Hybrid supercapacitor energy storage type current converter based on H bridge and operation method of hybrid supercapacitor energy storage type current converter

Abstract

The invention relates to a hybrid supercapacitor energy storage type converter based on an H bridge and an operation method thereof, and the energy storage type converter comprises an upper bridge arm part and a lower bridge arm part. Each of the upper bridge arm part and the lower bridge arm part comprises three bridge arms, and each bridge arm is formed by connecting n H-bridge sub-modules and a bridge arm inductor in series; the upper bridge arm part is connected with a direct current bus, and the lower bridge arm part is connected with a grounding wire; the H-bridge sub-module comprises four switch elements and an energy storage unit, the energy storage unit is a hybrid super capacitor, the four switch elements form an H-bridge structure, and the hybrid super capacitor is connected to the two ends of the H-bridge structure in parallel. According to the invention, the dual functions of energy storage and current conversion in the AC-DC interconnected power grid can be realized under the cooperation of the control strategy, and various operation requirements in different scenes can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of converter topology and medium voltage direct current power distribution, and in particular to a hybrid supercapacitor energy storage converter based on an H-bridge and an operating method thereof. Background Art

[0002] Affected by the natural environment, the output of renewable energy is often characterized by volatility, intermittency and unpredictability. The interaction between distributed renewable energy and the power grid is undertaken by the AC / DC hybrid microgrid. The interconnected converter is one of the key devices in the AC / DC hybrid microgrid, which is used to achieve bidirectional power flow regulation and control between subgrids. The energy storage interconnected converter has the ability to provide active and passive power. Under grid-connected, off-grid and on / off-grid switching conditions, it can flexibly respond to changes in the operating mode of the AC / DC grid, and has high power supply reliability for AC / DC loads.

[0003] The AC / DC interconnected converter is an important component of the AC / DC hybrid microgrid, which can realize the bidirectional power flow control between the AC subgrid and the DC subgrid. As one of the AC / DC interconnected converters, the PCS (Power conversion system) topology mostly uses diode clamped multilevel converters, cascaded H-bridge converters and half-bridge modular multilevel converters. Combining energy storage technology with conversion technology can increase the reusability of equipment and play the dual role of energy storage and conversion. At present, the combination of energy storage unit and cascaded H-bridge converter is widely used. The energy storage unit is dispersed in the cascaded H-bridge submodule, which is not only convenient for realizing medium and high voltage level active power reserve, but also conducive to the stability of submodule capacitor voltage and increases the safety of the device; at the same time, compared with centralized energy storage, it can reduce additional devices and reduce the footprint of the device; at the same time, the combination of modular multilevel converter and energy storage unit can save the transformer and directly connect to the medium and high voltage power grid, reduce costs, make the system structure simpler and more compact, improve system reliability and easy maintenance. However, due to the use of the H-bridge cascade mode, the three-phase bridge arms often adopt star or delta wiring, lack of DC bus, and easily lead to neutral point offset, which not only affects the normal operation of the equipment, but also brings difficulties to the control system design. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a hybrid supercapacitor energy storage converter based on an H-bridge and an operating method thereof, which can realize the dual functions of energy storage and current conversion in an AC / DC interconnected power grid under the cooperation of a control strategy, and meet various operating requirements in different scenarios.

[0005] The technical solution adopted by the present invention to solve its technical problems is: to provide a hybrid supercapacitor energy storage converter based on an H-bridge, including an upper bridge arm part and a lower bridge arm part; the upper bridge arm part and the lower bridge arm part each include three bridge arms, each bridge arm is composed of n H-bridge sub-modules and a bridge arm inductor connected in series; the upper bridge arm part is connected to a DC bus, and the lower bridge arm part is connected to a ground wire; the H-bridge sub-module includes four switching elements and an energy storage unit, and the energy storage unit is a hybrid supercapacitor; the four switching elements constitute an H-bridge structure, and the hybrid supercapacitor is connected in parallel at both ends of the H-bridge structure.

[0006] The energy storage unit may also be a lithium battery or a storage battery.

[0007] Capacitors are also connected in parallel at both ends of the energy storage unit.

