A three-level BOOST device and its control method

Abstract

The present application discloses a three-level BOOST device and a control method thereof, which relates to the fields of power electronics and new energy power generation technology. The main circuit of the device includes: a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first switch tube, a second switch tube, a third switch tube, a first diode, and a second diode. The device controls the first switch tube and the third switch tube to be turned on, and uses the voltage between the positive and negative poles of the main circuit input terminal to pre-charge the first capacitor and the second capacitor respectively. At the same time, after the first capacitor and the second capacitor are pre-charged, the first switch tube and the third switch tube are disconnected and the second switch tube is connected, and the voltage of the first capacitor and the second capacitor is used to pre-charge the third capacitor and the fourth capacitor respectively. The solution of the present application can achieve staggered wave generation, while also reducing the inductor ripple current, reducing the inductance value and the device volume.

Description

Technical Field

[0001] The present application belongs to the technical field of power electronics and new energy power generation technology, and specifically relates to a three-level BOOST device and a control method thereof. Background Art

[0002] In 1500V photovoltaic system applications, due to the IGBT voltage withstand, the DC boost stage requires a three-level BOOST topology. The mainstream solutions are dual-BOOST three-level circuits and flying capacitor three-level BOOST. With the dual-BOOST three-level circuit approach, if interleaved generation is used, the system common-mode current will be very high. In practical applications, synchronous generation control is generally adopted, resulting in high inductance values. Even with coupled inductor designs, the inductor still has drawbacks such as large size and high cost for the same ripple current, making it difficult to design and integrate. Therefore, current research focuses on optimizing the flying capacitor three-level BOOST circuit. However, both dual-BOOST and flying capacitor three-level circuits are based on the design concept of direct series connection of DC capacitors on the output side, which hinders the simultaneous optimization of interleaved generation and inductance value. Summary of the Invention

[0003] To this end, the present application provides a three-level BOOST device and a control method thereof, aiming to solve the problems that the existing three-level BOOST circuit cannot simultaneously achieve interleaved wave generation and inductance value optimization, as well as the large inductor volume and high equipment cost.

[0004] To achieve the above objectives, this application adopts the following technical solutions:

[0005] In a first aspect, the present application provides a three-level BOOST device, wherein a main circuit of the three-level BOOST device includes: a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first switch tube, a second switch tube, a third switch tube, a first diode, and a second diode;

[0006] A first end of the first inductor is connected to the positive electrode of the power supply, and a second end of the first inductor is connected to the first node; a first end of the first capacitor is connected to the first node, and a second end of the first capacitor is connected to the third node; a first end of the first switch is connected to the first node, and a second end of the first switch is connected to the second node;

[0007] The first end of the second capacitor is connected to the second node, and the second end of the second capacitor is connected to the fourth node; the first end of the third capacitor is connected to the second node, and the second end of the third capacitor is connected to the positive output electrode of the BOOST device; the first end of the second switch tube is connected to the second node, and the second end of the second switch tube is connected to the third node;

[0008] The first end of the third switch is connected to the third node, and the second end of the third switch is connected to the fourth node; the first end of the fourth capacitor is connected to the third node, and the second end of the fourth capacitor is connected to the output negative electrode of the BOOST device;

[0009] The anode of the first diode is connected to the first node, and the cathode of the first diode is connected to the output anode of the BOOST device; the anode of the second diode is connected to the output cathode of the BOOST device, and the cathode of the second diode is connected to the fourth node;

[0010] A first end of the second inductor is connected to the fourth node, and a second end of the second inductor is connected to the negative electrode of the power supply.

[0011] Furthermore, the first switch tube, the second switch tube and the third switch tube are all IGBTs.

[0012] Furthermore, the conduction state of the second switch tube is interlaced with the conduction states of the first switch tube and the third switch tube.

[0013] Furthermore, the duty cycle of the first switching tube is the same as that of the third switching tube.

