Control method of parallel LLC circuit, power conversion device, energy storage device and medium

Abstract

The application provides a control method of a parallel LLC circuit, a power conversion device, an energy storage device and a medium. The control method of the parallel LLC circuit comprises: when the two LLC branches are not current-sharing, the turn-on delay time and the turn-off delay time of the output side bridge arm circuit switch tube on the target LLC branch are prolonged. The control method of the parallel LLC circuit provided by the application can improve the power conversion efficiency and reliability of the parallel LLC circuit.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method for a parallel LLC circuit, a power conversion device, an energy storage device, and a computer-readable storage medium. Background Technology

[0002] When parallel LLC circuits operate in parallel, the difference in resonant parameters between the two LLC branches often leads to inconsistent gain curves. Furthermore, because the parallel LLC branches in related technologies are often based on open-loop control circuits, meaning the duty cycle and switching frequency on the high-voltage side of the LLC branches are fixed, the LLC branches cannot actively adjust the current. Therefore, during operation, current imbalance occurs between the two parallel LLC branches, affecting the power conversion efficiency and reliability of the parallel LLC circuit. Summary of the Invention

[0003] In view of this, this application provides a control method, power conversion device, energy storage device, and computer-readable storage medium for a parallel LLC circuit, which can conveniently and effectively realize current sharing control of the parallel LLC circuit, thereby improving the power conversion efficiency and reliability of the parallel LLC circuit.

[0004] The first aspect of this application provides a control method for a parallel LLC circuit, the parallel LLC circuit comprising at least two LLC branches connected in parallel, each LLC branch comprising an input-side bridge arm circuit and an output-side bridge arm circuit. The control method includes: when the two LLC branches have uneven current distribution, extending the turn-on delay time and turn-off delay time of the switching transistors in the output-side bridge arm circuit of the target LLC branch, wherein the target LLC branch is the LLC branch with the larger branch current among the two LLC branches; the turn-on delay time is the duration between the rising edge of the drive signal of any switching transistor in the input-side bridge arm circuit of the target LLC branch and the rising edge of the drive signal of the corresponding switching transistor in the output-side bridge arm circuit; the turn-off delay time is the duration between the falling edge of the drive signal of any switching transistor in the input-side bridge arm circuit of the target LLC branch and the falling edge of the drive signal of the corresponding switching transistor in the output-side bridge arm circuit, and the turn-on delay time and turn-off delay time are equal.

[0005] In one embodiment, extending the turn-on delay time and turn-off delay time of the switch transistor on the output side bridge arm circuit of the target LLC branch includes: extending the turn-on delay time and turn-off delay time of the switch transistor on the output side bridge arm circuit of the target LLC branch according to a preset adjustment step size.

[0006] In one embodiment, after extending the turn-on delay time and turn-off delay time of the output side bridge arm circuit switch on the target LLC branch, the control method further includes: when the turn-on delay time and turn-off delay time are both greater than or equal to the maximum delay time, and the two LLC branches are not in equal current distribution, controlling the output power of the target LLC branch to be less than or equal to a preset power threshold.

[0007] In one embodiment, after extending the turn-on delay time and turn-off delay time of the switch transistor in the output side bridge arm circuit of the target LLC branch, the control method further includes: when both the turn-on delay time and the turn-off delay time are greater than or equal to the maximum delay time, controlling the switch transistor in the output side bridge arm circuit of the target LLC branch to remain open.

[0008] In one embodiment, before extending the turn-on delay time and turn-off delay time of the switch transistor in the output side bridge arm circuit of the target LLC branch, the control method further includes: when the current is shared between the two LLC branches, controlling the turn-on delay time and turn-off delay time of the switch transistor in the output side bridge arm circuit of each LLC branch to be a preset delay time.

[0009] In one embodiment, before extending the turn-on delay time and turn-off delay time of the output side bridge arm circuit switch on the target LLC branch, the control method further includes: acquiring the branch current of the two LLC branches respectively; determining that the two LLC branches are not current-equal when the absolute value of the difference between the two branch currents is greater than a preset threshold; and determining that the two LLC branches are current-equal when the absolute value of the difference between the two branch currents is less than or equal to the preset threshold.

[0010] In one embodiment, each LLC branch further includes a resonant cavity, and the input-side bridge arm circuit and the output-side bridge arm circuit are coupled through the resonant cavity. The resonant cavity includes a resonant inductor, a resonant capacitor, and a transformer. The branch current is any one of the input current, output current, and inductance current flowing through the resonant inductor of the LLC circuit.

[0011] A second aspect of this application provides a power conversion device, including a parallel LLC circuit and a controller. The parallel LLC circuit includes at least two LLC branches connected in parallel, each LLC branch including an input-side bridge arm circuit and an output-side bridge arm circuit, and the controller is used to execute the control method of the parallel LLC circuit as described in any of the preceding claims.

[0012] A third aspect of this application provides an energy storage device, including an energy storage battery and a 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 to store the direct current output by the power conversion device.

