WO2016029824A1

WO2016029824A1 - Direct current voltage conversion device and bridge arm control method therefor

Info

Publication number: WO2016029824A1
Application number: PCT/CN2015/087796
Authority: WO
Inventors: 杨杰; 贺之渊; 汤广福; 庞辉; 李强
Original assignee: 国家电网公司; 国网智能电网研究院; 中电普瑞电力工程有限公司; 国网浙江省电力公司
Priority date: 2014-08-25
Filing date: 2015-08-21
Publication date: 2016-03-03

Abstract

A direct current voltage conversion device and a bridge arm control method therefor. The device is a structure having a single phase, two phases or more than two phases, each phase consisting of a basic function module, the basic function module comprising device cascade structures (S1, S4) connected in series and a sub-module cascade structure. Via combination of the device series connection structures and the sub-module cascade structure, voltage conversion may be implemented without a transformer, soft switching of series connection devices may be implemented, and investment and space may be reduced.

Description

DC voltage conversion device and bridge arm control method thereof

Technical field

The invention relates to a voltage conversion device in the field of flexible direct current transmission, in particular to a direct current voltage conversion device and a bridge arm control method thereof.

Background technique

The rapid development of flexible DC technology makes DC power grid possible. DC grid technology has no transmission distance limitation, no reactive power compensation equipment, strong flexibility and controllability, and can provide power supply for large cities and offshore wind power access. Good solutions have broad application prospects.

In practical applications, DC grid technology faces a voltage level conversion problem similar to that of an AC grid, and the research on DC voltage converters is still in a preliminary stage worldwide. According to the characteristics of the DC grid, the main features of the DC voltage converter are as follows:

1. A wide range of voltage ratios can be achieved. The diversity of DC voltage levels requires voltage converters to achieve a wide range of voltage ratios to meet the requirements of different applications;

2. Two-way power flow capability. Due to the flexibility requirements of DC grid power regulation, correspondingly, DC voltage converters need to have bidirectional power regulation capabilities;

3. Fault isolation capability. A good DC transformer should meet the DC fault condition on one side and not affect the operation on the other side, that is, it has fault isolation capability;

4. Lower investment, loss and land occupation. A good DC transformer should have a low investment and a low loss level, and the corresponding components should not be too large to cause excessive land occupation.

There have been a lot of research results for DC-DC converters. In the direction of high-voltage field and the use of modular multi-level technology with good scalability, "face-to-face" modular multi-level transformer is the most basic topology. The topology occupies a large area, and the cost is high, the loss is large, and it is difficult to promote the application on a large scale.

The "Modular Multilevel DC/DC converter for HVDC applications" patent of WO 2014/056540 A1 discloses a novel DC-DC transformer topology of high voltage direct current transmission, in which a two-terminal module in a "face-to-face" topology is shared, effectively reducing The number, sub-modules, and footprint of the sub-modules that the system inputs are used, but the transformer isolation potential must be used.

The "Bidirectional Unisolated DC-DC converter based on cascaded cells" patent of WO 2013/026477 A1 discloses a bidirectional isolated DC-DC transformer based on a cascading battery, wherein the disclosed modular multi-level structure directly converted to DC, The transformer is eliminated, which effectively reduces the investment and land occupation. However, the output on the low-voltage side still needs a large reactor or a conjugate reactor, and at the same time, for the fault isolation, an additional full-bridge sub-module is required.

In summary, the traditional low-voltage topology is difficult to apply to the high-voltage field. On the other hand, the DC-DC transformer based on modular multi-level technology has received wide attention from its good expansion performance. However, it was originally proposed. "face-to-face" type DC transformer based on modular multi-level technology, connecting two AC/DC modular multi-level converters through AC transformer to carry out voltage conversion, which not only occupies a large area, but also has high cost and high loss. It is difficult to carry out extensive promotion.

Summary of the invention

In order to solve the above deficiencies in the prior art, an object of the present invention is to provide a DC voltage conversion device and a bridge arm control method thereof. The technical solution provided by the present invention adopts a method in which a device serial structure and a sub-module are cascaded, Transformer In the case of voltage conversion, it also enables soft switching of series devices and reduces investment and footprint. In order to have a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This generalization is not a general comment, nor is it intended to identify key/critical constituent elements or to describe the scope of protection of these embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the following detailed description.

The object of the present invention is achieved by the following technical solutions:

The invention provides a DC voltage conversion device, which is a single-phase, two-phase or two-phase structure, each phase consisting of a basic functional module, the improvement being that the basic functional module comprises a series device cascade Structure and submodule cascade structure.

Further, the basic functional module includes two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure and one end of the device cascade structure S1 and the device respectively One end of the cascade structure S4 is connected; the other end of the device cascade structure S1 is connected to a low voltage terminal, the other end of the device cascade structure S4 is connected to a ground point; the other end of the sub-module cascade structure is connected to High voltage terminal.

