A DC energy consumption device based on supercapacitor

Abstract

The present invention relates to a supercapacitor-based DC energy consumption device, which is respectively connected to the positive and negative poles of a DC busbar and comprises a first isolating switch, a second isolating switch, a first DC inductor, a second DC inductor, a first DC current transformer, a second DC current transformer, a plurality of MMC modules, and a plurality of supercapacitor modules. The device can absorb surplus power, maintain voltage stability, and protect equipment when a power grid fault occurs. Furthermore, since the surplus power is stored in the supercapacitor, no large amount of heat is generated, thereby reducing the pressure of heat dissipation. Furthermore, when the DC voltage of the power grid is low, the energy in the supercapacitor can be released to support the DC voltage, thereby contributing to the stability of the power system. The control strategy of the present invention can be used to control the charging current of the supercapacitor submodule, thereby meeting the requirement of fast charging and preventing excessive charging current from burning components.

Description

Technical Field

[0001] The present invention relates to a DC energy consumption device based on a supercapacitor, and belongs to the technical field of flexible DC power transmission. Background Art

[0002] In offshore wind power flexible DC transmission projects, if a fault occurs at the onshore converter station or on the AC side, the offshore wind farm continues to output power, causing the active power input to the DC system to exceed the active power output. This excess power will cause the DC voltage to rise to dangerous levels in a very short time, damaging equipment.

[0003] To address the problem of excess power in DC systems, the traditional approach is to install energy dissipation devices on the DC or AC side of the converter station. For offshore wind power flexible DC transmission projects, installing energy dissipation devices on the AC side of the offshore converter station would increase the size and weight of the converter station, making this solution neither rational nor economical. Therefore, DC energy dissipation devices are typically installed at onshore converter stations. DC energy dissipation devices come in a variety of configurations: centralized, semi-centralized, and distributed. The difference lies in whether the energy dissipation valves and resistors are distributed within the module or centrally located.

[0004] Traditional centralized, semi-centralized, and distributed DC energy dissipation devices are all based on resistors. When the offshore wind power flexible DC transmission system operates normally, the controllable switching device of the energy dissipation valve is locked, the valve bears the entire DC voltage, and the voltage across the energy dissipation resistor is approximately zero. If a fault occurs at the onshore converter station or on the AC side, excess power causes the system DC voltage to rise. Once it exceeds the set value, the controllable switching device of the energy dissipation valve turns on, bypassing the valve. The system DC voltage is directly applied to the energy dissipation resistor, dissipating the excess power through the resistor. Summary of the Invention

[0005] In order to solve the above problems in the prior art, the present invention proposes a DC energy dissipation device based on a supercapacitor.

[0006] The technical solutions of the present invention are as follows:

[0007] The present invention proposes a DC energy consumption device based on supercapacitors, which is connected to the positive and negative poles of the DC bus respectively, and includes a first isolating switch, a second isolating switch, a first DC inductor, a second DC inductor, a first DC current transformer, a second DC current transformer, several MMC modules and several supercapacitor modules;

[0008] The MMC module is used to stabilize voltage, and the supercapacitor module is used to store and release electrical energy;

[0009] One end of the first isolating switch is connected to the positive electrode of the DC bus, the other end of the first isolating switch is connected to one end of a first DC inductor, the other end of the first DC inductor is connected to one end of a first DC current transformer, and the other end of the first DC current transformer is connected to one end of a plurality of MMC modules connected in series;

[0010] The other ends of the plurality of MMC modules connected in series are connected to one end of the plurality of supercapacitor modules connected in series, the other ends of the plurality of supercapacitor modules connected in series are connected to one end of another plurality of MMC modules connected in series, and the other ends of the another plurality of MMC modules connected in series are connected to one end of the second DC current transformer;

[0011] The other end of the second DC current transformer is connected to one end of the second DC inductor, the other end of the second DC inductor is connected to one end of the second isolating switch, and the other end of the second isolating switch is connected to the negative pole of the DC bus.

