An active balancing circuit suitable for solid oxide batteries

Abstract

This disclosure relates to an active balancing circuit suitable for solid oxide batteries. The circuit's power module includes n electrically connected power components. The circuit comprises n+1 inductors, n switching units, a capacitor, a measurement unit, and a signal generation unit. The signal generation unit is connected to the measurement unit, the control terminals of each transistor, and the power supply. It is used to generate switching control signals and target currents based on the electrical parameters of each power component and preset electrical parameters. The switching control signals act on the control terminals of each transistor, and the target currents are used to configure the power supply current of the power module. The embodiments of this disclosure can achieve current balancing among the power components in the power module, realize independent decoupling control of each power component, and have high current balancing capability and high control efficiency, effectively improving the uniformity of the power module.

Description

Technical Field

[0001] This disclosure relates to the field of energy management technology, and more particularly to an active balancing circuit suitable for solid oxide batteries. Background Technology

[0002] Green hydrogen can not only serve as a long-term energy storage medium to help power systems absorb fluctuating renewable energy sources like wind and solar power on a large scale, but it can also serve as a green energy source and raw material to help industries that struggle with carbon reduction, such as chemical, transportation, and metallurgy, achieve energy conservation and emission reduction. Electrolysis of water is an important method for large-scale production of green hydrogen. Among common technologies, solid oxide electrolysis (SOE) has the advantage of high hydrogen production efficiency; when an external steam supply is available, its energy consumption for hydrogen production can be as low as 3.4 kWh / Nm³. 3 Hydrogen, with energy consumption far lower than that of currently mature alkaline electrolysis (typically 5 kWh / Nm³), is used. 3 Hydrogen (hydrogen gas) is widely considered the next generation of electrolysis technology. Besides its high efficiency, it also possesses the unique advantage of reversibility, hence the name Solid Oxide Cell (SOC). This means it can operate in either electrolysis mode (Solid Oxide Electrolysis Cell, SOEC) to convert electrical energy into hydrogen energy, or in fuel cell mode (Solid Oxide Fuel Cell, SOFC) to convert hydrogen energy back into electrical energy. This feature can reduce the investment cost of hydrogen energy storage projects. Although the technology is currently relatively immature and costly, companies both domestically and internationally are already promoting its commercialization. As production scales up, economies of scale will effectively reduce manufacturing costs, gradually increasing market competitiveness.

[0003] Capacity scaling is one of the key technical challenges facing System-on-Chip (SOC) technology. SOC cells are made of ceramic materials, less than 1 mm thick. Due to the fragile mechanical properties of ceramic materials, the area of ​​a single cell is difficult to increase, typically to 150 cm². 2 The first step in scaling up the capacity of a System-on-Chip (SOC) is to stack individual cells into a stack. A single stack typically has a power output of several kilowatts and a voltage of tens of volts. To increase power and voltage while reducing investment and losses in the power conversion process, further scaling up usually requires stacking multiple stacks to form a tower connected in series in the circuitry and in parallel in the gas path. These towers are then integrated into a hot box to form a module, and finally, multiple modules are combined to form a large-capacity system. A tower structure consisting of three stacks connected in series is shown below. Figure 1As shown, steam and air enter the heatbox through a main pipe and are then distributed to different fuel cell stacks via manifolds. The hydrogen and air produced after the fuel cell reaction first pass through the manifolds to the main pipe and then flow out of the fuel cell stacks. As the number of fuel cell stacks in the tower increases, ensuring consistent airflow distribution between different stacks becomes increasingly difficult, while the current in electrically connected stacks must be equal. Due to the bottleneck effect, the maximum current of the tower will be limited by the stack with the least airflow, preventing linear power amplification. Simultaneously, inconsistencies in the fuel cell stacks themselves due to manufacturing defects or degradation will lead to higher internal resistance in some stacks, creating localized hot spots and increasing temperature unevenness. These gas and heat unevenness issues further accelerate tower performance degradation and jeopardize overall lifespan. Since the entire tower operates in a high-temperature environment of approximately 750°C, no valves or instruments can withstand such high temperatures; therefore, there are virtually no direct control methods to improve gas and heat distribution.

[0004] As the hub for the conversion of electricity, gas, and heat, the fuel cell stack is almost the only controllable component within the heat box. Leveraging its pivotal nature, it's possible to replace flow control and temperature control with electrical control, improving stack uniformity by altering the current of different fuel cell stacks. For example, when gas flow distribution is uneven across multiple fuel cell stacks, stacks with sufficient gas flow distribution have lower voltage and generate less heat, while stacks with insufficient gas flow distribution have higher voltage and generate more heat, leading to increased temperature inconsistency within the stack. Simultaneously, the stack's maximum current is limited by stacks with insufficient gas flow distribution, preventing the stack from fully utilizing the feed gas and resulting in a decrease in maximum power. To address this, reducing the current of stacks with insufficient gas flow distribution and increasing the current of stacks with sufficient gas flow distribution could potentially improve temperature uniformity and increase the stack's maximum power.

[0005] The lithium battery field also faces similar balancing problems in series-connected battery packs. Large-scale lithium battery systems also require multiple cells connected in series and parallel. Series-connected batteries are affected by factors such as self-discharge rate and manufacturing inconsistencies, causing inconsistencies in the State of Charge (SoC) of individual cells, leading to a reduction in the usable capacity of the series-connected battery pack. Current solutions involve bringing out the positive and negative leads of each cell in the series-connected battery pack and connecting them to an external balancing circuit. The charging and discharging of individual cells is controlled by switches in the balancing circuit, or controllable energy transfer is achieved between different cells or between cells and the battery pack, thereby achieving SoC balancing. Existing balancing circuit topologies include resistive dissipation topologies, capacitor topologies, inductor topologies, flyback converter topologies, etc. However, the most fundamental difference between lithium battery balancing and SoC balancing is that the former needs to balance the SoC, while the latter needs to balance the current. This difference leads existing lithium battery balancing circuits to operate intermittently, resulting in fluctuating current through individual lithium cells, making constant current transfer impossible. SOC stacks need to operate under relatively stable current, and rapidly fluctuating current will pose a great challenge to the durability of SOC stacks.

[0006] It is evident that the balancing circuits suitable for lithium batteries cannot be directly applied to SOC stack towers. The specific reasons are explained below.

[0007] Common series active balancing topologies used in lithium battery applications include controllable resistor balancing topologies, capacitor balancing topologies, inductor balancing topologies, flyback converter topologies, etc. Figure 2 As shown. Among them, the controllable resistance balancing topology ( Figure 2 In (a)), each series-connected cell is connected to a resistor via a switch. By controlling the opening and closing of the switch, independent discharge of each cell can be achieved. Therefore, by discharging cells with a high state of charge, the state of charge of different cells can be balanced; (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 2 (b) and Fit inductor balance topology ( Figure 2 In the middle (c) topology, inductors and capacitors are used as energy storage carriers. Energy is transferred between adjacent individual cells through the sequential opening and closing of switches, thereby balancing the state of charge of different individual cells; flyback converter topology ( Figure 2 In (d), each individual cell is connected to the primary side of a transformer via a switch, and the secondary side of the transformer is also connected to the entire battery pack via a switch. By combining the opening and closing of the switches, energy transfer between the battery pack and the corresponding individual cells can be achieved, thereby achieving balance. Figure 2The examples shown are only a few basic balancing topologies. Based on these topologies, many other forms of topologies have been derived and developed, which can realize energy transfer between individual cells and between individual cells and battery packs, thereby achieving the balancing function. The embodiments disclosed herein will not be described in detail.

