Control method and device of direct current conversion device, storage medium and energy storage system

Abstract

The invention provides a control method and device of a direct current conversion device, a storage medium and an energy storage system, and relates to the technical field of power electronics. The direct-current conversion device comprises a primary side H-bridge circuit and a secondary side H-bridge circuit, and the control method of the direct-current conversion device comprises the following steps: determining first switching frequencies of the primary side H-bridge circuit and the secondary side H-bridge circuit according to an output voltage of the secondary side H-bridge circuit; according to the first switching frequency and the switching frequency range, a second switching frequency, a first duty ratio and a second duty ratio are determined, the first duty ratio is the duty ratio of an upper half bridge arm in the primary side H-bridge circuit, and the second duty ratio is the duty ratio of an upper half bridge arm in the secondary side H-bridge circuit; and controlling the primary side H-bridge circuit and the secondary side H-bridge circuit according to the second switching frequency, the first duty ratio and the second duty ratio. On the premise that a wide soft switching range is guaranteed, the gain adjusting range is widened, and the current sharing capacity and the SOC balancing capacity of the direct current conversion device are improved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a control method, device, storage medium and energy storage system for a direct current conversion device. Background Art

[0002] In order to increase the capacity of the energy storage system, multiple battery clusters are usually connected in parallel. Due to differences in the factory and operating temperature of the batteries, if multiple battery clusters are directly connected in parallel, problems such as inter-cluster circulation and SOC (State Of Charge) imbalance will occur, affecting the charging and discharging capacity of the entire energy storage system.

[0003] In the related art, by adding a bidirectional DCDC (direct current-to-direct current) converter between battery clusters and then connecting them in parallel, the DCDC converter can adjust the charge and discharge current of each battery. The resonant converter has a high boost ratio and can achieve a wider soft switching range, thereby obtaining a higher conversion efficiency. However, the resonant converter usually adopts variable frequency control, and the gain adjustment range is limited, resulting in a low current sharing capability or SOC balancing capability of the converter. Summary of the invention

[0004] The present application aims to solve the technical problem of low current sharing capability or SOC balancing capability of the resonant converter existing in the prior art or related art.

[0005] To this end, a first aspect of the present application proposes a control method for a DC conversion device.

[0006] A second aspect of the present application provides a control device for a DC conversion device.

[0007] A third aspect of the present application provides a control device for a DC conversion device.

[0008] A fourth aspect of the present application provides a readable storage medium.

[0009] A fifth aspect of the present application proposes an energy storage system.

[0010] In view of this, according to a first aspect of the present application, a control method for a DC converter is proposed. The DC converter includes a primary H-bridge circuit and a secondary H-bridge circuit. The control method for the DC converter includes:

[0011] Determining a first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit according to the output voltage of the secondary H-bridge circuit;

[0012] Determine the second switching frequency, the first duty cycle and the second duty cycle according to the first switching frequency and the switching frequency range, wherein the first duty cycle is the duty cycle of the upper half bridge arm in the primary side H-bridge circuit, and the second duty cycle is the duty cycle of the upper half bridge arm in the secondary side H-bridge circuit;

[0013] The primary side H-bridge circuit and the secondary side H-bridge circuit are controlled according to the second switching frequency, the first duty cycle and the second duty cycle.

[0014] In this technical solution, frequency conversion control is first performed during the control of the DC converter. Specifically, the first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit is determined according to the output voltage of the secondary H-bridge circuit.

[0015] Specifically, the DC conversion device is controlled by synchronous equal-width frequency conversion.

[0016] In this technical solution, the first duty cycle is the duty cycle of the switch in the upper half arm of the primary H-bridge circuit, and the duty cycle of the switch in the lower half arm of the primary H-bridge circuit is complementary to the first duty cycle, and the second duty cycle is the duty cycle of the switch in the upper half arm of the secondary H-bridge circuit, and the duty cycle of the switch in the lower half arm of the secondary H-bridge circuit is complementary to the second duty cycle.

[0017] In this technical solution, the switching frequency range is a range between the minimum switching frequency and the maximum switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit. By comparing the first switching frequency with the switching frequency range, the second switching frequency is obtained, and the first duty cycle of the upper half bridge arm of the primary H-bridge circuit and the second duty cycle of the lower half bridge arm of the secondary H-bridge circuit are determined.

[0018] In this technical solution, switches in the primary H-bridge circuit and the secondary H-bridge circuit are controlled based on the first duty cycle, the second duty cycle and the second switching frequency. It should be noted that the duty cycle of the lower half bridge arm in the primary H-bridge circuit is the third duty cycle, which is complementary to the first duty cycle. The duty cycle of the lower half bridge arm in the secondary H-bridge circuit is the fourth duty cycle, which is complementary to the second duty cycle.

[0019] Specifically, it is determined whether the first switching frequency exceeds the switching frequency range during the control of the DC converter by synchronous equal-width frequency conversion. If the first switching frequency exceeds the switching frequency range, a center-symmetrical PWM (Pulse Width Modulation) method is used for adjustment.

[0020] In the technical solution of the present application, synchronous equal-width frequency conversion control of the DC conversion device is highly efficient and soft switching is easy to achieve, thereby enabling seamless switching of battery charging and discharging. The center-symmetrical PWM control gain range is relatively wide, and the gain is independent of power and only related to the duty cycle. The present application combines synchronous equal-width frequency conversion control with center-symmetrical PWM control. In the initial stage, synchronous equal-width frequency conversion control is first performed. When the first switching frequency obtained by the synchronous equal-width frequency conversion control exceeds the switching frequency range, center-symmetrical PWM control is performed. While ensuring a wider soft switching range, the gain adjustment range is improved, thereby improving the current sharing capability and SOC balancing capability of the DC conversion device.

[0021] In some technical schemes, optionally, the second switching frequency, the first duty cycle and the second duty cycle are determined based on the first switching frequency and the switching frequency range, including: comparing the first switching frequency with the maximum frequency and the minimum frequency in the switching frequency range; determining the second switching frequency based on the comparison result; and determining the first duty cycle and the second duty cycle based on the comparison result and the first switching frequency.

[0022] In this technical solution, when the first switching frequency is obtained by synchronous equal-width frequency conversion control, the first switching frequency is compared with the maximum frequency and the minimum frequency in the switching frequency range to obtain a comparison result. The comparison result includes that the first switching frequency is within the switching frequency range, the first switching frequency is greater than the maximum frequency, and the first switching frequency is less than the minimum frequency. When the first switching frequency is within the switching frequency range, it is determined that the first switching frequency does not exceed the range. At this time, the control is continued in the manner of synchronous equal-width frequency conversion. When the first switching frequency is greater than or equal to the maximum frequency or the first switching frequency is less than or equal to the minimum frequency, it is determined that the first switching frequency exceeds the range. At this time, it is necessary to determine the second switching frequency based on the switching frequency range, and determine the first duty cycle and the second duty cycle. The DC conversion device is subjected to central symmetrical PWM control based on the second switching frequency, the first duty cycle and the second duty cycle.

[0023] In the technical solution of the present application, by comparing and judging whether the first switching frequency is within the switching frequency range, and determining the second switching frequency, the first duty cycle, and the second duty cycle based on the comparison result, a segmented method of synchronous equal-width frequency conversion control and center-symmetrical PWM control is implemented, thereby further ensuring a wider soft switching range while improving the gain adjustment range.

[0024] In some technical solutions, optionally, determining the second switching frequency according to the comparison result includes:

[0025] When the first switching frequency is less than or equal to the maximum frequency value and greater than or equal to the minimum frequency value, determining the first switching frequency as the second switching frequency;

[0026] When the first switching frequency is greater than the maximum frequency, the maximum frequency is determined as the second switching frequency;

[0027] When the first switching frequency is less than the minimum frequency value, the minimum frequency value is determined as the second switching frequency.

