Active equalization circuit suitable for solid oxide battery

Abstract

The invention relates to an active equalization circuit suitable for a solid oxide battery, an electric energy module in the circuit comprises n electric energy assemblies which are electrically connected in series, the circuit comprises n + 1 inductors, n switch units, a capacitor, a measurement unit and a signal generation unit, and the signal generation unit is connected to the measurement unit, control ends of transistors and a power supply, the control module is used for generating switch control signals and target current according to the electric parameters of the electric energy assemblies and preset electric parameters, the switch control signals act on the control ends of the transistors, and the target current is used for configuring power supply current of the electric energy module power supply. According to the embodiment of the invention, the current balance of each electric energy assembly in the electric energy module can be realized, the independent decoupling control of each electric energy assembly is realized, the current balance capability and the control efficiency are high, and the uniformity of the electric energy module can be effectively improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of energy management, and in particular to an active balancing circuit suitable for solid oxide batteries. Background Art

[0002] Green hydrogen can not only be used as a long-term energy storage medium to help the power system absorb large-scale wind and solar volatile renewable energy, but also as a green energy and raw material to help chemical, transportation, metallurgy and other industries that are difficult to reduce carbon emissions to achieve energy conservation and emission reduction. Electrolysis of water to produce hydrogen is an important method for large-scale production of green hydrogen. Among the common technical routes, solid oxide electrolysis (SOE) has the advantage of high hydrogen production efficiency. When there is an external steam supply, its hydrogen production energy consumption can be as low as 3.4kWh / Nm 3 Hydrogen, which is much lower than the currently mature alkaline electrolysis (energy consumption is typically 5kWh / Nm 3 Hydrogen), so it is widely regarded as the next generation of electrolysis technology. In addition to its high efficiency, it also has the unique advantage of being reversible, and is called a solid oxide cell (SOC). In other words, it can work in electrolysis mode (Solid Oxide Electrolysis Cell, SOEC) to convert electrical energy into hydrogen energy, and it can also work 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 still relatively immature and the cost is relatively high, companies at home and abroad have been promoting it commercially. With the increase in production scale, the scale effect will effectively reduce its manufacturing costs and its market competitiveness will gradually increase.

[0003] Capacity expansion is one of the key technical issues facing SOC technology. The single cell of SOC is made of ceramic material with a thickness of less than 1mm. Due to the fragile mechanical properties of ceramic materials, the area of ​​a single cell is difficult to enlarge. The typical value is 150cm 2 The first step to increase the SOC capacity is to stack single cells to form a battery stack. The power of a single battery stack is generally several kilowatts and the voltage is tens of volts. In order to increase the power and voltage and reduce the investment and loss in the power conversion link, further amplification generally requires stacking multiple battery stacks to form a stack tower that is connected in series in the circuit and in parallel in the gas path. Multiple stack towers are then integrated in a heat box to form a module, and finally multiple modules form a large-capacity system. A stack tower structure consisting of three battery stacks in series is shown in Figure 1. Figure 1As shown. After steam and air enter the hot box from a main pipe, they are distributed to different stacks through the manifold. The hydrogen and air produced by the stack reaction are first collected into the main pipe through the manifold, and then flow out of the stack from the main pipe. With the increase in the number of stacks in the stack tower, the consistency of airflow distribution of different stacks is becoming increasingly difficult to ensure, but the current of the electrical series stacks must be equal. Due to the short board effect, the maximum current of the stack tower will be restricted by the stack with the least airflow, resulting in the inability to linearly amplify the power of the stack tower. At the same time, the inconsistency of the stack itself due to manufacturing or degradation will also cause the internal resistance of some stacks to be too large, resulting in local hot spots, and leading to problems such as increased uneven temperature distribution. These gas and heat inhomogeneities will further accelerate the performance degradation of the stack tower and endanger the overall life. Since the stack tower as a whole is in a high temperature environment of about 750°C, no valves or instruments can adapt to such high temperatures, so there is almost no direct control method to improve the gas and heat distribution.

[0004] As the hub of electricity, gas and heat conversion, the fuel cell stack is almost the only controllable component in the hot box. With its hub characteristics, it is possible to use electric control to replace flow control and temperature control, and improve the consistency of the stack tower by changing the current of different fuel cells. For example, when the airflow distribution of multiple fuel cells is uneven, the fuel cell with sufficient airflow distribution has a lower voltage and less heat, while the fuel cell with insufficient airflow distribution has a higher voltage and greater heat, which leads to an increase in the inconsistency of the temperature distribution of the stack tower. At the same time, the maximum current of the stack tower is also limited by the fuel cell with insufficient airflow distribution, which makes the stack tower unable to fully utilize the raw gas and also leads to the attenuation of the maximum power. In this case, if the current of the fuel cell with insufficient airflow distribution is reduced and the current of the fuel cell with sufficient airflow distribution is increased, it may be possible to improve the uniformity of temperature distribution and increase the maximum power of the stack tower.

[0005] The lithium battery field also faces similar balancing problems for series battery packs. Large-scale lithium battery systems also need to be composed of multiple batteries connected in series and parallel. Series batteries are affected by factors such as self-discharge rate and factory inconsistency, and the state of charge (SoC) of the single battery will gradually become inconsistent, resulting in a reduction in the available capacity of the series battery pack. The current solution is to lead out the positive and negative leads of each single cell in the series battery pack, connect an external balancing circuit, and control the charging and discharging of the single cell through the switch in the balancing circuit, or realize the controllable transfer of energy between different batteries or between batteries and battery packs, so as to achieve SoC balancing. Existing balancing circuit topologies include resistor dissipation topology, Fitu capacitor topology, Fitu inductor topology, flyback conversion topology, etc. However, the most essential difference between lithium battery balancing and SOC balancing is that the former needs to balance the state of charge SoC, while the latter needs to balance the current. This difference makes the existing lithium battery balancing circuit adopt an intermittent working mode, and the current through the single lithium battery is fluctuating, and constant current transfer cannot be achieved. The SOC stack needs to operate under a relatively stable current, and the rapidly fluctuating current will pose a great challenge to the durability of the SOC stack.

[0006] It can be seen that the equalization circuit suitable for lithium batteries cannot be directly applied to SOC stacks. The specific reasons are introduced below.

