Control method of dual active bridge converter, power conversion device and energy storage equipment

Abstract

The invention provides a control method of a dual active bridge converter, a power conversion device and energy storage equipment. The dual-active bridge converter comprises a primary side bridge arm and a secondary side bridge arm. The method comprises the following steps: acquiring a primary side input sampling value, a secondary side output sampling value and a target output voltage of the dual-active bridge converter; when the working condition of the dual active bridge converter is a light load working condition, determining a first control signal of a primary side bridge arm according to the target output voltage, the primary side input sampling value and the secondary side output sampling value; and controlling a switching tube of the primary side bridge arm to work according to the first control signal, and controlling a switching tube of the secondary side bridge arm to be kept closed. According to the control method provided by the invention, the switching loss can be reduced under the light-load working condition, and the noise problem is relieved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and particularly to a control method for a dual active bridge converter, a power conversion device, and an energy storage device. Background Art

[0002] With the development of the energy storage industry, the dual active bridge (DAB) converter has been increasingly widely used. Its excellent bidirectional power conversion response, high power density, and high conversion efficiency characteristics perform well in various application scenarios. However, the DAB converter has a low light load efficiency and large switching losses. In related technologies, a method of periodically blocking the wave is adopted, where the driving is turned off for a period of time and then the switching tubes are normally driven to act for a period of time to reduce the operating frequency of the switching tubes, thereby reducing the switching losses. However, this will cause problems with transformer noise, greatly affecting the user experience of using the device. Summary of the Invention

[0003] In view of this, the present application provides a control method for a dual active bridge converter, a power conversion device, and an energy storage device, which can reduce switching losses under light load conditions and alleviate the noise problem.

[0004] In a first aspect of the present application, a control method for a dual active bridge converter is provided. The dual active bridge converter includes a primary side bridge arm and a secondary side bridge arm. The method includes: obtaining a primary side input sampling value, a secondary side output sampling value, and a target output voltage of the dual active bridge converter; when the operating condition of the dual active bridge converter is a light load condition, determining a first control signal for the primary side bridge arm according to the target output voltage, the primary side input sampling value, and the secondary side output sampling value; controlling the switching tubes of the primary side bridge arm to work according to the first control signal, and controlling the switching tubes of the secondary side bridge arm to remain off.

[0005] In an embodiment, the primary side bridge arm includes a first bridge arm and a second bridge arm, and the light load condition includes a first light load condition. When the operating condition of the dual active bridge converter is the first light load condition, the first control signal includes a first driving signal and a second driving signal. The duty cycles of the first driving signal and the second driving signal are both 50%, and the first driving signal and the second driving signal are staggered by a phase difference of an internal phase shift angle; controlling the switching tubes of the primary side bridge arm to work according to the first control signal includes: controlling the switching tubes on the first bridge arm to alternately conduct according to the first driving signal, and controlling the switching tubes on the second bridge arm to alternately conduct according to the second driving signal.

[0006] In one embodiment, the primary bridge arm includes a first bridge arm and a second bridge arm. The first bridge arm includes a first upper switch and a first lower switch, and the second bridge arm includes a second upper switch and a second lower switch. The light load condition includes a second light load condition. When the operating condition of the dual-active-bridge converter is the second light load condition, the first control signal includes a third drive signal for driving the second lower switch. Controlling the switching tubes of the primary bridge arm according to the first control signal includes: controlling the first upper switch to remain conducting; controlling the first lower switch to remain off; controlling the second lower switch to conduct periodically according to the third drive signal; and controlling the second upper switch to remain off or controlling the second upper switch and the second lower switch to conduct complementarily.

[0007] In one embodiment, the secondary output sampling value includes the secondary output voltage, the primary input sampling value includes the primary input current, and the target output voltage includes the target output voltage. Determining the first control signal of the primary bridge arm according to the target output voltage, the primary input sampling value, and the secondary output sampling value includes: determining a reference input current according to the deviation between the secondary output voltage and the target output voltage; determining a target modulation parameter according to the deviation between the primary input current and the reference input current; and generating the first control signal according to the target modulation parameter.

[0008] In one embodiment, before determining the first control signal of the primary bridge arm according to the target output voltage, the primary input sampling value, and the secondary output sampling value, the method further includes: determining the operating condition of the dual-active-bridge converter according to the secondary output sampling value.

[0009] In one embodiment, the secondary output sampling value includes the secondary output power. Determining the operating condition of the dual-active-bridge converter according to the secondary output sampling value includes: when the secondary output power is greater than a first power threshold, determining that the operating condition of the dual-active-bridge converter is a non-light load condition; when the secondary output power is less than or equal to the first power threshold, determining that the operating condition of the dual-active-bridge converter is a light load condition.

[0010] In one embodiment, the light load condition includes a first light load condition and a second light load condition. Determining the operating condition of the dual-active-bridge converter according to the secondary output sampling value further includes: when the secondary output power is greater than a second power threshold and less than or equal to the first power threshold, determining that the operating condition of the dual-active-bridge converter is the first light load condition; when the secondary output power is less than or equal to the second power threshold, determining that the operating condition of the dual-active-bridge converter is the second light load condition.

[0011] In one embodiment, the method further includes: when the operating condition of the dual-active-bridge converter is a non-light load condition, controlling the switching tubes on the primary bridge arm and the secondary bridge arm to operate according to a preset regulation strategy.

