Control method and device of full-bridge three-level direct-current converter and electronic equipment

Abstract

The invention discloses a control method and device of a full-bridge three-level direct-current converter and electronic equipment. In the control process of the full-bridge three-level direct-current converter, on the basis of the size of a duty ratio coefficient d, dlt; when 1, controlling the direct-current converter to work in a two-level mode according to the PWM driving signal of the first preset rule; when 1 < = dlt; 2, controlling the direct-current converter to work in a three-level mode according to the PWM driving signal of the second preset rule; when the two-level mode needs to be switched to the three-level mode or the three-level mode needs to be switched to the two-level mode, namely, when d is equal to 1, the PWM driving signal of the first preset rule and the PWM driving signal of the second preset rule have the same waveform. Therefore, at the moment of switching between the two-level mode and the three-level mode, the driving waveforms of all the switching tubes Q1 to Q8 are not suddenly changed before and after switching, smooth switching is realized, and the advantage of wide output voltage range of the full-bridge three-level direct current converter can be brought into full play.

Description

Technical Field

[0001] The present invention relates to the technical field of DC converters, and in particular to a control method, device and electronic equipment for a full-bridge three-level DC converter. Background Art

[0002] With the increasing complexity of application scenarios and the integration of power supply systems, the output voltage range of DC power supply systems has gradually increased, requiring the power supply system to have a wide range of voltage output capabilities. Full-bridge three-level DC converters can meet these requirements due to their advantages such as low switch voltage stress, soft switching, and a wide range of output voltages. They have been widely used in scenarios such as communication power supplies, battery energy storage, and renewable energy generation. Existing full-bridge three-level DC converters mainly include a three-level neutral point clamped (NPC) bridge arm, a resonant network (or inductor / capacitor network), an isolation transformer, and a rectifier output circuit.

[0003] Existing research on controlling full-bridge three-level DC converters focuses on modulating the on / off states of the converter's switches, hoping to achieve higher efficiency and lower losses. For example, in "Optimal Switching Methods for Full-Bridge Three-Level DC Converters," Ma Yundong et al. analyzed the constraints that the switching method should meet and proposed a switching method that maximizes the converter's energy transfer ratio, minimizes filter inductor current ripple, and achieves soft switching of the switches. In "Research on a Novel Control Strategy for a Three-Level Full-Bridge DC Converter," Liu Jilong et al. proposed a symmetrical dual-phase-shift control strategy. This strategy can shape the transformer primary voltage waveform into an odd function, making it closer to a sine wave, thereby reducing voltage THD and improving the transformer's harmonic losses. In "A Novel Control Strategy for Full-Bridge Three-Level Converters," Zhang Zhiliang et al. proposed a dual-phase-shift modulation method to achieve a wide range of output voltage variations.

[0004] The full-bridge three-level DC converter can operate in two-level mode (the amplitude of the transformer primary voltage step wave is and 0, V in is the input voltage), and can also work in three-level mode (the transformer primary voltage step amplitude is V in 、 In the existing control method, it is impossible to smoothly switch the full-bridge three-level DC converter between the two-level mode and the three-level mode, resulting in the inability to fully utilize the advantage of the wide range of output voltage variation of the full-bridge three-level DC converter. Summary of the Invention

[0005] In view of this, the present invention provides a control method, device and electronic device for a full-bridge three-level DC converter to solve the problem of how to achieve smooth switching between the two-level mode and the three-level mode during the control of the full-bridge three-level DC converter.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention is to provide a control method for a full-bridge three-level DC converter. The full-bridge three-level DC converter includes a left bridge arm and a right bridge arm connected in parallel. The left bridge arm includes a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4 connected in series in sequence. The right bridge arm includes a switch tube Q5, a switch tube Q6, a switch tube Q7, and a switch tube Q8 connected in series in sequence. The control method includes the steps:

[0008] S11. Based on the set output voltage value u ref and the output voltage value u c1 at the first moment, calculate and obtain the duty cycle coefficient d, where 0 < d < 2;

[0009] S12. Set the control variable according to the duty cycle coefficient d, including: if 0 < d < 1, set the control variable as d 2L , and d 2L = d; if 1 ≤ d < 2, set the control variable as d 3L , and d 3L = d - 1;

[0010] S13. If the control variable is d 2L , control and drive the eight switch tubes Q 1～ Q8 according to the PWM drive signal of the first preset rule, so that the full-bridge three-level DC converter operates in the two-level mode and outputs the output voltage u c2 at the second moment, and

[0011] if the control variable is d 3L , control and drive the eight switch tubes Q 1～ Q8 according to the PWM drive signal of the second preset rule, so that the full-bridge three-level DC converter operates in the three-level mode and outputs the output voltage u c2 at the second moment, and[[ID= forty-four]] < thousands of nine hundred and eleven]]

[0012] S14. Take the output voltage u c2 at the second moment obtained in step S13 as the output voltage value u c1 at the first moment in step S11, and loop and repeat steps S11 to S13 until the output voltage uc2 Equal to the set output voltage value u ref ;

[0013] Among them, V in is the input voltage of the full-bridge three-level DC converter, K is the turns ratio of the transformer in the full-bridge three-level DC converter; when d=1, the PWM drive signal of the first preset rule and the PWM drive signal of the second preset rule have the same waveform.

