An electrical energy conversion circuit and method

Abstract

This application discloses a power conversion circuit and method. The circuit includes at least one power conversion branch, each power conversion branch being connected to a power conversion module via an input switch circuit. The power conversion module includes an N-phase interleaved parallel power boost circuit. The positive output terminals are connected together and connected to the positive terminal of a power battery via an output switch circuit. The negative output terminals are connected together and connected to the negative terminal of the power battery. A control unit controls whether to input voltage to the power conversion module by controlling the input switch circuit in the at least one power conversion branch, and controls whether to output voltage to the power battery by controlling the output switch circuit. This circuit solves the problems of high cost and large current ripple in current DC / DC converters, and the high cost of using high-current relays when using high current applications.

Description

Technical Field

[0001] This invention relates to the field of vehicle power supply technology, specifically to an energy conversion circuit and method. Background Technology

[0002] In fuel cell vehicle systems, DC / DC converters are essential power conversion devices responsible for boosting the fuel cell's capacity and storing it in the battery. High power and high current are emerging trends in commercial vehicles. For high power applications, two low-power fuel cells can be connected in parallel. This requires two DC / DC converters, which are currently costly and generate significant current ripple, potentially reducing the lifespan of both the fuel cell and the battery. Conversely, using high-current relays for high-current applications also increases costs. Summary of the Invention

[0003] This invention provides an energy conversion circuit and method to solve the problems that current DC / DC converters are not only expensive, but also generate large current ripples, and the cost of using high-current relays is also high when using high current.

[0004] In a first aspect, this application provides an electrical energy conversion circuit, the circuit comprising:

[0005] At least one power conversion branch, the positive input terminal of each power conversion branch is connected to the fuel cell and the negative input terminal is connected to the fuel cell. The positive input terminal is connected to the positive input terminal of the power conversion module via an input switch circuit. The negative input terminal of the power conversion module is connected to the negative electrode of the fuel cell. The power conversion module includes an N-phase power boost circuit with interleaved parallel connection, where N is an integer not less than 1.

[0006] The positive output terminals of the at least one power conversion branch are connected together, and the negative output terminals of the at least one power conversion branch are connected together. The positive output terminal is connected to the positive terminal of the power battery via an output switch circuit, and the negative output terminal is connected to the negative terminal of the power battery.

[0007] The control unit controls whether to input voltage to the power conversion module by controlling the input switch circuit in at least one power conversion branch, and controls whether to output voltage to the power battery by controlling the output switch circuit.

[0008] In one possible implementation, the N-phase interleaved parallel Boost circuit includes:

[0009] N Boost circuits, each Boost circuit includes an inductor, a field-effect transistor and a diode. One end of the inductor is connected to the output of the switching circuit, and the other end is connected to the anode of the diode and the drain of the field-effect transistor. The sources of the field-effect transistors of the N Boost circuits are connected together to the cathode of the fuel cell, and the cathodes of the diodes are connected together.

[0010] The control unit is also used to control the turn-off and turn-on of each field-effect transistor by generating a pulse width modulation (PWM) wave.

[0011] In one possible implementation, the input switch circuit includes:

[0012] The first main charging branch and the first pre-charging branch are connected in parallel;

[0013] The first main charging branch includes a first main relay, and the first pre-charging branch includes a first pre-charging relay and a first pre-charging resistor connected in series. One end of the first pre-charging relay is connected to the positive electrode of the fuel cell, and the other end of the first pre-charging relay is connected to the first pre-charging resistor.

[0014] In one possible implementation, the output switching circuit includes:

[0015] The second main charging branch and the second pre-charging branch are connected in parallel;

[0016] The second main charging branch includes a second main relay, and the second pre-charging branch includes a second pre-charging relay and a second pre-charging resistor connected in series. One end of the second pre-charging relay is connected to the positive electrode of the fuel cell, and the other end of the second pre-charging relay is connected to the second pre-charging resistor.

[0017] In one possible implementation, the circuit includes:

[0018] A first voltage sampler is connected between the positive and negative terminals of the fuel cell.