[0007] Common series active balancing topologies used in the field of lithium batteries include controlled resistance balancing topology, Fit capacitor balancing topology, Fit inductor balancing topology, flyback conversion topology, etc. Figure 2 As shown. Among them, the controllable resistance balancing topology ( Figure 2 In (a), each series-connected single cell is connected to a resistor through a switch. By controlling the on and off of the switch, the single cell can be discharged independently. Therefore, as long as the single cell with a high state of charge is discharged, the charge state of different single cells can be balanced; Fit capacitor ( Figure 2 (b)) and the Fitu inductor balanced topology ( Figure 2 In (c), inductors and capacitors are used as energy storage carriers. By controlling the timing of the switch, energy is transferred between adjacent cells, thereby balancing the charge states of different cells. Figure 2 In (d), each single cell is connected to the primary side of a transformer through a switch, and the secondary side of the transformer is also connected to the entire battery pack through a switch. Through the opening and closing combination of the switches, energy transfer between the battery pack and the corresponding single cell can be achieved, thereby achieving balance. Figure 2What is shown are only a few basic balancing topologies. Based on these topologies, many forms of topologies have been derived and developed, which can realize energy transfer between single cells and between single cells and battery packs, thereby achieving the balancing function. The embodiments of the present disclosure will not be described one by one.

[0008] However, the current balancing circuits for lithium batteries cannot be directly applied to SOC stacks because they can only achieve discrete charge transfer, but not constant current transfer. Figure 2 Taking the controlled resistance balancing topology shown in (a) as an example, when a switch is turned on or off, the current in the corresponding branch will suddenly change, which will cause the current through the corresponding battery to suddenly change. Figure 2 This problem also occurs in the other circuits shown. The fundamental reason is that the switch is directly connected in series to the branch connecting the main circuit and the balancing circuit. Therefore, when the switch state changes, the current in the main circuit will also change suddenly, making it impossible to achieve constant current transfer. This problem is common in the current common lithium battery series balancing circuit. This fluctuating current will cause the electrochemical reaction rate on the SOC electrode interface to fluctuate, resulting in an unstable redox environment on the interface, which may endanger the life.

[0009] Therefore, the existing active balancing circuits for lithium batteries are difficult to be directly applied to the balancing of SOC towers, and a new balancing circuit topology needs to be designed. Summary of the invention

[0010] According to one aspect of the present disclosure, an active balancing circuit for realizing a constant transfer current of an electric energy module is provided, wherein the electric energy module comprises n electric energy components electrically connected in series, the circuit comprises: n+1 inductors, n switch units, capacitors, a measuring unit and a signal generating unit, the switch unit comprises a transistor and a diode, the first end of the transistor is connected to the cathode of the diode as the first end of the switch unit, the second end of the transistor is connected to the anode of the diode as the second end of the switch unit, wherein:

[0011] The positive electrode and negative electrode of the electric energy module are connected to the power supply, wherein the positive electrode of the first electric energy component among the n electric energy components serves as the positive electrode of the electric energy module, and the negative electrode of the last electric energy component serves as the negative electrode of the electric energy module.

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

[0013] The second end of the i-th switch unit is connected to the first end of the i+1-th switch unit. The switch units correspond to the electric energy components one by one. 1≤i≤n-1 and i and n are both integers.

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

[0015] The measuring unit is connected to the first end of each inductor and is used to measure the electrical parameters of each electrical energy component;

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

[0017] A switch control signal and a target current are generated according to the electrical parameters of each electrical energy component and the preset electrical parameters. 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 a possible implementation, the switch control signal includes a transistor control signal of a transistor in each switch unit, and the off duty cycle of the transistor control signal is positively correlated with the current magnitude of the corresponding electric energy component.

[0019] In a possible implementation manner, the electrical parameter includes current, and the signal generating unit includes:

[0020] A duty cycle generating unit, used to determine a corresponding duty cycle according to the current of each electric energy component and a preset current;

[0021] A switch signal generating unit, used for generating the switch control signal according to each duty cycle and a preset sawtooth wave signal;

[0022] The current generating unit is used to determine the target current according to the current of each electric energy component and the preset current of each electric energy component.

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

[0024] A first subtractor, used for determining a first current difference between the current of the corresponding electric energy component and a preset current;

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

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

[0027] A first accumulator, used to determine a first current sum corresponding to the current of each electric energy component;

[0028] A second accumulator, used to determine a second current sum of the preset currents corresponding to the respective electrical energy components;

[0029] a second subtractor, configured to determine a second current difference between the first current and the second current;

[0030] A second integrator, used for integrating the second current difference to obtain an integrated value;

[0031] a multiplier, configured to implement a multiplication operation of the second current sum and a target coefficient to obtain an intermediate value;

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

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

[0034] In a possible implementation, the power module is a solid oxide battery SOC, the power assembly is a SOC stack, the SOC stack includes a plurality of stacked cells, and the cells are made of ceramic material, wherein the power module further includes:

[0035] A hot box body, in which each SOC stack is arranged;

[0036] A steam intake manifold and a plurality of steam intake manifolds, wherein the steam enters the hot box body through the steam intake manifold and is distributed to the corresponding SOC stack through each steam intake manifold;

[0037] An air intake main pipe and a plurality of air intake manifolds, wherein air enters the heat box body through the air intake main pipe and is distributed to corresponding SOC stacks through each air intake manifold;

[0038] A hydrogen outlet main pipe and a plurality of hydrogen outlet manifolds, wherein the hydrogen discharged from each SOC stack is collected into the hydrogen outlet main pipe through each hydrogen outlet manifold and then discharged from the hot box body;

[0039] An air outlet main pipe and multiple air outlet manifolds, wherein the air exhausted from each SOC stack is collected by each air outlet manifold to the air outlet main pipe and then discharged from the hot box body.

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

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

[0042] According to one aspect of the present disclosure, a power supply system is provided, the system comprising the active balancing circuit for realizing a constant transfer current of an electric energy module.

[0043] The active balancing circuit of the disclosed embodiment measures the electrical parameters of each electric energy component through a measuring unit, generates a switch control signal and a target current according to the electrical parameters of each electric energy component and preset electrical parameters by a signal generating unit, controls the conduction state of each switch unit by using the switch control signal, and configures the power supply current of the power supply by using the target current. It can achieve current balancing of each electric energy component in the electric energy module, constant current transfer of the electric energy module, and independent decoupling control of each electric energy component. It has a high current balancing capability and a high control efficiency, and can effectively improve the uniformity of the electric energy module.