[0012] The second aspect of the present application provides a power conversion device, including a dual active bridge converter and a controller. The controller is configured to execute the control method of the dual active bridge converter as described above.

[0013] The third aspect of the present application provides an energy storage device, including an energy storage battery and the power conversion device as described above. The energy storage battery is connected to the power conversion device to provide direct current to the power conversion device or store the direct current output by the power conversion device.

[0014] In summary, for the control method of the dual active bridge converter provided by the present application, when the DAB converter is in a light load condition, first, a first control signal of the primary bridge arm is determined according to the target output voltage, the primary side input sampling value, and the secondary side output sampling value, so as to control the switching tubes of the primary bridge arm to work according to the first control signal, and at the same time, control the switching tubes of the secondary bridge arm to remain off. In this way, compared with the control method in the related art that turns off the drive for a period of time and then drives the switching tubes normally for a period of time to reduce the switching frequency of the switching tubes when the dual active bridge converter is in light load, the control method provided by the present application directly reduces the number of switching tube actions of the DAB converter by controlling the switching tubes on the secondary bridge arm to remain off when the DAB converter is in a light load condition, thereby reducing the switching loss of the DAB converter in the light load condition, rather than reducing the switching frequency of the switching tubes in the related art, and thus can also alleviate the noise problem of the DAB converter. Description of the Drawings

[0015] To more clearly illustrate the technical solutions of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the protection scope of the present application. In each drawing, similar components are numbered similarly.

[0016] Figure 1 It is a circuit diagram of a dual active bridge converter provided by an embodiment of the present application.

[0017] Figure 2 It is a schematic flow chart of a control method of a dual active bridge converter provided by an embodiment of the present application.

[0018] Figure 3 It is a timing diagram of drive signals of each switching tube and the voltage Vab between the a terminal and the b terminal of the DAB converter under the first light load condition in an embodiment of the present application.

[0019] Figure 4 For Figure 3 It is an equivalent circuit diagram of the DAB converter corresponding to the shown timing diagram.

[0020] Figure 5Schematic diagram of the sub - step process for the DAB converter to control the switching tubes of the primary - side bridge arm according to the first control signal under the second light - load condition.

[0021] Figure 6 In an embodiment of the present application, timing diagram of the drive signals of each switching tube and the voltage Vab between the a - end and the b - end of the DAB converter under the second light - load condition.

[0022] Figure 7 For Figure 6 Equivalent circuit diagram of the DAB converter corresponding to the shown timing diagram.

[0023] Figure 8 Schematic diagram of the sub - step process of step S202 provided in an embodiment of the present application.

[0024] Figure 9 Specific control block diagram of the control method of the dual - active - bridge converter provided in an embodiment of the present application.

[0025] Figure 10 Module block diagram of the power conversion device provided in an embodiment of the present application.

[0026] Figure 11 Module block diagram of the energy storage device provided in an embodiment of the present application.

[0027] Figure 12 Module block diagram of the power device provided in an embodiment of the present application.

[0028] Figure 13 Module block diagram of the electronic device provided in an embodiment of the present application.

[0029] Figure 14 Function block diagram of the control device provided in an embodiment of the present application.

[0030] Figure 15 Function block diagram of the computer - readable storage medium provided in an embodiment of the present application. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0032] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component present at the same time. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component present at the same time. The terms "top", "bottom", "upper", "lower", "left", "right", "front", "rear", and similar expressions used in this article are only for the purpose of illustration.

[0033] Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0034] Some embodiments will be described below with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0035] With the development of the energy storage industry, the Dual Active Bridge (DAB) converter has been increasingly widely used. Its excellent bidirectional power conversion response, high power density, and high conversion efficiency characteristics perform well in various application scenarios. However, the DAB converter has low light-load efficiency and large switching losses. In related technologies, the method of periodic wave blocking is adopted, where the driving is turned off for a period of time and then the switching tubes are normally driven to act for a period of time to reduce the operating frequency of the switching tubes, thereby reducing the switching losses. However, this will bring the problem of transformer noise, which greatly affects the user experience of using the device.

[0036] Therefore, this application provides a control method, a power conversion device, and an energy storage device for a dual active bridge, which can reduce the switching losses under light-load conditions and alleviate the noise problem.

[0037] First, please refer to Figure 1 , Figure 1This is the circuit diagram of the Dual Active Bridge (DAB) converter involved in the embodiments of this application. Among them, the DAB converter 110 includes a primary bridge arm 11, a transformer 12, a secondary bridge arm 13, a primary input terminal, a secondary output terminal, and an inductor L1. Among them, the primary input terminal includes a positive input terminal VIN+ and a negative input terminal VIN-. The secondary output terminal includes a positive output terminal VOUT+ and a negative output terminal VOUT-. Specifically, the primary bridge arm 11 includes a first bridge arm 111 and a second bridge arm 112, and the secondary bridge arm 13 includes a third bridge arm 131 and a fourth bridge arm 132. Among them, the first bridge arm 111 includes a first upper switch Q1 (hereinafter referred to as switch Q1) and a first lower switch Q2 (hereinafter referred to as switch Q2), and the second bridge arm 112 includes a second upper switch Q3 (hereinafter referred to as switch Q3) and a second lower switch Q4 (hereinafter referred to as switch Q4). The third bridge arm 131 includes a third upper switch Q5 (hereinafter referred to as switch Q5) and a third lower switch Q6 (hereinafter referred to as switch Q6), and the fourth bridge arm 132 includes a fourth upper switch Q7 (hereinafter referred to as switch Q7) and a fourth lower switch Q8 (hereinafter referred to as switch Q8). The first end of switch Q1 and the first end of switch Q3 are connected to the positive input terminal VIN+. The second end of switch Q1 is connected to the first end of switch Q2 and is connected to one end of the primary side of transformer 12 through inductor L1. The second end of switch Q3 is connected to the first end of switch Q4 and the other end of the primary side of transformer 12. The second ends of switch Q2 and switch Q4 are connected to the negative input terminal VIN-. The first end of switch Q5 and the first end of switch Q7 are connected to the positive output terminal VOUT+. The second end of switch Q5 is connected to the first end of switch Q6 and is connected to one end of the secondary side of transformer 12. The second end of switch Q7 is connected to the first end of switch Q8 and the other end of the secondary side of transformer 12. The second ends of switch Q6 and switch Q8 are used to connect to the negative output terminal VOUT-. Switches Q1 to Q8 also each include a body diode and a parasitic capacitance.