[0019] The second voltage sampler is used to connect between the positive input terminal of the power conversion module and the negative electrode of the fuel cell;

[0020] The control unit is used to connect the first pre-charge relay of each input switch circuit. Based on the difference between the voltage collected by the first voltage sampler and the voltage collected by the second voltage sampler, it determines that when the difference is less than a first preset voltage, it disconnects the first pre-charge relay and connects the first main relay.

[0021] In one possible implementation, the circuit includes:

[0022] The third voltage sampler is connected between the positive and negative terminals of the power battery;

[0023] The fourth voltage sampler is connected between the positive and negative output terminals of the power conversion module;

[0024] The control unit is used to connect the second pre-charge relay of the output switch circuit. Based on the difference between the voltage collected by the third voltage sampler and the voltage collected by the fourth voltage sampler, when the difference is less than the second preset voltage, the second pre-charge relay is disconnected and the second main relay is connected.

[0025] Secondly, this application provides an energy conversion system, the system comprising:

[0026] A fuel cell is used to provide electrical energy to a power battery. The positive terminal of the fuel cell is connected to the positive input terminal of the corresponding power conversion branch, and the negative terminal is connected to the negative input terminal of the corresponding power conversion branch.

[0027] An energy conversion circuit is used to boost the electrical energy of a fuel cell and store it in a power battery. The structure of the energy conversion circuit includes the circuit described in the first aspect.

[0028] A power battery is used to provide power to a vehicle. The positive terminal of the power battery is connected to the positive output terminal of each power conversion branch, and the negative terminal is connected to the negative output terminal of each power conversion branch.

[0029] Thirdly, this application provides an energy conversion method, the method comprising:

[0030] Upon receiving the command to start the power conversion circuit, the corresponding power conversion module is connected to the power battery by controlling the output switch circuit to connect.

[0031] The target power conversion branch connecting the fuel cells is determined based on the number of fuel cells connected to the power conversion circuit.

[0032] By controlling the connection of the input switch circuit in the target power conversion branch, the corresponding fuel cell can input voltage to the corresponding power conversion module.

[0033] In one possible implementation, controlling the output switch circuit to connect includes:

[0034] The second pre-charge relay, which is connected to the output switch circuit, determines that the difference between the voltage collected by the third voltage sampler and the voltage collected by the fourth voltage sampler is less than the second preset voltage. When this difference is less than the second preset voltage, the second pre-charge relay is disconnected and the second main relay is connected.

[0035] In one possible implementation, controlling the connection of the input switch circuit in the target power conversion branch includes:

[0036] The first pre-charge relay, which connects all input switch circuits, disconnects and connects the first main relay when the difference between the voltage collected by the first voltage sampler and the voltage collected by the second voltage sampler is less than a first preset voltage.

[0037] In one possible implementation, when the input switch circuit in the target power conversion branch is connected, it further includes:

[0038] The generated PWM wave controls the turn-off and turn-on of each field-effect transistor in the corresponding power conversion module.

[0039] This application provides an energy conversion circuit and method that utilizes a DC / DC conversion circuit obtained by interleaving and paralleling multiple N-phase Boost circuits. This achieves high power for the entire vehicle system while avoiding the generation of current ripple and reducing costs by eliminating the use of high-current relays. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of an energy conversion circuit according to an exemplary embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of an N-box interleaved parallel Boost circuit according to an exemplary embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of an energy conversion system according to an exemplary embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram illustrating a power conversion method according to an exemplary embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram illustrating a specific process of an energy conversion method according to an exemplary embodiment of the present invention. Detailed Implementation

[0045] The technical solutions in the embodiments of this application will now be described clearly and in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] First, the technical terms used in the embodiments of this invention will be introduced.

[0047] DC-DC converters: DC / DC converters are voltage converters that transform input voltage and effectively output a fixed voltage. DC / DC converters are divided into three categories: boost DC / DC converters, buck DC / DC converters, and buck-boost DC / DC converters. Depending on the requirements, three types of control can be used. Among them, PWM control type has high efficiency and good output voltage ripple and noise.