[0014] In a specific solution, the step S11 includes: setting the output voltage value u ref And the output voltage value u at the first moment c1 A voltage difference is obtained by performing a difference, and a voltage control calculation and a proportional gain calculation are performed on the voltage difference in sequence to obtain the duty cycle coefficient d.

[0015] In a specific solution, the output voltage upper limit of the full-bridge three-level DC converter in the two-level mode is When the output voltage value u at the first moment c1 With the output voltage upper limit u 2LMAX When they are equal, d=1.

[0016] In a specific solution, in the PWM drive signal of the first preset rule, eight switch tubes Q 1～ The duty cycle of the waveform of the PWM drive signal of Q8 is 50%, and the waveforms of the switch tubes Q1 and Q4 are complementary to each other, the waveforms of the switch tubes Q2 and Q3 are complementary to each other, the waveforms of the switch tubes Q5 and Q6 are the same as the waveform of the switch tube Q1, the waveforms of the switch tubes Q7 and Q8 are the same as the waveform of the switch tube Q4, the phase shift control is performed between the switch tubes Q2 and Q4, and the phase shift control is performed between the switch tubes Q3 and Q1; wherein, the time difference between the rising edge of the switch tube Q2 and the rising edge of the switch tube Q4, and the time difference between the rising edge of the switch tube Q3 and the rising edge of the switch tube Q1, and the ratio of half a switching period are 1-d respectively. 2L ;

[0017] In the PWM driving signal of the second preset rule, the eight switch tubes Q 1～The duty ratios of the waveforms of the PWM drive signals of Q8 are 50% respectively. Moreover, the waveforms of switch tubes Q1 and Q4 conduct complementarily, the waveforms of switch tubes Q2 and Q3 conduct complementarily, the waveforms of switch tubes Q5 and Q6 are the same as those of switch tube Q3, the waveforms of switch tubes Q7 and Q8 are the same as those of switch tube Q2, phase-shift control is performed between switch tube Q1 and switch tube Q2, and phase-shift control is performed between switch tube Q4 and switch tube Q3; wherein, the ratio of the time difference between the rising edge of switch tube Q1 and the rising edge of switch tube Q2, and the ratio of the time difference between the rising edge of switch tube Q4 and the rising edge of switch tube Q3 to half of the switching period are 1 - d 3L .

[0018] The second aspect of the present invention is to provide a control device for a full-bridge three-level DC converter. The full-bridge three-level DC converter includes a left bridge arm and a right bridge arm connected in parallel. The left bridge arm includes switch tubes Q1, Q2, Q3, and Q4 connected in series in sequence. The right bridge arm includes switch tubes Q5, Q6, Q7, and Q8 connected in series in sequence. The control device includes:

[0019] A first processing unit is connected to the output terminal of the full-bridge three-level DC converter to obtain the output voltage of the full-bridge three-level DC converter. The first processing unit is used to calculate and obtain a duty ratio coefficient d based on a set output voltage value u ref and the output voltage value u c1 at the first moment, where 0 < d < 2;

[0020] A second processing unit is connected to the first processing unit and is used to set a control variable according to the duty ratio coefficient d. Wherein: if 0 < d < 1, the control variable is set to d 2L , and d 2L = d; if 1 ≤ d < 2, the control variable is set to d 3L , and d 3L = d - 1;

[0021] A drive signal generation unit is connected to the second processing unit and is used to generate PWM drive signals for eight switch tubes Q 1～ Q8 and input them to the full-bridge three-level DC converter. Wherein:

[0022] If the control variable is d 2L , the drive signal generation unit generates PWM drive signals of a first preset rule to control and drive eight switch tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in a two-level mode to output the output voltage u c2 at the second moment, and

[0023] If the control variable is d 3L The driving signal generating unit generates a PWM driving signal of a second preset rule to control and drive eight switching tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in the three-level mode and outputs the output voltage u at the second moment c2 ,and

[0024] The first processing unit converts the output voltage u at the second moment into c2 Replace the output voltage value u at the first moment c1 , recalculate the duty cycle coefficient d, and repeat this cycle until the output voltage u at the second moment is c2 Equal to the set output voltage value u ref ;

[0025] Among them, V in is the input voltage of the full-bridge three-level DC converter, K is the turns ratio of the transformer in the full-bridge three-level DC converter; when d=1, the PWM drive signal of the first preset rule and the PWM drive signal of the second preset rule have the same waveform.

[0026] In a specific solution, the first processing unit includes a difference calculation module, a voltage control calculation module and a proportional gain calculation module connected in sequence; the difference calculation module sets the output voltage value u ref And the output voltage value u at the first moment c1 The voltage control calculation module performs voltage control calculation based on the calculation result of the difference calculation module, and inputs the calculation result to the proportional gain calculation module; the proportional gain calculation module performs proportional gain calculation based on the calculation result of the voltage control calculation module, and inputs the calculation result to the second processing unit.

