Control method of power supply circuit, power conversion device and energy storage device

Abstract

This application provides a control method for a power supply circuit, a power conversion device, and an energy storage device. The control method includes acquiring the actual battery temperature and actual battery voltage, as well as the on / off state of a discharge switch. When the actual battery temperature is lower than a preset lower temperature limit and the discharge switch is off, a first DC-DC converter is controlled using a first target voltage as the setpoint for a first output voltage loop, causing the first side of the first DC-DC converter to output a corresponding first target voltage. A second DC-DC converter is controlled using a second target voltage as the setpoint for a second bus voltage loop, causing the second side of the second DC-DC converter to output a corresponding second target voltage to the battery heating circuit. The first target voltage is less than the actual battery voltage. This method enables heating of a low-temperature battery while avoiding charging and discharging, and also has lower hardware costs.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a control method for a power supply circuit, a power conversion device, and an energy storage device. Background Technology

[0002] In related technologies, batteries are often connected to two DC-DC converter circuits. One end of each DC-DC converter circuit is connected in series with the DC bus, and the other end is connected in parallel with the battery. Charging and discharging switches are placed between the battery and the DC-DC converter circuits to control the battery's charging and discharging. This allows for the transfer of electrical energy between the two DC-DC converter circuits and the DC bus. Furthermore, to prevent the battery's lifespan and capacity from decreasing due to low-temperature operation, a heating circuit connected to the DC bus is used to heat the battery at low temperatures. However, this design requires the heating circuit to withstand the high voltage of the DC bus, necessitating the use of higher voltage-rated components, resulting in higher hardware costs. Summary of the Invention

[0003] In view of this, this application provides a control method for a power supply circuit, a power conversion device, and an energy storage device, which can heat a low-temperature battery while avoiding charging and discharging the battery, and the hardware cost is also low.

[0004] The first aspect of this application provides a control method for a power supply circuit. The power supply circuit includes a first DC-DC converter and a second DC-DC converter. The first sides of the first and second DC-DC converters are connected in parallel and then connected to a battery through a discharge switch. A body diode is connected in parallel to the discharge switch. The anode of the body diode is connected to the first terminal of the discharge switch, and the cathode of the body diode is connected to the second terminal of the discharge switch and the battery. The second sides of the first and second DC-DC converters are connected in series through the midpoint of a bus and are respectively connected to each half of the DC bus. A battery heating circuit is connected in parallel to the second side of the second DC-DC converter. The control method includes: acquiring the actual battery temperature and actual battery voltage, as well as the on / off state of the discharge switch; when the actual battery temperature is lower than a preset lower temperature limit and the discharge switch is off, controlling the first DC-DC converter with a first target voltage as the setpoint of the first output voltage loop, so that the first side of the first DC-DC converter outputs the corresponding first target voltage; and controlling the second DC-DC converter with a second target voltage as the setpoint of the second bus voltage loop, so that the second side of the second DC-DC converter outputs the corresponding second target voltage to the battery heating circuit; the first target voltage is less than the actual battery voltage.

[0005] The control method of this application acquires the actual battery temperature and voltage, and the on / off state of the discharge switch to monitor the battery temperature and discharge status. Then, when the battery is at a low temperature and not discharging, that is, when the actual battery temperature is below a preset lower limit and the discharge switch is off, the first DC converter is controlled with a first target voltage less than the actual battery voltage as the given value of the first output voltage loop, so that the first side of the first DC converter outputs the corresponding first target voltage. The second DC converter is controlled with a second target voltage as the given value of the second bus voltage loop, so that the second side of the second DC converter outputs the corresponding second target voltage to the battery heating circuit. The battery heating circuit is thus powered and heats the battery, causing the battery temperature to rise. It is understandable that, since the discharge switch is connected in parallel with a body diode, when the first side of the first DC-DC converter outputs power, even if the discharge switch is off, the power from the first DC-DC converter may still supply power to the low-temperature battery through the body diode of the discharge switch, causing the battery to continue operating at low temperatures, which is detrimental to battery safety and performance. Therefore, in this embodiment, the first target voltage is used as the setpoint for the first output voltage loop to control the first DC-DC converter, so that the voltage output from the first side of the first DC-DC converter is less than the actual battery voltage. That is, the anode voltage of the body diode is less than the cathode voltage, and the body diode is cut off, thereby preventing charging of the battery. In addition, since the voltage on the second side of the second DC-DC converter is easily pulled down when the battery heating circuit is instantaneously switched on, it can cause bias voltage on the two half-buses, forming a circulating current, which is detrimental to circuit safety. Therefore, in this embodiment, the second target voltage is used as the setpoint for the second bus voltage loop to control the second DC-DC converter, which can avoid the voltage on the second side of the second DC-DC converter being pulled down and avoid bias voltage on the two half-buses. Therefore, the method of this application embodiment can heat the low-temperature battery while avoiding charging and discharging the battery, resulting in high safety of the battery and circuit. Moreover, there is no need to set up a charging switch tube, and the battery heating circuit does not need to bear the entire bus voltage, but only half of the bus voltage, thereby reducing the device voltage specifications and hardware costs.

[0006] In one embodiment, controlling the first DC-DC converter using a first target voltage as a setpoint for the first output voltage loop includes: acquiring a first actual output voltage and a first actual output current of the first DC-DC converter; using the first target voltage as a setpoint for the first output voltage loop, inputting the first actual output voltage into the first output voltage loop to obtain a first reference current; obtaining a first target control parameter based on the first reference current and the first actual output current; and outputting a first control signal based on the first target control parameter, wherein the first control signal is used to control the operation of the first DC-DC converter.

[0007] In one embodiment, using a first target voltage as a given value for a first output voltage loop, and inputting a first actual output voltage into the first output voltage loop to obtain a first reference current, the method includes: subtracting the first target voltage from the first actual output voltage to obtain a first voltage difference; performing deviation processing on the first voltage difference to obtain a first initial current; and performing amplitude limiting processing on the first initial current to obtain a first reference current.

[0008] In one embodiment, controlling the second DC-DC converter using a second target voltage as a setpoint for the second bus voltage loop includes: acquiring a second actual bus voltage and a second actual input current of the second DC-DC converter; using the second target voltage as a setpoint for the second bus voltage loop, inputting the second actual bus voltage into the second bus voltage loop to obtain a second reference current; obtaining a second target control parameter based on the second reference current and the second actual input current; and outputting a second control signal based on the second target control parameter, the second control signal being used to control the operation of the second DC-DC converter.

[0009] In one embodiment, the control method further includes: when the actual battery temperature is equal to or higher than a preset lower limit, controlling the first DC-DC converter with a second target voltage as a given value for the first bus voltage loop, such that the second side of the first DC-DC converter receives the corresponding second target voltage. In one embodiment, the control loop of the first DC-DC converter includes a first output voltage loop, a first bus voltage loop, and a selector. The selector is used to select the first output voltage loop to control the first DC-DC converter when the actual battery temperature is lower than the preset lower limit, and to select the first bus voltage loop to control the first DC-DC converter when the actual battery temperature is equal to or higher than the preset lower limit.

[0010] In one embodiment, the selector is a smaller value selector, used to output the smaller value between the output of the first output voltage loop and the output of the first bus voltage loop. When the actual battery temperature is below a preset lower limit, the first output voltage loop is selected to control the first DC-DC converter; and when the actual battery temperature is equal to or higher than the preset lower limit, the first bus voltage loop is selected to control the first DC-DC converter. This includes: when the actual battery temperature is below the preset lower limit, controlling the first DC-DC converter with a first target voltage as the setpoint for the first output voltage loop, so that the output of the first output voltage loop is less than the output of the first bus voltage loop, and selecting the output of the first output voltage loop as the output of the smaller value selector; when the actual battery temperature is equal to or higher than the preset lower limit, controlling the first DC-DC converter with a third target voltage as the setpoint for the first output voltage loop, so that the output of the first output voltage loop is greater than the output of the first bus voltage loop, and selecting the output of the first bus voltage loop as the output of the smaller value selector; the third target voltage is greater than the actual battery voltage.

[0011] In one embodiment, the battery heating circuit includes a heating element and a heating switch connected in series; the control method further includes: when the actual battery temperature is lower than a preset lower limit and the discharge switch is off, controlling the heating switch to turn on so that the heating element can perform heating operation; when the actual battery temperature is equal to or higher than the preset lower limit, controlling the heating switch to turn off so that the heating element stops working.

