High-gain low-ripple DC-DC converter based on coupling inductor and control method

Abstract

The invention relates to a high-gain low-ripple DC-DC converter based on a coupling inductor and a control method. A topological structure of the high-gain low-ripple DC-DC converter comprises an interleaved Boost circuit and an H-bridge auxiliary boost circuit, the interleaving Boost circuit comprises a first coupling inductor, a second coupling inductor, a first switching tube branch and a second switching tube branch. One end of the first coupling inductor and one end of the second coupling inductor are connected in parallel and then connected with an input voltage source, and the first switching tube branch and the second switching tube branch are connected in parallel and then serve as the output end of the interleaved Boost circuit; primary sides of the first coupling inductor and the second coupling inductor are used as filter inductors of the interleaved Boost circuit, secondary sides of the first coupling inductor are connected in series in an anti-phase manner and then are connected with the H-bridge auxiliary boost circuit, and an output end of the H-bridge auxiliary boost circuit is connected with an output end of the interleaved Boost circuit in series and superposed and then is connected with a load. The method can be widely applied to the new energy fields of fuel cells, photovoltaics and the like.

Description

Technical Field

[0001] The invention relates to a high-gain low-ripple DC-DC converter based on coupled inductors and a control method thereof, and belongs to the field of new energy such as fuel cells and photovoltaics. Background Art

[0002] The output voltage of renewable energy sources such as fuel cells and photovoltaics is low and unstable, and requires a DC-DC converter with higher gain to connect to a stable high-voltage DC bus.

[0003] like Figure 1 As shown in the figure, the most commonly used topology is the interleaved parallel Boost converter solution, which consists of two Boost converter branches with a phase stagger of 180°. In each branch, there is an inductor, a switch tube and a diode. This solution achieves voltage gain by adjusting the duty cycle of the switch tube.

[0004] Since the input current of the Boost circuit is generally in continuous mode, the current of the switch tube is usually large when it is turned on, resulting in large switching losses and reducing the efficiency of the system. At the same time, the theoretical voltage gain of the Boost circuit is 1 / (1-D), where D is the duty cycle of the switch tube. In theory, an infinite gain can be achieved. However, due to the presence of parasitic parameters, the actual Boost circuit cannot achieve a higher gain. In addition, at high gain, due to the long conduction time of the switch tube, the conduction loss is large, and the converter efficiency is low. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a high-gain, low-ripple DC-DC converter and control method based on coupled inductors, which can ensure that the switch tube is turned on at zero voltage. At the same time, coupled inductor technology is adopted to improve the gain of the converter.

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

[0007] In a first aspect, the present invention provides a high-gain, low-ripple DC-DC converter based on coupled inductors, whose topology structure includes: an interleaved parallel Boost circuit and an H-bridge auxiliary boost circuit; the interleaved parallel Boost circuit includes a first Boost branch and a second Boost branch; the first Boost branch includes a first coupled inductor and a first switch tube branch, and the second Boost branch includes a second coupled inductor and a second switch tube branch; one end of the first coupled inductor and the second coupled inductor are connected in parallel and connected to an input voltage source, and the first switch tube branch and the second switch tube branch are connected in parallel as the output end of the interleaved parallel Boost circuit; the primary sides of the first coupled inductor and the second coupled inductor serve as the filter inductor of the interleaved parallel Boost circuit, the secondary sides of the first coupled inductor and the second coupled inductor are connected in anti-phase series and coupled to the H-bridge auxiliary boost circuit, and the output side of the interleaved parallel Boost circuit is connected in series with the H-bridge auxiliary boost circuit and then connected to a load.

[0008] Further, the first switch branch includes a first upper switch tube and a first lower switch tube, and the second switch branch includes a second upper switch tube and a second lower switch tube;

[0009] After the source terminal of the first upper switch tube and the drain terminal of the first lower switch tube are connected in series, the connection point is connected to the other end of the primary side of the first coupling inductor;

[0010] The source terminal of the second upper switch tube and the drain terminal of the second lower switch tube are connected in series, and the connection point is connected to the other end of the primary side of the second coupling inductor;

[0011] The drain terminal of the first upper switch tube and the drain terminal of the second upper switch tube are connected in parallel and then connected to one end of the output capacitor;

[0012] The source terminal of the first lower switch tube and the source terminal of the second lower switch tube are connected in parallel to the other end of the output capacitor, and the two ends of the output capacitor serve as the output ends of the staggered parallel Boost circuit.