[0027] In a specific solution, the output voltage upper limit of the full-bridge three-level DC converter in the two-level mode is When the output voltage value u at the first moment c1 With the output voltage upper limit u 2LMAX When they are equal, the duty cycle coefficient d calculated by the first processing unit is 1.

[0028] In a specific solution, the second processing unit includes a control variable setting module and a control variable output module that are interconnected; the control variable setting module receives the duty cycle coefficient d input from the first processing unit and sets a control variable according to the duty cycle coefficient d, where: when 0 < d < 1, the control variable setting module sets the control variable to d 2L , and d 2L = d; when 1 ≤ d < 2, the control variable setting module sets the control variable to d 3L , and d 3L = d - 1; the control variable output module outputs the control variable set by the control variable setting module to the drive signal generation unit.

[0029] In a specific solution, in the PWM drive signal of the first preset rule generated by the drive signal generation unit, the duty cycles of the PWM drive signals of the eight switching tubes Q 1～ Q8 are 50% respectively, and, the waveforms of the switching tubes Q1 and Q4 are complementary and conduct, the waveforms of the switching tubes Q2 and Q3 are complementary and conduct, the waveforms of the switching tubes Q5 and Q6 are the same as the waveform of the switching tube Q1, the waveforms of the switching tubes Q7 and Q8 are the same as the waveform of the switching tube Q4, phase shift control is performed between the switching tube Q2 and the switching tube Q4, and phase shift control is performed between the switching tube Q3 and the switching tube Q1; where, the time difference between the rising edge of the switching tube Q2 and the rising edge of the switching tube Q4, and the time difference between the rising edge of the switching tube Q3 and the rising edge of the switching tube Q1 and the ratio to half of the switching period are 1 - d 2L ;

[0030] In the PWM drive signal of the second preset rule generated by the drive signal generation unit, the duty cycles of the PWM drive signals of the eight switching tubes Q 1～ Q8 are 50% respectively, and, the waveforms of the switching tubes Q1 and Q4 are complementary and conduct, the waveforms of the switching tubes Q2 and Q3 are complementary and conduct, the waveforms of the switching tubes Q5 and Q6 are the same as the waveform of the switching tube Q3, the waveforms of the switching tubes Q7 and Q8 are the same as the waveform of the switching tube Q2, phase shift control is performed between the switching tube Q1 and the switching tube Q2, and phase shift control is performed between the switching tube Q4 and the switching tube Q3; where, the time difference between the rising edge of the switching tube Q1 and the rising edge of the switching tube Q2, and the time difference between the rising edge of the switching tube Q4 and the rising edge of the switching tube Q3 and the ratio to half of the switching period are 1 - d 3L .

[0031] The third aspect of the present invention is to provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the control method of the full-bridge three-level DC converter as described above is implemented.

[0032] For the control method, device, and electronic device of the full-bridge three-level DC converter provided by the embodiments of the present invention, during the control process of the full-bridge three-level DC converter, based on the magnitude of the duty cycle coefficient d: when 0 < d < 1, the DC converter is controlled to operate in the two-level mode according to the PWM drive signal of the first preset rule; when 1 ≤ d < 2, the DC converter is controlled to operate in the three-level mode according to the PWM drive signal of the second preset rule; when it is necessary to switch from the two-level mode to the three-level mode or from the three-level mode to the two-level mode, that is, when d = 1, the PWM drive signals of the first preset rule and the second preset rule have the same waveform. Therefore, at the switching moment between the two-level mode and the three-level mode, the drive waveforms of all the switching transistors Q 1～ Q8 have no mutation before and after switching, achieving smooth switching. Thus, in the solution of the present invention, through the segmented control method, smooth switching between the two-level mode and the three-level mode is achieved, combining the respective advantages of the two-level mode and the three-level mode under wide-range working conditions, enabling dynamic selection of the optimal mode, and helping to give full play to the advantage of the wide output voltage range of the full-bridge three-level DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a flowchart of the control method of the full-bridge three-level DC converter in the embodiments of the present invention;

[0034] Figure 2 is a circuit structure diagram of the full-bridge three-level DC converter in the embodiments of the present invention;

[0035] Figure 3 is a block diagram of the control device of the full-bridge three-level DC converter in the embodiments of the present invention;

[0036] Figure 4 is a waveform diagram of the PWM drive signal of the first preset rule in the embodiments of the present invention;

[0037] Figure 5 is a waveform diagram of the PWM drive signal of the second preset rule in the embodiments of the present invention;

[0038] Figure 6 is a waveform diagram of the output voltage in a specific embodiment of the present invention;

[0039] Figure 7 is a waveform diagram of the duty cycle coefficient in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the present invention more apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the present invention shown in and described with reference to the accompanying drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0041] It should be noted that the same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0042] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, the accompanying drawings only show structures and / or processing steps closely related to the solutions according to the present invention, while other details that are not closely related to the present invention are omitted.