[0044] It should be understood that the above general description and the following detailed description are exemplary and explanatory only and do not limit the present disclosure. Other features and aspects of the present disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The drawings herein are incorporated into the specification and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and are used to illustrate the technical solutions of the present disclosure together with the specification.

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

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

[0048] Figure 3 A schematic diagram of an active balancing circuit for realizing a constant transfer current of an electric energy 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 generating unit according to an embodiment of the present disclosure is shown.

[0051] Figure 6a A schematic diagram of a duty cycle generating component in a 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 shows a schematic diagram of a switch signal generating unit when the number of electric energy components is 3, Figure 6d A schematic diagram of a switch control signal generated by a switch signal generating unit when the number of electric energy components is 3 is shown.

[0054] Figure 7 A circuit analysis schematic diagram of an electric energy module and an active balancing circuit is shown.

[0055] Figure 8 The schematic diagram of the simulation model structure of the power module and the active balancing circuit when the power component is 3 is shown.

[0056] Figure 9a The schematic diagram shows the control effect of the stack current when the stacks of the power module are consistent in the electrolysis mode.

[0057] Figure 9b The schematic diagram shows the control effect of the inductor current when the battery stacks of the power module are consistent in the electrolysis mode.

[0058] Fig.9c The schematic diagram shows the control effect of the duty cycle of the switch shutdown when the battery stacks of the power module are consistent in the electrolysis mode.

[0059] Figure 9d The schematic diagram shows the control effect of the stack current when the stacks of the power module are consistent in the power generation mode.

[0060] Fig.10a The schematic diagram shows the control effect of the stack current when the internal resistance of the series branches of the power module is inconsistent in the electrolysis mode.

[0061] Fig.10b The schematic diagram shows the control effect of the duty cycle of the switch when the internal resistance of the series branches of the power module is inconsistent in the electrolysis mode.

[0062] Fig.10c The schematic diagram shows the control effect of the stack current when the voltage sources of the series branches of the power module are inconsistent in the electrolysis mode.

[0063] Fig.10d The schematic diagram shows the control effect of the duty cycle of the switch shutdown when the voltage sources of the series branches of the power module are inconsistent in the power generation mode.

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

[0065] Fig.12a Shows Fig.11 The model shown is a schematic diagram of the change in normalized steam flow rate of each fuel cell stack after the uneven air flow distribution occurs.

[0066] Figure 12b Shows Fig.11 The model shown is a schematic diagram of the voltage changes of each battery stack after the uneven air flow distribution occurs.

[0067] Fig.12c Shows Fig.11 The model shown is a schematic diagram of the maximum temperature change of each fuel cell stack after the uneven air flow distribution occurs.

[0068] Fig.12d Shows Fig.11 The model shown is a schematic diagram of the minimum temperature change of each fuel cell stack after the uneven air flow distribution occurs.

[0069] Fig.13a Shows Fig.11 The model shown is a schematic diagram of the current changes of each battery stack after the active balancing circuit is introduced.

[0070] Fig.13b Shows Fig.11 The model shown is a schematic diagram of the voltage changes of each battery stack after the active balancing circuit is introduced.

[0071] Fig.13c Shows Fig.11 The model shown is a schematic diagram of the maximum temperature change of each battery stack after the active balancing circuit is introduced.

[0072] Fig.13d Shows Fig.11 The model shown is a schematic diagram of the minimum temperature change of each battery stack after the active balancing circuit is introduced. DETAILED DESCRIPTION

[0073] Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0074] In the description of the present disclosure, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present disclosure.

[0075] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0076] In the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0077] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0078] In the embodiments of the present disclosure, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent the following three situations: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the embodiments of the present disclosure, the term "at least one" represents any combination of at least two of any one or more of a plurality of. For example, including at least one of A, B, and C can represent including any one or more elements selected from the set consisting of A, B, and C.

[0079] In addition, in order to better illustrate the present disclosure, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present disclosure can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present disclosure.

[0080] See also Figure 3 , Figure 3 A schematic diagram of an active balancing circuit for realizing a constant transfer current of an electric energy 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 (L 1 ~L n+1), n switch units 20, a capacitor C, a measuring unit 30 and a signal generating unit 40, wherein the switch unit 20 includes a transistor (S i , that is, S 1 ~S n ) and diode (D i , that is, D 1 ~D n ), the first end of the transistor is connected to the cathode of the diode as the first end of the switch unit 20, and the second end of the transistor is connected to the anode of the diode as the second end of the switch unit 20, wherein,

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

[0083] The positive electrode of the i-th power component 1210 is connected to the first end of the i-th inductor, the negative electrode of the i-th power component 1210 is connected to the first end of the i+1-th inductor and the positive electrode of the i+1-th power component 1210, the second end of the i-th inductor is connected to the first end of the transistor in the i-th switch unit 20 and the cathode of the diode, the second end of the i-th switch unit 20 is connected to the first end of the i+1-th switch unit 20, the switch units 20 correspond to the power components 1210 one by one, 1≤i≤n-1 and i and n are both integers,

[0084] The first end of the capacitor C is connected to the first end of the first switch unit 20 and the second end of the first inductor, and the second end of the capacitor C is connected to the second end of the last switch unit 20 and the second end 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 electrical energy component 1210;

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

[0087] A switch control signal and a target current are generated according to the electrical parameters of each electrical energy component 1210 and the preset electrical parameters. 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 the disclosed embodiment measures the electrical parameters of each electric energy component 1210 through the measuring unit 30, generates a switch control signal and a target current according to the electrical parameters of each electric energy component 1210 and preset electrical parameters by using the signal generating unit 40, controls the conduction state of each switch unit 20 by using the switch control signal, and configures the power supply current of the power supply 110 by using the target current, thereby achieving current balancing of each electric energy component 1210 in the electric energy module 120, achieving constant current transfer of the electric energy module 120, and achieving independent decoupling control of each electric energy component 1210, having high current balancing capability and high control efficiency, and effectively improving the uniformity of the electric energy module 120.

[0089] The embodiments of the present disclosure do not limit the specific type of the power module 120, and do not limit the specific implementation method and number of the power components 1210. Those skilled in the art can set them 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, a fuel cell, etc. Of course, the active balancing circuit of the embodiments of the present disclosure can also be applied to lithium battery systems or other types of battery systems to achieve active current balancing.