[0028] In this technical solution, when the first switching frequency is within the switching frequency range, it is determined that the first switching frequency does not exceed the switching frequency range, that is, it does not exceed the range of synchronous equal-width frequency conversion regulation. At this time, the first switching frequency is used as the second switching frequency to modulate the signal and control the DC conversion device.

[0029] When the first switching frequency is greater than the maximum frequency, it is determined that the first switching frequency has exceeded the switching frequency range, that is, the first switching frequency exceeds the range of synchronous equal-width frequency conversion regulation. At this time, the maximum frequency is determined as the second switching frequency to prevent the second switching frequency from exceeding the range of synchronous equal-width frequency conversion regulation.

[0030] When the first switching frequency is less than the minimum frequency value, it is determined that the first switching frequency has exceeded the switching frequency range, that is, the first switching frequency exceeds the range of synchronous equal-width frequency conversion regulation. At this time, the minimum frequency value is determined as the second switching frequency to prevent the second switching frequency from exceeding the range of synchronous equal-width frequency conversion regulation.

[0031] In the technical solution of the present application, in the process of controlling the DC conversion device, after the first switching frequency is determined by synchronous equal-width frequency conversion control, when the first switching frequency is within the switching frequency range, the first switching frequency is determined as the second switching frequency to control the DC conversion device; when the first switching frequency is greater than the maximum frequency of the switching frequency range, the maximum frequency is used as the second switching frequency to control the DC conversion device; when the first switching frequency is less than the minimum frequency of the switching frequency range, the minimum frequency is used as the second switching frequency to control the DC conversion device, thereby avoiding the second switching frequency from exceeding the range of synchronous equal-width frequency conversion regulation, making it easy for the DC conversion device to achieve soft switching, and enabling seamless switching of battery charging and discharging.

[0032] In some technical solutions, optionally, determining the first duty cycle and the second duty cycle according to the comparison result and the first switching frequency includes:

[0033] When the first switching frequency is less than or equal to the maximum frequency and greater than or equal to the minimum frequency, both the first duty cycle and the second duty cycle are determined as preset duty cycles;

[0034] When the first switching frequency is greater than the maximum frequency, the first duty cycle is determined as the preset duty cycle, and the second duty cycle is determined based on the preset duty cycle, the maximum frequency and the first switching frequency;

[0035] When the first switching frequency is less than the minimum frequency value, the second duty cycle is determined as the preset duty cycle, and the first duty cycle is determined based on the preset duty cycle, the minimum frequency value and the first switching frequency.

[0036] In this technical solution, when the first switching frequency is within the switching frequency range, it is determined that the first switching frequency does not exceed the range of synchronous equal-width frequency conversion regulation. At this time, there is no need to enter the center-symmetrical PWM control, and the first duty cycle and the second duty cycle are both determined as the preset duty cycles.

[0037] In this technical solution, when the first switching frequency is outside the switching frequency range, it is necessary to determine the corresponding first duty cycle and second duty cycle based on the preset duty cycle according to the numerical relationship between the first switching frequency and the switching frequency range.

[0038] Specifically, the first switching frequency is greater than the maximum frequency in the switching frequency range. At this time, the DC conversion device is in a boost state, and there is no need to adjust the first duty cycle of the upper half bridge arm in the primary H-bridge circuit, so the first duty cycle can be determined as the preset duty cycle, and the second duty cycle of the upper half bridge arm in the secondary H-bridge circuit needs to be reduced, and the specific value of the reduction is calculated based on the first switching frequency and the maximum frequency. The first switching frequency is less than the minimum frequency in the switching frequency range. At this time, the DC conversion device is in a step-down state, and there is no need to adjust the second duty cycle of the upper half bridge arm in the secondary H-bridge circuit, so the second duty cycle can be determined as the preset duty cycle, and the first duty cycle of the upper half bridge arm in the primary H-bridge circuit needs to be reduced, and the specific value of the reduction is calculated based on the first switching frequency and the minimum frequency.

[0039] In the technical solution of the present application, after the first switching frequency is determined by synchronous equal-width frequency conversion control, when the first switching frequency is within the switching frequency range, the first switching frequency is determined as the second switching frequency to control the DC conversion device, and the first duty cycle and the second duty cycle are both determined as preset duty cycles. When the first switching frequency is greater than the maximum frequency of the switching frequency range, the preset duty cycle is adjusted according to the maximum frequency and the first switching frequency to obtain the second duty cycle. When the first switching frequency is less than the minimum frequency of the switching frequency range, the preset duty cycle is adjusted according to the minimum frequency and the first switching frequency to obtain the first duty cycle. This realizes the control of centrally symmetrical PWM when the first switching frequency exceeds the switching frequency range, thereby improving the adjustment range.

[0040] In some technical solutions, optionally, the second duty cycle is determined based on a preset duty cycle, a maximum frequency and a first switching frequency, including: determining a first frequency difference between the first switching frequency and the maximum frequency; and determining the second duty cycle based on the first frequency difference, the preset duty cycle and a proportional coefficient.

[0041] In this technical solution, when the first switching frequency is greater than the maximum frequency, the difference between the first switching frequency and the maximum frequency is calculated to obtain a first frequency difference. Based on the first frequency difference, the preset duty cycle is reduced to obtain a second duty cycle, that is, the difference between the preset duty cycle and the product of the first frequency difference and the proportional coefficient is used as the second duty cycle.

[0042] It should be noted that when the first switching frequency is greater than the maximum frequency, the preset duty cycle is used as the first duty cycle.

[0043] In the technical solution of the present application, a first frequency difference is obtained by calculating the difference between the first switching frequency and the maximum frequency, and a second duty cycle is obtained by adjusting the preset duty cycle based on the calculated first frequency difference, thereby improving the accuracy of controlling the DC conversion device based on the second duty cycle, the maximum frequency and the preset duty cycle as the first duty cycle.

[0044] In some technical schemes, optionally, the first duty cycle is determined based on a preset duty cycle, a minimum frequency value and a first switching frequency, including: determining a second frequency difference between the minimum frequency value and the first switching frequency; and determining the first duty cycle according to the second frequency difference, the preset duty cycle and the proportional coefficient.

[0045] In this technical solution, when the first switching frequency is less than the minimum frequency value, the difference between the minimum frequency value and the first switching frequency is calculated to obtain a second frequency difference value. Based on the second frequency difference value, the preset duty cycle is reduced to obtain the first duty cycle, that is, the difference between the preset duty cycle and the product of the second frequency difference value and the proportional coefficient is used as the first duty cycle.

[0046] It should be noted that when the first switching frequency is less than the minimum frequency, the preset duty cycle is used as the second duty cycle.

[0047] In the technical solution of the present application, a second frequency difference is obtained by calculating the difference between the minimum frequency and the first switching frequency, and the preset duty cycle is adjusted based on the calculated second frequency difference to obtain the first duty cycle, thereby improving the accuracy of controlling the DC conversion device based on the first duty cycle, the maximum frequency and the preset duty cycle as the second duty cycle.

[0048] In some technical schemes, optionally, the DC conversion device includes a resonant cavity, which is arranged between the primary H-bridge circuit and the secondary H-bridge circuit; according to the output voltage of the secondary H-bridge circuit, the first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit is determined, including: proportionally integrating the voltage difference between the output voltage and the reference voltage to obtain a proportional integration result; and determining the first switching frequency according to the resonant frequency and the proportional integration result.