[0043] An embodiment of the present invention first provides a control method for a full-bridge three-level DC converter, which is used to control the full-bridge three-level DC converter. Figure 1 is a flow chart of a control method for a full-bridge three-level DC converter in this embodiment, Figure 2 3 is a circuit structure diagram of a full-bridge three-level DC converter in this embodiment.

[0044] See Figure 2 The full-bridge three-level DC converter mainly includes a three-level neutral point clamped left bridge arm and a right bridge arm connected in parallel with each other, and also includes a resonant network, a high-frequency isolation transformer and a rectifier output circuit. Figure 2 In the figure, the left bridge arm includes the switch tubes Q1, Q2, Q3 and Q4 connected in series, and the right bridge arm includes the switch tubes Q5, Q6, Q7 and Q8 connected in series. in is the input voltage, C S1 and C S2 is the clamping capacitor, D C1 ~D C4 is the clamping diode, K is the turns ratio of the transformer, L r is the resonant inductance, L f is the filter inductor, u c is the output voltage.

[0045] Refer to Figure 1 , the control method of the full-bridge three-level DC converter in this embodiment includes the following steps:

[0046] S11. Based on the set output voltage value u ref and the output voltage value u c1 at the first moment, calculate and obtain the duty cycle coefficient d, where 0 < d < 2.

[0047] In a specific solution, the step S11 includes: subtracting the set output voltage value u ref from the output voltage value u c1 at the first moment to obtain a voltage difference, and performing voltage control calculation and proportional gain calculation on the voltage difference in sequence to obtain the duty cycle coefficient d.

[0048] Among them, the upper limit value of the output voltage of the full-bridge three-level DC converter in the two-level mode is When the output voltage value u c1 at the first moment is equal to the output voltage upper limit value u 2LMAX , d = 1.

[0049] Step S12. Set the control variable according to the duty cycle coefficient d, including: if 0 < d < 1, then set the control variable as d 2L , and d 2L = d; if 1 ≤ d < 2, then set the control variable as d 3L , and d 3L = d - 1.

[0050] Step S13. If the control variable is d 2L , then control and drive eight switching tubes Q 1～ Q8 according to the PWM drive signal of the first preset rule, so that the full-bridge three-level DC converter works in the two-level mode to output the output voltage u c2 at the second moment, and Among them, d 2L can be understood as the duty cycle (0 < d AB ) of the voltage component with an amplitude of in the arm voltage V 2L <1) of the full-bridge three-level DC converter in the two-level mode.

[0051] If the control variable is d 3L , then control and drive eight switching tubes Q 1～ Q8 according to the PWM drive signal of the second preset rule, so that the full-bridge three-level DC converter works in the three-level mode to output the output voltage u c2 at the second moment, and Among them, d 3L It can be understood that in the three-level mode, the bridge arm voltage V AB The median amplitude is V in The duty cycle of the voltage component (0 <d 3L <1).

[0052] Step S14: The output voltage u at the second moment obtained in step S13 is c2 As the output voltage value u at the first moment in step S11 c1 , repeat steps S11 to S13 until the output voltage u at the second moment obtained in step S13 is c2 Equal to the set output voltage value u ref .

[0053] When d=1, the PWM driving signal of the first preset rule and the PWM driving signal of the second preset rule have the same waveform.

[0054] Wherein, the set output voltage value u ref Refers to the output voltage that the DC converter needs to output according to the instruction received by the device. The output voltage value u at the first moment is c1 Refers to the real-time output voltage u of the DC converter c When the set output voltage value u is reached ref The voltage value at a certain moment before, the output voltage value u at the first moment c1 It can be based on the real-time output voltage u c Continuously updated until the final real-time output voltage u c Reach the set output voltage value u ref For example, when the device starts working, the initial output voltage u c is 0, and a voltage instruction of 1500V is received, then the set output voltage value u ref is 1500V, and the initial output voltage value u at the first moment is c1 The real-time output voltage u of the DC converter in a control cycle is c The output voltage u changes to the second moment c2 , then the output voltage value u at the first moment is c1 Based on the real-time output voltage, the output voltage u at the second moment is updated c2 The next cycle is carried out until the output voltage u at the second moment is finally obtained. c2 (Real-time output voltage u c ) reaches the set output voltage value u ref .

[0055] For the control method provided in the above embodiments, during the control process of the full-bridge three-level DC converter, based on the magnitude of the duty cycle coefficient d: when 0 < d < 1, the DC converter is controlled to operate in the two-level mode according to the PWM drive signal of the first preset rule; when 1 ≤ d < 2, the DC converter is controlled to operate in the three-level mode according to the PWM drive signal of the second preset rule; when it is necessary to switch from the two-level mode to the three-level mode or from the three-level mode to the two-level mode, that is, when d = 1, the PWM drive signals of the first preset rule and the second preset rule have the same waveform. Therefore, at the switching moment between the two-level mode and the three-level mode, all the switching tubes Q 1～ The drive waveforms of Q8 do not have sudden changes before and after the switching, achieving smooth switching. Thus, in the solution of the present invention, through the segmented control method, smooth switching between the two-level mode and the three-level mode is achieved, combining the respective advantages of the two-level mode and the three-level mode under wide-range working conditions, being able to dynamically select the optimal mode, which helps to fully exert the advantage of the wide output voltage range of the full-bridge three-level DC converter.

