return line 100 is connected to the earth return line 200, and realizing the rapid switching of the DC power transmission drive circuit line without losing electric energy, thereby improving the driving efficiency of the DC power transmission drive circuit.

[0097] In some embodiments, see Figure 6 , the control method of the DC transmission drive circuit also includes:

[0098] S21: Close the second conduction unit.

[0099] S22: Obtain a second control instruction of the DC power transmission drive circuit, the second control instruction is used to control the electrical connection between the positive metal return line and the negative metal return line, and to control the disconnection between the negative metal return line and the earth return line.

[0100] S23: According to the second control instruction, the voltage value of the first end of the earth return line is controlled to be smaller than the voltage value of the second end of the negative metal return line, so that the first conduction unit is disconnected, so that the positive metal return line and the negative metal return line form a loop.

[0101] It should be noted that Figure 7 The circuit diagram is a mode in which the negative metal return line 100 of the DC power transmission driving circuit is connected to the earth return line 200. Figure 8 The circuit diagram of the DC power transmission drive circuit in the conduction mode of the positive metal loop 300 and the negative metal loop 100 is shown in FIG. The current change curve of the DC power transmission drive circuit when the conduction mode of the negative metal loop 100 and the earth loop 200 is switched to the conduction mode of the positive metal loop 300 and the negative metal loop 100 is shown in FIG. Fig. 9 It should be noted that, when it is necessary to switch the loop of the positive metal loop 300 and the negative metal loop 100, the voltage of the first end of the positive metal loop 300 can be reduced, so that the voltage of the first end of the positive metal loop 300 is less than the voltage of the second end of the negative metal loop 100, thereby forming a loop in the loop formed by the positive metal loop 300 and the negative metal loop 100 in the opposite direction to the original current in the loop. The reverse direction of the loop causes the direct current in the loop formed by the positive metal loop 300 and the negative metal loop 100 to decrease rapidly so that the second conduction unit K2 is disconnected until the current becomes 0 amperes, as shown in FIG. Fig. 9 As shown in . In the case where the second conduction unit K2 is disconnected, it is necessary to restore the current reference value of the sending-end converter station of the LCC to the normal operating value after the second preset time, until the DC current returns to the original value, so that the circuit forms a loop with the positive metal return line 300 and the negative metal return line 100 and switches to other operating modes. Specifically, the second preset time can be set according to the actual situation of the second conduction unit K2. More specifically, in this embodiment, the second preset time ranges from 10s to 20s. For example, the second preset time can be 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s or 20s. Restoring the current reference value of the sending-end converter station of the line converter to the normal operating value after the second preset time can ensure that the second conduction unit K2 has sufficient recovery time to avoid current or voltage from causing damage to the second conduction unit K2.

[0102] The control method of the DC power transmission drive circuit provided in the embodiment of the present application closes the second conduction unit K2 so that the positive metal return line 300 is connected to the circuit, obtains the second control instruction of the DC power transmission drive circuit, and according to the second control instruction, makes the voltage value of the first end of the earth return line 200 less than the voltage value of the second end of the negative metal return line 100, thereby disconnecting the first conduction unit K1, so that the positive metal return line 300 and the negative metal return line 100 form a loop, thereby realizing the DC power transmission drive circuit from the mode in which the negative metal return line 100 is connected to the earth return line 200 to the mode in which the positive metal return line 300 is connected to the negative metal return line 100, and realizing the rapid switching of the DC power transmission drive circuit line without losing electric energy, thereby improving the driving efficiency of the DC power transmission drive circuit.

[0103] In some embodiments, see Fig.10 , the control method of the DC transmission drive circuit also includes:

[0104] S31: closing the third conduction unit and the fourth conduction unit.

[0105] S32: Close the first conduction unit.

[0106] S33: Obtain a third control instruction of the DC transmission drive circuit, the third control instruction is used to control the voltage value of the first end of the positive metal loop to be less than the voltage value of the second end of the negative metal loop, so that the second conduction unit is disconnected, so that the positive metal loop and the negative metal loop form a loop.

