Battery testing and capacity coupling system based on microgrid and control method

Abstract

The present invention discloses a battery testing and capacity-splitting coupling system based on a microgrid, including a fuel cell testing unit, an energy storage unit, a lithium-ion battery capacity-splitting unit, an inverter unit, and an energy management unit; the energy management unit is respectively connected to the fuel cell testing unit, the energy storage unit, the lithium-ion battery capacity-splitting unit, and the inverter unit for communication, and the DC interfaces of the fuel cell testing unit, the energy storage unit, and the lithium-ion battery capacity-splitting unit are connected to the DC bus L1; one end of the inverter unit is connected to the external power grid, and the other end is connected to the DC bus L1; a control method for a battery capacity-splitting coupling system based on a microgrid is also disclosed. The present invention avoids the energy waste of a conventional resistive load consuming the electric energy generated by a fuel cell system through heat energy, and also saves the extra electric energy consumption for cooling the resistive load.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cell testing, and in particular relates to a battery testing and chemical composition coupling system based on a microgrid and a control method. Background Art

[0002] Large-scale research, verification and testing of fuel cell stacks, fuel cell systems and fuel cell engines are essential steps before the application of fuel cells. Since the fuel cell itself is a power generation device that continuously consumes hydrogen, the first solution in the traditional performance test process is to use a resistive load to consume the electricity generated by the fuel cell system through heat energy, resulting in waste of resources and increased costs. In addition, the commonly used electronic loads also need cooling towers, large fans and even air conditioners to dissipate heat in the process of releasing heat energy to ensure the normal operation of the electronic loads, so additional electricity is required; and for fuel cell power systems for new energy vehicles, whose power exceeds 30kW or even up to 100kW, the use of electronic load testing will result in a huge waste of electricity and rising testing costs.

[0003] The second solution is to use a grid-fed electronic load to feed the power output during the fuel cell test back to the grid. Although this solution can effectively avoid the heat consumption of the fuel cell during the test discharge process, due to the complexity and diversity of the test process (such as frequent start-stop loading, acceleration, and testing polarization curves, etc.) and multiple stacks in parallel testing, when feeding power to the grid in this case, it will cause serious high-frequency harmonic interference to the grid, which is difficult to handle, seriously affecting the power quality of the grid and even causing impact on the grid.

[0004] The third solution is to use the electricity output during the fuel cell test to obtain hydrogen through water electrolysis to produce hydrogen and then pass it into the fuel cell for recycling. However, the efficiency of converting hydrogen into electricity during the operation of the fuel cell is generally 50% (based on the low heating value LHV of hydrogen). Although the theoretical electrolysis efficiency of the generated electricity to produce hydrogen through water electrolysis is very high (the apparent conversion efficiency can even reach 100% to 122%), the energy conversion efficiency is only 50% to 70% in industry due to factors such as heating and polarization overpotential required to increase the hydrogen production rate. The efficiency of completing a complete cycle of hydrogen → fuel cell → electrolyzer → hydrogen is only 30%, the energy loss exceeds 70%, the energy utilization rate is extremely low, and the water electrolysis hydrogen production system (especially the solid electrolyte membrane water electrolysis hydrogen production system using precious metals platinum or iridium as catalysts) is high in cost and short in life. Therefore, this solution is not economical, and there are problems of complex system and complicated maintenance. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a battery testing and chemical composition coupling system and control method based on a microgrid.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] An embodiment of the present invention provides a microgrid-based battery testing and capacity-splitting coupling system, which includes a fuel cell testing unit, an energy storage unit, a lithium-ion battery capacity-splitting unit, an inverter unit, and an energy management unit; the energy management unit is respectively communicatively connected with the fuel cell testing unit, the energy storage unit, the lithium-ion battery capacity-splitting unit, and the inverter unit, and the DC interfaces of the fuel cell testing unit, the energy storage unit, and the lithium-ion battery capacity-splitting unit are connected to a DC bus L1; one end of the inverter unit is connected to an external power grid, and the other end is connected to the DC bus L1.

[0008] In the above scheme, the fuel cell test unit includes a plurality of fuel cell test groups and a first circuit breaker, and the plurality of fuel cell test groups are respectively connected to the DC bus L1 through the first circuit breaker; each fuel cell test group includes a fuel cell test bench and a unidirectional DC / DC converter, and the DC output end of the fuel cell to be tested in the fuel cell test bench is electrically connected to the input end of the corresponding unidirectional DC / DC converter, and the output end of the unidirectional DC / DC converter is connected to the DC bus L1 through the first circuit breaker.

[0009] In the above scheme, the energy storage unit includes an energy storage battery pack, a battery management system BMS, a first bidirectional DC / DC converter and a second circuit breaker. The energy storage battery pack is electrically connected to one end of the first bidirectional DC / DC converter, and the other end of the first bidirectional DC / DC converter is connected to the DC bus L1 through the second circuit breaker. The battery management system BMS is connected to the energy storage battery pack through a low-voltage signal line.

[0010] In the above scheme, the energy storage battery pack adopts one or more of lead-acid batteries, lead-carbon batteries, lithium-ion batteries, flow batteries, and sodium-sulfur batteries.

[0011] In the above scheme, the lithium-ion battery capacity-splitting unit includes a plurality of lithium-ion battery capacity-splitting groups and a third circuit breaker, and the plurality of lithium-ion battery capacity-splitting groups are respectively connected to the DC bus L1 through the third circuit breaker; each lithium-ion battery capacity-splitting group includes a lithium-ion battery cell capacity-splitting cabinet and a second bidirectional DC / DC converter, and the lithium-ion battery cell capacity-splitting cabinet is electrically connected to one end of the corresponding second bidirectional DC / DC converter, and the other end of the second bidirectional DC / DC converter is connected to the DC bus L1 through the third circuit breaker.

[0012] In the above scheme, the inverter unit includes a bidirectional AC / DC inverter and a grid-connected disconnect switch, the DC end of the bidirectional AC / DC inverter is electrically connected to the DC bus L1, and the AC end of the bidirectional AC / DC inverter is connected to the power grid through the grid-connected disconnect switch, which is used to realize bidirectional energy transfer between the DC bus L1 and the external power grid through AC / DC conversion under specific circumstances.

