A bidirectional buck-boost DC converter control method based on duty cycle compensation

Abstract

The present invention discloses a bidirectional buck-boost DC converter control method based on duty cycle compensation, relating to the field of power electronics technology. The method comprises: when the bidirectional buck-boost DC converter operates in either the buck-boost mode or the boost mode, based on a traditional phase-shift modulation strategy, positively compensating the duty cycle of the conducting switch on the input side of the H-type bridge arm and negatively compensating the duty cycle of the conducting switch on the output side of the H-type bridge arm, thereby reducing the inductor current ripple during converter operation and simultaneously improving the converter's overall power density. This method has promising application and development prospects for the energy storage link of distributed power generation systems of renewable energy sources such as solar and wind power.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to a bidirectional buck-boost DC converter control method based on duty cycle compensation. Background Art

[0002] Energy storage is a crucial component of photovoltaic and wind power generation systems. Energy storage batteries, used in conjunction with renewable energy, can align renewable energy generation with grid demand in terms of timing and intensity, reducing the randomness of renewable energy generation, minimizing voltage fluctuations in DC microgrids, and improving power generation quality. The energy storage medium is typically connected to the high-voltage busbar via a bidirectional DC / DC converter, enabling bidirectional energy flow between the storage medium and the DC busbar, enabling control and efficient utilization of energy in the system.

[0003] Currently, commonly used bidirectional DC / DC power converters can be divided into two types: isolated and non-isolated topologies, depending on whether there is electrical isolation between the input and output. Non-isolated bidirectional power converters overcome the bulky and low system efficiency drawbacks of isolated topologies and are therefore commonly used in energy storage systems. Flying capacitor bidirectional buck-boost DC / DC converters reduce switching transistor voltage stress, increase power density, and have a wider range of applications. However, the current ripple of these converters under traditional modulation strategies is still large, which can reduce converter performance. Summary of the Invention

[0004] In response to the above problems and technical requirements, the inventors have proposed a bidirectional buck-boost DC converter control method based on duty cycle compensation. The technical solution of the present invention is as follows:

[0005] A method for controlling a bidirectional buck-boost DC converter based on duty cycle compensation, wherein the bidirectional buck-boost DC converter includes an H-shaped bridge arm, and the method comprises the following steps:

[0006] When the bidirectional buck-boost DC converter operates in both the boost and buck modes of the buck-boost mode, based on the traditional phase-shift modulation strategy, positive compensation is performed on the duty cycle of the conduction switch tube on the input side of the H-type bridge arm, and negative compensation is performed on the duty cycle of the conduction switch tube on the output side of the H-type bridge arm to reduce the inductor current ripple.

[0007] A further technical solution is that the expression for positive and negative compensation of the duty cycle is:

[0008]

[0009] Among them, d1 is the duty cycle after positive compensation on the input side, recorded as the first duty cycle; d2 is the duty cycle after negative compensation on the output side, recorded as the second duty cycle; d bis the duty cycle of the first switch tube on the input side of the H-type bridge arm, which serves as the reference duty cycle; λ is the compensation duty cycle.

[0010] A further technical solution is that the method further comprises:

[0011] According to the voltage gain and the first and second duty cycles of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, the relationship between the voltage gain and the upper and lower limits of the duty cycle and the compensation duty cycle is obtained.

[0012] Plan the voltage gain range based on the terminal voltage of the bidirectional buck-boost DC converter;

[0013] Under the duty cycle linear control law, the relationship 1 of the voltage gain and the planning range are combined to obtain the upper and lower limits of the duty cycle, the relationship 2 of the compensation duty cycle and the voltage on both sides of the bidirectional buck-boost DC converter;

[0014] The adjustment range of the compensation duty cycle is determined according to the second relationship and the predetermined conditions.

[0015] A further technical solution is that the method for obtaining the relationship 1 includes:

[0016] By setting the upper and lower limits of the duty cycle and substituting the voltage gain of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy into the expressions of the first and second duty cycles, we obtain:

[0017]

[0018] Among them, D max and D min are the upper and lower limits of the duty cycle respectively;

[0019] β is the voltage gain of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, and its expression is:

[0020] After finishing, we can get:

[0021] A further technical solution is to plan the range of voltage gain according to the terminal voltage of the bidirectional buck-boost DC converter, which is expressed as:

[0022]

[0023] Among them, V 1min and V 1max are the minimum and maximum terminal voltages on the input side of the bidirectional buck-boost DC converter respectively; V2 is the terminal voltage on the output side of the bidirectional buck-boost DC converter.