[0008] However, none of the current balancing circuits suitable for lithium batteries can be directly applied to SOC stacks because these circuits can only achieve discrete charge transfer, not constant current transfer. Figure 2 Taking the controllable resistor balancing topology shown in (a) as an example, when a switch is turned on or off, the current in the corresponding branch changes abruptly, which in turn causes abrupt changes in the current through the corresponding battery. This abrupt change occurs in... Figure 2 This problem also occurs in the other circuits shown. The root cause is that the switch is directly connected in series in the branch connecting the main circuit and the balancing circuit. Therefore, when the switch state changes, the current in the main circuit also changes abruptly, making it impossible to achieve a constant current transfer. This problem is common in current lithium battery series balancing circuits. This fluctuating current causes fluctuations in the electrochemical reaction rate at the SOC electrode interface, leading to an unstable redox environment at the interface, which may compromise battery life.

[0009] Therefore, existing active balancing circuits for lithium batteries are difficult to apply directly to the balancing of SOC stacks, and new balancing circuit topologies need to be designed. Summary of the Invention

[0010] According to one aspect of this disclosure, an active balancing circuit is provided for realizing a constant transfer current in a power module. The power module includes n electrically connected power components. The circuit includes: n+1 inductors, n switching units, a capacitor, a measurement unit, and a signal generation unit. Each switching unit includes a transistor and a diode. A first terminal of the transistor is connected to the cathode of the diode as a first terminal of the switching unit, and a second terminal of the transistor is connected to the anode of the diode as a second terminal of the switching unit.

[0011] The positive and negative terminals of the power module are connected to a power supply. The positive terminal of the first power component among the n power components serves as the positive terminal of the power module, and the negative terminal of the last power component serves as the negative terminal of the power module.

[0012] The positive terminal of the i-th power component is connected to the first terminal of the i-th inductor, the negative terminal of the i-th power component is connected to the first terminal of the (i+1)-th inductor and the positive terminal of the (i+1)-th power component, and the second terminal of the i-th inductor is connected to the first terminal of the transistor and the cathode of the diode in the i-th switching unit.

[0013] The second terminal of the i-th switching unit is connected to the first terminal of the (i+1)-th switching unit. Each switching unit corresponds one-to-one with a power component, where 1 ≤ i ≤ n-1 and i and n are both integers.

[0014] The first terminal of the capacitor is connected to the first terminal of the first switching unit and the second terminal of the first inductor, and the second terminal of the capacitor is connected to the second terminal of the last switching unit and the second terminal of the last inductor.

[0015] The measuring unit is connected to the first terminal of each inductor and is used to measure the electrical parameters of each power component.

[0016] The signal generation unit is connected to the measurement unit, the control terminals of each transistor, and the power supply, and is used for:

[0017] Based on the electrical parameters of each power component and preset electrical parameters, a switch control signal and a target current are generated. The switch control signal acts on the control terminal of each transistor, and the target current is used to configure the power supply current of the power supply.

[0018] In one possible implementation, the switch control signal includes transistor control signals for transistors in each switch unit, wherein the duty cycle of the transistor control signal being off is positively correlated with the current magnitude of the corresponding power component.

[0019] In one possible implementation, the electrical parameter includes current, and the signal generation unit includes:

[0020] The duty cycle generation unit is used to determine the corresponding duty cycle based on the current of each power component and the preset current.

[0021] A switch signal generation unit is used to generate the switch control signal according to each duty cycle and a preset sawtooth wave signal.

[0022] A current generating unit is used to determine the target current based on the current of each power component and the preset current of each power component.

[0023] In one possible implementation, the duty cycle generating unit includes a plurality of duty cycle generating components, the duty cycle generating components including:

[0024] The first subtractor is used to determine the first current difference between the current of the corresponding power component and the preset current.

[0025] The first integrator is used to integrate the first current difference to obtain the corresponding duty cycle.

[0026] In one possible implementation, the current generating unit includes:

[0027] The first accumulator is used to determine the first current sum corresponding to the current of each power component;

[0028] The second accumulator is used to determine the second current sum of the preset currents corresponding to each power component;

[0029] The second subtractor is used to determine the first current and the difference between the first current and the second current.

[0030] The second integrator is used to integrate the second current difference to obtain the integrated value;

[0031] A multiplier is used to perform the multiplication operation of the second current and the target coefficient to obtain an intermediate value;

[0032] An adder is used to perform the addition operation between the intermediate value and the integral value to determine the magnitude of the target current.

[0033] In one possible implementation, the switching signal generation unit is a PWM signal generator.

[0034] In one possible implementation, the power module is a solid oxide battery (SOC), the power assembly is a SOC stack, the SOC stack includes multiple stacked individual cells, each individual cell being made of ceramic material, and the power module further includes:

[0035] The hot box housing contains all the SOC stacks.

[0036] The steam intake manifold and multiple steam intake manifolds are provided. Steam enters the heat box body through the steam intake manifold and is then distributed to the corresponding SOC stacks through the various steam intake manifolds.

[0037] The system includes an air intake manifold and multiple air intake manifolds. Air enters the heat box through the air intake manifold and is then distributed to the corresponding SOC stacks through the various air intake manifolds.

[0038] Hydrogen outlet main pipe and multiple hydrogen outlet manifolds, wherein the hydrogen discharged from each SOC stack is collected in the hydrogen outlet main pipe after passing through the respective hydrogen outlet manifolds and then discharged from the heat box body.

[0039] The system includes a main air outlet pipe and multiple air outlet manifolds. Air discharged from each SOC stack is collected through the respective air outlet manifolds and then discharged from the heat box housing.

[0040] In one possible implementation, the power assembly includes any one or a combination of a SOC stack, an electrolyzer, a fuel cell, and a lithium battery.

[0041] In one possible implementation, the transistor includes any one of a bipolar junction transistor (BJT), a field-effect transistor (MOSFET), or an insulated gate bipolar transistor (IGBT).

[0042] According to one aspect of this disclosure, a power supply system is provided, the system including the active balancing circuit that realizes a constant transfer current of the power module.

[0043] The active balancing circuit of this embodiment measures the electrical parameters of each power component through a measurement unit, generates a switch control signal and a target current based on the electrical parameters of each power component and preset electrical parameters through a signal generation unit, controls the conduction state of each switch unit through the switch control signal, and configures the power supply current of the power supply through the target current. This enables current balancing of each power component in the power module, constant current transfer of the power module, and independent decoupling control of each power component. It has high current balancing capability, high control efficiency, and can effectively improve the uniformity of the power module.

[0044] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Other features and aspects of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0045] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the specification, serve to illustrate the technical solutions of this disclosure.

[0046] Figure 1 A schematic diagram of a solid oxide battery stack tower structure is shown.

[0047] Figure 2 A schematic diagram of a common series active balancing topology used in the field of lithium batteries is shown.