Further, the basic functional module includes two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure and one end of the device cascade structure S1 and the device respectively One end of the cascade structure S4 is connected; the other end of the device cascade structure S1 is connected to a high voltage terminal, and the other end of the device cascade structure S4 is connected to a low voltage terminal; the other end of the submodule cascade structure is connected to Grounding point.

Further, the basic functional module includes four sets of device cascade structures S1, S4', S1' and S4 and a sub-module cascade structure; the device cascade structures S1 and S4' are connected between the high voltage terminal and the low voltage terminal The other two device cascade structures S1' and S4 are connected between the low voltage terminal and the ground point; one end of the submodule cascade structure is connected to the connection point between the device cascade structures S1 and S4', and the other end is connected to A connection point between the device cascade structure S1' and S4.

Further, the device cascade structure is composed of a plurality of power electronic devices connected in series, the power electronic devices including fully-controlled devices (such as IGBT, GTO, etc.) and their anti-parallel diodes, semi-controlled devices (such as thyristors, etc.) Or a diode.

Further, the sub-module cascade structure is composed of a plurality of half-bridge sub-module cascade structures and a reactor in series, a full-bridge sub-module cascade structure and a reactor are connected in series or a full-bridge sub-module cascade structure and a half bridge The module cascade structure is composed of a full bridge type device which is connected in series with a capacitor in parallel; the full bridge submodule is composed of an H bridge and a capacitor in parallel; each bridge arm of the H bridge is composed of Controlled devices (such as IGBT, GTO, etc.); each fully controlled device is anti-parallel diode.

Further, when the device includes at least two basic functional modules, a two-phase structure or a two-phase or more structure, that is, a transform unit, whose operating frequency is a fundamental frequency or a high frequency is formed.

Further, when the device cascade structure is turned on or off, the number of inputs of the sub-module cascade structure is adjusted, and the soft switching function of the device cascade structure is realized.

The invention also provides a bridge arm control method for a DC voltage conversion device, wherein the basic function module in the DC voltage conversion device realizes voltage conversion by bridge arm control; the improvement is that the method is based on the connection of the basic function module Different ways include the following implementations:

1) The basic functional module comprises two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure is respectively connected with one end of the device cascade structure S1 and a device level One end of the connected structure S4 is connected; the other end of the device cascade structure S1 is connected to the low voltage terminal, and the other end of the device cascade structure S4 is connected to the ground Point; the other end of the sub-module cascade structure is connected to the high voltage terminal; when the device cascade structure S1 is turned on, the device cascade structure S4 is turned off, and the low voltage terminal positive current enters the submodule through the device cascade structure S1 Cascade structure, the voltage outputted by the cascaded structure of the sub-module is a voltage of a high voltage terminal minus a voltage of a low voltage terminal for compensating for a voltage difference between a high voltage terminal and a low voltage terminal; when the device cascade structure S4 is turned on, the device cascade structure S1 is closed. The current difference between the low voltage end and the high voltage end is injected into the sub-module cascade structure through the device cascade structure S4, and the voltage outputted by the sub-module cascade structure is the high voltage end voltage, which is used for compensating the voltage difference between the high voltage end and the ground;

2) The basic function module includes two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure and one end of the device cascade structure S1 and the device cascade structure respectively One end of S4 is connected; the other end of the device cascade structure S1 is connected to a high voltage terminal, the other end of the device cascade structure S4 is connected to a low voltage terminal; the other end of the submodule cascade structure is connected to a ground point; When the device cascade structure S1 is turned on, the device cascade structure S4 is turned off, and the high voltage terminal positive current enters the submodule cascade structure through the device cascade structure S1, and the output voltage of the submodule cascade structure is The high voltage terminal voltage is used to compensate the voltage difference between the high voltage terminal and the ground; when the device cascade structure S4 is turned on, the device cascade structure S1 is turned off, and the low voltage terminal current is injected into the submodule cascade through the device cascade structure S4. The voltage outputted by the cascaded structure of the sub-module is a low-voltage terminal voltage for compensating for a voltage difference between the low-voltage side and the ground;

3) The basic functional module comprises four sets of device cascade structures S1, S4', S1' and S4 and a sub-module cascade structure connected in a star shape; the device cascade structures S1 and S4' are connected to the high voltage terminal and Between the low voltage terminals, the other two device cascade structures S1' and S4 are connected between the low voltage terminal and the ground point; one end of the submodule cascade structure is connected to the connection point between the device cascade structures S1 and S4'. The other end is connected to a connection point between the device cascade structures S1' and S4; when the device cascade structures S1 and S1' are turned on, the device cascade structures S4 and S4' are turned off, and the high voltage terminal positive current passes. The device cascade structures S1 and S1' enter the sub-module cascade structure, and the output voltage of the sub-module cascade structure shown is a high voltage terminal voltage minus a low voltage terminal voltage for compensating for a voltage difference between the high voltage terminal and the low voltage terminal; When the junction structures S4 and S4' are turned on, the device cascade structures S1 and S1' are turned off, and the current difference between the low voltage terminal and the high voltage terminal is injected into the sub-module cascade structure through the device cascade structures S4 and S4'. The output voltage of the sub-module cascade structure is the low voltage end Pressure for compensating for the low-side voltage difference.