[0024] A further technical solution is that the expression of relation 2 is:

[0025]

[0026] Among them, D max and D min are the upper and lower limits of the duty cycle respectively; V 1min and V 1max are the minimum and maximum terminal voltages on the input side of the bidirectional buck-boost DC converter respectively; V2 is the terminal voltage on the output side of the bidirectional buck-boost DC converter.

[0027] A further technical solution is to determine the adjustment range of the compensation duty cycle according to the second relationship and predetermined conditions, including:

[0028] Arranging the relationship 2, the adjustment range of the compensation duty cycle is obtained as follows:

[0029]

[0030] The left side of the second inequality satisfies the predetermined condition that the maximum value of the compensation duty cycle is less than the duty cycle of the flying capacitor voltage, so as to ensure that the flying capacitor voltage is half of the input side terminal voltage.

[0031] A further technical solution is that the method further comprises:

[0032] The expression of the average value of the inductor current before and after duty cycle compensation is:

[0033]

[0034] Among them, I L is the average value of the inductor current before duty cycle compensation, I L_C is the average value of the inductor current after duty cycle compensation, P s is the input power of the bidirectional buck-boost DC converter, V1 is the terminal voltage on the input side of the bidirectional buck-boost DC converter, d b is the reference duty cycle, λ is the compensation duty cycle;

[0035] Divide the average values ​​of the inductor current before and after duty cycle compensation to obtain the ratio:

[0036]

[0037] If the ratio of the average values ​​of the inductor current before and after duty cycle compensation is greater than 1, it indicates that under the same input power, the average value of the inductor current is reduced after duty cycle compensation, thereby confirming that the inductor current ripple is reduced after compensation.

[0038] A further technical solution is that the method further comprises:

[0039] Determine the circuit state equations and corresponding operating times of the bidirectional buck-boost DC converter after duty cycle compensation in the boost and buck modes of the buck-boost mode;

[0040] Combining the circuit state equations of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, the voltage gain of the bidirectional buck-boost DC converter after duty cycle compensation is obtained as follows:

[0041]

[0042] Among them, V2 is the terminal voltage on the output side of the bidirectional buck-boost DC converter, V1 is the terminal voltage on the input side of the bidirectional buck-boost DC converter, d b is the reference duty cycle, and λ is the compensation duty cycle.

[0043] A further technical solution is that the two opposite bridge arms in the H-shaped bridge arm are respectively a first bridge arm and a second bridge arm, and the first bridge arm and the second bridge arm each include first to fourth switching tubes connected in series in sequence, and the first bridge arm is set as the input side and the second bridge arm is set as the output side;

[0044] The method also includes, after performing positive and negative compensation on the duty cycle:

[0045] When the bidirectional buck-boost DC converter operates in the boost mode of the buck-boost mode, two additional operating states are added compared to the operating state of the traditional phase-shift modulation strategy, namely:

[0046] State 1 after compensation: the first and second switching tubes of the first bridge arm are turned on, the fourth switching tube of the second bridge arm is turned on, and the second switching tube of the second bridge arm is turned on in freewheeling mode;

[0047] State 2 after compensation: the first and second switching tubes of the first bridge arm are turned on, the third switching tube of the second bridge arm is turned on, and the first switching tube of the second bridge arm is turned on in freewheeling mode;

[0048] When the bidirectional buck-boost DC converter operates in the buck mode of the buck-boost mode, two additional working states are added compared to the working state of the traditional phase-shift modulation strategy, namely:

[0049] State three after compensation: the first switch tube of the first bridge arm is turned on, the third switch tube of the first bridge arm and the first and second switch tubes of the second bridge arm are turned on in freewheeling mode;

[0050] State 4 after compensation: the second switch tube of the first bridge arm is turned on, and the fourth switch tube of the first bridge arm and the first and second switch tubes of the second bridge arm are turned on in freewheeling mode.