[0049] In the technical solution of the present application, in the process of determining the first switching frequency by synchronous equal-width frequency conversion, the difference signal between the output voltage signal of the secondary side H-bridge circuit and the reference voltage signal is proportionally integrated to obtain a proportional integration result, thereby determining the first switching frequency according to the proportional integration result and the resonant frequency. By controlling the output voltage of the secondary side H-bridge circuit, the first switching frequency of the synchronous equal-width frequency conversion control stage can be determined.

[0050] In some technical solutions, optionally, the DC conversion device includes a resonant cavity, which is arranged between the primary H-bridge circuit and the secondary H-bridge circuit; the resonant cavity includes at least one of the following: LLC resonant cavity, L-LLC resonant cavity, CLLC resonant cavity.

[0051] In the technical solution of the present application, a resonant cavity is also provided in the DC conversion device. The resonant cavity is arranged between the primary H-bridge circuit and the secondary H-bridge circuit. The resonant cavity can be selected as an LLC resonant cavity, an L-LLC resonant cavity, or a CLLC resonant cavity.

[0052] According to a second aspect of the present application, a control device for a DC converter is provided. The DC converter includes a primary H-bridge circuit and a secondary H-bridge circuit. The control device for the DC converter includes:

[0053] A determination module, used to determine a first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit according to the output voltage of the secondary H-bridge circuit;

[0054] A determination module, configured to determine a second switching frequency, a first duty cycle, and a second duty cycle according to the first switching frequency and the switching frequency range, wherein the first duty cycle is the duty cycle of the upper half bridge arm in the primary H-bridge circuit, and the second duty cycle is the duty cycle of the upper half bridge arm in the secondary H-bridge circuit;

[0055] The control module is used to control the primary side H-bridge circuit and the secondary side H-bridge circuit according to the second switching frequency, the first duty cycle and the second duty cycle.

[0056] In the embodiment of the present application, synchronous equal-width frequency conversion control of the DC conversion device is highly efficient and soft switching is easy to achieve, thereby enabling seamless switching of battery charging and discharging. The center-symmetrical PWM control gain range is relatively wide, and the gain is independent of power and only related to the duty cycle. The present application combines synchronous equal-width frequency conversion control with center-symmetrical PWM control. In the initial stage, synchronous equal-width frequency conversion control is first performed. When the first switching frequency obtained by the synchronous equal-width frequency conversion control exceeds the switching frequency range, center-symmetrical PWM control is performed. While ensuring a relatively wide soft switching range, the gain adjustment range is improved, thereby improving the current sharing capability and SOC balancing capability of the DC conversion device.

[0057] According to the third aspect of the present application, a control device for a DC converter is proposed, the control device for the DC converter comprises a processor and a memory, the memory stores a program or instruction, and when the program or instruction is executed by the processor, the steps of the control method for the DC converter in any of the above technical solutions are implemented. Therefore, the control device for the DC converter has all the beneficial effects of the control method for the DC converter in any of the above technical solutions, which will not be described in detail here.

[0058] According to the fourth aspect of the present application, a readable storage medium is proposed, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the control method of the DC conversion device in any of the above-mentioned technical solutions are implemented, thereby having all the beneficial technical effects of the control method of the DC conversion device in any of the above-mentioned technical solutions.

[0059] According to the fifth aspect of the present application, an energy storage system is proposed, comprising: at least two battery clusters, a DC conversion device is arranged between at least two battery clusters; such as the control device of the DC conversion device in any of the above technical solutions, and / or the readable storage medium in any of the above technical solutions, and thus has all the beneficial technical effects of the control device of the DC conversion device in any of the above technical solutions, and / or the readable storage medium in any of the above technical solutions, and no further details will be given here.

[0060] Additional aspects and advantages of the present application will become apparent in the following description or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0062] Figure 1 One of the flow charts of a control method of a DC conversion device provided in some embodiments of the present application is shown;

[0063] Figure 2One of the circuit topology diagrams of a DC conversion device provided in some embodiments of the present application is shown;

[0064] Figure 3 shows a steady-state waveform diagram of a DC conversion device in an under-resonance state in some embodiments of the present application;

[0065] Figure 4 shows a steady-state waveform diagram of a DC conversion device in a resonant state in some embodiments of the present application;

[0066] Figure 5 shows a steady-state waveform diagram of a DC conversion device in a super-resonant state in some embodiments of the present application;

[0067] Figure 6 The voltage gain characteristic curves of the DC conversion device under different quality factors in some embodiments of the present application are shown;

[0068] Figure 7 One of the voltage waveform diagrams of the DC conversion device in the boost stage in some embodiments of the present application is shown;

[0069] Figure 8 The second voltage waveform diagram of the DC conversion device in the step-down stage in some embodiments of the present application is shown;

[0070] Fig. 9 The voltage gain curves of the DC conversion device in the boost state and the buck state in some embodiments of the present application are shown;

[0071] Fig.10 A control loop schematic diagram in some embodiments of the present application is shown;

[0072] Fig.11 A second circuit topology diagram of a DC conversion device provided in some embodiments of the present application is shown;

[0073] Fig.12 A third circuit topology diagram of a DC conversion device provided in some embodiments of the present application is shown;

[0074] Fig.13 A second flow chart of a control method for a DC conversion device provided in some embodiments of the present application is shown;

[0075] Fig.14 One of the output voltage simulation waveform diagrams of the secondary side H-bridge circuit provided in some embodiments of the present application is shown;

[0076] Fig.15 The second output voltage simulation waveform diagram of the secondary side H-bridge circuit provided in some embodiments of the present application is shown;

[0077] Fig.16 The third output voltage simulation waveform diagram of the secondary side H-bridge circuit provided in some embodiments of the present application is shown;

[0078] Fig.17 One of the structural block diagrams of a control device for a DC conversion device is shown in some embodiments of the present application;

[0079] Fig.18 A second structural block diagram of a control device for a DC conversion device is shown in some embodiments of the present application;

[0080] Fig.19 A structural block diagram of an energy storage system provided in some embodiments of the present application is shown.

[0081] The reference numerals are as follows:

[0082] 200 DC conversion device, 202 primary side H-bridge circuit, 204 secondary side H-bridge circuit, 206 resonant cavity, S1 first switch, S2 second switch, S3 third switch, S4 fourth switch, S5 fifth switch, S6 sixth switch, S7 seventh switch, S8 eighth switch, L r Resonant inductor, C r Resonant capacitor, C 1 The filter capacitor on the low voltage side, C 2 The filter capacitor on the high voltage side, L m1 Additional inductance, L m2 The magnetizing inductance of the transformer, T transformer. DETAILED DESCRIPTION

[0083] In order to more clearly understand the above-mentioned objectives, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, in the absence of conflict, the present embodiment and the features in the embodiment can be combined with each other.

[0084] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0085] Refer to the following Figures 1 to 19 A control method for a DC converter device, a control device for a DC converter device, a readable storage medium, and an energy storage system according to some embodiments of the present application are described.

[0086] According to one embodiment of the present application, Figure 1 One of the flow charts of a control method of a DC conversion device provided in some embodiments of the present application is shown, Figure 2One of the circuit topology diagrams of a DC conversion device provided in some embodiments of the present application is shown, such as Figure 1 and Figure 2 As shown, a control method for a DC converter is proposed. The DC converter includes a primary H-bridge circuit and a secondary H-bridge circuit. The control method for the DC converter includes:

[0087] Step 102, determining a first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit according to the output voltage of the secondary H-bridge circuit;

[0088] In this embodiment, the primary H-bridge circuit 202 includes two parallel primary bridge arms, one of which is provided with a first switch S1 and a second switch S2 connected in series, and the other primary bridge arm is provided with a third switch S3 and a fourth switch S4 connected in series. The secondary H-bridge circuit 204 includes two parallel secondary bridge arms, one of which is provided with a fifth switch S5 and a sixth switch S6 connected in series, and the other secondary bridge arm is provided with a seventh switch S7 and an eighth switch S8 connected in series. A resonant cavity 206 is provided between the primary H-bridge circuit 202 and the secondary H-bridge circuit 204.