[0090] The embodiment of the present disclosure is exemplified by taking the power module 120 as a solid oxide battery SOC.

[0091] See also 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 a possible implementation, Figure 4a , Figure 4b The electric energy component 1210 is a SOC stack, which includes a plurality of stacked single cells (each of which is connected in series). The present disclosure does not limit the material of the single cell. For example, the single cell is made of a ceramic material. The electric energy module 120 may also include:

[0093] A hot box body, in which each SOC stack is arranged;

[0094] A steam intake manifold and a plurality of steam intake manifolds, wherein the steam enters the hot box body through the steam intake manifold and is distributed to the corresponding SOC stack through each steam intake manifold;

[0095] An air intake main pipe and a plurality of air intake manifolds, wherein air enters the heat box body through the air intake main pipe and is distributed to corresponding SOC stacks through each air intake manifold;

[0096] A hydrogen outlet main pipe and a plurality of hydrogen outlet manifolds, wherein the hydrogen discharged from each SOC stack is collected into the hydrogen outlet main pipe through each hydrogen outlet manifold and then discharged from the hot box body;

[0097] An air outlet main pipe and multiple air outlet manifolds, wherein the air exhausted from each SOC stack is collected by each air outlet manifold to the air outlet main pipe and then discharged from the hot box body.

[0098] For example, Figure 4a As shown, the main current I tot Provided by a power supply 110; on this basis, the active balancing circuit connects the positive and negative leads of all series-connected battery stacks (power components 1210) in the stack tower out of the hot box and connects them to the active balancing circuit. Through the bypass current, the active balancing circuit will control the size of the bypass current, thereby realizing independent control of the current of each battery stack. Since the bypass current is relative to the main current I tot The value is small, so the newly added bypass lead can use a wire with a smaller cross-sectional area, which is lower in cost, and the active balancing circuit will not generate too much heat loss.

[0099] For example, for a stack tower containing n series-connected SOC stacks, the active balancing circuit of the embodiment of the present disclosure includes n+1 inductors L i , n transistors S i , n diodes D connected in anti-parallel with the transistor i , and 1 capacitor C.

[0100] Among them, the embodiments of the present disclosure do not limit the types of transistors. The required type of transistor should be selected according to the specific switching frequency, current / voltage and other parameters. After selecting the corresponding transistor type, the first end, the second end and the control end of the transistor can be determined according to the specific situation, such as a bipolar junction transistor (BJT), a field effect transistor (Metal-Oxide Semiconductor Field Effect Transistor), an insulated gate bipolar transistor (IGBT), etc. The embodiments of the present disclosure are demonstrated by taking IGBT as an example. Exemplarily, if the transistor selects MOSFET, the first end of the transistor is the drain D, the second end of the transistor is the source S, and the control end of the transistor is the gate G; if the transistor selects IGBT, the first end of the transistor is the collector C, the second end of the transistor is the emitter E, and the control end of the transistor is the gate G.

[0101] For example, each inductor can be connected in series to the leads connecting the stack tower. It can be seen from the component characteristics of the inductor that the current passing through the inductor will not change suddenly. Therefore, this structural design ensures that the current on the leads connecting the stack tower will not change suddenly, and further ensures that the current passing through the stack tower will not change suddenly, thereby achieving constant current transfer. By controlling the size of the transferred current, independent decoupling control of the current of each battery stack in the stack tower can be achieved.

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

[0103] The embodiments of the present disclosure do not limit the specific implementation of the signal generating unit 40 and the measuring unit 30. Those skilled in the art can set them according to actual conditions and needs, as long as the corresponding functions can be realized. For example, the signal generating unit 40 may include a processing component. In one example, the processing component includes but is not limited to a separate processor, or a discrete component, or a combination of a processor and a discrete component. The processor may include a controller having an execution instruction function in an electronic device, and the processor may be implemented in any appropriate 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. Inside the processor, the executable instructions may be executed by hardware circuits such as logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers.

[0104] Of course, the signal generating unit 40 may be a discrete device, which is exemplarily described below.

[0105] See also Figure 5 , Figure 5 FIG. 4 is a schematic diagram of a signal generating unit 40 according to an embodiment of the present disclosure.

[0106] In a possible implementation, the electrical parameter may include current, voltage, etc. The embodiment of the present disclosure is introduced by taking current as an example.

[0107] In a possible implementation, Figure 5 As shown, the signal generating unit 40 may include:

[0108] The duty cycle generating unit 410 is used to determine the corresponding duty cycle according to the current of each power component 1210 and the preset current;

[0109] A switch signal generating unit 420, configured 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 tot ).

[0111] There is no limitation on the method for obtaining the preset current of each electric energy component 1210 in the embodiment of the present disclosure. By way of example, the preset current can be directly given from the outside, or generated by a dedicated control circuit, or stored in a memory in advance and directly called from the memory when needed. Those skilled in the art can select an appropriate processing method according to actual conditions and needs.

[0112] In one example, the memory may include a computer-readable storage medium, which may be a tangible device that can hold and store instructions used by an instruction execution device. The computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a programmable read-only memory (PROM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the above. The computer-readable storage medium used herein is not to be interpreted as a transient signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

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

[0114] In a 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 a first current difference;

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

[0117] For example, Figure 6a As shown, for any one of the stacks i (i = 2, 3, ..., n), the measured current Ii and current reference value I i，ref The difference passes through an integral link and is output as the duty cycle d i The existence of the integral link can ensure that the error between the measured value and the reference value of the branch current is 0 after the circuit reaches a steady state, that is, the error-free control of the current is achieved.

[0118] See also Figure 6b , Figure 6b FIG. 4 is a schematic diagram of a current generating unit 430 according to an embodiment of the present disclosure.

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

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

[0121] The second accumulator 4320 is used to determine a second current sum of the preset currents corresponding to each of the electrical energy components 1210;

[0122] A second subtractor 4330, configured to determine a second current difference between the first current and the second current;

[0123] A second integrator 4340 is used to integrate the second current difference to obtain an integral value;

[0124] The multiplier 4350 is used to realize the sum of the second current and the target coefficient (K p ) to obtain the intermediate value;

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

[0126] The disclosed embodiment has a target coefficient (K p ) is not limited in specific size, and technicians in this field can set it according to actual conditions and needs.

