A buck-boost bipolar bidirectional input-output converter

Abstract

This invention discloses a buck-boost bipolar bidirectional input / output converter, comprising a first filter capacitor C1, a first circuit unit, an energy storage inductor L, a second circuit unit, and a second filter capacitor C2 connected in sequence. The first circuit unit adopts a half-bridge or full-bridge structure, and the second circuit unit adopts a half-bridge or full-bridge structure. At least one of the first and second circuit units adopts a full-bridge structure, enabling mutual conversion between the bipolar voltages of the first and second circuit units, thus multiplying the voltage variation range on the input and output sides. This invention improves upon the traditional four-switch buck-boost DC-DC converter, achieving stable and adjustable voltage gain by changing the duty cycle while realizing high-frequency, high-efficiency bipolar bidirectional DC-DC conversion, significantly improving the converter's wide-range voltage supply capability.

Description

Technical Field

[0001] This invention relates to the technical field of DC-DC converter topologies, and in particular to a buck-boost bipolar bidirectional input-output converter. Background Technology

[0002] Energy devices such as distributed renewable energy sources and energy storage batteries with DC power output require a larger voltage span and a wider voltage range, leading to an increasing demand for DC-DC converters that can adapt to bipolar voltages and wider voltage ranges. Against the backdrop of global environmental change and the widespread application of new energy sources, bipolar output bidirectional DC-DC converters have shown broad application prospects in areas such as energy storage power supplies and DC power distribution for renewable energy.

[0003] Traditional four-switch buck-boost converters can be used for power applications where the output voltage is less than or equal to or greater than the input voltage, enabling bidirectional energy flow while maintaining the same polarity of the DC voltages on both sides. However, the output voltage of such converters is limited by the unipolar voltage and their own voltage gain range, making it difficult to adapt to the wide voltage requirements of distributed renewable energy and energy storage battery systems. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a buck-boost bipolar bidirectional input-output converter. It improves upon the traditional four-switch buck-boost DC converter, achieving stable and adjustable voltage gain by changing the duty cycle, while realizing high-frequency and high-efficiency bipolar bidirectional DC conversion, and significantly improving the converter's wide voltage range supply capability.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a buck-boost bipolar bidirectional input / output converter, comprising a first filter capacitor C1, a first circuit unit, an energy storage inductor L, a second circuit unit, and a second filter capacitor C2 connected in sequence; the first filter capacitor C1 is connected in parallel to the first circuit unit, the first circuit unit is connected to the second circuit unit through the energy storage inductor L, and the second filter capacitor C2 is connected in parallel to the second circuit unit; the first circuit unit adopts a half-bridge or full-bridge structure, and the second circuit unit adopts a half-bridge or full-bridge structure;

[0006] At least one of the first and second circuit units adopts a full-bridge structure to realize bipolar voltage conversion and bidirectional power flow. Specifically, when power flows from the first circuit unit to the second circuit unit (i.e., power flows in the forward direction), the voltage of the positive or negative polarity on the first circuit unit side can be converted to the voltage of the positive or negative polarity on the second circuit unit side; when power flows from the second circuit unit side to the first circuit unit side (i.e., power flows in the reverse direction), the voltage of the positive or negative polarity on the second circuit unit side can be converted to the voltage of the positive or negative polarity on the first circuit unit side.

[0007] Preferably, the first circuit unit is a half-bridge structure, including switching transistors Q1 and Q2 connected in series.

[0008] Preferably, the first circuit unit is a full-bridge structure, including a first half-bridge composed of series-connected switching transistors Q1 and Q2 and a second half-bridge composed of series-connected switching transistors Q3 and Q4, wherein the first half-bridge and the second half-bridge are connected in parallel.

[0009] Preferably, the second circuit unit is a half-bridge structure, including switching transistors Q5 and Q6 connected in series.

[0010] Preferably, the second circuit unit is a full-bridge structure, including a third half-bridge composed of series-connected switching transistors Q5 and Q6 and a fourth half-bridge composed of series-connected switching transistors Q7 and Q8, wherein the third half-bridge and the fourth half-bridge are connected in parallel.

[0011] Preferably, the switching transistors of the first circuit unit form a Buck unit, and the switching transistors of the second circuit unit form a Boost unit. The midpoints of the first and second circuit units are A and B, respectively, and the duty cycles of the switching transistors Q1, Q2, Q5, and Q6 are defined as D. S1 D S2 D S5 D S6 Analysis of its circuit topology reveals that during steady-state operation of the converter, the average inductor voltage over one switching cycle is zero, meaning the average voltage across inductor L is constant. Therefore:

[0012]

[0013] In the formula, Let A and B be the average voltage values ​​at points A and B, respectively, and express them as follows:

[0014]

[0015]

[0016] In the formula, V g V is the input voltage. oThis refers to the output voltage.

