Capacitor with overvoltage protection device, flexible DC power module and overvoltage protection method

Abstract

The invention provides a capacitor with an overvoltage protection device, a flexible DC power module and an overvoltage protection method. The capacitor comprises a capacitor body and the overvoltage protection device. The capacitor body is connected with the overvoltage protection device; the overvoltage protection device is used for being switched on when the voltage value of the capacitor body exceeds a first threshold value, carrying out energy consumption on the capacitor body and cutting off when the voltage value of the capacitor body is lower than a second threshold value; the first threshold is greater than a voltage standard value of the capacitor body, and the second threshold is smaller than the voltage standard value of the capacitor body. According to the invention, the overvoltage protection device is integrated in the capacitor, so that rapid response can be realized and redundant power can be consumed when a huge power difference is generated between a transmitting-end converter station and a receiving-end converter station due to system faults of extra-high-voltage flexible direct current, and the problem of rapid rise of system direct-current voltage caused by the power difference is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a capacitor with an overvoltage protection device, a flexible direct current power module and an overvoltage protection method. Background Art

[0002] In the context of today's energy structure transformation, the efficient use and stable transmission of new energy have become important issues in the global energy field. Especially in the field of long-distance new energy transmission, flexible direct current transmission technology has attracted widespread attention because it can achieve long-distance, large-capacity and high-efficiency power transmission. The application of this technology can not only improve the utilization rate of new energy, but also effectively support the stable operation of the power grid, which is of great significance for promoting the optimization of energy structure and sustainable development.

[0003] However, in the specific practice of flexible DC transmission applications, especially in renewable energy grid-connected systems such as offshore wind power, system stability and safety face severe challenges. When a fault occurs in the receiving power grid, a huge power difference will be generated between the sending and receiving ends in a short time due to the inability to lock the converter to prevent large-scale disconnection of wind turbines. This power difference will cause the system DC voltage to rise rapidly, which in turn poses an overvoltage risk to the flexible DC power module. In order to stabilize the system DC voltage and protect the power module, energy-consuming technology is currently widely used to consume excess system power. However, this method requires independent energy-consuming equipment, which not only occupies land resources, but also has high costs, which is not conducive to the economic benefits and environmental friendliness of new energy projects. Summary of the invention

[0004] In view of this, the present invention aims to propose a capacitor with an overvoltage protection device, a flexible DC power module and an overvoltage protection method, which are used to solve the problem of realizing the overvoltage protection function when the capacitor voltage of the flexible DC power module rises rapidly, thereby ensuring that the offshore wind power grid-connected system can safely pass through the fault and avoid the new energy system from being disconnected from the grid.

[0005] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, the present invention provides a capacitor with an overvoltage protection device, comprising:

[0007] Capacitor body and overvoltage protection device;

[0008] The capacitor body is connected to the overvoltage protection device;

[0009] The overvoltage protection device is used to be put into operation when the voltage value of the capacitor body exceeds a first threshold value, and consume energy of the capacitor body until the voltage value of the capacitor body is lower than a second threshold value;

[0010] The first threshold is greater than the standard voltage value of the capacitor body, and the second threshold is less than the standard voltage value of the capacitor body.

[0011] Further, the capacitor body and the overvoltage protection device are connected in parallel, and the overvoltage protection device includes: a discharge resistor and a controllable switch;

[0012] One end of the discharge resistor is connected to one end of the capacitor body, and the other end is connected to the other end of the capacitor body through a controllable switch;

[0013] The controllable switch is used to close when the voltage value of the capacitor body exceeds a first threshold value to input the discharge resistor, and is also used to open when the voltage value of the capacitor body is lower than a second threshold value to cut off the discharge resistor;

[0014] The bleeder resistor in the switched-on state is used to consume energy from the capacitor body.

[0015] Furthermore, the first threshold is 1.1 times the standard value of the capacitor voltage, and the second threshold is 0.9 times the standard value of the capacitor voltage.

[0016] Furthermore, the overvoltage protection device further includes: an overvoltage protection board;

[0017] The overvoltage protection board is used to compare the voltage value of the capacitor body with the first threshold and the second threshold. If it exceeds the first threshold, the overvoltage protection device is controlled to be turned on. If it is lower than the second threshold, the overvoltage protection device is controlled to be turned off.