[0127] Since the duty cycle d of each transistor 1 d 2 ,…,d n The sum of the currents of the n stacks is 1, and there are only n-1 degrees of freedom. Therefore, it is impossible to achieve zero-difference control of the currents of the n stacks simultaneously by controlling the duty cycle alone. Therefore, it is necessary to find additional degrees of freedom to achieve zero-difference control of the current of stack 1 (the first stack). Figure 6b The PI controller shown in the figure adjusts the total current I tot To realize the stack 1 current I 1 No-difference control.

[0128] For example, in specific implementation, Figure 6b The current generating unit 430 shown in FIG. 1 uses the average value of the reference values ​​of all the stack currents as I tot The difference between the sum of all the stack current reference values ​​and the sum of the measured current values ​​is used to calculate the I tot The existence of the integral link can make the sum of all stack current measurement values ​​follow the sum of the reference values ​​after the circuit stabilizes.

[0129] Since the stack current I 2 ,I 3 ,…,I n Already passed Figure 6b The controller shown achieves zero-error control, so Figure 6b The current generating unit 430 shown in FIG. 1 It can also achieve error-free control.

[0130] Of course, the above introduction to the duty cycle generating unit 410 and the current generating unit 430 is exemplary and should not be regarded as limiting the present disclosure. In other embodiments, those skilled in the art may also introduce the duty cycle generating unit 410 and the current generating unit 430 based on the principle of the PI controller. Figure 6a , Figure 6b The implementation shown is modified.

[0131] In a possible implementation manner, the switch signal generating unit 420 is a PWM (Pulse Width Modulation, PWM) signal generator.

[0132] The PWM signal generator may be implemented in a manner known in the related art, and the embodiments of the present disclosure do not limit this.

[0133] See also Figure 6c , Figure 6d , Figure 6c 1 is a schematic diagram showing the switch signal generating unit 420 when the number of the power components 1210 is 3. Figure 6d FIG. 4 is a schematic diagram showing a switch control signal generated by the switch signal generating unit 420 when the number of the power components 1210 is 3. FIG.

[0134] For example, Figure 6c As shown, the PWM signal generator receives the duty cycle d i and a preset sawtooth wave signal. 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 a trigger turn-on signal for each switch. The corresponding trigger rules are shown in Table 1.

[0135] Table 1 Trigger rules

[0136]

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

[0138] For example, as shown in Table 1, Figure 6d As shown, if d is satisfied 2 <s(t)≤d 2 +d 3 , then transistor S 3 is turned off and the rest of the transistors are turned on.

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

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

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

[0142] It is worth mentioning that Figure 3 The active balancing circuit shown has n switch units 20, so there are 2 n In order to simplify the analysis, the present disclosure simplifies the SOC stack into a voltage source U i With resistor R i The series connection, such as Figure 7 shown.

[0143] On this basis, the present disclosure embodiment only considers these two n There are n switch combinations in which only one switch is disconnected. i For example, if the Figure 7 It can be seen that since the transistors in the other switch 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 Under reverse pressure, it is also in the disconnected state. In this state, the transistor S i 、Diode D iThe transistors and diodes in the remaining switch units 20 are directly removed and replaced by wires, and only the inductor and capacitor C exist in the circuit, becoming a linear circuit.

[0144] refer to Figure 7 , according to Kirchhoff's law, the sum of the currents flowing into the balanced circuit is 0, so:

[0145]

[0146] Among them, i L,n+1 represents the current flowing through the n+1th inductor, i L,i 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 represents the current of the i-th electric energy component 1210 (electrical stack), I tot represents the total current flowing into the power module 120 .

[0150] A theoretical analysis of the circuit shows that under n switch combinations where only one switch is disconnected, the equations satisfied by the circuit are shown in Table 2.

[0151] Table 2 Circuit equations under different switching states

[0152]

[0153] Wherein, L represents the size of each inductor, Ui represents the voltage size of the voltage source corresponding to the i-th power component 1210 (fuel stack), R i represents the resistance corresponding to the i-th electrical energy component 1210, u C Indicates the voltage across capacitor C.

[0154] The inductor current and the capacitor C voltage are taken 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=[U 1 ,U 2 ,...,U n ,I tot ] T .

[0155] Table 2 can be summarized in the general form as shown below: Where 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 of each matrix are as follows:

[0158]

[0159] In the above expression, I n is the identity matrix of dimension n*n, 1 n×n is a matrix with dimension n*n and all elements are 1, e j is a unit column vector of length n, with the jth element being 1 and the rest being 0.

[0160] Assume that the duty cycle of transistor Si being off in one cycle is d i , since the embodiment of the present disclosure only considers n switch combinations in which only one switch is disconnected, 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 the transistor Si is turned off in a switching cycle is Δx i Since the switching period is very short, the derivative can be replaced by the rate of change, that is, Δx = x′Δt. Therefore, combined with equation 1.3, the following equation holds, where T s 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 a steady state, the net change of the state quantity in one cycle should be 0, that is, Therefore, the following equation holds, where Represents the average value of the state variable after the circuit reaches steady state.

[0165]

[0166] By solving this linear equation system, we can get

[0167]

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

[0169]

[0170] By using formula 1.11, the circuit parameters can be optimized, including the optimal selection of inductance, capacitance C and switching cycle parameters.

[0171] In order to guide the design of the controller, it is necessary to know the relationship between the duty cycle and the transfer current (i.e., the inductor current). Equation 1.10 is relatively complex and difficult to derive an analytical expression. Therefore, the present disclosure considers the simplest case, that is, the voltage source and internal resistance of the series branch are equal, that is, U 1 =U 2 =...=U n =U 0 , R 1 =R 2 =... =R n =R 0 , where U 0 Represents the voltage of each voltage source, R 0 Represents the size of each resistor. Under this assumption, by solving equation 1.10, the relationship between the average value of the inductor current and the duty cycle can be derived as follows:

[0172]

[0173] From the above formula, we can see that for inductor i, as the duty cycle d of switch i is turned off, i The current I through the inductor i increases L,i The current drawn from the main circuit by the inductor i decreases, and the current of the corresponding i-th series branch increases accordingly. The present disclosure utilizes this feature to design the signal generating unit 40 to implement current tracking control, thereby achieving current balancing of each power component 1210.

[0174] The active balancing circuit is simulated below by taking the number of the power components 1210 as 3 as an example to verify the effectiveness of the active balancing circuit.