[0048] In view of the current ripple and high cost issues in the application of DC-DC / DC converters in fuel cell vehicle systems where high power and high current are required, this application provides an energy conversion circuit for use in DC-DC converters. The circuit includes:

[0049] At least one power conversion branch, the positive input terminal of each power conversion branch is connected to the fuel cell and the negative input terminal is connected to the fuel cell. The positive input terminal is connected to the positive input terminal of the power conversion module via an input switch circuit. The negative input terminal of the power conversion module is connected to the negative electrode of the fuel cell. The power conversion module includes an N-phase power boost circuit with interleaved parallel connection, where N is an integer not less than 1.

[0050] The positive output terminals of the at least one power conversion branch are connected together, and the negative output terminals of the at least one power conversion branch are connected together. The positive output terminal is connected to the positive terminal of the power battery via an output switch circuit, and the negative output terminal is connected to the negative terminal of the power battery.

[0051] The control unit controls whether to input voltage to the power conversion module by controlling the input switch circuit in at least one power conversion branch, and controls whether to output voltage to the power battery by controlling the output switch circuit.

[0052] like Figure 1 As shown, the input method used in this application is multi-channel isolated input. Taking two fuel cells as an example, the fuel cells are connected to their corresponding power conversion modules respectively. Multiple power conversion modules are controlled by a control unit, and each power conversion module includes an N-phase interleaved parallel Boost circuit.

[0053] In one possible implementation, the N-phase interleaved parallel Boost circuit is as follows: Figure 2 As shown, it includes:

[0054] There are N Boost circuits, each consisting of an inductor, a field-effect transistor (FET), and a diode. One end of the inductor is connected to the output of the switching circuit, and the other end is connected to the anode of the diode and the drain of the FET. The sources of the FETs in all N Boost circuits are connected together to the cathode of the fuel cell, and the cathodes of the diodes are connected together. Here, N is an integer not less than 1, and its specific value can be determined based on the vehicle's current requirements and the rated current of the FETs and diodes.

[0055] The control unit is also connected to the gate of the field-effect transistors (FETs) and is used to control the turn-off and turn-on of each FET through the generated pulse width modulation (PWM) wave. When the PWM wave is high, the FET is turned on, and when it is low, the FET is turned off. The PWM wave can be generated by, but is not limited to, a microcontroller.

[0056] Capacitors are connected between the positive and negative input terminals of each power conversion module and between the positive and negative terminals of the power battery. This connection constitutes a fixed circuit structure. Figure 1 In order to prevent the capacitors C1, C2 and C3 from being damaged by the large current generated by the instantaneous power-on, a switching circuit needs to be connected between the power supply and the capacitors. The input switching circuit connected before C1 and C2 is used to suppress the current generated by the fuel cell when it is turned on, and the output switching circuit connected after C3 is used to suppress the current generated by the power battery when it is turned on.

[0057] In one possible implementation, the input switch circuit includes:

[0058] The first main charging branch and the first pre-charging branch are connected in parallel;

[0059] The first main charging branch includes a first main relay, and the first pre-charging branch includes a first pre-charging relay and a first pre-charging resistor connected in series. One end of the first pre-charging relay is connected to the positive electrode of the fuel cell, and the other end of the first pre-charging relay is connected to the first pre-charging resistor.

[0060] The output switching circuit includes:

[0061] The second main charging branch and the second pre-charging branch are connected in parallel;

[0062] The second main charging branch includes a second main relay, and the second pre-charging branch includes a second pre-charging relay and a second pre-charging resistor connected in series. One end of the second pre-charging relay is connected to the positive electrode of the fuel cell, and the other end of the second pre-charging relay is connected to the second pre-charging resistor.

[0063] It should be noted that, Figure 1The resistance values ​​of the first pre-charge resistors R1 and R2 in the first pre-charge branch of the input switch circuit and the resistance value of the second pre-charge resistor R3 in the second pre-charge branch of the output switch circuit can be the same or different. The specific values ​​can be selected according to the size of capacitors C1, C2, and C3.