[0012] As a preferred embodiment of the present invention, the MMC module includes a controllable switch device K1 and a parallel diode D1, a diode D2, a capacitor C, a resistor R, a controllable switch device Ka and a parallel diode thereof;

[0013] One end of the controllable switch device K1 is connected to the input end of the diode D2, the other end of the controllable switch device K1 is respectively connected to one end of the capacitor C and one end of the controllable switch device Ka, the other end of the controllable switch device Ka is connected to one end of the resistor R, and the output end of the diode D2 is respectively connected to the other end of the capacitor C and the other end of the resistor R.

[0014] As a preferred embodiment of the present invention, the supercapacitor module includes a controllable switch device K3 and a parallel diode D3 thereof, a controllable switch device K4 and a parallel diode D4 thereof, an inductor L0 and a supercapacitor SC;

[0015] One end of the controllable switch device K3 is connected to one end of the controllable switch device K4 and one end of the inductor L0 respectively, the other end of the controllable switch device K3 is connected to one end of the super capacitor SC, and the other end of the super capacitor SC is connected to the other end of the inductor L0.

[0016] As a preferred embodiment of the present invention, the other end of the first isolating switch is further connected to one end of the first grounding switch;

[0017] The other end of the second DC inductor is also connected to one end of the second grounding switch.

[0018] As a preferred embodiment of the present invention, the control strategy of the MMC module is:

[0019] Assume the voltage of the MMC module is U mmc The upper limit of the voltage allowed by the MMC module is Ummc_up The lower voltage limit allowed by the MMC module is U mmc_down ;

[0020] Then when U mmc >U mmc_up When , the controllable switch device K1 is closed, and the MMC module capacitor is discharged through the R-Ka loop;

[0021] When U mmc_up ≥U mmc ≥U mmc_down When the controllable switch device K1 remains closed, U mmc Continued decline;

[0022] When U mmc mmc_down When the controllable switch device K1 is disconnected, U mmc Increase or remain unchanged.

[0023] As a preferred embodiment of the present invention, the control strategy of the supercapacitor module is:

[0024] When the controllable switch device K4 is turned on, the current flows through the K4-L0-SC loop to charge the supercapacitor;

[0025] When the controllable switch device K3 is turned on, the supercapacitor SC discharges through the SC-L0-K3 loop. When the controllable switch device K3 is turned off, the current flows to the DC bus through the SC-L0-D4 loop.

[0026] The output voltage of the supercapacitor module is adjusted by controlling the duty cycle of the controllable switch device K3. The calculation formula of the duty cycle α of the switch device is shown in the following formula:

[0027]

[0028] The calculation formula for the output voltage E of the supercapacitor module is:

[0029]

[0030] Among them: U sc Indicates the voltage of the supercapacitor module.

[0031] As a preferred embodiment of the present invention, the steps for selecting the number of supercapacitor modules and MMC modules are as follows:

[0032] Assume that the upper limit of the voltage allowed by the supercapacitor module is U sc_up , the lower limit of the allowed voltage is U sc_down , the number of MMC modules is N mmc , the number of supercapacitor modules is N sc , the DC bus voltage is U dc ​;

[0033] When all MMC modules are in use, the voltage of the supercapacitor module is the lowest:

[0034] N sc ·U sc_down +N mmc ·U mmc =2U dc

[0035] When all MMC modules are disconnected, the DC bus voltage is completely borne by the supercapacitor module, and the supercapacitor module voltage is the highest:

[0036] N sc ·U sc_up =2U dc

[0037] Then the number of supercapacitor modules N sc =2U dc ÷U sc_up , the number of MMC modules is N mmc =(2U dc -N sc ·U sc_down )÷U mmc .

[0038] As a preferred embodiment of the present invention, the total energy value that can be stored in the supercapacitor module is:

[0039] W sc =0.5·C sc ·(U sc_up ·U sc_up -U sc_down ·U sc_down )·N sc

[0040] Where: W sc is the total energy value that can be stored in the supercapacitor module.