[0008] The technical solution adopted by the present invention to solve its technical problem is: to provide an operating method of the above-mentioned H-bridge-based hybrid supercapacitor energy storage converter, including: connecting the three bridge arms of the upper bridge arm part and the three bridge arms of the lower bridge arm part in the H-bridge-based energy storage converter to the AC power grid, and connecting the DC bus of the H-bridge-based energy storage converter to the DC power grid; when the power performance in the AC power grid or the DC power grid is insufficient, the hybrid supercapacitor transfers energy from the H-bridge-based energy storage converter to the AC power grid or the DC power grid through a control strategy; when the power of the AC power grid or the DC power grid is sufficient, the excess energy is stored in the hybrid supercapacitor through the H-bridge-based energy storage converter.

[0009] The H-bridge based energy storage converter adopts a constant DC voltage control strategy, which means that the voltage on the DC side of the H-bridge based energy storage converter is a constant value, and the active power transmitted between the H-bridge based energy storage converter and the AC power grid is determined by external operating conditions.

[0010] When a fault occurs on the DC side of the H-bridge based energy storage converter, the bipolar level output capability of the H-bridge submodule is utilized to adjust the voltage on the DC side and actively disconnect the DC grid; the upper bridge arm part and the lower bridge arm part in the H-bridge based energy storage converter operate in parallel and serve as backup for each other.

[0011] The H-bridge-based energy storage converter adopts a constant power control strategy, which means that the active power and reactive power transmitted between the H-bridge-based energy storage converter and the AC power grid interact according to given instructions to achieve tracking control of power transmission; the H-bridge submodule adopts a constant voltage control strategy or a droop control strategy.

[0012] The operating method also includes: when a fault occurs on the AC side of the H-bridge-based energy storage converter, the H-bridge-based energy storage converter is converted to a DC / DC operating mode, and a bridge arm is put into use to support the DC bus voltage. When put into use, the three bridge arms of the upper bridge arm part are alternately put into use or the three bridge arms of the lower bridge arm part are alternately put into use.

[0013] The operating method also includes: when a fault occurs on both the AC side and the DC side of the H-bridge based energy storage converter, the H-bridge based energy storage converter disconnects the DC grid and the AC grid, and operates in V / F mode to provide voltage and frequency support for the AC load, or operates in DC / DC mode to stabilize the DC voltage and provide energy supply for the DC load.

[0014] When the H-bridge based energy storage converter operates in the V / F mode, the output voltage frequency of the power electronic device is adjusted by droop control simulating the droop characteristic curve of the synchronous generator.

[0015] Beneficial Effects

[0016] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages and positive effects compared with the prior art: the present invention adopts a full-bridge MMC energy storage converter topology. Compared with other power converters, MMC has the advantages of good capacity and voltage level scalability, low output current harmonic content, flexible control and application, etc., and MMC has a DC bus and can directly interact with the DC power grid for energy. The neutron module of the present invention adopts a full-bridge structure, has multiple operating modes and bipolar level output capabilities, and can directly cross the DC fault when a fault occurs on the DC side, thereby isolating the DC power grid; the H-bridge-based energy storage converter topology structure of the present invention can operate the upper and lower bridge arms jointly or independently in parallel, and serve as backup for each other, thereby reducing equipment loss and the number of times the hybrid supercapacitor is charged and discharged, and increasing the life of the equipment; hybrid supercapacitors, lithium batteries, batteries and other energy storage units can be conveniently connected to the MMC submodule to form an energy storage MMC with multiple types of storage media; the energy storage MMC structure can make full use of its modular structural characteristics, and increase the output AC and DC voltages of the energy storage system through sub-module expansion, realize direct grid connection of the energy storage system, and save transformer cost investment; under the cooperation of different control strategies, double-end networking operation, single-end networking operation, and island operation modes are realized, providing higher power supply reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the topological structure of an energy storage converter based on an H-bridge according to an embodiment of the present invention;

[0018] Figure 2 Schematic diagram of AC / DC power grid interconnection topology of an H-bridge energy storage converter in an embodiment of the present invention;