[0089] In this embodiment, in the process of controlling the DC conversion device, frequency conversion control is first performed. Specifically, the first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit is determined according to the output voltage of the secondary H-bridge circuit.

[0090] Specifically, during the execution of step 102, the DC conversion device is controlled by synchronous equal-width frequency conversion.

[0091] Step 104, determining a second switching frequency, a first duty cycle, and a second duty cycle according to the first switching frequency and the switching frequency range;

[0092] The first duty cycle is the duty cycle of the upper half bridge arm in the primary H-bridge circuit, and the second duty cycle is the duty cycle of the upper half bridge arm in the secondary H-bridge circuit;

[0093] In this embodiment, the first duty cycle is the duty cycle of the switch in the upper half arm of the primary H-bridge circuit, and the duty cycle of the switch in the lower half arm of the primary H-bridge circuit is complementary to the first duty cycle, and the second duty cycle is the duty cycle of the switch in the upper half arm of the secondary H-bridge circuit, and the duty cycle of the switch in the lower half arm of the secondary H-bridge circuit is complementary to the second duty cycle.

[0094] like Figure 2 As shown, exemplarily, the first target switches are the first switch S1 and the second switch S2, and the second target switches are the fifth switch S5 and the seventh switch S7.

[0095] In this embodiment, the switching frequency range is a range between the minimum switching frequency and the maximum switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit. The second switching frequency is obtained by comparing the first switching frequency with the switching frequency range, and the first duty cycle of the upper half bridge arm of the primary H-bridge circuit and the second duty cycle of the lower half bridge arm of the secondary H-bridge circuit are determined.

[0096] Step 106: Control the primary H-bridge circuit and the secondary H-bridge circuit according to the second switching frequency, the first duty cycle, and the second duty cycle.

[0097] In this embodiment, switches in the primary H-bridge circuit and the secondary H-bridge circuit are controlled based on the first duty cycle, the second duty cycle, and the second switching frequency. It should be noted that the duty cycle of the lower half bridge arm in the primary H-bridge circuit is the third duty cycle, which is complementary to the first duty cycle. The duty cycle of the lower half bridge arm in the secondary H-bridge circuit is the fourth duty cycle, which is complementary to the second duty cycle.

[0098] Specifically, step 104 can determine whether the first switching frequency exceeds the switching frequency range during the control of the DC converter by synchronous equal-width frequency conversion. If the first switching frequency exceeds the switching frequency range, the center-symmetrical PWM is used for adjustment.

[0099] like Figure 2 As shown, the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 are the switch tubes of the primary side H bridge circuit, the fifth switch S5, the sixth switch S6, the seventh switch S7 and the eighth switch S8 are the switch tubes of the secondary side H bridge circuit, and the transformation ratio of the transformer T is 1:n. The voltage between the midpoints of the bridge arms of the primary side H bridge circuit is V AB , the voltage between the midpoints of the bridge arms of the secondary H-bridge circuit is V CD Among them, L m1 is the additional inductance, L m2 is the transformer's magnetizing inductance, and L m1 =L m2 .L r is the resonant inductor, C r is the resonant capacitor, C 1 is the filter capacitor on the low voltage side, C 2 is the filter capacitor on the high voltage side. The resonant frequency of the DC converter 200 is f r , the expression (1) of the resonant frequency is as follows:

[0100]

[0101] Among them, f r is the resonant frequency, L r is the resonant inductor, C r is the resonant capacitor.

[0102] The expression (2) of the voltage gain M of the DC converter controlled by synchronous equal-width frequency conversion is as follows:

[0103]

[0104] Where M is the voltage gain, f n is the normalized switching frequency, m is the ratio of the magnetizing inductance to the resonant inductance, and m = L m / L c , L m is the magnetizing inductance, L c is the resonant inductor and Q is the quality factor.

[0105] Exemplarily, the quality factor expression (3) is as follows:

[0106]

[0107] Among them, Q is the quality factor, n is the transformer ratio, Zr is the characteristic impedance, R o For resistance.

[0108] Exemplarily, the expression (4) of characteristic impedance is as follows:

[0109]

[0110] Where Zr is the characteristic impedance, L r is the resonant inductor, C r is the resonant capacitor.

[0111] Figure 3 shows a steady-state waveform diagram of a DC converter in a sub-resonant state in some embodiments of the present application, Figure 4 shows a steady-state waveform diagram of a DC converter in a resonant state in some embodiments of the present application, Figure 5 shows a steady-state waveform diagram of a DC conversion device in a super-resonant state in some embodiments of the present application, Figure 6 The voltage gain characteristic curves of the DC converter under different quality factors in some embodiments of the present application are shown, such as Figures 3 to 6 As shown in the figure, when the DC converter is controlled only by synchronous equal-width frequency conversion, the following problems exist: if the frequency is too small, it may enter the capacitive region, resulting in the loss of ZVS (Zero Voltage Switch). If the frequency is too large, the switching loss will increase. It can be seen that the frequency adjustment range is limited, and thus the gain adjustment range is also limited. Among them, t0, t1, t2, t3, t4, t5, and t6 are all moments, and VAB is Figure 2 The voltage value between points AB, VCD is Figure 2The voltage value of point CD, im1 and ir are Figure 2 The current value of the current signal is shown in FIG.

[0112] When the DC converter is subjected to central symmetric PWM control, D P is the first duty cycle of the switch tube in the upper half of the primary H-bridge circuit, and the duty cycle of the switch tube in the lower half of the primary H-bridge circuit is complementary to the first duty cycle. S It is the second duty cycle of the switch tube in the upper half arm of the secondary H-bridge circuit, and the duty cycle of the switch tube in the lower half arm of the secondary H-bridge circuit is complementary to the second duty cycle.

[0113] Figure 7 FIG. 1 shows one of the voltage waveform diagrams of the DC conversion device in the boost stage in some embodiments of the present application, such as Figure 7 As shown, in the boost state, D P =0.5, D S <0.5. Where V GS is voltage, VAB is Figure 2 The voltage value between points AB, VCD is Figure 2 The voltage values ​​at point CD are as follows: t0, t1, t2, t3, t4, t5, and t6 are all moments.

[0114] The DC converter is controlled by means of central symmetric PWM, and the expression (5) of the voltage gain M in the boost stage is as follows:

[0115]

[0116] Where M is the voltage gain, V H is the input voltage of the primary H-bridge circuit, V L is the output voltage of the secondary side H-bridge circuit, D S is the second duty cycle of the switch tube in the upper half bridge arm of the secondary side H-bridge circuit, and n is the transformation ratio of the transformer.

[0117] Figure 8 FIG. 2 shows a voltage waveform diagram of a DC converter in a voltage reduction stage in some embodiments of the present application. Figure 8 As shown, in the step-down state, D P <0.5, D S =0.5, where V GS is voltage, VAB is Figure 2 The voltage value between points AB, VCD is Figure 2 The voltage values ​​at point CD are as follows: t0, t1, t2, t3, t4, t5, and t6 are all moments.

[0118] The DC converter is controlled by means of central symmetric PWM, and the expression (6) of the voltage gain M in the boost stage is as follows:

[0119]

[0120] Where M is the voltage gain, V H is the input voltage of the primary H-bridge circuit, V L is the output voltage of the secondary side H-bridge circuit, D P is the first duty cycle of the switch tube in the upper half bridge arm of the primary H-bridge circuit, and n is the transformation ratio of the transformer.

[0121] Fig. 9 The voltage gain curves of the DC conversion device in the boost state and the buck state in some embodiments of the present application are shown.