[0012] A second aspect of this application provides a power conversion device, including a power supply circuit and a controller. The power supply circuit includes a first DC-DC converter and a second DC-DC converter. The first sides of the first and second DC-DC converters are connected in parallel and then connected to a battery through a discharge switch. A body diode is connected in parallel to the discharge switch. The anode of the body diode is connected to the first end of the discharge switch, and the cathode of the body diode is connected to the second end of the discharge switch and the battery. The second sides of the first and second DC-DC converters are connected in series through the midpoint of a bus and are respectively connected to each half of the DC bus. A battery heating circuit is connected in parallel to the second side of the second DC-DC converter. The controller is used to execute the control method described in the first aspect or any embodiment of the first aspect.

[0013] A third aspect of this application provides an energy storage device, comprising: a battery, a discharge switch, a power supply circuit, a battery heating circuit, and a controller. The power supply circuit includes a first DC-DC converter and a second DC-DC converter. The first sides of the first and second DC-DC converters are connected in parallel and then connected to the battery through the discharge switch. A body diode is connected in parallel to the discharge switch. The anode of the body diode is connected to the first end of the discharge switch, and the cathode of the body diode is connected to the second end of the discharge switch and the battery. The second sides of the first and second DC-DC converters are connected in series through the midpoint of a bus and are respectively connected to each half of the DC bus. The battery heating circuit is connected in parallel to the second side of the second DC-DC converter. The controller is used to execute the control method described in the first aspect or any embodiment of the first aspect.

[0014] The fourth aspect of this application provides an electronic device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to perform the control method described in the first aspect or any embodiment of the first aspect.

[0015] A fifth aspect of this application provides a control device, including an acquisition module and a control module. The acquisition module is used to acquire the actual battery temperature and actual battery voltage, as well as the on / off state of a discharge switch. The control module is used to control a first DC-DC converter with a first target voltage as the given value of a first output voltage loop when the actual battery temperature is lower than a preset lower limit and the discharge switch is off, so that the first side of the first DC-DC converter outputs a corresponding first target voltage; and to control a second DC-DC converter with a second target voltage as the given value of a second bus voltage loop, so that the second side of the second DC-DC converter outputs a corresponding second target voltage to the battery heating circuit; the first target voltage is less than the actual battery voltage.

[0016] The sixth aspect of this application provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the method described in the first aspect or any embodiment of the first aspect.

[0017] Furthermore, the technical effects of any of the possible implementations in aspects two through six can be found in the technical effects of different implementations in aspect one, and will not be repeated here. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a heating circuit heating a battery in related technologies.

[0019] Figure 2 This is an application scenario diagram of a power supply circuit control method provided in an embodiment of this application.

[0020] Figure 3 This is a flowchart of a control method for a power supply circuit provided in an embodiment of this application.

[0021] Figure 4 yes Figure 3 A detailed flowchart of step S40.

[0022] Figure 5 yes Figure 4 A detailed flowchart of step S42.

[0023] Figure 6 yes Figure 3 A detailed flowchart of step S50.

[0024] Figure 7 This is a schematic diagram of a control loop provided in an embodiment of this application.

[0025] Figure 8 This is another schematic diagram of the control loop provided in one embodiment of this application.

[0026] Figure 9Is Figure 2 The battery heating circuit is not working. When the battery is discharging normally, the waveform diagram of the first actual bus voltage and the second actual bus voltage is shown.

[0027] Figure 10 Is Figure 2 A waveform diagram of the first and second actual output voltages when the battery heating circuit is turned on.

[0028] Figure 11 Is Figure 2 When the battery heating circuit is turned on, a waveform diagram of the first actual output current and the second actual input current is shown.

[0029] Figure 12 Is Figure 2 A waveform diagram of the first actual bus current and the second actual bus current when the battery heating circuit is turned on.

[0030] Figure 13 This is a schematic diagram of a power conversion device provided in an embodiment of this application.

[0031] Figure 14 This is a schematic diagram of an electronic device provided in an embodiment of this application.

[0032] Figure 15 This is a schematic diagram of a control device provided in an embodiment of this application. Detailed Implementation

[0033] It should be noted that the terms "first," "second," and "third" in the specification, claims, and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0034] It should also be noted that the methods disclosed in the embodiments of this application or the methods shown in the flowcharts include one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged, and some steps can also be deleted.

[0035] Some embodiments will now be described with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] In related technologies, such as Figure 1As shown, the battery is typically connected to two DC-DC converter circuits. One end of each DC-DC converter circuit is connected in series with the DC bus, and the other end is connected in parallel with the battery. Charging and discharging switches are placed between the battery and the DC-DC converter circuits to control the battery's charging and discharging. This allows for the transfer of electrical energy between the two DC-DC converter circuits and the DC bus. Furthermore, to prevent the battery's lifespan and capacity from decreasing due to low-temperature operation, a heating circuit connected to the DC bus is used to heat the battery during low-temperature operation.

[0037] However, such a design requires the heating circuit to withstand the high voltage VBUS of the DC bus, which means that the heating circuit needs to use devices with higher voltage specifications, resulting in higher hardware costs.

[0038] In response, this application provides a power supply circuit control method that can heat a low-temperature battery while preventing the battery from charging and discharging, and the hardware cost is also low.

[0039] The technical solution of this application will be further described in detail below with reference to the accompanying drawings.

[0040] Please see Figure 2 This is an application scenario diagram of a power supply circuit control method provided in an embodiment of this application.

[0041] like Figure 2 As shown, the scenario includes a power supply circuit 100, a battery 200, a DC bus, and a battery heating circuit 300. The power supply circuit 100 includes two DC converters: a first DC converter 10 and a second DC converter 20. The DC bus includes two half-buses: a positive half-bus BUS+ and a negative half-bus BUS-.

[0042] Specifically, the first side of the first DC-DC converter 10 and the first side of the second DC-DC converter 20 are connected in parallel. Therefore, the voltage Vdc1 on the first side of the first DC-DC converter 10 is equal to the voltage Vdc2 on the first side of the second DC-DC converter 20.

[0043] The first side of the first DC-DC converter 10 and the first side of the second DC-DC converter 20, which are connected in parallel, are also connected to the battery 200 through a discharge switch Q1. A reverse-connected body diode D1 is connected in parallel with the discharge switch Q1. The anode of the body diode D1 is connected to the first terminal of the discharge switch Q1, and the cathode of the body diode D1 is connected to the second terminal of the discharge switch Q1 and the battery 200.

[0044] The discharge switch Q1 can be a semiconductor switch, including but not limited to transistors, silicon controlled rectifiers (SCRs), metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), or gallium nitride high-electron-mobility transistors (GaN HEMTs). For example, the discharge switch Q1 can be an N-channel MOSFET, where the gate is the control terminal, the source is the first terminal, and the drain is the second terminal.

[0045] If the discharge switch Q1 is turned on, the battery 200 can discharge to at least one of the first DC-DC converter 10 and the second DC-DC converter 20 through the channel of the discharge switch Q1. If the discharge switch Q1 is turned off, the battery 200 cannot discharge. Therefore, the discharge of the battery 200 can be controlled by controlling the on / off state of the discharge switch Q1.

[0046] When the anode voltage of the body diode D1 is higher than the cathode voltage and the voltage difference exceeds the conduction threshold of the body diode D1 (e.g., 0.6V to 0.7V), the body diode D1 conducts, and at least one of the first DC-DC converter 10 and the second DC-DC converter 20 can charge the battery 200 through the body diode D1. If the anode voltage is lower than the cathode voltage, the body diode D1 is turned off, and the battery 200 cannot be charged. Therefore, by controlling the on / off state of the body diode D1, the charging of the battery 200 can be controlled.

[0047] The second side of the first DC converter 10 and the second side of the second DC converter 20 are connected in series through the midpoint N of the bus, and are respectively connected to each half bus of the DC bus.

[0048] For ease of description, such as Figure 2As shown, this embodiment uses the example of connecting the second side of the first DC-DC converter 10 to the positive half bus BUS+ and the bus midpoint N, and the second side of the second DC-DC converter 20 to the negative half bus BUS- and the bus midpoint N. Therefore, the voltage on the second side of the first DC-DC converter 10 is the first actual bus voltage Vbus1 of the positive half bus BUS+ relative to the bus midpoint N, and the voltage on the second side of the second DC-DC converter 20 is the second actual bus voltage Vbus2 of the bus midpoint N relative to the negative half bus BUS-. The total voltage of the DC bus (or total bus voltage) is denoted as VBUS, and the total current of the DC bus (or total bus current) is denoted as IBUS. The sum of the voltages Vbus1 and Vbus2 is equal to the total DC bus voltage VBUS. Under normal circumstances, Vbus1 and Vbus2 are equal, both being VBUS / 2 (which can be simply referred to as half bus voltage).