[0019] Figure 3 1 is a schematic diagram of the topology of the upper and lower bridge arms independently operating in the H-bridge based energy storage converter according to an embodiment of the present invention;

[0020] Figure 4 It is a block diagram of a constant DC voltage control in an embodiment of the present invention;

[0021] Figure 5 is a schematic diagram of system topology when a DC side fault occurs in an embodiment of the present invention;

[0022] Figure 6 is a schematic diagram of system topology in an AC power grid operation mode in an embodiment of the present invention;

[0023] Figure 7 is a constant power control block diagram in an embodiment of the present invention;

[0024] Figure 8 is a schematic diagram of system topology when an AC side fault occurs in an embodiment of the present invention;

[0025] Fig. 9 is a schematic diagram of system topology in a DC power grid operation mode in an embodiment of the present invention;

[0026] Fig.10 is a schematic diagram of the system topology when both the AC and DC sides fail in an embodiment of the present invention;

[0027] Fig.11 Schematic diagram of system topology in isolated network operation mode in an embodiment of the present invention;

[0028] Fig.12 is a topological diagram of the cascaded H-bridge operation mode in an embodiment of the present invention;

[0029] Fig.13 It is a block diagram of a constant voltage control strategy in an embodiment of the present invention;

[0030] Fig.14 is a droop control block diagram in an embodiment of the present invention;

[0031] Fig.15 is a simulation waveform diagram in an embodiment of the present invention;

[0032] Fig.16 It is a waveform diagram of grid frequency change when grid load suddenly increases in an implementation manner of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0034] The embodiment of the present invention relates to a hybrid supercapacitor energy storage converter based on an H-bridge, such as Figure 1 As shown, it includes an upper bridge arm part and a lower bridge arm part; the upper bridge arm part and the lower bridge arm part each include three bridge arms, each bridge arm is composed of n H bridge submodules and a bridge arm inductor connected in series; the upper bridge arm part is connected to the DC bus, and the lower bridge arm part is connected to the ground wire; the H bridge submodule includes four switching elements and an energy storage unit, the energy storage unit is a hybrid supercapacitor, the four switching elements form an H bridge structure, and the hybrid supercapacitor is connected in parallel at both ends of the H bridge structure. Among them, the energy storage unit is a hybrid supercapacitor, which is also suitable for lithium batteries or batteries.

[0035] like Figure 1 As shown, the energy storage unit in this embodiment adopts a hybrid supercapacitor. A hybrid supercapacitor is a device that has the characteristics of a double-layer supercapacitor and a battery. Its unique structure and material properties have many significant advantages. First, the hybrid supercapacitor has a high energy density and is suitable for applications that require high energy storage. Secondly, its power density is also very high, and it can release a large amount of electrical energy in a short period of time, which is suitable for occasions that require fast response and high power output. The hybrid supercapacitor has extremely high charging and discharging efficiency, and can almost achieve lossless energy conversion. Its service life is also very long. Compared with traditional batteries, hybrid supercapacitors can undergo more charge and discharge cycles without significantly reducing their performance.

[0036] The way to connect the hybrid supercapacitor to the H-bridge based energy storage converter is generally divided into centralized energy storage and distributed energy storage. Distributed energy storage is widely used due to its high controllability. Once a fault occurs, the H-bridge based energy storage converter can choose to cut it off. In this embodiment, the hybrid supercapacitor can be connected directly, that is, replacing the capacitor in the H-bridge submodule or connecting it in parallel with the capacitor in the H-bridge submodule.

[0037] In order to illustrate the technical advantages and characteristics of the H-bridge based energy storage converter in this embodiment, it is applied to the AC / DC grid interconnection system and a Figure 2The AC / DC grid interconnection topology shown in the figure. When applied, the three bridge arms of the upper bridge arm part and the three bridge arms of the lower bridge arm part of the H-bridge based energy storage converter are connected to the AC grid, and the DC bus of the H-bridge based energy storage converter is connected to the DC grid.