[0048] Figure 3 A schematic diagram of an active balancing circuit for implementing a constant transfer current of a power module according to an embodiment of the present disclosure is shown.

[0049] Figure 4a , Figure 4b A schematic diagram of the framework structure of an embodiment of the present disclosure applied to a solid oxide battery (SOC) is shown.

[0050] Figure 5 A schematic diagram of a signal generation unit according to an embodiment of the present disclosure is shown.

[0051] Figure 6a A schematic diagram of the duty cycle generating component in the duty cycle generating unit is shown.

[0052] Figure 6b A schematic diagram of a current generating unit according to an embodiment of the present disclosure is shown.

[0053] Figure 6c A schematic diagram of the switching signal generation unit is shown when the number of power components is 3. Figure 6d A schematic diagram of the switch control signal generated by the switch signal generation unit when the number of power components is 3 is shown.

[0054] Figure 7 A circuit analysis diagram of the power module and active balancing circuit is shown.

[0055] Figure 8 The diagram shows a simulation model of the power module and active balancing circuit when the power components are 3.

[0056] Figure 9a This diagram illustrates the control effect of the stack current when all stacks are consistent in the electrolysis mode of the power module.

[0057] Figure 9b This diagram illustrates the control effect of inductor current when all fuel cells are aligned in electrolysis mode.

[0058] Figure 9c This diagram illustrates the control effect of the duty cycle of the switch-off when all stacks of the power module are in the same state in electrolysis mode.

[0059] Figure 9d This diagram illustrates the control effect of the stack current when all stacks are consistent in the power generation mode.

[0060] Figure 10a This diagram illustrates the control effect of the stack current when the internal resistance of the series branches of the power module is inconsistent in electrolysis mode.

[0061] Figure 10b This diagram illustrates the effect of the duty cycle control when the series branch resistances of the power module are inconsistent in electrolysis mode.

[0062] Figure 10c This diagram illustrates the control effect of the stack current when the voltage sources of the series branches of the power module are inconsistent in electrolysis mode.

[0063] Figure 10d This diagram illustrates the control effect of the duty cycle of the switch-off when the voltage sources of the series branches of the power module are inconsistent in the power generation mode.

[0064] Figure 11 A schematic diagram of the finite element model of the stack used to verify the effect of current balancing is shown.

[0065] Figure 12a It shows Figure 11 The model shown is a schematic diagram illustrating the normalized steam flow rate changes of each fuel cell stack after the generation of uneven airflow distribution.

[0066] Figure 12b It shows Figure 11 The model shown is a schematic diagram simulating the voltage changes of each fuel cell stack after the generation of uneven airflow distribution.

[0067] Figure 12c It shows Figure 11 The diagram shown is a schematic representation of the maximum temperature change of each fuel cell stack after the generation of uneven airflow distribution.

[0068] Figure 12d It shows Figure 11 The diagram shown illustrates the minimum temperature change of each fuel cell stack after the generation of uneven airflow distribution.

[0069] Figure 13a It shows Figure 11 The diagram shown illustrates the current changes in each fuel cell stack after the active balancing circuit is introduced.

[0070] Figure 13b It shows Figure 11 The diagram shown illustrates the voltage changes of each stack after the active balancing circuit is introduced.

[0071] Figure 13c It shows Figure 11 The diagram shown illustrates the maximum temperature change of each fuel cell stack after the introduction of the active balancing circuit.

[0072] Figure 13d It shows Figure 11 The diagram shown illustrates the minimum temperature change of each fuel cell stack after the introduction of the active balancing circuit. Detailed Implementation

[0073] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0074] In the description of this disclosure, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0075] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise expressly specified.

[0076] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0077] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0078] In this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, in this disclosure, the term "at least one" means any combination of at least two of any one or more of a plurality of elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0079] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0080] Please see Figure 3 , Figure 3 A schematic diagram of an active balancing circuit for implementing a constant transfer current of a power module according to an embodiment of the present disclosure is shown.

[0081] like Figure 3 As shown, the power module 120 includes n power components 1210, and the active balancing circuit includes n+1 inductors (L1~L...). n+1The system includes n switching units 20, a capacitor C, a measurement unit 30, and a signal generation unit 40. Each switching unit 20 includes a transistor (S...). i That is, S1~S n ) and diodes (D i That is, D1~D n The first terminal of the transistor is connected to the cathode of the diode as the first terminal of the switching unit 20, and the second terminal of the transistor is connected to the anode of the diode as the second terminal of the switching unit 20.

[0082] The positive and negative terminals of the power module 120 are connected to the power supply 110. The positive terminal of the first power component 1210 among the n power elements 1210 serves as the positive terminal of the power module 120, and the negative terminal of the last power component 1210 serves as the negative terminal of the power module 120.

[0083] The positive terminal of the i-th power component 1210 is connected to the first terminal of the i-th inductor. The negative terminal of the i-th power component 1210 is connected to the first terminal of the (i+1)-th inductor and the positive terminal of the (i+1)-th power component 1210. The second terminal of the i-th inductor is connected to the first terminal of the transistor and the cathode of the diode in the i-th switching unit 20. The second terminal of the i-th switching unit 20 is connected to the first terminal of the (i+1)-th switching unit 20. There is a one-to-one correspondence between the switching unit 20 and the power component 1210, where 1 ≤ i ≤ n-1 and i and n are both integers.

[0084] The first terminal of capacitor C is connected to the first terminal of the first switching unit 20 and the second terminal of the first inductor, and the second terminal of capacitor C is connected to the second terminal of the last switching unit 20 and the second terminal of the last inductor.

[0085] The measuring unit 30 is connected to the first end of each inductor and is used to measure the electrical parameters of each power component 1210.

[0086] The signal generation unit 40 is connected to the measurement unit 30, the control terminals of each transistor, and the power supply 110, and is used for:

[0087] Based on the electrical parameters of each power component 1210 and preset electrical parameters, a switch control signal and a target current are generated. The switch control signal acts on the control terminal of each transistor, and the target current is used to configure the power supply current of the power supply 110.

[0088] The active balancing circuit of this embodiment measures the electrical parameters of each power component 1210 by the measurement unit 30, and generates a switch control signal and a target current by the signal generation unit 40 based on the electrical parameters of each power component 1210 and preset electrical parameters. The switch control signal is used to control the conduction state of each switch unit 20, and the target current is used to configure the supply current of the power supply 110. This enables current balancing of each power component 1210 in the power module 120, constant current transfer of the power module 120, and independent decoupling control of each power component 1210. It has high current balancing capability, high control efficiency, and can effectively improve the uniformity of the power module 120.

[0089] This disclosure does not limit the specific type of the power module 120, nor does it limit the specific implementation method or number of the power components 1210. Those skilled in the art can set it according to actual conditions and needs. For example, the power module 120 can be a solid oxide battery (SOC) or other electrochemical energy conversion devices that need to achieve constant current transfer, such as an electrolyzer or a fuel cell. Of course, the active balancing circuit of this disclosure can also be applied to lithium battery systems or other types of battery systems to achieve active current balancing.

[0090] This disclosure uses the power module 120 as an example of a solid oxide battery (SOC).