[0049] It should be noted that the main bus (i.e., DC bus) can be divided into a half bus (i.e., a single segment) or multiple sub-buses according to actual operating requirements and topology design. For example, each sub-bus can be directly connected in series to the main bus through a sectionalizing switch.

[0050] It should be understood that the first DC-DC converter 10 can be configured with an appropriate topology, such as an LLC resonant converter circuit, a dual active bridge (DAB) converter circuit, a buck-boost circuit, or other DC-DC converter circuits, depending on the actual situation. The second DC-DC converter 20 adopts the same topology as the first DC-DC converter 10.

[0051] In this embodiment, both the first DC-DC converter 10 and the second DC-DC converter 20 are bidirectional converters, meaning they can operate in either forward or reverse direction. Forward operation refers to the direction in which electrical energy flows from the second side of the DC-DC converter to the first side, with the input side being the second side and the output side being the first side. Reverse operation refers to the direction in which electrical energy flows from the first side of the DC-DC converter to the second side, with the input side being the first side and the output side being the second side. It should be understood that in other embodiments, the forward and reverse directions can be reversed.

[0052] The battery heating circuit 300 is connected in parallel to the second side of the second DC-DC converter 20. For example... Figure 2As shown, the battery heating circuit 300 includes a heating element R1 connected in series and a heating switch K1. When the heating switch K1 is closed, the heating element R1 is connected to the bus midpoint N, the negative half bus BUS-, and the second DC-DC converter 20 to form a circuit. The second DC-DC converter 20 can supply power to the heating element R1, and the voltage across the heating element R1 is Vbus2. The heating element R1 generates heat when energized, thereby heating the battery 200. When the heating switch K1 is open, the heating element R1 stops heating the battery 200.

[0053] The heating switch K1 is, for example, any one or a combination of a relay, a knife switch, and a semiconductor switch. The heating element R1 is, for example, a heating film or a heating wire, and its heating power is adjustable. For example, the energizing time of the heating element R1 can be changed by adjusting the high-level duty cycle of the pulse-width modulation (PWM) control signal of the heating switch K1, thereby changing the heating power of the heating element R1.

[0054] Figure 2 The scenario also includes a controller 400. The controller 400 may be, for example, a microcontroller unit (MCU) or other control circuitry.

[0055] The controller 400 is connected to the discharge switch Q1 and the heating switch K1 in the battery heating circuit 300, as well as the first DC converter 10 and the second DC converter 20 in the power supply circuit 100, and is used to control the switching state of the discharge switch Q1 and the heating switch K1, and to control the working state of the first DC converter 10 and the second DC converter 20.

[0056] The controller 400 includes a control loop for the first DC-DC converter 10 and a control loop for the second DC-DC converter 20. The input / output parameters of the first DC-DC converter 10 and the second DC-DC converter 20 can be controlled through the corresponding control loops. The control loops can be implemented in hardware, software, or a combination of both; no special limitation is made here. The input / output parameters include at least one of voltage, current, and power.

[0057] In practice, the power supply circuit 100 can be applied to a variety of working conditions.

[0058] For example, the power supply circuit 100 can be applied to battery charging conditions. In this condition, a power source such as a power conversion system (PCS) is connected between the positive half bus (BUS+) and the negative half bus (BUS-) of the DC bus. The controller 400 can control the first DC converter 10 and the second DC converter 20 in the power supply circuit 100 to operate in the forward direction, and control the discharge switch Q1 to be turned off and the battery heating circuit 300 to be deactivated. Thus, the second sides of the first DC converter 10 and the second DC converter 20 are both input sides, and the first sides of the first DC converter 10 and the second DC converter 20 are both output sides. Power can be supplied to the first DC converter 10 and the second DC converter 20 through the DC bus, and the first DC converter 10 and the second DC converter 20 then charge the battery 200 together through the body diode D1.

[0059] For example, the power supply circuit 100 can be applied to battery discharge mode. In this mode, a load is connected between the positive half bus BUS+ and the negative half bus BUS-. The controller 400 can control the first DC-DC converter 10 and the second DC-DC converter 20 to operate in reverse, and control the discharge switch Q1 to turn on and the battery heating circuit 300 to turn off. Thus, the first side of the first DC-DC converter 10 and the second DC-DC converter 20 are both input sides, and the second side of the first DC-DC converter 10 and the second DC-DC converter 20 are both output sides. The battery 200 can supply power to the first DC-DC converter 10 and the second DC-DC converter 20 through the discharge switch Q1, and the first DC-DC converter 10 and the second DC-DC converter 20 then jointly supply power to the load through the DC bus.

[0060] For example, the power supply circuit 100 can be applied to low-temperature battery operating conditions. In this condition, power is connected between the positive half bus BUS+ and the bus midpoint N. The battery heating circuit 300 acts as a load. The controller 400 can control the first DC-DC converter 10 to operate in the forward direction and the second DC-DC converter 20 to operate in the reverse direction, as well as control the discharge switch Q1 to disconnect and the battery heating circuit 300 to operate. Thus, the first DC-DC converter 10 uses its second side as the input side and its first side as the output side. The second DC-DC converter 20 uses its first side as the input side and its second side as the output side. Figure 2 As shown, the power supply can power the second DC-DC converter 20 through the first DC-DC converter 10, and the second DC-DC converter 20 then powers the battery heating circuit 300, which in turn heats the battery 200. The energy flow can be referenced... Figure 2 The bold black arrow in the middle indicates this.

[0061] For example, the power supply circuit 100 can be applied to the aging test conditions of the DC-DC converter. If the battery heating circuit 300 is used as a load, the circuit operation under this condition can be referred to the low-temperature battery condition, which will not be repeated here. If other loads are connected between the negative half bus BUS- and the bus midpoint N, the controller 400 can control the battery heating circuit 300 to not work, and the second DC-DC converter 20 will supply power to the other loads.

[0062] In this embodiment, for battery low-temperature operating conditions, the controller 400 can execute the control method of the power supply circuit provided in this application embodiment to control the first DC converter 10 and the second DC converter 20, so as to heat the low-temperature battery 200 while preventing the low-temperature battery 200 from charging and discharging.

[0063] Next, the control method for the power supply circuit according to an embodiment of this application will be described. It is understood that in other embodiments, it may also be implemented by a dedicated control device / electronic device / processor, etc.

[0064] like Figure 3 As shown, the control method for the power supply circuit includes:

[0065] Step 10: Obtain the actual battery temperature and voltage, as well as the on / off state of the discharge switch.

[0066] The controller 400 can detect the actual battery temperature using a temperature sensor located on or adjacent to the battery surface. As a further example, the temperature sensor could be a negative temperature coefficient (NTC) thermistor, connected in series between the positive and negative terminals of the battery. The voltage across the NTC thermistor is negatively correlated with temperature. Therefore, the controller 400 can determine the corresponding temperature based on the voltage across the NTC thermistor; this temperature is the actual battery temperature.

[0067] The controller 400 can detect the actual battery voltage by using a voltage sampling circuit connected to the positive and negative terminals of the battery.

[0068] It can be understood that the on / off state of the discharge switch Q1 can be interpreted as whether the discharge switch Q1 meets the conduction condition. Since the conduction condition of the discharge switch Q1 is the magnitude of its voltage or current, in some examples, the controller 400 detects the voltage or current of the discharge switch Q1 through the sampling circuit, which is equivalent to obtaining the on / off state of the discharge switch Q1.

[0069] For example, if the discharge switch Q1 is an N-channel MOSFET, the conduction condition of the discharge switch Q1 is that the gate-source voltage VGS of the discharge switch Q1 is greater than the conduction threshold VGSth. Therefore, the controller 400 obtains the magnitude of the gate-source voltage VGS by detecting the voltage sampling circuit, and thus obtains the on / off state of the discharge switch Q1.

[0070] In other examples, the on / off state of the discharge switch Q1 can also be obtained by controlling the controller of the discharge switch Q1 or by reading specific flag bits in the memory, etc., and this application does not limit this.

[0071] Step 20: Confirm whether the actual battery temperature is lower than the preset lower limit.

[0072] The preset lower temperature limit can be set according to the actual situation, such as -5℃, 0℃, 1℃ or other temperature values, without specific limitations here.

[0073] If the actual battery temperature is higher than or equal to the preset lower limit, the battery temperature is normal. If the actual battery temperature is lower than the preset lower limit, the battery temperature is too low, so proceed to step S30.

[0074] Step 30: Confirm whether the discharge switch is off. If the discharge switch is off, proceed to steps S40 and S50.

[0075] The controller 400 can determine whether the discharge switch Q1 is in a conducting state or a disconnected state by judging whether the detected voltage or current of the discharge switch Q1 meets the conduction conditions.