[0013] In the above scheme, the energy management unit is connected to the fuel cell test bench and the unidirectional DC / DC converter in the fuel cell test unit, the battery management system BMS and the first bidirectional DC / DC converter in the energy storage unit, the lithium ion battery cell capacity-splitting cabinet and the second bidirectional DC / DC converter in the lithium ion battery capacity-splitting unit, and the bidirectional AC / DC inverter in the inverter unit through CAN lines, and is connected to the first circuit breaker in the fuel cell test unit, the second circuit breaker in the energy storage unit, the third circuit breaker in the lithium ion battery capacity-splitting unit, the voltage and current Hall sensor of the DC bus L1, and the grid-connected isolation switch of the inverter unit through low-voltage signal lines.

[0014] The embodiment of the present invention further provides a control method for a battery-based component-capacitor coupling system based on a microgrid, and the method is implemented by the following steps:

[0015] Step (1), the energy management unit starts self-checking and confirms that the grid-connected isolation switch of the inverter unit is in the disconnected state, so that the fuel cell test and lithium-ion battery capacity coupling system enters the initial off-grid control mode;

[0016] Step (2), the energy management unit determines the total amount of electricity Q generated by the fuel cell during the entire test process through the fuel cell test unit. 1 , the energy storage unit determines the discharge capacity Q of the energy storage battery pack when it is discharged from the current SOC to the set SOC lower limit 2 and the required charge amount Q′ when charging from the current SOC to the set SOC upper limit 2 , the total capacity Q that needs to be charged during the formation and / or capacity division process of the lithium-ion battery cell is determined by the lithium-ion battery formation and capacity division unit 3 According to Q 1 , Q 2 , Q′ 2 and Q 3 The size relationship determines whether to enter the steady-state off-grid working mode, i.e., step (3) or the transient grid-connected working mode, i.e., step (4);

[0017] Step (3), the energy management unit starts the fuel cell test unit to perform an electrochemical performance test on the fuel cell to be tested, starts the lithium-ion battery capacity conversion unit to charge and discharge the lithium-ion battery cells that have entered the capacity conversion process, and the grid-connected isolation switch of the inverter unit is always in an off state, wherein the energy management unit obtains in real time the amount of electricity Q generated by the fuel cell during the test process F The amount of electricity Q required to charge the lithium-ion battery cell C And the amount of electricity Q generated by discharge D ;

[0018] Step (4), the energy management unit starts the fuel cell test unit to perform an electrochemical performance test on the fuel cell to be tested, and starts the lithium-ion battery capacity conversion unit to charge and discharge the lithium-ion battery cell entering the capacity conversion process, wherein the energy management unit obtains the power Q generated by the fuel cell during the test in real time F , the state of charge SOC of the energy storage battery pack in the energy storage unit and the amount of electricity Q required to charge the lithium-ion battery cell into different capacities C And the amount of electricity Q generated by discharge D .

[0019] In the above scheme, in step (3), when Q is detected F <Q C or Q F =0, that is, when the fuel cell is not subjected to electrochemical testing, the energy management unit sends a switch-on instruction to the first bidirectional DC / DC converter and the second circuit breaker in the energy storage unit, and then connects to the DC bus L1 to convert the electric energy stored in the energy storage battery pack into a voltage matching the DC bus L1 via the first bidirectional DC / DC converter and then sends it to the DC bus L1; when Q is detected F ≥Q C or Q D ≥0, that is, when the lithium-ion battery cell is in the discharge step or at rest, the energy management unit sends a connection instruction to the first bidirectional DC / DC converter and the second circuit breaker in the energy storage unit to be connected to the DC bus L1, and the surplus electric energy of the DC bus L1 is converted into a voltage matching the charging voltage of the energy storage battery pack through the first bidirectional DC / DC converter and then output to the energy storage battery pack.

[0020] In the above scheme, in step (4), when Q is detected F <Q C or Q F=0, that is, when the fuel cell is not subjected to electrochemical testing, the energy management unit, while ensuring that the grid-connected isolating switch in the inverter unit continues to remain disconnected, converts the electric energy stored in the energy storage battery group in the energy storage unit into a voltage matching the DC bus L1 via the first bidirectional DC / DC converter, and then sends it to the DC bus L1 to supplement the electric energy of the lithium-ion battery cells in the charging step; and when the energy management unit detects that the state of charge SOC of the energy storage battery group in the energy storage unit has dropped to a set lower limit and the lithium-ion battery cells in the capacity conversion step still need to be charged, the grid-connected isolating switch of the inverter unit is closed, converts the electric energy of the external power grid into a DC voltage matching the DC bus L1 via the bidirectional AC / DC inverter, and then sends it to the DC bus L1 to power the lithium-ion battery cells being charged; when Q is detected F ≥Q C or Q D ≥0, that is, when the lithium-ion battery cell is in the discharge step or at rest, the energy management unit, while ensuring that the grid-connected isolating switch in the inverter unit continues to remain disconnected, converts the surplus electric energy in the DC bus L1 into a voltage matching the charging voltage of the energy storage battery pack through the first bidirectional DC / DC converter in the energy storage unit according to the voltage and current fluctuations of the DC bus L1 monitored in real time, and then outputs it to the energy storage battery pack. When the energy management unit detects that the state of charge SOC of the energy storage battery pack has risen to the set upper limit while the fuel cell test is still in progress and / or the lithium-ion battery cell is still discharging or at rest, the grid-connected isolating switch of the inverter unit is closed, and the electric energy in the DC bus L1 is converted into a specified AC voltage through the bidirectional AC / DC inverter of the inverter unit, and then sent to the external power grid, ensuring the orderly and stable operation of the fuel cell test and the lithium-ion battery capacity conversion.

[0021] Compared with the prior art, the present invention uses the electric energy generated during the electrochemical test of the fuel cell for the capacity division of the lithium-ion battery by constructing a DC microgrid. On the one hand, it avoids the energy waste of the conventional resistive load consuming the electric energy generated by the fuel cell system through heat energy, and also saves the extra electric energy consumption for the resistance load cooling equipment; on the other hand, the use of the energy storage battery pack in the DC microgrid avoids the waste of electric energy of the lithium-ion battery frequently taking electricity from the external power grid for charging during the capacity division and then discharging in the form of resistance heat energy, and the more times of charging and discharging, the greater the waste of electric energy. Therefore, the battery capacity division coupling system based on the microgrid provided by the present invention realizes the efficient utilization of electric energy in the fuel cell test and lithium-ion battery capacity division process, and thus also greatly saves the electricity cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a structural schematic diagram of a battery testing and chemical composition coupling system based on a microgrid according to an embodiment of the present invention.

[0023] Figure 2 The present invention is a flow chart of a control method of a microgrid-based battery testing and chemical composition coupling system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are further described below with reference to the accompanying drawings, and the advantages and features of the present invention will become clearer as the description proceeds. However, the embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solutions of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0025] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. Those skilled in the art will appreciate that the present invention can be implemented without these specific details. In other embodiments, well-known methods, processes, components and circuits are not described in detail in order to highlight the subject matter of the present invention.