[0018] Furthermore, the overvoltage protection board includes: a voltage sampling module;

[0019] The voltage sampling module is used to collect the voltage value of the capacitor body in real time and transmit it to the overvoltage protection board.

[0020] In a second aspect, the present invention provides a flexible DC power module, comprising:

[0021] Flexible DC power unit and capacitor unit;

[0022] Flexible DC power unit and capacitor unit connection;

[0023] Flexible DC power unit is used for power conversion;

[0024] The capacitor unit includes a capacitor for storing and releasing electric energy during the conversion process to support the operation of the flexible DC power unit;

[0025] The capacitor is the capacitor with an overvoltage protection device according to the first aspect.

[0026] Furthermore, when the number of capacitors in the capacitor unit is not less than two, each capacitor is connected in parallel and isolated so that each capacitor works independently in its own space.

[0027] Furthermore, the capacitor unit is packaged as a whole and then connected to the flexible DC power unit.

[0028] Furthermore, the flexible DC power unit also includes:

[0029] High-power controllable switch device string for converter valve, self-powered power supply and bypass switch;

[0030] The high-power controllable switch device string for the converter valve is used to realize the conversion of electric energy;

[0031] The self-powered power supply is used to provide the power required for the operation of the flexible DC power module;

[0032] The bypass switch is used to protect the flexible DC power module.

[0033] In a third aspect, the present invention provides an overvoltage protection method, which is implemented based on the capacitor with an overvoltage protection device as in the first aspect, and comprises the following steps:

[0034] Continuously collect the voltage value of the capacitor when the capacitor starts to charge;

[0035] When the voltage value of the capacitor exceeds a first threshold value, the overvoltage protection device is controlled to be activated;

[0036] Using overvoltage protection devices to dissipate energy from capacitors;

[0037] When the voltage value of the capacitor is lower than the second threshold value, the overvoltage protection device is controlled to be cut off, and the overvoltage protection action is completed.

[0038] In summary, the present invention provides a capacitor with an overvoltage protection device, including a capacitor body and an overvoltage protection device; the capacitor body and the overvoltage protection device are connected; the overvoltage protection device is used to be put into operation when the voltage value of the capacitor body exceeds a first threshold value, and consume energy of the capacitor body until the voltage value of the capacitor body is lower than a second threshold value, and is cut off; the first threshold value is greater than the voltage standard value of the capacitor body, and the second threshold value is less than the voltage standard value of the capacitor body. By integrating an overvoltage protection device in the capacitor, the present invention can respond quickly when a huge power difference occurs between the sending and receiving ends, consume excess power, thereby avoiding the problem of rapid rise in system DC voltage caused by the power difference, and improving the stability of the system. In addition, the overvoltage protection device can automatically respond to voltage changes without manual intervention, reducing maintenance costs and operational complexity, while improving the response speed and control accuracy of the system.

[0039] The present invention also provides a flexible DC power module and an overvoltage protection method. The module and the method are implemented based on a capacitor with an overvoltage protection device. When implemented, they have similar effects to those of the capacitor, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 An electrical connection schematic diagram of a single capacitor with an overvoltage protection device provided in an embodiment of the present invention;

[0042] Figure 2 An electrical connection schematic diagram of a plurality of capacitors with overvoltage protection devices provided in an embodiment of the present invention connected in parallel and applied in a flexible DC power module;

[0043] Figure 3 A flow chart of an overvoltage protection method provided by an embodiment of the present invention.

[0044] In the above drawings: 1-capacitor, 2-capacitor body, 3-controllable switch, 4-discharge resistor, 5-flexible DC power unit. DETAILED DESCRIPTION

[0045] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The technical problem that the present invention aims to solve is mainly how to effectively protect the long-distance renewable energy transmission system from overvoltage damage via flexible DC transmission, especially when the receiving end power grid fails. In this specific context, the inability to lock the converter to prevent large-scale disconnection of wind turbines from the grid leads to a huge instantaneous power difference between the transmitting and receiving ends. This power difference will cause a rapid rise in the system DC voltage and the power module capacitor voltage, thereby causing a short-term overvoltage problem for the flexible DC power module, which may damage the power module and affect the stability and safety of the system.

[0047] Traditional solutions use energy-consuming technologies to consume excess system power to stabilize the voltage of the DC system. Although this approach can solve the overvoltage problem to a certain extent, it requires independent energy-consuming equipment, which not only occupies valuable land resources but also adds additional financial costs. These factors limit the economic benefits and environmental friendliness of new energy projects, especially in space-constrained occasions such as offshore wind power.