[0076] For example, if the discharge switch Q1 is an N-channel MOSFET, the controller 400 determines that the discharge switch Q1 is turned on when it determines that the gate-source voltage VGS is greater than the turn-on threshold VGSth. The controller 400 determines that the discharge switch Q1 is turned off when it determines that the gate-source voltage VGS is less than or equal to the turn-on threshold VGSth.

[0077] In other examples, the controller 400 can also determine that the discharge switch Q1 is off when it reads the value of a specific flag bit in the register, and that the discharge switch Q1 is on when the read value is a first value (e.g., 0).

[0078] Step 40: When the actual battery temperature is lower than the preset lower limit and the discharge switch is turned off, the first DC-DC converter is controlled with the first target voltage as the given value of the first output voltage loop, so that the first side of the first DC-DC converter outputs the corresponding first target voltage.

[0079] Among them, the first target voltage is less than the actual battery voltage. That is to say, the first target voltage Vref1 = Vbat - N, where N is a positive value. The magnitude of N can be adjusted accordingly according to actual situations (such as the actual battery voltage Vbat, voltage sampling error, undervoltage point UVP of the battery, etc.), and no specific limitation is made here.

[0080] For example, in an embodiment, the magnitude of N needs to satisfy the conditions: Vbat – N > UVP and Vbat – N < Vbat. That is to say, the magnitude of N should ensure that the first target voltage Vref1 is greater than the battery undervoltage point and at the same time ensure that the first target voltage Vref1 is less than the actual battery voltage Vbat.

[0081] The first output voltage loop is a control loop used to control the output voltage of the first side of the first DC converter. It can adjust the voltage conversion process of the first DC converter according to the given value Vset_out1, so that the output voltage Vdc1 of the first side of the first DC converter is equal to the given value Vset_out1.

[0082] Therefore, in step S40, when the first target voltage Vref1 is input as the given value Vset_out1 to the first output voltage loop, the first output voltage loop can control the voltage Vdc1 output by the first side of the first DC converter to be equal to the first target voltage Vref1, that is, Vdc1 is less than the actual battery voltage Vbat.

[0083] Since the first side of the first DC converter is connected to the anode of the body diode D1 and the cathode of the battery-connected body diode D1, the anode voltage of the body diode D1 is Vdc1, and the cathode voltage of the body diode D1 is Vbat. When Vdc1 is less than Vbat, the body diode D1 is turned off, making the electrical energy output by the first side of the first DC converter unable to be transmitted to the battery.

[0084] Step 50: Control the second DC converter with the second target voltage as the given value of the second bus voltage loop, so that the second side of the second DC converter outputs the corresponding second target voltage to the battery heating circuit.

[0085] Among them, the second target voltage Vref2 can be set accordingly according to the total voltage VBUS of the DC bus. Exemplarily, the second target voltage Vref2 can be set to be equal to half of VBUS, that is, Vref2 = VBUS / 2.

[0086] The second bus voltage loop is a control loop used to control the second actual bus voltage Vbus2 output from the second side of the second DC-DC converter. It can adjust the voltage conversion process of the second DC-DC converter according to a given value Vset_bus2, so that the second actual bus voltage Vbus2 output from the second side of the second DC-DC converter is equal to the given value Vset_bus2. Therefore, the second bus voltage loop is also equivalent to the second output voltage loop of the second DC-DC converter.

[0087] Therefore, in step S50, when the second target voltage Vref2 is used as the given value Vset_bus2 input to the second bus voltage loop, the second bus voltage loop can control the second actual bus voltage Vbus2 output from the second side of the second DC converter to be equal to the second target voltage Vref2, which is equal to VBUS / 2.

[0088] Since the sum of the bus voltages Vbus1 and Vbus2 between the positive half bus BUS- and the bus midpoint N is equal to the total DC bus voltage VBUS, when Vbus2 equals VBUS / 2, Vbus1 also equals VBUS / 2. That is, Vbus2 and Vbus1 are equal, preventing bias voltage. This avoids circulating current between the positive and negative half bus BUS- and suppresses fluctuations in Vbus2 and Vbus1, making them controllable and stable. Consequently, the battery heating circuit, using VBUS / 2 as its operating voltage, can stably perform heating operations.

[0089] In summary, the control method of this application monitors the battery temperature and discharge status by acquiring the actual battery temperature and voltage, and the on / off state of the discharge switch. Then, when the battery is at a low temperature and not discharging (i.e., the actual battery temperature is below a preset lower limit and the discharge switch is off), a first target voltage less than the actual battery voltage is used as the given value for the first output voltage loop to control the first DC-DC converter, causing the first side of the first DC-DC converter to output the corresponding first target voltage. Furthermore, a second target voltage is used as the given value for the second bus voltage loop to control the second DC-DC converter, causing the second side of the second DC-DC converter to output the corresponding second target voltage to the battery heating circuit. The battery heating circuit is thus powered and heats the battery, causing the battery temperature to rise.

[0090] In order to prevent the power of the first DC converter from supplying power to the low-temperature battery through the body diode of the discharge switch when the first side of the first DC converter is outputting, which would be detrimental to battery safety and performance, the embodiments of this application use the first target voltage as the given value of the second bus voltage loop to control the second DC converter, so that the voltage output from the first side of the first DC converter is less than the actual battery voltage. That is, the anode voltage of the body diode is less than the cathode voltage, the body diode is cut off, thereby prohibiting battery charging and protecting battery safety.

[0091] To prevent the voltage on the second side of the second DC-DC converter from dropping when the battery heating circuit is momentarily switched on, which would cause bias voltage on the two half-buses, forming a circulating current, resulting in additional losses, reduced heating efficiency, and compromised circuit safety, this embodiment uses the second target voltage as the given value for the second bus voltage loop to control the second DC-DC converter. This avoids the voltage on the second side of the second DC-DC converter being pulled down, thus preventing bias voltage and voltage fluctuations on the two half-buses.

[0092] Therefore, the method of this application embodiment can achieve heating of low-temperature batteries while avoiding charging and discharging of the batteries, with high heating efficiency, safety and stability.

[0093] Furthermore, the embodiments of this application can omit the charging switch tube, and the battery heating circuit does not need to bear the entire bus voltage, but only half of the bus voltage. This can reduce the device voltage specifications and hardware costs, and also help improve heating safety.

[0094] It's understandable that batteries perform worse at low temperatures. If the discharge switch remains on at low temperatures, allowing the battery to continue discharging, it will easily damage the battery and reduce its performance. Therefore, if... Figure 3 As shown, if step S30 confirms that the discharge switch is turned on, the control method may further include the following steps:

[0095] Step S60: When the actual battery temperature is lower than the preset lower limit and the discharge switch is turned on, control the discharge switch to turn off.

[0096] Therefore, step S60 can prevent the battery from discharging at low temperatures, thus protecting the battery.

[0097] After executing step S60, the controller 400 can return to step S30 to confirm whether the discharge switch Q1 is really off. If the discharge switch Q1 is off, it proceeds to steps S40 and S50.

[0098] Afterwards, when the battery reaches its normal operating temperature, the controller 400 can control the discharge switch Q1 to turn on, allowing the battery to resume its normal discharge function.

[0099] In addition, the control can perform corresponding regulation on the first DC converter to解除电池的充电限制. Therefore, as Figure 3 shown, the control method further includes the following steps:

[0100] Step S70: When the actual battery temperature is equal to or higher than the preset temperature lower limit, control the first DC converter with the second target voltage as the given value of the first bus voltage loop, so that the second side input of the first DC converter corresponds to the second target voltage.

[0101] Among them, the first bus voltage loop is a control loop used to control the first actual bus voltage Vbus1 of the second side input of the first DC converter. It can adjust the voltage conversion process of the first DC converter according to the given value Vset_bus1, so that the first actual bus voltage Vbus1 of the first side input of the first DC converter is equal to the given value Vset_bus1. Therefore, the first bus voltage loop is also equivalent to the first input voltage loop of the first DC converter.

[0102] Therefore, in step S70, when the second target voltage Vref2 = VBUS / 2 is input as the given value Vset_bus1 to the first bus voltage loop, the first bus voltage loop can control the voltage Vbus1 of the second side input of the first DC converter to be equal to the second target voltage VBUS / 2, and the first DC converter then performs voltage conversion on VBUS / 2.

[0103] It can be understood that since the first DC converter is controlled by switching to the first bus voltage loop at this time and not through the first output voltage loop, the restriction that Vdc1 < Vbat causes the body diode D1 to be cut off is lifted, which is beneficial to the battery to resume normal charging function.

