A control method for a multi-port DC converter switch based on a controllable negative pressure source

Abstract

The present invention discloses a control method for a multi-port DC conversion switch based on a controllable negative pressure source, which belongs to the field of power system control technology. Before current conversion, the flow vacuum switch and the commutation vacuum switch are closed, and other components are turned off. When the current of the main branch to be interrupted is positive, the flow vacuum switch is opened, and the thyristors VT1, VT4 and the forward conduction component are triggered to transfer the current to the commutation branch; the commutation vacuum switch is opened, and the controllable square wave voltage source is adjusted using the same frequency / divided frequency control method to transfer the current to the LC branch, and finally the MOV is activated to transfer the current to other main branches. When the current is reverse, VT2, VT3 and the reverse conduction component are triggered, and the subsequent steps are similar. The same frequency / divided frequency control method is achieved by controlling the IGBT switching frequency, and the method is different when there are one or more triggering branches. This control method is simple, can realize rapid transfer of current in different directions, and the control methods of the sending end and the receiving end are consistent.

Description

Technical Field

[0001] The present invention relates to the technical field of power system control, and in particular to a control method for a multi-port DC conversion switch based on a controllable negative pressure source. Background Art

[0002] With the rapid development of high-voltage direct current (HVDC) transmission technology, power systems are placing higher demands on the flexibility, reliability, and efficiency of switching operating modes. Traditional two-port DC transfer switches (such as MRTBs and ERTBs) rely on the coordinated operation of mechanical switches and LC oscillating circuits to achieve current transfer, but they have the following prominent problems:

[0003] Limitations of control strategies: Traditional control methods rely on the negative resistance characteristics of the arc to excite LC oscillations. The current transfer speed is slow, and the oscillation frequency cannot be actively adjusted, making it difficult to adapt to high-frequency requirements.

[0004] Lack of multi-port coordinated control: Existing multi-port switching requires the sequential operation of multiple independent switches and lacks a unified control strategy, which can easily lead to control timing mismatch and cause overvoltage or current shock.

[0005] Insufficient dynamic response capability: The resonant frequency of the traditional LC circuit is fixed and cannot be dynamically adjusted according to the system operating conditions, resulting in low energy absorption efficiency and excessive burden on the lightning arrester.

[0006] Low level of intelligence: Lack of real-time monitoring and adaptive control functions makes it difficult to meet the development needs of intelligent and digital modern power grids.

[0007] Furthermore, with the advancement of the "dual carbon" goals, the trend toward banning SF6 gas is becoming increasingly pronounced, necessitating an urgent need for environmentally friendly arc-extinguishing alternatives. While existing vacuum switches are environmentally friendly, their control strategies for high-frequency current transfer and complex operating conditions remain immature, limiting their widespread application in DC converters. Summary of the Invention

[0008] The purpose of the present invention is to provide a control method for a multi-port DC conversion switch based on a controllable negative pressure source, which realizes rapid current transfer and efficient energy management by dynamically adjusting the output frequency of the square wave voltage source.

[0009] To achieve the above objectives, the present invention provides a control method for a multi-port DC transfer switch based on a controllable negative pressure source. When the current in the main branch to be interrupted is a positive current (flowing from the busbar to the main branch), the control method for the multi-port DC transfer switch comprises the following steps:

[0010] S1. Before switching, the through-current vacuum switch and the commutation vacuum switch are both in the closed state, and the controllable square wave voltage source, the controllable negative pressure source, the controllable conduction switch, etc. are all in the off state;

[0011] S2: When current conversion is required, the vacuum switch is opened and the thyristor VT1 and thyristor VT4 in the controllable negative pressure source are triggered, so that the negative pressure source is connected to the commutation branch. At the same time, the forward thyristor assembly or the forward vacuum trigger gap connected to the main branch to be interrupted is triggered, forcing the current to be transferred to the commutation branch, and the vacuum switch is extinguished;

[0012] S3, open-gate commutation vacuum switch, controls the IGBT near the bus terminal in the controllable square wave voltage source through the same frequency / divided frequency control method f , so that the square wave voltage source output voltage U SWO The frequency of and the resonant frequency of the LC branch meet the same frequency / multiple frequency relationship, the excitation current is further transferred from the commutation vacuum switch to the LC branch, and the commutation vacuum switch is extinguished;

[0013] S4, the load current charges the capacitor of the LC branch, and the voltage across the MOV branch gradually rises to the MOV operating voltage;

[0014] S5, MOV operates, creates transient voltage, absorbs energy, and transfers load current to other main branches.