[0175] See also 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 the power components 1210 is 3.

[0176] like Figure 8As shown, the disclosed embodiment takes a stack tower containing three series-connected stacks as an example, and verifies the effect of the designed active balancing circuit through simulation. The disclosed embodiment uses an equivalent circuit model of a voltage source and a resistor in series to simulate the electrical characteristics of the SOC stack, where the voltage source corresponds to the Nernst voltage of the stack, and the resistor corresponds to the equivalent resistance corresponding to the ohmic loss and activation loss of the electrochemical reaction in the stack. The inductor size is selected as 30μH, the capacitor C size is selected as 10μF, and the switching frequency is selected as 1MHz.

[0177] See also Figure 9a , Figure 9a The schematic diagram shows the control effect of the stack current when the power module 120 is in the electrolysis mode and the stacks are consistent.

[0178] See also Figure 9b , Figure 9b The schematic diagram shows the control effect of the inductor current when the power module 120 is in electrolysis mode and the battery stacks are consistent.

[0179] See also Fig.9c , Fig.9c The schematic diagram shows the control effect of the duty cycle of the switch shutdown when the power module 120 and the battery stacks are consistent in the electrolysis mode.

[0180] See also Figure 9d , Figure 9d The schematic diagram shows the control effect of the stack current when the stacks of the power module 120 are consistent in the power generation mode.

[0181] Assume that all series stacks are exactly the same, that is, U 1 =U 2 =U 3 =30V, R 1 =R 2 =R 3 =0.1Ω.

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

[0183] Figure 9a The dotted line in the figure is the reference current value, while the solid line of the corresponding color represents the actual current value of the three series stacks, and the black line represents the external DC power supply input current I tot size.

[0184] from Figure 9a It can be found that after the current reference value changes, the current of the corresponding battery stack can track the reference value within 1s, with good dynamic performance. The circuit can arbitrarily adjust the relative size of the current of the three battery stacks, and can realize the decoupling control of the current of the series battery stacks.

[0185] Figure 9a It shows that the current in the initial stage has certain oscillations, which is mainly caused by improper selection of the initial value of the capacitor C voltage during simulation. The simulation can be optimized by selecting an appropriate initial capacitor C voltage.

[0186] from Figure 9b It can be found that compared with the main current passing through the battery stack, the bypass current passing through the inductor is one order of magnitude smaller, which makes the additional switching loss generated by the bypass current passing through the active balancing circuit smaller, and also reduces the cost of the bypass lead and the selection requirements of the switch tube, making the proposed circuit easier to implement in engineering.

[0187] from Fig.9c By comparing the stack current and the inductor current, it can be found that the duty cycle is negatively correlated with the inductor current and positively correlated with the stack current, which proves the correctness of the theoretical deduction in the previous article and also proves the effectiveness of the signal generating unit 40.

[0188] Figure 9a to Figure 9c It shows that the stack works in electrolysis mode, converting electrical energy into hydrogen energy. The characteristic of SOC technology is that it can work in both electrolysis mode and power generation mode. When the stack current direction is reversed, the stack converts hydrogen energy into electrical energy. At this time, the proposed active balancing circuit can still realize the function of controlling current bypass, such as Figure 9d shown.

[0189] from Figure 9d It can be found that under this working condition, the proposed active balancing circuit can still achieve independent control of the current size of each series stack. It should be noted that the signal generating unit 40 proposed in the embodiment of the present disclosure is based on Figure 7 The positive direction is designed as specified in the specification, and all the voltage and current measurement values ​​and reference values ​​are numbers with positive and negative signs. For the opposite direction, those skilled in the art can change it according to actual conditions and needs.

[0190] In the above introduction, in order to obtain an analytical expression for the relationship between the duty cycle and the transfer current, it is assumed that the voltage sources and resistances of the three series branches are exactly the same. When the resistances or voltage sources of the three series branches are inconsistent, the derived expression 1.12 will no longer be accurate. However, the purpose of formula 1.12 is to guide the design of the signal generating unit 40, and the effectiveness of the designed signal generating unit 40 depends only on the conclusion that "the switch off duty cycle is positively correlated with the corresponding battery stack current". When the three series branches are inconsistent, there is reason to believe that the above conclusion will not change directionally.

[0191] To verify this, the embodiment of the present disclosure tests the performance of the signal generating unit 40 under the condition of inconsistent resistance. Figure 8The simulation model shown in the figure assumes that U 1 =U 2 =U 3 =30V, R 1 =0.08Ω, R 2 =0.1Ω, R 3 =0.12Ω.

[0192] See also Fig.10a , Fig.10a The schematic diagram shows the control effect of the stack current when the internal resistance of the series branches of the power module 120 is inconsistent in the electrolysis mode.

[0193] See also Fig.10b , Fig.10b The schematic diagram shows 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 the electrolysis mode.

[0194] See also Fig.10c , Fig.10c The schematic diagram shows the control effect of the stack current when the voltage sources of the series branches of the power module 120 are inconsistent in the electrolysis mode.

[0195] See also Fig.10d , Fig.10d The schematic diagram shows 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] Attached Fig.10a In the figure, the dotted line is the reference current of each battery stack, the solid line of the corresponding color is the actual current of the battery stack, and the black solid line is the total current I tot size.

[0197] from Fig.10a It can be found that except for the current oscillation in the initial stage, the current tracking effect of the signal generating unit 40 does not change significantly in other cases, which means that the designed signal generating unit 40 can still effectively control the equalization circuit to realize the current tracking function.

[0198] like Fig.10b As shown, it can be found that in the initial 0 to 1 second, although the currents of each series stack are equal, the duty cycles after stabilization are not equal. The larger the internal resistance of the stack, the higher the duty cycle of the corresponding switch off. The simulation sets the initial state of the controller output duty cycle to 33%, which is different 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 has not changed. The larger the duty cycle, the larger the corresponding stack current, and the two still show a positive correlation.

[0199] Fig.10cThis is the simulation result when the voltage sources of different series branches are different in size. Figure 7 The simulation model shown in the figure assumes that U 1 =29V, U 2 =30V, U 3 =31V, R 1 =R 2 =R 3 =0.1Ω. Fig.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 balancing circuit to realize the current tracking function.