[0104] Moreover, the first bus voltage loop limits Vbus1 to be equal to VBUS / 2. When Vbus1 is equal to VBUS / 2, Vbus2 will also be equal to VBUS / 2. That is, Vbus1 and Vbus2 are equal, and there will be no bias voltage situation. Therefore, it is possible to avoid the generation of circulating current between the positive half bus BUS- and the negative half bus BUS-, and suppress the fluctuations of Vbus2 and Vbus1.

[0105] Therefore, through the above step S70, the battery can resume normal operation, and the voltage balance and stability of the two half buses can be maintained, ensuring the availability of the battery and the stable operation of the power supply circuit.

[0106] It should be understood that if the battery is always at normal temperature and does not need to be heated, when the discharge switch tube is turned on, the control method can directly execute step S70.

[0107] It should be noted that the phrase "解除电池的充电限制" in the original text seems to be an incomplete or incorrect expression. It might need to be further clarified or corrected in the original content for a more accurate translation. Here, a literal translation is provided first.In some embodiments, the controller 400 may use a selector to achieve accurate switching between the first output voltage loop and the first bus voltage loop.

[0108] like Figure 7 As shown, the control loop of the first DC-DC converter may include a first output voltage loop 401, a first bus voltage loop 403, and a selector 405. The selector 405 is used to select the first output voltage loop 401 to control the first DC-DC converter when the actual battery temperature is lower than a preset lower limit, and to select the first bus voltage loop 403 to control the first DC-DC converter when the actual battery temperature is equal to or higher than the preset lower limit.

[0109] In one embodiment, the selector 405 may use the relationship between the actual battery temperature and a preset lower temperature limit as the selection condition. When the actual battery temperature is lower than the preset lower temperature limit, the selector 405 directly selects the first output voltage loop 401 and uses the output of the first output voltage loop 401 to control the first DC-DC converter. When the actual battery temperature is equal to or higher than the preset lower temperature limit, the selector 405 directly selects the first bus voltage loop 403 and uses the output of the first bus voltage loop 403 to control the first DC-DC converter.

[0110] In another embodiment, the selector 405 may use the magnitude relationship between the output of the first output voltage loop 401 and the output of the first bus voltage loop 403 as the selection condition.

[0111] Specifically, such as Figure 7 As shown, selector 405 is a smaller value selector, which is used to output the smaller value between the output of the first output voltage loop 401 and the output of the first bus voltage loop 403.

[0112] When the actual battery temperature is lower than the preset lower limit, the first output voltage loop uses the first target voltage Vref1 as the setpoint Vset_out1, and the first bus voltage loop uses the second target voltage Vref2 as the setpoint Vset_bus1. Based on this, the output of the first output voltage loop is less than the output of the first bus voltage loop. Therefore, the selector selects the output of the first output voltage loop as the output of the smaller circuit, and uses the output of the first output voltage loop to control the first DC-DC converter.

[0113] When the actual battery temperature is equal to or higher than the preset lower limit, the first output voltage loop uses the third target voltage Vref3 as the setpoint Vset_out1, and the first bus voltage loop uses the second target voltage Vref2 as the setpoint Vset_bus1. The third target voltage Vref3 is greater than the actual battery voltage Vbat, for example, Vref3 = Vbat + N. Based on this, the output of the first output voltage loop is greater than the output of the first bus voltage loop. Therefore, the selector selects the output of the first bus voltage loop as the output of the smaller loop, and uses the output of the first bus voltage loop to control the first DC-DC converter.

[0114] It should be understood that this application does not limit the selection logic of the selector, as long as the selector can achieve the corresponding function.

[0115] Similarly, in some embodiments, the control loop of the second DC converter may also include a selector and two voltage loops, with the selector choosing one of the voltage loops to control the second DC converter.

[0116] For example, such as Figure 8 As shown, the control loop of the second DC-DC converter may include a second bus voltage loop 402, a second input voltage loop 404, and a selector 406. For ease of distinction, the selector 405 in the control loop of the first DC-DC converter is referred to as the first selector, and the selector 406 in the control loop of the second DC-DC converter is referred to as the second selector.

[0117] When the actual battery temperature is lower than the preset lower limit, the second input voltage loop uses the fourth target voltage Vref4 as the setpoint Vset_in2, and the second bus voltage loop uses the second target voltage Vref2 as the setpoint Vset_bus2. The fourth target voltage Vref4 is greater than the actual battery voltage Vbat, for example, Vref4 = Vbat + M, where M is equal to or greater than N. Based on this, the output of the second input voltage loop is greater than the output of the second bus voltage loop. Therefore, the second selector selects the output of the second bus voltage loop as the output of the smaller circuit, and uses the output of the second bus voltage loop to control the second DC-DC converter.

[0118] When the actual battery temperature is equal to or higher than the preset lower limit, since the first DC converter is controlled by the first bus voltage loop, Vbus1 and Vbus2 can remain stable. Therefore, the second DC converter can be controlled by either the second input voltage loop or the second bus voltage loop.

[0119] In one embodiment, the outputs of both the first output voltage loop and the first bus voltage loop are a reference current; therefore, as Figure 7As shown, in addition to the first output voltage loop 401, the first bus voltage loop 403, and the first selector 405, the control loop of the first DC converter may also include a first current loop 407. The first current loop 407 can control the first DC converter according to the reference current output by the first output voltage loop and the first bus voltage loop.

[0120] Therefore, when the first selector selects the first output voltage loop to control the first DC-DC converter, such as Figure 4 and Figure 7 As shown, the process of controlling the first DC-DC converter in step S40, using the first target voltage as the setpoint for the first output voltage loop, may include:

[0121] Step S41: Obtain the first actual output voltage and the first actual output current of the first DC converter.

[0122] The first actual output voltage Vdc1 of the first DC converter can be obtained by sampling the voltage on the first side of the first DC converter through a voltage sampling circuit.

[0123] The first actual output current Idc1 of the first DC converter can be obtained by sampling the current on the first side of the first DC converter through a current sampling circuit.

[0124] Step S42: Using the first target voltage as the given value of the first output voltage loop, input the first actual output voltage into the first output voltage loop to obtain the first reference current.

[0125] The first output voltage loop can adjust the first reference current Iref1 based on the first target voltage Vref1 and the first actual output voltage Vdc1. The first selector then outputs the first reference current Iref1 to the first current loop.

[0126] Step S43: Obtain the first target control parameter based on the first reference current and the first actual output current.

[0127] The first current loop can adjust the first target control parameter Scr1 based on the first reference current Iref1 and the first actual output current Idc1.

[0128] The first target control parameter Scr1 is, for example, the duty cycle, frequency, or phase of the first DC converter. It can be flexibly selected according to the actual situation and is not specifically limited here.

[0129] Step S44: Output a first control signal according to the first target control parameter. The first control signal is used to control the operation of the first DC converter.

[0130] When the first target control parameter Scr1 is the duty cycle, the first control signal S1 can be, for example, a PWM signal, which controls the voltage conversion process by adjusting the on-time of different switching transistors in the first DC-DC converter. The duty cycle range can be set according to the parameter range and operating conditions of the actual device, for example, 0 to 0.5.

[0131] When the first target control parameter Scr1 is a frequency, the first control signal S1 can be, for example, a PFM (Pulse Frequency Modulation) signal, which controls the voltage conversion process by adjusting the switching frequency of different switching transistors in the first DC-DC converter. The frequency range can be set according to the parameter range and operating conditions of the actual device, for example, 70kHz to 200kHz.

[0132] When the first target control parameter Scr1 is a phase, the first control signal S1 can be, for example, a PSM (Phase Shift Modulation) signal, which controls the voltage conversion process by adjusting the phase difference between different switches in the first DC-DC converter. The phase range can be set according to the parameter range and operating conditions of the actual device, for example, -0.5 to 0.5 (the unit is the DC-DC converter period T).

[0133] Ultimately, the first actual output voltage Vdc1 of the first DC converter can be adjusted to Vref1, and the first actual output current Idc1 of the first DC converter can be adjusted to Iref1.

[0134] Therefore, steps S41 to S44 above combine the first output voltage loop and the first current loop to obtain the first control signal S1. Since the first control signal S1 can be used to adjust the first actual output voltage Vdc1 and the first actual output current Idc1 of the first DC converter, and the first actual output voltage Vdc1 is fed back to the first output voltage loop, and the first actual output current Idc1 is fed back to the first current loop, the above process can form a closed-loop regulation, thereby improving the immediacy and accuracy of adjusting the first actual output voltage Vdc1 and the first actual output current Idc1.