[0041] As a preferred embodiment of the present invention, the energy storage control strategy of the device is:

[0042] By cutting out the MMC modules one by one, the supercapacitor modules are charged. Specifically:

[0043] Assume that within the time dT, one MMC module is exited, then N sc The voltage on each supercapacitor module rises by one U mmc , the voltage rise borne by a single supercapacitor module

[0044] By controlling the switching speed of the MMC module, the charging current of the supercapacitor module is controlled. At the same time, the appropriate inductance value L0 of the supercapacitor module is selected according to the voltage-current equation, as shown in the following formula:

[0045]

[0046]

[0047] Where: i(0) represents the initial current value of the supercapacitor module; U sc (0) represents the initial voltage value of the supercapacitor module; C sc It represents the capacitance value of the supercapacitor of the supercapacitor module; i represents the current value of the supercapacitor module.

[0048] As a preferred embodiment of the present invention, the energy consumption control strategy of the device is:

[0049] Control the duty cycle of the controllable switch device K3 of the supercapacitor module and adjust the output voltage of the supercapacitor module. Then N sc The voltage output by the supercapacitor module when When the super capacitor module releases energy to the DC bus, and when The larger it is, the faster the energy is released.

[0050] The present invention has the following beneficial effects:

[0051] 1. The present invention controls DC energy-consuming devices through a control strategy, which can absorb surplus power, maintain voltage stability, and protect equipment when a power grid fails. Moreover, since the surplus power is stored in the supercapacitor, no large amount of heat is generated, which reduces the pressure of heat dissipation. Moreover, when the DC voltage of the power grid is low, the energy in the supercapacitor can be released to support the DC voltage, which helps to stabilize the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a topological diagram of the device of the present invention. DETAILED DESCRIPTION

[0053] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] It should be understood that the step numbers used herein are only for convenience of description and are not intended to limit the order in which the steps are to be executed.

[0055] It should be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0056] The terms “include” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0057] The term "and / or" refers to and includes any and all possible combinations of one or more of the associated listed items.

[0058] Example 1:

[0059] See also Figure 1 , a DC energy consumption device based on supercapacitor, connected to the positive and negative poles of the DC bus respectively, the bus voltage is +U dc 、-U dc , including a first isolating switch DS, a second isolating switch DS, a first DC inductor L, a second DC inductor L, a first DC current transformer CT, a second DC current transformer CT, a plurality of MMC modules SM and a plurality of supercapacitor modules SM;

[0060] One end of the first isolating switch is connected to the positive electrode of the DC bus, the other end of the first isolating switch is connected to one end of a first DC inductor, the other end of the first DC inductor is connected to one end of a first DC current transformer, and the other end of the first DC current transformer is connected to one end of a plurality of MMC modules connected in series;

[0061] The other ends of the plurality of MMC modules connected in series are connected to one end of the plurality of supercapacitor modules connected in series, the other ends of the plurality of supercapacitor modules connected in series are connected to one end of another plurality of MMC modules connected in series, and the other ends of the another plurality of MMC modules connected in series are connected to one end of the second DC current transformer;

[0062] The other end of the second DC current transformer is connected to one end of the second DC inductor, the other end of the second DC inductor is connected to one end of the second isolating switch, and the other end of the second isolating switch is connected to the negative pole of the DC bus.

[0063] The isolating switch DS is used to disconnect the DC energy consumption device from the DC bus, forming a clear break;

[0064] The DC inductor L is used to reduce the inrush current during charging and discharging of the DC energy consuming device;

[0065] The DC current transformer CT is used to measure the current of the device;

[0066] The MMC module is used to provide a stable voltage;

[0067] The supercapacitor module is used for storing and releasing electric energy and is the core energy storage component.

[0068] As a preferred implementation of this embodiment, the other end of the first isolating switch DS is further connected to one end of the first grounding switch ES;

[0069] The other end of the second DC inductor L is also connected to one end of the second grounding switch ES.