[0051] The beneficial technical effects of the present invention are:

[0052] Based on the traditional phase-shift modulation strategy of the flying capacitor bidirectional buck-boost DC converter, the duty cycle of the conduction switch tube on the input side of the H-type bridge arm is positively compensated, and the duty cycle of the conduction switch tube on the output side of the H-type bridge arm is negatively compensated, thereby increasing the working state of the converter; under the same power, the average value of the inductor current is reduced after the duty cycle compensation, which is more beneficial to improving the system power density; and the present application also provides an adjustment range of the compensation duty cycle, and satisfies the maximum value of the compensation duty cycle to be less than the duty cycle of the flying capacitor voltage, so as to ensure that the flying capacitor voltage has a certain adjustment capability and is half of the input side terminal voltage; the use of the control method proposed in the present application has good application and development prospects for the energy storage link of distributed power generation systems of new energy such as light and wind. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a circuit diagram of a flying capacitor bidirectional buck-boost DC converter provided by this application.

[0054] Figure 2 This is a driving and current pulsation signal diagram provided by the present application under the traditional phase-shift modulation strategy applied to the flying capacitor bidirectional buck-boost DC converter.

[0055] Figure 3 This is the equivalent circuit state diagram of the flying capacitor bidirectional buck-boost DC converter provided by this application under the traditional phase-shift modulation strategy.

[0056] Figure 4 This is a flow chart of a bidirectional buck-boost DC converter control method based on duty cycle compensation provided in this application.

[0057] Figure 5 This is a diagram of a driving square wave signal after duty cycle compensation provided by this application.

[0058] Figure 6 This is the circuit state diagram added after the duty cycle compensation provided by this application.

[0059] Figure 7 This is a comparison diagram of the average inductor current before and after the compensation duty cycle is added to the converter provided by this application. DETAILED DESCRIPTION

[0060] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0061] like Figure 1 As shown, a flying capacitor bidirectional buck-boost DC converter includes: an H-type bridge arm, a filter inductor L, a resistor R L , two flying capacitors C f1 and C f2, two filter capacitors C1 and C2. The two opposite bridge arms in the H-shaped bridge arm are the first bridge arm and the second bridge arm, and the first bridge arm includes the first to fourth switching tubes S in series. 11 -S 14 The second bridge arm includes the first to fourth switch tubes S in series. 21 -S 24 , the connecting bridge arm in the H-type bridge arm has a series filter inductor L and a resistor R L Since the specific connection method of the H-type bridge arm switch tube is well known to those skilled in the art, it will not be described in detail here. f1 The positive terminal is connected to the first switch tube S of the first bridge arm 11 and the second switch tube S 12 The negative terminal is connected to the third switch tube S in the first bridge arm. 13 and the fourth switch tube S 14 Similarly, another flying capacitor C f2 The two ends are respectively connected between the first and second switch tubes of the second bridge arm and between the third and fourth switch tubes. 11 The upper end of the fourth switch tube S 14 The first filter capacitor C1 is connected in parallel between the lower ends of the first bridge arm and the upper end S of the first switch tube of the first bridge arm. 11 With the fourth switch tube S 14 A terminal voltage V1 is also formed between the lower ends of the first switch tube S 11 The upper end of the terminal voltage V1 is used as the positive electrode. The first switch tube S of the second bridge arm 21 The upper end of the fourth switch tube S 24 A second filter capacitor C2 is connected in parallel between the lower ends of the bridge and the first switch tube S of the second bridge arm. 21 The upper end of the fourth switch tube S 24 A terminal voltage V2 is also formed between the lower ends of the first switch tube S 21 The upper end of the fourth switch tube S of the first bridge arm is used as the positive electrode of the terminal voltage V2. 14 The lower end of the fourth switch tube S of the second bridge arm 24 The lower end is connected.

[0062] like Figure 2 As shown, when the DC converter operates in the boost and buck modes of the buck-boost mode, the conventional phase-shift modulation strategy is adopted. The DC converter has four working states in the full range of duty cycles (i.e., 0-1), as shown in FIG. Figure 3 As shown. Among them, the traditional phase shift modulation strategy is: the first switch tube S of the first bridge arm 11 The driving signal of the first bridge arm and the second switch tube S 12 The driving signal of the first bridge arm is phase-shifted by 180°, and the first switch tube S 11The driving signal of the fourth switch tube S of the second bridge arm 24 The driving signal of the second switch tube S of the first bridge arm is the same. 12 The driving signal of the third switch tube S of the second bridge arm 23 The driving signal is the same.