[0015] Preferably, when the current of the main branch to be disconnected is a reverse current (flowing from the main branch to the bus), the steps of the control method of the multi-port DC transfer switch are:

[0016] S1. Before switching, the through-current vacuum switch and the commutation vacuum switch are both in the closed state, and the controllable square wave voltage source, the controllable negative pressure source, the controllable conduction switch, etc. are all in the off state;

[0017] S2: When current conversion is required, the vacuum switch is opened and the thyristor VT2 and thyristor VT3 in the controllable negative pressure source are triggered, so that the negative pressure source is connected to the commutation branch. At the same time, the reverse thyristor assembly or reverse vacuum trigger gap connected to the main branch to be interrupted is triggered, forcing the current to be transferred to the commutation branch, and the vacuum switch is extinguished;

[0018] S3, open gate commutation vacuum switch, controls the far bus terminal IGBT in the controllable square wave voltage source through the same frequency / divided frequency control method b , so that the square wave voltage source output voltage U SWO The frequency of and the resonant frequency of the LC branch meet the same frequency / multiple frequency relationship, the excitation current is further transferred from the commutation vacuum switch to the LC branch, and the commutation vacuum switch is extinguished;

[0019] S4, the load current charges the capacitor of the LC branch, and the voltage across the MOV branch gradually rises to the MOV operating voltage;

[0020] S5, MOV operates, creates transient voltage, absorbs energy, and transfers load current to other main branches.

[0021] Preferably, the controllable square wave voltage source is controlled by turning on and off the IGBT in the controllable square wave generator. U SWO The frequency of and the resonant frequency of the LC branch satisfy the same frequency / multiple frequency relationship, that is, (N=1,2,3…).

[0022] Preferably, when the trigger branch consists of one switch branch, the switching frequency of the IGBT itself is used to realize ,Right now , N can be any positive integer. The specific implementation method is: first turn off IGBT1 so that U swo Output high level and keep off state for 2N-1 capacitor voltage half-waves, wait for the capacitor voltage to reach the Nth positive peak, turn on IGBT1 to make U swo Output low level and keep the conduction state for 1 half wave, wait for the capacitor voltage to drop from the forward voltage peak to the reverse voltage peak, and then turn off IGBT1 again. U swo The output is high, and the IGBT1 cycle enters the process of turning off 2N-1 half-waves and turning on 1 half-wave. The positive peak value of the capacitor voltage refers to when the capacitor terminal connected to the positive electrode of the square wave voltage source is positive; the reverse peak value of the capacitor voltage refers to when the capacitor terminal connected to the positive electrode of the square wave voltage source is negative.

[0023] Preferably, when the trigger branch is composed of n (n=2, 3, 4...) parallel switch branches, the cross triggering of multiple parallel IGBTs can be used to achieve , and the switching frequency of a single IGBT and the LC resonant frequency meet The specific implementation method is: First, turn off all IGBTs so that U swo Output high level, wait for the capacitor voltage to reach the positive peak, turn on the first branch IGBT1 so that U swo Output low level, keep the conduction state for one capacitor voltage half wave, wait for the capacitor voltage to drop from the forward voltage peak to the reverse voltage peak, turn off IGBT1 so that U swo Output high level, wait for the capacitor voltage to reach the positive peak, turn on the second branch IGBT2 to make U swo Output low level, keep the conduction state for 1 half wave, wait for the capacitor voltage to drop from the forward voltage peak to the reverse voltage peak, turn off IGBT2 so that U swoOutput high level. During the IGBT control cycle, each IGBT is triggered to conduct for half a cycle in sequence to achieve , and the switching frequency of a single IGBT and the LC resonant frequency meet The forward peak value of the capacitor voltage refers to when the capacitor terminal connected to the positive electrode of the square wave voltage source is the positive electrode; the reverse peak value of the capacitor voltage refers to when the capacitor terminal connected to the positive electrode of the square wave voltage source is the negative electrode.