[0013] Further, the H-bridge auxiliary boost circuit includes a first rectifying branch and a second rectifying branch arranged in parallel;

[0014] The first rectifying branch is provided with two first rectifying devices connected in series, and the connection point of the two first rectifying devices is connected to one end of the secondary side of the first coupled inductor as a midpoint of the H-bridge auxiliary boost circuit;

[0015] The second rectifying branch is provided with two second rectifying devices connected in series, and the connection point of the two second rectifying devices is connected to one end of the secondary side of the second coupled inductor as another midpoint of the H-bridge auxiliary boost circuit, and the secondary side of the first coupled inductor is connected in reverse series with the other end of the secondary side of the second coupled inductor.

[0016] Furthermore, the first rectifying device and the second rectifying device are diodes or switch devices.

[0017] Furthermore, the switch device is a MOSFET or an IGBT device.

[0018] In a second aspect, the present invention provides a control method for a high-gain, low-ripple DC-DC converter based on a coupled inductor, comprising the following steps:

[0019] Collect current and voltage data;

[0020] Based on the collected current and voltage data, the basic duty cycle and duty cycle variation of the interleaved parallel Boost circuit are calculated;

[0021] The interleaved parallel Boost circuit is controlled based on the basic duty cycle and the duty cycle variation.

[0022] Further, the basic duty cycle and duty cycle variation of the staggered parallel Boost circuit are calculated based on the collected current and voltage data, including:

[0023] The sampling value and the actual value of the output voltage are subtracted and input into the preset first PI regulator to obtain the basic duty cycle D base ;

[0024] The difference between the average current of the first coupled inductor and the average current of the second coupled inductor is input into a preset second PI regulator to obtain a duty cycle change ΔD of the two switch tube branches.

[0025] Further, the controlling of the interleaved parallel Boost circuit based on the basic duty cycle and the duty cycle variation includes:

[0026] Based on the calculated basic duty cycle D base The duty ratios of the first switch tube branch and the second switch tube branch are calculated based on the duty ratio change ΔD, and are used to control the first switch tube branch and the second switch tube branch.

[0027] Furthermore, the duty ratios of the first switch tube branch and the second switch tube branch are D base +ΔD and D base -ΔD.

[0028] The present invention adopts the above technical solution, which has the following advantages:

[0029] 1. Based on the staggered parallel Boost circuit, the present invention introduces an H-bridge auxiliary boost circuit based on coupled inductors, which is connected in series and superimposed with the staggered parallel Boost converter, thereby effectively improving the voltage gain;

[0030] 2. The present invention adopts coupled inductors to replace the independent inductors in the traditional staggered parallel Boost circuit. The current on the secondary side of the coupled inductors is superimposed on the filter inductor current of the staggered parallel Boost circuit, so that the current of the switch tube is less than 0 at the turn-on time, thereby realizing the soft switching operation of the circuit and improving the efficiency of the circuit.

[0031] 3. The present invention connects the secondary sides of the two coupled inductors in reverse series so that the currents converted to the primary sides can cancel each other out after superposition, thereby eliminating the influence of the H-bridge auxiliary boost circuit on the input current ripple. Therefore, the input current ripple only depends on the staggered parallel Boost circuit, thereby reducing the input current ripple;

[0032] 4. The voltage stress of the switch tube of the present invention is less than that of the switch tube of the traditional staggered parallel boost converter. Since the present invention introduces an additional H-bridge auxiliary boost unit, the output voltage is composed of the output of the staggered parallel boost circuit and the output of the H-bridge auxiliary boost unit, so that the output voltage of the staggered parallel boost circuit is less than the final output voltage, and the voltage stress of the switch tube is lower.

[0033] The present invention overcomes the shortcomings of hard switching operation and low efficiency at high gain of traditional interleaved parallel Boost circuits, and has the advantages of low current ripple, high voltage gain, soft switching operation, etc., and is suitable for occasions such as fuel cells and photovoltaics that require high-gain DC-DC converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings:

[0035] Figure 1 It is the topological structure diagram of interleaved parallel Boost converter;

[0036] Figure 2 is a topological structure diagram of a high-gain soft switching circuit provided by an embodiment of the present invention;

[0037] Figure 3 is a structural diagram of an H-bridge auxiliary boost unit provided in an embodiment of the present invention;

[0038] Figure 4is a control block diagram provided by an embodiment of the present invention;

[0039] The reference numerals in the figures are as follows:

[0040] 1. Staggered parallel Boost circuit; 2. H-bridge auxiliary boost circuit; 3. First Boost branch; 4. Second Boost branch; 5. First coupled inductor; 6. First switch tube branch; 7. Second coupled inductor; 8. Second switch tube branch; 9. First rectifier branch; 10. Second rectifier branch. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0042] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0043] In view of the defects of the existing staggered parallel Boost technology, such as low efficiency at high gain and hard switching operation, in some embodiments of the present invention, a high-gain low-ripple DC-DC converter based on coupled inductors is provided. By introducing an H-bridge auxiliary boost circuit based on coupled inductors, it is connected in series with the traditional staggered parallel Boost converter to effectively improve the voltage gain; at the same time, by introducing coupled inductors, the current on the secondary side of the coupled inductors is superimposed on the filter inductor current of the Boost circuit, so that the current of the switch tube at the turn-on time can be less than 0, thereby realizing the soft switching operation of the circuit. The present invention can be widely used in fuel cells, photovoltaics and other applications that require high voltage gain and low current ripple.

[0044] Correspondingly, in some other embodiments of the present invention, a control method for a high-gain and low-ripple DC-DC converter based on coupled inductors is also provided.

[0045] Example 1

[0046] like Figure 2As shown, this embodiment provides a high-gain, low-ripple DC-DC converter based on coupled inductors, and its topology structure includes: an interleaved parallel Boost circuit and an H-bridge auxiliary boost circuit. The input side of the interleaved parallel Boost circuit is connected to the input voltage source, the output side of the interleaved parallel Boost circuit is connected in series with the H-bridge auxiliary boost circuit and then connected to the load, and the input side of the H-bridge auxiliary boost circuit is coupled to the interleaved parallel Boost circuit.

[0047] Preferably, the staggered parallel Boost circuit includes a first Boost branch and a second Boost branch, and the first Boost branch includes a first coupled inductor and a first switch tube branch, and the second Boost branch includes a second coupled inductor and a second switch tube branch. One end of the first coupled inductor and the second coupled inductor are connected in parallel to an input voltage source, and the first switch tube branch and the second switch tube branch are connected in parallel to serve as the output end of the staggered parallel Boost circuit; the primary sides of the first coupled inductor and the second coupled inductor serve as filter inductors of the staggered parallel Boost circuit, and the secondary sides of the first coupled inductor and the second coupled inductor are connected in anti-phase series and coupled to the H-bridge auxiliary boost circuit.

[0048] Preferably, the first switch tube branch includes a first upper switch tube and a first lower switch tube, and the second switch tube branch includes a second upper switch tube and a second lower switch tube. Wherein, after the source terminal of the first upper switch tube and the drain terminal of the first lower switch tube are connected in series, their connection point is connected to the other end of the first coupling inductor; after the source terminal of the second upper switch tube and the drain terminal of the second lower switch tube are connected in series, their connection point is connected to the other end of the second coupling inductor; after the drain terminal of the first upper switch tube and the drain terminal of the second upper switch tube are connected in parallel, they are connected to one end of the output capacitor; after the source terminal of the first lower switch tube and the source terminal of the second lower switch tube are connected in parallel, they are connected to the other end of the output capacitor, and the two ends of the output capacitor serve as the output ends of the staggered parallel Boost circuit.

[0049] In fact, in the staggered parallel Boost circuit of this embodiment, the first coupled inductor and the first switch tube branch constitute the first Boost branch, the second coupled inductor and the second switch tube branch constitute the second Boost branch, and the phases of the two Boost branches are 180° opposite to each other, which can reduce the input current ripple. Moreover, in the single-branch Boost circuit of the present invention, the filter inductor is composed of the primary side of the coupled inductor, the lower switch tube is the main tube, and the upper switch tube is the auxiliary tube. The conduction time of the main tube and the auxiliary tube is complementary, and there is a certain dead zone. The output voltage can be adjusted by controlling the duty cycle of the main tube.

[0050] Preferably, the H-bridge auxiliary boost circuit includes a first rectifying branch and a second rectifying branch arranged in parallel, and a first upper diode and a first lower diode connected in series are arranged on the first rectifying branch, and the connection point of the first upper diode and the first lower diode is connected to one end of the secondary side of the first coupled inductor as a midpoint of the H-bridge auxiliary boost circuit; a second upper diode and a second lower diode connected in series are arranged on the second rectifying branch, and the connection point of the second upper diode and the second lower diode is connected to one end of the secondary side of the second coupled inductor as another midpoint of the H-bridge auxiliary boost circuit, and the secondary side of the first coupled inductor is connected in reverse series with the other end of the secondary side of the second coupled inductor.