[0122] In the embodiment of the present application, synchronous equal-width frequency conversion control of the DC conversion device is highly efficient and soft switching is easy to achieve, thereby enabling seamless switching of battery charging and discharging. The center-symmetrical PWM control gain range is relatively wide, and the gain is independent of power and only related to the duty cycle. The present application combines synchronous equal-width frequency conversion control with center-symmetrical PWM control. In the initial stage, synchronous equal-width frequency conversion control is first performed. When the first switching frequency obtained by the synchronous equal-width frequency conversion control exceeds the switching frequency range, center-symmetrical PWM control is performed. While ensuring a relatively wide soft switching range, the gain adjustment range is improved, thereby improving the current sharing capability and SOC balancing capability of the DC conversion device.

[0123] In some embodiments, optionally, the second switching frequency, the first duty cycle, and the second duty cycle are determined based on the first switching frequency and the switching frequency range, including: comparing the first switching frequency with the maximum frequency and the minimum frequency in the switching frequency range; determining the second switching frequency based on the comparison result; and determining the first duty cycle and the second duty cycle based on the comparison result and the first switching frequency.

[0124] In this embodiment, when the first switching frequency is obtained by synchronous equal-width frequency conversion control, the first switching frequency is compared with the maximum frequency and the minimum frequency in the switching frequency range to obtain a comparison result. The comparison result includes that the first switching frequency is within the switching frequency range, the first switching frequency is greater than or equal to the maximum frequency, and the first switching frequency is less than or equal to the minimum frequency. When the first switching frequency is within the switching frequency range, it is determined that the first switching frequency does not exceed the range. At this time, the control is continued in the manner of synchronous equal-width frequency conversion. When the first switching frequency is greater than or equal to the maximum frequency or the first switching frequency is less than or equal to the minimum frequency, it is determined that the first switching frequency exceeds the range. At this time, it is necessary to determine the second switching frequency based on the switching frequency range, and determine the first duty cycle and the second duty cycle. The DC conversion device is subjected to central symmetrical PWM control based on the second switching frequency, the first duty cycle and the second duty cycle.

[0125] In the embodiment of the present application, by comparing and judging whether the first switching frequency is within the switching frequency range, and determining the second switching frequency, the first duty cycle, and the second duty cycle based on the comparison result, a segmented method of synchronous equal-width frequency conversion control and center-symmetrical PWM control is implemented, thereby further ensuring a wider soft switching range while improving the gain adjustment range.

[0126] In some embodiments, optionally, determining the second switching frequency according to the comparison result includes:

[0127] When the first switching frequency is less than or equal to the maximum frequency value and greater than or equal to the minimum frequency value, determining the first switching frequency as the second switching frequency;

[0128] When the first switching frequency is greater than the maximum frequency, the maximum frequency is determined as the second switching frequency;

[0129] When the first switching frequency is less than the minimum frequency value, the minimum frequency value is determined as the second switching frequency.

[0130] In this embodiment, when the first switching frequency is within the switching frequency range, it is determined that the first switching frequency does not exceed the switching frequency range, that is, it does not exceed the range of synchronous equal-width frequency conversion regulation. At this time, the first switching frequency is used as the second switching frequency to modulate the signal and control the DC conversion device.

[0131] When the first switching frequency is greater than the maximum frequency, it is determined that the first switching frequency has exceeded the switching frequency range, that is, the first switching frequency exceeds the range of synchronous equal-width frequency conversion regulation. At this time, the maximum frequency is determined as the second switching frequency to prevent the second switching frequency from exceeding the range of synchronous equal-width frequency conversion regulation.

[0132] When the first switching frequency is less than the minimum frequency value, it is determined that the first switching frequency has exceeded the switching frequency range, that is, the first switching frequency exceeds the range of synchronous equal-width frequency conversion regulation. At this time, the minimum frequency value is determined as the second switching frequency to prevent the second switching frequency from exceeding the range of synchronous equal-width frequency conversion regulation.

[0133] In an embodiment of the present application, in the process of controlling a DC conversion device, after determining the first switching frequency by means of synchronous equal-width frequency conversion control, when the first switching frequency is within the switching frequency range, the first switching frequency is determined as the second switching frequency to control the DC conversion device; when the first switching frequency is greater than the maximum frequency value of the switching frequency range, the maximum frequency value is used as the second switching frequency to control the DC conversion device; when the first switching frequency is less than the minimum frequency value of the switching frequency range, the minimum frequency value is used as the second switching frequency to control the DC conversion device, thereby avoiding the second switching frequency from exceeding the range of synchronous equal-width frequency conversion regulation, making it easy for the DC conversion device to achieve soft switching, and enabling seamless switching of battery charging and discharging.

[0134] In some embodiments, optionally, determining the first duty cycle and the second duty cycle according to the comparison result and the first switching frequency includes:

[0135] When the first switching frequency is less than or equal to the maximum frequency and greater than or equal to the minimum frequency, both the first duty cycle and the second duty cycle are determined as preset duty cycles;

[0136] When the first switching frequency is greater than the maximum frequency, the first duty cycle is determined as the preset duty cycle, and the second duty cycle is determined based on the preset duty cycle, the maximum frequency and the first switching frequency;

[0137] When the first switching frequency is less than the minimum frequency value, the second duty cycle is determined as the preset duty cycle, and the first duty cycle is determined based on the preset duty cycle, the minimum frequency value and the first switching frequency.

[0138] In this embodiment, when the first switching frequency is within the switching frequency range, it is determined that the first switching frequency does not exceed the range of synchronous equal-width frequency conversion regulation. At this time, there is no need to enter the centrally symmetrical PWM control, and the first duty cycle and the second duty cycle are both determined as the preset duty cycles.

[0139] Exemplarily, the preset duty cycle is 0.5.

[0140] In this embodiment, when the first switching frequency is outside the switching frequency range, it is necessary to determine the corresponding first duty cycle and second duty cycle based on the preset duty cycle according to the numerical relationship between the first switching frequency and the switching frequency range.

[0141] Specifically, the first switching frequency is greater than the maximum frequency in the switching frequency range. At this time, the DC conversion device is in a boost state, and there is no need to adjust the first duty cycle of the upper half bridge arm in the primary H-bridge circuit, so the first duty cycle can be determined as the preset duty cycle, and the second duty cycle of the upper half bridge arm in the secondary H-bridge circuit needs to be reduced, and the specific value of the reduction is calculated based on the first switching frequency and the maximum frequency. The first switching frequency is less than the minimum frequency in the switching frequency range. At this time, the DC conversion device is in a step-down state, and there is no need to adjust the second duty cycle of the upper half bridge arm in the secondary H-bridge circuit, so the second duty cycle can be determined as the preset duty cycle, and the first duty cycle of the upper half bridge arm in the primary H-bridge circuit needs to be reduced, and the specific value of the reduction is calculated based on the first switching frequency and the minimum frequency.

[0142] In an embodiment of the present application, after the first switching frequency is determined by synchronous equal-width frequency conversion control, when the first switching frequency is within the switching frequency range, the first switching frequency is determined as the second switching frequency to control the DC conversion device, and the first duty cycle and the second duty cycle are both determined as preset duty cycles. When the first switching frequency is greater than the maximum frequency of the switching frequency range, the preset duty cycle is adjusted according to the maximum frequency and the first switching frequency to obtain the second duty cycle. When the first switching frequency is less than the minimum frequency of the switching frequency range, the preset duty cycle is adjusted according to the minimum frequency and the first switching frequency to obtain the first duty cycle. This realizes the control of centrally symmetrical PWM when the first switching frequency exceeds the switching frequency range, thereby increasing the adjustment range.