[0024] Therefore, the present invention adopts a control method of a multi-port DC converter switch based on a controllable negative pressure source using the above structure, which has the following beneficial effects:

[0025] The present invention has the advantage of a simple control method. By selectively controlling the controllable conduction switch, the controllable negative voltage source, and the controllable square wave voltage source according to the current direction of the main branch to be disconnected, the main branch current in any direction can be transferred to the commutation branch and ultimately to other main branches. The control method is consistent for multi-port DC converter switches installed at the sending or receiving end.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a control flow chart of a multi-port DC conversion switch based on a controllable negative pressure source according to an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of the implementation principle of the control method of a controllable square wave voltage source according to an embodiment of the present invention (n=1, N=2);

[0029] Figure 3 Schematic diagram of the implementation principle of the controllable square wave voltage source control method according to an embodiment of the present invention (n=2, N=1);

[0030] Figure 4 This is a schematic diagram of the current when a conventional DC system operates in a negative-earth return mode before the multi-port DC conversion switch based on a controllable negative pressure source according to an embodiment of the present invention is actuated;

[0031] Figure 5 This is a schematic diagram of an embodiment of the present invention showing a multi-port DC conversion switch operating in parallel with an earth return line and a positive metal return line based on a controllable negative pressure source;

[0032] Figure 6 A schematic diagram of the earth return current flowing through the sending-end commutation branch during the operation of a multi-port DC conversion switch based on a controllable negative pressure source according to an embodiment of the present invention;

[0033] Figure 7Schematic diagram of the gradual transfer of earth return current to the positive metal return line during the operation of the multi-port DC conversion switch based on the controllable negative pressure source according to an embodiment of the present invention;

[0034] Figure 8 In the process of the multi-port DC conversion switch operation based on the controllable negative pressure source in the embodiment of the present invention, the square wave resonant DC circuit breaker establishes a transient voltage U tr Schematic diagram of the process;

[0035] Figure 9 A schematic diagram showing that the earth return line current is completely transferred to the positive metal return line after the multi-port DC conversion switch based on the controllable negative pressure source according to an embodiment of the present invention is actuated;

[0036] Figure 10 This is a schematic diagram of an intermediate state during the switching process when a multi-port DC conversion switch based on a controllable negative pressure source switches from a negative electrode-earth return line operation mode to a negative electrode-metal return line operation mode in an embodiment of the present invention;

[0037] Figure 11 This is a schematic diagram of an intermediate state of a square wave resonant DC circuit breaker when it is disconnected when the negative pole-earth return line operation mode is switched to the negative pole-metal return line operation mode in a multi-port DC conversion switch based on a controllable negative pressure source in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0039] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0040] Example

[0041] like Figure 1The present invention provides a control method for a multi-port DC transfer switch based on a controllable negative pressure source. Assuming that the load current of the main branch x needs to be transferred to the main branch y through the multi-port DC transfer switch, the steps of the method are as follows:

[0042] S1, before switching, the vacuum switch K x , the commutation vacuum switch VCB is in the closed state, the controllable square wave voltage source, the controllable negative pressure source, the controllable conduction switch, etc. are all in the off state;

[0043] S2. When current needs to be converted, close the vacuum switch K y , open-circuit vacuum switch K x , at this time, the main branch x and the main branch y are running in parallel;

[0044] S3, determine the current direction of the main branch x, if it is a positive current (current from the busbar to the main branch x), then trigger the thyristors VT1 and VT4 to cut the negative voltage source into the commutation branch, triggering the IGBT f1 The temporary current branch is forward-conducted, and the forward thyristor assembly connected to the main branch x is triggered, forcing the current to transfer to the commutation branch, and the current vacuum switch extinguishes the arc; if it is a reverse current (the current is from the main branch x to the bus), the thyristors VT2 and VT3 are triggered to cut the negative voltage source into the commutation branch, triggering the IGBT b1 The temporary current-carrying branch is reversely conducted, and the reverse thyristor assembly connected to the main branch x is triggered at the same time, forcing the current to transfer to the commutation branch, and the current-carrying vacuum switch extinguishes the arc;

[0045] S4, open the commutation vacuum switch VCB, and control the IGBT through the same frequency / divided frequency control method fi or IGBT bi The opening and closing of the controllable square wave voltage source causes the output of a square wave voltage with the same frequency or a multiple of the LC resonant frequency, and the excitation current is further transferred from the commutation vacuum switch to the LC branch, and the commutation vacuum switch extinguishes the arc;

[0046] S5. The load current is transferred to the LC branch to charge capacitor C1. The voltage across the MOV branch gradually rises. When the voltage across the MOV reaches the action voltage of MOV1, MOV1 operates to establish a transient voltage, absorbs energy, and the load current begins to transfer to the main branch y.

[0047] In order to further illustrate the operation process of the present invention, Figure 6 Taking the switching from the negative-earth return mode to the negative-metal return mode as an example, the current transfer process when the multi-port DC conversion switch is in operation is explained.