[0017] By simultaneously solving these equations, we can obtain the relationship between the input voltage and the output voltage of the converter, i.e., the gain formula of the converter:

[0018]

[0019] In the formula, M is the gain of the converter.

[0020] Preferably, when the first circuit unit adopts a half-bridge structure and the second circuit unit adopts a full-bridge structure, the following situations apply:

[0021] When power flows in the forward direction, in the first circuit unit, the switching transistors Q1 and Q2 are turned on complementaryly, and the bipolar output of voltage is achieved by controlling the full-bridge circuit in the second circuit unit.

[0022] When the output voltage is positive, the switching transistors Q5 and Q7 conduct complementaryly, the switching transistor Q6 is always on, and the switching transistor Q8 is always off.

[0023] When the output voltage is negative, the switching transistors Q6 and Q8 conduct complementaryly, the switching transistor Q5 is always on, and the switching transistor Q7 is always off.

[0024] When power flows in reverse, in the first circuit unit, the switching transistors Q1 and Q2 are complementary and conduct, outputting a unipolar voltage. By controlling the full-bridge circuit in the second circuit unit, the bipolar input of the voltage is realized.

[0025] When the input voltage is positive, switching transistors Q5 and Q7 conduct complementaryly, switching transistor Q6 is always on, and switching transistor Q8 is always off.

[0026] When the input voltage is negative, switching transistors Q6 and Q8 conduct complementaryly, switching transistor Q5 is always on, and switching transistor Q7 is always off.

[0027] Preferably, when the first circuit unit adopts a full-bridge structure and the second circuit unit adopts a half-bridge structure, the following situations apply:

[0028] When power flows in the forward direction, in the second circuit unit, the switching transistors Q5 and Q6 are complementary and conduct, outputting a unipolar voltage. By controlling the full-bridge circuit in the first circuit unit, the bipolar input of the voltage is achieved.

[0029] When the input voltage is positive, the switching transistors Q1 and Q3 conduct complementaryly, the switching transistor Q4 is always on, and the switching transistor Q2 is always off.

[0030] When the input voltage is negative, switches Q2 and Q4 conduct complementaryly, switch Q3 is always on, and switch Q1 is always off.

[0031] When the power flows in reverse, in the second circuit unit, the switching transistors Q5 and Q6 are turned on complementaryly, and the bipolar output of voltage is achieved by controlling the full-bridge circuit in the second circuit unit.

[0032] When the output voltage is positive, the switching transistors Q1 and Q3 conduct complementaryly, the switching transistor Q4 is always on, and the switching transistor Q2 is always off.

[0033] When the output voltage is negative, the switching transistors Q2 and Q4 conduct complementaryly, the switching transistor Q3 is always on, and the switching transistor Q1 is always off.

[0034] Preferably, when the first circuit unit adopts a full-bridge structure and the second circuit unit adopts a full-bridge structure, the following situations apply:

[0035] When power flows in the forward direction, bipolar voltage input is achieved by controlling the full-bridge circuit in the first circuit unit, and bipolar voltage output is achieved by controlling the full-bridge circuit in the second circuit unit.

[0036] When the input voltage is positive and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q4 and Q6 are always on, and switches Q2 and Q8 are always off.

[0037] When the input voltage is positive and the output voltage is negative, switches Q1 and Q3 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q4 and Q5 are always on, and switches Q2 and Q7 are always off.

[0038] When the input voltage is negative and the output voltage is positive, switches Q2 and Q4 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q3 and Q6 are always on, and switches Q1 and Q8 are always off.

[0039] When the input voltage is negative and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q3 and Q5 are always on, and switches Q1 and Q7 are always off.

[0040] When power flows in reverse, bipolar voltage input is achieved by controlling the full-bridge circuit in the first circuit unit, and bipolar voltage output is achieved by controlling the full-bridge circuit in the second circuit unit.

[0041] When the input voltage is positive and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q4 and Q6 are always on, and switches Q2 and Q8 are always off.

[0042] When the input voltage is positive and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q3 and Q6 are always on, and switches Q1 and Q8 are always off.

[0043] When the input voltage is negative and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q4 and Q5 are always on, and switches Q1 and Q8 are always off.

