Buck-Boost converter for super capacitor grid connection and fault ride-through control method thereof

Abstract

The invention discloses a Buck-Boost converter for super capacitor grid connection and a fault ride-through control method of the Buck-Boost converter. The Buck-Boost converter for grid connection of the super capacitor comprises a super capacitor module, an inductor, a first switch module, a second switch module, a thyristor module and a grid-connected side capacitor, and the super capacitor module is connected with the inductor in series and then connected with the second switch module in parallel; the first switch module, the thyristor module and the second switch module are connected in series and then are connected in parallel with the grid-connected side capacitor.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power equipment, and more specifically, to a Buck-Boost converter for supercapacitor grid connection and a fault ride-through control method thereof. Background Art

[0002] When renewable energy is connected to microgrids on a large scale, it will cause voltage fluctuations, power shocks, and increased harmonics, which will cause the grid to be unable to operate safely and stably. Therefore, it is necessary to deploy energy storage systems in the grid. The energy storage system can provide energy buffering between the power generation side and the power consumption side of the grid, so that renewable energy power generation devices can be well accepted by the large grid. At the same time, the power quality and reliability of the power generation system can also be improved. Power devices represented by supercapacitor energy storage have the characteristics of high power density, good dynamic performance, long cycle life and high charging and discharging efficiency, and have good development prospects.

[0003] At present, most DC / DC converters for supercapacitor grid-connected use bidirectional supercapacitor grid-connected Buck-Boost converters. When a short circuit fault occurs on the grid-connected side, the DC fault current rises quickly, has a high amplitude, and does not naturally cross the zero point. The relay protection and circuit breaker are not able to operate in time, and the fault current continues to flow for a long time through the diode in the supercapacitor grid-connected Buck-Boost converter, threatening the safety of the supercapacitor grid-connected Buck-Boost converter. How to adjust and design the existing supercapacitor grid-connected Buck-Boost converter to ensure the safety of the supercapacitor grid-connected Buck-Boost converter under short circuit faults has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a Buck-Boost converter for supercapacitor grid connection and a fault ride-through control method thereof.

[0005] According to one aspect of the present invention, a Buck-Boost converter for supercapacitor grid connection is provided, comprising: a supercapacitor module, an inductor, a first switch module, a second switch module, a thyristor module and a grid-connected capacitor, wherein

[0006] The supercapacitor module is connected in series with the inductor and then connected in parallel with the second switch module;

[0007] The first switch module, the thyristor module and the second switch module are connected in series and then connected in parallel with the grid-connected capacitor.

[0008] Optionally, the supercapacitor module includes supercapacitors and supercapacitor side capacitors connected in parallel.

[0009] Optionally, the first switch module includes a first switch tube and a first diode anti-parallel connection structure.

[0010] Optionally, the first switch tube and the second switch tube are fully controllable power electronic switch tubes.

[0011] Optionally, the second switch module includes a second switch tube and a second diode anti-parallel connection structure.

[0012] Optionally, the second switch tube is a fully controllable power electronic switch tube.

[0013] Optionally, the thyristor module includes a thyristor and a third diode anti-parallel connection structure.

[0014] Optionally, the thyristor is a half-controlled power electronic switch tube.

[0015] Optionally, the cathode of the thyristor is connected to the emitter of the first switching tube, and the anode of the thyristor is connected to the collector of the second switching tube.

[0016] According to another aspect of the present invention, there is provided a fault ride-through control method for a Buck-Boost converter for supercapacitor grid connection, comprising:

[0017] According to the detected grid-connected side voltage and grid-connected side current of the supercapacitor grid-connected Buck-Boost converter and the preset grid-connected side fault judgment criteria, the operating state of the supercapacitor grid-connected Buck-Boost converter is judged;

[0018] When the Buck-Boost converter for supercapacitor grid connection is operating normally, the first switch module and the second switch module are turned off according to the preset pulse width modulation, and the thyristor module is continuously triggered to realize the conversion of voltage levels and the transmission of high and low voltage side energy;

[0019] When a grid-connected fault occurs in the supercapacitor grid-connected Buck-Boost converter, the first switch module and the second switch module are locked, and the trigger signal of the thyristor module is cancelled. During the grid-connected capacitor discharge phase, the natural zero-crossing characteristic of the freewheeling current and the current zero-crossing self-shutdown characteristic of the thyristor module are used to achieve fast fault ride-through of the supercapacitor grid-connected Buck-Boost converter;

[0020] After isolating the fault point, restart the supercapacitor grid-connected Buck-Boost converter.