[0013] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, can implement the control method for the parallel LLC circuit as described in any of the preceding claims.

[0014] In summary, the control method for parallel LLC circuits provided in this application identifies the LLC branch with the larger branch current as the target LLC branch when the two LLC branches in the parallel LLC circuit have uneven current distribution. By extending the turn-on and turn-off delay times of the output-side bridge arm circuit switch on the target LLC branch, the conduction time of the body diode of the output-side bridge arm circuit switch is prolonged, thereby changing the gain of the target LLC circuit. Since the voltage drop of the body diode is greater than that of the switch, the output voltage of the output-side bridge arm circuit on the target LLC branch is reduced, thus pulling down the output current of the target LLC branch to achieve current sharing control. Furthermore, this application reduces the probability of energy flowing back from the output-side bridge arm circuit to the input-side bridge arm circuit by controlling the turn-on delay time to be equal to the turn-off delay time, thereby reducing the switching stress and electromagnetic interference of the output-side bridge arm circuit switch, simplifying the control logic, and improving control accuracy. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation on the scope of protection of this application. In the various drawings, similar components are numbered similarly.

[0016] Figure 1 This is a schematic diagram of a parallel LLC circuit according to an embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the drive signals for some of the switching transistors when the parallel LLC circuit provided in one embodiment of this application is in operation.

[0018] Figure 3 This is a schematic diagram of the drive signals of the switch Q1 on the input side bridge arm circuit and the corresponding switch Q5 on the output side bridge arm circuit when executing the control method of the parallel LLC circuit provided in this application in one embodiment of the present application.

[0019] Figure 4 This is a schematic diagram of some steps of a control method for a parallel LLC circuit before extending the turn-on delay time and turn-off delay time of the switch transistor in the output side bridge arm circuit of the target LLC branch, as provided in an embodiment of this application.

[0020] Figure 5A flowchart illustrating a control method for a parallel LLC circuit provided in an embodiment of this application.

[0021] Figure 6 In one embodiment of this application, when the two LLC branches in the parallel LLC circuit have uneven current distribution, and the turn-on delay time and turn-off delay time of the input-side bridge arm circuit switch in each LLC branch are consistent with the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch, the branch current waveform diagram of the two LLC branches is shown.

[0022] Figure 7 A schematic diagram of the branch current waveforms of the two LLC branches obtained after extending the turn-on delay time and turn-off delay time of the output side bridge arm circuit switch in the second LLC branch.

[0023] Figure 8 This is a schematic diagram of a power conversion device provided in an embodiment of this application.

[0024] Figure 9 A functional block diagram of an energy storage device provided in an embodiment of this application.

[0025] Figure 10 This is a functional block diagram of a control device provided in an embodiment of this application.

[0026] Figure 11 A functional block diagram of a computer-readable storage medium provided in an embodiment of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0028] 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 may also have an intervening component. When a component is considered to be "placed" on another component, it can be directly placed on the other component or may also have an intervening component.

[0029] 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.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0032] 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.

[0033] When parallel LLC circuits operate in parallel, the difference in resonant parameters between the two LLC branches often leads to inconsistent gain curves. Furthermore, because the parallel LLC branches in related technologies are often based on open-loop control circuits, meaning the duty cycle and switching frequency on the high-voltage side of the LLC branches are fixed, the LLC branches cannot actively adjust the current. Therefore, during operation, current imbalance may occur between the two parallel LLC branches, affecting the power conversion efficiency and reliability of the parallel LLC circuit.

[0034] Based on this, this application provides a control method, power conversion device, energy storage device, and computer-readable storage medium for a parallel LLC circuit, which can conveniently and effectively realize current sharing control of the parallel LLC circuit, thereby improving the power conversion efficiency and reliability of the parallel LLC circuit.

[0035] The parallel LLC circuit involved in this application includes two LLC branches, and each LLC branch includes an input-side bridge arm circuit and an output-side bridge arm circuit. The switching transistors of the input-side bridge arm circuit and the output-side bridge arm circuit correspond one-to-one.

[0036] Please see Figure 1 , Figure 1 This is a schematic diagram of a parallel LLC circuit according to an embodiment of this application. Figure 1 The parallel LLC circuit 10 shown is an example, which includes a first LLC branch 11 and a second LLC branch 12.

[0037] Taking the first LLC branch 11 as an example, the first LLC branch 11 includes a DC / AC conversion circuit 111, an AC / DC conversion circuit 112, and a resonant cavity 113. The DC / AC conversion circuit 111 and the AC / DC conversion circuit 112 are coupled through the resonant cavity 113.