[0048] like Figure 2 As shown in the figure, the implementation process of the frequency-same / frequency-divided control method is explained by taking n=1 and N=2 as an example.VCB is the control signal of the commutation vacuum switch VCB, S VCB When it is in the close state, it means that VCB receives the closing signal. VCB When it is in the open state, it means that VCB receives the trip signal. IGBT1 is the control signal of IGBT1, S IGBT1 When it is in the on state, it means that IGBT1 receives the conduction signal, S IGBT1 When it is in the off state, it means that IGBT1 receives the shutdown signal. U SWO is the square wave voltage output by the square wave voltage source SWO, U E for U SWO The amplitude of . f IGBT1 is the switching frequency of IGBT1, and the square wave voltage U SWO The frequencies are equal. U C1 is the voltage across capacitor C1, i LC is the current in the LC branch, and the frequency of the two is f LC .time t Before 0, the commutation vacuum switch VCB is open and IGBT1 is in the on state. At time t0, IGBT1 is turned off and keeps off for 3 half waves. The square wave voltage U SWO Rise to U E , capacitor voltage U C1 It rises to the first positive peak during the first half-wave and maintains constant amplitude oscillation during the second and third half-waves. Considering the line loss, the second positive peak is slightly lower than the first positive peak. At the second positive peak, IGBT1 is turned on and continues to conduct for 1 half-wave. The square wave voltage U SWO Wait for the capacitor voltage to drop to zero U C1 When the forward voltage peak decreases to the reverse voltage peak, IGBT1 is turned off again. After one half-wave, the capacitor voltage U C1 When the off state lasts until the third half wave, the capacitor voltage U C1 It rises to the fourth forward peak. Considering the line loss, the fourth forward peak is slightly lower than the third forward peak. At the fourth peak, IGBT1 is turned on again, and the cycle enters the process of IGBT1 turning off for 3 half-waves and turning on for 1 half-wave. As the capacitor voltage UC1 The rising oscillating current i LC The amplitude of gradually increases, causing the current in the temporary current branch to pass through zero and the commutation vacuum switch VCB to extinguish.

[0049] like Figure 3 As shown in the figure, the implementation process of the frequency-same / frequency-divided control method is explained by taking n=2 and N=1 as an example. VCB is the control signal of the commutation vacuum switch VCB, S VCB When it is in the close state, it means that VCB receives the closing signal. VCB When it is in the open state, it means that VCB receives the trip signal. IGBT1 is the control signal of IGBT1, S IGBT1 When it is in the on state, it means that IGBT1 receives the conduction signal, S IGBT1 When it is in the off state, it means that IGBT1 receives the shutdown signal. IGBT2 is the control signal of IGBT2, S IGBT2 When it is in the on state, it means that IGBT2 receives the conduction signal, S IGBT2 When it is in the off state, it means that IGBT2 receives the shutdown signal. U SWO is the square wave voltage output by the square wave voltage source SWO, U E for U SWO The amplitude of . f IGBT1 is the switching frequency of IGBT1, and the square wave voltage U SWO The frequencies are equal. U C1 is the voltage across capacitor C1, i LC is the current in the LC branch, and the frequency of the two is f LC .time t Before 0, the commutation vacuum switch VCB is open and IGBT1 is in the on state. t At 0, IGBT1 is turned off and lasts for 1 half wave, and the square wave voltage source output voltage U E , capacitor voltage U C1 Rising to the first positive peak. At the first positive peak, IGBT1 is turned on and lasts for 1 half wave, the square wave voltage source output voltage is zero, and then it falls to the first reverse peak, at which point IGBT1 is turned off and lasts for 3 half waves. Capacitor voltage U C1 When it rises to the second positive peak, IGBT2 is turned on and lasts for one half wave. The capacitor voltageU C1 It drops to the reverse peak value, at which point IGBT2 is turned off and lasts for 3 half-waves. U C1 When the voltage rises to the third positive peak, IGBT1 is turned on for 1 half-wave and then turned off for 3 half-waves. IGBT1 and IGBT2 are turned on for 1 half-wave and turned off for 3 half-waves at the positive peak. U C1 The rising oscillating current i LC The amplitude of gradually increases, causing the current in the temporary current branch to pass through zero and the commutation vacuum switch VCB to extinguish.

[0050] Compared with the case where the trigger branch consists of 1 switch branch, the same frequency / divided frequency control method when the trigger branch consists of n (n=2,3,4...) parallel switch branches has more technical advantages. By reducing the switching frequency of the IGBT and cross-triggering the IGBT, , without changing the IGBT trigger frequency, the divergence speed of the resonant current is accelerated.