[0038] The DAB converter 10 also includes a first bus capacitor C1 and a second bus capacitor C2. Among them, both ends of the first bus capacitor C1 are respectively connected to the positive input terminal VIN+ and the negative input terminal VIN-. Both ends of the second bus capacitor C2 are respectively connected to the positive output terminal VOUT+ and the negative output terminal VOUT-. The control ends of switches Q1 to Q8 are all connected to the controller of the DAB converter 10 ( Figure 1 (not shown). In this way, the controller can control the conduction and disconnection of each switch in the DAB converter 10. It can be understood that by controlling the conduction and disconnection of each switch in the primary bridge arm 11 and the secondary bridge arm 13 through different control strategies, the transmission power and output voltage of the DAB converter 10 can be adjusted.

[0039] For example, in some embodiments, the primary input terminal of the DAB converter 10 is used to connect to an energy storage device ( Figure 1 not shown), and the secondary output terminal is used to connect to a power supply ( Figure 1 not shown). When the power supply is connected to the DAB converter 10 and the DAB converter 10 provides direct current power to the energy storage device, the direct current power provided by the power supply is converted into an alternating square wave via the third bridge arm 131 and the fourth bridge arm 132. This alternating square wave is transmitted from the secondary side of the transformer 12 to the primary side of the transformer 12, and then converted into direct current power with the required voltage after voltage conversion by the inductor L1, the first bridge arm 111, and the second bridge arm 112 to charge the energy storage device.

[0040] Again, for example, in some other embodiments, the primary input terminal of the DAB converter 10 is used to connect to an energy storage device, and the secondary output terminal is used to connect to a load ( Figure 1 not shown). When the load is connected to the DAB converter 10 and power supply from the energy storage device 20 is required, the direct current power output by the energy storage device 20 is converted into an alternating square wave via the first bridge arm 111, the second bridge arm 112, and the inductor L1. This alternating square wave is transmitted from the primary side of the transformer 12 to the secondary side of the transformer 12, and then converted into direct current power required by the load after voltage conversion via the third bridge arm 131 and the fourth bridge arm 132.

[0041] In some embodiments, the primary input terminal and / or the secondary output terminal of the DAB converter 10 are also connected to devices such as a load, an energy storage device, and a power supply through a power conversion device. In this way, the power requirements of each device connected to the DAB converter 10 can be more flexibly met.

[0042] It can be understood that each switching tube in the DAB converter 10 may include a power transistor (GTR), a power field effect transistor (MOSFET), or an insulated gate bipolar transistor (IGBT), etc. There is a body diode included in each of the above GTR tubes, MOS tubes, and IGBT tubes. In other embodiments, the switching tube may also be formed by connecting a triode and a diode in parallel, and the present application does not limit this.

[0043] Please refer to Figure 2 , Figure 2 which is a schematic flowchart of the control method for a dual active bridge provided in an embodiment of the present application. It can be understood that this method can be executed by the controller of the dual active bridge converter. This method includes the following sub-steps:

[0044] Step S201: Obtain the primary input sampling value, the secondary output sampling value, and the target output voltage of the dual active bridge converter.

[0045] In some embodiments, a sampling circuit may be provided at the primary input end and the secondary output end of the DAB converter 10. The sampling circuit includes, but is not limited to, a voltage sampling circuit, a current sampling circuit, a power sampling circuit, etc. In this way, the actual primary input voltage, the actual primary input current, the actual primary input power, etc. can be sampled at the primary input end. Correspondingly, the actual secondary output voltage, the actual secondary output current, the actual secondary output power, etc. can be sampled at the secondary output end.

[0046] The target output voltage can be used to represent the target value related to the secondary output end of the DAB converter 10.

[0047] Step S202: When the operating condition of the dual active bridge converter is a light load condition, determine the first control signal of the primary bridge arm according to the target output voltage, the primary input sampling value, and the secondary output sampling value.

[0048] In step S202, based on a preset control loop, the first control signal of the primary bridge arm 11 can be determined according to the target output voltage, the primary input sampling value, and the secondary output sampling value. Among them, the preset control loop can be a feedback control loop. For example, the control loop can include at least one of a voltage loop, a current loop, a power loop, and other control loops. According to different designs of the preset control loop, different algorithms can be used to determine the first control signal. For example, in some embodiments, based on the preset control loop, the deviation between the target output voltage and the secondary output sampling value can be adjusted for deviation, and the first control signal can be determined according to the result obtained by the deviation adjustment and the primary input sampling value.