[0038] The DC / AC conversion circuit 111 includes switching transistors Q1, Q2, Q3, and Q4. The AC / DC conversion circuit 112 includes switching transistors Q5, Q6, Q7, and Q8. The resonant cavity 113 includes a first resonant inductor L1, a first resonant capacitor C1, and a first transformer T1. The first terminals of switching transistors Q1 and Q3 are electrically connected to the positive DC bus BUS+. The second terminal of switching transistor Q1 is electrically connected to the first terminal of switching transistor Q2. The second terminal of switching transistor Q3 is electrically connected to the first terminal of switching transistor Q4. The second terminals of switching transistors Q2 and Q4 are both electrically connected to the negative DC bus BUS-. The first terminal of the first resonant capacitor C1 is electrically connected between the second terminals of switching transistors Q3 and Q4. The second terminal of the first resonant capacitor C1 is electrically connected to the first terminal of the first resonant inductor L1. The second terminal of the first resonant inductor L1 is electrically connected to the first terminal of the first winding of the transformer T1. The second terminal of the first winding of transformer T1 is electrically connected between the second terminal of switch Q1 and the first terminal of switch Q2. The first terminal of the second winding of transformer T1 is electrically connected to the second terminal of switch Q7. The second terminal of the second winding of transformer T1 is electrically connected to the second terminal of switch Q5. The first terminals of both switch Q7 and Q5 are electrically connected to the positive transmission bus BAT+. The second terminal of switch Q5 is also electrically connected to the first terminal of switch Q6. The second terminal of switch Q7 is also electrically connected to the first terminal of switch Q8. The second terminals of both switch Q6 and Q8 are electrically connected to the negative transmission bus BAT-.

[0039] In some embodiments, the second end of the first winding of transformer T1 is also electrically connected between the second end of switching transistor Q1 and the first end of switching transistor Q2 via a first current transformer CT1. Thus, the resonant cavity current can be acquired via the first current transformer CT1.

[0040] The DC / AC conversion circuit 111 includes two bridge arms. One bridge arm consists of switching transistors Q1 and Q2, and the other bridge arm consists of switching transistors Q3 and Q4. When the DC / AC conversion circuit 111 is operating, switching transistors Q1 and Q4 form one group, and switching transistors Q3 and Q2 form the other group. Switches in the same group are simultaneously turned on or off, while switches in different groups are turned on alternately. That is, in each cycle, one group of switches is on for half the cycle, and the other group is on for the other half. Furthermore, after one group of switches is turned off, the other group of switches is turned on only after a dead time delay. Switches Q5, Q6, Q7, and Q8 in the AC / DC conversion circuit 112 correspond one-to-one with switches Q1, Q2, Q3, and Q4 in the DC / AC conversion circuit 111. Furthermore, the working principle of AC / DC conversion circuit 112 is roughly the same as that of DC / AC conversion circuit 111, and will not be described in detail here.

[0041] For example, the DC / AC conversion circuit 111 in the first LLC branch 11 can serve as the high-voltage side, and the DC bus of the DC / AC conversion circuit 111, namely the positive DC bus BUS+ and the negative DC bus BUS-, is connected to, for example, a charger or a load. The AC / DC conversion circuit 112 in the first LLC branch 11 can serve as the low-voltage side, and the transmission bus of the AC / DC conversion circuit 112, namely the positive transmission bus BAT+ and the negative transmission bus BAT-, is connected to an energy storage battery or any device equipped with an energy storage battery, such as a battery pack. Furthermore, the first LLC branch 11 can realize bidirectional energy conversion between the high-voltage side and the low-voltage side.

[0042] In this configuration, when energy flows from the high-voltage side to the low-voltage side, the DC / AC conversion circuit 111 acts as the input-side bridge arm circuit to convert the DC power on the DC bus into AC power and output it to the resonant cavity 113. The AC / DC conversion circuit 112 acts as the output-side bridge arm circuit to convert the AC power output from the resonant cavity 113 into DC power and output it through the transmission bus. When energy flows from the low-voltage side to the high-voltage side, the AC / DC conversion circuit 112 acts as the input-side bridge arm circuit to convert the DC power on the transmission bus into AC power and output it to the resonant cavity 113. The DC / AC conversion circuit 111 acts as the output-side bridge arm circuit to convert the AC power output from the resonant cavity 113 into DC power and output it through the DC bus. In both cases, the four switches in the input-side bridge arm circuit correspond one-to-one with the four switches in the output-side bridge arm circuit.

[0043] The circuit structure and working principle of the second LLC branch 12 are roughly the same as those of the first LLC branch 11, and will not be described again here.

[0044] Understandably, the switching transistors mentioned in this application are, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors).

[0045] In the following embodiment, the control method of parallel LLC circuit is applied... Figure 1 The parallel LLC circuit 10 shown, with energy flowing from the high-voltage side to the low-voltage side, illustrates the working principle and process of the control method for the parallel LLC circuit provided in this application. It is worth noting that the control method for the parallel LLC circuit provided in this application can also be applied to scenarios where the AC / DC converter circuit 112 is used as the input-side bridge arm circuit and the DC / AC converter circuit 111 is used as the output-side bridge arm circuit. Furthermore, the control method for the parallel LLC circuit provided in this application, besides being applicable to… Figure 1 The parallel LLC circuit 10, which is composed of a bidirectional full-bridge LLC circuit, can also be applied to a parallel LLC circuit composed of a half-bridge LLC circuit, or to a parallel LLC circuit composed of a full-bridge circuit and a half-bridge circuit. Furthermore, the control method for the parallel LLC circuit provided in this application can also be applied to a parallel LLC circuit composed of a unidirectional LLC circuit.