[0038] The H-bridge based energy storage converter of this embodiment has the characteristics of flexible change, and can realize multiple operation modes to adapt to the application scenarios and diversified working conditions of AC and DC grid interconnection. The multiple operation modes include: double-end interconnection operation mode, AC interconnection operation mode, DC interconnection operation mode and island operation mode. In the AC interconnection operation mode, the H-bridge based energy storage converter can operate the upper and lower bridge arms independently, such as Figure 3 As shown. According to the actual application scenario conditions and requirements, the H-bridge-based energy storage converter can achieve energy caching, voltage support, and primary frequency and voltage regulation and other functional requirements. By designing the corresponding control strategy, the flexible change advantage of the H-bridge-based energy storage converter operation mode can be brought into play to meet the multi-operating conditions of the actual application scenario.

[0039] Dual-end networking operation mode, such as Figure 2 As shown, the H-bridge-based energy storage converter can simultaneously connect and support the AC grid and the DC grid, play a dual role of energy storage and current conversion, and perform bidirectional energy transfer between the AC grid and the DC grid, and between the hybrid supercapacitor and the grid. When the power performance in the AC grid or the DC grid is insufficient, the hybrid supercapacitor transfers energy from the H-bridge-based energy storage converter to the AC grid or the DC grid through a control strategy; when the power of the AC grid or the DC grid is sufficient, the excess energy is stored in the hybrid supercapacitor through the H-bridge-based energy storage converter, thereby improving energy utilization. At the same time, it can feed or absorb reactive power to the grid, providing functions such as power factor compensation and voltage support.

[0040] In the double-terminal networking operation mode, the H-bridge based energy storage converter mainly plays the role of energy transfer, so a constant DC voltage control strategy can be adopted. Figure 4 ) means that the voltage on the DC side of the H-bridge based energy storage converter is a constant, and the active power transmitted between the H-bridge based energy storage converter and the AC power grid is determined by the external operating conditions, so that the bidirectional changes of the energy flow can be adaptively changed.

[0041] When a fault occurs on the DC side of the H-bridge based energy storage converter (see Figure 5 ), the AC networking operation mode can be adopted. Figure 6As shown, in this mode, the bipolar level output capability of the H-bridge submodule can be used to quickly adjust the DC side voltage, perform active DC fault isolation, and disconnect the DC grid. Since the DC bus voltage is not required at this time, the operating topology is flexible, and the cascade H-bridge mode can be adopted. At this time, the upper bridge arm part and the lower bridge arm part of the H-bridge-based energy storage converter run in parallel and serve as backup for each other. The H-bridge-based energy storage converter can continue to play a primary regulation role on the AC grid to ensure the stability of the AC load voltage and frequency.

[0042] In AC grid operation mode, a constant power control strategy can be adopted (see Figure 7 ), the constant power control strategy refers to the interaction of the active power and reactive power transmitted between the H-bridge-based energy storage converter and the AC power grid according to given instructions, which can realize the tracking control of power transmission. The H-bridge submodule can adopt a constant voltage control strategy to stabilize the load side voltage, or a droop control strategy to provide frequency support to ensure the power quality of the AC load.

[0043] When a fault occurs on the AC side of the H-bridge based energy storage converter (see Figure 8 ), the DC interconnection operation mode can be adopted, and its topology is as follows Fig. 9 As shown. At this time, the H-bridge-based energy storage converter is converted to the DC / DC operation mode, and plays an energy storage role in the DC power grid to cope with charging during the DC power load valley, and discharge during the power peak to reduce the impact of the load peak on the power grid, and meet the bidirectional conversion requirements brought by the "charging + discharging" of the energy storage system. Since the AC current is zero, in order to reduce the number of charge and discharge times of the energy storage element and improve the operating life, at the same time, the H-bridge-based energy storage converter can also put into use a bridge arm to support the DC bus voltage. When put into use, the three bridge arms of the upper bridge arm part are put into use alternately or the three bridge arms of the lower bridge arm part are put into use alternately. A fixed DC voltage control strategy can be adopted in the DC interconnection operation mode.