[0091] Please see Figure 4a , Figure 4b , Figure 4a , Figure 4b A schematic diagram of the framework structure of an embodiment of the present disclosure applied to a solid oxide battery (SOC) is shown.

[0092] In one possible implementation, such as Figure 4a , Figure 4b The power module 1210 shown is a SOC (System-on-Chip) stack, which includes multiple stacked individual cells (each cell connected in series). This embodiment does not limit the material of the individual cells; for example, the individual cells may be made of ceramic material. The power module 120 may also include:

[0093] The hot box housing contains all the SOC stacks.

[0094] The steam intake manifold and multiple steam intake manifolds are provided. Steam enters the heat box body through the steam intake manifold and is then distributed to the corresponding SOC stacks through the various steam intake manifolds.

[0095] The system includes an air intake manifold and multiple air intake manifolds. Air enters the heat box through the air intake manifold and is then distributed to the corresponding SOC stacks through the various air intake manifolds.

[0096] Hydrogen outlet main pipe and multiple hydrogen outlet manifolds, wherein the hydrogen discharged from each SOC stack is collected in the hydrogen outlet main pipe after passing through the respective hydrogen outlet manifolds and then discharged from the heat box body.

[0097] The system includes a main air outlet pipe and multiple air outlet manifolds. Air discharged from each SOC stack is collected through the respective air outlet manifolds and then discharged from the heat box housing.

[0098] For example, such as Figure 4a As shown, the main current I flowing into the power tower (power module 120) is... tot Power is supplied by a single power source 110. Based on this, the active balancing circuit connects the positive and negative leads of all series-connected fuel cells (energy components 1210) in the stack to the active balancing circuit via the bypass current. The active balancing circuit controls the magnitude of the bypass current, thereby achieving independent control of the current in each fuel cell stack. Because the bypass current is relative to the main current I... tot The value is relatively small, so the newly added bypass lead can use wires with a smaller cross-sectional area, which is less expensive, and the active balancing circuit will not generate too much heat loss.

[0099] For example, for a stack containing n series-connected SOC stacks, the active balancing circuit of this disclosure embodiment includes n+1 inductors L i n transistors S i n diodes D connected in antiparallel to the transistor i And one capacitor C.

[0100] In this disclosure, the type of transistor is not limited. The required transistor type should be selected based on specific switching frequency, current / voltage, and other parameters. After selecting the appropriate transistor type, the first terminal, second terminal, and control terminal of the transistor can be determined according to specific circumstances. Types include bipolar junction transistors (BJTs), metal-oxide semiconductor field-effect transistors (MOSFETs), and insulated-gate bipolar transistors (IGBTs). This disclosure uses an IGBT as an example. For instance, if a MOSFET is selected, the first terminal is the drain (D), the second terminal is the source (S), and the control terminal is the gate (G). If an IGBT is selected, the first terminal is the collector (C), the second terminal is the emitter (E), and the control terminal is the gate (G).

[0101] For example, each inductor can be connected in series with the leads of the stack. As can be seen from the component characteristics of inductors, the current through an inductor will not change abruptly. Therefore, this structural design ensures that the current on the leads of the stack will not change abruptly, and thus ensures that the current through the stack will not change abruptly, thereby achieving constant current transfer. By controlling the magnitude of the transfer current, independent decoupling control of the current of each stack in the stack can be achieved.

[0102] In one possible implementation, the switch control signal may include the transistor control signal of the transistor in each switch unit 20, wherein the duty cycle of the transistor control signal being turned off is positively correlated with the current magnitude of the corresponding power component 1210.

[0103] This disclosure does not limit the specific implementation of the signal generation unit 40 and the measurement unit 30. Those skilled in the art can configure them according to actual conditions and needs, as long as the corresponding functions are achieved. For example, the signal generation unit 40 may include a processing component. In one example, the processing component includes, but is not limited to, a separate processor, discrete components, or a combination of a processor and discrete components. The processor may include a controller in an electronic device with instruction execution capabilities. The processor can be implemented in any suitable manner, for example, by one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components. Within the processor, the executable instructions can be executed through hardware circuits such as logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers.

[0104] Of course, the signal generation unit 40 can be a discrete device, as illustrated below.

[0105] Please see Figure 5 , Figure 5 A schematic diagram of a signal generation unit 40 according to an embodiment of the present disclosure is shown.

[0106] In one possible implementation, the electrical parameters may include current, voltage, etc. This disclosure uses current as an example for illustration.

[0107] In one possible implementation, such as Figure 5 As shown, the signal generation unit 40 may include:

[0108] Duty cycle generating unit 410 is used to determine the corresponding duty cycle based on the current of each power component 1210 and the preset current.

[0109] The switch signal generation unit 420 is used to generate the switch control signal according to each duty cycle and a preset sawtooth wave signal.

[0110] The current generating unit 430 is used to determine the target current (I) based on the current of each power component 1210 and the preset current of each power component 1210. tot ).

[0111] The method for obtaining the preset current of each power component 1210 in the embodiments of this disclosure is not limited. For example, the preset current can be given directly from the outside, generated by a dedicated control circuit, or stored in memory in advance and called directly from memory when needed. Those skilled in the art can choose the appropriate processing method according to the actual situation and needs.

[0112] In one example, memory may include a computer-readable storage medium, which can be a tangible device capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), programmable read-only memory (PROM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage medium as used herein is not to be construed as a transient signal itself, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0113] Please see Figure 6a , Figure 6a A schematic diagram of the duty cycle generating component 4110 in the duty cycle generating unit 410 is shown.

[0114] In one possible implementation, the duty cycle generating unit 410 includes a plurality of duty cycle generating components 4110, such as... Figure 6a As shown, the duty cycle generating component 4110 may include:

[0115] The first subtractor 41110 is used to determine the current I of the corresponding power component 1210. i and preset current I i，ref The first current difference;

[0116] The first integrator 41120 is used to integrate the first current difference to obtain the corresponding duty cycle d. i .

[0117] For example, such as Figure 6a As shown, for any one of the fuel cell stacks i (i = 2, 3, ..., n), the measured current Ii and current reference value I i，ref The difference is passed through an integral element, and the output is used as the duty cycle d. i The presence of the integrator ensures that the error between the measured and reference values ​​of the branch current is zero after the circuit reaches steady state, thus achieving error-free current control.

[0118] Please see Figure 6b , Figure 6b A schematic diagram of a current generating unit 430 according to an embodiment of the present disclosure is shown.

[0119] In one possible implementation, such as Figure 6b As shown, the current generating unit 430 includes:

[0120] The first accumulator 4310 is used to determine the first current sum corresponding to the current (measured current) of each power component 1210;

[0121] The second accumulator 4320 is used to determine the second current sum of the preset currents corresponding to each power component 1210;

[0122] The second subtractor 4330 is used to determine the first current and the difference between the first current and the second current;

[0123] The second integrator 4340 is used to integrate the second current difference to obtain the integrated value;

[0124] Multiplier 4350 is used to implement the second current sum and the target coefficient (K) p The multiplication operation is performed to obtain the intermediate value;

[0125] Adder 4360 is used to perform the addition operation of the intermediate value and the integral value to determine the magnitude of the target current.

[0126] This disclosure embodiment addresses the target coefficient (K) p The specific size is not limited, and those skilled in the art can set it according to the actual situation and needs.