[0049] Among them, the primary input sampling value and the secondary output sampling value can be determined according to the specific control loop, and the present application does not limit the specific parameters included in the primary input sampling value and the secondary output sampling value.

[0050] Specifically, based on different preset control loops, the primary input sampling value can include at least one of the actual primary input voltage, the actual primary input current, and the actual primary input power, and the secondary output sampling value can include at least one of the actual secondary output voltage, the actual secondary output current, and the actual secondary output power.

[0051] The first control signal can include PWM (Pulse Width Modulation) signals for controlling each switching tube.

[0052] Step S203: Control the switching tubes of the primary bridge arm to work according to the first control signal, and control the switching tubes of the secondary bridge arm to remain off.

[0053] In step S203, while controlling the switching tubes of the primary bridge arm 11 according to the first control signal, the switching tubes of the secondary bridge arm 13 are controlled to remain off, which can reduce the number of switching actions of the switching tubes in the DAB converter 10 while ensuring normal power conversion of the DAB converter 10, thereby at least reducing the switching losses of the switching tubes in the secondary bridge arm 13.

[0054] For example, in some embodiments, when controlling the switching tubes of the primary bridge arm 11 according to the first control signal and controlling the switching tubes of the secondary bridge arm 13 to remain off so that the circuit of the DAB converter 10 is equivalent to a phase-shifted full-bridge circuit or a boost circuit, the power conversion of the DAB converter 10 can be ensured.

[0055] It can be understood that corresponding control signals can be output to the switching tubes on the secondary bridge arm 13 according to the types of the switching tubes on the secondary bridge arm 13 to keep the switching tubes off. For example, when the switching tubes on the secondary bridge arm 13 are MOS tubes, the controller can output a low-level signal to the control terminals of the switching tubes on the secondary bridge arm 13 to keep the switching tubes of the secondary bridge arm 13 off.

[0056] In summary, for the control method of the dual-active-bridge converter provided in this application, when the DAB converter 10 is in a light-load condition, first, the first control signal of the primary bridge arm is determined according to the target output voltage, the primary input sampling value, and the secondary output sampling value, and then the switching tubes of the primary bridge arm are controlled to work according to the first control signal, while the switching tubes of the secondary bridge arm are controlled to remain off. In this way, compared with the control method in the related art of driving the switching tubes to be off for a period of time and then driving them normally for a period of time to reduce the switching frequency of the switching tubes when the dual-active-bridge converter is lightly loaded, the control method provided in this application, when the DAB converter 10 is in a light-load condition, directly reduces the number of switching actions of the switching tubes in the DAB converter 10 by controlling the switching tubes on the secondary bridge arm 13 to remain off, thereby reducing the switching losses of the DAB converter 10 under the light-load condition, rather than reducing the switching frequency of the switching tubes in the related art, and thus can also alleviate the noise problem of the DAB converter.

[0057] In some embodiments, the light-load condition includes a first light-load condition. When the DAB converter 10 is in the first light-load condition, the first control signal includes a first driving signal and a second driving signal. The duty cycles of the first driving signal and the second driving signal are both 50%, and there is a phase difference of an internal phase-shift angle between the first driving signal and the second driving signal. Correspondingly, the controlling the switching tubes of the primary bridge arm according to the first control signal in step S203 includes:

[0058] Control the switching tubes on the first leg to conduct alternately according to the first driving signal, and control the switching tubes on the second leg to conduct alternately according to the second driving signal.

[0059] Please refer to Figure 1 , Figure 3 and Figure 4 . Among them, Figure 3 shows the timing diagrams of the driving signals of the switching tubes in the DAB converter 10 and the voltage Vab between the a and b ends in the DAB converter 10. Among them, in a complete switching cycle Ts, that is, in the time period from t0 to Ts, the operating conditions of the primary leg of the DAB converter 10 in the positive and negative half-cycles are symmetrical. Understandably, when controlling the operation of the DAB converter 10 according to the Figure 3 shown timing diagram, the DAB converter 10 is equivalent to the Figure 4 shown phase-shifted full-bridge circuit, and the secondary leg is equivalent to a full-bridge rectifier circuit.

[0060] Specifically, as Figure 3 shown, under the control of the first driving signal, the switching tubes on the first leg of the DAB converter 10, that is, the switching tubes Q1 and Q2, conduct alternately at high frequency; under the control of the second driving signal, the switching tubes on the second leg of the DAB converter 10, that is, the switching tubes Q3 and Q4, conduct alternately at high frequency. And because the first driving signal and the second driving signal are staggered by an internal phase-shift angle, two switching tubes in different legs and in the diagonal direction in the primary leg 11, that is, the switching tubes Q1 and Q4, the switching tubes Q2 and Q3, conduct or turn off successively with a certain phase angle difference. In this embodiment, the first driving signal includes a driving signal for controlling the switching tube Q1 and a driving signal for controlling the switching tube Q2. The second driving signal includes a driving signal for controlling the switching tube Q3 and a driving signal for controlling the switching tube Q4. The phase angle difference between the driving signals for controlling the switching tubes Q1 and Q4 is called the internal phase-shift angle Dy1. In this embodiment, the direction of power transfer in the dual-active-bridge converter 10 can be controlled by controlling the magnitude of the internal phase-shift angle Dy1.