The present invention also provides a DC voltage conversion device, which is improved in that the device includes a basic transformation unit composed of a unipolar structure or a bipolar structure that realizes DC power conversion.

Further, the basic transformation unit is composed of two or more phase basic functional modules in parallel; and the DC power conversion is realized by the bridge arm control method.

Further, the basic functional module includes two device cascade structures and a sub-module cascade structure connected in a star structure;

The remaining end of one of the device cascade structures is connected to the high voltage terminal positive terminal, and the remaining end of the other device cascade structure is connected to the ground point; the remaining end of the submodule cascade structure is connected to the low voltage terminal positive terminal.

Further, the basic function module constitutes a multi-DC terminal basic function module having a plurality of DC voltage conversion capabilities by an additional sub-module cascade structure.

Further, the device cascade structure is formed by a single control device and one of an anti-parallel diode, a half bridge submodule, and a full bridge submodule structure, or a plurality of them are connected in series. Or formed by the series inductance of the above structure; in the absence of power reverse demand, the full control type of the upper or lower arm in the basic functional module formed by the fully controlled device and its anti-parallel diode is omitted. The device becomes a diode cascade or a series arrangement of diodes and inductors.

Further, the sub-module cascade structure is composed of a plurality of full bridge submodules or half bridge submodules, or multiple full bridges The submodule or half bridge submodule is composed of a series connected inductor.

Further, the full bridge sub-module is composed of an H-bridge shunt capacitor bank, and each bridge arm of the H-bridge is composed of a full-control device module and a diode connected in anti-parallel with the same, and the half-bridge sub-module is connected in parallel by a single-phase bridge arm. a capacitor bank consisting of the upper and lower bridge arms, each of the bridge arm submodules being composed of a full control device module and a diode connected in anti-parallel thereto;

The full control device module is composed of a single full control device, or a full control device connected in series or in parallel, the capacitor group being composed of a single capacitor, or a plurality of capacitors connected in series or in parallel.

The invention also provides a bridge arm control method for a DC voltage conversion device, which is improved in that when the basic transformation unit is a single-phase basic function module, the bridge arm control method comprises the following steps:

(1) When the upper arm of the basic function module is turned on, the lower arm thereof is turned off, the positive current Id1 of the high voltage terminal enters the corresponding sub-module cascade structure through the upper bridge arm, and the sub-module cascade structure outputs Ud1-Ud2, Used to compensate the voltage difference across the high-voltage side and low-voltage side output terminals;

(2) When the lower arm of the basic function module is turned on, the upper arm thereof is turned off, and the low-voltage end and the high-voltage end current difference Id2-Id1 of the basic function module are injected into the sub-module cascade structure through the lower arm, and the sub-module level The joint structure output -Ud2 is used to compensate the voltage difference between the low-voltage side output terminal and the ground;

(3) When the upper arm and the lower arm of the basic function module have the same on-time, the power of the capacitor module is kept constant due to the equal power of the sub-module cascade structure, and the conversion of the DC energy is completed.

Further, the on-time of the upper arm and the lower arm of the basic function module are designed according to the balance setting manner, and the switching frequency setting range of the upper arm and the lower arm of the basic function module is not limited.

Further, the balance setting mode adjusts the ratio of the opening time of the upper arm and the lower arm of the corresponding basic function module according to the voltage or energy fluctuation of the sub-module cascade structure.

Further, when the upper arm and the lower arm of the basic function module are turned on and off, the output of the sub-module cascade structure is adjusted to be soft-switched.

Compared with the closest prior art, the technical solution provided by the present invention has the excellent effects of:

1. The technical solution provided by the present invention can realize a wide range of voltage conversion ratios. The diversity of DC voltage levels requires voltage converters to achieve a wide range of voltage ratios to meet the requirements of different applications;

2. With two-way power flow capability. Due to the flexibility requirements of DC grid power regulation, DC voltage converters need to have bidirectional power regulation capabilities;

3. Has good fault isolation capability. A good DC transformer should meet the DC fault condition on one side, and the operation on the other side is not affected, that is, it has fault isolation capability;

4. Low investment, loss and land occupation level. A good DC transformer should have a low investment and a low loss level, and the corresponding components should not be too large to cause excessive land occupation.