[0048] In response to this technical problem, the purpose of the present invention is to realize the overvoltage protection function when the capacitor voltage of the flexible DC power module rises rapidly by proposing a capacitor with an overvoltage protection device, a flexible DC power module including the capacitor, and a corresponding overvoltage protection method. This method aims to avoid large-scale disconnection of new energy systems due to receiving-end power grid failures, ensure that the offshore wind power grid-connected system can safely pass through the fault period, and meet the requirements of the wind power access guidelines to provide further support for the power grid; on the other hand, the power module has direct overvoltage protection capabilities and rapid response capabilities while maintaining a compact structure.

[0049] An embodiment of a capacitor with an overvoltage protection device according to the present invention is described in detail below.

[0050] The embodiment of the present invention provides a capacitor with an overvoltage protection device, including: a capacitor body and an overvoltage protection device, wherein the capacitor body and the overvoltage protection device are connected. The overvoltage protection device is used to be put into operation when the voltage value of the capacitor body exceeds a first threshold value, and consumes energy of the capacitor body until the voltage value of the capacitor body is lower than a second threshold value, and is cut off; the first threshold value is greater than the standard voltage value of the capacitor body, and the second threshold value is less than the standard voltage value of the capacitor body.

[0051] It should be noted that the capacitor body is the main part of the capacitor, responsible for storing and releasing electrical energy. In power systems, capacitors are often used to improve power factor, filtering, energy storage, etc. The capacitor body is usually composed of a capacitor core, an insulating medium, and an electrode plate, which are encapsulated in a shell.

[0052] An overvoltage protection device is a safety device designed to automatically start when the voltage of the capacitor body exceeds a predetermined safety threshold to prevent damage caused by excessive voltage. An overvoltage protection device can include a variety of components, such as metal oxide varistors (MOVs), spark gaps, silicon rectifiers, etc. These components can quickly conduct when the voltage is abnormal, providing a bypass for overvoltage, thereby protecting the capacitor body.

[0053] The overvoltage protection device is designed with an automatic mechanism. When the voltage value of the capacitor body exceeds the first threshold (i.e., the overvoltage threshold), the device will automatically start to work and start to consume the energy stored in the capacitor. This energy consumption process is usually achieved by converting energy into heat or other forms of energy. Once the voltage of the capacitor body drops below the second threshold (i.e., the reset threshold), the overvoltage protection device will automatically cut off and stop the energy consumption process to avoid unnecessary energy loss.

[0054] The first threshold and the second threshold are the set voltage safety limits. The first threshold is greater than the voltage standard value of the capacitor body, which means that when the voltage exceeds its normal working voltage, the overvoltage protection device will start. The second threshold is less than the voltage standard value, which is the condition for the overvoltage protection device to stop working, ensuring that the voltage drops below the safe level. This design ensures that the capacitor can continue to work normally after the voltage returns to normal.

[0055] This embodiment provides a capacitor with an overvoltage protection device. By integrating the overvoltage protection device in the capacitor, it can respond quickly when a huge power difference occurs between the sending and receiving ends, consume excess power, thereby avoiding the problem of rapid rise in system DC voltage caused by the power difference and improving the stability of the system. In addition, the overvoltage protection device can automatically respond to voltage changes without manual intervention, reducing maintenance costs and operational complexity, while improving the response speed and control accuracy of the system.

[0056] In one embodiment, the capacitor body and the overvoltage protection device are connected in parallel, and the overvoltage protection device includes: a discharge resistor and a controllable switch;

[0057] One end of the discharge resistor is connected to one end of the capacitor body, and the other end is connected to the other end of the capacitor body through a controllable switch;

[0058] The controllable switch is used to close when the voltage value of the capacitor body exceeds a first threshold value to input the discharge resistor, and is also used to open when the voltage value of the capacitor body is lower than a second threshold value to cut off the discharge resistor;

[0059] The bleeder resistor in the switched-on state is used to consume energy from the capacitor body.

[0060] In this embodiment, the capacitor body and the overvoltage protection device are connected in parallel. When the capacitor is working, the overvoltage protection device is also in a standby state, ready to intervene at any time.

