A modular machine-based cascaded frequency converter

Abstract

The utility model discloses a kind of cascaded frequency converters based on module machine, belong to high voltage frequency converter technical field.It is composed of multiple parallel power branches, each the power branch is composed of one frequency converter module machine or multiple series-connected frequency converter module machines, the frequency converter module machine has three pairs of connection terminals corresponding frequency converter three-phase respectively, multiple two-level topology H bridge power units or multiple three-level topology H bridge power units are connected in series between each pair of connection terminals.By flexible series connection and parallel connection of frequency converter module machine, frequency converter of different voltage grade and different power grade is realized;By the series connection of cascaded frequency converter module machine to adapt to different voltage grade, by the parallel connection of cascaded frequency converter module machine to adapt to different power grade;The kind of cascaded frequency converter module machine is less, design development, control and maintenance are relatively simpler, by flexible series connection and parallel connection configuration, it can be applied to each industry, and convenient later expansion.

Description

Technical Field

[0001] This utility model relates to a cascaded frequency converter based on a modular unit, belonging to the field of high-voltage frequency converter technology. Background Technology

[0002] In industries such as metallurgy, steel, petroleum, chemical, papermaking, water treatment, and medium-sized factories and mines, the use of variable frequency speed control (VFD) solutions can achieve significant energy-saving effects, resulting in substantial direct economic benefits, and even greater macroeconomic and social benefits. In these sectors, electric motors are recognized as major power consumers, accounting for over 60% of the total national electricity consumption, making energy-saving retrofitting of them a huge potential endeavor. With the continuous development of VFD technology, VFDs are being used more and more widely, especially in the field of high-voltage VFD technology. As technology has advanced, the price of high-voltage VFD equipment has decreased, creating favorable conditions for the large-scale promotion and application of high-voltage VFDs.

[0003] Currently, medium and high voltage frequency converters have a wide voltage range, from a few kV to tens of kV, and a wide power range, from hundreds of kW to tens of MW. Domestically, three standard voltages are commonly used: 3kV, 6kV, and 10kV. Internationally, four standard voltages are commonly used: 3.3kV, 6.6kV, 11kV, and 4.16kV (North America), with some other non-standard voltage levels. Therefore, there are many types of medium and high voltage frequency converters and numerous power unit categories, which brings certain difficulties to product design, development, management, and maintenance.

[0004] To address the challenges in designing, developing, managing, and maintaining the wide variety of frequency converters, a cascaded frequency converter based on modular units was designed. Summary of the Invention

[0005] The technical problem to be solved by this utility model is to provide a cascaded frequency converter based on a modular unit, which solves the problems of design, development, control and maintenance difficulties of the current wide variety of frequency converters.

[0006] The technical problem to be solved by this utility model is achieved by the following technical solution:

[0007] A cascaded frequency converter based on a modular unit is provided, which consists of multiple parallel power branches. Each power branch consists of one frequency converter modular unit or multiple frequency converter modular units connected in series. The frequency converter modular unit has three pairs of terminals respectively corresponding to the three phases of the frequency converter. Multiple two-level topology H-bridge power units or multiple three-level topology H-bridge power units are connected in series between each pair of terminals.

[0008] As a preferred example, the two-level topology H-bridge power unit consists of four power modules forming an H-bridge structure. The DC bus side of the two-level topology H-bridge power unit adopts multiple parallel capacitor branches, each of which consists of one capacitor or multiple capacitors connected in series.

[0009] As a preferred example, the three-level topology H-bridge power unit consists of eight power modules forming an H-bridge structure. The DC bus side of the three-level topology H-bridge power unit is divided into positive, midpoint, and negative terminals. Multiple parallel capacitor branches are used between the positive and midpoint and between the midpoint and negative terminals. Each capacitor branch consists of one or more capacitors connected in series.

[0010] As a preferred example, the type of capacitor includes, but is not limited to, electrolytic capacitors and film capacitors.

[0011] As a preferred example, the power module types include, but are not limited to, IGBT single transistor, IGBT half-bridge module, IGBT full-bridge module, power MOSFET, SiC single transistor, and SiC module.

[0012] As a preferred example, the power module types include, but are not limited to, IGBT single transistor, IGBT half-bridge module, IGBT full-bridge module, IGBT three-level module, power MOSFET, SiC single transistor, and SiC module.