[0044] When the input voltage is negative and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q3 and Q5 are always on, and switches Q1 and Q7 are always off.

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] 1. At least one of the first circuit unit and the second circuit unit adopts a full-bridge structure, which enables the bipolar voltage of the first circuit unit and the bipolar voltage of the second circuit unit to be mutually converted, multiplying the voltage variation range of the input side and the output side, and is suitable for occasions that require bipolar voltage conversion and wide voltage variation range.

[0047] 2. This invention improves upon the traditional four-switch buck-boost DC-DC converter. By changing the duty cycle, it achieves stable and adjustable voltage gain while realizing high-frequency, high-efficiency bipolar bidirectional DC-DC conversion, significantly improving the converter's wide-range voltage supply capability. Attached Figure Description

[0048] Figure 1 This is a structural framework diagram of the present invention.

[0049] Figure 2 This is a structural framework diagram of the forward power flow in an embodiment of the present invention.

[0050] Figure 3 This is a structural framework diagram of reverse power flow in an embodiment of the present invention.

[0051] Figure 4 This is a structural framework diagram of a first circuit unit provided in an embodiment of the present invention.

[0052] Figure 5 This is a structural framework diagram of a second circuit unit provided in an embodiment of the present invention. Detailed Implementation

[0053] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0054] like Figure 1As shown, this embodiment provides a buck-boost bipolar bidirectional input / output converter, including a first filter capacitor C1, a first circuit unit, an energy storage inductor L, a second circuit unit, and a second filter capacitor C2 connected in sequence; the first filter capacitor C1 is connected in parallel to the first circuit unit, the first circuit unit is connected to the second circuit unit through the energy storage inductor L, and the second filter capacitor C2 is connected in parallel to the second circuit unit; the first circuit unit adopts a half-bridge or full-bridge structure, and the second circuit unit adopts a half-bridge or full-bridge structure;

[0055] At least one of the first and second circuit units adopts a full-bridge structure to achieve bipolar voltage conversion and bidirectional power flow. Specifically, when power flows from the first circuit unit to the second circuit unit (i.e., power flows in the forward direction), the voltage of the positive or negative polarity on the first circuit unit side can be converted to the voltage of the positive or negative polarity on the second circuit unit side; when power flows from the second circuit unit side to the first circuit unit side (i.e., power flows in the reverse direction), the voltage of the positive or negative polarity on the second circuit unit side can be converted to the voltage of the positive or negative polarity on the first circuit unit side.

[0056] The second circuit unit is a full-bridge structure, including a third half-bridge composed of series-connected switching transistors Q5 and Q6, and a fourth half-bridge composed of series-connected switching transistors Q7 and Q8. The third and fourth half-bridges are connected in parallel.

[0057] The switching transistors in the first circuit unit form a Buck unit, and the switching transistors in the second circuit unit form a Boost unit. The midpoints of the first and second circuit units are A and B, respectively. The duty cycles of switching transistors Q1, Q2, Q5, and Q6 are defined as D. S1 D S2 D S5 D S6 Analysis of its circuit topology reveals that during steady-state operation of the converter, the average inductor voltage over one switching cycle is zero, meaning the average voltage across inductor L is constant. Therefore:

[0058]

[0059] In the formula, Let A and B be the average voltage values ​​at points A and B, respectively, and express them as follows:

[0060]

[0061]

[0062] In the formula, V g V is the input voltage. o This refers to the output voltage.

[0063] By simultaneously solving these equations, we can obtain the relationship between the input voltage and the output voltage of the converter, i.e., the gain formula of the converter:

[0064]

[0065] In the formula, M represents the gain of the converter. It can be seen that the converter has two control variables, namely D. S1 and D S3 These features enable the realization of a wide input voltage range for the converter. Furthermore, by replacing the original freewheeling diodes D2 and D3 with switching transistors S2 and S3, the inductor current can flow in reverse, thus achieving soft switching for all switching transistors. In addition, a phase shift angle can be added between the two main control transistors S1 and S3 to further increase the diversity of the converter's control strategies.

[0066] like Figure 2 As shown, when power flows in the forward direction, bipolar voltage input is achieved by controlling the full-bridge circuit in the first circuit unit, and bipolar voltage output is achieved by controlling the full-bridge circuit in the second circuit unit.

[0067] When the input voltage is positive and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q4 and Q6 are always on, and switches Q2 and Q8 are always off.

[0068] When the input voltage is positive and the output voltage is negative, switches Q1 and Q3 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q4 and Q5 are always on, and switches Q2 and Q7 are always off.