[0127] Due to the duty cycles d1, d2, ..., d of each transistor n The sum of these values ​​is 1, resulting in only n-1 degrees of freedom. Therefore, it is impossible to achieve error-free control of the currents of n fuel cell stacks simultaneously by controlling only the duty cycle. Therefore, it is necessary to find additional degrees of freedom to achieve error-free control of the current of fuel cell stack 1 (the first fuel cell stack). This disclosure proposes the following embodiments... Figure 6b The PI controller shown adjusts the total current I... tot To achieve error-free control of the current I1 of fuel cell stack 1.

[0128] For example, in specific implementation, Figure 6bThe current generation unit 430 shown uses the average value of all reference values ​​of the stack currents as I. tot The baseline value is used as the basis, and the difference between the sum of all stack current reference values ​​and the sum of the measured current values ​​is integrated through an integrator to determine I. tot Corrections are made. The presence of the integrator ensures that the sum of all measured current values ​​of the fuel cell stack after the circuit reaches steady state follows the sum of the reference values.

[0129] Due to the stack currents I2, I3, ..., I n It has been approved Figure 6b The controller shown achieves zero-error control, therefore through Figure 6b The current generating unit 430 shown can also achieve error-free control of the fuel cell current I1.

[0130] Of course, the above description of the duty cycle generating unit 410 and the current generating unit 430 is exemplary and should not be considered as a limitation of this disclosure. In other embodiments, those skilled in the art can also adapt them based on the principle of a PI controller. Figure 6a , Figure 6b The implementation shown has been modified.

[0131] In one possible implementation, the switching signal generation unit 420 is a PWM (Pulse Width Modulation) signal generator.

[0132] The PWM signal generator can be implemented using methods found in related technologies, and this disclosure does not limit the specific implementation of the embodiments.

[0133] Please see Figure 6c , Figure 6d , Figure 6c A schematic diagram of the switching signal generation unit 420 is shown when the number of power components 1210 is 3. Figure 6d A schematic diagram of the switch control signal generated by the switch signal generation unit 420 is shown when the number of power components 1210 is 3.

[0134] For example, such as Figure 6c As shown, the PWM signal generator receives the duty cycle d. i The PWM signal generator compares the sawtooth wave signal s(t) with a period of Ts and a value range of [0,1] with the duty cycle value input to the PWM signal generator to generate the trigger signal for each switch. The corresponding triggering rules are shown in Table 1.

[0135] Table 1 Triggering Rules

[0136]

[0137] In Table 1, Si The state of the transistor in the i-th switching unit 20 can be determined by the above Table 1 when the sawtooth wave signal s(t) is in the corresponding interval.

[0138] For example, as shown in Table 1, Figure 6d As shown, if d2<s(t)≤d2+d3 is satisfied, then transistor S3 is turned off, and all other transistors are turned on.

[0139] Of course, the above description of the method of generating switch control signals is exemplary and should not be regarded as a limitation of the embodiments of this disclosure. Those skilled in the art can use relevant technologies to generate corresponding switch control signals according to the duty cycle based on actual conditions and needs.

[0140] The above describes the possible implementation methods of the active equalization circuit. The following is a theoretical analysis to introduce the theoretical basis of the active equalization circuit of the present disclosure embodiment.

[0141] Please see Figure 7 , Figure 7 A circuit analysis diagram of the power module 120 and the active balancing circuit is shown.

[0142] It is worth noting that, Figure 3 The active equalization circuit shown has n switching units 20, therefore a total of 2 n A type of switch combination. To simplify analysis, this disclosure simplifies the SOC stack to a voltage source U. i With resistance R i Serial connection, such as Figure 7 As shown.

[0143] Based on this, the embodiments disclosed herein only consider these two. n There are n switch combinations in which exactly one switch is off. Taking transistor S in switch unit 20 as an example... i Taking the case of disconnection as an example, by Figure 7 It can be seen that since the transistors in the other switching units 20 are all in the on state, the capacitor C is directly connected in parallel with the diode D. i On both sides, diode D i It withstands reverse voltage and is also in the off state. In this state, transistor S can be switched on. i Diode D i The transistors and diodes in the remaining switching units 20 are directly removed, and wires are used to replace them. Only the inductor and capacitor C exist in the circuit, making it a linear circuit.

[0144] refer to Figure 7 According to Kirchhoff's laws, the sum of the currents flowing into the balancing circuit is 0, therefore:

[0145]

[0146] Among them, i L,n+1 i represents the current flowing through the (n+1)th inductor. L,i This represents the current flowing through the i-th inductor.

[0147] The inductor current and the stack branch current satisfy the following relationship:

[0148]

[0149] Among them, i i I represents the current of the i-th power unit 1210 (fuel cell stack). tot This indicates the total current flowing into the power module 120.

[0150] Theoretical analysis of the circuit reveals that, under n possible switch combinations where only one switch is open, the circuit satisfies the equations shown in Table 2.

[0151] Table 2 Circuit equations under different switching states

[0152]

[0153] Where L represents the magnitude of each inductor, Ui represents the voltage magnitude of the voltage source corresponding to the i-th power component 1210 (fuel pile), and R i u represents the resistance value corresponding to the i-th power component 1210. C This indicates the magnitude of the voltage across capacitor C.

[0154] Using the inductor current and the voltage across capacitor C as state variables, denoted as x = [i L1 i L2 ,...,i Ln ,u C ] T Taking the voltage and total current of the voltage source as input, denoted as u=[U1,U2,...,U n ,I tot ] T .

[0155] Table 2 can be summarized in the general form shown in the following equation. Here, x′ represents the derivative of the state variable x with respect to time.

[0156] K i x′=A i x+B i u 1.3

[0157] The expressions for each matrix are as follows:

[0158]

[0159] In the above expression, I n For an n*n identity matrix, 1 n×n Let e ​​be an n*n matrix with all elements equal to 1. j It is a unit column vector of length n, with the j-th element being 1 and the rest being 0.

[0160] Assume the duty cycle of transistor Si being off during one cycle is d. i Since this embodiment only considers n switch combinations where one and only one switch is off, the sum of the duty cycles of the n transistors is 1, which satisfies:

[0161]

[0162] Assume that the change in the state quantity when transistor Si is turned off during one switching cycle is Δx. i Since the switching period is very short, the derivative can be replaced by the rate of change, i.e., Δx = x′Δt. Therefore, combining with Equation 1.3, the following equation holds, where T s This represents the switching cycle.

[0163] K i Δx i =d i T s (A i x+B i u), i = 1, ..., n 1.8

[0164] When the circuit reaches steady state, the net change in state variables within one cycle should be 0, that is... Therefore, the following equation holds true, where This represents the average value of the state variables after the circuit reaches steady state.

[0165]

[0166] By solving this system of linear equations, we can obtain...

[0167]

[0168] based on The solution can be used to calculate the fluctuation value of the state variable within one switching cycle, that is:

[0169]

[0170] Formula 1.11 can be used to optimize the design of circuit parameters, including the selection of inductance, capacitance C, and switching cycle parameters.