[0014] Furthermore, the driving signal periods corresponding to the first switching tube and the third switching tube are the same.

[0015] Furthermore, it also includes a first current limiting element and a second current limiting element, the first current limiting element is arranged in the circuit between the first capacitor and the first diode or the first capacitor and the second switching tube; the second current limiting element is arranged in the circuit between the second capacitor and the second diode or the second capacitor and the second switching tube.

[0016] Furthermore, the first current limiting element and the second current limiting element are both one or more of an inductor and a resistor.

[0017] In a second aspect, the present application provides a control method for a three-level BOOST device, the control method being applied to the three-level BOOST device provided in the first aspect, the control method comprising:

[0018] S1: When the positive and negative electrodes of the main circuit input terminal of the three-level BOOST device are charged, the first and third switching tubes are controlled to be turned on simultaneously, and the second switching tube is turned off. The voltage between the positive and negative electrodes of the main circuit input terminal is used to pre-charge the first and second capacitors respectively;

[0019] S2: Adjusting the duty cycle of the first switch tube and the third switch tube so that the voltage between the first capacitor and the second capacitor is balanced;

[0020] S3: After the first capacitor and the second capacitor are pre-charged, the first switch tube and the third switch tube are controlled to be disconnected, and the second switch tube is turned on to pre-charge the third capacitor using the voltage of the first capacitor, and to pre-charge the fourth capacitor using the voltage of the second capacitor;

[0021] S4: Adjust the duty cycle of the second switch tube so that voltage balance is maintained between the first capacitor and the third capacitor, and between the second capacitor and the fourth capacitor.

[0022] This application adopts the above technical solution, which has at least the following beneficial effects:

[0023] The three-level BOOST device provided by the present application has a main circuit including a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a first switch tube, a second switch tube, a third switch tube, a first diode, and a second diode. The first end of the first inductor is connected to the positive electrode of the power supply, and the second end of the first inductor is connected to the first node; the first end of the first capacitor is connected to the first node, and the second end of the first capacitor is connected to the third node; the first end of the first switch tube is connected to the first node, and the second end of the first switch tube is connected to the second node;

[0024] The first end of the second capacitor is connected to the second node, and the second end of the second capacitor is connected to the fourth node; the first end of the third capacitor is connected to the second node, and the second end of the third capacitor is connected to the positive output electrode of the BOOST device; the first end of the second switch tube is connected to the second node, and the second end of the second switch tube is connected to the third node;

[0025] The first end of the third switch is connected to the third node, and the second end of the third switch is connected to the fourth node; the first end of the fourth capacitor is connected to the third node, and the second end of the fourth capacitor is connected to the output negative electrode of the BOOST device;

[0026] The positive electrode of the first diode is connected to the first node, and the negative electrode of the first diode is connected to the output positive electrode of the BOOST device; the positive electrode of the second diode is connected to the output negative electrode of the BOOST device, and the negative electrode of the second diode is connected to the fourth node; the first end of the second inductor is connected to the fourth node, and the second end of the second inductor is connected to the negative electrode of the power supply. In the above-mentioned main circuit structure, the device controls the first switch tube and the third switch tube to be turned on, disconnects the second switch tube, and uses the voltage between the positive and negative poles of the main circuit input end to pre-charge the first capacitor and the second capacitor respectively. At the same time, after the first capacitor and the second capacitor are pre-charged, the first switch tube and the third switch tube are disconnected, and the second switch tube is connected, and the voltage of the first capacitor and the second capacitor is used to pre-charge the third capacitor and the fourth capacitor respectively. The present application scheme chooses to design a three-level BOOST circuit structure by not directly connecting capacitors in series on the high-voltage side, which can achieve staggered wave generation, while also reducing the inductor ripple current, reducing the inductance value and the device volume.