[0061] The controllable switch is a key component that connects the bleeder resistor and the capacitor. It is responsible for closing when the voltage of the capacitor body exceeds the first threshold (i.e., the overvoltage threshold), so that the bleeder resistor is put into operation and consumes the energy in the capacitor. When the voltage of the capacitor body drops below the second threshold (i.e., the safety voltage threshold), the controllable switch is disconnected and the bleeder resistor is cut off to avoid unnecessary energy loss.

[0062] When the controllable switch is closed, the bleeder resistor is put into operation, and the energy stored in the capacitor is converted into heat energy through the bleeder resistor, thereby realizing energy consumption. This process continues until the voltage of the capacitor drops below a safe level.

[0063] In one embodiment, the first threshold is 1.1 times the standard value of the capacitor voltage, and the second threshold is 0.9 times the standard value of the capacitor voltage.

[0064] In this embodiment, the first threshold is the voltage level that triggers the overvoltage protection device to start. When the voltage of the capacitor exceeds 1.1 times its standard voltage, the voltage has risen to a potentially dangerous level that may cause damage to the capacitor or other system components. At this time, the controllable switch of the overvoltage protection device will close, activate the discharge resistor, and start the energy consumption process to reduce the voltage of the capacitor.

[0065] The second threshold is the voltage level that determines the overvoltage protection device should stop working. When the voltage of the capacitor drops to 0.9 times its standard voltage, the voltage has dropped to a safe range and no further energy consumption is required. At this point, the controllable switch will be disconnected, cutting off the discharge resistor and ending the overvoltage protection process. In this way, the capacitor can continue to operate within its normal operating voltage range without wasting energy or damaging the capacitor.

[0066] In one embodiment, the overvoltage protection device further includes: an overvoltage protection board;

[0067] The overvoltage protection board is used to compare the voltage value of the capacitor with a first threshold and a second threshold. If the voltage value exceeds the first threshold, the overvoltage protection device is controlled to be activated; if the voltage value is lower than the second threshold, the overvoltage protection device is controlled to be deactivated.

[0068] In this embodiment, an overvoltage protection board is integrated in the overvoltage protection device, and its main function is to monitor the voltage level of the capacitor and compare it with the preset safety threshold. When the voltage of the capacitor exceeds the first threshold, the overvoltage protection board will send a control signal to trigger the input of the overvoltage protection device. This action is to protect the capacitor from damage caused by excessively high voltage.

[0069] On the contrary, when the voltage of the capacitor drops below the second threshold, the overvoltage protection board will send another control signal to cut off the overvoltage protection device. This action marks the end of the overvoltage event and the capacitor can resume normal operation.

[0070] In one embodiment, the overvoltage protection board further includes: a voltage sampling module;

[0071] The voltage sampling module is used to collect the voltage value of the capacitor body in real time and transmit it to the overvoltage protection board.

[0072] In this embodiment, the voltage sampling module is used to monitor the real-time voltage level of the capacitor and transmit the data to the overvoltage protection board.

[0073] Based on the above embodiment, a capacitor with an overvoltage protection device is designed, and its electrical connection principle is as follows: Figure 1 As shown, the capacitor body 2, the controllable switch 3, the discharge resistor 4 and the overvoltage protection board are integrated inside the capacitor body 2. The controllable switch 3 and the discharge resistor 4 are connected in series to form an overvoltage protection device, and are connected in parallel with the capacitor body 2.

[0074] When the capacitor is working, the capacitor body 2 is charged normally and stores energy. The controllable switch 3 is in the disconnected state, and the discharge resistor 4 does not participate in the operation of the circuit, so it does not consume energy. When the voltage of the capacitor body 2 rises to exceed the first threshold value (1.1 times the standard value of the capacitor voltage), the controllable switch 3 receives a control signal and closes quickly. The closing of the controllable switch 3 makes the discharge resistor 4 connected in parallel with the capacitor body 2. At this time, the energy stored in the capacitor body 2 begins to be consumed in the form of heat energy through the discharge resistor 3. As the energy is continuously consumed through the discharge resistor 3, the voltage of the capacitor body 2 gradually decreases. The design of the discharge resistor 3 must ensure that the energy of the capacitor body 2 can be effectively consumed during the overvoltage period, and at the same time, it has sufficient thermal stability to cope with the heat generated during the energy consumption process. When the voltage of the capacitor body 2 drops below the second threshold value (0.9 times the standard value of the capacitor voltage), the controllable switch 3 receives a control signal again and disconnects the discharge resistor 3. At this time, the capacitor body 2 continues to work normally at its rated voltage, and the discharge resistor 3 no longer participates in the operation of the circuit, and the system returns to normal.