[0026] The embodiment of the present invention provides a battery testing and chemical composition coupling system based on a microgrid, such as Figure 1 As shown, it includes a fuel cell test unit 1, an energy storage unit 2, a lithium-ion battery capacity conversion unit 3, an inverter unit 4, and an energy management unit 5; the energy management unit 5 is respectively communicated with the fuel cell test unit 1, the energy storage unit 2, the lithium-ion battery capacity conversion unit 3, and the inverter unit 4, and the DC interfaces of the fuel cell test unit 1, the energy storage unit 2, and the lithium-ion battery capacity conversion unit 3 are connected to the DC bus L1; one end of the inverter unit 4 is connected to the external power grid, and the other end is connected to the DC bus L1.

[0027] The fuel cell test unit 1 includes a plurality of fuel cell test groups and a first circuit breaker 13, wherein the plurality of fuel cell test groups are respectively connected to the DC bus L1 through the first circuit breaker 13; each fuel cell test group includes a fuel cell test bench 11 and a unidirectional DC / DC converter 12, wherein the DC output end of the fuel cell to be tested in the fuel cell test bench 11 is electrically connected to the input end of the corresponding unidirectional DC / DC converter 12, and the output end of the unidirectional DC / DC converter 12 is connected to the DC bus L1 through the first circuit breaker 13.

[0028] The fuel cell test bench 11 in the fuel cell test unit 1 is used to test and evaluate the polarization curve, electrochemical impedance spectroscopy (EIS) and electrochemical performance of the fuel cell under various simulated working conditions, while the unidirectional DC / DC converter 12 converts the electric energy generated by the fuel cell during the test into the DC bus L1 after voltage conversion.

[0029] Furthermore, the fuel cell test bench 11 in the fuel cell test unit 1 can be a single unit or multiple units to form a fuel cell test bench array, and each of the fuel cell test benches in the fuel cell test bench array works independently without interfering with each other; and the number of the unidirectional DC / DC converters 12 is consistent with the number of the fuel cell test benches 11 and forms a one-to-one correspondence.

[0030] Optionally, the fuel cell test bench 11 includes but is not limited to a hydrogen flow test unit, an air flow test unit, a water management unit, a thermal management unit and a control unit, and the fuel cells tested include but are not limited to fuel cell single cells, fuel cell stacks, fuel cell systems, fuel cell engines, etc.; and different fuel cells have different configurations of the corresponding fuel cell test benches, as long as the type of fuel cell tested and the test parameters match the fuel cell test bench. Similarly, the unidirectional DC / DC converter 12 corresponding to the fuel cell test platform will also have different configuration parameters due to the different voltages and currents of the fuel cells to be tested, as long as the voltage and current intervals that can be converted match the voltage and current output by the fuel cell. In other words, the fuel cell test bench 11 in the above-mentioned fuel cell test bench array can be of the same type or of different types; correspondingly, the unidirectional DC / DC converter 12 can also be of the same type or of different types, but the input configuration parameters of each unidirectional DC / DC converter 12 must match the electrical output parameters of the fuel cell test bench to which it is connected, and its output configuration parameters must also match the voltage and current parameters of the DC bus L1.

[0031] The energy storage unit 2 includes an energy storage battery group 21, a battery management system BMS22, a first bidirectional DC / DC converter 23 and a second circuit breaker 24. The energy storage battery group 21 is electrically connected to one end of the first bidirectional DC / DC converter 23, and the other end of the first bidirectional DC / DC converter 23 is connected to the DC bus L1 through the second circuit breaker 24. The battery management system BMS22 is connected to the energy storage battery group 21 through a low-voltage signal line.

[0032] The energy storage battery group 21 of the energy storage unit 2 is used to realize bidirectional transmission of DC power with the DC bus L1 through the first bidirectional DC / DC converter 23: on the one hand, it receives the DC power generated by the fuel cell in the fuel cell test unit 1 during the test, the DC power released by the lithium-ion battery cells of the lithium-ion battery conversion unit 3 in the discharge step, and the AC power transmitted from the external power grid via the inverter unit 4; on the other hand, it directly provides DC power to the lithium-ion battery conversion unit 3 and feeds power to the external power grid via the inverter unit 4, and provides peak-shaving, frequency regulation and reactive power compensation power auxiliary services for the external power grid.

[0033] Optionally, the energy storage battery group 21 adopts one or more of lead-acid batteries, lead-carbon batteries, lithium-ion batteries, flow batteries, and sodium-sulfur batteries;

[0034] Preferably, the energy storage battery group 21 preferably uses lithium titanate batteries or all-vanadium redox flow batteries.

[0035] The battery management system BMS22 in the energy storage unit 2 is used to monitor the voltage, current and temperature of the energy storage battery group 21, accurately estimate the state of charge SOC of the energy storage battery group 21 and transmit the real-time collected data information to the energy management unit 5 through the CAN line, and at the same time balance the energy between the single cells of the energy storage battery group 21.

[0036] The lithium-ion battery capacity-splitting unit 3 includes a plurality of lithium-ion battery capacity-splitting groups and a third circuit breaker 33, and the plurality of lithium-ion battery capacity-splitting groups are respectively connected to the DC bus L1 through the third circuit breaker 33; each lithium-ion battery capacity-splitting group includes a lithium-ion battery cell capacity-splitting cabinet 31 and a second bidirectional DC / DC converter 32, and the lithium-ion battery cell capacity-splitting cabinet 31 is electrically connected to one end of the corresponding second bidirectional DC / DC converter 32, and the other end of the second bidirectional DC / DC converter 32 is connected to the DC bus L1 through the third circuit breaker 33.

[0037] The lithium-ion battery cell capacity splitting cabinet 31 in the lithium-ion battery capacity splitting unit 3 is used to charge and discharge the lithium-ion battery cells entering the capacity splitting process through the bidirectional energy transfer between the second bidirectional DC / DC converter 32 and the DC bus L1; the second bidirectional DC / DC converter 32 is used to realize the bidirectional energy transfer between the lithium-ion battery cell capacity splitting cabinet 31 and the DC bus L1 through the conversion of DC voltage, and the number of the second bidirectional DC / DC converters 32 is consistent with the number of the lithium-ion battery cell capacity splitting cabinets 31 and forms a one-to-one correspondence.