[0200] Further draw the change curve of different switch off duty cycle during the simulation process, such as Fig.10d As shown. It can be found that in the initial 0 to 1 second, although the currents of each series stack are equal, the duty cycles after stabilization are not equal. The larger the voltage source of the stack, the higher the duty cycle of the corresponding switch off. The simulation sets the initial state of the controller output duty cycle to 33%, which is different 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 has not changed. The larger the duty cycle, the larger the corresponding stack current, and the two still show a positive correlation.

[0201] See also Fig.11 , Fig.11 A schematic diagram of a stack tower finite element model used to verify the current balancing effect is shown.

[0202] In the previous article, the equivalent circuit model of the battery stack was used to verify the ability of the designed active balancing circuit of the stack tower to achieve current transfer. The following will further verify the ability of current transfer to improve the unevenness of the stack tower based on the finite source model that can more accurately simulate the working characteristics of the stack tower. The finite element model of the stack tower used is as follows: Fig.11 As shown, it includes 4 stacks (Stack 1 to 4) connected in series electrically, and the stack tower is placed in a hot box. The model can simulate the spatial distribution of temperature, current, voltage, and material concentration when the stack tower is working.

[0203] See also Fig.12a , Fig.12a Shows Fig.11 The model shown is a schematic diagram of the change in normalized steam flow rate of each fuel cell stack after the uneven air flow distribution occurs.

[0204] See also Figure 12b , Figure 12b Shows Fig.11 The model shown is a schematic diagram of the voltage changes of each battery stack after the uneven air flow distribution occurs.

[0205] See also Fig.12c , Fig.12c Shows Fig.11 The model shown is a schematic diagram of the maximum temperature change of each fuel cell stack after the uneven air flow distribution occurs.

[0206] See also Fig.12d , Fig.12d Shows Fig.11 The model shown is a schematic diagram of the minimum temperature change of each fuel cell stack after the uneven air flow distribution occurs.

[0207] Assume that at the initial moment, the current of the four stacks is 100A, working in the electrolysis mode, and the stacks are completely consistent at the initial moment, and the steam flow rate allocated to them is also completely equal. The stack tower reaches a stable operating state under this condition. First, the model is used to simulate the changes in the working characteristics of the stack after the uneven airflow distribution occurs, such as Figure 12a to Figure 12d As shown. Fig.12a As shown in Figure 2, the simulation assumes that the normalized steam flow of each stack is inconsistent, with stack 4 receiving the most steam and stack 1 receiving the least. Figure 12b It can be found that with the occurrence of uneven steam distribution, the voltage of the stack also immediately becomes inconsistent. The voltage of stack 1 with insufficient steam is the highest, which is more than 1V higher than that of stack 4. The main reason is the increase in overvoltage caused by insufficient steam distribution. Fig.12c and Fig.12d It can be seen that the unevenness of steam distribution also causes the inconsistency of the temperature of different stacks in the stack tower. The hot spot temperature of stack 1 with insufficient steam can be 15°C higher than the hot spot temperature of stack 4 with sufficient steam. This unevenness will lead to inconsistent degradation rates of different stacks in the stack tower, further exacerbating the inconsistency and endangering the life. In addition, due to Figure 12b It can also be found that after the airflow distribution is uneven, the average voltage of the four battery stacks also increases slightly, indicating that the energy consumption of the stack tower has increased and the operating efficiency has decreased.

[0208] Figure 12a to Figure 12d The case where the active balancing circuit of the embodiment of the present disclosure is not used to actively balance the current of each battery stack is shown. The following describes the case where the active balancing circuit of the embodiment of the present disclosure is used to actively balance the current of each battery stack.

[0209] The disclosed embodiment can effectively improve the current of each series stack by investing in an active balancing circuit to independently control the current of each series stack. Figure 12a to Figure 12d The inconsistency in the case shown is shown in the simulation results. Figure 13a to Figure 13d shown.

[0210] See also Fig.13a , Fig.13a Shows Fig.11 The model shown is a schematic diagram of the current changes of each battery stack after the active balancing circuit is introduced.

[0211] See also Fig.13b , Fig.13b Shows Fig.11 The model shown is a schematic diagram of the voltage changes of each battery stack after the active balancing circuit is introduced.

[0212] See also Fig.13c , Fig.13c Shows Fig.11 The model shown is a schematic diagram of the maximum temperature change of each battery stack after the active balancing circuit is introduced.

[0213] See also Fig.13d , Fig.13d Shows Fig.11 The model shown is a schematic diagram of the minimum temperature change of each battery stack after the active balancing circuit is introduced.

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

[0215] Depend on Fig.13a It is known that the active balancing circuit starts to work at the initial moment to adjust the current of each stack. The active balancing circuit quickly reduces the current of stack 1 with insufficient steam and increases the current of stack 4 with sufficient steam, thereby reducing the voltage difference between each stack. At the same time, the current values ​​of each stack are still around 100A, with a deviation of less than 10A, indicating that the bypass current value through the balancing circuit is very small.

[0216] Depend on Fig.13b It can be seen that after the balancing circuit works, the voltage difference of the four stacks is reduced to about 0.1 V. As the voltage difference is reduced, the heat release power of each stack gradually becomes consistent.

[0217] Depend on Fig.13c , Fig.13d It can be seen that the temperature of each battery stack gradually tends to be balanced. This result proves the effectiveness of the proposed active balancing circuit.

[0218] In order to solve the problem of worsening inconsistency and reduced reliability of SOC after the battery stack is amplified into a stack tower, the disclosed embodiment proposes a new idea of ​​using a balancing control circuit to independently adjust the current of each series battery stack, thereby improving the consistency of the stack tower. Based on this idea, the disclosed embodiment designs a new active balancing circuit topology that can achieve constant current transfer, in order to solve the problem that the existing lithium battery series balancing circuit topology cannot achieve constant current transfer and is not suitable for SOC. For this circuit topology, the disclosed embodiment designs a switch modulation mode, and derives the relationship between the switch duty cycle and the transfer current through theoretical analysis. Based on this, a controller for the active balancing circuit is constructed to enable the current of each series battery stack in the stack tower to independently track its own reference value.

[0219] The disclosed embodiment simulates and verifies the designed active balancing circuit and controller. It has been verified that the circuit can effectively realize constant current transfer, and can still realize the function of transferring current when the series stack has inconsistency. At the same time, the designed controller is not only applicable to the electrolysis mode of SOC, but also in the power generation mode. Through the simulation of the three-dimensional finite element model of the stack tower, the disclosed embodiment verifies that the proposed circuit and controller can effectively improve the uniformity of temperature distribution inside the stack tower when the steam distribution is inconsistent, and reduce the voltage deviation of different series stacks, which is beneficial to improve the life and reliability of large-capacity stack towers, thereby supporting the engineering scale-up of SOC technology.