[0027] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 is a schematic diagram showing the circuit structure of a three-level BOOST device according to an exemplary embodiment;

[0030] Figure 2 is a schematic diagram showing the direction of the pre-charging current of the second capacitor according to an exemplary embodiment;

[0031] Figure 3 is a schematic diagram showing the direction of the pre-charging current of the first capacitor according to an exemplary embodiment;

[0032] Figure 4 is a schematic diagram showing the direction of the pre-charging current of the third capacitor according to an exemplary embodiment;

[0033] Figure 5 is a schematic diagram showing the direction of the pre-charging current of the fourth capacitor according to an exemplary embodiment;

[0034] Figure 6 FIG. 1 is a flow chart of a control method for a three-level BOOST device according to an exemplary embodiment. DETAILED DESCRIPTION

[0035] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions of this application will be described in detail below. Obviously, the embodiments described are only some of the embodiments of this application, rather than all of them. Based on the embodiments in this application, all other implementation methods obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0036] See also Figure 1 , Figure 1 This is a schematic diagram of a three-level BOOST device circuit structure according to an exemplary embodiment. In the figure, Udc pv The terminal is the main circuit input terminal of the three-level BOOST device, and its positive and negative poles correspond to the positive and negative poles of the power supply. bus The terminal is the output terminal of the main circuit of the three-level BOOST device, and its positive and negative poles are connected to the load. Figure 1 As shown, the main circuit of the three-level BOOST device includes: a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first inductor Lm1, a second inductor Lm2, a first switch S1, a second switch S2, a third switch S3, a first diode D1 and a second diode D2.

[0037] Among them, the first end of the first inductor Lm1 is connected to the positive electrode of the power supply, and the second end of the first inductor Lm1 is connected to the first node; the first end of the first capacitor C1 is connected to the first node, and the second end of the first capacitor C1 is connected to the third node; the first end of the first switch tube S1 is connected to the first node, and the second end of the first switch tube S1 is connected to the second node.

[0038] A first end of the second capacitor C2 is connected to the second node, and a second end of the second capacitor C2 is connected to the fourth node; a first end of the third capacitor C3 is connected to the second node, and a second end of the third capacitor C3 is connected to the positive output electrode of the BOOST device; a first end of the second switch tube S2 is connected to the second node, and a second end of the second switch tube S2 is connected to the third node.

[0039] A first end of the third switch tube S3 is connected to the third node, and a second end of the third switch tube S3 is connected to the fourth node; a first end of the fourth capacitor C4 is connected to the third node, and a second end of the fourth capacitor C4 is connected to the output negative electrode of the BOOST device.

[0040] The anode of the first diode D1 is connected to the first node, and the cathode of the first diode D1 is connected to the output anode of the BOOST device; the anode of the second diode D2 is connected to the output cathode of the BOOST device, and the cathode of the second diode D2 is connected to the fourth node.

[0041] A first end of the second inductor Lm2 is connected to the fourth node, and a second end of the second inductor Lm2 is connected to the negative electrode of the power supply.

[0042] Furthermore, in one embodiment, the first switch S1, the second switch S2, and the third switch S3 are all IGBTs. An IGBT (Insulated Gate Bipolar Transistor), an insulated gate bipolar transistor, is a composite fully controlled voltage-driven power semiconductor device composed of a bipolar junction transistor (BJT) and an insulated gate field-effect transistor (MOS). It combines the advantages of the high input impedance of a metal-oxide-semiconductor field-effect transistor (MOSFET) and the low on-state voltage drop of a giant transistor (GTR), while also having the advantages of small size, low on-state voltage, and low cost. The present application utilizes IGBTs to conduct the circuit, which can reduce the size of the device and reduce the cost of the device. In addition, other switching devices can also be used to control the conduction and disconnection of the circuit, which is not limited here and depends on the specific application environment, all of which are within the scope of protection of this application.