[0107] It should be noted that Fig.11 The circuit diagram is a mode in which the positive metal loop line 300 and the negative metal loop line 100 of the DC power transmission driving circuit are connected. Fig.12 The circuit diagram is a circuit diagram of a DC power transmission drive circuit in which the positive metal loop 300 and the negative metal loop 100 form a loop mode through a second rectifier 500 and a second inverter 700. The mode in which the positive metal loop 300 and the negative metal loop 100 of the DC power transmission drive circuit are turned on is switched to a current in which the positive metal loop 300 and the negative metal loop 100 form a loop mode through a second rectifier 500 and a second inverter 700. Fig.13 When the loop of the positive metal loop 300 and the negative metal loop 100 needs to be switched, the voltage of the first end of the positive metal loop 300 can be reduced so that the voltage of the first end of the positive metal loop 300 is less than the voltage of the second end of the negative metal loop 100, thereby forming a loop in the loop formed by the positive metal loop 300 and the negative metal loop 100 in the opposite direction to the original current in the loop. The reverse direction of the loop causes the direct current in the loop formed by the positive metal loop 300 and the negative metal loop 100 to decrease rapidly, and the direct current drops to zero ampere, as shown in FIG. Fig.13As shown in . When the DC current drops below the cut-off current of the third conduction unit K31, the third conduction unit K31 is disconnected. When the third conduction unit K31 is disconnected, it is necessary to restore the current reference value of the sending-end converter station of the LCC to the normal operating value after the third preset time, until the DC current returns to the original value, so that the circuit is switched from the loop formed by the positive metal loop 300 and the negative metal loop 100 to other operating modes. Specifically, the third conduction unit K31 connects the positive metal loop 300 and the negative metal loop 100 through the loop formed by the second rectifier 500 and the second inverter 700.

[0108] Exemplarily, the third preset time can be set according to the actual situation of the third conduction unit K31. More specifically, in this embodiment, the third preset time ranges from 10s to 20s. For example, the third preset time can be 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s or 20s. After the third preset time, restoring the current reference value of the sending-end converter station of the line converter to the normal operating value can ensure that the third conduction unit K31 has sufficient recovery time to avoid current or voltage damage to the third conduction unit K31.

[0109] It should be noted that, when it is necessary to switch the loop of the positive metal loop 300 and the negative metal loop 100, the voltage of the first end of the positive metal loop 300 can be reduced, so that the voltage of the first end of the positive metal loop 300 is less than the voltage of the second end of the negative metal loop 100, thereby forming a loop in the loop formed by the positive metal loop 300 and the negative metal loop 100 with a direction opposite to the original current in the loop. The reverse direction of the loop causes the DC current in the loop formed by the positive metal loop 300 and the negative metal loop 100 to decrease rapidly, and the DC current drops to zero ampere, such as Fig.13 As shown in . When the DC current drops below the cut-off current of the fourth conduction unit K32, the fourth conduction unit K32 is disconnected. And it is necessary to restore the current reference value of the sending-end converter station of the LCC to the normal operating value after the fourth preset time, until the DC current returns to the original value, so that the circuit is switched from the loop formed by the positive metal loop 300 and the negative metal loop 100 to other operating modes. Specifically, the fourth conduction unit K32 connects the positive metal loop 300 and the negative metal loop 100 through the loop formed by the second rectifier 500 and the second inverter 700, and the third conduction unit K31 is connected in series with the fourth conduction unit K32.

[0110] Exemplarily, the fourth preset time can be set according to the actual situation of the fourth conduction unit K32. More specifically, in this embodiment, the fourth preset time ranges from 10s to 20s. For example, the fourth preset time can be 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s or 20s. After the fourth preset time, restoring the current reference value of the sending-end converter station of the line converter to the normal operating value can ensure that the fourth conduction unit K32 has sufficient recovery time to avoid current or voltage damage to the fourth conduction unit K32.

[0111] The control method of the DC power transmission drive circuit provided in the embodiment of the present application closes the third conduction unit K31 and the fourth conduction unit K32, so that the positive metal loop 300 is connected to the circuit, and the third control instruction of the DC power transmission drive circuit is obtained. According to the third control instruction, the voltage value of the first end of the positive metal loop 300 is made less than the voltage value of the second end of the negative metal loop 100, and then the second conduction unit K2 is disconnected, so that the positive metal loop 300 and the negative metal loop 100 form a loop through the second rectifier 500 and the second inverter 700, thereby realizing the DC power transmission drive circuit from the mode in which the positive metal loop 300 and the negative metal loop 100 are connected to the mode in which the positive metal loop 300 and the negative metal loop 100 form a loop through the second rectifier 500 and the second inverter 700, and realizing the fast switching of the DC power transmission drive circuit without losing electric energy, thereby improving the driving efficiency of the DC power transmission drive circuit.

[0112] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features of the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A DC power transmission drive circuit, characterized in that: include: Negative metal return line; an earth return line, wherein a first end of the earth return line is electrically connected to a first end of the negative metal return line, and a second end of the earth return line is electrically connected to a second end of the negative metal return line; A positive metal loop line, wherein the first end of the positive metal loop line is connected between the first end of the earth loop line and the first end of the negative metal loop line, and the second end of the positive metal loop line is connected between the second end of the earth loop line and the second end of the negative metal loop line; A first conduction unit, located between the first end of the earth return line and the first end of the positive metal return line, is used to control the connection between the negative metal return line and the earth return line according to the voltage of the first end of the earth return line and the voltage of the second end of the negative metal return line; Wherein, the positive metal loop line includes a second conduction unit for controlling the connection and disconnection between the negative metal loop line and the positive metal loop line; The first conducting unit and the second conducting unit are alternately turned on.