[0135] In one embodiment, the first output voltage loop can perform deviation processing based on the voltage difference between the first target voltage Vref1 and the first actual output voltage Vdc1 to obtain the first reference current Iref1.

[0136] Therefore, as Figure 5 As shown, step S42, which uses the first target voltage as the given value of the first output voltage loop and inputs the first actual output voltage into the first output voltage loop to obtain the first reference current, may include:

[0137] Step S421: Subtract the first target voltage from the first actual output voltage to obtain the first voltage difference.

[0138] For example, a subtractor can be used to subtract the first target voltage Vref1 from the first actual output voltage Vdc1 to obtain the first voltage difference ΔV. That is, ΔV = Vref1 - Vdc1.

[0139] Step S422: Perform deviation processing on the first voltage difference to obtain the first initial current.

[0140] For example, a deviation processor can be used to process the first voltage difference ΔV. In this process, the deviation processor may employ a deviation processing algorithm such as PI (Proportion Integration) regulation, PID (Proportion Integration Differentiation) regulation, or other deviation regulation algorithms.

[0141] Step S423: Limit the first initial current to obtain the first reference current.

[0142] For example, a limiter can be used to limit the first initial current to a suitable current range. For instance, the first initial current can be limited to the range of [-80A, 80A], so that the first initial current within the range of [-80A, 80A] can be used as the first reference current Iref1.

[0143] It should be understood that the current range is set according to the charging and discharging power specifications of the DC-DC converter and battery, as well as the rated current of the battery heating circuit. The current value within this range is greater than the rated current of the battery heating circuit to ensure sufficient power to start the battery heating circuit.

[0144] Therefore, it can be seen that the deviation adjustment algorithm used in the above steps S421 to S423 can help improve control accuracy and control speed, and facilitate the rapid adjustment of the first reference current Iref1 to a suitable value.

[0145] Similarly, in one embodiment, the first current loop can perform deviation processing based on the current difference between the first reference current Iref1 and the second actual output current Idc1 to obtain the first target control parameter Scr1.

[0146] Therefore, as Figure 7 As shown, the process of obtaining the first target control parameter based on the first reference current and the first actual output current in step S43 may include:

[0147] Subtract the first reference current Iref1 from the first actual output current Idc1 to obtain the first current difference ΔI, where ΔI = Iref1 - Idc1;

[0148] Then, the first current difference ΔI is processed to obtain the first initial control parameter;

[0149] Finally, the first initial control parameter is subjected to amplitude limiting to obtain the first target control parameter Scr1. The first target control parameter Scr1 can be modulated by a modulator to generate the first control signal S1.

[0150] It should be understood that the process of step S43 can be referred to the aforementioned steps S421 to S423, and will not be repeated here.

[0151] When the first selector selects the first bus voltage loop to control the first DC converter, such as Figure 7 As shown, the process of controlling the first DC-DC converter in step S70 by using the second target voltage as the given value of the first bus voltage loop may include:

[0152] Obtain the first actual bus voltage Vbus1 and the first actual output current Idc1 of the first DC converter;

[0153] Then, using the second target voltage Vref2 as the given value Vset_bus1 of the first output voltage loop, the first actual bus voltage Vbus1 is input into the first bus voltage loop to obtain the first reference current Iref1;

[0154] Next, based on the first reference current Iref1 and the first actual output current Idc1, the first target control parameter Scr1 is obtained;

[0155] Finally, according to the first target control parameter Scr1, the first control signal S1 is output. The first control signal S1 is used to control the operation of the first DC converter, so that the first actual output voltage Vdc1 of the first DC converter is adjusted to Vref2 and the first actual output current Idc1 of the first DC converter is adjusted to Iref1.

[0156] It should be understood that the process of step S70 is similar to that of step S40. For details, please refer to the aforementioned steps S41 to S44, so they will not be repeated here.

[0157] Since step S70 combines the first bus voltage loop and the first current loop to obtain the first control signal S1, this process can form a closed-loop regulation, thereby improving the immediacy and accuracy of regulating the first actual output voltage Vdc1 and the first actual output current Idc1.

[0158] In one embodiment, the outputs of the second input voltage loop and the second bus voltage loop are also a reference current, therefore, as Figure 8 As shown, in addition to the second bus voltage loop 402, the second input voltage loop 404, and the second selector 406, the control loop of the second DC converter may also include a second current loop 408. The second current loop 408 can control the second DC converter according to the reference current output by the second input voltage loop and the second bus voltage loop.

[0159] Therefore, when the second selector selects the second bus voltage loop to control the second DC converter, such as Figure 6 and Figure 8 As shown, the process of controlling the second DC-DC converter in step S50 by using the second target voltage as the given value of the second bus voltage loop may include:

[0160] Step S51: Obtain the second actual bus voltage and the second actual input current of the second DC converter.

[0161] The second actual bus voltage Vbus2 of the second DC converter can be obtained by sampling the voltage on the second side of the second DC converter through a voltage sampling circuit, or by sampling the voltage on the negative half bus BUS- and the bus midpoint N.

[0162] The second actual input current Idc2 of the second DC converter can be obtained by sampling the current on the first side of the second DC converter through a current sampling circuit.

[0163] Step S52: Using the second target voltage as the given value of the second bus voltage loop, input the second actual bus voltage into the second bus voltage loop to obtain the second reference current.

[0164] The second input voltage loop can adjust the second reference current Iref2 based on the second target voltage Vref2 and the second actual bus voltage Vbus2. The second selector then outputs the second reference current Iref2 to the second current loop.

[0165] Step S53: Obtain the second target control parameters based on the second reference current and the second actual input current.

[0166] The second current loop can adjust the second target control parameter Scr2 based on the second reference current Iref2 and the second actual input current Idc2.

[0167] The second target control parameter Scr2 can be, for example, the duty cycle, frequency, or phase of the second DC converter. It can be flexibly selected according to the actual situation and is not specifically limited here.

[0168] Step S54: Output a second control signal according to the second target control parameters. The second control signal is used to control the operation of the second DC-DC converter.

[0169] The type of the second control signal S2 can be referred to the relevant description of the first control signal S1, and will not be repeated here.

[0170] Under the control of the second control signal S2, the second actual output voltage Vdc2 of the second DC converter can be adjusted to Vref2, and the second actual output current Idc2 of the second DC converter can be adjusted to Iref2.

[0171] Therefore, steps S51 to S54 above combine the second input voltage loop and the second current loop to obtain the second control signal S2. Since the second control signal S2 can be used to adjust the second actual bus voltage Vbus2 and the second actual input current Idc2 of the second DC converter, and the second actual bus voltage Vbus2 is fed back into the second bus voltage loop, and the second actual input current Idc2 is fed back into the second current loop, the above process can form a closed-loop regulation, thereby improving the immediacy and accuracy of adjusting the second actual bus voltage Vbus2 and the second actual input current Idc2.

[0172] In step S52, the second bus voltage loop can be adjusted based on the voltage difference between the second target voltage Vref2 and the second actual bus voltage Vbus2 to obtain the second reference current Iref2. This process can be referred to the aforementioned step S42, and will not be repeated here.

[0173] In step S53, the second current loop can perform deviation processing based on the current difference between the second reference current Iref2 and the second actual input current Idc2 to obtain the second target control parameter Scr2. This process can be referred to the aforementioned step S43, and will not be repeated here.

[0174] When the second selector selects the second input voltage loop to control the second DC-DC converter, such as Figure 7 As shown, this control process is similar to step S50, so you can refer to the relevant description of step S50, which will not be described in detail here.

[0175] It should be noted that the control loops of the first and second DC-DC converters described above are merely illustrative examples provided in this application. This application does not limit the specific composition of the control loops of the first and second DC-DC converters. For example, some components can be combined or separated, some components can be omitted or other components can be added (for example, the control loop of the second DC-DC converter can omit the second input voltage loop 404 and the second selector 406, and only include the second bus voltage loop 402). Alternatively, it can be replaced with a combination of voltage loop and current loop, or a combination of voltage loop and power loop, etc., and can be adjusted accordingly based on the actual situation. This application does not list all of these possibilities.

[0176] It should be understood that when the first DC converter is running in reverse, the first output voltage loop 401 serves as the input voltage loop of the first DC converter, and the first bus voltage loop 403 serves as the output voltage loop of the first DC converter. The controller 400 can still control the operation of the first DC converter through one of these two voltage loops and through the first current loop.

[0177] When the second DC-DC converter is running in the forward direction, the second input voltage loop 404 serves as the output voltage loop of the second DC-DC converter, and the second bus voltage loop 402 serves as the input voltage loop of the second DC-DC converter. The controller 400 can still control the operation of the second DC-DC converter through one of these two voltage loops and through the second current loop.