[0063] This application adds a duty cycle compensation strategy based on the traditional phase-shift modulation strategy to further reduce the inductor current ripple and improve the system power density. Taking the DC converter transferring energy from left to right as an example, the first bridge arm is the input side and the second bridge arm is the output side, and a bidirectional buck-boost DC converter control method based on duty cycle compensation is provided. Figure 4 Specifically, it includes the following contents:

[0064] S1. When the bidirectional buck-boost DC converter operates in the buck-boost mode and the buck-boost mode, based on the traditional phase-shift modulation strategy, the duty cycle of the conducting switch tube of the first bridge arm of the H-type bridge arm is positively compensated, and the duty cycle of the conducting switch tube of the second bridge arm of the H-type bridge arm is negatively compensated. The expression is:

[0065]

[0066] Among them, d1 is the duty cycle after positive compensation on the input side, recorded as the first duty cycle; d2 is the duty cycle after negative compensation on the output side, recorded as the second duty cycle; d b The first switch tube (also known as S 11 ) is used as the reference duty cycle; λ is the compensation duty cycle.

[0067] S2, two triangular carriers T with a phase interval of 180° ri1 and T ri2 The first duty cycle d1, the second duty cycle d2 and the reference duty cycle d b The modulation wave is compared with that of the bidirectional buck-boost DC converter to obtain the switching tube S on the input and output sides of the H-type bridge arm in the boost and buck modes of the buck-boost mode. 11 、S 12 、S 23 、S 24 The driving square wave signal is Figure 5 shown.

[0068] S3. Analyze the working states of the DC converter in the step-up and step-down modes to obtain the voltage gain of the bidirectional step-up and step-down DC converter after duty cycle compensation.

[0069] After the duty cycle is compensated, the DC converter works in the boost mode of the buck-boost mode, that is, d bWhen >0.5, two more working states are added compared with the working state of the traditional phase shift modulation strategy, namely:

[0070] State 1 after compensation: the first and second switch tubes S of the first bridge arm 11 and S 12 The fourth switch tube S of the second bridge arm is turned on. 24 The second switch tube D of the second bridge arm is turned on. 22 Freewheeling conduction, such as Figure 6 As shown in (a).

[0071] State 2 after compensation: the first and second switch tubes S of the first bridge arm 11 and S 12 The third switch tube S of the second bridge arm is turned on. 23 The first switch tube D of the second bridge arm is turned on. 21 Freewheeling conduction, such as Figure 6 (b) shown.

[0072] When the bidirectional buck-boost DC converter works in the buck mode of the buck-boost mode, that is, d b When <0.5, two more working states are added compared with the working state of the traditional phase-shift modulation strategy, namely:

[0073] State 3 after compensation: the first switch tube S of the first bridge arm 11 The third switch tube D of the first bridge arm is turned on. 13 and the first and second switch tubes D of the second bridge arm 21 、D 22 Freewheeling conduction, such as Figure 6 (c) shown.

[0074] State 4 after compensation: the second switch tube S of the first bridge arm 12 The fourth switch tube D of the first bridge arm is turned on. 14 and the first and second switch tubes D of the second bridge arm 21 、D 22 Freewheeling conduction, such as Figure 6 (d) shown.

[0075] Determine the circuit state equations and corresponding operating times of the bidirectional buck-boost DC converter after duty cycle compensation in the boost and buck modes of the buck-boost mode, including:

[0076] By analyzing the circuit of the converter, the state equation of the added circuit can be expressed as:

[0077]

[0078] Among them, V f1 and V f2 There are two flying capacitors Cf1 and C f2 voltage.

[0079] right Figure 5 By performing duty cycle time analysis, the circuit state and its operating time in the entire cycle are obtained as shown in Table 1. The operating time is obtained by adding or subtracting λ from the operating time corresponding to the original operating state.

[0080] Table 1 Duty cycle phase shift compensation circuit status

[0081]

[0082] Combining the circuit state equations of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, as shown in Equation (3), the voltage gain of the bidirectional buck-boost DC converter after duty cycle compensation is obtained, as shown in Equation (4).

[0083]

[0084]

[0085] S4. Under the predetermined conditions, the adjustment range of the compensation duty cycle is designed, including:

[0086] S41. According to the voltage gain and the first and second duty cycles of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, obtain a relationship between the voltage gain, the upper and lower limits of the duty cycle, and the compensation duty cycle.