[0044] When both the AC side and the DC side of the H-bridge based energy storage converter fail (see Fig.10 ), the H-bridge based energy storage converter disconnects the DC grid and the AC grid and enters the isolated grid operation mode. The system topology in the isolated grid operation mode is as follows: Fig.11 As shown, the H-bridge based energy storage converter can choose to form an AC isolated grid or a DC isolated grid with an AC load or a DC load. At this time, the H-bridge based energy storage converter can operate in V / F mode to provide voltage and frequency support for the AC load, or it can operate in DC / DC mode to stabilize the DC voltage and provide energy supply for the DC load. When in the AC island operation mode, the H-bridge based energy storage converter can adjust the output voltage and frequency of the power electronic equipment by droop control to simulate the droop characteristic curve of the synchronous generator.

[0045] The output characteristics of the H-bridge based energy storage converter are described below using the AC grid operation mode as an example.

[0046] When a fault occurs on the DC side, the DC grid is isolated and operates in the AC grid operation mode. In this embodiment, when the DC load is disconnected, the energy storage MMC can be used for energy storage and current conversion to supply power to part of the DC load. In order to reduce equipment losses and the number of times the hybrid supercapacitor is charged and discharged, and to increase equipment life, the H-bridge-based energy storage converter can also operate in parallel with the upper and lower bridge arms, serving as backup for each other, and operating in the cascade H-bridge mode. This is equivalent to the upper and lower cascade H-bridges running in parallel. If the demand is met, only one cascade H-bridge can be operated. Fig.12 Where L1 is the equivalent inductance of the AC power system, L2 is the connection inductance, and U G ,I G is the effective value of the grid-side voltage and current; U L ,I L is the effective value of voltage and current on the load side; U C ,I C is the effective value of the output voltage and current.

[0047] In the system, the AC power supply and the load are connected through an AC system equivalent inductor, the cascaded H-bridge is connected in parallel with the load, and each phase is composed of multiple cascaded power modules. Each power module includes an H-bridge and a hybrid supercapacitor connected in parallel with a capacitor.

[0048] In normal operation, the active and reactive power outputs of the cascaded H-bridge energy storage system are both 0. At this time, the active and reactive power required by the load are provided by the AC power grid. The power grid outputs active power P G 、Reactive power Q G They are:

[0049]

[0050] Where X1 is the reactance value of L1, and δ is the phase difference between the grid voltage and the load voltage. Taking phase A as an example, the system voltage satisfies the following relationship during normal operation:

[0051]

[0052] where u G 、u G is the instantaneous value of phase A voltage and current, u L is the instantaneous value of phase A voltage on the load side, u C 、u C is the instantaneous value of the output voltage and current of phase A of the cascaded H-bridge energy storage system. L and i G 、i C The relationship is:

[0053] i L =i G -i C (3)

[0054] From formula (2) and formula (3), we can get:

[0055]

[0056] It can be seen from formula (4) that when there is a problem with the AC power supply, the voltage quality on the load side may be affected and thus fail to meet the demand. By changing formula (4), we can get:

[0057]

[0058] The biggest feature of hybrid supercapacitor energy storage frequency regulation is that it can use its ultra-high power density to achieve short-term high-power output and storage. Droop control gradually restores the system frequency to the rated value by adjusting the active power output of the energy storage system. When the system frequency is lower than the rated value, the energy storage system increases the active power output; when the system frequency is higher than the rated value, the energy storage system reduces the active power output or absorbs the excess active power of the system to maintain the system frequency balance.

[0059] 1) Constant voltage control

[0060] The main purpose is to stabilize the voltage on the load side. When the voltage on the grid side fluctuates greatly, the system can still provide a relatively stable voltage for the load side. In order to continuously output a stable voltage to the load side, the system collects the three-phase voltage value and the output current of the cascaded H-bridge energy storage system in real time. By transforming equation (4), we can get:

[0061]

[0062] It can be seen from formula (6) that there is an inductive coupling phase between the dq axes, and the dq axes cannot be adjusted independently. It is necessary to add a decoupling term in the control link. According to formula (6), the control strategy is designed as follows: Fig.13 shown.

[0063] 2) Droop control

[0064] There is an approximately linear relationship between the output active power and frequency, and the reactive power and voltage amplitude of the synchronous generator, which is the droop characteristic.