5. The DC voltage conversion device provided by the invention only uses IGBT series structure and a certain number of sub-modules to realize voltage conversion in series, with less investment and small loss, and at the same time, low-frequency operation has less improvement on loss; good DC transformer should be invested less With low loss levels;

6. The DC voltage conversion device provided by the invention has high voltage and current quality on the DC side, and no other filter is needed;

7. The DC voltage conversion device provided by the invention can effectively realize fault isolation; a good DC transformer should meet the DC fault condition on one side, and the operation on the other side is not affected, that is, it has fault isolation capability;

8. The DC voltage conversion device provided by the present invention has a wide range of variation ratio and a wide range of voltage conversion ratios. The diversity of DC voltage levels requires voltage converters to achieve a wide range of voltage ratios to meet the requirements of different applications.

9. The DC voltage conversion device provided by the present invention has power flow capability. Due to the flexibility requirement of DC power regulation, correspondingly, the DC voltage converter needs to have bidirectional power adjustment capability.

For the above and related purposes, one or more embodiments include the features that are described in detail below and particularly pointed out in the claims. The following description and the annexed drawings are to be considered in the Other advantages and novel features will become apparent from the Detailed Description of the Drawings.

DRAWINGS

The drawings are intended to provide a further understanding of the invention, and are intended to be a In the drawing:

1 is a structural diagram of a half bridge or full bridge submodule provided by the present invention, wherein (a) is a half bridge submodule structure; (b) is a full bridge submodule structure;

2 is a structural diagram of a basic function module provided by the present invention, wherein (a) is a basic functional module structure diagram 1; (b) is a basic function module structure diagram 2; (c) is a basic function module structure diagram 3;

3 is a structural diagram of a three-phase transform unit provided by the present invention, wherein (a) is a three-phase transform unit structure diagram 1; (b) is a three-phase transform unit structure diagram 2; (c) is a three-phase transform unit structure diagram 3 .

4 is a working mechanism diagram (single DC terminal) of a basic function module provided by the present invention;

Figure 5 is a diagram showing the working mechanism of the basic function module provided by the present invention (multiple DC terminals);

6 is a single phase conversion unit and a working mechanism diagram provided by the present invention;

7 is a topological structural diagram of a multiphase transform unit provided by the present invention;

8 is a bipolar structure diagram of a DC voltage conversion device provided by the present invention;

9 is a structural diagram of a three-phase basic conversion unit of a three-DC terminal provided by the present invention.

detailed description

The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

The detailed description of the embodiments of the invention are set forth in the description Other embodiments may include structural, logical, electrical, process, and other changes. The examples represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operations may vary. Portions and features of some embodiments may be included or substituted for portions and features of other embodiments. The scope of the embodiments of the invention includes the full scope of the claims, and all equivalents of the claims. These embodiments of the invention may be referred to herein, individually or collectively, by the term "invention", merely for convenience, and if more than one invention is disclosed, it is not intended to automatically limit the application. The scope is any single invention or inventive concept.

The invention provides a DC voltage conversion device, which is a single-phase or multi-phase structure, each phase is composed of basic functional modules, including a device cascade structure and a sub-module cascade structure in series; Implementation form:

As shown in FIG. 2(a), the basic functional module includes two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure is respectively cascaded with the device. One end of the device and one end of the structure S1 S4 cascade structure is connected; the other end of the cascade structure of the device S1 is connected to low-voltage terminal (V _L), the other end of the cascade structure device S4 is connected to ground; the The other end of the sub-module cascade structure is connected to the high voltage terminal (V _H ).

As shown in FIG. 2(b), the basic functional module includes two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure is respectively cascaded with the device One end of the structure S1 is connected to one end of the device cascade structure S4; the other end of the device cascade structure S1 is connected to a high voltage terminal (V _H ), and the other end of the device cascade structure S4 is connected to a low voltage terminal (V _L The other end of the sub-module cascade structure is connected to a ground point.

As shown in FIG. 2(c), the basic functional module includes four sets of device cascade structures S1, S4', S1', and S4 and a sub-module cascade structure connected in a star shape; the device cascade structure S1 and S4' is connected between the high voltage terminal (V _H ) and the low voltage terminal (V _L ), and the other two device cascade structures S1' and S4 are connected between the low voltage terminal (V _L ) and the ground point; One end of the junction structure is connected to the connection point between the device cascade structures S1 and S4', and the other end is connected to the connection point between the device cascade structures S1' and S4.

The device cascade structure is composed of a plurality of power electronic devices connected in series, the power electronic devices including fully controlled devices (such as IGBT, GTO, etc.) and their anti-parallel diodes, semi-controlled devices (such as thyristors, etc.) or diodes.

The sub-module cascade structure is composed of a plurality of half-bridge sub-module cascade structures and reactors in series or a full-bridge sub-module cascade structure and a reactor connected in series, and the half-bridge sub-module is composed of a fully-controlled device series branch and a capacitor Parallel composition; the full bridge sub-module is composed of an H-bridge and a capacitor in parallel; each bridge arm of the H-bridge is composed of a fully-controlled device; each fully-controlled device (such as IGBT, GTO, etc.) is anti-parallel diode The structure diagram of the half bridge or full bridge submodule is shown in Figures 1(a) and (b).