[0143] In some embodiments, optionally, determining the second duty cycle based on a preset duty cycle, a maximum frequency and a first switching frequency includes: determining a first frequency difference between the first switching frequency and the maximum frequency; and determining the second duty cycle based on the first frequency difference, the preset duty cycle and a proportional coefficient.

[0144] In this embodiment, when the first switching frequency is greater than the maximum frequency, the difference between the first switching frequency and the maximum frequency is calculated to obtain a first frequency difference, and the preset duty cycle is reduced based on the first frequency difference to obtain a second duty cycle, that is, the difference between the preset duty cycle and the product of the first frequency difference and the proportional coefficient is used as the second duty cycle.

[0145] Specifically, the calculation formula (7) of the second duty cycle is as follows:

[0146] D S =0.5-(f S -f max )×k; (7)

[0147] Among them, D S is the second duty cycle, 0.5 is the preset duty cycle, fS is the first switching frequency, f max is the maximum frequency, and k is the proportional coefficient.

[0148] It should be noted that when the first switching frequency is greater than the maximum frequency, the preset duty cycle is used as the first duty cycle.

[0149] In an embodiment of the present application, a first frequency difference is obtained by calculating the difference between the first switching frequency and the maximum frequency, and a preset duty cycle is adjusted based on the calculated first frequency difference to obtain a second duty cycle, thereby improving the accuracy of controlling the DC conversion device based on the second duty cycle, the maximum frequency and the preset duty cycle serving as the first duty cycle.

[0150] In some embodiments, optionally, determining the first duty cycle based on a preset duty cycle, a minimum frequency value and a first switching frequency includes: determining a second frequency difference between the minimum frequency value and the first switching frequency; and determining the first duty cycle based on the second frequency difference, the preset duty cycle and a proportional coefficient.

[0151] In this embodiment, when the first switching frequency is less than the minimum frequency value, the difference between the minimum frequency value and the first switching frequency is calculated to obtain a second frequency difference value, and the preset duty cycle is reduced based on the second frequency difference value to obtain the first duty cycle, that is, the difference between the preset duty cycle and the product of the second frequency difference value and the proportional coefficient is used as the first duty cycle.

[0152] Specifically, the calculation formula (8) of the first duty cycle is as follows:

[0153] D P =0.5-(f min -f S )×k; (8)

[0154] Among them, D P is the first duty cycle, 0.5 is the preset duty cycle, f S is the first switching frequency, f min is the minimum frequency, and k is the proportional coefficient.

[0155] It should be noted that when the first switching frequency is less than the minimum frequency, the preset duty cycle is used as the second duty cycle.

[0156] In an embodiment of the present application, a second frequency difference is obtained by calculating the difference between the minimum frequency and the first switching frequency, and the preset duty cycle is adjusted based on the calculated second frequency difference to obtain the first duty cycle, thereby improving the accuracy of controlling the DC conversion device based on the first duty cycle, the maximum frequency and the preset duty cycle as the second duty cycle.

[0157] In some embodiments, optionally, the DC conversion device includes a resonant cavity, which is arranged between the primary H-bridge circuit and the secondary H-bridge circuit; according to the output voltage of the secondary H-bridge circuit, the first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit is determined, including: performing proportional integration on the voltage difference between the output voltage and the reference voltage to obtain a proportional integration result; and determining the first switching frequency according to the resonant frequency and the proportional integration result.

[0158] In the embodiment of the present application, in the process of determining the first switching frequency by synchronous equal-width frequency conversion, the difference signal between the output voltage signal of the secondary side H-bridge circuit and the reference voltage signal is proportionally integrated to obtain a proportional integration result, thereby determining the first switching frequency according to the proportional integration result and the resonant frequency. By controlling the output voltage of the secondary side H-bridge circuit, the first switching frequency in the synchronous equal-width frequency conversion control stage can be determined.

[0159] Fig.10 Schematic diagram of control loop in some embodiments of the present application is shown, such as Fig.10 As shown, Vref is the reference voltage signal, VH is the output voltage signal of the secondary side H-bridge circuit, PI is the proportional integral calculation, fr is the resonant frequency, and PIout is the first switching frequency of the output.

[0160] In some embodiments, optionally, the DC conversion device includes a resonant cavity, which is arranged between the primary H-bridge circuit and the secondary H-bridge circuit; the resonant cavity includes at least one of the following: LLC resonant cavity, L-LLC resonant cavity, CLLC resonant cavity.

[0161] In an embodiment of the present application, a resonant cavity is also provided in the DC conversion device. The resonant cavity is arranged between the primary H-bridge circuit and the secondary H-bridge circuit. The resonant cavity can be selected as an LLC resonant cavity, an L-LLC resonant cavity, or a CLLC resonant cavity.

[0162] Fig.11 FIG. 2 shows a circuit topology diagram of a DC conversion device provided in some embodiments of the present application. Figure 2 and Fig.11 As shown, the resonant cavity is an L-LLC resonant cavity.

[0163] Fig.12 FIG. 3 shows a circuit topology diagram of a DC conversion device provided in some embodiments of the present application. Fig.12 As shown, the resonant cavity is an L-LLC resonant cavity.

[0164] Fig.13 FIG. 2 shows a flow chart of a control method of a DC conversion device provided in some embodiments of the present application. Fig.13 As shown, the control method of the DC conversion device includes:

[0165] Step 1302, determining whether the first switching frequency is greater than the maximum frequency, if the determination result is yes, executing step 1304, otherwise executing step 1306;

[0166] Step 1304: the first duty cycle is determined as a preset duty cycle, a second duty cycle is determined according to the preset duty cycle, the first switching frequency and the maximum frequency, and the maximum frequency is determined as the second switching frequency;

[0167] Step 1306, determining whether the first switching frequency is less than the minimum frequency, if the determination result is yes, executing step 1308, otherwise executing step 1310;

[0168] Step 1308, the second duty cycle is determined as the preset duty cycle, the first duty cycle is determined according to the preset duty cycle, the first switching frequency and the minimum frequency value, and the minimum frequency value is determined as the second switching frequency;

[0169] Step 1310: both the first duty cycle and the second duty cycle are determined to be preset duty cycles, and the first switching frequency is determined to be the second switching frequency;

[0170] Step 1312: performing variable frequency modulation according to the first duty cycle, the second duty cycle and the second switching frequency.

[0171] Fig.14 FIG. 1 shows one of the output voltage simulation waveforms of the secondary side H-bridge circuit provided in some embodiments of the present application, such as Fig.14 As shown, VL = 50V, transformer ratio is 1:8, VH reference value Vref = 300V, VH simulation waveform is as follows, at this time the frequency is the maximum frequency, Dp = 0.5, D s =0.36.

[0172] Fig.15 FIG. 2 shows a second output voltage simulation waveform diagram of the secondary side H-bridge circuit provided in some embodiments of the present application, such as Fig.15 As shown, VL = 50V, the transformer ratio is 1:8, VH reference value Vref = 390V, VH simulation waveform is as follows, at this time the frequency is 1.04×f r , D p =0.5, D s =0.5.

[0173] Fig.16 FIG. 3 shows a third output voltage simulation waveform diagram of the secondary side H-bridge circuit provided in some embodiments of the present application, such as Fig.16 As shown, VL = 50V, the transformer ratio is 1:8, VH reference value Vref = 420V, and the VH simulation waveform is as follows. At this time, the frequency is the minimum frequency, D p =0.36, Ds =0.5.

[0174] Wherein, VL is the input voltage of the primary H-bridge circuit, VH is the output voltage of the secondary H-bridge circuit, Dp is the first duty cycle, and Ds is the second duty cycle.