[0065] The P / f and Q / U droop characteristics show that when the output active power increases, the output frequency decreases; when the output reactive power increases, the output voltage amplitude decreases. Droop control is to use the frequency and voltage droop curves similar to those of traditional generators to obtain stable frequency and voltage through P / f droop control and Q / U droop control. Referring to the droop characteristics of traditional generators, the droop characteristic equations of the inverter output voltage frequency and amplitude can be obtained as follows:

[0066]

[0067] In formula (7), ω0 and U0 are the given reference angular frequency and voltage respectively, P0 and Q0 are the reference active power and reactive power respectively, K p and K q are the P / f droop coefficient and Q / U droop coefficient of the inverter respectively. ω, U, P, Q are the output angular frequency, voltage, active power and reactive power of the converter. The output active power and frequency are linearly related.

[0068] The specific process of droop control uses the active power and reactive power in the system at this time to compare with the reference power value, and multiplies the power difference with the droop coefficient to obtain the angular frequency and voltage value that the system should change at this time, and add it with the system rated angular frequency and system reference voltage U0 to obtain the actual output angular frequency and voltage value, and perform time integration of the angular frequency and synthesize it with the voltage value to obtain the three-phase voltage reference value that the system should output. Then input it into the double closed-loop system to obtain the PWM waveform of the drive signal corresponding to the power device that should be output. Its control block diagram is as follows Fig.14 shown.

[0069] In order to verify the feasibility and effectiveness of this implementation, a system simulation model was built using PSCAD / EMTDC simulation software. The system rated line voltage is 35kV effective value, rated frequency is 50Hz, and the simulation simulates the voltage sag and load surge of the power grid to verify that the topology can flexibly operate in the energy storage cascade H-bridge structure. The energy storage unit uses a hybrid supercapacitor, which can provide voltage support, participate in primary frequency regulation, and ensure good power quality of the load.

[0070] In the case of grid voltage sag, the following simulation conditions are designed: in normal working state, the energy storage system does not output active and reactive power. In the first case, the grid voltage drops to 0.1pu at 1.8s, that is, the effective value of the line voltage drops to 3.5kV, and the voltage drops for 0.3s. After 0.3s, the grid voltage returns to normal working condition. At this time, the simulation waveform is as follows Fig.15 As shown; Fig.15 (a) is the grid-side phase voltage waveform. It can be seen that the voltage drops sharply to 0.1pu at 1.8s, but the load-side voltage does not change significantly. The phase voltage waveform is as follows: Fig.15 As shown in (b) in Fig.15 In (c), it can be seen that the effective value of the load-side voltage fluctuates slightly at 1.8s and 2.1s. It can be seen that the energy storage system can support the load-side voltage to maintain voltage stability. Fig.15(d) is the active and reactive power output of the energy storage system during the entire period. It can be seen that under normal operating conditions, the active and reactive power output of the energy storage system is basically 0. When the grid-side voltage drops sharply, the energy storage system outputs about 16MW of active power and about 52Mvar of reactive power.

[0071] In view of the sudden increase in grid load, the following simulation conditions are designed: the rated grid frequency is 50Hz. In normal working state, the H-bridge based energy storage converter is not connected to the grid. At 2s, the grid suddenly increases the load of 2WM. At this time, the grid frequency drops to 49.4Hz. At 3s, the energy storage system is connected and the grid frequency returns to the rated frequency (see Fig.16 ). After adding energy storage, the maximum frequency deviation of the system subjected to disturbances was reduced from 0.602Hz to 0.0048Hz, and the steady-state frequency deviation was reduced from 0.6Hz to 0.0045Hz, stabilizing at the rated value of 50Hz.

[0072] In the AC interconnected operation mode, the H-bridge-based energy storage converter operates flexibly and can isolate the DC grid in the event of a DC side fault. When operating in the cascaded H-bridge mode, the cascaded H-bridge energy storage system can provide voltage support in the event of a temporary drop in grid voltage, and can participate in primary frequency modulation in the event of a sudden load increase, so that the load-side voltage and grid frequency are in a stable state, ensuring continuous and reliable power supply to the load.