[0171] To guide controller design, the relationship between the duty cycle and the transfer current (i.e., inductor current) needs to be known. Equation 1.10 is quite complex and difficult to derive an analytical expression from. Therefore, this embodiment considers the simplest case, where the voltage sources and internal resistances of the series branches are equal, i.e., U1 = U2 = ... = U n =U0, R1=R2=...=R n =R0, where U0 represents the voltage magnitude of each voltage source, and R0 represents the magnitude of each resistor. Under this assumption, the relationship between the average inductor current and the duty cycle can be derived by solving Equation 1.10 as follows:

[0172]

[0173] From the above equation, it can be seen that for inductor i, as the duty cycle d of switch i is turned off... i The increase of inductance i leads to the current I flowing through inductor i. L,i As the current decreases, the current drawn from the main circuit by inductor i decreases, and the current in the i-th series branch will increase accordingly. This disclosure utilizes this feature to design a signal generation unit 40 to achieve current tracking control, thereby realizing current balancing among the various power components 1210.

[0174] The active balancing circuit is simulated below using an example of 3 power components 1210 to verify its effectiveness.

[0175] Please see Figure 8 , Figure 8 A schematic diagram of the simulation model structure of the power module 120 and the active balancing circuit is shown when the number of power components 1210 is 3.

[0176] like Figure 8 As shown, this embodiment of the present disclosure uses a stack containing three series-connected fuel cells as an example to verify the effectiveness of the designed active balancing circuit through simulation. This embodiment utilizes an equivalent circuit model of a voltage source and a resistor connected in series to simulate the electrical characteristics of the SOC fuel cell stack. The voltage source corresponds to the Nernst voltage of the stack, and the resistor corresponds to the equivalent resistance corresponding to the ohmic losses and activation losses of the electrochemical reaction in the stack. The inductor size is chosen to be 30μH, the capacitor C size is chosen to be 10μF, and the switching frequency is chosen to be 1MHz.

[0177] Please see Figure 9a , Figure 9a The diagram shows the control effect of the stack current when all stacks are consistent in the electrolysis mode.

[0178] Please see Figure 9b , Figure 9bA schematic diagram showing the control effect of inductor current in power module 120 when all stacks are consistent in electrolysis mode is shown.

[0179] Please see Figure 9c , Figure 9c The diagram illustrates the control effect of the duty cycle of the switch-off when all stacks of the power module 120 are in the same electrolysis mode.

[0180] Please see Figure 9d , Figure 9d A schematic diagram of the control effect of the stack current is shown when the power module 120 is consistent across all stacks in the power generation mode.

[0181] Assume that all series-connected stacks are identical, i.e., U1 = U2 = U3 = 30V, R1 = R2 = R3 = 0.1Ω.

[0182] First, the current decoupling control capability of the circuit is verified. The simulation results are as follows: Figure 9a As shown.

[0183] Figure 9a The dashed line represents the reference current value, while the solid line of the corresponding color represents the actual current of the three series-connected fuel cells. The black line represents the input current I from the external DC power supply. tot Size.

[0184] from Figure 9a It can be observed that after the current reference value changes, the current of the corresponding stack can track the reference value within 1 second, demonstrating good dynamic performance. Furthermore, the circuit can arbitrarily adjust the relative magnitude of the currents of the three stacks, enabling decoupling control of the currents of the series stacks.

[0185] Figure 9a The current in the initial stage showed some oscillations, mainly due to the improper selection of the initial value of the capacitor C voltage during simulation. The simulation can be optimized by selecting a suitable initial capacitor C voltage.

[0186] from Figure 9b It can be observed that the bypass current through the inductor is an order of magnitude smaller than the main current through the fuel cell stack. This results in less additional switching loss caused by the bypass current through the active balancing circuit, while also reducing the cost of the bypass leads and the selection requirements for the switching transistors, making the proposed circuit easier to implement in engineering.

[0187] from Figure 9c Comparing the stack current and the inductor current reveals that the duty cycle is negatively correlated with the inductor current and positively correlated with the stack current. This proves the correctness of the theoretical derivation above and also demonstrates the effectiveness of the signal generation unit 40.

[0188] Figures 9a-9cThis demonstrates the reactor tower operating in electrolysis mode, converting electrical energy into hydrogen energy. A key feature of SOC technology is its ability to operate in both electrolysis and power generation modes. When the reactor tower current direction is reversed, the tower converts hydrogen energy into electrical energy; in this case, the proposed active balancing circuit can still achieve the function of controlling current bypass, such as... Figure 9d As shown.

[0189] from Figure 9d It can be observed that, under this operating condition, the proposed active balancing circuit can still achieve independent control of the current magnitude of each series-connected fuel cell stack. It should be noted that the signal generation unit 40 proposed in this embodiment is based on... Figure 7 Designed for the specified positive direction, all voltage and current measurements and reference values ​​are signed numbers. For the opposite direction, those skilled in the art can modify them according to the actual situation and needs.

[0190] In the foregoing introduction, to obtain the analytical expression for the relationship between duty cycle and transfer current, it was assumed that the voltage sources and resistors of the three series branches were identical. However, when the resistors or voltage sources of the three series branches are inconsistent, the derived expression 1.12 will no longer be accurate. Nevertheless, Equation 1.12 is used to guide the design of the signal generation unit 40, and the effectiveness of the designed signal generation unit 40 depends solely on the conclusion that "the switch turn-off duty cycle and the corresponding stack current are positively correlated." When the three series branches are inconsistent, it is reasonable to assume that the above conclusion will not change directionally.

[0191] To verify this, the performance of the signal generation unit 40 was tested under conditions of inconsistent resistance in this embodiment. Still using... Figure 8 The simulation model shown assumes U1 = U2 = U3 = 30V, R1 = 0.08Ω, R2 = 0.1Ω, and R3 = 0.12Ω.

[0192] Please see Figure 10a , Figure 10a A schematic diagram showing the control effect of the stack current when the internal resistance of the series branches of the power module 120 is inconsistent in electrolysis mode is shown.

[0193] Please see Figure 10b , Figure 10b The diagram illustrates the control effect of the duty cycle of the switch-off when the internal resistance of the series branches of the power module 120 is inconsistent in electrolysis mode.

[0194] Please see Figure 10c , Figure 10c A schematic diagram showing the control effect of the stack current when the voltage sources of the series branches of the power module 120 are inconsistent in electrolysis mode is shown.

[0195] Please see Figure 10d , Figure 10d The diagram illustrates the control effect of the duty cycle of the switch-off when the voltage sources of the series branches of the power module 120 are inconsistent in the power generation mode.

[0196] Appendix Figure 10a In the diagram, the dashed lines represent the reference current magnitudes for each fuel cell stack, the corresponding solid lines represent the actual current magnitudes for the stacks, and the black solid line represents the total current I. tot Size.

[0197] from Figure 10a It can be observed that, except for the current oscillation that occurred in the initial stage, the current tracking effect of the signal generation unit 40 did not change significantly in other cases. This indicates that the designed signal generation unit 40 can still effectively control the equalization circuit to achieve the current tracking function.

[0198] like Figure 10b As shown, it can be observed that although the current in each series-connected stack is equal within the initial 0-1s, the duty cycles after stabilization are not equal. The stack with higher internal resistance corresponds to a higher duty cycle when the switch is turned off. The simulation sets the initial duty cycle of the controller output to 33%, which differs from the steady-state state. This difference causes oscillations in the stack current at the initial moment. In the subsequent time period, the relationship between the duty cycle and the corresponding stack current remains unchanged; the larger the duty cycle, the larger the corresponding stack current, and the two still exhibit a positive correlation.