[0087] In actual systems, to avoid the occurrence of narrow pulses, the duty cycle is usually set to an upper limit D max and the lower limit D min Substituting the voltage gain of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy into the equations (1) for the first and second duty cycles, we obtain:

[0088]

[0089] Where β is the voltage gain of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, and its expression is:

[0090] Arranging formula (5) yields:

[0091] S42. Plan the voltage gain range based on the terminal voltage of the bidirectional buck-boost DC converter. The expression is:

[0092]

[0093] Among them, V 1min and V 1maxare the minimum and maximum terminal voltages on the input side of the bidirectional buck-boost DC converter, respectively.

[0094] S43. Under the duty cycle linear control law, the voltage gain relationship (6) and the planning range (7) are combined to obtain the relationship between the upper and lower limits of the duty cycle, the compensation duty cycle and the voltage on both sides of the bidirectional buck-boost DC converter. The expression is:

[0095]

[0096] S44. Determine the adjustment range of the compensation duty cycle according to equation (8) and predetermined conditions.

[0097] Arranging the relationship 2, the adjustment range of the compensation duty cycle is obtained as follows:

[0098]

[0099] In practical systems, the flying capacitor voltage must be independently controlled to ensure that it is always half the input-side voltage V1, allowing the converter to operate in three-level mode. Therefore, the left side of the second inequality in equation (9) satisfies the predetermined condition that the maximum compensation duty cycle is less than the duty cycle of the flying capacitor voltage, ensuring that the flying capacitor voltage has a certain degree of regulation capability.

[0100] S5. Verify the inductor current ripple state after duty cycle compensation.

[0101] When energy is transferred from V1 to V2, the input power of the DC converter is controlled by the switch tube of the first bridge arm. Let the input power be P s , the expression of the average value of the inductor current before and after duty cycle compensation is:

[0102]

[0103] Among them, I L is the average value of the inductor current before duty cycle compensation, I L_C is the average value of the inductor current after duty cycle compensation.

[0104] Divide the average values ​​of the inductor current before and after duty cycle compensation to obtain the ratio:

[0105]

[0106] This example gives two ways to compensate for the duty cycle λ. L with I L_C The numerical relationship of Figure 7As shown in the figure, it can be seen that the ratio of the average value of the inductor current before and after duty cycle compensation is greater than 1, indicating that under the same input power, the average value of the inductor current after duty cycle compensation is reduced, thereby confirming that the inductor current ripple after compensation is reduced, which is more beneficial to improving the system power density. The control method proposed in this application has good application and development prospects for the energy storage link of distributed power generation systems of new energy sources such as light and wind.

[0107] The above description is only a preferred embodiment of the present application, and the present invention is not limited to the above embodiment. It is understood that other improvements and variations directly derived or imagined by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the scope of protection of the present invention.

Claims

1. A control method for a bidirectional buck-boost DC converter based on duty cycle compensation, wherein the bidirectional buck-boost DC converter includes an H-shaped bridge arm, characterized in that: The method comprises: When the bidirectional buck-boost DC converter operates in the buck-boost mode and the buck-boost mode, based on the traditional phase-shift modulation strategy, positive compensation is performed on the duty cycle of the conducting switch tube on the input side of the H-shaped bridge arm, and negative compensation is performed on the duty cycle of the conducting switch tube on the output side of the H-shaped bridge arm, so as to reduce the inductor current ripple; Among them, the expression for positive and negative compensation of duty cycle is: Among them, d1 is the duty cycle after positive compensation on the input side, recorded as the first duty cycle; d2 is the duty cycle after negative compensation on the output side, recorded as the second duty cycle; d b is the duty cycle of the first switch tube on the input side of the H-type bridge arm, which serves as the reference duty cycle; λ is the compensation duty cycle.

2. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to claim 1, characterized in that: The method further comprises: According to the voltage gain and the first and second duty cycles of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, a relationship between the voltage gain, the upper and lower limits of the duty cycle, and the compensation duty cycle is obtained; Planning the range of the voltage gain according to the terminal voltage of the bidirectional buck-boost DC converter; Under the duty cycle linear control law, the first relationship of the voltage gain and the planning range are combined to obtain the upper and lower limits of the duty cycle, the second relationship between the compensation duty cycle and the voltage on both sides of the bidirectional buck-boost DC converter; The adjustment range of the compensation duty cycle is determined according to the second relationship and a predetermined condition.

3. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to claim 2, characterized in that: Methods for obtaining the first relationship include: By setting the upper and lower limits of the duty cycle, substituting the voltage gain of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy into the expressions of the first and second duty cycles, we obtain: Among them, D max and D min are the upper and lower limits of the duty cycle respectively; β is the voltage gain of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, and its expression is: After finishing, we can get:

4. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to claim 2, characterized in that: The voltage gain range is planned according to the terminal voltage of the bidirectional buck-boost DC converter, and the expression is: Among them, V 1min and V 1max are the minimum and maximum values ​​of the terminal voltage on the input side of the bidirectional buck-boost DC converter respectively; V2 is the terminal voltage on the output side of the bidirectional buck-boost DC converter.

5. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to claim 2, characterized in that: The expression of the second relation is: Among them, D max and D min are the upper and lower limits of the duty cycle respectively; V 1min and V 1max are the minimum and maximum terminal voltages on the input side of the bidirectional buck-boost DC converter respectively; V2 is the terminal voltage on the output side of the bidirectional buck-boost DC converter.

6. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to claim 5, characterized in that: The determining the adjustment range of the compensation duty cycle according to the second relationship and a predetermined condition includes: Arranging the second relationship, the adjustment range of the compensation duty cycle is obtained as follows: The left side of the second inequality satisfies the predetermined condition that: the maximum value of the compensation duty cycle is less than the duty cycle of the flying capacitor voltage, so as to ensure that the flying capacitor voltage is half of the input side terminal voltage.

7. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to any one of claims 1 to 6, characterized in that: The method further comprises: The expression of the average value of the inductor current before and after duty cycle compensation is: Among them, I L is the average value of the inductor current before duty cycle compensation, I L_C is the average value of the inductor current after duty cycle compensation, P s is the input power of the bidirectional buck-boost DC converter, V1 is the terminal voltage on the input side of the bidirectional buck-boost DC converter, d b is the reference duty cycle, λ is the compensation duty cycle; Dividing the average values ​​of the inductor current before and after duty cycle compensation, the ratio formula is: If the ratio of the average values ​​of the inductor current before and after the duty cycle compensation is greater than 1, it indicates that under the same input power, the average value of the inductor current is reduced after the duty cycle compensation, thereby determining that the inductor current ripple is reduced after compensation.

8. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to any one of claims 1 to 6, characterized in that: The method further comprises: Determining the circuit state equations and corresponding operating times of the bidirectional buck-boost DC converter after duty cycle compensation in the boost and buck modes of the buck-boost mode respectively; Combining the circuit state equations of the bidirectional buck-boost DC converter under the traditional phase-shift modulation strategy, the voltage gain of the bidirectional buck-boost DC converter after duty cycle compensation is obtained as follows: Among them, V2 is the terminal voltage on the output side of the bidirectional buck-boost DC converter, V1 is the terminal voltage on the input side of the bidirectional buck-boost DC converter, d b is the reference duty cycle, and λ is the compensation duty cycle.

9. The bidirectional buck-boost DC converter control method based on duty cycle compensation according to any one of claims 1 to 6, characterized in that: The two opposite bridge arms in the H-shaped bridge arm are respectively a first bridge arm and a second bridge arm, wherein the first bridge arm and the second bridge arm each include first to fourth switching transistors connected in series in sequence, and the first bridge arm is assumed to be the input side and the second bridge arm is assumed to be the output side; The method further includes, after performing positive and negative compensation on the duty cycle: When the bidirectional buck-boost DC converter operates in the boost mode of the buck-boost mode, two additional operating states are added compared to the operating state of the traditional phase-shift modulation strategy, namely: State 1 after compensation: the first and second switching tubes of the first bridge arm are turned on, the fourth switching tube of the second bridge arm is turned on, and the second switching tube of the second bridge arm is turned on in freewheeling mode; State 2 after compensation: the first and second switching tubes of the first bridge arm are turned on, the third switching tube of the second bridge arm is turned on, and the first switching tube of the second bridge arm is turned on in freewheeling mode; When the bidirectional buck-boost DC converter operates in the buck mode of the buck-boost mode, two additional working states are added compared to the working state of the traditional phase-shift modulation strategy, namely: State three after compensation: the first switch tube of the first bridge arm is turned on, and the third switch tube of the first bridge arm and the first and second switch tubes of the second bridge arm are turned on in freewheeling mode; State four after compensation: the second switch tube of the first bridge arm is turned on, and the fourth switch tube of the first bridge arm and the first and second switch tubes of the second bridge arm are turned on in freewheeling mode.

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