[0175] According to one embodiment of the present application, Fig.17 One of the structural block diagrams of a control device for a DC conversion device is shown in some embodiments of the present application, such as Fig.17 As shown, a control device 1700 of a DC conversion device is proposed. The DC conversion device includes a primary side H-bridge circuit and a secondary side H-bridge circuit. The control device 1700 of the DC conversion device includes:

[0176] A determination module 1702 is used to determine a first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit according to the output voltage of the secondary H-bridge circuit;

[0177] A determination module 1702 is used to determine a second switching frequency, a first duty cycle, and a second duty cycle according to the first switching frequency and the switching frequency range, wherein the first duty cycle is the duty cycle of the upper half bridge arm in the primary side H-bridge circuit, and the second duty cycle is the duty cycle of the upper half bridge arm in the secondary side H-bridge circuit;

[0178] The control module 1704 is used to control the primary side H-bridge circuit and the secondary side H-bridge circuit according to the second switching frequency, the first duty cycle and the second duty cycle.

[0179] In the embodiment of the present application, synchronous equal-width frequency conversion control of the DC conversion device is highly efficient and soft switching is easy to achieve, thereby enabling seamless switching of battery charging and discharging. The center-symmetrical PWM control gain range is relatively wide, and the gain is independent of power and only related to the duty cycle. The present application combines synchronous equal-width frequency conversion control with center-symmetrical PWM control. In the initial stage, synchronous equal-width frequency conversion control is first performed. When the first switching frequency obtained by the synchronous equal-width frequency conversion control exceeds the switching frequency range, center-symmetrical PWM control is performed. While ensuring a relatively wide soft switching range, the gain adjustment range is improved, thereby improving the current sharing capability and SOC balancing capability of the DC conversion device.

[0180] In some embodiments, optionally, the control device 1800 of the DC conversion device includes:

[0181] A comparison module, used for comparing the first switching frequency with a maximum frequency value and a minimum frequency value in a switching frequency range;

[0182] The determination module 1702 is configured to determine the second switching frequency according to the comparison result; and determine the first duty cycle and the second duty cycle according to the comparison result and the first switching frequency.

[0183] In the embodiment of the present application, by comparing and judging whether the first switching frequency is within the switching frequency range, and determining the second switching frequency, the first duty cycle, and the second duty cycle based on the comparison result, a segmented method of synchronous equal-width frequency conversion control and center-symmetrical PWM control is implemented, thereby further ensuring a wider soft switching range while improving the gain adjustment range.

[0184] In some embodiments, optionally, the determination module 1702 is configured to determine the first switching frequency as the second switching frequency when the first switching frequency is less than or equal to the maximum frequency value and greater than or equal to the minimum frequency value;

[0185] A determination module 1702, configured to determine the maximum frequency as a second switching frequency when the first switching frequency is greater than the maximum frequency;

[0186] The determination module 1702 is configured to determine the minimum frequency value as the second switching frequency when the first switching frequency is less than the minimum frequency value.

[0187] In an embodiment of the present application, in the process of controlling a DC conversion device, after determining the first switching frequency by means of synchronous equal-width frequency conversion control, when the first switching frequency is within the switching frequency range, the first switching frequency is determined as the second switching frequency to control the DC conversion device; when the first switching frequency is greater than the maximum frequency value of the switching frequency range, the maximum frequency value is used as the second switching frequency to control the DC conversion device; when the first switching frequency is less than the minimum frequency value of the switching frequency range, the minimum frequency value is used as the second switching frequency to control the DC conversion device, thereby avoiding the second switching frequency from exceeding the range of synchronous equal-width frequency conversion regulation, making it easy for the DC conversion device to achieve soft switching, and enabling seamless switching of battery charging and discharging.

[0188] In some embodiments, optionally, the determination module 1702 is configured to determine both the first duty cycle and the second duty cycle as preset duty cycles when the first switching frequency is less than or equal to the maximum frequency value and greater than or equal to the minimum frequency value;

[0189] A determination module 1702, configured to determine the first duty cycle as a preset duty cycle when the first switching frequency is greater than the maximum frequency, and determine a second duty cycle based on the preset duty cycle, the maximum frequency and the first switching frequency;

[0190] The determination module 1702 is used to determine the second duty cycle as the preset duty cycle when the first switching frequency is less than the minimum frequency value, and determine the first duty cycle based on the preset duty cycle, the minimum frequency value and the first switching frequency.

[0191] In an embodiment of the present application, after the first switching frequency is determined by synchronous equal-width frequency conversion control, when the first switching frequency is within the switching frequency range, the first switching frequency is determined as the second switching frequency to control the DC conversion device, and the first duty cycle and the second duty cycle are both determined as preset duty cycles. When the first switching frequency is greater than the maximum frequency of the switching frequency range, the preset duty cycle is adjusted according to the maximum frequency and the first switching frequency to obtain the second duty cycle. When the first switching frequency is less than the minimum frequency of the switching frequency range, the preset duty cycle is adjusted according to the minimum frequency and the first switching frequency to obtain the first duty cycle. This realizes the control of centrally symmetrical PWM when the first switching frequency exceeds the switching frequency range, thereby increasing the adjustment range.

[0192] In some embodiments, optionally, the determination module 1702 is configured to determine a first frequency difference between the first switching frequency and the maximum frequency;

[0193] The determination module 1702 is used to determine the second duty cycle according to the first frequency difference, the preset duty cycle and the proportional coefficient.

[0194] In an embodiment of the present application, a first frequency difference is obtained by calculating the difference between the first switching frequency and the maximum frequency, and a preset duty cycle is adjusted based on the calculated first frequency difference to obtain a second duty cycle, thereby improving the accuracy of controlling the DC conversion device based on the second duty cycle, the maximum frequency and the preset duty cycle serving as the first duty cycle.

[0195] In some embodiments, optionally, the determination module 1702 is configured to determine a second frequency difference between the minimum frequency value and the first switching frequency;

[0196] The determination module 1702 is used to determine the first duty cycle according to the second frequency difference, the preset duty cycle and the proportional coefficient.

[0197] In an embodiment of the present application, a second frequency difference is obtained by calculating the difference between the minimum frequency and the first switching frequency, and the preset duty cycle is adjusted based on the calculated second frequency difference to obtain the first duty cycle, thereby improving the accuracy of controlling the DC conversion device based on the first duty cycle, the maximum frequency and the preset duty cycle as the second duty cycle.

[0198] In some embodiments, optionally, the DC conversion device includes a resonant cavity, and the resonant cavity is arranged between the primary H-bridge circuit and the secondary H-bridge circuit; the control device 1800 of the DC conversion device includes:

[0199] An operation module, used for performing proportional integration on the voltage difference between the output voltage and the reference voltage to obtain a proportional integration result;

[0200] The determination module 1702 is used to determine the first switching frequency according to the resonant frequency and the proportional integral result.

[0201] In the embodiment of the present application, in the process of determining the first switching frequency by synchronous equal-width frequency conversion, the difference signal between the output voltage signal of the secondary side H-bridge circuit and the reference voltage signal is proportionally integrated to obtain a proportional integration result, thereby determining the first switching frequency according to the proportional integration result and the resonant frequency. By controlling the output voltage of the secondary side H-bridge circuit, the first switching frequency in the synchronous equal-width frequency conversion control stage can be determined.

[0202] In some embodiments, optionally, the DC conversion device includes a resonant cavity, which is arranged between the primary H-bridge circuit and the secondary H-bridge circuit; the resonant cavity includes at least one of the following: LLC resonant cavity, L-LLC resonant cavity, CLLC resonant cavity.

[0203] In an embodiment of the present application, a resonant cavity is also provided in the DC conversion device. The resonant cavity is arranged between the primary H-bridge circuit and the secondary H-bridge circuit. The resonant cavity can be selected as an LLC resonant cavity, an L-LLC resonant cavity, or a CLLC resonant cavity.