[0013] The beneficial effects of this utility model are:

[0014] By flexibly connecting frequency converter modules in series and parallel, frequency converters of different voltage and power levels can be realized; cascaded frequency converter modules can be connected in series to accommodate different voltage levels, and cascaded frequency converter modules can be connected in parallel to accommodate different power levels; there are fewer types of cascaded frequency converter modules, and their design, development, control, and maintenance are relatively simple. Through flexible series and parallel configurations, they can be applied to various industries and are convenient for future expansion. Attached Figure Description

[0015] Figure 1 This is a 3kV-4kV two-level topology inverter module with three capacitors connected in series and then in parallel on the DC bus side.

[0016] Figure 2 Example 2: A 3kV-4kV two-level topology inverter module machine with two capacitors connected in series and then in parallel on the DC bus side;

[0017] Figure 3 Example 3: A 3kV-4kV two-level topology inverter module machine with a capacitor connected in series and then in parallel on the DC bus side;

[0018] Figure 4 This is a two-level H-bridge power unit;

[0019] Figure 5 It is a 6kV-7kV three-level topology frequency converter module;

[0020] Figure 6 It is a three-level H-bridge power unit.

[0021] Figure 7 The wiring terminal structure of the frequency converter module;

[0022] Figure 8 Parallel application circuit for 3kV-4kV cascaded high-voltage frequency converter modules;

[0023] Figure 9 Parallel application circuit for 6kV-8kV cascaded high-voltage frequency converter modules;

[0024] Figure 10 This is a parallel application circuit for 9kV-12kV cascaded high-voltage frequency converter modules.

[0025] In the diagram: 1. Inverter module; 2. Two-level topology H-bridge power unit; 3. Capacitor branch; 4. Capacitor; 5. Power module; 6. Three-level topology H-bridge power unit; 7. Power branch; 8. High-voltage motor. Detailed Implementation

[0026] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this utility model, the following description, in conjunction with specific illustrations, further elaborates on this utility model.

[0027] like Figure 1 As shown, the DC bus side uses a 3kV-4kV two-level topology inverter module 1, consisting of three capacitors connected in series and then in parallel. Inverter module 1 has three pairs of terminals corresponding to inverter 3: (T1_A, T2_A), (T1_B, T2_B), and (T1_C, T2_C). The same number of two-level topology H-bridge power units 2 are connected in series between each pair of terminals. Figure 1 Three two-level topology H-bridge power units 2 are connected in series between each pair of terminals, and there are a total of nine two-level topology H-bridge power units 2 between the three-phase terminals of the inverter module 1. The DC bus side of the two-level topology H-bridge power unit 2 adopts multiple parallel capacitor branches 3, and each capacitor branch 3 consists of three capacitors 4 connected in series.

[0028] like Figure 2As shown, the DC bus side uses a 3kV-4kV two-level topology inverter module 1, consisting of two capacitors connected in series and then in parallel. Inverter module 1 has three pairs of terminals corresponding to inverter 3: (T1_A, T2_A), (T1_B, T2_B), and (T1_C, T2_C). The same number of two-level topology H-bridge power units 2 are connected in series between each pair of terminals. Figure 2 Three two-level topology H-bridge power units 2 are connected in series between each pair of terminals, and there are a total of nine two-level topology H-bridge power units 2 between the three-phase terminals of the inverter module 1. The DC bus side of the two-level topology H-bridge power unit 2 adopts multiple parallel capacitor branches 3, and each capacitor branch 3 consists of two capacitors 4 connected in series.

[0029] like Figure 3 As shown, the DC bus side uses a 3kV-4kV two-level topology inverter module 1 with one capacitor connected in series and then in parallel. Inverter module 1 has three pairs of terminals corresponding to inverter 3: (T1_A, T2_A), (T1_B, T2_B), and (T1_C, T2_C). The same number of two-level topology H-bridge power units 2 are connected in series between each pair of terminals. Figure 3 Three two-level topology H-bridge power units 2 are connected in series between each pair of terminals, and there are a total of nine two-level topology H-bridge power units 2 between the three-phase terminals of the inverter module 1. The DC bus side of the two-level topology H-bridge power unit 2 adopts multiple parallel capacitor branches 3, and each capacitor branch 3 consists of a capacitor 4.