[0043] Furthermore, in one embodiment, since the first, second, and third switches S1, S2, and S3 are all IGBT devices, to achieve staggered wave generation, the conduction state of the second switch S2 in this application solution is staggered with the conduction states of the first and third switches S1, S3. Furthermore, the duty cycles of the first and third switches S1, S3 are the same, and the drive signal periods corresponding to the first and third switches S1, S3 are the same.

[0044] Specifically, under the above circuit structure design, if Figure 2 As shown, after the positive and negative electrodes of the main circuit input terminal are charged, the present application solution controls the on and off of the first switch tube S1 so as to pre-charge the second capacitor C2 with the voltage between the positive and negative electrodes of the main circuit input terminal when starting the machine.

[0045] Specifically, such as Figure 3As shown, the present application solution controls the on-off of the third switch tube S3 to pre-charge the first capacitor C1 with the voltage between the positive and negative electrodes of the main circuit input terminal.

[0046] Specifically, such as Figure 4 and Figure 5 As shown, the present application solution controls the on-off of the second switch tube S2 to pre-charge the third capacitor C3 with the voltage of the first capacitor C1 and to pre-charge the fourth capacitor C4 with the voltage of the second capacitor C2. Figures 2 to 5 In the figure, the dashed line with an arrow indicates the direction of current.

[0047] Furthermore, in one embodiment, the present application solution can achieve voltage balancing between the second capacitor C2 and the first capacitor C1 by adjusting the duty cycle of the first switch S1 and the third switch S3. It can also achieve voltage balancing between the first capacitor C1 and the third capacitor C3, and between the second capacitor C2 and the fourth capacitor C4, by adjusting the duty cycle of the second switch S2. The duty cycle and drive period of the first switch S1, the second switch S2, and the third switch S3 can be set based on the capacity of the first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4. It is sufficient to ensure voltage balancing between the four capacitors. This is not limited here and depends on the specific application environment, all of which are within the scope of protection of this application.

[0048] Furthermore, in one embodiment, the three-level BOOST device provided by the present application solution to achieve smooth charging of the third capacitor C3C3 further includes a first current limiting element and a second current limiting element. The first current limiting element is arranged in the circuit between the first capacitor C1 and the first diode D1 or the first capacitor C1 and the second switch tube S2; the second current limiting element is arranged in the circuit between the second capacitor C2 and the second diode D2 or the second capacitor C2 and the second switch tube S2. The first current limiting element and the second current limiting element are both one or more of an inductor and a resistor, and other current limiting components may also be used. This is not limited here and depends on the specific application environment. They are all within the scope of protection of this application.

[0049] Please refer to Figure 6 The present application also provides a control method for a three-level BOOST device. The control method is applied to the three-level BOOST device provided in the present application. The control method includes:

[0050] S1: When the positive and negative electrodes of the main circuit input terminal of the three-level BOOST device are charged, the first switch S1 and the third switch S3 are controlled to be turned on simultaneously, and the second switch S2 is turned off. The voltage between the positive and negative electrodes of the main circuit input terminal is used to pre-charge the first capacitor C1 and the second capacitor C2 respectively;

[0051] S2: Adjust the duty cycle of the first switch S1 and the third switch S3 to maintain voltage balance between the first capacitor C1 and the second capacitor C2;

[0052] S3: After the first capacitor C1 and the second capacitor C2 are pre-charged, the first switch S1 and the third switch S3 are turned off, and the second switch S2 is turned on. The voltage of the first capacitor C1 is used to pre-charge the third capacitor C3, and the voltage of the second capacitor C2 is used to pre-charge the fourth capacitor C4.

[0053] S4: Adjust the duty cycle of the second switch S2 so that the voltages between the first capacitor C1 and the third capacitor C3, and between the second capacitor C2 and the fourth capacitor C4 are balanced.

[0054] This application solution designs a three-level boost circuit structure without directly connecting capacitors in series on the high-voltage side. It also independently controls and adjusts the conduction state and duty cycle of the first, second, and third switches S1, S2, and S3. This enables interleaved power generation while also reducing inductor ripple current, inductance value, and device size.