[0178] In some embodiments, such as Figure 2 As shown, the battery heating circuit includes a heating element R1 connected in series and a heating switch K1. Therefore, as Figure 3 As shown, the control method may include:

[0179] Step S80: When the actual battery temperature is equal to or higher than the preset lower limit, control the heating switch to turn off so that the heating element stops working.

[0180] Step S80 can be executed after step S70, or simultaneously with step S70.

[0181] Therefore, through step S80, the battery heating circuit can be automatically disconnected when the battery temperature is normal, stopping the heating of the battery and preventing the battery temperature from becoming too high due to continuous heating, thus protecting the battery safety.

[0182] Step S90: When the actual battery temperature is lower than the preset lower limit and the discharge switch is off, control the heating switch to turn on so that the heating element can perform heating.

[0183] Step S90 can be executed after step S40 or simultaneously with step S40.

[0184] Therefore, through step S90, the battery heating circuit can be automatically connected when the battery is at a low temperature to heat the battery and prevent the battery from being unusable due to excessively low temperature.

[0185] In addition, simulation experiments were conducted to verify the control effect of the control method in the embodiments of this application.

[0186] In the simulation experiment, the total DC bus voltage VBUS was 820V, the actual battery voltage Vbat was 20V, the operating frequency of the first DC-DC converter and the second DC-DC converter was 30kHz, the duty cycle was 50%, and the heating element was a heating film, which can be equivalent to an 800Ω resistor. Furthermore, the setpoints Vset_bus1 of the first bus voltage loop 403 and Vset_bus2 of the second bus voltage loop 402 were both set to 400V, and the target value Vset_out1 of the first output voltage loop 401 was set to 18V.

[0187] Figure 9 The waveforms of the voltage Vdc1 on the first side of the first DC-DC converter and the voltage Vdc2 on the first side of the second DC-DC converter are shown during the T1 period, when the battery temperature is normal.

[0188] Figure 10 The waveforms of the voltage Vbus1 on the first side of the first DC-DC converter and the voltage Vbus2 on the first side of the second DC-DC converter are shown in the case of low battery temperature during the T2 period following the T1 period.

[0189] Figure 11 The waveforms of the current Idc1 on the first side of the first DC-DC converter and the current Idc2 on the first side of the second DC-DC converter are shown when the battery temperature is too low during the T2 period.

[0190] Figure 12 The waveforms of the current Ibus1 on the positive half bus BUS+ and the current Ibus2 on the negative half bus BUS- are shown in the T2 period when the battery temperature is too low.

[0191] The data on the horizontal and vertical axes are for illustrative purposes only and may vary in different experiments, which does not constitute a limitation of this application.

[0192] Specifically, during period T1, controller 400 turns on discharge switch Q1, and the first and second DC-DC converters operate in the same direction, allowing the battery to transfer electrical energy to the DC bus through the first and second DC-DC converters. The battery heating circuit is not activated. Therefore, from Figure 9 It can be seen that Vdc1, the output of the first side of the first DC-DC converter, and Vdc2, the output of the first side of the second DC-DC converter, are both stable at 18V.

[0193] During period T2, controller 400 controls discharge switch Q1 to turn off, the first DC converter operates in the forward direction, the second DC converter operates in the reverse direction, and the battery heating circuit is activated, so that the electrical energy of the DC bus is supplied to the battery heating circuit through the first DC converter and the second DC converter, and the battery heating circuit heats the battery.

[0194] When the battery heating circuit is activated, it is momentarily switched to the negative busbar BUS-, meaning the negative busbar BUS- is loaded while the positive busbar BUS+ is unloaded. This causes the voltage Vbus2 on the negative busbar BUS- to drop, and the current Idc2 to rise rapidly to supply the battery heating circuit. Therefore, if... Figure 10 , Figure 11 and Figure 12 As shown, Vbus2 oscillates, and the current Idc2 also oscillates and is a positive current. The current Ibus2 oscillates in tandem with Vbus2. Correspondingly, Vbus1 also oscillates, and the current Idc1 oscillates and is a negative current. The current Ibus1 also oscillates.

[0195] At this time, the controller 400 can execute the control method of the present application embodiment to regulate the first DC converter and the second DC converter. Therefore, the body diode D1 of the discharge switch Q1 can be turned off, the first DC converter cannot charge the battery through the body diode D1, so Ibat = 0V, and the output Vbus2 of the second DC converter can be adjusted to 410V (i.e., Vbus2 = VBUS / 2) and kept stable. Correspondingly, the Vbus1 of the first DC converter is also adjusted to 410V (i.e., Vbus1 = VBUS - Vbus2) and kept stable. The magnitudes of currents Idc1 and Idc2 are stabilized at around 2.5V, and the magnitudes of currents Ibus1 and Ibus2 are stabilized at around 0.5A (i.e., 410V / 800Ω ≈ 0.5A).

[0196] Therefore, from Figure 10 , Figure 11 and Figure 12 It can be seen that the waveforms of Vbus1 and Vbus2, Idc1 and Idc2, and Ibus1 and Ibus2 remain stable after a short period of oscillation.

[0197] Therefore, the control method of this application embodiment can prevent the battery from charging and discharging while the battery heating circuit heats the low-temperature battery by controlling the first DC converter and the second DC converter when the battery is at a low temperature, and can also effectively control the stability of voltage and current on the positive half bus and the negative half bus.

[0198] It should be noted that, for the sake of simplicity, the aforementioned method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps may be performed in other orders or simultaneously.

[0199] Please see Figure 13 This is a schematic diagram of a power conversion device provided in an embodiment of this application. The power conversion device 500 includes a power supply circuit 100 and a controller 400.

[0200] like Figure 2 and Figure 13 As shown, the power supply circuit 100 includes a first DC-DC converter 10 and a second DC-DC converter 20. The first sides of the first DC-DC converter 10 and the second DC-DC converter 20 are connected in parallel and then connected to the battery 200 through a discharge switch Q1. A body diode D1 is connected in parallel to the discharge switch Q1. The anode of the body diode D1 is connected to the first terminal of the discharge switch Q1, and the cathode of the body diode D1 is connected to the second terminal of the discharge switch Q1 and the battery 200. The second sides of the first DC-DC converter 10 and the second DC-DC converter 20 are connected in series through the midpoint N of the busbar and are respectively connected to each half of the DC busbar. A battery heating circuit 300 is connected in parallel to the second side of the second DC-DC converter 20. The first DC-DC converter 10, the second DC-DC converter 20, the discharge switch, and the battery heating circuit 300 are all connected to the controller 400.

[0201] In practical applications, the first DC converter 10, the second DC converter 20, the discharge switch Q1, the battery heating circuit 300, and the controller 400 can be set up independently, or at least partially integrated into one unit.

[0202] Under low-temperature conditions of battery 200, controller 400 can be used to execute the control method of the power supply circuit 100 described above, controlling the output of the first DC-DC converter 10 and the second DC-DC converter 20 in the power supply circuit 100. This ensures that the electrical energy from the half-DC bus, with both the channel and body diodes of the discharge switch transistor cut off, can be supplied to the battery heating circuit 300 after conversion by the first DC-DC converter 10 and the second DC-DC converter 20, thus powering the battery heating circuit 300. This design, on the one hand, achieves heating of the low-temperature battery 200 while avoiding charging and discharging of the low-temperature battery 200, and avoids the battery heating circuit 300 from being subjected to high voltage, which is beneficial to improving circuit safety performance. On the other hand, it can omit the charging switch transistor and reduce the voltage specifications of the components in the battery heating circuit 300, which is beneficial to reducing hardware costs.

[0203] The first DC-DC converter 10, the second DC-DC converter 20, the discharge switch Q1, the battery heating circuit 300, the controller 400, and the control method can all refer to the relevant descriptions in the foregoing embodiments, and will not be repeated here.

[0204] Please see Figure 2 This is a schematic diagram of an energy storage device provided in an embodiment of this application.

[0205] like Figure 2 As shown, the energy storage device 1000 includes a battery 200, a discharge switch Q1, a power supply circuit 100, a battery heating circuit 300, and a controller 400. The battery 200, discharge switch Q1, power supply circuit 100, battery heating circuit 300, and controller 400 can all be referred to in the relevant descriptions of the foregoing embodiments, and will not be repeated here.

[0206] In practical applications, the battery 200, discharge switch Q1, power supply circuit 100, battery heating circuit 300 and controller 400 can be set up independently, or at least partially integrated into one unit.

[0207] It should be understood that other aspects of the energy storage device 1000 can be found by referring to [the relevant documentation / reference]. Figures 2 to 8 The relevant descriptions in the foregoing embodiments shown will not be repeated here.