[0030] The above three types of 3kV-4kV two-level topology inverter module units 1 all use a two-level topology H-bridge power unit 2 connected in series. The difference lies in the number of capacitors 4 used in the DC bus side capacitor branch 3, which are three, two, and one respectively. Multiple capacitors 4 in the capacitor branch 3 can be used to improve voltage withstand capability, achieve voltage equalization, and flexibly configure capacity and voltage withstand. The number of parallel capacitor branches 3 for the three types is determined according to the power of each two-level topology H-bridge power unit 2 to meet the power requirements of the 3kV-4kV two-level topology inverter module unit 1 in actual applications.

[0031] like Figure 4 As shown, the two-level topology H-bridge power unit 2 consists of four power modules 5 forming an H-bridge structure. The DC bus side of the two-level topology H-bridge power unit 2 uses multiple parallel capacitor branches 3, each capacitor branch 3 consisting of one capacitor 4 or multiple capacitors 4 connected in series. Figure 4 The capacitor branch 3 consists of three capacitors 4 connected in series. The types of capacitors 4 include, but are not limited to, electrolytic capacitors 4 and film capacitors 4. The types of power modules 5 include, but are not limited to, single IGBT transistors, IGBT half-bridge modules, IGBT full-bridge modules, power MOSFETs, single SiC transistors, and SiC modules.

[0032] like Figure 5 The 6kV-7kV three-level topology frequency converter module 1 is shown. Module 1 has three pairs of terminals corresponding to the three frequency converters: (T1_A, T2_A), (T1_B, T2_B), and (T1_C, T2_C). The same number of three-level topology H-bridge power units 6 are connected in series between each pair of terminals. Figure 5 Three three-level topology H-bridge power units 6 are connected in series between each pair of terminals in the inverter module 1. There are a total of 9 three-level topology H-bridge power units 6 between the three-phase terminals of the inverter module 1.

[0033] like Figure 6 As shown, the three-level topology H-bridge power unit 6 consists of eight power modules 5 forming an H-bridge structure (four on top and four on the bottom). The DC bus side of the three-level topology H-bridge power unit 6 is divided into positive, midpoint, and negative terminals. Multiple parallel capacitor branches 3 are used between the positive and midpoint terminals and between the midpoint and negative terminals. Each capacitor branch 3 consists of one capacitor 4 or multiple capacitors 4 connected in series. Figure 6 Each capacitor branch 3 consists of one capacitor 4. The advantage of the three-level topology H-bridge power unit 6 is that one three-level topology H-bridge power unit 6 can replace two two-level topology H-bridge power units 2. The types of capacitors 4 include, but are not limited to, electrolytic capacitors 4 and film capacitors 4. The types of power modules 5 include, but are not limited to, IGBT single transistors, IGBT half-bridge modules, IGBT full-bridge modules, IGBT three-level modules, power MOSFETs, SiC single transistors, and SiC modules.

[0034] like Figure 7 The diagram shows the wiring structure of inverter module 1. All inverter modules 1 described above are equipped with three pairs of terminals: (T1_A, T2_A), (T1_B, T2_B), and (T1_C, T2_C). In application, cascaded inverter modules 1 are connected in series to accommodate different voltage levels, and cascaded inverter modules 1 are connected in parallel to accommodate different power levels.

[0035] Example 1

[0036] like Figure 8 The circuit diagram shows a parallel application of a 3kV-4kV cascaded high-voltage frequency converter module 1. Multiple frequency converter modules 1 with voltage levels of 3kV-4kV are connected in parallel. Terminals T2_A, T2_B, and T2_C of all frequency converter modules 1 are shorted, and terminals T1_A, T1_B, and T1_C are connected to the U, V, and W phases of the high-voltage motor 8, respectively.

[0037] At voltage levels of 3kV-4kV, frequency converters applicable to different power ranges can be achieved through parallel connection of cascaded frequency converter modules 1.

[0038] Example 2

[0039] like Figure 9 The circuit diagram shows a parallel application of a 6kV-8kV cascaded high-voltage frequency converter module 1. Based on the above circuit, a two-stage structure is added. Each power branch 7 consists of two series-connected 3kV-4kV frequency converter modules 1, referred to as the first-stage frequency converter module 1 and the second-stage frequency converter module 1. Multiple power branches 7 are then connected in parallel. The terminals T2_A, T2_B, and T2_C of the first-stage frequency converter modules 1 in all power branches 7 are shorted. The terminals T1_A, T1_B, and T1_C of the first-stage frequency converter modules 1 are connected to the corresponding terminals T2_A, T2_B, and T2_C of the second-stage frequency converter modules 1. The terminals T1_A, T1_B, and T1_C of the second-stage frequency converter modules 1 are connected to the U, V, and W phases of the high-voltage motor 8. This realizes the parallel application circuit of the 6kV-8kV cascaded high-voltage frequency converter module 1.