[0051] like Figure 4 As shown, the system operates in the negative pole-earth return line mode, and the earth return line current The main branch 2 of the sending-end multi-port DC conversion switch, the negative metal return current The current flows through the main branch 5 of the multi-port DC conversion switch at the sending end and the main branch C of the multi-port DC conversion switch at the receiving end. C The commutation vacuum switches VCB and VCB are all in the closed state, and the through-current vacuum switches K1, K3, K4, K A , K B All are in the open state, and the controllable conduction switch, controllable negative pressure source and controllable square wave voltage source of the sending / receiving end multi-port DC conversion switch are all in the off state. R n 、 L n Represents the equivalent resistance and equivalent inductance of the positive metal loop, R p 、 L p Represents the equivalent resistance and equivalent inductance of the negative metal loop, R e 、 L e represents the equivalent resistance and equivalent inductance of the grounding electrode line, k1, k2, k3 and k4 are isolation switches for current transfer, VT1, VT2, VT3 and VT4 are thyristor components that control the conduction direction of the negative voltage source. C2 is the negative voltage source, U C2is the voltage of the negative voltage source. Vt is the diode that provides the current path. SWO is a controllable square-wave voltage source. Inductor L and capacitor C1 form the LC branch of the square-wave resonant DC circuit breaker, and arrester MOV1 forms the arrester branch.

[0052] like Figure 5 As shown, in response to the operation mode switching instruction, the through-current vacuum switch K4 is closed, the main branch 2 and the main branch 4 are operated in parallel, and the earth return current and positive metal return current The sum is equal to the negative metal return current .

[0053] like Figure 6 As shown, the vacuum switch K2 is open and the current in the main branch 2 is It is a forward current, so VT1 and VT4 in the controllable negative voltage source are triggered at the same time to switch the negative voltage source to the commutation branch and trigger the IGBT in the controllable square wave power supply. f1 The positive thyristor assembly connected to the main branch 2 provides a path for the load current. Under the action of the negative voltage source, a circulating current is generated between the main branch 2 and the commutation branch. , the commutation branch current increases rapidly, the main branch 2 current It decreases rapidly to zero, the through-current vacuum switch K2 extinguishes the arc, and the earth return current flows through the sending-end commutation branch.

[0054] like Figure 7 As shown in the figure, after the through-current vacuum switch K2 extinguishes the arc, the controllable negative pressure source is connected to the diode component V t After the vacuum switch VCB is opened and the controllable square wave voltage source is triggered to generate a square wave voltage source with the same frequency as the LC resonant frequency, the square wave resonant DC circuit breaker establishes a transient voltage U tr , the commutation branch current gradually transfers to the main branch 4, that is, the earth return line current gradually transfers to the positive metal return line.

[0055] like Figure 8 As shown, the square wave resonant DC circuit breaker creates a transient voltage U tr The process is as follows: First, under the action of the square wave voltage of the same frequency, the resonant current The amplitude gradually increases. When the current superimposed on the commutation vacuum switch VCB passes through zero, VCB extinguishes the arc and the commutation branch current is transferred to the LC branch. Then, the current Charge capacitor C1. When the current across the arrester MOV1 rises to the operating voltage, MOV1 operates and the branch current is commutated. Transferred to the MOV branch, the MOV absorbs the energy and creates a transient voltage U tr, commutation branch current Gradually decreases to zero.

[0056] like Figure 9 As shown, the earth return line current is completely transferred to the positive metal return line, VT1 and VT4 in the controllable negative voltage source and the forward thyristor assembly connected to the main branch return to the off state, and the operation mode switching is completed.

[0057] like Figure 10 As shown, in t 0=4.0s ago, negative metal return current =5kA, positive metal return current =0.4kA, main branch 2 current =4.6kA, at this time the earth return line and the positive metal return line run in parallel.

[0058] At t0, the DC converter at the sending end responds to the operation mode switching instruction, opens the vacuum switch K2 and triggers the thyristors VT1 and VT4 in the controllable negative pressure source to cut the negative pressure source into the commutation branch, and triggers the IGBT in the controllable square wave power supply. f1 The forward thyristor assembly connected to the main branch 2 provides a path for the load current, such as Figure 11 As shown, the current i 2 drops to zero, the commutation branch current rises to the level of the earth return current.