[0075] An embodiment of the present invention also provides a flexible DC power module, comprising: a flexible DC power unit and a capacitor unit; the flexible DC power unit and the capacitor unit are connected; the flexible DC power unit is used to convert electric energy; the capacitor unit includes a capacitor, which is used to store and release electric energy during the conversion process to support the operation of the flexible DC power unit; the capacitor is the capacitor with an overvoltage protection device of the first aspect.

[0076] It should be noted that the flexible DC power unit is the part of the module responsible for power conversion. It uses voltage source converter (VSC) technology to convert AC to DC or convert DC back to AC through self-shutdown devices (such as IGBT) and pulse width modulation (PWM) technology. This conversion technology can achieve independent decoupling control of active and reactive power, supply power to the passive network, and there is no need for communication between converter stations, making it easy to form a multi-terminal DC system.

[0077] The capacitor unit includes one or more capacitors, which play the role of storing and releasing electric energy in the process of electric energy conversion. The voltage standard value of the capacitor is the rated working voltage determined when it is designed. In the present invention, the capacitor unit also includes an overvoltage protection device, which can automatically start when the voltage value of the capacitor body exceeds a first threshold value, and consume the energy in the capacitor through a discharge resistor until the voltage drops below a second threshold value, thereby protecting the capacitor from overvoltage damage.

[0078] The flexible DC power module provided in this embodiment can not only effectively convert electric energy, but also automatically start the protection mechanism when an overvoltage condition is detected to ensure the safe and stable operation of the system. This integrated solution reduces the demand for independent energy-consuming equipment, reduces costs and land occupation, and improves the economic benefits and environmental friendliness of new energy projects. At the same time, this automatic response mechanism improves the safety and stability of the system, reduces maintenance costs and potential system failure risks.

[0079] In one embodiment, when the number of capacitors in the capacitor unit is not less than two, each capacitor is connected in parallel and isolated so that each capacitor works independently in its own space.

[0080] In this embodiment, the main technical conditions of the capacitor include winding, gold spraying, polymerization (heat treatment), semi-testing, welding, assembly, pouring, argon arc welding sealing, etc. Each link must be strictly controlled to ensure the manufacturing quality and product reliability of the capacitor.

[0081] In one embodiment, the capacitor unit is packaged as a whole and then connected to the flexible DC power unit. The entire module is in a closed housing to ensure that a single module failure will not affect the normal operation of adjacent modules.

[0082] like Figure 2 As shown, multiple capacitors 1 are connected in parallel with an overvoltage protection device to form a complete capacitor. Each capacitor is isolated by a metal plate and located in a different space to ensure that a single capacitor failure will not affect the normal operation of the remaining capacitors. Each capacitor 1 is connected in parallel with a flexible DC power unit 5.

[0083] In one embodiment, the flexible DC power unit also includes: a string of high-power controllable switching devices for converter valves, a self-energy power supply and a bypass switch; the string of high-power controllable switching devices for converter valves is used to realize the conversion of electric energy; the self-energy power supply is used to provide the required power for the operation of the flexible DC power module; the bypass switch is used to protect the flexible DC power module.

[0084] In this embodiment, the high-power controllable switch device string for the converter valve is formed by crimping the high-power controllable switch device for the converter valve, the high-power anti-parallel diode, and the heat sink between the devices. The self-powered power supply and the bypass switch are power units of the flexible DC power module. The high-power controllable switch device for the converter valve needs to comprehensively consider the device's steady-state current margin and overcurrent shutdown capability; the high-power anti-parallel diode needs to comprehensively consider the device's forward DC current and operating junction temperature; the self-powered power supply needs to comprehensively consider the input and output voltage range and related parameters of the power supply; the bypass switch needs to consider the rapidity of the device's action and the current and voltage tolerance requirements.

[0085] like Figure 3 As shown, an embodiment of the present invention further provides an overvoltage protection method, which is implemented based on a capacitor with an overvoltage protection device as in the above embodiment, and includes the following steps:

[0086] S1: continuously collect the voltage value of the capacitor when the capacitor starts to charge;

[0087] S2: When the voltage value of the capacitor exceeds the first threshold, the overvoltage protection device is controlled to be activated;

[0088] S3: using the overvoltage protection device to consume the energy of the capacitor;

[0089] S4: When the voltage value of the capacitor is lower than the second threshold value, the overvoltage protection device is controlled to be cut off, and the overvoltage protection action is completed.