[0199] Figure 10c This simulation result takes into account the case where the voltage source magnitudes of different series branches are inconsistent. It still uses... Figure 7 The simulation model shown assumes U1 = 29V, U2 = 30V, U3 = 31V, and R1 = R2 = R3 = 0.1Ω. Figure 10a Similarly, except for the current oscillation that occurred in the initial stage, the current tracking effect of the controller did not change significantly in other cases, which shows that the designed controller can still effectively control the equalization circuit to achieve the current tracking function.

[0200] Further plotting the curves showing the change in duty cycle of different switches during the simulation process, such as... Figure 10d As shown, it can be observed that although the current in each series-connected stack is equal within the initial 0-1s, the duty cycles after stabilization are not equal. The larger the voltage source of the stack, the higher the corresponding duty cycle when the switch is turned off. The simulation sets the initial state of the controller output duty cycle to 33%, which differs from the steady state. This difference causes the stack current to oscillate at the initial moment. In the subsequent time period, the relationship between the duty cycle and the corresponding stack current does not change; the larger the duty cycle, the larger the corresponding stack current, and the two still show a positive correlation.

[0201] Please see Figure 11 , Figure 11 A schematic diagram of the finite element model of the stack used to verify the effect of current balancing is shown.

[0202] The preceding section used an equivalent circuit model of the fuel cell stack to verify the current transfer capability of the designed active balancing circuit for the fuel cell tower. The following section will further verify the ability of current transfer to improve the non-uniformity of the fuel cell tower based on a finite source model that can more accurately simulate the operating characteristics of the fuel cell tower. The finite element model of the fuel cell tower used is as follows: Figure 11 As shown, it comprises four electrically connected fuel cells (Stack1-4), with the stacks placed inside a thermal chamber. This model can simulate the spatial distribution of temperature, current, voltage, and material concentration during stack operation.

[0203] Please see Figure 12a , Figure 12a It shows Figure 11 The model shown is a schematic diagram illustrating the normalized steam flow rate changes of each fuel cell stack after the generation of uneven airflow distribution.

[0204] Please see Figure 12b , Figure 12b It shows Figure 11 The model shown is a schematic diagram simulating the voltage changes of each fuel cell stack after the generation of uneven airflow distribution.

[0205] Please see Figure 12c , Figure 12c It shows Figure 11 The diagram shown is a schematic representation of the maximum temperature change of each fuel cell stack after the generation of uneven airflow distribution.

[0206] Please see Figure 12d , Figure 12d It shows Figure 11 The diagram shown illustrates the minimum temperature change of each fuel cell stack after the generation of uneven airflow distribution.

[0207] Assuming that initially, all four fuel cell stacks operate at a current of 100A in electrolysis mode, and that the initial flow rates and steam distributions are identical across all stacks, the stacks reach a stable operating state under these conditions. First, this model is used to simulate the changes in stack operating characteristics after the generation of uneven steam distribution, such as... Figures 12a-12d As shown. Figure 12a As shown in the simulation, it is assumed that the normalized steam flow rate of each fuel cell stack is inconsistent, with fuel cell stack 4 receiving the most steam and fuel cell stack 1 receiving the least. Under these circumstances, [the following is a continuation of the simulation]... Figure 12b It can be observed that with the occurrence of uneven steam distribution, the stack voltage immediately becomes inconsistent. Stack 1, with insufficient steam, has the highest voltage, exceeding that of stack 4 by more than 1V. This is mainly due to the increased overvoltage caused by insufficient steam distribution. Figure 12c and Figure 12d It is known that the uneven distribution of steam also leads to temperature inconsistencies among different fuel cell stacks within the reactor tower. The hot spot temperature of stack 1, which suffers from insufficient steam, can be 15°C higher than that of stack 4, which has sufficient steam. This unevenness will result in inconsistent degradation rates among the different fuel cell stacks within the reactor tower, further exacerbating the inconsistency and jeopardizing their lifespan. Furthermore, due to… Figure 12b It was also found that after the airflow distribution became uneven, the average voltage of the four fuel cells increased slightly, indicating that the energy consumption of the stack increased and the operating efficiency decreased.

[0208] Figures 12a-12d The illustration shows the case where the active balancing circuit of this disclosure is not used to actively balance the current of each fuel cell stack. The following describes the case where the active balancing circuit of this disclosure is used to actively balance the current of each fuel cell stack.

[0209] This embodiment of the disclosure, by employing an active balancing circuit to independently control the current magnitude of each series-connected fuel cell stack, can effectively improve... Figures 12a-12d The inconsistencies shown are illustrated in the simulation results. Figures 13a-13d As shown.

[0210] Please see Figure 13a , Figure 13a It shows Figure 11 The diagram shown illustrates the current changes in each fuel cell stack after the active balancing circuit is introduced.

[0211] Please see Figure 13b , Figure 13b It shows Figure 11 The diagram shown illustrates the voltage changes of each stack after the active balancing circuit is introduced.

[0212] Please see Figure 13c , Figure 13c It shows Figure 11 The diagram shown illustrates the maximum temperature change of each fuel cell stack after the introduction of the active balancing circuit.

[0213] Please see Figure 13d , Figure 13d It shows Figure 11 The diagram shown illustrates the minimum temperature change of each fuel cell stack after the introduction of the active balancing circuit.

[0214] in, Figures 13a-13d The initial moment represents Figures 12a-12d The simulation structure shown reaches a steady state.

[0215] Depend on Figure 13aIt is known that the active balancing circuit starts working at the initial moment, adjusting the current magnitude of each fuel cell stack. This active balancing circuit quickly reduces the current of fuel cell stack 1, which has insufficient steam, and increases the current of fuel cell stack 4, which has sufficient steam, thereby reducing the voltage difference between the fuel cell stacks. At the same time, since the current values ​​of each fuel cell stack are still around 100A, with a deviation of less than 10A, it indicates that the bypass current value through the balancing circuit is very small.

[0216] Depend on Figure 13b It can be seen that after the equalization circuit is working, the voltage difference between the four fuel cells is reduced to about 0.1V. As the voltage difference decreases, the heat dissipation power of each fuel cell gradually becomes more consistent.

[0217] Depend on Figure 13c , Figure 13d As can be seen, the temperature of each fuel cell stack gradually tends to equalize. This result proves the effectiveness of the proposed active balancing circuit.

[0218] To address the challenges of inconsistency and reduced reliability in State of Charge (SOC) as it scales up from individual battery stacks to a tower, this disclosure proposes a novel approach to improve tower consistency by independently adjusting the current magnitude of each series-connected battery stack using an equalization control circuit. Based on this approach, this disclosure addresses the limitations of existing lithium-ion battery series equalization circuit topologies, which cannot achieve constant current transfer and are unsuitable for SOCs, by designing a novel active equalization circuit topology capable of constant current transfer. For this circuit topology, this disclosure designs a switching modulation mode and derives the relationship between the switching duty cycle and the transfer current magnitude through theoretical analysis. Based on this, a controller for the active equalization circuit is constructed to ensure that the current of each series-connected battery stack in the tower can independently track its respective reference value.