[0055] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0056] It should be noted that, in the description of this application, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" or "multiple" is at least two.

[0057] It should be understood that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intervening element at the same time; when an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intervening element at the same time. In addition, the "connection" used here may include wireless connection; the wording "and / or" used includes any unit and all combinations of one or more associated listed items.

[0058] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application belong.

[0059] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0060] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0061] In addition, the functional units in the various embodiments of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into a module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0062] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0063] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0064] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A three-level BOOST device, characterized in that: The main circuit of the three-level BOOST device includes: a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first switch tube, a second switch tube, a third switch tube, a first diode and a second diode; A first end of the first inductor is connected to the positive electrode of the power supply, and a second end of the first inductor is connected to the first node; a first end of the first capacitor is connected to the first node, and a second end of the first capacitor is connected to the third node; a first end of the first switch is connected to the first node, and a second end of the first switch is connected to the second node; The first end of the second capacitor is connected to the second node, and the second end of the second capacitor is connected to the fourth node; the first end of the third capacitor is connected to the second node, and the second end of the third capacitor is connected to the positive output electrode of the BOOST device; the first end of the second switch tube is connected to the second node, and the second end of the second switch tube is connected to the third node; The first end of the third switch is connected to the third node, and the second end of the third switch is connected to the fourth node; the first end of the fourth capacitor is connected to the third node, and the second end of the fourth capacitor is connected to the output negative electrode of the BOOST device; The anode of the first diode is connected to the first node, and the cathode of the first diode is connected to the output anode of the BOOST device; the anode of the second diode is connected to the output cathode of the BOOST device, and the cathode of the second diode is connected to the fourth node; A first end of the second inductor is connected to the fourth node, and a second end of the second inductor is connected to the negative electrode of the power supply.

2. A three-level BOOST device according to claim 1, characterized in that: The first switch tube, the second switch tube and the third switch tube are all IGBTs.

3. The three-level BOOST device according to claim 1, characterized in that: The conduction state of the second switch tube is interlaced with the conduction states of the first switch tube and the third switch tube.

4. The three-level BOOST device according to claim 1, characterized in that: The duty cycle of the first switching tube is the same as that of the third switching tube.

5. The three-level BOOST device according to claim 1, characterized in that: The driving signal cycles corresponding to the first switching tube and the third switching tube are the same.

6. The three-level BOOST device according to claim 1, characterized in that: It also includes a first current limiting element and a second current limiting element. The first current limiting element is arranged in the circuit between the first capacitor and the first diode or the first capacitor and the second switching tube; the second current limiting element is arranged in the circuit between the second capacitor and the second diode or the second capacitor and the second switching tube.

7. The three-level BOOST device according to claim 6, characterized in that: The first current limiting element and the second current limiting element are both one or more of an inductor and a resistor.

8. A control method for a three-level BOOST device, characterized in that: The control method is applied to a three-level BOOST device according to any one of claims 1 to 7, and the control method includes: S1: When the positive and negative electrodes of the main circuit input terminal of the three-level BOOST device are charged, the first and third switching tubes are controlled to be turned on simultaneously, and the second switching tube is turned off, so that the voltage between the positive and negative electrodes of the main circuit input terminal is used to pre-charge the first and second capacitors respectively; S2: Adjusting the duty cycle of the first switch tube and the third switch tube so that the voltage between the first capacitor and the second capacitor is balanced; S3: After the first capacitor and the second capacitor are pre-charged, the first switch tube and the third switch tube are controlled to be disconnected, and the second switch tube is turned on to pre-charge the third capacitor using the voltage of the first capacitor, and to pre-charge the fourth capacitor using the voltage of the second capacitor; S4: Adjust the duty cycle of the second switch tube so that voltage balance is maintained between the first capacitor and the third capacitor, and between the second capacitor and the fourth capacitor.

Images