[0038] Furthermore, the lithium-ion battery cell capacity-dividing cabinet 31 may be a single cabinet or a plurality of cabinets to form a lithium-ion battery cell capacity-dividing cabinet array; moreover, each of the lithium-ion battery cell capacity-dividing cabinets in the lithium-ion battery cell capacity-dividing cabinet array operates independently without interfering with each other.

[0039] Optionally, in the above-mentioned lithium-ion battery cell capacity splitting cabinet array, depending on the type and capacity (ampere-hours) of the lithium-ion battery cells entering the capacity splitting process, the specific parameter configuration of the corresponding lithium-ion battery cell capacity splitting cabinet 31 is also different, as long as its configuration matches the process step parameters of the lithium-ion battery cells that need to be split; similarly, the second bidirectional DC / DC converter 32 corresponding to the lithium-ion battery cell capacity splitting cabinet 31 will also have different configuration parameters due to the different voltages and currents of the lithium-ion battery cells that need to be split, as long as the voltage and current range that it can convert matches the voltage and current of the lithium-ion battery cells for charging and discharging. In other words, the lithium-ion battery cell capacity cabinets 31 in the above-mentioned lithium-ion battery cell capacity cabinet array can be of the same type or of different types; correspondingly, the second bidirectional DC / DC converters 32 can also be of the same type or of different types, but the configuration parameters at both ends of each second bidirectional DC / DC converter 32 must respectively match the input and output parameters of the lithium-ion battery cell capacity cabinet 31 to which it is connected and the voltage and current parameters of the DC bus L1.

[0040] The inverter unit 4 includes a bidirectional AC / DC inverter 41 and a grid-connected isolating switch 42. The DC end of the bidirectional AC / DC inverter 41 is electrically connected to the DC bus L1, and the AC end of the bidirectional AC / DC inverter 41 is connected to the power grid through the grid-connected isolating switch 42, so as to realize bidirectional energy transfer between the DC bus L1 and the external power grid through AC / DC conversion under specific circumstances.

[0041] The energy management unit 5 is connected to the fuel cell test bench 11 and the unidirectional DC / DC converter 12 in the fuel cell test unit 1, the battery management system BMS22 and the first bidirectional DC / DC converter 23 in the energy storage unit 2, the lithium ion battery cell capacity cabinet 31 and the second bidirectional DC / DC converter 32 in the lithium ion battery capacity unit 3, and the bidirectional AC / DC inverter 41 in the inverter unit 4 through CAN lines, and is connected to the first circuit breaker 13 in the fuel cell test unit 1, the second circuit breaker 24 in the energy storage unit 2, and the third circuit breaker 33 in the lithium ion battery capacity unit 3 through low-voltage signal lines. , the voltage and current Hall sensor of the DC bus L1, and the grid-connected isolation switch 42 of the inverter unit 4 are connected to receive the real-time parameter information of the fuel cell test unit 1, the energy storage unit 2, the lithium-ion battery capacity-splitting unit 3 and the DC bus L1, and record, count and analyze the power operation data of the entire microgrid system, and issue operation instructions to the control elements and circuit breakers of the fuel cell test unit 1, the energy storage unit 2, the lithium-ion battery capacity-splitting unit 3 and the inverter unit 4 according to preset commands, so as to comprehensively manage and dispatch fuel cell testing, energy storage, lithium-ion battery cell capacity-splitting and power grid energy exchange, so as to make the operation of the entire microgrid system in the best state and achieve better economic benefits.

[0042] The microgrid-based battery test and capacity coupling system operates in a steady-state off-grid working mode and a transient grid-connected working mode:

[0043] In the steady-state off-grid working mode, the energy management unit 5 sends a start signal to the fuel cell test bench 11 in the fuel cell test unit 1, and performs an electrochemical performance test on the fuel cell to be tested according to preset parameters and steps. At the same time, a connection instruction is sent to the unidirectional DC / DC converter 12 and the first circuit breaker 13 corresponding to the fuel cell test bench 11 to convert the electric energy generated by the fuel cell under online test on the fuel cell test bench 11 into a specified voltage through the unidirectional DC / DC converter 12 and then send it to the DC bus L1; and according to the needs, the energy management unit 5 sends a start signal to the lithium-ion battery cell capacity cabinet 31 in the lithium-ion battery capacity cabinet unit 3, and performs an electrochemical performance test on the fuel cell to be tested according to preset parameters and steps. The set working step parameters and cycle parameters are used to charge and discharge the lithium-ion battery cells entering the capacity splitting process, and at the same time, the second bidirectional DC / DC converter 32 and the third circuit breaker 33 corresponding to the lithium-ion battery cell capacity splitting cabinet 31 are sent a connection instruction to be incorporated into the DC bus L1 so that the lithium-ion battery cells can convert the electric energy in the DC bus L1 through the second bidirectional DC / DC converter 32 in the charging step and output it to the lithium-ion battery cell capacity splitting cabinet 31 to charge the lithium-ion battery cells, and the lithium-ion battery cells can convert the electric energy stored in the lithium-ion battery cells into a specified voltage through the second bidirectional DC / DC converter 32 in the discharging step and then send it to the DC bus L1.

[0044] The energy management unit 5 obtains the amount of electricity Q generated by the fuel cell during the test in real time. F The amount of electricity Q required to charge the lithium-ion battery cell C And the amount of electricity Q generated by discharge D : When Q is detected F <Q C or Q F =0, that is, when the fuel cell is not undergoing electrochemical testing, the energy management unit 5 sends a connection instruction to the first bidirectional DC / DC converter 23 and the second circuit breaker 24 in the energy storage unit 2, and then connects to the DC bus L1 to convert the electric energy stored in the energy storage battery group 21 into a specified voltage via the first bidirectional DC / DC converter 23 and then sends it to the DC bus L1, thereby charging or providing electric energy for the lithium-ion battery cell that is being converted into a capacity; when Q F ≥Q C or Q D ≥0, that is, when the lithium-ion battery cell is in the discharge step or is stationary, the energy management unit 5 sends a connection instruction to the first bidirectional DC / DC converter 23 and the second circuit breaker 24 in the energy storage unit 2, and is integrated into the DC bus L1 to convert the surplus electric energy of the DC bus L1 into a specified voltage through the first bidirectional DC / DC converter 23 and then output it to the energy storage battery group 21, thereby maintaining the normal progress of the fuel cell test and the lithium-ion battery cell capacity conversion and suppressing the voltage fluctuation of the DC bus L1.

[0045] During the entire process of fuel cell testing and lithium-ion battery cell capacity division, the electric energy generated by the fuel cell is only transmitted between the fuel cell testing unit 1, the energy storage unit 2 and the lithium-ion battery capacity division unit 3, and the grid-connected isolation switch 42 of the inverter unit 4 is always in the disconnected state, and the entire microgrid-based coupling system operates in an island manner.