[0046] The control method for the parallel LLC circuit provided in this application can be controlled by the controller of the parallel LLC circuit 10. Figure 1 (Not shown) This can be executed by a controller independent of the parallel LLC circuit 10, or by a controller that is independent of the parallel LLC circuit 10. The control method for the parallel LLC circuit includes: When the two LLC branches have uneven current, the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch on the target LLC branch are extended. The target LLC branch is the LLC branch with the larger branch current among the two LLC branches. The turn-on delay time is the time between the rising edge of the drive signal of any switch on the input side bridge arm circuit of the target LLC branch and the rising edge of the drive signal of the corresponding switch on the output side bridge arm circuit. The turn-off delay time is the time between the falling edge of the drive signal of any switch on the input side bridge arm circuit of the target LLC branch and the falling edge of the drive signal of the corresponding switch on the output side bridge arm circuit. The turn-on delay time and the turn-off delay time are equal.

[0047] In this embodiment, uneven current distribution between the two LLC branches refers to a current difference exceeding a preset threshold. It is understood that uneven current distribution between the two LLC branches in the parallel LLC circuit 10 may lead to inconsistent phase and amplitude of the output current in different LLC branches, resulting in significant ripple in the total output current after parallel connection, affecting power conversion efficiency and potentially interfering with the load. Furthermore, the LLC branch with the larger current needs to bear greater current stress, leading to increased heat generation. Prolonged uneven current distribution may increase the failure risk of the parallel LLC circuit 10. Therefore, it is necessary to control uneven current distribution between the two LLC branches of the parallel LLC circuit 10 in a timely manner.

[0048] First, during the operation of the parallel LLC circuit 10, when the input-side bridge arm circuit of each LLC branch performs inverter processing on the received DC power, the output-side bridge arm circuit should simultaneously perform rectification. Please refer to the following: Figure 2 Taking the first LLC branch 11 as an example, theoretically, during the operation of the first LLC branch 11, switching transistors Q1 and Q5 need to be switched simultaneously, Q3 and Q7 simultaneously, Q2 and Q6 simultaneously, and Q4 and Q8 simultaneously, so as to achieve synchronous rectification of the output-side bridge arm circuit following the input-side bridge arm circuit. Taking switching transistors Q1 and Q5 as an example, considering that actual applications may lead to energy backflow, switching transistor Q5 is turned on after a certain delay following the turn-on of Q1, and is turned off a certain period before Q1 is turned off. For example, switching transistor Q1 of the input-side bridge arm circuit turns on at time t0, and switching transistor Q5 of the output-side bridge arm circuit turns on at time t1 after time t0; switching transistor Q1 of the input-side bridge arm circuit turns off at time t3, and switching transistor Q5 of the output-side bridge arm circuit turns off at time t2 before time t3. Similarly, the other switches in the input-side bridge arm circuit and the corresponding switch Q7 in the output-side bridge arm circuit are treated similarly, and will not be elaborated further here. The time period from t0 to t1 is the turn-on delay time of switch 112 in the output-side bridge arm circuit, and the time period from t2 to t3 is the turn-off delay time of switch 112 in the output-side bridge arm circuit.

[0049] It is understandable that the body diode of switch Q5 is conducting between time t0 and time t1, and switch Q5 is conducting between time t1 and time t2. Obviously, since the voltage drop of the body diode is greater than that of the switch, the voltage loss of the body diode is greater. Therefore, when the turn-on delay time and turn-off delay time of switch Q5 are longer, that is, when the conduction time of the body diode of switch Q5 is longer, the output voltage of the first LLC branch 11 containing switch Q5 will decrease, thereby pulling down the output current of the first LLC branch 11. Therefore, the control method for the parallel LLC circuit provided in this application, after determining the target LLC branch with a larger branch current among the first LLC branch 11 and the second LLC branch 12 in parallel, can extend the turn-on delay time and turn-off delay time of the switch tube on the output side bridge arm circuit of the target LLC branch to reduce the output current of the target LLC branch, thereby reducing the difference between the branch currents of the two parallel LLC branches, so that the branch currents of the two LLC branches are closer, thus effectively realizing the current sharing control of the parallel LLC circuit 10.

[0050] For example, when the first LLC branch 11 is determined to be the target LLC branch, the turn-on delay time and turn-off delay time of the switching transistors in the output side bridge arm circuit of the target LLC branch can be extended. For example, for the switching transistor Q5 in the output side bridge arm circuit, the turn-on delay time and turn-off delay time can be extended. Figure 2 The turn-on delay time and turn-off delay time of the switch Q5 shown are extended to: Figure 3 The turn-on and turn-off delay times of switch Q5 are shown. Similarly, other switches on the target LLC branch perform similar operations, which will not be described further here.