[0208] Please see Figure 14 The diagram shows a structural schematic of an electronic device provided in an embodiment of this application.

[0209] like Figure 14 As shown, the electronic device 600 may include a processor 601 and a memory 602.

[0210] Processor 601 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0211] Memory 602 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto. Memory 602 may exist independently and be connected to processor 601 via a bus. Memory 602 may also be integrated with processor 601.

[0212] The memory 602 stores programs, instructions, or code for executing the control method described above. The processor 601 executes the programs, instructions, or code stored in the memory 602. The programs, instructions, or code stored in the memory 602 can execute some or all of the steps of the control method described above.

[0213] Please see Figure 15 The diagram illustrates a control device provided in an embodiment of this application. This control device can be used to implement the control method for the power supply circuit described above.

[0214] Specifically, such as Figure 15 As shown, the control device 700 includes an acquisition module 701 and a control module 702.

[0215] The acquisition module 701 is used to acquire the actual battery temperature and actual battery voltage, as well as the on / off state of the discharge switch.

[0216] The control module 702 is used to control the first DC-DC converter with a first target voltage as the given value of the first output voltage loop when the actual battery temperature is lower than the preset lower limit and the discharge switch is off, so that the first side of the first DC-DC converter outputs the corresponding first target voltage; and to control the second DC-DC converter with a second target voltage as the given value of the second bus voltage loop, so that the second side of the second DC-DC converter outputs the corresponding second target voltage to the battery heating circuit; the first target voltage is less than the actual battery voltage.

[0217] It is understood that the division of the various modules in the control device 700 described above is only for illustrative purposes. In other embodiments, the control device 700 may be divided into different modules as needed to complete all or part of the functions of the control device 700.

[0218] The specific implementation of each module in the embodiments of this application can also refer to the corresponding description of the above control method embodiments, so it will not be described in detail here.

[0219] In the various embodiments of this application, all functional modules can be integrated into one processing module / unit, or each module can be a separate module, or two or more modules can be integrated into one module; the integrated module can be implemented in hardware or in the form of hardware plus software functional modules.

[0220] If the integrated modules described above in this application are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROM, RAM, magnetic disks, or optical disks.

[0221] This application also provides a computer-readable storage medium for storing computer programs or code, which, when loaded and executed by a processor, implement all or part of the steps in the above-described control method embodiments. The computer-readable storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Specific embodiments of the computer-readable storage medium can be found in [reference needed]. Figure 14 The description of memory 602 in the memory is not repeated here.

[0222] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A control method for a power supply circuit, characterized in that, The power supply circuit includes a first DC-DC converter and a second DC-DC converter. The first side of the first DC-DC converter and the second DC-DC converter are connected in parallel and then connected to the battery through a discharge switch. A body diode is connected in parallel to the discharge switch. The anode of the body diode is connected to the first end of the discharge switch, and the cathode of the body diode is connected to the second end of the discharge switch and the battery. The second side of the first DC-DC converter and the second DC-DC converter are connected in series through the midpoint of the bus and are respectively connected to each half of the DC bus. A battery heating circuit is connected in parallel to the second side of the second DC-DC converter. The control method includes: The actual battery temperature and actual battery voltage of the battery, as well as the on / off state of the discharge switch tube, are obtained. When the actual battery temperature is lower than the preset lower limit and the discharge switch is turned off, the first DC-DC converter is controlled with the first target voltage as the given value of the first output voltage loop, so that the first side of the first DC-DC converter outputs the corresponding first target voltage; and the second DC-DC converter is controlled with the second target voltage as the given value of the second bus voltage loop, so that the second side of the second DC-DC converter outputs the corresponding second target voltage to the battery heating circuit. The first target voltage is less than the actual battery voltage.

2. The control method as described in claim 1, characterized in that, The control of the first DC-DC converter using the first target voltage as the setpoint for the first output voltage loop includes: Obtain the first actual output voltage and the first actual output current of the first DC-DC converter; Using the first target voltage as the given value of the first output voltage loop, the first actual output voltage is input into the first output voltage loop to obtain the first reference current; The first target control parameters are obtained based on the first reference current and the first actual output current. A first control signal is output based on the first target control parameter, and the first control signal is used to control the operation of the first DC converter.

3. The control method as described in claim 2, characterized in that, The step of using the first target voltage as the given value of the first output voltage loop, and inputting the first actual output voltage into the first output voltage loop to obtain the first reference current, includes: Subtract the first target voltage from the first actual output voltage to obtain the first voltage difference; The first voltage difference is processed to obtain the first initial current; The first initial current is limited to obtain the first reference current.

4. The control method as described in claim 2, characterized in that, The control of the second DC-DC converter using the second target voltage as the setpoint for the second bus voltage loop includes: Obtain the second actual bus voltage and the second actual input current of the second DC converter; Using the second target voltage as the given value of the second bus voltage loop, the second actual bus voltage is input into the second bus voltage loop to obtain the second reference current; The second target control parameters are obtained based on the second reference current and the second actual input current; A second control signal is output based on the second target control parameter, and the second control signal is used to control the operation of the second DC converter.

5. The control method according to any one of claims 1 to 4, characterized in that, The control method further includes: When the actual battery temperature is equal to or higher than the preset lower limit, the first DC-DC converter is controlled with the second target voltage as the given value of the first bus voltage loop, so that the second side of the first DC-DC converter receives the corresponding second target voltage.

6. The control method as described in claim 5, characterized in that, The control loop of the first DC-DC converter includes a first output voltage loop, a first bus voltage loop, and a selector. The selector is used to select the first output voltage loop to control the first DC-DC converter when the actual battery temperature is lower than the preset lower limit, and to select the first bus voltage loop to control the first DC-DC converter when the actual battery temperature is equal to or higher than the preset lower limit.

7. The control method as described in claim 6, characterized in that, The selector is a smaller value selector, which is used to output the smaller value between the output of the first output voltage loop and the output of the first bus voltage loop. The step of selecting the first output voltage loop to control the first DC-DC converter when the actual battery temperature is lower than the preset lower limit, and selecting the first bus voltage loop to control the first DC-DC converter when the actual battery temperature is equal to or higher than the preset lower limit, includes: When the actual battery temperature is lower than the preset lower limit, the first DC-DC converter is controlled with the first target voltage as the given value of the first output voltage loop, so that the output of the first output voltage loop is less than the output of the first bus voltage loop, and the output of the first output voltage loop is selected as the output of the smaller element. When the actual battery temperature is equal to or higher than the preset lower limit, the first DC-DC converter is controlled with the third target voltage as the given value of the first output voltage loop, so that the output of the first output voltage loop is greater than the output of the first bus voltage loop, and the output of the first bus voltage loop is selected as the output of the smaller element; the third target voltage is greater than the actual battery voltage.

8. The control method according to any one of claims 1 to 7, characterized in that, The battery heating circuit includes a heating element and a heating switch connected in series; the control method further includes: When the actual battery temperature is lower than the preset lower limit and the discharge switch is off, the heating switch is turned on to enable the heating element to perform heating. When the actual battery temperature is equal to or higher than the preset lower limit, the heating switch is turned off to stop the heating element from working.

9. A power conversion device, characterized in that, The power conversion device includes a power supply circuit and a controller. The power supply circuit includes a first DC-DC converter and a second DC-DC converter. The first side of the first DC-DC converter and the second DC-DC converter are connected in parallel and then connected to the battery through a discharge switch. A body diode is connected in parallel to the discharge switch. The anode of the body diode is connected to the first end of the discharge switch, and the cathode of the body diode is connected to the second end of the discharge switch and the battery. The second side of the first DC-DC converter and the second DC-DC converter are connected in series through the midpoint of the bus and are respectively connected to each half of the DC bus. A battery heating circuit is connected in parallel to the second side of the second DC-DC converter. The controller is used to execute the control method as described in any one of claims 1 to 8.

10. An energy storage device, characterized in that, include: The system comprises a battery, a discharge switch, a power supply circuit, a battery heating circuit, and a controller. The power supply circuit includes a first DC-DC converter and a second DC-DC converter. The first and second DC-DC converters are connected in parallel on their first sides and then connected to the battery through the discharge switch. A body diode is connected in parallel to the discharge switch. The anode of the body diode is connected to the first end of the discharge switch, and the cathode of the body diode is connected to the second end of the discharge switch and the battery. The second sides of the first and second DC-DC converters are connected in series through the midpoint of a busbar and are respectively connected to each half of the DC busbar. The battery heating circuit is connected in parallel to the second side of the second DC-DC converter. The controller is used to execute the control method according to any one of claims 1 to 8.

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