[0046] In the transient grid-connected working mode, the energy management unit 5 sends a start signal to the fuel cell test bench 11 in the fuel cell test unit 1, and performs an electrochemical performance test on the fuel cell to be tested according to preset parameters and steps. At the same time, a connection instruction is sent to the unidirectional DC / DC converter 12 and the first circuit breaker 13 corresponding to the fuel cell test bench 11 to convert the electric energy generated by the fuel cell under online test on the fuel cell test bench 11 into a specified voltage through the unidirectional DC / DC converter 12 and then send it to the DC bus L1; and according to the needs, the energy management unit 5 sends a start signal to the lithium ion battery cell capacity cabinet 31 in the lithium ion battery capacity cabinet unit 3, and performs an electrochemical performance test on the fuel cell to be tested according to preset parameters and steps. The set working step parameters and cycle parameters are used to charge and discharge the lithium-ion battery cells entering the capacity splitting process, and at the same time, the second bidirectional DC / DC converter 32 and the third circuit breaker 33 corresponding to the lithium-ion battery cell capacity splitting cabinet 31 are sent a connection instruction to be incorporated into the DC bus L1 so that the lithium-ion battery cells can convert the electric energy in the DC bus L1 through the second bidirectional DC / DC converter 32 in the charging step and output it to the lithium-ion battery cell capacity splitting cabinet 31 to charge the lithium-ion battery cells, and the lithium-ion battery cells can convert the electric energy stored in the lithium-ion battery cells into a specified voltage through the second bidirectional DC / DC converter 32 in the discharging step and then send it to the DC bus L1.

[0047] The energy management unit 5 obtains the amount of electricity Q generated by the fuel cell during the test in real time. F , the state of charge SOC of the energy storage battery pack 21 in the energy storage unit 2 and the amount of electricity Q required for charging the lithium-ion battery cell into different capacities C And the amount of electricity Q generated by discharge D : When Q is detected F <Q C or Q F=0, that is, when the fuel cell is not subjected to electrochemical testing, the energy management unit 5 preferentially converts the electric energy stored in the energy storage battery group 21 in the energy storage unit 2 into a voltage with a prescribed voltage via the first bidirectional DC / DC converter 23 and then sends it to the DC bus L1 to supplement the electric energy for the lithium-ion battery cells in the charging step. When the energy management unit 5 detects that the state of charge SOC of the energy storage battery group 21 has dropped to the set lower limit and the lithium-ion battery cells in the capacity conversion step still need to be charged, the grid-connected isolating switch 42 of the inverter unit 4 is closed to convert the electric energy of the external power grid into a prescribed DC voltage via the bidirectional AC / DC inverter 41 of the inverter unit 4 and then send it to the DC bus L1 to supply power for the lithium-ion battery cells being charged. When Q is detected F ≥Q C or Q D ≥0 means that when the lithium-ion battery cell is in the discharge step or at rest, the surplus electric energy in the DC bus L1 is converted into a specified voltage through the first bidirectional DC / DC converter 23 and then output to the energy storage battery group 21. When the energy management unit 5 detects that the state of charge SOC of the energy storage battery group 21 has risen to the set upper limit and the fuel cell test is still in progress, the grid-connected isolation switch 42 of the inverter unit 4 is closed to convert the electric energy in the DC bus L1 into a specified AC voltage through the bidirectional AC / DC inverter 41 of the inverter unit 4 and then send it to the external power grid. This ensures the orderly and stable operation of the fuel cell test and the lithium-ion battery capacity conversion and the stability of the DC bus L1 voltage.

[0048] The present invention uses the electric energy generated during the electrochemical test of the fuel cell for the capacity division of the lithium-ion battery by constructing a direct current microgrid. On the one hand, it avoids the energy waste of the conventional resistive load consuming the electric energy generated by the fuel cell system through heat energy, and also saves the extra electric energy consumption for the resistance load cooling equipment; on the other hand, the use of the energy storage battery pack in the direct current microgrid avoids the electric energy waste of the lithium-ion battery frequently taking electricity from the external power grid for charging during the capacity division and then discharging in the form of resistive heat energy, and the more times of charging and discharging, the greater the electric energy waste. Therefore, the microgrid-based battery testing and capacity division coupling system provided by the present invention realizes the efficient utilization of electric energy in the fuel cell testing and lithium-ion battery capacity division process, and thus also greatly saves electricity costs.

[0049] In addition, when power needs to be supplied to the grid in extreme cases, the coupling system provided by the present invention can avoid the serious interference of the high-frequency harmonics of the grid by the usual grid-fed electronic loads due to the use of energy storage battery packs, thereby ensuring the power quality of the grid; on the other hand, it can also achieve peak shaving and valley filling, harmonic control and reactive power compensation for the grid, thereby improving the power quality of the grid; at the same time, the use of energy storage battery packs can also bring additional benefits to enterprises through power auxiliary services such as valley power consumption, peak shaving and frequency regulation.

[0050] The embodiment of the present invention also provides a microgrid-based battery test and chemical composition coupling system control method, such as Figure 2 As shown, the method is implemented by the following steps:

[0051] In step 200, the energy management unit 5 starts self-checking and confirms that the grid-connected disconnector 42 of the inverter unit 4 is in the disconnected state, so that the microgrid-based battery test and capacity-sharing coupling system enters the initial off-grid control mode. Then, step 201 is entered.

[0052] In step 201, the energy management unit 5 obtains the number of fuel cells to be tested in the fuel cell testing unit 1 and the test parameters to calculate the total power Q generated by the fuel cell during the entire test process. 1 The SOC of the energy storage battery group 21 is obtained by the BMS 22 in the energy storage unit 2, so as to calculate the discharge amount Q of the energy storage battery group 21 when it is discharged from the current SOC to the set SOC lower limit. 2 and the required charge amount Q′ when charging from the current SOC to the set SOC upper limit 2 , obtain the capacity model (i.e., ampere-hour) and number of the lithium-ion battery cells in the lithium-ion battery cell forming and forming cabinet 31 in the lithium-ion battery forming and forming unit 3, thereby calculating the total capacity Q of the lithium-ion battery cells that need to be charged during the formation and / or forming and forming process 3 ; Then compare Q 1 , Q 2 , Q′ 2 and Q 3 The size between the two and proceed to step 202.