[0051] Furthermore, in this embodiment, by controlling the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch to be equal, the probability of energy flowing back from the output-side bridge arm circuit to the input-side bridge arm circuit can be reduced. On the other hand, this ensures that the drive signal of the output-side bridge arm circuit switch is symmetrical within each half-cycle, reducing switching stress and electromagnetic interference caused by asymmetry. This helps balance the switching losses of the switch and makes the dynamic characteristics of the switch more consistent during turn-on and turn-off. Moreover, from a control logic perspective, controlling the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch to be equal simplifies the control logic and improves control accuracy.

[0052] Understandably, the extended turn-on delay time and turn-off delay time can be output to the dead time register of the pulse width modulation (WPM) module of the target LLC branch, and a PWM signal can be generated according to the extended turn-on delay time and turn-off delay time and the preset control algorithm to adjust the turn-on delay time and turn-off delay time of the switch of the output side bridge arm circuit of the target LLC branch, thereby reducing the branch current of the target LLC branch.

[0053] In summary, the control method for the parallel LLC circuit provided in this application, when the two LLC branches of the parallel LLC circuit 10 have uneven current, identifies the LLC branch with the larger branch current as the target LLC branch. By extending the turn-on and turn-off delay times of the output-side bridge arm circuit switch on the target LLC branch, the conduction time of the body diode of the output-side bridge arm circuit switch is extended, thereby changing the gain of the target LLC circuit. Since the voltage drop of the body diode is greater than that of the switch, the output voltage of the output-side bridge arm circuit on the target LLC branch is reduced, thus pulling down the output current of the target LLC branch to achieve current sharing control. Furthermore, this application also reduces the probability of energy flowing back from the output-side bridge arm circuit to the input-side bridge arm circuit by controlling the turn-on delay time to be equal to the turn-off delay time, thereby reducing the switching stress and electromagnetic interference of the output-side bridge arm circuit switch, simplifying the control logic, and improving control accuracy.

[0054] In some embodiments, after extending the turn-on delay time and turn-off delay time of the output side bridge arm circuit switch on the target LLC branch, if current sharing between the two LLC branches in the parallel LLC circuit is detected, the current turn-on delay time and turn-off delay time of the two LLC branches are maintained.

[0055] Please see Figure 4 In some embodiments, before extending the turn-on delay time and turn-off delay time of the output side bridge arm circuit switch on the target LLC branch, the control method of the parallel LLC circuit further includes the following steps S401-S403.

[0056] Step S401: Obtain the branch current of each LLC branch.

[0057] In some embodiments, the branch current can be any one of the input current, output current of the LLC branch, and inductance current flowing through the resonant inductor.

[0058] For example, this can be achieved through a current transformer, such as... Figure 1The first current transformer CT1 and the second current transformer CT2 shown collect the current flowing through the resonant cavity in the corresponding LLC branch as the branch current. That is, the first current transformer CT1 collects the inductance current flowing through the first resonant inductor L1 as the branch current of the first LLC branch 11, and the second current transformer CT2 collects the inductance current flowing through the second resonant inductor L2 as the branch current of the second LLC branch 12.

[0059] In other embodiments, a current sampling circuit can be provided in the input-side bridge arm circuit of each LLC branch to collect the input current of that LLC branch as the branch current. For example, taking the first LLC branch 11 as an example, a current sampling circuit can be provided between the first terminal of switch Q1 and the first terminal of switch Q3 to collect the input current.

[0060] In another embodiment, a current sampling circuit can be provided in the output-side bridge arm circuit of each LLC branch to collect the output current of that LLC branch as the branch current. For example, taking the first LLC branch 11 as an example, a current sampling circuit can be provided between the first terminal of switch Q5 and the first terminal of switch Q7 to collect the output current.

[0061] This application does not impose any restrictions on the specific circuit structure of the current sampling circuit.

[0062] Step S402: When the absolute value of the difference between the currents of the two branches is greater than a preset threshold, it is determined that the two LLC branches are not in equal current.

[0063] Step S403: When the absolute value of the difference between the currents of the two branches is less than or equal to a preset threshold, determine the current sharing of the two LLC branches.

[0064] In some embodiments, the absolute value of the difference between the branch current of the first LLC branch 11 and the branch current of the second LLC branch 12 can be calculated as the difference between the two branch currents.

[0065] This application does not limit the size of the preset threshold; the preset threshold can be limited according to the circuit parameters of the parallel LLC circuit 10.

[0066] In summary, by executing steps S401-S403, it can be determined whether the two LLC branches in the parallel LLC circuit 10 have uneven current distribution.