[0051] In the H-bridge auxiliary boost circuit, the secondary sides of the two coupled inductors are connected in reverse series, and the two ends are connected to the midpoint of the H-bridge. The purpose of reverse series connection is to make the two secondary currents of the coupled inductors offset each other after being converted to the primary side, so that the primary current of the coupled inductors depends only on the staggered parallel boost circuit and has nothing to do with the H-bridge auxiliary boost circuit, thereby reducing the input current ripple.

[0052] Preferably, if Figure 3 As shown, the first upper diode, the first lower diode, the second upper diode and the second lower diode in the H-bridge auxiliary boost circuit can also use switching devices such as MOSFET or IGBT. When the diode is replaced with a switching device, the converter can transmit energy in the reverse direction. Therefore, the high-gain soft-switching converter based on coupled inductors proposed in the present invention is not limited to unidirectional applications, and can also achieve reverse energy transmission after replacing the switching device, thereby broadening the application scope of the present invention.

[0053] Example 2

[0054] Based on the high-gain low-ripple DC-DC converter based on coupled inductors provided in Example 1, this embodiment provides a control method for a high-gain low-ripple DC-DC converter based on coupled inductors, comprising the following steps:

[0055] 1) Collect relevant current and voltage data;

[0056] 2) Based on the collected current and voltage data, the basic duty cycle and duty cycle variation of the interleaved parallel Boost circuit are calculated;

[0057] 3) Control the interleaved parallel Boost circuit based on the basic duty cycle and the duty cycle variation.

[0058] Preferably, in the above step 1), the current and voltage data are collected, including collecting the average current of the first coupled inductor and the second coupled inductor in the staggered parallel Boost circuit and the output voltage of the DC-DC converter.

[0059] Preferably, in the above step 2), based on the collected current and voltage data, the basic duty cycle and duty cycle variation of the staggered parallel Boost circuit are calculated, including:

[0060] 2.1) The sampling value and the actual value of the output voltage are subtracted and input into the preset first PI regulator to obtain the basic duty cycle D base ;

[0061] 2.2) The average current of the first coupled inductor and the average current of the second coupled inductor are input into a preset second PI regulator to obtain the duty cycle change ΔD of the two switch tube branches.

[0062] Preferably, in the above step 3), controlling the staggered parallel Boost circuit based on the basic duty cycle and the duty cycle variation includes:

[0063] Based on the calculated basic duty cycle D base The duty ratios of the first switch tube branch and the second switch tube branch are calculated based on the duty ratio change ΔD, and are used to control the first switch tube branch and the second switch tube branch.

[0064] The duty ratios of the first switch tube branch and the second switch tube branch are D base +ΔD and D base -ΔD.

[0065] 1) collecting the average current of the first coupled inductor and the second coupled inductor and the output voltage of the DC-DC converter;

[0066] 2) Subtract the sampled value of the output voltage from the actual value and input it into the first PI regulator to obtain a basic duty cycle D base ;

[0067] 3) Subtract the average current of the first coupled inductor from the average current of the second coupled inductor and input it into the second PI regulator to obtain the duty cycle change ΔD of the two branches;

[0068] 4) Based on the basic duty cycle D calculated in step 2) base The duty cycle change ΔD calculated in step 3) is calculated to obtain the duty cycles of the first switch tube branch and the second switch tube branch as D1=D base +ΔD and D2 = D base -ΔD, to realize the control of DC-DC converter.

[0069] In summary, the voltage gain of the high-gain, low-ripple DC-DC converter based on coupled inductors provided in this embodiment depends not only on the duty cycle of the Boost circuit, but also on the turns ratio of the coupled inductors (the turns ratio N of the coupled inductors is related to the boost ratio, which is equal to N / (1-d), d is the duty cycle, generally working at 0.6-0.7, and the boost ratio depends on the application scenario, so the turns ratio N can be calculated). The larger the duty cycle, the higher the turns ratio of the coupled inductors, and the higher the circuit boost. Therefore, the coupled inductor ratio can be reasonably designed according to the gain requirements of the actual application scenario, so that the circuit achieves a higher gain while the duty cycle is not too large.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A high-gain, low-ripple DC-DC converter based on coupled inductors, characterized in that: Its topological structure includes: an interleaved parallel Boost circuit and an H-bridge auxiliary boost circuit; the interleaved parallel Boost circuit includes a first Boost branch and a second Boost branch; the first Boost branch includes a first coupled inductor and a first switch tube branch, and the second Boost branch includes a second coupled inductor and a second switch tube branch; one end of the first coupled inductor and the second coupled inductor are connected in parallel and connected to an input voltage source, and the first switch tube branch and the second switch tube branch are connected in parallel as the output end of the interleaved parallel Boost circuit; the primary sides of the first coupled inductor and the second coupled inductor serve as the filter inductor of the interleaved parallel Boost circuit, the secondary sides of the first coupled inductor and the second coupled inductor are connected in anti-phase series and coupled to the H-bridge auxiliary boost circuit, and the output side of the interleaved parallel Boost circuit is connected in series with the H-bridge auxiliary boost circuit and then connected to a load.