[0021] Optionally, the preset grid-connected side fault criterion is: the grid-connected side voltage drops to a set voltage threshold or the grid-connected side current exceeds a set current threshold.

[0022] Optionally, when the supercapacitor grid-connected Buck-Boost converter is operating normally, the first switch module and the second switch module are turned off according to a preset pulse width modulation control, and a trigger signal is continuously given to the thyristor module to achieve voltage level conversion and high and low voltage side energy transfer, including:

[0023] When the power flows from the high-voltage side to the low-voltage side, the Buck-Boost converter for supercapacitor grid connection works in the step-down mode, the first switch module works as the main switch, the second switch module is in the off state, and the low-voltage side voltage is adjusted by controlling the on and off time of the first switch module through preset pulse width modulation, so as to realize energy transmission from the high-voltage side to the low-voltage side;

[0024] When the power flows from the low-voltage side to the high-voltage side, the Buck-Boost converter for supercapacitor grid connection works in boost mode, the first switch module is in the off state, and the second switch module works as a main switch. The on and off time of the second switch module is controlled by preset pulse width modulation to adjust the high-voltage side voltage, thereby realizing energy transmission from the low-voltage side to the high-voltage side.

[0025] According to the detected grid-connected side voltage and grid-connected side current of the supercapacitor grid-connected Buck-Boost converter and the preset grid-connected side fault judgment criteria, the operating state of the supercapacitor grid-connected Buck-Boost converter is judged;

[0026] When the Buck-Boost converter for supercapacitor grid connection is operating normally, the first switch tube and the second switch tube are turned off according to the preset pulse width modulation, and the thyristor trigger signal is continuously given to realize the conversion of voltage level and the transmission of high and low voltage side energy;

[0027] When a grid-connected fault occurs in the Buck-Boost converter for supercapacitor grid connection, the first switch tube and the second switch tube are locked, and the trigger signal of the thyristor is cancelled. During the discharge phase of the grid-connected capacitor, the natural zero-crossing characteristic of the freewheeling current and the current zero-crossing self-shutdown characteristic of the thyristor are utilized to achieve fast fault ride-through of the Buck-Boost converter for supercapacitor grid connection;

[0028] After isolating the fault point, restart the supercapacitor grid-connected Buck-Boost converter.

[0029] Optionally, the preset grid-connected side fault criterion is: the grid-connected side voltage drops to a set voltage threshold or the grid-connected side current exceeds a set current threshold.

[0030] Optionally, when the supercapacitor grid-connected Buck-Boost converter is operating normally, the first switch tube and the second switch tube are turned off according to a preset pulse width modulation, and a thyristor trigger signal is continuously given to realize the conversion of voltage levels and the transmission of high and low voltage side energy, including:

[0031] When the power flows from the high-voltage side to the low-voltage side, the supercapacitor grid-connected Buck-Boost converter works in the step-down mode, the first switch tube works as the main switch, and the second switch tube is in the off state. The on and off time of the first switch tube is controlled by preset pulse width modulation to adjust the low-voltage side voltage, so as to realize energy transmission from the high-voltage side to the low-voltage side.

[0032] When the power flows from the low-voltage side to the high-voltage side, the Buck-Boost converter for supercapacitor grid connection works in boost mode, the first switch tube is in the off state, and the second switch tube works as the main switch. The on and off time of the second switch tube is controlled by preset pulse width modulation to adjust the high-voltage side voltage, thereby realizing energy transmission from the low-voltage side to the high-voltage side.

[0033] Therefore, according to the supercapacitor grid-connected Buck-Boost converter of the embodiment of the present invention, under the condition of a grid-connected side fault, the first switch module and the second switch module of the fully controlled power electronics are locked, and the trigger signal of the thyristor SCR is canceled. During the discharge of the grid-connected side capacitor CH, the fault current is superimposed on the reverse DC current generated by the grid-connected side capacitor CH in the diode freewheeling path, so as to block the internal current path of the diode freewheeling loop in the supercapacitor grid-connected Buck-Boost converter, thereby ensuring that all power electronic switch tubes do not need to withstand long-term fault surge current and have the ability of rapid fault self-clearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0035] Figure 1 It is a schematic diagram of the structure of a Buck-Boost converter for supercapacitor grid connection provided by the first aspect of the embodiment of the present invention;

[0036] Figure 2 It is a structural schematic diagram of an existing supercapacitor grid-connected Buck-Boost converter provided by an embodiment of the present invention;

[0037] Figure 3 It is a flow chart of a fault ride-through control method of a Buck-Boost converter for supercapacitor grid connection provided by an exemplary embodiment of the present invention;

[0038] Figure 4It is another flow chart of a fault ride-through control method of a supercapacitor grid-connected Buck-Boost converter provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0039] Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described here.