[0059] like Figure 11 As shown, in t When 1=4.00095s, the commutation vacuum switch VCB is opened and the IGBT is turned off. f1 , so that the square wave voltage source output voltage U E , subsequent cross-triggering IGBT f1 and IGBT f2 , so that the square wave voltage source outputs a voltage wave with a frequency of 10kHz, which is the same as the resonant frequency of the LC branch. Under the action of the square wave, the current amplitude of the LC branch is The value gradually increases. When the temporary current branch current When the commutation vacuum switch VCB is extinguished, the commutation branch current Transfer to LC branch.

[0060] Current To charge the capacitor, When the voltage across the arrester reaches the operating voltage, the commutation branch current Gradually transferred to the MOV branch, the arrester MOV1 established a transient voltage of 148kV, forcing the earth return line current to transfer to the positive metal return line. Figure 10 As shown, the commutation branch current Gradually decreases, the positive metal return current Gradually rising, When the commutation branch current When the voltage drops to zero, VT1 and VT4 in the controllable negative voltage source and the forward thyristor assembly connected to the main branch return to the off state, and the operation mode switching is completed.

[0061] Therefore, the present invention utilizes the aforementioned control method for a multi-port DC converter switch based on a controllable negative pressure source, which offers the advantage of a simple control method. By selectively controlling the controllable conduction switch, the controllable negative pressure source, and the controllable square wave voltage source according to the current direction of the main branch to be disconnected, the main branch current in any direction can be transferred to the commutation branch and ultimately to other main branches. The control method for multi-port DC converter switches installed at either the sending or receiving end is consistent.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A control method for a multi-port DC converter switch based on a controllable negative pressure source, characterized in that: When the current of the main branch to be interrupted is a forward current, the following steps are included: S1. Before switching, the through-current vacuum switch and the commutation vacuum switch are both in the closed state, and the controllable square wave voltage source, the controllable negative pressure source, and the controllable conduction switch are all in the off state; S2, open the vacuum switch to trigger the thyristor in the controllable negative pressure source and , and trigger the forward conducting component connected to the main branch to be disconnected, forcing the current to be transferred to the commutation branch; S3, opening the commutation vacuum switch, and controlling the frequency of the controllable square wave voltage source to meet the same frequency or multiple frequency relationship with the resonant frequency of the LC branch through the same frequency / multiple frequency control method, and transferring the excitation current to the LC branch; S4, the load current charges the capacitor of the LC branch, and the voltage across the MOV branch gradually rises to the MOV operating voltage; S5, MOV operates, creates transient voltage, and transfers load current to other main branches; When the current of the main branch to be disconnected is a reverse current, the following steps are included: S1. Before switching, the through-current vacuum switch and the commutation vacuum switch are both in the closed state, and the controllable square wave voltage source, the controllable negative pressure source, and the controllable conduction switch are all in the off state; S2, open the vacuum switch to trigger the thyristor in the controllable negative pressure source and , and trigger the reverse conducting component connected to the main branch to be disconnected, forcing the current to transfer to the commutation branch; S3, opening the commutation vacuum switch, and controlling the frequency of the controllable square wave voltage source to meet the same frequency or multiple frequency relationship with the resonant frequency of the LC branch through the same frequency / multiple frequency control method, and transferring the excitation current to the LC branch; S4, the load current charges the capacitor of the LC branch, and the voltage across the MOV branch gradually rises to the MOV operating voltage; S5, MOV operates, creates transient voltage, and transfers load current to other main branches; The same frequency / divided frequency control method is implemented by controlling the IGBT switching frequency in the controllable square wave voltage source, satisfying: ； in, is the output frequency of the controllable square wave voltage source, is the resonant frequency of the LC branch; ; When the trigger branch consists of one switching branch, the frequency relationship is achieved through the switching frequency of the IGBT itself. The specific steps are: Shutdown And maintain 2N-1 capacitor voltage half waves; It turns on when the capacitor voltage reaches the Nth positive peak , maintain 1 half wave; The above shutdown and conduction process is repeated to form a periodic square wave output.

2. The control method of a multi-port DC converter switch based on a controllable negative pressure source according to claim 1, characterized in that: When the trigger branch consists of n parallel switch branches, n ≥ 2, the frequency relationship is achieved by cross-triggering multiple IGBTs. The specific steps are as follows: Turn off all IGBTs in sequence and wait for the capacitor voltage to reach the positive peak; Trigger the IGBT of each branch in sequence to conduct for half a cycle; The switching frequency and LC resonant frequency of a single IGBT satisfy: 。

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