The basic function module can be extended to a two-phase structure, or the number of phases can be increased to three-phase or even more phases, and the three-phase transformation unit structure diagram is as shown in Figs. 3(a), (b) and (c), thereby forming a transformation unit. The transform unit can in turn form a parallel or bipolar structure. At the same time, the operating frequency of the transform unit is not limited to the fundamental frequency, and may also be a high frequency operation.

Another advantageous feature of the DC converter topology of the present invention is that the soft switching of the device cascade structure can be effectively realized by adjusting the number of sub-module cascade inputs when the device cascade structure is turned on or off.

The invention also provides a bridge arm control method for a DC voltage conversion device, wherein the basic function module in the DC voltage conversion device realizes voltage conversion by bridge arm control;

1. For the basic functional module structure given in FIG. 2(a), when the device cascade structure S1 is turned on, the device cascade structure S4 is turned off, and the low-voltage terminal positive current enters the sub-module level through the device cascade structure S1. The connection structure, the output voltage of the sub-module cascade structure is a high voltage terminal voltage minus a low voltage terminal voltage, used to compensate a voltage difference between the high voltage terminal and the low voltage terminal; when the device cascade structure S4 is turned on, the device cascade structure S1 is turned off. The current difference between the low voltage end and the high voltage end is injected into the sub-module cascade structure through the device cascade structure S4, and the voltage outputted by the sub-module cascade structure is a negative high voltage terminal voltage, which is used to compensate the high voltage terminal to ground voltage difference.

2. For the basic functional module structure given in FIG. 2(b), when the device cascade structure S1 is turned on, the device cascade structure S4 is turned off, and the high voltage terminal positive current passes through the device cascade structure S1. a module cascade structure, wherein the voltage outputted by the cascaded structure of the submodule is a high voltage terminal voltage for compensating for a voltage difference between the high voltage terminal and the ground; when the device cascade structure S4 is turned on, the device cascade structure S1 is closed. The low-voltage terminal current is injected into the sub-module cascade structure through the device cascade structure S4, and the voltage outputted by the sub-module cascade structure is a low-voltage terminal voltage for compensating for the low-voltage side-to-ground voltage difference.

3. For the basic functional block structure given in FIG. 2(c), when the device cascade structures S1 and S1' are turned on, the device cascade structures S4 and S4' are turned off, and the high voltage terminal positive current passes through the device. The cascaded structures S1 and S1' enter the sub-module cascade structure, and the output voltage of the sub-module cascade structure shown is the high-voltage terminal voltage minus the low-voltage terminal voltage, which is used to compensate the high-voltage end and the low voltage. The voltage difference at the terminals; when the device cascade structures S4 and S4' are turned on, the device cascade structures S1 and S1' are turned off, and the current difference between the low voltage terminal and the high voltage terminal passes through the device cascade structures S4 and S4' The sub-module cascade structure is injected, and the voltage outputted by the sub-module cascade structure is a low-voltage terminal voltage for compensating for a low-voltage terminal-to-ground voltage difference.

The DC voltage conversion device provided by the invention only adopts the device series structure and a certain number of sub-modules to realize voltage conversion in series, with less investment and small loss, and at the same time, the high-frequency operation has less improvement on the loss; the DC-side voltage and current quality at both ends is high. No additional filters are required; power flows in both directions with a wide range of ratios.

The invention provides a DC voltage conversion device, which has the following structure: the device comprises a basic transformation unit, and the basic transformation unit comprises a monopole structure or a bipolar structure to realize conversion of DC power. The bipolar structure diagram is shown in Figure 8.

The basic transformation unit is composed of two-phase or multi-phase basic functional modules in parallel; the DC power conversion is realized by the bridge arm control method. Fig. 4 is a basic functional block of the device, which is composed of two device cascade structures and one sub-module cascade structure, and the three are connected in a star structure. The other end of one device cascade structure is connected to the high voltage terminal positive terminal, and the other end of the other device cascade structure is connected to the ground point; the remaining end of the submodule cascade structure is connected to the low voltage terminal positive terminal. The basic function module can form a multi-DC terminal basic function module with multiple DC voltage conversion capabilities through an additional sub-module cascade structure, as shown in FIG.

The device cascade structure is generally composed of a plurality of fully controlled devices (such as IGBT, GTO, etc.) and its anti-parallel diodes. There may be a series of reactances on the bridge arms. Another alternative is through multiple Figure 1(a). The half bridge or the full bridge submodule shown in Figure 1(b) is connected in series to replace the full control device in series. It is also a feasible solution to mix the full control device with the half bridge and full bridge submodule. The sub-module cascade structure is a series structure of a plurality of half bridge submodules shown in FIG. 1(a) or a full bridge submodule shown in FIG. 1(b), and a reactance may be connected in series on the bridge arm.