[0090] The present invention can safely, efficiently and repeatedly perform overvoltage protection on capacitors, avoid unsafe factors caused by excessive capacitor voltage or slow capacitor voltage release in flexible DC power units and reduce time costs, and can automatically collect capacitor information, improve collection accuracy and facilitate subsequent related personnel to perform such analysis; in addition, the built-in overvoltage protection device of the capacitor can maintain the directness of the power unit overvoltage protection and the compactness of the power unit structure.

[0091] 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 aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A capacitor with an overvoltage protection device, characterized in that: include: Capacitor body and overvoltage protection device; The capacitor body is connected to the overvoltage protection device; The overvoltage protection device is used to be activated when the voltage value of the capacitor body exceeds a first threshold value, and consume energy of the capacitor body until the voltage value of the capacitor body is lower than a second threshold value, and then be cut off; The first threshold is greater than a standard voltage value of the capacitor body, and the second threshold is less than a standard voltage value of the capacitor body.

2. A capacitor with an overvoltage protection device according to claim 1, characterized in that: The capacitor body and the overvoltage protection device are connected in parallel, and the overvoltage protection device includes: a discharge resistor and a controllable switch; One end of the discharge resistor is connected to one end of the capacitor body, and the other end is connected to the other end of the capacitor body through the controllable switch; The controllable switch is used to close when the voltage value of the capacitor body exceeds the first threshold value to input the discharge resistor, and is also used to open when the voltage value of the capacitor body is lower than the second threshold value to cut off the discharge resistor; The discharge resistor in the switched-on state is used to consume energy of the capacitor body.

3. A capacitor with an overvoltage protection device according to claim 1, characterized in that: The first threshold is 1.1 times the standard value of the capacitor voltage, and the second threshold is 0.9 times the standard value of the capacitor voltage.

4. A capacitor with an overvoltage protection device according to claim 1, characterized in that: The overvoltage protection device further comprises: an overvoltage protection plate; The overvoltage protection board is used to compare the voltage value of the capacitor body with the first threshold and the second threshold. If the voltage value exceeds the first threshold, the overvoltage protection device is controlled to be activated. If the voltage value is lower than the second threshold, the overvoltage protection device is controlled to be deactivated.

5. A capacitor with an overvoltage protection device according to claim 4, characterized in that: The overvoltage protection board comprises: a voltage sampling module; The voltage sampling module is used to collect the voltage value of the capacitor body in real time and transmit it to the overvoltage protection board.

6. A flexible DC power module, characterized in that: include: Flexible DC power unit and capacitor unit; The flexible DC power unit is connected to the capacitor unit; The flexible DC power unit is used for electric energy conversion; The capacitor unit includes a capacitor for storing and releasing electric energy during the conversion process to support the operation of the flexible DC power unit; The capacitor is a capacitor with an overvoltage protection device as described in any one of claims 1 to 5.

7. A flexible DC power module according to claim 6, characterized in that: When the number of the capacitors in the capacitor unit is not less than two, each of the capacitors is connected in parallel and isolated so that each of the capacitors works independently in its own space.

8. The flexible DC power module according to claim 7, characterized in that: The capacitor unit is packaged as a whole and then connected to the flexible DC power unit.

9. The flexible DC power module according to claim 6, characterized in that: The flexible DC power unit also includes: High-power controllable switch device string for converter valve, self-powered power supply and bypass switch; The converter valve uses a high-power controllable switch device string to achieve the conversion of electric energy; The self-powered power supply is used to provide the power required for the operation of the flexible DC power module; The bypass switch is used to protect the flexible DC power module.

10. An overvoltage protection method, characterized in that: The method is implemented based on a capacitor with an overvoltage protection device according to any one of claims 1 to 5, comprising the following steps: Continuously collect the voltage value of the capacitor when the capacitor starts to charge; When the voltage value of the capacitor exceeds a first threshold, the overvoltage protection device is controlled to be activated; Using the overvoltage protection device to consume energy from the capacitor; When the voltage value of the capacitor is lower than the second threshold, the overvoltage protection device is controlled to be cut off, and the overvoltage protection action is completed.

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