[0061] Please refer to Figure 5 . In some other embodiments, the light-load condition includes a second light-load condition. Understandably, the required power of the load connected to the DAB converter 10 in the second light-load condition is less than the required power of the load connected to the DAB converter 10 in the first light-load condition. For example, the first light-load condition can be a light-load condition, and the second light-load condition can be a no-load condition.

[0062] When the operating condition of the dual-active-bridge converter is the second light-load condition, the first control signal includes a third driving signal for driving the second lower switch tube, and controlling the switching tubes of the primary bridge arm to operate according to the first control signal in step S203 includes:

[0063] Step S501: Control the first upper switch tube to remain conducting.

[0064] In some embodiments, when the first upper switch tube, i.e., the switch tube Q1, is a MOS tube, the controller may output a high-level signal to the control terminal of the switch tube Q1 to control the switch tube Q1 to remain conducting.

[0065] Step S502: Control the first lower switch tube to remain off.

[0066] In some embodiments, when the first lower switch tube, i.e., the switch tube Q2, is a MOS tube, the controller may output a low-level signal to the control terminal of the switch tube Q2 to control the switch tube Q2 to remain off.

[0067] Wherein, the voltage value of the low-level signal is less than the voltage value of the high-level signal. The present application does not limit the specific voltage values of the high-level signal and the low-level signal.

[0068] Step S503: Control the second lower switch tube to conduct periodically according to the third driving signal.

[0069] It can be understood that the duty ratio of the third driving signal can be calculated according to the target output voltage, the primary input sampling value and the secondary output sampling value in step S202.

[0070] Step S504: Control the second upper switch tube to remain off or control the second upper switch tube and the second lower switch tube to conduct complementarily.

[0071] In some embodiments, when the second upper switch tube, i.e., the switch tube Q3, is a MOS tube, the controller may output a low-level signal to the control terminal of the switch tube Q3 to control the switch tube Q3 to remain off.

[0072] In some embodiments, the controller may output a driving signal complementary to the third driving signal to the switch tube Q3 so that the switch tube Q3 and the switch tube Q4 conduct complementarily.

[0073] In this way, when controlling the primary bridge arm 11 according to steps S501 to S502, the primary circuit of the DAB converter 10 is equivalent to a Boost circuit.

[0074] For example, please refer to Figure 1 、 Figure 6 and Figure 7 . Among them, Figure 6A timing diagram showing the driving signals of each switching tube in the DAB converter 10 and the voltage Vab between the a - end and the b - end in the DAB converter 10 in an embodiment of the present application is shown. Among them, each switching tube of the primary bridge arm 11 of the DAB converter 10 operates periodically according to the switching period Ts, that is, the timing diagram in the time period from t0 to Ts. As Figure 6 shown, in the second light - load condition, the switching tube Q1 of the DAB converter 10 remains on, the switching tubes Q2 and Q3 remain off, and the switching tube Q4 conducts periodically. At this time, the DAB converter 10 is equivalent to Figure 7 the circuit diagram shown, and the primary circuit of the DAB converter 10 is equivalent to a Boost circuit.

[0075] It can be understood that, in this embodiment, when controlling the primary bridge arm 11 according to steps S501 to S502, the voltage Vab only changes in the positive half - cycle. Also, since the primary voltage of the transformer 12 is equal to the voltage Vab, and the primary current is positively correlated with the primary voltage, thus, the primary current of the transformer 12 also only changes in the positive half - cycle. Since the method provided in this embodiment is applied to the light - load condition of the DAB converter 10, at this time the primary current is small, so the control method provided in this embodiment generally does not exceed the magnetic saturation margin of the transformer 12, and the normal operation of the DAB converter 10 can be ensured.

[0076] Please refer to Figure 8 , in some embodiments, the secondary - side output sampling value includes the secondary - side output voltage, the primary - side input sampling value includes the primary - side input current, and step S202 includes the following sub - steps:

[0077] Step S801: Determine the reference input current according to the deviation between the secondary - side output voltage and the target output voltage.

[0078] Among them, the secondary - side output voltage can be the actual voltage of the secondary - side output terminal sampled at the secondary - side output terminal. The target output voltage is used to represent the target value of the actual voltage of the secondary - side output terminal. The voltage deviation value obtained by subtracting the secondary - side output voltage from the target output voltage can obtain the deviation between the secondary - side output voltage and the target output voltage.

[0079] In step S801, the voltage difference can be adjusted for deviation to obtain the reference input current. The deviation adjustment can be performed by proportional - integral - derivative adjustment, proportional - integral adjustment, or proportional adjustment. For example, inputting the voltage deviation value into a proportional - integral regulator or a proportional regulator can calculate the reference input current. Specifically, it can be realized through a voltage loop with a proportional - integral regulator or a proportional regulator.

[0080] Step S802: Determine the target modulation parameter according to the deviation between the primary - side input current and the reference input current.

[0081] Among them, the primary side input current can be the actual current at the primary side input terminal sampled at the primary side input terminal. The target modulation parameter is used to characterize the PWM modulation parameter associated with the duty cycle of each switch tube on the primary side bridge arm.

[0082] In step S802, a current deviation value obtained by subtracting the primary side input current from the reference input current can be obtained as the deviation between the primary side input current and the reference input current, and then the current deviation value is subjected to deviation adjustment to determine the target modulation parameter. Similarly, the deviation adjustment can be performed by proportional integral derivative adjustment, proportional integral adjustment, or proportional adjustment. For example, by inputting the current deviation value into a proportional integral regulator or a proportional regulator, the target modulation parameter can be calculated. Specifically, it can be implemented through a current loop with a proportional integral regulator or a proportional regulator.