[0056] As a preferred solution, in this embodiment, the waveforms of the PWM drive signal of the first preset rule (i.e., the PWM drive signal of the two-level mode) and the PWM drive signal of the second preset rule (i.e., the PWM drive signal of the three-level mode) are respectively as Figure 4 and Figure 5 shown.

[0057] Specifically, referring to Figure 4 , in the PWM drive signal of the first preset rule, the duty cycles of the PWM drive signals of the eight switching tubes Q 1～ Q8 are 50% respectively, and the waveforms of the switching tube Q1 and the switching tube Q4 are complementary and conduct, the waveforms of the switching tube Q2 and the switching tube Q3 are complementary and conduct, the waveforms of the switching tube Q5 and the switching tube Q6 are the same as the waveform of the switching tube Q1, the waveforms of the switching tube Q7 and the switching tube Q8 are the same as the waveform of the switching tube Q4, phase-shift control is performed between the switching tube Q2 and the switching tube Q4 (which can also be understood as the switching tube Q7 and the switching tube Q8), and phase-shift control is performed between the switching tube Q3 and the switching tube Q1 (which can also be understood as the switching tube Q5 and the switching tube Q6).

[0058] Among them, the ratio of the time difference between the rising edge of the switching tube Q2 and the rising edge of the switching tube Q4 to half of the switching period is 1 - d 2L ; similarly, the ratio of the time difference between the rising edge of the switching tube Q3 and the rising edge of the switching tube Q1 to half of the switching period is also 1 - d 2L . In the two-level mode, the control system uses d 2L as the control variable to control the output voltage.

[0059] Specifically, see Figure 5 In the second preset rule PWM driving signal, the eight switch tubes Q 1～ The duty cycle of the waveform of the PWM drive signal of Q8 is 50%, and the waveforms of the switch tubes Q1 and Q4 are complementary to each other, the waveforms of the switch tubes Q2 and Q3 are complementary to each other, the waveforms of the switch tubes Q5 and Q6 are the same as the waveform of the switch tube Q3, the waveforms of the switch tubes Q7 and Q8 are the same as the waveform of the switch tube Q2, phase shift control is performed between the switch tubes Q1 and Q2 (which can also be understood as the switch tubes Q7 and Q8), and phase shift control is performed between the switch tubes Q4 and Q3 (which can also be understood as the switch tubes Q5 and Q6).

[0060] The ratio of the time difference between the rising edge of the switch tube Q1 and the rising edge of the switch tube Q2 to half a switching cycle is 1-d 3L Similarly, the ratio of the time difference between the rising edge of the switch tube Q4 and the rising edge of the switch tube Q3 to half a switching cycle is also 1-d 3L In three-level mode, the control system will d 3L As a control variable to achieve control of the output voltage.

[0061] Combine Figure 4 and Figure 5 The waveform diagram, when d = 1, corresponds to d in the two-level mode 2L =1 and d in three-level mode 3L =0, at this time, the PWM drive signals of the two working modes are the same, that is, the rising edge of the switch tube Q2 is consistent with the rising edge of the switch tube Q7 / Q8, and the falling edge of the switch tube Q1, the rising edge of the switch tube Q3 is consistent with the rising edge of the switch tube Q5 / Q6, and the falling edge of the switch tube Q4. Therefore, at the moment of switching between the two-level mode and the three-level mode, all the switch tubes Q 1～ The driving waveform of Q8 has no sudden change before and after switching, achieving smooth switching.

[0062] The embodiment of the present invention further provides a control device for a full-bridge three-level DC converter, which is used to execute the control method described in the above embodiment, and is used to control a full-bridge three-level DC converter. Figure 2 The full-bridge three-level DC converter shown is controlled so that the full-bridge three-level DC converter can achieve smooth switching between the two-level mode and the three-level mode.

[0063] See Figure 3 The control device mainly includes a first processing unit 1, a second processing unit 2 and a drive signal generating unit 3.