[0219] This disclosure presents simulation verification of the designed active balancing circuit and controller. The verification shows that the circuit can effectively achieve constant current transfer, and can still achieve current transfer even when there is inconsistency in the series-connected fuel cell stacks. Furthermore, the designed controller is applicable not only to the electrolysis mode of SOC but also to the power generation mode. Through simulation of a three-dimensional finite element model of the stack, this disclosure verifies that the proposed circuit and controller can effectively improve the uniformity of temperature distribution inside the stack when steam distribution is inconsistent, and reduce voltage deviation between different series-connected fuel cell stacks. This is beneficial for improving the lifespan and reliability of large-capacity stacks, thereby supporting the engineering scale-up of SOC technology.

[0220] As described above, this disclosure proposes a novel active balancing circuit topology capable of achieving constant transfer current, applicable to current balancing in SOC stacks and other power modules 120. For this topology, the invention designs a modulation strategy for the circuit switching state, derives a formula describing the relationship between transfer current and switching duty cycle based on an average value circuit model, and designs a duty cycle controller using the relationship between transfer current and duty cycle shown by this formula to achieve independent decoupled control of different stack currents in the stack.

[0221] The embodiments disclosed herein verify the function of the equalization circuit using an equivalent circuit model, and also verify through three-dimensional model simulation of the stack that the transfer current can effectively improve the consistency of the stack.

[0222] The contributions of this disclosure include, but are not limited to:

[0223] (1) A novel approach to improve the uniformity of SOC series stack tower by controlling the bypass current was proposed. An active balancing circuit topology capable of achieving constant current transfer was designed. This circuit is suitable for electrochemical energy conversion devices that require constant current transfer, such as electrolyzers and fuel cells. It also has the potential to be applied to lithium battery systems.

[0224] (2) For the designed active equalization circuit, the present invention proposes a corresponding modulation method and builds a control system. The function of the proposed circuit is tested by simulation, and it is verified that the active equalization circuit can effectively improve the uniformity of the stack by changing the current magnitude of different series stacks in the stack.

[0225] According to one aspect of this disclosure, a power supply system is provided, the system including the active balancing circuit that realizes a constant transfer current of the power module 120.

[0226] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used in the embodiments of this disclosure is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable other those skilled in the art to understand the embodiments disclosed in this disclosure.

Claims

1. An active balancing circuit for achieving constant transfer current in a power module, characterized in that, The power module includes n electrically connected power components. The circuit includes: n+1 inductors, n switching units, a capacitor, a measurement unit, and a signal generation unit. Each switching unit includes a transistor and a diode. The first terminal of the transistor is connected to the cathode of the diode as the first terminal of the switching unit, and the second terminal of the transistor is connected to the anode of the diode as the second terminal of the switching unit. The positive and negative terminals of the power module are connected to a power supply. The positive terminal of the first power component among the n power components serves as the positive terminal of the power module, and the negative terminal of the last power component serves as the negative terminal of the power module. The positive terminal of the i-th power component is connected to the first terminal of the i-th inductor, the negative terminal of the i-th power component is connected to the first terminal of the (i+1)-th inductor and the positive terminal of the (i+1)-th power component, and the second terminal of the i-th inductor is connected to the first terminal of the transistor and the cathode of the diode in the i-th switching unit. The second terminal of the i-th switching unit is connected to the first terminal of the (i+1)-th switching unit. Each switching unit corresponds one-to-one with a power component, where 1 ≤ i ≤ n-1 and i and n are both integers. The first terminal of the capacitor is connected to the first terminal of the first switching unit and the second terminal of the first inductor, and the second terminal of the capacitor is connected to the second terminal of the last switching unit and the second terminal of the last inductor. The measuring unit is connected to the first terminal of each inductor and is used to measure the electrical parameters of each power component. The signal generation unit is connected to the measurement unit, the control terminals of each transistor, and the power supply, and is used for: Based on the electrical parameters of each power component and preset electrical parameters, a switch control signal and a target current are generated. The switch control signal acts on the control terminal of each transistor, and the target current is used to configure the power supply current of the power supply.

2. The circuit according to claim 1, characterized in that, The switching control signal includes the transistor control signal of the transistor in each switching unit, and the duty cycle of the transistor control signal being turned off is positively correlated with the current of the corresponding power component.

3. The circuit according to claim 1, characterized in that, The electrical parameters include current, and the signal generation unit includes: The duty cycle generation unit is used to determine the corresponding duty cycle based on the current of each power component and the preset current. A switch signal generation unit is used to generate the switch control signal according to each duty cycle and a preset sawtooth wave signal. A current generating unit is used to determine the target current based on the current of each power component and the preset current of each power component.

4. The circuit according to claim 3, characterized in that, The duty cycle generating unit includes multiple duty cycle generating components, and the duty cycle generating components include: The first subtractor is used to determine the first current difference between the current of the corresponding power component and the preset current. The first integrator is used to integrate the first current difference to obtain the corresponding duty cycle.

5. The circuit according to claim 3, characterized in that, The current generating unit includes: The first accumulator is used to determine the first current sum corresponding to the current of each power component; The second accumulator is used to determine the second current sum of the preset currents corresponding to each power component; The second subtractor is used to determine the first current and the difference between the first current and the second current. The second integrator is used to integrate the second current difference to obtain the integrated value; A multiplier is used to perform the multiplication operation of the second current and the target coefficient to obtain an intermediate value; An adder is used to perform the addition operation between the intermediate value and the integral value to determine the magnitude of the target current.

6. The circuit according to claim 3, characterized in that, The switching signal generation unit is a PWM signal generator.

7. The circuit according to claim 1, characterized in that, The power module is a solid oxide battery (SOC) stack, and the power assembly is an SOC stack. The SOC stack comprises multiple stacked individual cells, each made of ceramic material. The power module further includes: The hot box housing contains all the SOC stacks. The steam intake manifold and multiple steam intake manifolds are provided. Steam enters the heat box body through the steam intake manifold and is then distributed to the corresponding SOC stacks through the various steam intake manifolds. The system includes an air intake manifold and multiple air intake manifolds. Air enters the heat box through the air intake manifold and is then distributed to the corresponding SOC stacks through the various air intake manifolds. Hydrogen outlet main pipe and multiple hydrogen outlet manifolds, wherein the hydrogen discharged from each SOC stack is collected in the hydrogen outlet main pipe after passing through the respective hydrogen outlet manifolds and then discharged from the heat box body. The system includes a main air outlet pipe and multiple air outlet manifolds. Air discharged from each SOC stack is collected through the respective air outlet manifolds and then discharged from the heat box housing.

8. The circuit according to claim 1, characterized in that, The power components include any one or combination of SOC stack, electrolytic cell, fuel cell, and lithium battery.

9. The circuit according to claim 1, characterized in that, The transistor includes any one of a bipolar junction transistor (BJT), a field-effect transistor (MOSFET), or an insulated gate bipolar transistor (IGBT).

10. A power supply system, characterized in that, The system includes the active balancing circuit for achieving constant transfer current of the power module as described in any one of claims 1 to 9.

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