[0073] In short, the H-bridge based energy storage converter can meet the power quality requirements of the load in different operation modes. In the DC interconnection operation mode, it can play the role of energy storage, and energy is transferred bidirectionally between the DC grid and the energy storage; in the AC island operation mode, a local "microgrid" is formed to act as a V / f power supply, providing voltage and frequency control to the local load; in the DC island operation mode, the energy storage MMC-MVDC can also be used to provide a certain amount of power support to the DC load.

Claims

1. A hybrid supercapacitor energy storage converter based on an H-bridge, characterized in that: It comprises an upper bridge arm part and a lower bridge arm part; the upper bridge arm part and the lower bridge arm part each comprise three bridge arms, each bridge arm is formed by n H-bridge submodules and a bridge arm inductor connected in series; the upper bridge arm part is connected to a DC bus, and the lower bridge arm part is connected to a ground wire; the H-bridge submodule comprises four switch elements and an energy storage unit, and the energy storage unit is a hybrid supercapacitor; the four switch elements constitute an H-bridge structure, and the hybrid supercapacitor is connected in parallel at both ends of the H-bridge structure.

2. The H-bridge based hybrid supercapacitor energy storage converter according to claim 1, characterized in that: The energy storage unit may also be a lithium battery or a storage battery.

3. The H-bridge based hybrid supercapacitor energy storage converter according to claim 1, characterized in that: Capacitors are also connected in parallel at both ends of the energy storage unit.

4. An operating method of a hybrid supercapacitor energy storage converter based on an H-bridge as claimed in any one of claims 1 to 3, characterized in that: include: The three bridge arms of the upper bridge arm part and the three bridge arms of the lower bridge arm part of the H-bridge-based energy storage converter are connected to the AC power grid, and the DC bus of the H-bridge-based energy storage converter is connected to the DC power grid; when the power performance in the AC power grid or the DC power grid is insufficient, the hybrid supercapacitor transfers energy from the H-bridge-based energy storage converter to the AC power grid or the DC power grid through a control strategy; when the power of the AC power grid or the DC power grid is sufficient, the excess energy is stored in the hybrid supercapacitor through the H-bridge-based energy storage converter.

5. The operating method according to claim 4, characterized in that: The H-bridge based energy storage converter adopts a constant DC voltage control strategy, which means that the voltage on the DC side of the H-bridge based energy storage converter is a constant value, and the active power transmitted between the H-bridge based energy storage converter and the AC power grid is determined by external operating conditions.

6. The operating method according to claim 4, characterized in that: Also includes: When a fault occurs on the DC side of the H-bridge based energy storage converter, the bipolar level output capability of the H-bridge submodule is utilized to adjust the voltage on the DC side and actively disconnect the DC grid; the upper bridge arm part and the lower bridge arm part in the H-bridge based energy storage converter operate in parallel and serve as backup for each other.

7. The operating method according to claim 6, characterized in that: The H-bridge-based energy storage converter adopts a constant power control strategy, which means that the active power and reactive power transmitted between the H-bridge-based energy storage converter and the AC power grid interact according to given instructions to achieve tracking control of power transmission; the H-bridge submodule adopts a constant voltage control strategy or a droop control strategy.

8. The operating method according to claim 4, characterized in that: Also includes: When a fault occurs on the AC side of the H-bridge based energy storage converter, the H-bridge based energy storage converter is converted to a DC / DC operation mode, and one bridge arm is put into operation to support the DC bus voltage. When the three bridge arms of the upper bridge arm part are put into operation alternately, or the three bridge arms of the lower bridge arm part are put into operation alternately.

9. The operating method according to claim 4, characterized in that: Also includes: When faults occur on both the AC side and the DC side of the H-bridge based energy storage converter, the H-bridge based energy storage converter disconnects the DC grid and the AC grid, and operates in V / F mode to provide voltage and frequency support for the AC load, or operates in DC / DC mode to stabilize the DC voltage and provide energy supply for the DC load.

10. The operating method according to claim 9, characterized in that: When the H-bridge based energy storage converter operates in the V / F mode, the output voltage frequency of the power electronic device is adjusted by droop control simulating the droop characteristic curve of the synchronous generator.

Images