[0064] Among them, the first processing unit 1 is connected to the output terminal of the full-bridge three-level DC converter to obtain the output voltage u of the full-bridge three-level DC converter c , and receives the set output voltage value u from the outside ref . The first processing unit 1 is configured to calculate and obtain a duty cycle coefficient d based on the set output voltage value u ref and the output voltage value u at the first moment c1 , where 0 < d < 2. That is, the first processing unit 1 is mainly used to execute step S11 in the control method of the above embodiment

[0065] Specifically, as in Figure 3 , the first processing unit 1 includes a difference calculation module 11, a voltage control calculation module 12, and a proportional gain calculation module 13 connected in sequence. The difference calculation module 11 subtracts the set output voltage value u ref and the output voltage value u at the first moment c1 , and inputs the calculation result to the voltage control calculation module 12. A voltage controller G is provided in the voltage control calculation module 12 V . The voltage control calculation module 12 performs voltage control calculation based on the calculation result of the difference calculation module 11, and inputs the calculation result to the proportional gain calculation module 13. The proportional gain calculation module 13 performs proportional gain calculation based on the calculation result of the voltage control calculation module 12 according to the gain coefficient , and inputs the calculation result to the second processing unit 2

[0066] Among them, the second processing unit 2 is connected to the first processing unit 1, and is configured to set a control variable according to the duty cycle coefficient d, where: if 0 < d < 1, the control variable is set to d 2L , and d 2L = d; if 1 ≤ d < 2, the control variable is set to d 3L , and d 3L = d - 1. That is, the second processing unit 2 is mainly used to execute step S12 in the control method of the above embodiment

[0067] Specifically, as in Figure 3 , the second processing unit 2 includes a control variable setting module 21 and a control variable output module 22 connected to each other. The control variable setting module 21 receives the duty cycle coefficient d input from the first processing unit 1, and sets a control variable according to the duty cycle coefficient d, where: when 0 < d < 1, the control variable setting module 21 sets the control variable to d 2L , and d 2L = d; when 1 ≤ d < 2, the control variable setting module 21 sets the control variable to d3L , and d 3L =d−1. The control variable output module 22 outputs the control variable set by the control variable setting module 21 to the drive signal generating unit 3.

[0068] The driving signal generating unit 3 is connected to the second processing unit 2 and is used to generate a signal according to the control variable d 2L or d 3L Generate eight switch tubes Q 1～ The PWM drive signal of Q8 is input to the full-bridge three-level DC converter to control the full-bridge three-level DC converter to operate in a two-level mode or a three-level mode. That is, the drive signal generating unit 3 is mainly used to execute step S13 of the control method in the above embodiment.

[0069] Specifically, if the control variable received from the second processing unit 2 is d 2L The driving signal generating unit 3 generates a PWM driving signal according to a first preset rule to control and drive eight switching tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in a two-level mode and outputs an output voltage u at the second moment c2 ,and If the control variable received from the second processing unit 2 is d 3L The driving signal generating unit 3 generates a PWM driving signal according to a second preset rule to control and drive the eight switching tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in the three-level mode and outputs the output voltage u at the second moment c2 ,and

[0070] The first processing unit 1 converts the output voltage u at the second moment into c2 Replace the output voltage value u at the first moment c1 , recalculate the duty cycle coefficient d, and repeat this cycle until the output voltage u at the second moment is c2 Equal to the set output voltage value u ref It should be noted that if Figure 3 In the output voltage u c It can be understood as the output voltage value u at the first moment input to the first processing unit 1 c1 , and after one cycle, the output voltage u at the second moment output at the output end of the full-bridge three-level DC converter c2 , at this time the output voltage u at the second moment c2 The output voltage value u at the first moment before replacement c1 Proceed to the next cycle.

[0071] Hereinafter, a simulation is performed on the control method and control device of the full-bridge three-level DC converter proposed in the above embodiment of the present invention.

[0072] Among them, the input voltage V in The output voltage upper limit in the two-level mode is 900V and the transformer turns ratio K is 0.346. The control instruction requires the output voltage value u to be set ref is 1500V, after reaching 1500V for a certain period of time, u ref Then reduce it to 900V output.

[0073] In this case, the output voltage first gradually increases from 0 to 1500V. After reaching 1500V for a certain period of time, it gradually decreases from 1500V to 900V. Because 1500V is higher than the upper output voltage limit of 1300V in the two-level mode, the DC converter first switches from two-level mode to three-level mode. Then, when the output voltage drops from 1500V to 900V, because 900V is lower than the upper output voltage limit of 1300V in the two-level mode, the DC converter switches from three-level mode to two-level mode.

[0074] In this case, the output voltage u of the DC converter is c The waveform is as Figure 6 As shown, the waveform of the duty cycle coefficient d is as follows Figure 7 As shown. Figure 6 and Figure 7 It can be seen that the working mode of the DC converter has switched twice, the first time is from the two-level mode to the three-level mode, and the second time is from the three-level mode to the two-level mode. The output voltage u c The waveform changes smoothly, and there is no voltage mutation during the switching between the two-level mode and the three-level mode. Therefore, the control method and control device applied in the present invention realize the smooth switching of the full-bridge three-level DC converter between the two-level mode and the three-level mode.

[0075] Based on the control method of the full-bridge three-level DC converter provided in the above embodiment, an embodiment of the present invention further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the control method of the full-bridge three-level DC converter described in the above embodiment are implemented.