In the absence of power reverse demand, the full-control device of the upper or lower arm of the device cascade can be omitted, only diode cascade.

The sub-module cascade structure is formed by cascading a plurality of half bridge submodules or full bridge submodules, and may include a series inductor. The sub-module is shown in Figure 1(b). The full-control device symbol only represents the function. It can be composed of multiple control devices connected in series or in parallel. The capacitance symbol is only representative of the function. It can also be composed of multiple capacitors connected in series or in parallel. .

The invention also provides a bridge arm control method for a DC voltage conversion device. When the basic transformation unit is composed of a single-phase basic function module, the working mechanism is as follows:

(1) When the upper arm S1a is turned on, the lower arm is turned off, and the high-voltage positive current Id1 enters the corresponding sub-module cascade structure through the upper arm, and the sub-module cascade structure outputs Ud1-Ud2 for compensation. The voltage difference across the high-voltage side and low-voltage side output terminals;

(2) When the lower arm S2a is turned on, the upper arm is turned off, and the current difference Id2-Id1 between the low voltage end and the high voltage end is injected into the sub-module cascade structure through the lower arm, and the sub-module cascade structure outputs -Ud2, To compensate the voltage difference between the low-voltage side output terminal and the ground.

(3) When the turn-on time of S1a and S2a is about the same, since the charge and discharge power of the sub-module cascade structure is close, the capacitance energy can be maintained unchanged, thereby completing the power conversion.

For the single phase structure shown in Figure 6, S1a, S2b and S2a, S1b generally operate as complementary pairs.

1. When S1a and S2b are turned on, the high-voltage positive current Id1 enters the corresponding sub-module cascade structure through S1a, and the sub-module cascade structure outputs Ud1-Ud2 for compensating for the voltage difference between the high-voltage side and low-voltage side output terminals. The current difference Id2-Id1 between the low voltage end and the high voltage end is injected into the sub-module cascade structure through S2b, and the sub-module cascade structure output -Ud2 is used to compensate the voltage difference between the low-voltage side output terminal and the ground.

2. When S2a and S1b are turned on, the high-voltage positive current Id1 enters the corresponding sub-module cascade structure through S2a. The sub-module cascade structure outputs Ud1-Ud2 to compensate the voltage difference between the high-voltage side and low-voltage side output terminals. The current difference Id2-Id1 between the low voltage end and the high voltage end is injected into the sub-module cascade structure through S1b, and the sub-module cascade structure output -Ud2 is used to compensate the voltage difference between the low-voltage side output terminal and the ground.

Since the charging and discharging powers of the two sub-module cascade structures are basically the same, the energy can be kept constant. If the energy of the cascaded structure of the two sub-modules is deviated due to errors, etc., the ratio of the input time of the two complementary pairs can be adjusted. To make adjustments.

The basic function module can be extended to the single-phase structure of Fig. 6, or the phase number can be increased to three-phase or even more phases (Fig. 7), thereby forming a basic transformation unit, and the three-phase basic three-phase basic transformation unit structure diagram is as shown in Fig. 9. It can be seen that the basic transformation unit can in turn form a bipolar structure by the form of FIG. At the same time, the operating frequency of the transform unit is not limited to the fundamental frequency, but may also be low frequency and high frequency operation.

Another advantageous feature of the topology result of the present invention is that the soft switching of the device cascade structure can be effectively realized by adjusting the number of sub-module cascade structures when the device cascade structure is turned on or off.

In the above Detailed Description, various features are grouped together in a single embodiment to simplify the present disclosure. This method of disclosure is not to be interpreted as reflecting the intention that the embodiments of the claimed subject matter are claimed in the claims. Rather, as the following claims reflect, the invention is in a <RTIgt; Therefore, the appended claims are hereby expressly incorporated in the claims

Various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments herein can be implemented as electronic hardware, computer software, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described in terms of their functionality. Whether such functionality is implemented as hardware or as software depends on the particular application and design constraints imposed on the overall system. Skilled artisans are capable of <Desc/Clms Page number> number> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt;

The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above-described embodiments, but one of ordinary skill in the art will recognize that the various embodiments can be further combined and arranged. Accordingly, the embodiments described herein are intended to cover all such modifications, modifications, and variations in the scope of the appended claims. Furthermore, the term "comprising", as used in the specification or the claims, is intended to cover the term "comprising" as used in the claims. Furthermore, any use of the term "or" in the specification of the claims is intended to mean "non-exclusive or".

It should be noted that the above embodiments are only for explaining the technical solutions of the present invention and are not limited thereto. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still implement the present invention. Modifications or equivalents are intended to be included within the scope of the appended claims.