[0083] Step S803: Generate a first control signal according to the target modulation parameter.

[0084] In step S803, the target modulation parameter can be subjected to pulse width (Pulse width modulation, PWM) modulation to generate a first control signal. Among them, the first control signal can include drive signals for driving each switch tube on the primary side bridge arm 11. And the drive signal can be a PWM signal.

[0085] It can be understood that in the first light load condition and the second light load condition mentioned in the above embodiments, different PWM modulation algorithms can be adopted. The present application does not limit the specific algorithm of PWM modulation.

[0086] In this way, in some embodiments, it can be based on Figure 8 the shown flow schematic diagram to generate a first control signal in step S202 to achieve the control of the DAB converter 10 under light load conditions.

[0087] Please continue to refer to Figure 9 , Figure 9 which shows the specific control block diagram of the DAB converter 10 implementing the control method of the dual active bridge converter provided by an embodiment of the present application. As Figure 9 shown, the control block diagram includes a voltage loop 21 and a current loop 22. The following will explain the specific working process of the control method of the dual active bridge converter according to Figure 9 this.

[0088] Specifically, in the voltage loop 21, the first adder 211 calculates the voltage deviation value Vdev based on the target output voltage Vref and the secondary side output voltage Vsamp. The first PI regulator 212 performs deviation adjustment on the voltage deviation value Vdev to obtain the reference input current Iref1. Then, the first limiter 213 performs a limiting process on the reference input current Iref1 to obtain the limited reference input current Iref2. In this way, the limited reference input current Iref2 can be within a reasonable range.

[0089] In the current loop 22, the second adder 221 calculates the current deviation value Idev based on the limited reference input current Iref2 and the primary side input current Isamp. The second PI regulator 222 performs deviation adjustment on the current deviation value Idev to obtain the target modulation parameter Pmod1. Then, the second limiter 223 performs a limiting process on the target modulation parameter Pmod1 to obtain the limited target modulation parameter Pmod2. In this way, when the primary side bridge arm 11 is controlled according to the limited target modulation parameter Pmod2, the primary side input current can be within a reasonable range. Then, the PWM modulator 224 calculates the first control signal PWM based on the limited target modulation parameter Pmod2, and outputs the first control signal PWM to the primary side bridge arm 11, so as to control the primary side bridge arm 11 to work while keeping the secondary side bridge arm 13 of the DAB converter 10 closed, thereby realizing the power conversion of the DAB converter 10 under light load conditions.

[0090] It can be understood that the above first PI regulator 213 and second PI regulator 223 take existing controllers in the related art, such as a PI controller (proportional integral controller) as an example. In other embodiments, other controllers such as a PID controller (proportional integral differentiation controller) etc. can also be used, and the present application does not limit this. Correspondingly, the deviation adjustment algorithm can also be a PID adjustment algorithm (Proportion Integration Differentiation control), a PI adjustment algorithm (proportional integral control), etc., and of course, it can also be other adjustment algorithms.

[0091] It can be understood that Figure 9 The control process of the shown control block diagram can be implemented by the inverter circuit control method provided by the present application, for example, implemented by a computer program stored in the controller, and the specific implementation details are not described herein again.

[0092] Understandably, in other embodiments, the first control signal may also be generated based on other voltage loops and current loops. For example, when the voltage loop 21 outputs the reference value of the secondary side output current, such as the reference output current, the feedback value of the current loop 22 can also be adjusted to the secondary side output current, that is, at this time, the target modulation parameter can be determined according to the deviation between the reference output current and the secondary side output current in the current loop 22.

[0093] In some embodiments, before performing step S202, the control method further includes:

[0094] Determine the operating condition of the dual active bridge converter according to the secondary side output sampling value.

[0095] In this way, when the operating condition of the DAB converter 10 is determined to be a light load condition according to the secondary side output sampling value and the control method provided in any of the above embodiments is executed, the switching loss of the switching tubes of the DAB converter 10 under the light load condition can be effectively reduced.

[0096] In some embodiments, the secondary side output sampling value includes the secondary side output power. Correspondingly, determining the operating condition of the dual active bridge converter according to the secondary side output sampling value includes:

[0097] When the secondary side output power is greater than the first power threshold, determine that the operating condition of the dual active bridge converter is a non-light load condition;

[0098] When the secondary side output power is less than or equal to the first power threshold, determine that the operating condition of the dual active bridge converter is a light load condition.

[0099] Among them, the secondary side output power may be the actual power sampled at the secondary side output end of the DAB converter 10. In other embodiments, the secondary side output voltage and the secondary side output current at the secondary side output end may also be sampled to calculate the secondary side output power.

[0100] The first power threshold is used to represent the critical power value between the light load condition and the non-light load condition. The first power threshold is less than the rated output power of the secondary side output end. The present application does not limit the specific value of the first power threshold.

[0101] In some embodiments, determining the operating condition of the dual active bridge converter according to the secondary side output sampling value further includes:

[0102] When the secondary side output power is greater than the second power threshold and less than or equal to the first power threshold, determine that the operating condition of the dual active bridge converter is the first light load condition;

[0103] When the secondary side output power is less than or equal to the second power threshold, determine that the operating condition of the dual active bridge converter is the second light load condition.