[0053] In step 202, when the energy management unit 5 detects that Q 1 ≤Q′ 2 And Q 3 ≤Q 1 +Q 2 When Q is detected, the process proceeds to step 210, that is, the steady-state off-grid working mode is entered; 1 >Q′ 2 or Q 3 >Q 1 +Q 2 , then enter step 220, that is, enter the transient grid-connected working mode.

[0054] In step 210, the energy management unit 5 sends a start signal to the fuel cell test bench 11 in the fuel cell test unit 1, performs an electrochemical performance test on the fuel cell to be tested according to preset parameters and steps, and at the same time sends a connection instruction to the unidirectional DC / DC converter 12 and the first circuit breaker 13 corresponding to the fuel cell test bench 11 to convert the electric energy generated by the fuel cell under online test on the fuel cell test bench 11 into a voltage matching the DC bus L1 through the unidirectional DC / DC converter 12 and then send it to the DC bus L1; and according to the needs, the energy management unit 5 sends a start signal to the lithium ion battery cell capacity cabinet 31 in the lithium ion battery capacity cabinet unit 3, according to the preset The process step parameters and cycle parameters charge and discharge the lithium-ion battery cells that enter the capacity splitting process, and at the same time send a connection instruction to the second bidirectional DC / DC converter 32 and the third circuit breaker 33 corresponding to the lithium-ion battery cell capacity splitting cabinet 31 to be connected to the DC bus L1 so that the lithium-ion battery cells can convert the electric energy in the DC bus L1 through the second bidirectional DC / DC converter 32 in the charging process step and output it to the lithium-ion battery cell capacity splitting cabinet 31 to charge the lithium-ion battery cells, and the lithium-ion battery cells can convert the electric energy stored in the lithium-ion battery cells through the second bidirectional DC / DC converter 32 into a voltage matching the DC bus L1 and then send it to the DC bus L1 in the discharge process step. In the whole process of fuel cell testing and lithium-ion battery cell capacity splitting, the electric energy generated by the fuel cell is only transmitted between the fuel cell testing unit 1, the energy storage unit 2 and the lithium-ion battery capacity splitting unit 3, and the grid-connected isolation switch 42 of the inverter unit 4 is always in the disconnected state, and the entire microgrid-based coupling system is islanded.

[0055] The energy management unit obtains the amount of electricity Q generated by the fuel cell during the test in real time. F The amount of electricity Q required to charge the lithium-ion battery cell C And the amount of electricity Q generated by discharge D , then compare Q F With Q C The size between Q D and proceed to step 211.

[0056] In step 211, the energy management unit 5 starts to detect whether there is Q F <Q C or Q F =0 means that the fuel cell has not been subjected to electrochemical testing: if so, the process proceeds to step 212; if not, the process proceeds to step 213.

[0057] In step 212, the energy management unit 5 sends a connection instruction to the first bidirectional DC / DC converter 23 and the second circuit breaker 24 in the energy storage unit 2, and integrates into the DC bus L1. The electric energy stored in the energy storage battery group 21 is converted into a voltage matching the DC bus L1 via the first bidirectional DC / DC converter 23 and then sent to the DC bus L1, so as to charge or provide electric energy for the lithium-ion battery cells that are being divided into capacities. Meanwhile, the energy management unit 5 sends a disconnection signal to the third circuit breaker 33 corresponding to one or more lithium-ion battery cell dividing cabinets 31 according to the voltage and current fluctuations of the DC bus L1 monitored in real time, and adopts a strategy of timely delaying the charging of the lithium-ion battery cells to ensure the stability of the DC bus L1 voltage.

[0058] In step 213, the energy management unit 5 starts to detect whether there is Q F ≥Q C or Q D ≥0 means that the lithium-ion battery cell is in the discharge step or is at rest: if so, proceed to step 214; if not, return to step 211.

[0059] In step 214, the energy management unit 5 sends a connection instruction to the first bidirectional DC / DC converter 23 and the second circuit breaker 24 in the energy storage unit 2, and integrates into the DC bus L1 to convert the surplus electric energy of the DC bus L1 into a voltage matching the charging voltage of the energy storage battery group 21 via the first bidirectional DC / DC converter 23, and then outputs it to the energy storage battery group 21, thereby maintaining the normal progress of the fuel cell test and the lithium-ion battery cell discharging process; meanwhile, when the fuel cell test and the lithium-ion battery cell discharging process are carried out simultaneously, the energy management unit 5 sends a pause signal to one or more fuel cell test benches 11 according to the voltage and current fluctuations of the DC bus L1 monitored in real time, and adopts a strategy of timely delaying the fuel cell test to ensure the stability of the DC bus L1 voltage.

[0060] In step 220, the energy management unit 5 sends a start signal to the fuel cell test bench 11 in the fuel cell test unit 1, performs an electrochemical performance test on the fuel cell to be tested according to preset parameters and steps, and at the same time sends a connection instruction to the unidirectional DC / DC converter 12 and the first circuit breaker 13 corresponding to the fuel cell test bench 11 to convert the electric energy generated by the fuel cell under online test on the fuel cell test bench 11 into a voltage matching the DC bus L1 through the unidirectional DC / DC converter 12 and then send it to the DC bus L1; and according to the needs, the energy management unit 5 sends a start signal to the lithium ion battery cell capacity cabinet 31 in the lithium ion battery capacity cabinet unit 3, according to the preset The step parameters and cycle parameters are used to charge and discharge the lithium-ion battery cells that have entered the capacity splitting process, and at the same time, a connection instruction is sent to the second bidirectional DC / DC converter 32 and the third circuit breaker 33 corresponding to the lithium-ion battery cell capacity splitting cabinet 31 to be incorporated into the DC bus L1 so that the lithium-ion battery cells can convert the electric energy in the DC bus L1 through the second bidirectional DC / DC converter 32 in the charging step and output it to the lithium-ion battery cell capacity splitting cabinet 31 to charge the lithium-ion battery cells, and the lithium-ion battery cells can convert the electric energy stored in the lithium-ion battery cells into a voltage matching the DC bus L1 through the second bidirectional DC / DC converter 32 in the discharging step and then send it to the DC bus L1.

[0061] The energy management unit obtains the amount of electricity Q generated by the fuel cell during the test in real time. F , the state of charge SOC of the energy storage battery pack in the energy storage unit and the amount of electricity Q required to charge the lithium-ion battery cell into different capacities C And the amount of electricity Q generated by discharge D , then compare Q F With Q C The size between Q D and proceed to step 221.

[0062] In step 221, the energy management unit 5 starts to detect whether there is Q F <Q C or Q F =0 means that the fuel cell has not been subjected to electrochemical testing: if so, the process proceeds to step 222; if not, the process proceeds to step 225.