[0067] In some embodiments, extending the turn-on delay time and turn-off delay time of the switching transistors in the output-side bridge arm circuit of the target LLC branch includes: The turn-on delay time and turn-off delay time of the switch transistor on the output side bridge arm circuit of the target LLC branch are extended according to the preset adjustment step size.

[0068] The preset adjustment step size indicates the amount by which the turn-on delay time and turn-off delay time are increased each time. In other words, the turn-on delay time and turn-off delay time can be gradually extended based on the initial turn-on delay time and turn-off delay time of the switching transistors in the output bridge arm circuit, according to the preset adjustment compensation.

[0069] In some embodiments, the preset adjustment step size can be a preset value, and the preset adjustment step size can be set according to the specific circuit parameters of the parallel LLC circuit 10. This application does not limit the specific value of the preset adjustment step size. In this way, stable current sharing control can be achieved by gradually adjusting the turn-on delay time and the turn-off delay time.

[0070] In other embodiments, the preset adjustment step size can also be a dynamically changing value. Furthermore, the preset adjustment step size can be adjusted based on the difference between the branch currents of the two LLC branches. For example, the preset adjustment step size can be configured to have a positive correlation with the difference between the branch currents of the two LLC branches. Thus, when the difference between the branch currents of the two LLC branches is larger, a larger preset adjustment step size can cause the output current of the target LLC branch to decrease more quickly, thereby rapidly achieving current sharing control.

[0071] In summary, by performing the steps provided in this embodiment, the turn-on delay time and turn-off delay time of the switching transistors on the output side bridge arm circuit of the target LLC branch can be effectively adjusted.

[0072] In some embodiments, after extending the turn-on delay time and turn-off delay time of the switching transistor in the output side bridge arm circuit of the target LLC branch, the control method further includes: When both the turn-on delay time and the turn-off delay time are greater than or equal to the maximum delay time, and the two LLC branches have uneven current distribution, the output power of the target LLC branch is controlled to be less than or equal to the preset power threshold.

[0073] The maximum delay time represents the upper limit of the turn-on and turn-off delay times. The maximum delay time is less than or equal to half the product of the duty cycle and period of the drive signal of the switching transistor in the input bridge arm circuit. Specifically, when the maximum delay time is equal to half the product of the duty cycle and period of the drive signal of the switching transistor in the input bridge arm circuit, and both the turn-on and turn-off delay times are greater than or equal to the maximum delay time, then the switching transistor in the output bridge arm circuit is already off, and only the body diode of the switching transistor remains conducting.

[0074] In this embodiment, by controlling the output power of the target LLC branch to be less than or equal to a preset power threshold, the branch current of the target LLC branch is limited, thereby reducing the difference between the branch currents of the two LLC branches. The preset power threshold is at least greater than the minimum output power of the target LLC branch, but this application does not limit the specific value of the preset power threshold.

[0075] Thus, when both the turn-on delay time and the turn-off delay time are greater than or equal to the maximum delay time, it means that it is no longer possible to reduce the output current of the target LLC circuit by extending the turn-on delay time and the turn-off delay time. At this time, the output power of the target LLC branch is directly controlled to be less than or equal to the preset power threshold in order to quickly reduce the branch current of the target LLC branch, thereby improving the safety of the parallel LLC circuit 10.

[0076] In some embodiments, after extending the turn-on delay time and turn-off delay time of the switching transistor in the output side bridge arm circuit of the target LLC branch, the control method further includes: When both the turn-on delay time and the turn-off delay time are equal to the maximum delay time, the switch of the output side bridge arm circuit of the control target LLC branch remains open.

[0077] When both the turn-on delay time and the turn-off delay time are equal to the maximum delay time, it means that it is no longer possible to reduce the output current of the target LLC circuit by extending the turn-on delay time and the turn-off delay time. At this time, the switch of the output side bridge arm circuit of the target LLC branch is kept open, that is, the target LLC branch is stopped working. However, the other LLC branch in the parallel LLC circuit 10 is kept working normally. This is to reduce the risk of burnout of the devices on the target LLC circuit and improve the safety of the parallel LLC circuit 10, while maintaining the energy transfer function of the parallel LLC circuit 10 as much as possible.

[0078] In some embodiments, after the switch of the output-side bridge arm circuit of the controlled LLC branch remains open, the control method further includes: After a preset time, the target LLC branch is controlled to re-participate in power conversion. When the uneven current between the two LLC branches of the parallel LLC circuit 10 is detected, the target LLC branch is re-determined, and the steps of extending the turn-on delay time and turn-off delay time of the output side bridge arm circuit switch on the target LLC branch are executed.

[0079] In this way, the energy conversion efficiency of the parallel LLC circuit 10 can be maximized.

[0080] In some embodiments, before extending the turn-on delay time and turn-off delay time of the switch transistor in the output side bridge arm circuit of the target LLC branch, the control method further includes: When the current is shared between the two LLC branches, the turn-on delay time and turn-off delay time of the switching transistors controlling the output side bridge arm circuit of each LLC branch are both preset delay times.