[0104] Among them, the first power threshold is greater than the second power threshold. For example, when the second power threshold is 0, the second light load condition may be an unloaded condition. The present application does not limit the specific values of the first power threshold and the second power threshold.

[0105] In some embodiments, when it is determined that the operating condition of the DAB converter 10 is the first light load condition, it can be based on Figure 3 or Figure 6 The timing diagram shown controls the operation of the primary bridge arm 11 of the DAB converter 10. When it is determined that the operating condition of the DAB converter 10 is the second light load condition, it can be based on Figure 6 The timing diagram shown controls the operation of the primary bridge arm 11 of the DAB converter 10. In this way, while reducing the switching loss of the switching tubes of the DAB converter 10 under the light load condition, the safety of the DAB converter 10 can be improved.

[0106] In some embodiments, the control method further includes:

[0107] When the operating condition of the dual active bridge converter is not a light load condition, control the switching tubes on the primary bridge arm and the secondary bridge arm to operate according to a preset regulation strategy.

[0108] It can be understood that compared with the light load condition, it is easier to achieve soft switching of the DAB converter 10 under the non-light load condition. At this time, the switching tubes on the primary bridge arm and the secondary bridge arm can be controlled according to the preset regulation strategy to improve the power conversion efficiency of the DAB converter 10. The present application does not specifically limit the preset regulation strategy. In this way, the control method of the dual active bridge converter provided by the present application can be flexibly controlled according to the operating condition of the DAB converter 10 and can be applied to more working scenarios.

[0109] Please refer to Figure 10 , the present application also provides a power conversion device 30, including a DAB converter 10 and a controller 20. The DAB converter 10 is connected to the controller 20, and the controller 20 is used to execute the control method of the dual active bridge converter described in any one of the above. In this way, the power conversion device 30 can reduce the switching loss of the switching tubes when the operating condition of the DAB converter 10 is a light load condition, and effectively alleviate the problem of relatively large noise of the DAB converter 10 under the light load condition.

[0110] Please refer to Figure 11 , the present application also provides an energy storage device 50, including a power conversion device 30 and an energy storage battery 40. The energy storage battery 40 can be used as a DC power source. The energy storage battery 40 can be connected to the power conversion device 30 and provide direct current for the power conversion device 30 or store the direct current output by the power conversion device 30. Among them, the power conversion device 30 and the energy storage battery 40 can be integrated or separated, and the embodiments of the present application do not limit this.

[0111] Understandably, the power conversion device 30 can be Figure 10 the power conversion device 30 shown. Therefore, under the control of the controller 20, the DAB converter 10 can either charge the energy storage battery 40 or discharge the energy storage battery 40.

[0112] Understandably, the energy storage device 50 can be applied to any energy storage system, such as a photovoltaic energy storage system, etc., which is not limited herein.

[0113] Please refer to Figure 12 , this application also provides a power device 60. The power device 60 can be applied to any electromechanical device product that requires power, such as a refrigerator, an air conditioner, an electric vehicle, etc., which is not limited herein.

[0114] As Figure 12 shown, the power device 60 may include a motor 61 and a power conversion device 30. The motor 61 can be connected to the power conversion device 30 and powered by the power conversion device 30.

[0115] Understandably, the power conversion device 30 can be Figure 10 the power conversion device 30 shown. Therefore, under the control of the controller 20, the DAB converter 10 can provide the required power for the motor 61 so that the motor 61 can start smoothly. In some embodiments, the motor 61 can be a DC motor. In some other embodiments, the power conversion device 30 further includes an inverter circuit ( Figure 12 not shown) connected to the motor 61. At this time, the motor 61 can also be an AC motor.

[0116] Please refer to Figure 13 , this application also provides an electronic device 70, including a controller 20 and a memory 71. Among them, the memory 71 is used to store programs, instructions or codes for executing the above control method of the dual active bridge converter. The controller 20 is used to execute the programs, instructions or codes stored in the memory 71. The programs, instructions or codes stored in the memory 71 can execute some or all of the steps of the control method of the dual active bridge converter in any of the above embodiments.

[0117] Please refer to Figure 14 , an embodiment of this application also provides a control device 80, which is applied to the DAB converter 10 or an electronic device integrated with the DAB converter 10. Figure 14 Schematically shows the structural block diagram of the control device 80 provided by the embodiment of this application. As Figure 14 shown, the control device 80 includes:

[0118] An acquisition module 81, configured to acquire the primary-side input sampling value, the secondary-side output sampling value, and the target output voltage of the dual-active-bridge converter.

[0119] A determination module 82, configured to determine a first control signal of the primary-side bridge arm according to the target output voltage, the primary-side input sampling value, and the secondary-side output sampling value when the operating condition of the dual-active-bridge converter is a light-load condition.

[0120] A control module 83, configured to control the switching tubes of the primary-side bridge arm to operate according to the first control signal, and to control the switching tubes of the secondary-side bridge arm to stay.

[0121] The specific details of the control device 80 provided in the embodiments of the present application for implementing the control method of the dual-active-bridge converter have been described in detail in the embodiments of the corresponding control method of the dual-active-bridge converter, and will not be elaborated here.