[0069] When the input voltage is negative and the output voltage is positive, switches Q2 and Q4 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q3 and Q6 are always on, and switches Q1 and Q8 are always off.

[0070] When the input voltage is negative and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q3 and Q5 are always on, and switches Q1 and Q7 are always off.

[0071] like Figure 3 As shown, when power flows in reverse, bipolar voltage input is achieved by controlling the full-bridge circuit in the first circuit unit, and bipolar voltage output is achieved by controlling the full-bridge circuit in the second circuit unit.

[0072] When the input voltage is positive and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q4 and Q6 are always on, and switches Q2 and Q8 are always off.

[0073] When the input voltage is positive and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q3 and Q6 are always on, and switches Q1 and Q8 are always off.

[0074] When the input voltage is negative and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q4 and Q5 are always on, and switches Q1 and Q8 are always off.

[0075] When the input voltage is negative and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q3 and Q5 are always on, and switches Q1 and Q7 are always off.

[0076] As a preferred embodiment, such as Figure 4 As shown, a first circuit unit structure for another application of the present invention is illustrated. The first circuit unit is a half-bridge structure, including switching transistors Q1 and Q2 connected in series.

[0077] As a preferred embodiment, such as Figure 5 As shown, a first circuit unit structure for another application of the present invention is illustrated. The second circuit unit is a half-bridge structure, including series-connected switching transistors Q5 and Q6.

[0078] In the first and second circuit units, at least one circuit unit adopts a full-bridge structure to realize bipolar voltage conversion and bidirectional power flow.

[0079] The embodiments and descriptions above are merely illustrative of the principles and preferred embodiments of the present invention. Various changes and modifications may be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A buck-boost bipolar bidirectional input / output converter, characterized in that: The circuit includes a first filter capacitor C1, a first circuit unit, an energy storage inductor L, a second circuit unit, and a second filter capacitor C2 connected in sequence. The first filter capacitor C1 is connected in parallel to the first circuit unit, the first circuit unit is connected to the second circuit unit through the energy storage inductor L, and the second filter capacitor C2 is connected in parallel to the second circuit unit. The first circuit unit adopts a half-bridge or full-bridge structure, and the second circuit unit adopts a half-bridge or full-bridge structure. At least one of the first and second circuit units adopts a full-bridge structure to realize bipolar voltage conversion and bidirectional power flow. Specifically, when power flows from the first circuit unit to the second circuit unit (i.e., power flows in the forward direction), the voltage of the positive or negative polarity on the first circuit unit side can be converted to the voltage of the positive or negative polarity on the second circuit unit side; when power flows from the second circuit unit side to the first circuit unit side (i.e., power flows in the reverse direction), the voltage of the positive or negative polarity on the second circuit unit side can be converted to the voltage of the positive or negative polarity on the first circuit unit side. The switching transistors of the first circuit unit form a Buck unit, and the switching transistors of the second circuit unit form a Boost unit. The midpoints of the first and second circuit units are A and B, respectively, and the gain of the converter is controlled by the duty cycle.

2. The buck-boost bipolar bidirectional input / output converter according to claim 1, characterized in that: The first circuit unit is a half-bridge structure, including switching transistors Q1 and Q2 connected in series.

3. A buck-boost bipolar bidirectional input / output converter according to claim 1, characterized in that: The first circuit unit is a full-bridge structure, including a first half-bridge composed of series-connected switching transistors Q1 and Q2 and a second half-bridge composed of series-connected switching transistors Q3 and Q4, with the first and second half-bridges connected in parallel.

4. A buck-boost bipolar bidirectional input / output converter according to claim 1, characterized in that: The second circuit unit is a half-bridge structure, including series-connected switching transistors Q5 and Q6.

5. A buck-boost bipolar bidirectional input / output converter according to claim 1, characterized in that: The second circuit unit is a full-bridge structure, including a third half-bridge composed of series-connected switching transistors Q5 and Q6 and a fourth half-bridge composed of series-connected switching transistors Q7 and Q8, wherein the third half-bridge and the fourth half-bridge are connected in parallel.

6. A buck-boost bipolar bidirectional input / output converter according to any one of claims 1-5, characterized in that: Define the duty cycles of switching transistors Q1, Q2, Q5, and Q6 as D. S1 D S2 D S5 D S6 Analysis of its circuit topology reveals that during steady-state operation of the converter, the average inductor voltage over one switching cycle is zero, meaning the average voltage across inductor L is constant. Therefore: ； In the formula, , Let A and B be the average voltage values ​​at points A and B, respectively, and express them as follows: ； ； In the formula, Input voltage, This refers to the output voltage. By simultaneously solving these equations, we can obtain the relationship between the input voltage and the output voltage of the converter, i.e., the gain formula of the converter: ； In the formula, This represents the gain of the converter.