[0070] As a preferred implementation of this embodiment, the MMC module includes a controllable switch device K1 and its parallel diode D1, a diode D2, a capacitor C, a resistor R, a controllable switch device Ka and its parallel diode;

[0071] One end of the controllable switch device K1 is connected to the input end of the diode D2, the other end of the controllable switch device K1 is respectively connected to one end of the capacitor C and one end of the controllable switch device Ka, the other end of the controllable switch device Ka is connected to one end of the resistor R, and the output end of the diode D2 is respectively connected to the other end of the capacitor C and the other end of the resistor R.

[0072] In this embodiment, a control strategy of the MMC module is set to stabilize the voltage of the MMC module, specifically:

[0073] Assume the voltage of the MMC module is U mmc The upper limit of the voltage allowed by the MMC module is U mmc_up The lower voltage limit allowed by the MMC module is U mmc_down ;

[0074] Then when U mmc >U mmc_up When , the controllable switch device K1 is closed, and the MMC module capacitor is discharged through the R-Ka loop;

[0075] When U mmc_up ≥U mmc ≥U mmc_doqn When the controllable switch device K1 remains closed, U mmc Continued decline;

[0076] When U mmc mmc_down When the controllable switch device K1 is disconnected, U mmc Increase or remain unchanged;

[0077] ​In order to avoid frequent operation of the controllable switch device Ka, a hysteresis control link is set, and the controllable switch device Ka does not operate in the dead zone of the hysteresis control;

[0078] Under this control strategy, U mmc in U mmc_up to U mmc_down The voltage of the MMC module fluctuates within a certain range, so it can be considered that the voltage of the MMC module maintains a constant value U mmc .

[0079] As a preferred embodiment of this embodiment, the supercapacitor module includes a controllable switch device K3 and a parallel diode D3 thereof, a controllable switch device K4 and a parallel diode D4 thereof, an inductor L0 and a supercapacitor SC, and the capacitance value of the supercapacitor SC is in the Farad level;

[0080] One end of the controllable switch device K3 is connected to one end of the controllable switch device K4 and one end of the inductor L0 respectively, the other end of the controllable switch device K3 is connected to one end of the supercapacitor SC, and the other end of the supercapacitor SC is connected to the other end of the inductor L0;

[0081] In this embodiment, the control strategy of the supercapacitor module is set:

[0082] When the controllable switch device K4 is turned on, the current flows through the K4-L0-SC loop to charge the supercapacitor;

[0083] When the controllable switch device K3 is turned on, the supercapacitor SC discharges through the SC-L0-K3 loop. When the controllable switch device K3 is turned off, since the inductor current of L0 cannot change suddenly, the current flows to the DC bus through the SC-L0-D4 loop;

[0084] By controlling the duty cycle of the controllable switch device K3, that is, the on-time of the controllable switch device K3 / (on-time + off-time), the output voltage of the supercapacitor module can be adjusted. Assuming that α is the duty cycle of the controllable switch device K3, the output voltage of a single supercapacitor submodule is

[0085] In this embodiment, a method for selecting the number of supercapacitor modules and MMC modules is proposed, and the specific steps are as follows:

[0086] Assume that the upper limit of the voltage allowed by the supercapacitor module is U sc_up , the lower limit of the allowed voltage is U sc_down , the number of MMC modules is N mmc , the number of supercapacitor modules is N sc , the DC bus voltage is U dc ;

[0087] When all MMC modules are in use, the voltage of the supercapacitor module is the lowest:

[0088] N sc ·U sc_down +N mmc ·U mmc =2U dc

[0089] When all MMC modules are disconnected, the DC bus voltage is completely borne by the supercapacitor module, and the supercapacitor module voltage is the highest:

[0090] N sc ·U sc_up =2U dc

[0091] Then the number of supercapacitor modules N sc =2U dc ÷U sc_up , the number of MMC modules is N mmc =(2U dc -N sc ·U sc_down )÷U mmc ;

[0092] The total energy value W that the supercapacitor module can store sc for:

[0093] W sc =0.5·C sc ·(U sc_up ·U sc_up -U sc_down ·U sc_down )·N sc

[0094] The energy storage control strategy of the DC energy consumption device is:

[0095] To avoid the simultaneous exit of MMC modules, which would cause a sudden and substantial increase in the DC bus voltage borne by the supercapacitor module, leading to an accident in which the high charging current burns out the components, this embodiment proposes a strategy for exiting the MMC modules one by one, specifically:

[0096] When the MMC module exits, the bus voltage borne by the supercapacitor module increases and the supercapacitor module is charged;

[0097] Assume that within dT time, one MMC module is exited, then N sc The voltage on each supercapacitor module rises by one U mmc , the voltage rise U borne by a single supercapacitor module mmc ÷N sc ;

[0098] By controlling the switching speed of the MMC module, the charging current of the supercapacitor module can be controlled. In order to protect the supercapacitor submodule and avoid excessive charging current from burning components, the inductance value L0 of the supercapacitor module can be selected appropriately. According to the voltage-current equation, it can be obtained:

[0099]

[0100] U sc Around the initial value U sc (0) Fluctuates up and down, first increases and then decreases. In order to achieve the effect of rapid energy storage, the cut-out time dT of the MMC module should not be greater than U sc Oscillation cycle

[0101]

[0102]

[0103] The energy consumption control strategy of the DC energy consumption device is:

[0104] By controlling the duty cycle of the controllable switch device K3 of the supercapacitor module, the output voltage of the supercapacitor module is adjusted; then N sc The output voltage of each supercapacitor module is when When the supercapacitor module releases energy to the DC bus, The larger it is, the faster it releases.

[0105] In the embodiments of the present application, "at least one" refers to one or more, and "more" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can represent: a, b, c, a and b, a and c, b and c or a and b and c, where a, b, c can be single or multiple.

[0106] Those skilled in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented using a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0107] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0108] In the several embodiments provided in this application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of this application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), magnetic disk or optical disk, and other media that can store program code.

[0109] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A DC energy consumption device based on a supercapacitor, connected to the positive and negative poles of a DC bus, characterized in that: It includes a first isolating switch, a second isolating switch, a first DC inductor, a second DC inductor, a first DC current transformer, a second DC current transformer, several MMC modules and several supercapacitor modules; The MMC module is used to stabilize voltage, and the supercapacitor module is used to store and release electrical energy; One end of the first isolating switch is connected to the positive electrode of the DC bus, the other end of the first isolating switch is connected to one end of a first DC inductor, the other end of the first DC inductor is connected to one end of a first DC current transformer, and the other end of the first DC current transformer is connected to one end of a plurality of MMC modules connected in series; The other ends of the plurality of MMC modules connected in series are connected to one end of the plurality of supercapacitor modules connected in series, the other ends of the plurality of supercapacitor modules connected in series are connected to one end of another plurality of MMC modules connected in series, and the other ends of the another plurality of MMC modules connected in series are connected to one end of the second DC current transformer; The other end of the second DC current transformer is connected to one end of the second DC inductor, the other end of the second DC inductor is connected to one end of the second isolating switch, and the other end of the second isolating switch is connected to the negative pole of the DC bus.

2. A supercapacitor-based DC energy consumption device according to claim 1, characterized in that: The MMC module includes a controllable switch device K1 and a parallel diode D1, a diode D2, a capacitor C, a resistor R, a controllable switch device Ka and a parallel diode; One end of the controllable switch device K1 is connected to the input end of the diode D2, the other end of the controllable switch device K1 is respectively connected to one end of the capacitor C and one end of the controllable switch device Ka, the other end of the controllable switch device Ka is connected to one end of the resistor R, and the output end of the diode D2 is respectively connected to the other end of the capacitor C and the other end of the resistor R.

3. A supercapacitor-based DC energy consumption device according to claim 1, characterized in that: The supercapacitor module includes a controllable switch device K3 and a parallel diode D3 thereof, a controllable switch device K4 and a parallel diode D4 thereof, an inductor L0 and a supercapacitor SC; One end of the controllable switch device K3 is connected to one end of the controllable switch device K4 and one end of the inductor L0 respectively, the other end of the controllable switch device K3 is connected to one end of the super capacitor SC, and the other end of the super capacitor SC is connected to the other end of the inductor L0.