[0040] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0041] Those skilled in the art can understand that the terms "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices or modules, etc., and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0042] It should also be understood that, in the embodiments of the present invention, “plurality” may refer to two or more than two, and “at least one” may refer to one, two or more than two.

[0043] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more, unless explicitly limited or otherwise indicated in the context.

[0044] In addition, the term "and / or" in the present invention is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0045] It should also be understood that the description of the various embodiments of the present invention focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced to each other, and for the sake of brevity, they will not be described one by one.

[0046] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0047] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0048] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0049] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0050] Figure 1 is a schematic diagram of the structure of a Buck-Boost converter for supercapacitor grid connection provided by the first aspect of the embodiment of the present invention, with reference to Figure 1 As shown, the Buck-Boost converter for supercapacitor grid connection includes: a supercapacitor module, an inductor L, a first switch module, a second switch module, a thyristor module and a grid-connected capacitor CH, wherein

[0051] The supercapacitor module is connected in series with the inductor L and then connected in parallel with the second switch module;

[0052] The first switch module, the thyristor module and the second switch module are connected in series and then connected in parallel with the grid-connected capacitor CH.

[0053] Optionally, the supercapacitor module includes a supercapacitor and a supercapacitor side capacitor CL connected in parallel.

[0054] Optionally, the first switch module includes a first switch tube S1 and a first diode D1 anti-parallel connection structure.

[0055] Optionally, the first switch tube S1 is a fully controllable power electronic switch tube.

[0056] Optionally, the second switch module includes a second switch tube S2 and a second diode D2 anti-parallel connection structure.

[0057] Optionally, the second switch tube S2 is a fully controllable power electronic switch tube.

[0058] Optionally, the thyristor module includes a thyristor SCR and a third diode D3 anti-parallel connection structure.

[0059] Optionally, the thyristor SCR is a half-controlled power electronic switch tube.

[0060] Optionally, the cathode of the thyristor SCR is connected to the emitter of the first switch tube S1 , and the anode of the thyristor SCR is connected to the collector of the second switch tube S2 .

[0061] Specifically, Figure 2 FIG. 2 shows a schematic diagram of the topology of the existing supercapacitor grid-connected Buck-Boost converter. Figure 2As shown in the figure, when a bipolar short-circuit fault occurs, after the fault current reaches its peak value, the grid-connected capacitor voltage drops to zero, the IGBT is locked, and after the grid-connected fault current reaches its peak value, it will continue to flow in the diode of the supercapacitor grid-connected Buck-Boost converter. At this stage, the diode conducts a surge current exceeding its rated current for a long time, which lasts for hundreds of milliseconds. The accumulation of thermal stress will cause the diode temperature to exceed the limit and cause irreversible damage.

[0062] To solve this problem, Figure 1 The supercapacitor grid-connected Buck-Boost converter shown in the figure is proposed. The present invention aims to propose a supercapacitor grid-connected Buck-Boost converter with a fault ride-through control method for the converter, so that it can play a fast fault self-clearing function under a DC fault. Figure 1 As shown, the improved topology of the supercapacitor grid-connected Buck-Boost converter includes a first switch tube S1, a second switch tube S2, a thyristor SCR, a first diode D1, a second diode D2, a third diode D3, an inductor L, a supercapacitor side capacitor CL, and a grid-connected side capacitor CH of a fully controlled power electronic device; the first switch tube S1, the second switch tube S2, and the thyristor SCR are respectively connected in anti-parallel with the first diode D1, the second diode D2, and the third diode D3 and then connected in series, and the cathode of the thyristor SCR is connected to the emitter of the first switch tube S1, and the anode is connected to the collector of the second switch tube S2; the supercapacitor is connected in parallel with the supercapacitor side capacitor CL and then connected in series with the inductor L, and then connected in parallel to both ends of the second switch tube S2, and the inductor L is connected to the collector of the second switch tube S2; the grid-connected side capacitor CH is connected across the collector of the first switch tube S1 and the emitter of the second switch tube S2.