[0063] In step 222 , the energy management unit 5 continues to detect whether the state of charge SOC of the energy storage battery group 21 drops to a set lower limit: if not, the process proceeds to step 223 ; if so, the process proceeds to step 224 .

[0064] In step 223, the energy management unit 5, while ensuring that the grid-connected isolating switch 42 in the inverter unit 4 continues to remain disconnected, preferentially converts the electric energy stored in the energy storage battery group 21 in the energy storage unit 2 into a voltage matching the DC bus L1 via the first bidirectional DC / DC converter 23, and then sends it to the DC bus L1 to replenish electric energy for the lithium-ion battery cells in the charging step; meanwhile, the energy management unit 5 sends a disconnect signal to the third circuit breaker 33 corresponding to one or more lithium-ion battery cell capacity-splitting cabinets 31 in the lithium-ion battery capacity-splitting unit 3 according to the voltage and current fluctuations of the DC bus L1 monitored in real time, and adopts a strategy of timely delaying the charging of the lithium-ion battery cells to ensure the stability of the DC bus L1 voltage.

[0065] In step 224, when the energy management unit 5 detects that the state of charge SOC of the energy storage battery pack 21 in the energy storage unit 2 has dropped to the set lower limit and the lithium-ion battery cells in the capacity conversion step still need to be charged, the energy management unit 5 sends a closing signal to the grid-connected disconnector 42 of the inverter unit 4 to convert the electric energy of the external grid into a DC voltage matching the DC bus L1 via the bidirectional AC / DC inverter 41 and then send it to the DC bus L1 to power the lithium-ion battery cells being charged.

[0066] In step 225, the energy management unit 5 starts to detect whether there is Q F ≥Q C or Q D ≥0 means that the lithium-ion battery cell is in the discharge step or is at rest: if so, proceed to step 226; if not, return to step 221.

[0067] In step 226 , the energy management unit 5 continues to detect whether the state of charge SOC of the energy storage battery group 21 rises to the set upper limit: if not, the process proceeds to step 227 ; if so, the process proceeds to step 228 .

[0068] In step 227, the energy management unit 5 ensures that the grid-connected disconnecting switch 42 in the inverter unit 4 continues to remain disconnected, and converts the surplus electric energy in the DC bus L1 into a voltage matching the charging voltage of the energy storage battery group 21 through the first bidirectional DC / DC converter 23 in the energy storage unit 2 according to the voltage and current fluctuations of the DC bus L1 monitored in real time, and then outputs it to the energy storage battery group 21; meanwhile, when the fuel cell test and the lithium-ion battery cell discharge process are carried out simultaneously, the energy management unit 5 sends a pause signal to one or more fuel cell test benches 11 in the fuel cell test unit 1 according to the voltage and current fluctuations of the DC bus L1 monitored in real time, and adopts a strategy of timely delaying the fuel cell test to ensure the stability of the DC bus L1 voltage.

[0069] In step 228, when the energy management unit 5 detects that the state of charge SOC of the energy storage battery group 21 has risen to the set upper limit while the fuel cell test is still in progress and / or the lithium-ion battery cell is still discharging or standing still, the energy management unit 5 sends a closing signal to the grid-connected disconnector 42 of the inverter unit 4 to convert the electric energy in the DC bus L1 into a specified AC voltage via the bidirectional AC / DC inverter 41 of the inverter unit 4 and then send it to the external power grid, thereby ensuring the orderly and smooth operation of the fuel cell test and the lithium-ion battery capacity conversion.

[0070] The embodiments of the present invention are disclosed as above, however, the embodiments are not intended to limit the scope of the present invention. Simple equivalent changes and modifications made according to the claims and description of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A battery testing and chemical composition coupling system based on microgrid, It is characterized in that It includes a fuel cell test unit, an energy storage unit, a lithium-ion battery capacity conversion unit, an inverter unit, and an energy management unit; the energy management unit is respectively connected to the fuel cell test unit, the energy storage unit, the lithium-ion battery capacity conversion unit, and the inverter unit for communication; the DC interfaces of the fuel cell test unit, the energy storage unit, and the lithium-ion battery capacity conversion unit are connected to the DC bus L1; one end of the inverter unit is connected to the external power grid, and the other end is connected to the DC bus L1; the energy storage unit includes an energy storage battery pack, a battery management system BMS, a first bidirectional DC / DC converter, and a second circuit breaker, The energy storage battery pack is electrically connected to one end of the first bidirectional DC / DC converter, the other end of the first bidirectional DC / DC converter is connected to the DC bus L1 through the second circuit breaker, and the battery management system BMS is connected to the energy storage battery pack through a low-voltage signal line; the energy storage battery pack adopts one or more of lead-acid batteries, lead-carbon batteries, lithium-ion batteries, flow batteries, and sodium-sulfur batteries; the lithium-ion battery capacity-splitting unit includes a plurality of lithium-ion battery capacity-splitting groups and a third circuit breaker, and the plurality of lithium-ion battery capacity-splitting groups are respectively connected to the DC bus L1 through the third circuit breaker. L1 is connected; each lithium-ion battery capacity group includes a lithium-ion battery cell capacity cabinet and a second bidirectional DC / DC converter, the lithium-ion battery cell capacity cabinet is electrically connected to one end of the corresponding second bidirectional DC / DC converter, and the other end of the second bidirectional DC / DC converter is connected to the DC bus L1 through a third circuit breaker; the inverter unit includes a bidirectional AC / DC inverter and a grid-connected isolating switch, the DC end of the bidirectional AC / DC inverter is electrically connected to the DC bus L1, and the AC end of the bidirectional AC / DC inverter is connected to the grid-connected isolating switch through the grid-connected isolating switch. The grid is connected; when the state of charge of the energy storage battery pack has dropped to the set lower limit and the lithium-ion battery cells in the capacity conversion step still need to be charged, the grid-connected isolating switch is closed and the electric energy of the external grid is converted into a specified DC voltage via the bidirectional AC / DC inverter and then sent to the DC bus L1 to supply power to the lithium-ion battery cells being charged; when the state of charge of the energy storage battery pack has risen to the set upper limit and the fuel cell test is still in progress, the grid-connected isolating switch is closed and the electric energy in the DC bus L1 is converted into a specified AC voltage via the bidirectional AC / DC inverter and then sent to the external grid.