2. A high-gain, low-ripple DC-DC converter based on coupled inductors as claimed in claim 1, characterized in that: The first switch branch includes a first upper switch tube and a first lower switch tube, and the second switch branch includes a second upper switch tube and a second lower switch tube; After the source terminal of the first upper switch tube and the drain terminal of the first lower switch tube are connected in series, the connection point is connected to the other end of the primary side of the first coupling inductor; The source terminal of the second upper switch tube and the drain terminal of the second lower switch tube are connected in series, and the connection point is connected to the other end of the primary side of the second coupling inductor; The drain terminal of the first upper switch tube and the drain terminal of the second upper switch tube are connected in parallel and then connected to one end of the output capacitor; The source terminal of the first lower switch tube and the source terminal of the second lower switch tube are connected in parallel to the other end of the output capacitor, and the two ends of the output capacitor serve as the output ends of the staggered parallel Boost circuit.

3. A high-gain, low-ripple DC-DC converter based on coupled inductors as claimed in claim 1, characterized in that: The H-bridge auxiliary boost circuit comprises a first rectifying branch and a second rectifying branch arranged in parallel; The first rectifying branch is provided with two first rectifying devices connected in series, and the connection point of the two first rectifying devices is connected to one end of the secondary side of the first coupled inductor as a midpoint of the H-bridge auxiliary boost circuit; The second rectifying branch is provided with two second rectifying devices connected in series, and the connection point of the two second rectifying devices is connected to one end of the secondary side of the second coupled inductor as another midpoint of the H-bridge auxiliary boost circuit, and the secondary side of the first coupled inductor is connected in reverse series with the other end of the secondary side of the second coupled inductor.

4. A high-gain, low-ripple DC-DC converter based on coupled inductors as claimed in claim 3, characterized in that: The first rectifying device and the second rectifying device are diodes or switch devices.

5. A high-gain, low-ripple DC-DC converter based on coupled inductors as claimed in claim 4, characterized in that: The switch device is a MOSFET or an IGBT device.

6. A control method for a high-gain, low-ripple DC-DC converter based on coupled inductance according to any one of claims 1 to 5, characterized in that: The following steps are involved: Collect current and voltage data; Based on the collected current and voltage data, the basic duty cycle and duty cycle variation of the interleaved parallel Boost circuit are calculated; The interleaved parallel Boost circuit is controlled based on the basic duty cycle and the duty cycle variation.

7. The control method of the high-gain low-ripple DC-DC converter based on coupled inductance according to claim 6, characterized in that: The collecting of current and voltage data includes collecting average currents of the first coupled inductor and the second coupled inductor in the staggered parallel Boost circuit and the output voltage of the DC-DC converter.

8. The control method of the high-gain low-ripple DC-DC converter based on coupled inductance according to claim 7, characterized in that: The basic duty cycle and duty cycle variation of the staggered parallel Boost circuit are calculated based on the collected current and voltage data, including: The sampling value and the actual value of the output voltage are subtracted and input into the preset first PI regulator to obtain the basic duty cycle D base ; The difference between the average current of the first coupled inductor and the average current of the second coupled inductor is input into a preset second PI regulator to obtain a duty cycle change ΔD of the two switch tube branches.

9. The control method of the high-gain low-ripple DC-DC converter based on coupled inductance according to claim 8, characterized in that: The controlling of the interleaved parallel Boost circuit based on the basic duty cycle and the duty cycle variation comprises: Based on the calculated basic duty cycle D base The duty ratios of the first switch tube branch and the second switch tube branch are calculated based on the duty ratio change ΔD, and are used to control the first switch tube branch and the second switch tube branch.

10. The control method of the high-gain low-ripple DC-DC converter based on coupled inductance according to claim 9, characterized in that: The duty ratios of the first switch tube branch and the second switch tube branch are respectively D base +ΔD and D base -ΔD.

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