[0064] In one possible implementation, the following can also be connected before the positive and negative input terminals of each power conversion module:

[0065] A first voltage sampler is connected between the positive and negative terminals of the fuel cell.

[0066] The second voltage sampler is used to connect between the positive input terminal of the power conversion module and the negative electrode of the fuel cell;

[0067] The control unit can determine the connection and disconnection of the first main relay and the first pre-charge relay based on the voltage values ​​collected by the first voltage sampler and the second voltage sampler. Specifically, the following implementation method can be adopted:

[0068] Taking one of the power conversion branches as an example, the first pre-charge relay K2, which connects to each input switch circuit, is disconnected and connected to the first main relay K1 when the difference between the voltage collected by the first voltage sampler V1 and the voltage collected by the second voltage sampler V2 is less than the first preset voltage.

[0069] The structure and control of the output switching circuit are similar to those of the input switching circuit, specifically:

[0070] In one possible implementation, the following can also be connected before the positive and negative input terminals of each power conversion module:

[0071] The third voltage sampler is connected between the positive and negative terminals of the power battery;

[0072] The fourth voltage sampler is connected between the positive and negative output terminals of the power conversion module;

[0073] The second pre-charge relay K6 is connected to the output switch circuit via the control unit. Based on the difference between the voltage collected by the third voltage sampler V6 and the voltage collected by the fourth voltage sampler V5, if the difference is less than the second preset voltage, the second pre-charge relay K6 is disconnected and the second main relay K5 is connected.

[0074] The power conversion circuit provided in this application uses an N-phase interleaved parallel Boost circuit as a single power conversion module, reducing current ripple and thus extending the lifespan of the fuel cell. Multiple fuel cells are each connected to a separate power conversion module, ensuring isolated inputs and allowing a single DC / DC converter to connect to two fuel cells simultaneously.

[0075] Based on the same inventive concept, embodiments of this application also provide an energy conversion system, such as... Figure 3 As shown, the system includes:

[0076] A fuel cell is used to provide electrical energy to a power battery. The positive terminal of the fuel cell is connected to the positive input terminal of the corresponding power conversion branch, and the negative terminal is connected to the negative input terminal of the corresponding power conversion branch.

[0077] An energy conversion circuit is used to boost the electrical energy of a fuel cell and store it in a power battery. The structure of the energy conversion circuit includes any of the above-mentioned energy conversion circuit structures.

[0078] A power battery is used to provide power to a vehicle. The positive terminal of the power battery is connected to the positive output terminal of each power conversion branch, and the negative terminal is connected to the negative output terminal of each power conversion branch.

[0079] Based on the same inventive concept, embodiments of this application also provide an electrical energy conversion method, such as... Figure 4 As shown, the method includes:

[0080] S401: Receives the command to start the power conversion circuit, and connects the corresponding power conversion module and the power battery by controlling the output switch circuit to connect.

[0081] The command to start the power conversion circuit is issued by the control unit. After receiving the command, the power conversion circuit first needs to connect the output switch circuit.

[0082] In one possible implementation, controlling the output switch circuit to connect includes:

[0083] The second pre-charge relay, which is connected to the output switch circuit, determines that the difference between the voltage collected by the third voltage sampler and the voltage collected by the fourth voltage sampler is less than the second preset voltage. When this difference is less than the second preset voltage, the second pre-charge relay is disconnected and the second main relay is connected.

[0084] S402: Determine the target power conversion branch connecting the fuel cells based on the number of fuel cells connected to the power conversion circuit.

[0085] The number of fuel cells varies depending on the vehicle's needs; it can include one fuel cell or multiple fuel cells. Generally, two fuel cells are sufficient to meet the vehicle's power requirements. If the vehicle has only one fuel cell, then a power conversion branch corresponding to that fuel cell can be identified; the same applies to two fuel cells.

[0086] S403: By controlling the connection of the input switch circuit in the target power conversion branch, the corresponding fuel cell inputs voltage to the corresponding power conversion module.

[0087] After determining the number of fuel cells and their corresponding power conversion branches, the input switch circuit needs to be connected first.