[0063] Furthermore, the first switch tube S1 and the second switch tube S2 can be IGBT, IGCT, GCT, IEGT, GTO, etc., which can actively control the on and off current; the thyristor SCR is a semi-controlled power electronic switch tube, which can only control the on current but cannot actively shut down the current, and has the characteristic of naturally shutting down when the current passes through zero after the trigger signal is canceled.

[0064] Therefore, the supercapacitor grid-connected supercapacitor grid-connected Buck-Boost converter provided by the present invention can cut off the current conduction path in the diode freewheeling circuit of the supercapacitor grid-connected Buck-Boost converter by locking the power electronic device under the grid-connected side fault, and has the grid-connected side fault self-clearing capability. In the discharge stage of the grid-connected capacitor CH, the fault current and the reverse DC current generated by the grid-connected capacitor CH in the diode freewheeling path are superimposed to make the thyristor SCR1 turn off at zero crossing, thereby preventing the power electronic switch tube from being damaged by long-term surge current, and improving the operating reliability of the supercapacitor grid-connected Buck-Boost converter.

[0065] In addition, other structures and functions of the control method of the Buck-Boost converter for supercapacitor grid-connected with fault ride-through capability in the embodiment of the present invention are known to those skilled in the art and will not be described in detail to reduce redundancy.

[0066] Figure 3 1 is a flow chart of a fault ride-through control method for a supercapacitor grid-connected Buck-Boost converter provided in accordance with a second aspect of an embodiment of the present invention. This embodiment can be applied to electronic devices, such as Figure 1 As shown, the fault ride-through control method 300 of the supercapacitor grid-connected Buck-Boost converter includes the following steps:

[0067] Step 301, judging the operating state of the supercapacitor grid-connected Buck-Boost converter according to the detected grid-connected side voltage, grid-connected side current and preset grid-connected side fault criterion of the supercapacitor grid-connected Buck-Boost converter;

[0068] Step 302, when the supercapacitor grid-connected Buck-Boost converter is operating normally, the first switch module and the second switch module are turned off according to the preset pulse width modulation, and a trigger signal is continuously given to the thyristor module to achieve voltage level conversion and high and low voltage side energy transfer;

[0069] Step 303, when a grid-connected fault occurs in the supercapacitor grid-connected Buck-Boost converter, the first switch module and the second switch module are locked, the trigger signal of the thyristor module is cancelled, and in the discharge phase of the grid-connected capacitor CH, the natural zero-crossing characteristic of the freewheeling current and the current zero-crossing self-shutdown characteristic of the thyristor module are used to achieve fast fault ride-through of the supercapacitor grid-connected Buck-Boost converter;

[0070] Step 304, restarting the supercapacitor grid-connected Buck-Boost converter after isolating the fault point.

[0071] Optionally, the preset grid-connected side fault criterion is: the grid-connected side voltage drops to a set voltage threshold or the grid-connected side current exceeds a set current threshold.

[0072] Optionally, when the supercapacitor grid-connected Buck-Boost converter is operating normally, the first switch module and the second switch module are turned off according to a preset pulse width modulation control, and a trigger signal is continuously given to the thyristor module to achieve voltage level conversion and high and low voltage side energy transfer, including:

[0073] When the power flows from the high-voltage side to the low-voltage side, the Buck-Boost converter for supercapacitor grid connection works in the step-down mode, the first switch module works as the main switch, the second switch module is in the off state, and the low-voltage side voltage is adjusted by controlling the on and off time of the first switch module through preset pulse width modulation, so as to realize energy transmission from the high-voltage side to the low-voltage side;

[0074] When the power flows from the low-voltage side to the high-voltage side, the Buck-Boost converter for supercapacitor grid connection works in boost mode, the first switch module is in the off state, and the second switch module works as a main switch. The on and off time of the second switch module is controlled by preset pulse width modulation to adjust the high-voltage side voltage, thereby realizing energy transmission from the low-voltage side to the high-voltage side.