[0081] Thus, when the two LLC branches of the parallel LLC circuit 10 share the current, the turn-on delay time and turn-off delay time of the switching transistor in the output side bridge arm circuit of each LLC branch are controlled to be preset delay times, so as to reduce the probability of energy flowing back from the output side bridge arm circuit to the input side bridge arm circuit.

[0082] It is understandable that if uneven current is detected in the two LLC branches of the parallel LLC circuit 10, the extended turn-on delay time and turn-off delay time can be obtained based on the preset delay time and the preset adjustment step size.

[0083] Please see Figure 5 , Figure 5 A flowchart illustrating a control method for a parallel LLC circuit provided in an embodiment of this application. Figure 5 The flowchart of the control method for the parallel LLC circuit shown includes the following steps S501-S510.

[0084] Step S501: Obtain the branch current I1 of the first LLC branch and the branch current I2 of the second LLC branch respectively.

[0085] Step S502: Determine whether the absolute value of the current difference obtained by subtracting the branch current I2 of the second LLC branch from the branch current I1 of the first LLC branch is greater than a preset threshold.

[0086] Step S503: If the judgment result of step S502 is negative, the turn-on delay time and turn-off delay time of the switching transistor of the output side bridge arm circuit in each LLC branch are both preset delay times.

[0087] Step S504: If the judgment result of step S502 is yes, determine the LLC branch with the larger branch current among the two LLC branches as the target LLC branch, and extend the turn-on delay time and turn-off delay time of the switch tube on the output side bridge arm circuit of the target LLC branch, and make the turn-on delay time equal to the turn-off delay time.

[0088] Step S505: Determine whether both the activation delay time and the deactivation delay time are greater than or equal to the maximum delay time.

[0089] Step S506: When the judgment result of step S505 is yes, control the output power of the target LLC branch to be less than or equal to the preset power threshold.

[0090] Step S507: If the judgment result of step S507 is negative, determine whether the absolute value of the current difference obtained by subtracting the branch current I2 of the second LLC branch from the branch current I1 of the first LLC branch is less than or equal to a preset threshold.

[0091] Step S508: If the judgment result of step S507 is yes, the turn-on delay time and turn-off delay time of the target LLC branch remain unchanged.

[0092] Step S509: If the judgment result of step S507 is negative, return to step S504.

[0093] Understandably, Figure 5 The flowchart of the control method for the parallel LLC circuit shown does not limit the control method for the parallel LLC circuit provided in this application.

[0094] Please refer to the following: Figure 6 and Figure 7 , Figure 6 In one embodiment of this application, when the two LLC branches in the parallel LLC circuit 10 have uneven current distribution, and the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switching transistors on each LLC branch are consistent, the following is a schematic diagram of the branch current waveforms of the two LLC branches. Curve L601 represents the branch current curve of the first LLC branch 11, and curve L602 represents the branch current curve of the second LLC branch 12. The effective value of the branch current of the first LLC branch 11 is 2.07A, and the effective value of the branch current of the second LLC branch 12 is 4.39A. The current difference between the two branch currents is 2.03A. At this time, the first LLC branch 11 and the second LLC branch 12 have uneven current distribution.

[0095] Figure 7 This diagram illustrates the branch current waveforms of the two LLC branches after extending the turn-on and turn-off delay times of the output-side bridge arm circuit switch on the second LLC branch 12. Curve L701 represents the branch current curve of the first LLC branch 11, and curve L702 represents the branch current curve of the second LLC branch 12. The effective value of the branch current in the first LLC branch 11 is 3.17A, and the effective value of the branch current in the second LLC branch 12 is 3.48A. The current difference between the two branches is reduced to 0.31A, achieving current sharing between the first LLC branch 11 and the second LLC branch 12. Clearly, from... Figure 6 and Figure 7 It can be seen that the control method for the parallel LLC circuit provided in this application has a significant effect on achieving current sharing between the two LLC branches.

[0096] Please see Figure 8One embodiment of this application also provides a power conversion device 100, including a parallel LLC circuit 10 and a controller 101. The parallel LLC circuit includes two LLC branches connected in parallel. Each LLC branch includes an input-side bridge arm circuit 11 and an output-side bridge arm circuit 12. The four switches of the input-side bridge arm circuit 11 correspond one-to-one with the four switches of the output-side bridge arm circuit 12. The controller is used to execute the control method of the parallel LLC circuit as described in any of the above embodiments.

[0097] Please see Figure 9 An embodiment of this application also provides an energy storage device 200, including a power conversion device 100 and an energy storage battery 201. The energy storage battery 201 is connected to the power conversion device 100 to provide DC power to the power conversion device 100 or to store the DC power output by the power conversion device 100.

[0098] Please refer to the following: Figure 8 In some embodiments, the energy storage battery 201 may be connected to the transmission bus of the power conversion device 100, such as the positive transmission bus BAT+ and the negative transmission bus BAT-.