[0088] In one possible implementation, controlling the connection of the input switch circuit in the target power conversion branch includes:

[0089] The first pre-charge relay, which connects all input switch circuits, disconnects and connects the first main relay when the difference between the voltage collected by the first voltage sampler and the voltage collected by the second voltage sampler is less than a first preset voltage.

[0090] The field-effect transistor in the connected power module can be implemented in the following way:

[0091] The generated PWM wave controls the on / off state of each field-effect transistor (FET) in the corresponding power conversion module. When the PWM wave is high, the FET is on; when the PWM wave is low, the FET is off. During this process, based on the preset maximum current carrying capacity of each module and the number of fuel cells, the number of FETs in the corresponding power conversion module can be controlled to control the output current of each fuel cell. Figure 2 As shown, the control unit can determine whether the current of the power conversion module has reached the preset maximum carrying current by collecting the current value of the current sensor.

[0092] In one possible implementation, the specific process of the power conversion method is as follows: Figure 5 As shown, taking two fuel cells as an example:

[0093] S1: Receives the command to start the power conversion circuit and starts the power conversion circuit;

[0094] S2: Connect the output switch circuit, and the specific connection method is as described above;

[0095] S3: Determine the number of fuel cells and whether the single-input switch circuit is connected;

[0096] S4: If it is determined that the single-input switch circuit is connected, connect the single-input circuit corresponding to the fuel cell;

[0097] S5: Activate the power conversion module corresponding to the fuel cell;

[0098] S6: If it is determined that the dual-input switch circuit is connected, connect the dual-input circuit corresponding to the fuel cell.

[0099] S7: Activate the dual energy conversion module corresponding to the fuel cell;

[0100] S8: The circuit is operating normally and charging the power battery.

[0101] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. An electrical energy conversion circuit, characterized in that, include: At least one power conversion branch is provided. The positive input terminal of each power conversion branch is connected to the fuel cell, and the negative input terminal is connected to the fuel cell. The positive input terminal is connected to the positive input terminal of the power conversion module via an input switch circuit. The negative input terminal of the power conversion module is connected to the negative electrode of the fuel cell. The power conversion module is used to boost the power of the fuel cell and store it in the power battery. The power conversion module includes N-phase interleaved parallel power boost circuits. The N-phase interleaved parallel boost circuits include N boost circuits. Each boost circuit includes a current sensor, an inductor, a field-effect transistor, and a diode. One end of the inductor is connected to the output terminal of the switch circuit, and the other end is connected to the positive electrode of the diode and the drain of the field-effect transistor. The sources of the field-effect transistors of the N boost circuits are connected together to the negative electrode of the fuel cell, and the negative electrodes of the diodes are connected together. N is an integer not less than 1. The positive output terminals of the at least one power conversion branch are connected together, and the negative output terminals of the at least one power conversion branch are connected together. The positive output terminal is connected to the positive terminal of the power battery via an output switch circuit, and the negative output terminal is connected to the negative terminal of the power battery. The control unit controls whether to input voltage to the power conversion module by controlling the input switch circuit in at least one power conversion branch, controls whether to output voltage to the power battery by controlling the output switch circuit, determines the number of field-effect transistors in the power conversion module to be turned on by the preset maximum carrying current of the power conversion module and the number of fuel cells, and determines whether the current of the power conversion module has reached the preset maximum carrying current by collecting the current value of the current sensor.

2. The circuit according to claim 1, characterized in that, The control unit is also used to control the turn-off and turn-on of each field-effect transistor by generating a pulse width modulation (PWM) wave.

3. The circuit according to claim 1, characterized in that, The input switch circuit includes: The first main charging branch and the first pre-charging branch are connected in parallel; The first main charging branch includes a first main relay, and the first pre-charging branch includes a first pre-charging relay and a first pre-charging resistor connected in series. One end of the first pre-charging relay is connected to the positive electrode of the fuel cell, and the other end of the first pre-charging relay is connected to the first pre-charging resistor.