Claims

A DC voltage conversion device, the device being a single-phase, two-phase or two-phase structure, each phase being composed of a basic functional module, wherein the basic functional module comprises a device cascade structure and a sub-module cascade in series structure.
The DC voltage conversion device according to claim 1, wherein said basic function module comprises two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; said sub-module cascade structure One end of the device cascade structure S1 and one end of the device cascade structure S4 are respectively connected; the other end of the device cascade structure S1 is connected to the low voltage terminal, and the other end of the device cascade structure S4 is connected to the ground point The other end of the sub-module cascade structure is connected to the high voltage terminal.
The DC voltage conversion device according to claim 1, wherein said basic function module comprises two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; said sub-module cascade structure One end of the device cascade structure S1 and one end of the device cascade structure S4 are respectively connected; the other end of the device cascade structure S1 is connected to the high voltage terminal, and the other end of the device cascade structure S4 is connected to the low voltage terminal The other end of the sub-module cascade structure is connected to a ground point.
The DC voltage conversion device according to claim 1, wherein said basic function module comprises four sets of device cascade structures S1, S4', S1' and S4 and a sub-module cascade structure; said device cascade structure S1 and S4' are connected between the high voltage terminal and the low voltage terminal, and the other two device cascade structures S1' and S4 are connected between the low voltage terminal and the ground point; one end of the submodule cascade structure is connected to the device cascade structure S1 The connection point with S4' is connected to the connection point between the device cascade structures S1' and S4.
The DC voltage conversion device according to claim 1, wherein said device cascade structure is composed of power electronic devices connected in series, said power electronic device comprising a fully controlled device and an anti-parallel diode thereof, a semi-controlled device or diode.
The DC voltage conversion device according to claim 1, wherein the sub-module cascade structure is composed of a cascade structure of a half bridge submodule and a reactor in series, and the cascade structure of the full bridge submodule is formed in series with the reactor or The full bridge submodule cascade structure is combined with the half bridge submodule cascade structure, wherein the half bridge submodule is composed of a full control type device connected in series and connected in parallel with a capacitor; the full bridge submodule is composed of an H bridge and a capacitor in parallel; Each of the bridge arms of the H-bridge is composed of a fully-controlled device; each fully-controlled device has an anti-parallel diode.
The DC voltage conversion device according to claim 1, wherein when the device comprises at least two basic functional modules, a two-phase structure or a two-phase or more structure, that is, a transform unit, wherein the operating frequency of the transform unit is Base frequency or high frequency.
The DC voltage conversion device according to claim 1, wherein when the device cascade structure is turned on or off, the number of inputs of the sub-module cascade structure is adjusted to implement a soft switching function of the device cascade structure.
A bridge arm control method for a DC voltage conversion device according to any one of claims 1 to 8, wherein a basic function module in the DC voltage conversion device realizes voltage conversion by bridge arm control; The method according to the connection mode of the basic function module includes the following implementation modes:

1) The basic functional module comprises two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure is respectively connected with one end of the device cascade structure S1 and a device level One end of the connection structure S4 is connected; the other end of the device cascade structure S1 is connected to the low voltage terminal, the other end of the device cascade structure S4 is connected to the ground point; the other end of the sub-module cascade structure is connected to the high voltage a terminal; when the device cascade structure S1 is turned on, the device cascade structure S4 is turned off, and the low-voltage terminal positive current enters the sub-module cascade structure through the device cascade structure S1, and the output voltage of the sub-module cascade structure is The voltage of the high voltage terminal is reduced by the voltage of the low voltage terminal to compensate the voltage difference between the high voltage terminal and the low voltage terminal. When the device cascade structure S4 is turned on, the device cascade structure S1 is turned off, and the current difference between the low voltage terminal and the high voltage terminal passes through the device cascade structure S4. Injecting a sub-module cascade structure, the output voltage of the sub-module cascade structure is a high-voltage terminal voltage, which is used for compensating for a voltage difference between the high-voltage terminal and the ground;

2) The basic function module includes two sets of device cascade structures S1 and S4 and a sub-module cascade structure connected in a star shape; one end of the sub-module cascade structure and one end of the device cascade structure S1 and the device cascade structure respectively One end of S4 is connected; the other end of the device cascade structure S1 is connected to a high voltage terminal, and the other end of the device cascade structure S4 is connected to a low voltage terminal; the submodule is cascaded The other end of the structure is connected to the grounding point; when the device cascade structure S1 is turned on, the device cascade structure S4 is turned off, and the high voltage terminal positive current flows through the device cascade structure S1 into the submodule cascade structure, The voltage outputted by the sub-module cascade structure is a high voltage terminal voltage for compensating for the voltage difference between the high voltage terminal and the ground; when the device cascade structure S4 is turned on, the device cascade structure S1 is turned off, and the low voltage terminal current passes through the device. The cascade structure S4 is injected into the sub-module cascade structure, and the voltage outputted by the sub-module cascade structure is a low-voltage terminal voltage for compensating for the low-voltage side-to-ground voltage difference;