[0220] According to the above introduction, the embodiment of the present disclosure proposes a new active balancing circuit topology capable of achieving constant transfer current, which can be applied to the current balancing of SOC stack towers and other power modules 120. In view of this topology, the present invention designs a modulation strategy for the circuit switch state, derives a formula describing the relationship between the transfer current and the switch duty cycle based on the average value circuit model, and designs a duty cycle controller based on the relationship between the transfer current and the duty cycle shown by this formula, so as to realize independent decoupling control of different stack currents in the stack tower.

[0221] The disclosed embodiment uses an equivalent circuit model to verify the function of the balancing circuit, and also verifies through a three-dimensional model simulation of the tower stack that the transfer current can effectively improve the consistency of the tower stack.

[0222] The contributions of the embodiments of the present disclosure include but are not limited to:

[0223] (1) A new idea of ​​improving the uniformity of SOC series stacks by controlling bypass current was proposed, and an active balancing circuit topology that can achieve constant current transfer was designed. This circuit is suitable for electrochemical energy conversion devices such as electrolyzers and fuel cells that require constant current transfer, and it also has the potential to be applied to lithium battery systems;

[0224] (2) For the designed active balancing circuit, the embodiment of the present disclosure proposes a corresponding modulation method and builds a control system, and tests the function of the proposed circuit through simulation, verifying that the active balancing circuit can effectively improve the uniformity of the stack by changing the current size of different series-connected battery stacks in the stack.

[0225] According to one aspect of the present disclosure, a power supply system is provided, the system comprising the active balancing circuit for achieving a constant transfer current of the power module 120 .

[0226] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used in the embodiments of the present disclosure is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed in the embodiments of the present disclosure.

Claims

1. An active balancing circuit for realizing a constant transfer current of an electric energy module, characterized in that: The electric energy module includes n electric energy components electrically connected in series, the circuit includes: n+1 inductors, n switch units, capacitors, a measuring unit and a signal generating unit, the switch unit includes a transistor and a diode, the first end of the transistor is connected to the cathode of the diode as the first end of the switch unit, the second end of the transistor is connected to the anode of the diode as the second end of the switch unit, wherein, The positive electrode and negative electrode of the electric energy module are connected to the power supply, wherein the positive electrode of the first electric energy component among the n electric energy components serves as the positive electrode of the electric energy module, and the negative electrode of the last electric energy component serves as the negative electrode of the electric energy module. The positive electrode of the i-th power component is connected to the first end of the i-th inductor, the negative electrode of the i-th power component is connected to the first end of the i+1-th inductor and the positive electrode of the i+1-th power component, and the second end of the i-th inductor is connected to the first end of the transistor in the i-th switch unit and the cathode of the diode. The second end of the i-th switch unit is connected to the first end of the i+1-th switch unit. The switch units correspond to the electric energy components one by one. 1≤i≤n-1 and i and n are both integers. The first end of the capacitor is connected to the first end of the first switch unit and the second end of the first inductor, and the second end of the capacitor is connected to the second end of the last switch unit and the second end of the last inductor. The measuring unit is connected to the first end of each inductor and is used to measure the electrical parameters of each electrical energy component; The signal generating unit is connected to the measuring unit, the control terminals of each transistor and the power supply, and is used for: A switch control signal and a target current are generated according to the electrical parameters of each electrical energy component and the preset electrical parameters. 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 switch control signal includes a transistor control signal of a transistor in each switch unit, and the off duty cycle of the transistor control signal is positively correlated with the current magnitude of the corresponding electric energy component.

3. The circuit according to claim 1, characterized in that The electrical parameter includes current, and the signal generating unit includes: A duty cycle generating unit, used to determine a corresponding duty cycle according to the current of each electric energy component and a preset current; A switch signal generating unit, used for generating the switch control signal according to each duty cycle and a preset sawtooth wave signal; The current generating unit is used to determine the target current according to the current of each electric energy component and the preset current of each electric energy component.

4. The circuit according to claim 3, characterized in that The duty cycle generating unit includes a plurality of duty cycle generating components, and the duty cycle generating components include: A first subtractor, used for determining a first current difference between the current of the corresponding electric energy component and a preset current; The first integrator is used to integrate the first current difference to obtain a corresponding duty cycle.

5. The circuit according to claim 3, characterized in that The current generating unit comprises: A first accumulator, used to determine a first current sum corresponding to the current of each electric energy component; A second accumulator, used to determine a second current sum of the preset currents corresponding to the respective electrical energy components; a second subtractor, configured to determine a second current difference between the first current and the second current; A second integrator, used for integrating the second current difference to obtain an integrated value; a multiplier, configured to implement a multiplication operation of the second current sum and a target coefficient to obtain an intermediate value; The adder is used to implement the addition operation of 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 switch signal generating unit is a PWM signal generator.

7. The circuit according to claim 1, characterized in that The electric energy module is a solid oxide battery (SOC) stack tower, the electric energy component is a SOC stack, the SOC stack includes a plurality of stacked single cells, and the single cells are made of ceramic material, wherein the electric energy module further includes: A hot box body, in which each SOC stack is arranged; A steam intake manifold and a plurality of steam intake manifolds, wherein the steam enters the hot box body through the steam intake manifold and is distributed to the corresponding SOC stack through each steam intake manifold; An air intake main pipe and a plurality of air intake manifolds, wherein air enters the heat box body through the air intake main pipe and is distributed to corresponding SOC stacks through each air intake manifold; A hydrogen outlet main pipe and a plurality of hydrogen outlet manifolds, wherein the hydrogen discharged from each SOC stack is collected into the hydrogen outlet main pipe through each hydrogen outlet manifold and then discharged from the hot box body; An air outlet main pipe and multiple air outlet manifolds, wherein the air exhausted from each SOC stack is collected by each air outlet manifold to the air outlet main pipe and then discharged from the hot box body.

8. The circuit according to claim 1, characterized in that The electric energy component includes any one or a combination of a SOC stack, an electrolyzer, a fuel cell, and a lithium battery.

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

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

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