[0075] Specifically, the fault ride-through control method of the supercapacitor grid-connected Buck-Boost converter proposed in the present invention can enable the converter to perform a fast fault self-clearing function under a DC fault. In normal operation and when a grid-connected fault is detected, the supercapacitor grid-connected Buck-Boost converter operates in different control modes to ensure that when a fault occurs on the grid-connected side, the current in the diode freewheeling circuit of the supercapacitor grid-connected Buck-Boost converter can pass zero during the discharge of the grid-connected capacitor, thereby preventing the freewheeling diode from being damaged by long-term surge current thermal stress, which has important application value for improving the reliability of the supercapacitor grid-connected converter. Figure 4 As shown, the specific implementation process is as follows:

[0076] During normal operation, the first switch tube S1 and the second switch tube S2 of the fully controlled power electronics in the Buck-Boost converter for supercapacitor grid connection are controlled according to PWM modulation, and at the same time, a trigger signal is continuously given to the thyristor SCR to make it equivalent to a diode. By controlling the on and off of the first switch tube S1 and the second switch tube S2 of the fully controlled power electronics, the conversion of the DC voltage level and the transmission of energy on the high and low voltage sides are realized. When the power flow direction is from the high voltage side to the low voltage side, the converter works in the buck mode, S1 works in the form of a main switch, S2 is in the off state, and the on and off time of S1 is controlled by PWM modulation, that is, the duty cycle is controlled to adjust the low voltage side voltage, and energy is transmitted from the high voltage side to the low voltage side; when the power flow direction is from the low voltage side to the high voltage side, the converter works in the boost mode, S1 is in the off state, S2 works in the form of a main switch, and the on and off time of S2 is controlled by PWM modulation, that is, the duty cycle is controlled to adjust the high voltage side voltage, and energy is transmitted from the low voltage side to the high voltage side. When a grid-connected fault is detected, the first switch tube S1 and the second switch tube S2 of the fully controlled power electronics are locked, and the trigger signal of the thyristor SCR is canceled. During the discharge phase of the grid-connected capacitor CH, the natural zero-crossing characteristics of the freewheeling current and the current zero-crossing self-shutdown characteristics of the thyristor SCR are utilized to achieve fast fault ride-through of the supercapacitor grid-connected Buck-Boost converter; after isolating the fault point, the supercapacitor grid-connected Buck-Boost converter is restarted.

[0077] During normal operation, the fully controlled power electronic switch tubes S1 and S2 in the supercapacitor grid-connected Buck-Boost converter are controlled according to PWM modulation, and the trigger signal of the thyristor SCR1 is continuously given to make it equivalent to a diode. By controlling the on and off of the fully controlled power electronic switch tubes S1 and S2, the conversion of the DC voltage level and the transfer of energy on the high and low voltage sides are realized; when a grid-connected side fault is detected, the fully controlled power electronic switch tubes S1 and S2 are locked, and the trigger signal of SCR1 is canceled. In the discharge stage of the grid-connected capacitor CH, the natural zero-crossing characteristic of the freewheeling current and the current zero-crossing self-shutdown characteristic of the thyristor SCR1 are used to realize the fast fault ride-through of the supercapacitor grid-connected Buck-Boost converter; after isolating the fault point, the supercapacitor grid-connected Buck-Boost converter is restarted.

[0078] Furthermore, the grid-connected side fault detection method is to use the grid-connected side voltage drop to a set threshold as a grid-connected side fault judgment criterion;

[0079] Furthermore, the grid-connected side fault detection method uses the grid-connected side current exceeding a set threshold as a grid-connected side fault judgment criterion.

[0080] In the present invention, the fully controlled power electronic switch tubes S1 and S2 can be IGBT, IGCT, GCT, IEGT, GTO, etc., which can actively control the on and off current; the thyristor SCR1 is a semi-controlled power electronic switch tube, which can only control the on current but cannot actively shut down the current, and has the characteristic of naturally shutting down when the current passes through zero after the trigger signal is canceled.

[0081] In a specific embodiment of the supercapacitor grid-connected supercapacitor grid-connected Buck-Boost converter fault ride-through control method provided by the present invention, the grid-connected side fault detection method is to detect that the grid-connected side voltage Udc drops to less than a set threshold Uset.

[0082] In a specific embodiment of the supercapacitor grid-connected supercapacitor grid-connected Buck-Boost converter fault ride-through control method provided by the present invention, the grid-connected side fault detection method is to detect that the grid-connected side current Idc of the supercapacitor grid-connected Buck-Boost converter rises to be greater than the set threshold value Iset.

[0083] Therefore, according to the supercapacitor grid-connected supercapacitor grid-connected Buck-Boost converter fault ride-through control method of the embodiment of the present invention, under the grid-connected side fault, the first switch tube S1 and the second switch tube S2 of the fully controlled power electronics are locked, and the trigger signal of the thyristor SCR is canceled. During the discharge of the grid-connected side capacitor CH, the fault current is superimposed on the reverse DC current generated by the grid-connected side capacitor CH in the diode freewheeling path, so as to block the internal current path of the diode freewheeling loop in the supercapacitor grid-connected Buck-Boost converter, thereby ensuring that all power electronic switch tubes do not need to withstand long-term fault surge current and have the ability of rapid fault self-clearing.