[0204] According to one embodiment of the present application, Fig.18 FIG. 2 shows a second structural block diagram of a control device for a DC conversion device provided in some embodiments of the present application. Fig.18 As shown, the control device 1800 of the DC converter includes a processor 1802 and a memory 1804. The memory 1804 stores a program or instruction. When the program or instruction is executed by the processor 1802, the steps of the control method of the DC converter in any of the above embodiments are implemented. Therefore, the control device 1800 of the DC converter has all the beneficial effects of the control method of the DC converter in any of the above embodiments, which will not be described in detail.

[0205] According to one embodiment of the present application, optionally, a readable storage medium is provided, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the control method of the DC conversion device in any of the above embodiments are implemented, thereby having all the beneficial technical effects of the control method of the DC conversion device in any of the above embodiments.

[0206] The readable storage medium includes a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0207] A computer readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device. A computer readable storage medium may be an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above devices, but is not limited thereto. A non-exhaustive list of more specific examples of computer readable storage media includes: portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory card, floppy disk, encoding mechanical device (such as a punch card or a groove with a raised structure with instructions recorded) and any suitable combination of the above devices. The computer readable storage medium used herein should not be understood as a transmission signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium, or an electrical signal transmitted through a wire, etc.

[0208] Fig.19 The structure block diagram of the energy storage system provided in some embodiments of the present application is shown as follows: Fig.19 As shown, according to one embodiment of the present application, optionally, there is provided an energy storage system 1900, including: at least two battery clusters 1904, a DC conversion device 1906 is arranged between at least two battery clusters 1904; such as the control device 1700 of the DC conversion device in any of the above embodiments, and / or the readable storage medium 1902 in any of the above embodiments, thus having all the beneficial technical effects of the control device 1700 of the DC conversion device in any of the above embodiments, and / or the readable storage medium 1902 in any of the above embodiments, which will not be described in detail herein.

[0209] It should be clarified that in the claims, specification and drawings of the present application, the term "multiple" refers to two or more than two. Unless otherwise clearly defined, the orientation or position relationship indicated by the terms "upper" and "lower" is based on the orientation or position relationship shown in the drawings, which is only for the purpose of more conveniently describing the present application and making the description process easier, rather than indicating or implying that the device or element referred to must have the specific orientation described, be constructed and operated in a specific orientation, so these descriptions cannot be understood as limitations on the present application; the terms "connect", "install", "fix" and the like should be understood in a broad sense. For example, "connection" can be a fixed connection between multiple objects, or a detachable connection between multiple objects, or an integral connection; it can be a direct connection between multiple objects, or an indirect connection between multiple objects through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood based on the specific circumstances of the above data.

[0210] In the claims, specification and drawings of the present application, the description of the terms "one embodiment", "some embodiments", "specific embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the claims, specification and drawings of the present application, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0211] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for a DC converter, characterized in that: The DC conversion device includes a primary H-bridge circuit and a secondary H-bridge circuit, and the control method of the DC conversion device includes: Determining a first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit according to the output voltage of the secondary H-bridge circuit; Determining a second switching frequency, a first duty cycle, and a second duty cycle according to the first switching frequency and the switching frequency range, wherein the first duty cycle is the duty cycle of the upper half bridge arm in the primary H-bridge circuit, and the second duty cycle is the duty cycle of the upper half bridge arm in the secondary H-bridge circuit; The primary H-bridge circuit and the secondary H-bridge circuit are controlled according to the second switching frequency, the first duty cycle, and the second duty cycle.

2. The control method of the DC converter according to claim 1, characterized in that: The determining the second switching frequency, the first duty cycle and the second duty cycle according to the first switching frequency and the switching frequency range includes: Comparing the first switching frequency with a maximum frequency and a minimum frequency in the switching frequency range; Determine the second switching frequency according to the comparison result; and The first duty cycle and the second duty cycle are determined according to the comparison result and the first switching frequency.

3. The control method of the DC converter according to claim 2, characterized in that: The determining the second switching frequency according to the comparison result includes: When the first switching frequency is less than or equal to the maximum frequency value and greater than or equal to the minimum frequency value, determining the first switching frequency as the second switching frequency; When the first switching frequency is greater than the maximum frequency, determining the maximum frequency as the second switching frequency; When the first switching frequency is less than the minimum frequency value, the minimum frequency value is determined as the second switching frequency.

4. The control method of the DC converter according to claim 2, characterized in that: The determining the first duty cycle and the second duty cycle according to the comparison result and the first switching frequency includes: When the first switching frequency is less than or equal to the maximum frequency value and greater than or equal to the minimum frequency value, determining both the first duty cycle and the second duty cycle as preset duty cycles; When the first switching frequency is greater than the maximum frequency, the first duty cycle is determined as the preset duty cycle, and the second duty cycle is determined based on the preset duty cycle, the maximum frequency and the first switching frequency; In a case where the first switching frequency is less than the minimum frequency value, the second duty cycle is determined as the preset duty cycle, and the first duty cycle is determined based on the preset duty cycle, the minimum frequency value, and the first switching frequency.

5. The control method of the DC converter according to claim 4, characterized in that: The determining the second duty cycle based on the preset duty cycle, the maximum frequency and the first switching frequency includes: determining a first frequency difference between the first switching frequency and the frequency maximum; The second duty cycle is determined according to the first frequency difference, the preset duty cycle and the proportional coefficient.

6. The control method of the DC converter according to claim 4, characterized in that: The determining the first duty cycle based on the preset duty cycle, the minimum frequency value and the first switching frequency includes: determining a second frequency difference between the minimum frequency value and the first switching frequency; The first duty cycle is determined according to the second frequency difference, the preset duty cycle and the proportional coefficient.

7. The control method of a DC converter according to any one of claims 1 to 6, characterized in that: The determining, according to the output voltage of the secondary H-bridge circuit, the first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit comprises: Performing proportional integration on the voltage difference between the output voltage and the reference voltage to obtain a proportional integration result; The first switching frequency is determined according to the resonant frequency and the proportional integral result.

8. The control method of a DC converter according to any one of claims 1 to 6, characterized in that: The DC conversion device includes a resonant cavity, which is arranged between the primary H-bridge circuit and the secondary H-bridge circuit; the resonant cavity includes at least one of the following: an LLC resonant cavity, an L-LLC resonant cavity, and a CLLC resonant cavity.

9. A control device for a DC converter, characterized in that: The DC conversion device includes a primary H-bridge circuit and a secondary H-bridge circuit, and the control device of the DC conversion device includes: A determination module, used to determine a first switching frequency of the primary H-bridge circuit and the secondary H-bridge circuit according to the output voltage of the secondary H-bridge circuit; The determination module is used to determine the second switching frequency, the first duty cycle and the second duty cycle according to the first switching frequency and the switching frequency range, wherein the first duty cycle is the duty cycle of the upper half bridge arm in the primary H-bridge circuit, and the second duty cycle is the duty cycle of the upper half bridge arm in the secondary H-bridge circuit; A control module is used to control the primary H-bridge circuit and the secondary H-bridge circuit according to the second switching frequency, the first duty cycle and the second duty cycle.

10. A control device for a DC converter, characterized in that: include: processor; A memory, wherein a program or instruction is stored in the memory, and the processor implements the steps of the control method of the DC converter device according to any one of claims 1 to 8 when executing the program or instruction in the memory.

11. A readable storage medium, characterized in that: The readable storage medium stores a program or instruction, and when the program or instruction is executed by the processor, the steps of the control method of the DC converter device according to any one of claims 1 to 8 are implemented.

12. An energy storage system, characterized in that: include: At least two battery clusters, with a DC conversion device disposed between at least two of the battery clusters; The control device of the DC converter according to claim 9 or 10; and / or The readable storage medium as claimed in claim 11.

Images