[0076] The memory, as a computer-readable storage medium, can be used to store software programs, computer-executable programs, and modules. The processor executes the software programs, instructions, and modules stored in the memory to perform various functional applications and data processing of the device, thereby implementing the steps of the control method for a full-bridge three-level DC converter provided in the aforementioned embodiments of the present invention.

[0077] In summary, the control method and control device for the full-bridge three-level DC converter provided in the embodiments of the present invention achieve smooth switching between the two-level mode and the three-level mode through segmented control, combine the respective advantages of the two-level mode and the three-level mode under a wide range of operating conditions, and can dynamically select the optimal mode, which helps to give full play to the advantage of the wide output voltage range of the full-bridge three-level DC converter.

[0078] The above is only a specific implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A control method for a full-bridge three-level DC converter, the full-bridge three-level DC converter comprising a left bridge arm and a right bridge arm connected in parallel, the left bridge arm comprising a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4 connected in series, and the right bridge arm comprising a switch tube Q5, a switch tube Q6, a switch tube Q7, and a switch tube Q8 connected in series, characterized in that: The control method comprises the steps of: S11, based on the set output voltage value u ref And the output voltage value u at the first moment c1 , calculate the duty cycle coefficient d, where 0 <d<2; S12. Set control variables according to the duty cycle coefficient d, including: if 0 < d < 1, set the control variable to d 2L , and d 2L = d; if 1 ≤ d < 2, set the control variable to d 3L , and d 3L = d - 1; S13, if the control variable is d 2L , then the PWM drive signal according to the first preset rule controls the driving of eight switch tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in a two-level mode and outputs an output voltage u at the second moment c2 ,and If the control variable is d 3L , then the PWM drive signal according to the second preset rule controls the driving of eight switch tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in the three-level mode and outputs the output voltage u at the second moment c2 ,and S14: The output voltage u at the second moment obtained in step S13 c2 As the output voltage value u at the first moment in step S11 c1 , repeat steps S11 to S13 until the output voltage u at the second moment obtained in step S13 is c2 Equal to the set output voltage value u ref ; Among them, V in is the input voltage of the full-bridge three-level DC converter, K is the turns ratio of the transformer in the full-bridge three-level DC converter; when d=1, the PWM drive signal of the first preset rule and the PWM drive signal of the second preset rule have the same waveform.

2. The control method according to claim 1, characterized in that: The step S11 includes: setting the output voltage value u ref And the output voltage value u at the first moment c1 A voltage difference is obtained by performing a difference, and a voltage control calculation and a proportional gain calculation are performed on the voltage difference in sequence to obtain the duty cycle coefficient d.

3. The control method according to claim 2, characterized in that: The output voltage upper limit of the full-bridge three-level DC converter in the two-level mode is When the output voltage value u at the first moment c1 With the output voltage upper limit value u 2LMAX When they are equal, d=1.

4. The control method according to any one of claims 1 to 3, characterized in that: In the first preset rule PWM driving signal, eight switch tubes Q 1～ The duty cycle of the waveform of the PWM drive signal of Q8 is 50%, and the waveforms of the switch tubes Q1 and Q4 are complementary to each other, the waveforms of the switch tubes Q2 and Q3 are complementary to each other, the waveforms of the switch tubes Q5 and Q6 are the same as the waveform of the switch tube Q1, the waveforms of the switch tubes Q7 and Q8 are the same as the waveform of the switch tube Q4, the phase shift control is performed between the switch tubes Q2 and Q4, and the phase shift control is performed between the switch tubes Q3 and Q1; wherein, the time difference between the rising edge of the switch tube Q2 and the rising edge of the switch tube Q4, and the time difference between the rising edge of the switch tube Q3 and the rising edge of the switch tube Q1, and the ratio of half a switching period are 1-d respectively. 2L ; In the PWM driving signal of the second preset rule, the eight switch tubes Q 1～ The duty cycle of the waveform of the PWM drive signal of Q8 is 50%, and the waveforms of the switch tubes Q1 and Q4 are complementary to each other, the waveforms of the switch tubes Q2 and Q3 are complementary to each other, the waveforms of the switch tubes Q5 and Q6 are the same as the waveform of the switch tube Q3, the waveforms of the switch tubes Q7 and Q8 are the same as the waveform of the switch tube Q2, phase shift control is performed between the switch tubes Q1 and Q2, and phase shift control is performed between the switch tubes Q4 and Q3; wherein the time difference between the rising edge of the switch tube Q1 and the rising edge of the switch tube Q2, and the time difference between the rising edge of the switch tube Q4 and the rising edge of the switch tube Q3, and the ratio of half a switching period are 1-d respectively. 3L .