2. The DC power transmission drive circuit according to claim 1, characterized in that: When the voltage at the first end of the earth return line is lower than the voltage at the second end of the negative metal return line, the first conduction unit is disconnected; When the voltage at the first end of the positive metal loop is lower than the voltage at the second end of the negative metal loop, the second conduction unit is turned off.

3. The DC power transmission drive circuit according to claim 1, characterized in that: Also includes: A first rectifier, wherein an output end of the first rectifier is electrically connected to a first end of the first conductive unit away from the earth return line, an input end of the first rectifier is electrically connected to a first end of the negative metal return line, and the first rectifier is used to convert an input AC voltage into a DC voltage output; A second rectifier, wherein an input end of the second rectifier is electrically connected to a first end of the first conductive unit away from the earth return line and an output end of the first rectifier, and an output end of the second rectifier is electrically connected to an end of the second conductive unit away from the earth return line; a first inverter, wherein an input end of the first inverter is electrically connected to a second end of the earth return line, and an output end of the first inverter is electrically connected to a second end of the negative metal return line; A second inverter, wherein the input end of the second inverter is electrically connected to the second end of the positive metal return line, and the output end of the second inverter is electrically connected to the second end of the earth return line and the input end of the first inverter.

4. The DC power transmission drive circuit according to claim 3, characterized in that: Also includes: a third conducting unit, one end of the third conducting unit being electrically connected to the input end of the second rectifier, and the other end of the third conducting unit being electrically connected to the first end of the first conducting unit away from the earth return line and the output end of the first rectifier; When the voltage value of the first end of the positive metal loop is less than the voltage value of the second end of the negative metal loop, the third conduction unit is turned off.

5. The DC power transmission drive circuit according to claim 3, characterized in that: Also includes: a fourth conduction unit, one end of the fourth conduction unit being electrically connected to the output end of the second inverter, and the other end of the fourth conduction unit being electrically connected to the second end of the earth return line and the input end of the first inverter; When the voltage value of the first end of the positive metal loop is less than the voltage value of the second end of the negative metal loop, the fourth conduction unit is turned off.

6. The DC power transmission drive circuit according to claim 4 or 5, characterized in that: The first conduction unit, the second conduction unit, the third conduction unit and the fourth conduction unit are all vacuum switches.

7. The DC power transmission drive circuit according to claim 1, characterized in that: The positive metal return line also includes: a fifth conducting unit, wherein a first end of the fifth conducting unit is electrically connected to the second conducting unit, and a second end of the fifth conducting unit is electrically connected to a second end of the earth return line; A sixth conducting unit is located between the fifth conducting unit and the second end of the earth return line.

8. A control method for a DC transmission drive circuit, characterized in that: The method applied to the DC power transmission drive circuit according to any one of claims 1 to 6 comprises: closing the first conduction unit; Disconnecting the second conduction unit; Acquire a first control instruction of the DC power transmission drive circuit, wherein the first control instruction is used to control the earth return line to be electrically connected to the negative metal return line, and to control the positive metal return line to be disconnected from the negative metal return line; According to the first control instruction, the voltage value of the first end of the positive metal loop is controlled to be smaller than the voltage value of the second end of the negative metal loop, so that the third conduction unit and the fourth conduction unit are disconnected, so that the earth loop and the negative metal loop form a loop.

9. The control method of the DC power transmission drive circuit according to claim 8, characterized in that: Also includes: closing the second conducting unit; Acquire a second control instruction of the DC power transmission drive circuit, wherein the second control instruction is used to control the electrical connection between the positive metal return line and the negative metal return line, and to control the disconnection between the negative metal return line and the earth return line; According to the second control instruction, the voltage value of the first end of the earth return line is controlled to be smaller than the voltage value of the second end of the negative metal return line, so that the first conduction unit is disconnected, so that the positive metal return line and the negative metal return line form a loop.

10. The control method of the DC power transmission drive circuit according to claim 8, characterized in that: Also includes: closing the third conducting unit and the fourth conducting unit; closing the first conducting unit; A third control instruction of the DC power transmission drive circuit is obtained, wherein the third control instruction is used to control the voltage value of the first end of the positive metal loop to be less than the voltage value of the second end of the negative metal loop, so that the second conduction unit is disconnected, so that the positive metal loop and the negative metal loop form a loop.

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