[0099] It is understandable that the energy storage device 200 can be a device with pure energy storage function, or it can be an electronic device with energy storage function, such as an air conditioner, refrigerator, or self-moving device with a battery pack.

[0100] Please see Figure 10 An embodiment of this application also provides a control device 300, including a memory 301 and a controller 101. The memory 301 stores a computer program so that when the controller 101 executes the computer program, it implements the control method for the parallel LLC circuit as described in any of the above embodiments.

[0101] It is understood that the control device 300 can be a standalone electronic device or integrated into the power conversion device 100 or the energy storage device 200. This application does not limit the specific form of the control device 300.

[0102] Please see Figure 11 An embodiment of this application also provides a computer-readable storage medium 400. The computer-readable storage medium 400 stores a computer program 401, which, when executed by a processor, can implement the control method for the parallel LLC circuit as described in any of the above embodiments.

[0103] Computer-readable storage media may be portable compact disc read-only memory (CD-ROM) and include program code, and may 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 that may be used by or in conjunction with an instruction execution system, apparatus, or device.

[0104] It is understood that the controller 101 and processor mentioned in this application may include a microcontroller unit (MCU), a central processing unit (CPU), other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, etc.

[0105] The above-described program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A 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 thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0106] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium, capable of sending, propagating, or transmitting programs for use by or in conjunction with an instruction execution system, apparatus, or device.

[0107] The program code contained on the readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0108] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's device, as a standalone 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 cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0109] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0110] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for a parallel LLC circuit, wherein the parallel LLC circuit comprises at least two LLC branches connected in parallel, each LLC branch comprising an input-side bridge arm circuit and an output-side bridge arm circuit, characterized in that, The control method includes: When the two LLC branches have uneven current distribution, the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch in the target LLC branch are extended, wherein, The target LLC branch is the LLC branch with the larger branch current among the two LLC branches; The turn-on delay time is the duration between the rising edge of the drive signal of any switch in the input-side bridge arm circuit of the target LLC branch and the rising edge of the drive signal of the corresponding switch in the output-side bridge arm circuit. The turn-off delay time is the duration between the falling edge of the drive signal of any switch in the input-side bridge arm circuit of the target LLC branch and the falling edge of the drive signal of the corresponding switch in the output-side bridge arm circuit, and the turn-on delay time is equal to the turn-off delay time.

2. The control method according to claim 1, characterized in that, The turn-on delay time and turn-off delay time of the output side bridge arm circuit switching transistor on the extended target LLC branch include: The turn-on delay time and the turn-off delay time of the output side bridge arm circuit switch on the target LLC branch are extended according to the preset adjustment step size.

3. The control method according to claim 1, characterized in that, After the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch on the extended target LLC branch, the control method further includes: When both the turn-on delay time and the turn-off delay time are greater than or equal to the maximum delay time, and the two LLC branches have uneven current distribution, the output power of the target LLC branch is controlled to be less than or equal to a preset power threshold.

4. The control method according to claim 1, characterized in that, After the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch on the extended target LLC branch, the control method further includes: When both the turn-on delay time and the turn-off delay time are greater than or equal to the maximum delay time, the switching transistor of the output side bridge arm circuit of the target LLC branch is kept off.

5. The control method according to claim 1, characterized in that, Before the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch on the extended target LLC branch, the control method further includes: When the two LLC branches share the current, the turn-on delay time and turn-off delay time of the switching transistor of the output side bridge arm circuit in each LLC branch are both preset delay times.

6. The control method according to claim 1, characterized in that, Before the turn-on delay time and turn-off delay time of the output-side bridge arm circuit switch on the extended target LLC branch, the control method further includes: Obtain the branch current of each of the two LLC branches; When the absolute value of the difference between the currents of the two LLC branches is greater than a preset threshold, it is determined that the two LLC branches are not in equal current distribution. When the absolute value of the difference between the currents of the two LLC branches is less than or equal to a preset threshold, the current sharing of the two LLC branches is determined.

7. The control method according to claim 1, characterized in that, Each LLC branch further includes a resonant cavity, and the input-side bridge arm circuit and the output-side bridge arm circuit are coupled through the resonant cavity. The resonant cavity includes a resonant inductor, a resonant capacitor, and a transformer. The branch current is any one of the input current, output current, and inductance current flowing through the resonant inductor of the LLC circuit.

8. A power conversion device, the power conversion device comprising a parallel LLC circuit and a controller, characterized in that, The parallel LLC circuit includes at least two LLC branches connected in parallel, each LLC branch including an input-side bridge arm circuit and an output-side bridge arm circuit, and the controller is used to execute the control method of the parallel LLC circuit as described in any one of claims 1 to 7.

9. An energy storage device, characterized in that, The energy storage device includes an energy storage battery and a power conversion device as described in claim 8, wherein the energy storage battery is connected to the power conversion device to provide DC power to the power conversion device or to store the DC power output by the power conversion device.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the control method for the parallel LLC circuit as described in any one of claims 1-7.

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