4. The circuit according to any one of claims 1 to 3, characterized in that, The output switching circuit includes: The second main charging branch and the second pre-charging branch are connected in parallel; The second main charging branch includes a second main relay, and the second pre-charging branch includes a second pre-charging relay and a second pre-charging resistor connected in series. One end of the second pre-charging relay is connected to the positive electrode of the fuel cell, and the other end of the second pre-charging relay is connected to the second pre-charging resistor.

5. The circuit according to claim 3, characterized in that, The circuit includes: A first voltage sampler is connected between the positive and negative terminals of the fuel cell. The second voltage sampler is used to connect between the positive input terminal of the power conversion module and the negative electrode of the fuel cell; The control unit is used to connect the first pre-charge relay of each input switch circuit. Based on the difference between the voltage collected by the first voltage sampler and the voltage collected by the second voltage sampler, it determines that when the difference is less than a first preset voltage, it disconnects the first pre-charge relay and connects the first main relay.

6. The circuit according to claim 4, characterized in that, The circuit includes: The third voltage sampler is connected between the positive and negative terminals of the power battery; The fourth voltage sampler is connected between the positive and negative output terminals of the power conversion module; The control unit is used to connect the second pre-charge relay of the output switch circuit. Based on the difference between the voltage collected by the third voltage sampler and the voltage collected by the fourth voltage sampler, when the difference is less than the second preset voltage, the second pre-charge relay is disconnected and the second main relay is connected.

7. An electrical energy conversion system, characterized in that, The system includes: A fuel cell is used to provide electrical energy to a power battery. The positive terminal of the fuel cell is connected to the positive input terminal of the corresponding power conversion branch, and the negative terminal is connected to the negative input terminal of the corresponding power conversion branch. An energy conversion circuit is used to boost the electrical energy of a fuel cell and store it in a power battery. The structure of the energy conversion circuit includes the circuit described in any one of claims 1 to 6. A power battery is used to provide power to a vehicle. The positive terminal of the power battery is connected to the positive output terminal of each power conversion branch, and the negative terminal is connected to the negative output terminal of each power conversion branch.

8. A method for electrical energy conversion, characterized in that, The method includes: Upon receiving the command to start the power conversion circuit, the corresponding power conversion module is connected to the power battery by controlling the output switch circuit. The target power conversion branch connecting the fuel cells is determined based on the number of fuel cells connected to the power conversion circuit. By controlling the connection of the input switch circuit in the target power conversion branch, the corresponding fuel cell inputs voltage to the corresponding power conversion module. The number of field effect transistors in the power conversion module is determined by the preset maximum carrying current of the power conversion module and the number of fuel cells. By collecting the current value of the current sensor, it is determined whether the current of the power conversion module has reached the preset maximum carrying current. The power conversion module includes an N-phase interleaved parallel power boost circuit, which is used to boost the power energy of the fuel cell and store it in the power battery. The N-phase interleaved parallel boost circuit includes N boost circuits. Each boost circuit includes a current sensor, an inductor, a field-effect transistor, and a diode. One end of the inductor is connected to the output terminal of the switching circuit, and the other end is connected to the positive terminal of the diode and the drain terminal of the field-effect transistor. The sources of the field-effect transistors of the N boost circuits are connected together to the negative terminal of the fuel cell, and the negative terminals of the diodes are connected together.

9. The method according to claim 8, characterized in that, Controlling the connection of the output switch circuit includes: The second pre-charge relay, which is connected to the output switch circuit, determines that the difference between the voltage collected by the third voltage sampler and the voltage collected by the fourth voltage sampler is less than the second preset voltage. When this difference is less than the second preset voltage, the second pre-charge relay is disconnected and the second main relay is connected.

10. The method according to claim 8, characterized in that, Controlling the connection of the input switch circuit in the target power conversion branch includes: The first pre-charge relay, which connects all input switch circuits, disconnects and connects the first main relay when the difference between the voltage collected by the first voltage sampler and the voltage collected by the second voltage sampler is less than a first preset voltage.

11. The method according to claim 8, characterized in that, When the input switch circuit in the target power conversion branch is connected by controlling the connection, it also includes: The generated PWM wave controls the turn-off and turn-on of each field-effect transistor in the corresponding power conversion module.

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