5. A control device for a full-bridge three-level DC converter, the full-bridge three-level DC converter comprising a left bridge arm and a right bridge arm connected in parallel, the left bridge arm comprising a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4 connected in series, and the right bridge arm comprising a switch tube Q5, a switch tube Q6, a switch tube Q7, and a switch tube Q8 connected in series, characterized in that: The control device comprises: The first processing unit is connected to the output end of the full-bridge three-level DC converter to obtain the output voltage of the full-bridge three-level DC converter, and the first processing unit is used to set the output voltage value u ref And the output voltage value u at the first moment c1 , calculate the duty cycle coefficient d, where 0 <d<2; A second processing unit, connected to the first processing unit, is configured to set a control variable according to the duty cycle coefficient d, where: if 0 < d < 1, the control variable is set to d 2L , and d 2L = d; if 1 ≤ d < 2, the control variable is set to d 3L , and d 3L = d - 1; A drive signal generating unit connected to the second processing unit is used to generate eight switch tubes Q according to the control variable 1～ The PWM drive signal of Q8 is input to the full-bridge three-level DC converter, wherein: If the control variable is d 2L The driving signal generating unit generates a PWM driving signal of a first preset rule to control and drive eight switching tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in a two-level mode and outputs an output voltage u at the second moment c2 ,and If the control variable is d 3L The driving signal generating unit generates a PWM driving signal of a second preset rule to control and drive eight switching tubes Q 1～ Q8, so that the full-bridge three-level DC converter operates in the three-level mode and outputs the output voltage u at the second moment c2 ,and The first processing unit converts the output voltage u at the second moment into c2 Replace the output voltage value u at the first moment c1 , recalculate the duty cycle coefficient d, and repeat this cycle until the output voltage u at the second moment is c2 Equal to the set output voltage value u ref ; Among them, V in is the input voltage of the full-bridge three-level DC converter, K is the turns ratio of the transformer in the full-bridge three-level DC converter; when d=1, the PWM drive signal of the first preset rule and the PWM drive signal of the second preset rule have the same waveform.

6. The control device according to claim 5, characterized in that The first processing unit includes a difference calculation module, a voltage control calculation module and a proportional gain calculation module connected in sequence; the difference calculation module sets the output voltage value u ref And the output voltage value u at the first moment c1 The difference is calculated and the calculation result is input into the voltage control calculation module; The voltage control calculation module performs voltage control calculation based on the calculation result of the difference calculation module, and inputs the calculation result into the proportional gain calculation module; The proportional gain calculation module performs proportional gain calculation based on the calculation result of the voltage control calculation module, and inputs the calculation result to the second processing unit.

7. The control device according to claim 6, characterized in that The output voltage upper limit of the full-bridge three-level DC converter in the two-level mode is When the output voltage value u at the first moment c1 With the output voltage upper limit value u 2LMAX When they are equal, the duty cycle coefficient d calculated by the first processing unit is 1.

8. The control device according to claim 5, characterized in that: The second processing unit includes a control variable setting module and a control variable output module that are connected to each other; the control variable setting module receives the duty cycle coefficient d input from the first processing unit, and sets a control variable according to the duty cycle coefficient d, where: when 0 < d < 1, the control variable setting module sets the control variable to d 2L , and d 2L = d; when 1 ≤ d < 2, the control variable setting module sets the control variable to d 3L , and d 3L = d - 1; the control variable output module outputs the control variable set by the control variable setting module to the drive signal generation unit.

9. The control device according to claim 5, characterized in that In the first preset rule PWM driving signal generated by the driving signal generating unit, eight switching tubes Q 1～ The duty cycle of the waveform of the PWM drive signal of Q8 is 50%, and the waveforms of the switch tubes Q1 and Q4 are complementary to each other, the waveforms of the switch tubes Q2 and Q3 are complementary to each other, the waveforms of the switch tubes Q5 and Q6 are the same as the waveform of the switch tube Q1, the waveforms of the switch tubes Q7 and Q8 are the same as the waveform of the switch tube Q4, the phase shift control is performed between the switch tubes Q2 and Q4, and the phase shift control is performed between the switch tubes Q3 and Q1; wherein, the time difference between the rising edge of the switch tube Q2 and the rising edge of the switch tube Q4, and the time difference between the rising edge of the switch tube Q3 and the rising edge of the switch tube Q1, and the ratio of half a switching period are 1-d respectively. 2L ; In the second preset rule PWM driving signal generated by the driving signal generating unit, eight switching tubes Q 1～ The duty cycle of the waveform of the PWM drive signal of Q8 is 50%, and the waveforms of the switch tubes Q1 and Q4 are complementary to each other, the waveforms of the switch tubes Q2 and Q3 are complementary to each other, the waveforms of the switch tubes Q5 and Q6 are the same as the waveform of the switch tube Q3, the waveforms of the switch tubes Q7 and Q8 are the same as the waveform of the switch tube Q2, phase shift control is performed between the switch tubes Q1 and Q2, and phase shift control is performed between the switch tubes Q4 and Q3; wherein the time difference between the rising edge of the switch tube Q1 and the rising edge of the switch tube Q2, and the time difference between the rising edge of the switch tube Q4 and the rising edge of the switch tube Q3, and the ratio of half a switching period are 1-d respectively. 3L .

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the control method of the full-bridge three-level DC converter according to any one of claims 1 to 4 is implemented.

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