7. A buck-boost bipolar bidirectional input / output converter according to any one of claims 1-5, characterized in that: When the first circuit unit adopts a half-bridge structure and the second circuit unit adopts a full-bridge structure, the following situations apply: When power flows in the forward direction, in the first circuit unit, the switching transistors Q1 and Q2 are turned on complementaryly, and the bipolar output of voltage is achieved by controlling the full-bridge circuit in the second circuit unit. When the output voltage is positive, the switching transistors Q5 and Q7 conduct complementaryly, the switching transistor Q6 is always on, and the switching transistor Q8 is always off. When the output voltage is negative, the switching transistors Q6 and Q8 conduct complementaryly, the switching transistor Q5 is always on, and the switching transistor Q7 is always off. When power flows in reverse, in the first circuit unit, the switching transistors Q1 and Q2 are complementary and conduct, outputting a unipolar voltage. By controlling the full-bridge circuit in the second circuit unit, the bipolar input of the voltage is realized. When the input voltage is positive, switching transistors Q5 and Q7 conduct complementaryly, switching transistor Q6 is always on, and switching transistor Q8 is always off. When the input voltage is negative, switching transistors Q6 and Q8 conduct complementaryly, switching transistor Q5 is always on, and switching transistor Q7 is always off.

8. A buck-boost bipolar bidirectional input / output converter according to any one of claims 1-5, characterized in that: When the first circuit unit adopts a full-bridge structure and the second circuit unit adopts a half-bridge structure, the following situations apply: When power flows in the forward direction, in the second circuit unit, the switching transistors Q5 and Q6 are complementary and conduct, outputting a unipolar voltage. By controlling the full-bridge circuit in the first circuit unit, the bipolar input of the voltage is achieved. When the input voltage is positive, the switching transistors Q1 and Q3 conduct complementaryly, the switching transistor Q4 is always on, and the switching transistor Q2 is always off. When the input voltage is negative, switches Q2 and Q4 conduct complementaryly, switch Q3 is always on, and switch Q1 is always off. When the power flows in reverse, in the second circuit unit, the switching transistors Q5 and Q6 are turned on complementaryly, and the bipolar output of voltage is achieved by controlling the full-bridge circuit in the second circuit unit. When the output voltage is positive, the switching transistors Q1 and Q3 conduct complementaryly, the switching transistor Q4 is always on, and the switching transistor Q2 is always off. When the output voltage is negative, the switching transistors Q2 and Q4 conduct complementaryly, the switching transistor Q3 is always on, and the switching transistor Q1 is always off.

9. A buck-boost bipolar bidirectional input / output converter according to any one of claims 1-5, characterized in that: When both the first circuit unit and the second circuit unit adopt a full-bridge structure, the following situations apply: When power flows in the forward direction, bipolar voltage input is achieved by controlling the full-bridge circuit in the first circuit unit, and bipolar voltage output is achieved by controlling the full-bridge circuit in the second circuit unit. When the input voltage is positive and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q4 and Q6 are always on, and switches Q2 and Q8 are always off. When the input voltage is positive and the output voltage is negative, switches Q1 and Q3 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q4 and Q5 are always on, and switches Q2 and Q7 are always off. When the input voltage is negative and the output voltage is positive, switches Q2 and Q4 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q3 and Q6 are always on, and switches Q1 and Q8 are always off. When the input voltage is negative and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q3 and Q5 are always on, and switches Q1 and Q7 are always off. When power flows in reverse, bipolar voltage input is achieved by controlling the full-bridge circuit in the first circuit unit, and bipolar voltage output is achieved by controlling the full-bridge circuit in the second circuit unit. When the input voltage is positive and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q4 and Q6 are always on, and switches Q2 and Q8 are always off. When the input voltage is positive and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q5 and Q7 conduct complementaryly, switches Q3 and Q6 are always on, and switches Q1 and Q8 are always off. When the input voltage is negative and the output voltage is positive, switches Q1 and Q3 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q4 and Q5 are always on, and switches Q1 and Q8 are always off. When the input voltage is negative and the output voltage is negative, switches Q2 and Q4 conduct complementaryly, switches Q6 and Q8 conduct complementaryly, switches Q3 and Q5 are always on, and switches Q1 and Q7 are always off.

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