4. A supercapacitor-based DC energy consumption device according to claim 1, characterized in that: The other end of the first isolating switch is also connected to one end of the first grounding switch; The other end of the second DC inductor is also connected to one end of the second grounding switch.

5. The supercapacitor-based DC energy consumption device according to claim 2, characterized in that: The control strategy of the MMC module is: Assume the voltage of the MMC module is U mmc The upper limit of the voltage allowed by the MMC module is U mmc_up The lower voltage limit allowed by the MMC module is U mmc_down ; Then when U mmc >U mmc_up When , the controllable switch device K1 is closed, and the MMC module capacitor is discharged through the R-Ka loop; When U mmc_up ≥U mmc ≥U mmc_down When the controllable switch device K1 remains closed, U mmc Continued decline; When U mmc mmc_down When the controllable switch device K1 is disconnected, U mmc Increase or remain unchanged.​ 6. A supercapacitor-based DC energy consumption device according to claim 5, characterized in that: The control strategy of the supercapacitor module is: When the controllable switch device K4 is turned on, the current flows through the K4-L0-SC loop to charge the supercapacitor; When the controllable switch device K3 is turned on, the supercapacitor SC discharges through the SC-L0-K3 loop. When the controllable switch device K3 is turned off, the current flows to the DC bus through the SC-L0-D4 loop. The output voltage of the supercapacitor module is adjusted by controlling the duty cycle of the controllable switch device K3. The calculation formula of the duty cycle α of the switch device is shown in the following formula: The calculation formula for the output voltage E of the supercapacitor module is: Among them: U sc Indicates the voltage of the supercapacitor module.

7. A supercapacitor-based DC energy consumption device according to claim 6, characterized in that: The steps for selecting the number of supercapacitor modules and MMC modules are as follows: Assume that the upper limit of the voltage allowed by the supercapacitor module is U sc_up , the lower limit of the allowed voltage is U sc_down , the number of MMC modules is N mmc , the number of supercapacitor modules is N sc , the DC bus voltage is U dc ; When all MMC modules are in use, the voltage of the supercapacitor module is the lowest: N sc ·U sc_down +N mmc ·U mmc =2U dc When all MMC modules are disconnected, the DC bus voltage is completely borne by the supercapacitor module, and the supercapacitor module voltage is the highest: N sc ·U sc_up =2U dc Then the number of supercapacitor modules N sc =2U dc ÷U sc_up , the number of MMC modules is N mmc =(2U dc -N sc ·U sc_down )÷U mmc .

8. The supercapacitor-based DC energy consumption device according to claim 7, characterized in that: The total energy that can be stored in the supercapacitor module is: W sc =0.5·C sc ·(U sc_up ·U sc_up -U sc_down ·U sc_down )·N sc Where: W sc is the total energy value that can be stored in the supercapacitor module; C sc Indicates the capacitance value of the supercapacitor in the supercapacitor module.

9. The supercapacitor-based DC energy consumption device according to claim 7, characterized in that: The energy storage control strategy of the device is: By cutting out the MMC modules one by one, the supercapacitor modules are charged. Specifically: Assume that within the time dT, one MMC module is exited, then N sc The voltage on each supercapacitor module rises by one U mmc , the voltage rise borne by a single supercapacitor module By controlling the switching speed of the MMC module, the charging current of the supercapacitor module is controlled. At the same time, the appropriate inductance value L0 of the supercapacitor module is selected according to the voltage-current equation, as shown in the following formula: i(0)＝0 Where: i(0) represents the initial current value of the supercapacitor module; U sc (0) represents the initial voltage value of the supercapacitor module; C sc It represents the capacitance value of the supercapacitor of the supercapacitor module; i represents the current value of the supercapacitor module.

10. The supercapacitor-based DC energy consumption device according to claim 7, characterized in that: The energy consumption control strategy of the device is: Control the duty cycle of the controllable switch device K3 of the supercapacitor module and adjust the output voltage of the supercapacitor module. Then N sc The voltage output by the supercapacitor module when When the super capacitor module releases energy to the DC bus, and when The larger it is, the faster the energy is released.

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