3) The basic functional module comprises four sets of device cascade structures S1, S4', S1' and S4 and a sub-module cascade structure connected in a star shape; the device cascade structures S1 and S4' are connected to the high voltage terminal and Between the low voltage terminals, the other two device cascade structures S1' and S4 are connected between the low voltage terminal and the ground point; one end of the submodule cascade structure is connected to the connection point between the device cascade structures S1 and S4'. The other end is connected to a connection point between the device cascade structures S1' and S4; when the device cascade structures S1 and S1' are turned on, the device cascade structures S4 and S4' are turned off, and the high voltage terminal positive current passes. The device cascade structures S1 and S1' enter the sub-module cascade structure, and the output voltage of the sub-module cascade structure shown is a high voltage terminal voltage minus a low voltage terminal voltage for compensating for a voltage difference between the high voltage terminal and the low voltage terminal; When the junction structures S4 and S4' are turned on, the device cascade structures S1 and S1' are turned off, and the current difference between the low voltage terminal and the high voltage terminal is injected into the sub-module cascade structure through the device cascade structures S4 and S4'. The output voltage of the sub-module cascade structure is the low voltage end Pressure for compensating for the low-side voltage difference.
A DC voltage conversion device, characterized in that the device comprises a basic transformation unit composed of a unipolar structure or a bipolar structure for realizing DC power conversion.
The DC voltage conversion device according to claim 10, wherein the basic conversion unit is constituted by two-phase or multi-phase basic function modules in parallel; and the DC power conversion is realized by the bridge arm control method.
The DC voltage conversion device according to claim 11, wherein said basic function module comprises two device cascade structures and a submodule cascade structure connected in a star structure;

The remaining end of one of the device cascade structures is connected to the high voltage terminal positive terminal, and the remaining end of the other device cascade structure is connected to the ground point; the remaining end of the submodule cascade structure is connected to the low voltage terminal positive terminal.
The DC voltage conversion device according to claim 12, wherein the basic function module constitutes a multi-DC terminal basic function module having a plurality of DC voltage conversion capabilities by an additional sub-module cascade structure.
The DC voltage conversion device according to claim 12, wherein said device cascade structure is separately connected in series by a fully controlled device and an anti-parallel diode, a half bridge submodule, and a full bridge submodule structure. Or formed by several kinds of hybrids in series, or formed by a series inductance of the above structure; in the absence of power reverse demand, the basic functions formed by the fully controlled device and its anti-parallel diode are omitted. The fully-controlled device of the upper or lower arm of the module becomes a diode cascade or a series arrangement of diodes and inductors.
The DC voltage conversion device according to claim 12, wherein the sub-module cascade structure is composed of a plurality of full bridge submodules or half bridge submodules, or a plurality of full bridge submodules or half bridges. The sub-module cascade structure consists of series inductors.
The DC voltage conversion device according to claim 15, wherein said full bridge sub-module is composed of an H-bridge shunt capacitor bank, and each bridge arm of the H-bridge is composed of a full-control device module and a diode connected in anti-parallel thereto The half bridge sub-module is composed of a single-phase bridge arm parallel capacitor group, and the single-phase bridge arm includes two upper and lower bridge arms, and each bridge arm sub-module is composed of a full-control device module and a diode connected in anti-parallel thereto;

The full control device module is composed of a single full control device, or a full control device connected in series or in parallel, the capacitor group being composed of a single capacitor, or a plurality of capacitors connected in series or in parallel.
A bridge arm control method for a DC voltage conversion device according to any one of claims 10 to 16, wherein when the basic conversion unit is a single-phase basic function module, the bridge arm control method includes the following step:

(1) When the upper arm of the basic function module is turned on, the lower arm thereof is turned off, the positive current Id1 of the high voltage terminal enters the corresponding sub-module cascade structure through the upper bridge arm, and the sub-module cascade structure outputs Ud1-Ud2, Used to compensate voltage across the high side and low side output terminals difference;

(2) When the lower arm of the basic function module is turned on, the upper arm thereof is turned off, and the low-voltage end and the high-voltage end current difference Id2-Id1 of the basic function module are injected into the sub-module cascade structure through the lower arm, and the sub-module level The joint structure output -Ud2 is used to compensate the voltage difference between the low-voltage side output terminal and the ground;

(3) When the upper arm and the lower arm of the basic function module have the same on-time, the power of the capacitor module is kept constant due to the equal power of the sub-module cascade structure, and the conversion of the DC energy is completed.
The bridge arm control method according to claim 17, wherein the upper arm and the lower arm of the basic function module are designed according to a balance setting manner, and the upper arm and the lower bridge of the basic function module are The arm's switching frequency setting range is unlimited.
The bridge arm control method according to claim 18, wherein the balance setting mode adjusts the opening time of the upper arm and the lower arm of the corresponding basic function module according to the voltage or energy fluctuation of the sub-module cascade structure proportion.
The bridge arm control method according to claim 19, wherein when the upper arm and the lower arm of the basic function module are turned on and off, the output of the sub-module cascade structure is adjusted to be soft-switched. .