[0040] Under voltage levels of 6kV-8kV, frequency converters applicable to different power ranges can be realized through the parallel connection of cascaded frequency converter modules 1.

[0041] Example 3

[0042] like Figure 10 The circuit diagram shows a parallel application of a 9kV-12kV cascaded high-voltage frequency converter module 1. The frequency converter structure is implemented using a three-stage cascade connection. Each power branch 7 consists of three frequency converter modules 1 connected in series at 3kV-4kV voltage levels, referred to as the first-stage frequency converter module 1, the second-stage frequency converter module 1, and the third-stage frequency converter module 1. Multiple power branches 7 are then connected in parallel. The terminals T2_A, T2_B, and T2_C of the first-stage inverter module 1 in all power branches 7 are shorted. The terminals T1_A, T1_B, and T1_C of the first-stage inverter module 1 are connected to the corresponding terminals T2_A, T2_B, and T2_C of the second-stage inverter module 1. The terminals T1_A, T1_B, and T1_C of the second-stage inverter module 1 are connected to the corresponding terminals T2_A, T2_B, and T2_C of the third-stage inverter module 1. The terminals T1_A, T1_B, and T1_C of the third-stage inverter module 1 are connected to the U, V, and W phases of the high-voltage motor 8. This realizes a parallel application circuit for the 9kV-12kV cascaded high-voltage inverter module 1.

[0043] Under voltage levels of 9kV-12kV, frequency converters applicable to different power ranges can be realized through the parallel connection of cascaded frequency converter modules 1.

[0044] The above only lists common application circuits. This invention uses the inverter module 1 as its core component, and through flexible series and parallel connections, it can realize inverters with different voltage and power levels. Different voltage levels are accommodated by connecting the cascaded inverter modules 1 in series, and different power levels are accommodated by connecting them in parallel.

[0045] Cascaded frequency converter modules are less diverse, and their design, development, control, and maintenance are relatively simple. Through flexible series and parallel configurations, they can be applied to various industries. The modular connection method facilitates future capacity expansion.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by this utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A cascaded frequency converter based on a modular unit, characterized in that, It consists of multiple parallel power branches, each of which consists of one frequency converter module or multiple frequency converter modules connected in series. Each frequency converter module has three pairs of terminals corresponding to the three phases of the frequency converter. Multiple two-level topology H-bridge power units or multiple three-level topology H-bridge power units are connected in series between each pair of terminals.

2. The cascaded frequency converter based on a modular unit according to claim 1, characterized in that, The two-level topology H-bridge power unit is an H-bridge structure composed of four power modules. The DC bus side of the two-level topology H-bridge power unit adopts multiple parallel capacitor branches, and each capacitor branch consists of one capacitor or multiple capacitors connected in series.

3. The cascaded frequency converter based on a modular unit according to claim 1, characterized in that, The three-level topology H-bridge power unit is an H-bridge structure composed of eight power modules. The DC bus side of the three-level topology H-bridge power unit is divided into positive, midpoint, and negative terminals. Multiple parallel capacitor branches are used between the positive and midpoint and between the midpoint and negative terminals. Each capacitor branch consists of one or more capacitors connected in series.

4. A cascaded frequency converter based on a modular unit according to claim 2 or 3, characterized in that, The types of capacitors include, but are not limited to, electrolytic capacitors and film capacitors.

5. A cascaded frequency converter based on a modular unit according to claim 2, characterized in that, The types of power modules include, but are not limited to, IGBT single transistors, IGBT half-bridge modules, IGBT full-bridge modules, power MOSFETs, SiC single transistors, and SiC modules.

6. A cascaded frequency converter based on a modular unit according to claim 3, characterized in that, The types of power modules include, but are not limited to, IGBT single transistors, IGBT half-bridge modules, IGBT full-bridge modules, IGBT three-level modules, power MOSFETs, SiC single transistors, and SiC modules.

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