2. The microgrid-based battery testing and chemical composition coupling system according to claim 1, It is characterized in that The fuel cell test unit includes a plurality of fuel cell test groups and a first circuit breaker, wherein the plurality of fuel cell test groups are respectively connected to the DC bus L1 through the first circuit breaker; each fuel cell test group includes a fuel cell test bench 11 and a unidirectional DC / DC converter 12, wherein the DC output end of the fuel cell to be tested in the fuel cell test bench 11 is electrically connected to the input end of the corresponding unidirectional DC / DC converter, and the output end of the unidirectional DC / DC converter is connected to the DC bus L1 through the first circuit breaker.

3. The microgrid-based battery testing and chemical composition coupling system according to claim 1, It is characterized in that The energy management unit is connected to the fuel cell test bench and the unidirectional DC / DC converter in the fuel cell test unit, the battery management system BMS and the first bidirectional DC / DC converter in the energy storage unit, the lithium ion battery cell capacity-splitting cabinet and the second bidirectional DC / DC converter in the lithium ion battery capacity-splitting unit, and the bidirectional AC / DC inverter in the inverter unit through CAN lines, and is connected to the first circuit breaker in the fuel cell test unit, the second circuit breaker in the energy storage unit, the third circuit breaker in the lithium ion battery capacity-splitting unit, the voltage and current Hall sensor of the DC bus L1, and the grid-connected isolation switch of the inverter unit through low-voltage signal lines.

4. A control method for a battery split-capacity coupling system based on a microgrid, applied to a battery test and split-capacity coupling system based on a microgrid as claimed in any one of claims 1 to 3, It is characterized in that This method is implemented through the following steps: Step (1), the energy management unit starts self-checking and confirms that the grid-connected isolation switch of the inverter unit is in the disconnected state, so that the fuel cell test and lithium-ion battery capacity coupling system enters the initial off-grid control mode; Step (2), the energy management unit determines the total amount of electricity Q1 generated by the fuel cell during the entire test process through the fuel cell test unit, determines the discharge amount Q2 of the energy storage battery group when it is discharged from the current SOC to the set SOC lower limit and the required charging amount Q′2 when it is charged from the current SOC to the set SOC upper limit through the energy storage unit, and determines the total capacity Q3 of the lithium-ion battery cells that need to be charged during the formation and / or capacity division process through the lithium-ion battery formation and division unit; according to the size relationship of Q1, Q2, Q′2 and Q3, determine whether to enter the steady-state off-grid working mode, i.e., step (3) or the transient grid-connected working mode, i.e., step (4); when Q1≤Q′2 and Q3≤Q1+Q2, enter the steady-state off-grid working mode, i.e., step (3); when Q1>Q′2 or Q3>Q1+Q2, enter the transient grid-connected working mode, i.e., step (4); Step (3), the energy management unit starts the fuel cell test unit to perform an electrochemical performance test on the fuel cell to be tested, starts the lithium-ion battery capacity conversion unit to charge and discharge the lithium-ion battery cells that have entered the capacity conversion process, and the grid-connected isolation switch of the inverter unit is always in an off state, wherein the energy management unit obtains in real time the amount of electricity QF generated by the fuel cell during the test, the amount of electricity QC required for charging the lithium-ion battery cells for capacity conversion, and the amount of electricity QD generated by discharge; In step (4), the energy management unit starts the fuel cell test unit to perform an electrochemical performance test on the fuel cell to be tested, and starts the lithium-ion battery capacity conversion unit to charge and discharge the lithium-ion battery cells that have entered the capacity conversion process, wherein the energy management unit obtains in real time the amount of electricity QF generated by the fuel cell during the test, the state of charge SOC of the energy storage battery group in the energy storage unit, the amount of electricity QC required for charging the lithium-ion battery cells for capacity conversion, and the amount of electricity QD generated by discharging.

5. The control method of the battery-to-capacitor coupling system based on microgrid according to claim 4, It is characterized in that In the step (3), when it is detected that QF<QC or QF=0, that is, the fuel cell is not subjected to electrochemical testing, the energy management unit sends a connection instruction to the first bidirectional DC / DC converter and the second circuit breaker in the energy storage unit, and is integrated into the DC bus L1 to convert the electric energy stored in the energy storage battery pack into a voltage matching the DC bus L1 via the first bidirectional DC / DC converter, and then sends it to the DC bus L1; when it is detected that QF≥QC or QD≥0, that is, the lithium-ion battery cell is in a discharge step or is stationary, the energy management unit sends a connection instruction to the first bidirectional DC / DC converter and the second circuit breaker in the energy storage unit, and is integrated into the DC bus L1 to convert the surplus electric energy of the DC bus L1 into a voltage matching the charging voltage of the energy storage battery pack via the first bidirectional DC / DC converter, and then output it to the energy storage battery pack.

6. The control method of the battery-to-capacitor coupling system based on microgrid according to claim 4 or 5, It is characterized in that In the step (4), when it is detected that QF<QC or QF=0, that is, the fuel cell is not subjected to electrochemical testing, the energy management unit, while ensuring that the grid-connected isolating switch in the inverter unit continues to remain disconnected, converts the electric energy stored in the energy storage battery group in the energy storage unit into a voltage matching the DC bus L1 via the first bidirectional DC / DC converter, and then sends the converted electric energy to the DC bus L1 to supplement the electric energy of the lithium-ion battery cells in the charging step; and when the energy management unit detects that the state of charge SOC of the energy storage battery group in the energy storage unit has dropped to a set lower limit and the lithium-ion battery cells in the capacity conversion step still need to be charged, the grid-connected isolating switch of the inverter unit is closed, converts the electric energy of the external power grid into a DC voltage matching the DC bus L1 via the bidirectional AC / DC inverter, and then sends the converted electric energy to the DC bus L1 to power the lithium-ion battery cells being charged; when it is detected that QF≥ When QC or QD≥0, that is, the lithium-ion battery cell is in the discharge step or at rest, the energy management unit ensures that the grid-connected isolating switch in the inverter unit continues to remain disconnected, and according to the voltage and current fluctuations of the DC bus L1 monitored in real time, converts the surplus electric energy in the DC bus L1 into a voltage matching the charging voltage of the energy storage battery pack through the first bidirectional DC / DC converter in the energy storage unit, and then outputs it to the energy storage battery pack. When the energy management unit detects that the state of charge SOC of the energy storage battery pack has risen to the set upper limit while the fuel cell test is still in progress and / or the lithium-ion battery cell is still discharging or at rest, the grid-connected isolating switch of the inverter unit is closed, and the electric energy in the DC bus L1 is converted into a specified AC voltage through the bidirectional AC / DC inverter of the inverter unit, and then sent to the external power grid, ensuring the orderly and stable operation of the fuel cell test and the lithium-ion battery capacity conversion.

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