[0084] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A Buck-Boost converter for supercapacitor grid connection, characterized in that: include: A supercapacitor module, an inductor (L), a first switch module, a second switch module, a thyristor module and a grid-connected capacitor (CH), wherein The super capacitor module is connected in series with the inductor (L) and then connected in parallel with the second switch module; The first switch module, the thyristor module and the second switch module are connected in series and then connected in parallel with the grid-connected capacitor (CH).

2. The Buck-Boost converter for supercapacitor grid connection according to claim 1, characterized in that: The super capacitor module includes a super capacitor and a super capacitor side capacitor (CL) connected in parallel.

3. The Buck-Boost converter for supercapacitor grid connection according to claim 1, characterized in that: The first switch module comprises a first switch tube (S1) and a first diode (D1) in an anti-parallel connection structure.

4. The Buck-Boost converter for supercapacitor grid connection according to claim 3, characterized in that: The first switch tube (S1) and the second switch tube (S2) are fully controllable power electronic switch tubes.

5. The Buck-Boost converter for supercapacitor grid connection according to claim 3, characterized in that: The second switch module includes a second switch tube (S2) and a second diode (D2) connected in anti-parallel.

6. The Buck-Boost converter for supercapacitor grid connection according to claim 5, characterized in that: The thyristor module comprises a thyristor (SCR) and a third diode (D3) in an anti-parallel connection structure.

7. The Buck-Boost converter for supercapacitor grid connection according to claim 6, characterized in that: The thyristor (SCR) is a semi-controlled power electronic switch tube.

8. The Buck-Boost converter for supercapacitor grid connection according to claim 6, characterized in that: The cathode of the thyristor (SCR) is connected to the emitter of the first switch tube (S1), and the anode of the thyristor (SCR) is connected to the collector of the second switch tube (S2).

9. A fault ride-through control method for a converter, applied to the converter according to any one of claims 1 to 8, characterized in that: include: Determine the operating state of the supercapacitor grid-connected Buck-Boost converter according to the detected grid-connected side voltage, grid-connected side current and preset grid-connected side fault criterion of the supercapacitor grid-connected Buck-Boost converter; When the supercapacitor grid-connected Buck-Boost converter is operating normally, the first switch module and the second switch module are turned off according to the preset pulse width modulation, and a trigger signal is continuously given to the thyristor module to achieve voltage level conversion and high- and low-voltage side energy transfer; When a grid-connected side fault occurs in the supercapacitor grid-connected Buck-Boost converter, the first switch module and the second switch module are locked, the trigger signal of the thyristor module is cancelled, and in the discharge phase of the grid-connected capacitor (CH), the natural zero-crossing characteristic of the freewheeling current and the current zero-crossing self-shutdown characteristic of the thyristor module are used to achieve fast fault ride-through of the supercapacitor grid-connected Buck-Boost converter; After isolating the fault point, the supercapacitor grid-connected Buck-Boost converter is restarted.

10. The method according to claim 9, characterized in that The preset grid-connected side fault criterion is: the grid-connected side voltage drops to a set voltage threshold or the grid-connected side current exceeds a set current threshold.

11. The method according to claim 9, characterized in that When the supercapacitor grid-connected Buck-Boost converter is operating normally, the first switch module and the second switch module are turned off according to the preset pulse width modulation, and a trigger signal is continuously given to the thyristor module to achieve voltage level conversion and high and low voltage side energy transmission, including: When the power flows from the high-voltage side to the low-voltage side, the supercapacitor grid-connected Buck-Boost converter operates in a step-down mode, the first switch module operates as a main switch, the second switch module is in an off state, and the low-voltage side voltage is adjusted by controlling the on and off time of the first switch module through the preset pulse width modulation, so as to realize energy transmission from the high-voltage side to the low-voltage side; When the power flows from the low-voltage side to the high-voltage side, the supercapacitor grid-connected Buck-Boost converter operates in a boost mode, the first switch module is in an off state, and the second switch module operates as a main switch. The on and off time of the second switch module is controlled by the preset pulse width modulation to adjust the high-voltage side voltage, thereby realizing energy transmission from the low-voltage side to the high-voltage side.

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