[0122] Please refer to Figure 15 , the present application further provides a computer-readable storage medium 90, on which a computer program 91 is stored. When the computer program 91 is executed by a controller, it implements the control method of the dual-active-bridge converter in the above technical solution. The computer-readable storage medium may adopt a portable compact disc read-only memory (CD-ROM) and include program codes, and may be run on a terminal device, such as a personal computer. However, the program product of the present invention is not limited thereto. In this document, the readable storage medium may be any tangible medium that contains or stores a program, and the program may be used by or in combination with an instruction execution system, apparatus, or device.

[0123] The above program product may adopt any combination of one or more readable media. The readable media may be a readable signal medium or a readable storage medium. The readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples (non-exhaustive list) of the readable storage medium include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0124] A computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, in which readable program code is carried. Such a propagated data signal may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the foregoing. The readable signal medium may also be any readable medium other than a readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device.

[0125] The program code contained on the readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wired, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0126] The program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages such as Java, C++, etc., and also including conventional procedural programming languages such as the "C" language or similar programming languages. The program code may be executed entirely on the user's computing device, partially on the user's device, executed as a stand-alone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user's computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., by connecting through the Internet using an Internet service provider).

[0127] In addition, the above drawings are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present invention, and are not for limiting purposes. It is easily understood that the processes shown in the above drawings do not indicate or limit the chronological order of these processes. Additionally, it is also easily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0128] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A control method for a dual-active-bridge converter, characterized in that The dual-active-bridge converter includes a primary bridge arm and a secondary bridge arm, and the method includes: Obtaining a primary input sampling value, a secondary output sampling value, and a target output voltage of the dual-active-bridge converter; When the operating condition of the dual-active-bridge converter is a light-load condition, determining a first control signal of the primary bridge arm according to the target output voltage, the primary input sampling value, and the secondary output sampling value; Controlling the switching tubes of the primary bridge arm to operate according to the first control signal, and controlling the switching tubes of the secondary bridge arm to remain off.

2. The method according to claim 1, wherein The primary bridge arm includes a first bridge arm and a second bridge arm, and the light-load condition includes a first light-load condition. When the operating condition of the dual-active-bridge converter is the first light-load condition, the first control signal includes a first driving signal and a second driving signal. The duty ratios of the first driving signal and the second driving signal are both 50%, and there is a phase difference of an internal phase-shift angle between the first driving signal and the second driving signal; The controlling the switching tubes of the primary bridge arm to operate according to the first control signal includes: Controlling the switching tubes on the first bridge arm to conduct alternately according to the first driving signal, and controlling the switching tubes on the second bridge arm to conduct alternately according to the second driving signal.

3. The method according to claim 1, wherein The primary bridge arm includes a first bridge arm and a second bridge arm. The first bridge arm includes a first upper switching tube and a first lower switching tube. The second bridge arm includes a second upper switching tube and a second lower switching tube. The light-load condition includes a second light-load condition. When the operating condition of the dual-active-bridge converter is the second light-load condition, the first control signal includes a third driving signal for driving the second lower switching tube; The controlling the switching tubes of the primary bridge arm to operate according to the first control signal includes: Controlling the first upper switching tube to remain on; Controlling the first lower switching tube to remain off; Controlling the second lower switching tube to conduct periodically according to the third driving signal; and Controlling the second upper switching tube to remain off or controlling the second upper switching tube and the second lower switching tube to conduct complementarily.

4. The method according to claim 1, wherein The secondary output sampling value includes a secondary output voltage, and the primary input sampling value includes a primary input current; The determining the first control signal of the primary bridge arm according to the target output voltage, the primary input sampling value, and the secondary output sampling value includes: Determining a reference input current according to the deviation between the secondary output voltage and the target output voltage; Determining a target modulation parameter according to the deviation between the primary input current and the reference input current; Generating the first control signal according to the target modulation parameter.

5. The method according to claim 1, characterized in that, Before the determining the first control signal of the primary bridge arm according to the target output voltage, the primary input sampling value, and the secondary output sampling value, the method further includes: Determining the operating condition of the dual-active-bridge converter according to the secondary output sampling value.

6. The method according to claim 5, characterized in that, The secondary output sampling value includes a secondary output power, and the determining the operating condition of the dual-active-bridge converter according to the secondary output sampling value includes: When the secondary side output power is greater than the first power threshold, it is determined that the operating condition of the dual active bridge converter is a non-light load condition; When the secondary side output power is less than or equal to the first power threshold, it is determined that the operating condition of the dual active bridge converter is the light load condition.

7. The method according to claim 6, characterized in that, The light load condition includes a first light load condition and a second light load condition. Determining the operating condition of the dual active bridge converter according to the secondary side output sampling value further includes: When the secondary side output power is greater than the second power threshold and less than or equal to the first power threshold, it is determined that the operating condition of the dual active bridge converter is the first light load condition; When the secondary side output power is less than or equal to the second power threshold, it is determined that the operating condition of the dual active bridge converter is the second light load condition.

8. The method according to claim 6, wherein The method further includes: When the operating condition of the dual active bridge converter is the non-light load condition, controlling the switching tubes on the primary side bridge arm and the secondary side bridge arm to operate according to a preset control strategy.

9. A power conversion device, the power conversion device comprising a dual active bridge converter and a controller, characterized in that, The controller is configured to execute the control method of the dual active bridge converter according to any one of claims 1 to 8.

10. An energy storage device, characterized in that, The energy storage device includes an energy storage battery and the power conversion device according to claim 9. The energy storage battery is connected to the power conversion device to provide direct current for the power conversion device or store the direct current output by the power conversion device.

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