CN106301037A - A kind of high voltage ac/dc electrical energy changer and control method thereof - Google Patents

Abstract

The present invention relates to a kind of high voltage ac/dc electrical energy changer, it is made up of three-phase structure, phase structure is connected by upper and lower two brachium pontis converter units and forms, brachium pontis converter unit is made up of two groups of device cascade structures and sub module cascade structure, the technical scheme that the present invention provides carries out switching operation by devices in series structure to cascade submodule, achieve the transformation of electrical energy of alternating current-direct current, the topology that part proposes, by using full-bridge sub modular structure also can realize the self-cleaning of DC Line Fault, meets the application demand of aerial line.

Description

A high-voltage AC-DC power conversion device and its control method

technical field

The invention relates to an AC/DC conversion device, in particular to a high-voltage AC/DC power conversion device and a control method thereof.

Background technique

There have been many research results on high-voltage DC-AC converters. Based on the original two-level technology, modular multi-level technology is currently the most popular converter technology suitable for high-voltage flexible DC transmission technology. It has been extensively studied in many literatures, and engineering applications up to ±320kV/1000MW have been realized.

Existing flexible DC technologies mainly use cables for power transmission. In order to further extend the flexible DC technology to the overhead line system, the half-bridge sub-module structure (Figure 1(a)) must be replaced by the full-bridge sub-module structure (Figure 1(b)), however, this method causes system loss And investment has risen sharply, making it difficult to meet engineering needs.

Aiming at the topological structure of the cable system application, the "HYBRID 2-LEVEL ANDMULTILEVEL HVDC CONVERTER" of the patent US 20130128629A1 proposes a new type of converter structure, which can greatly reduce the semiconductor devices and capacitors used, but the control method is complicated and has Many technical problems are difficult to solve;

Aiming at the application requirements of the overhead line system, the "AMultilevel Converter with HybridFull Bridge Cells" of the patent WO2014/111164A1 proposes to change the bridge arm into a half-bridge and full-bridge hybrid structure, which reduces the system loss and investment; the "AMultilevel Converter with HybridFull Bridge Cells" of the patent WO2011/098117A1 "Converter for High voltage DC Transmission" proposes an inverter bridge arm converter, which realizes electric energy conversion by combining two-level and modular multi-level structures, but requires complex and precise energy balance control, which is actually realized more difficult.

Contents of the invention

In order to solve the deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a high-voltage AC-DC power conversion device and its control method. The high-voltage AC-DC power conversion device performs switching operations on cascaded sub-modules through a device series structure, The power conversion of AC and DC is realized, and some of the proposed topologies can also realize the self-clearing of DC faults by using the full-bridge sub-module structure, which meets the application requirements of overhead lines.

The object of the present invention is to adopt following technical scheme to realize:

The present invention provides a high-voltage AC-DC power conversion device. The improvement is that the AC-DC power conversion device is composed of a three-phase structure, each phase is a single-phase structure, and the single-phase structure is composed of two upper and lower bridges. The arm transformation unit is connected.

Wherein, the bridge arm transformation unit is composed of two sets of device cascade structures and sub-module cascade structures, including three composition modes:

1) The two sets of device cascade structures are connected in star form to the sub-module cascade structures, and the two sets of device cascade structures are connected in series; one end of one set of device cascade structures is connected to the AC terminal, and the other set of device cascade structures are connected in series. One end of the cascade structure is connected to the DC positive terminal when it is used as the upper bridge arm conversion unit structure, and connected to the DC negative terminal when it is used as the lower bridge arm conversion unit structure; The common point between, and the other end is connected to the ground point;

2) The two groups of device cascade structures are connected in a star shape to the sub-module cascade structure, wherein one end of one group of device cascade structures is connected to an AC terminal, and the other end is connected to one end of the sub-module cascade structure; the other group One end of the device cascade structure is connected to the ground point, and the other end is connected to one end of the submodule cascade structure; the other end of the submodule cascade structure is connected to a DC positive terminal or a DC negative terminal;

3) The two sets of device cascade structures are connected in a star shape to the sub-module cascade structure, one end of one group of device cascade structures is connected to the DC positive terminal or the DC negative terminal, and the other end is connected to one end of the sub-module cascade structure connection; the other end of the sub-module cascade structure is connected to the AC terminal; the other end of the device cascade structure is connected to the ground point, and the other end is connected to the common point between the device cascade structure and the sub-module cascade structure .

Wherein, the device cascade structure is composed of power electronic devices in series, and the power electronic devices are composed of fully controlled devices and their anti-parallel diodes, and the fully controlled devices include insulated gate bipolar transistors IGBT, gates The thyristor GTO, the integrated gate commutated thyristor IGCT and the electron injection enhanced gate transistor IEGT are turned off.

Wherein, the sub-module cascading structure is composed of half-bridge sub-modules or full-bridge sub-modules cascading, and a reactor is connected in series on the bridge arm of the sub-module cascading structure.

Wherein, when the sub-module cascading structure is composed of full-bridge sub-module cascading, the self-clearing of DC faults can be realized and the application requirements of overhead lines can be met.

The present invention also provides a control method for a high-voltage AC-DC power conversion device, the improvement of which is that the method includes the following implementation methods:

① For mode 1) when the middle bridge arm conversion unit is used as the upper bridge arm conversion unit, when the AC voltage output is a positive half wave, one group of device cascade structure S1p is turned on, and the other group of device cascade structure S2p is turned off. The sub-module cascade structure outputs the positive half-wave AC voltage Uc, which is used to support the AC voltage; when the AC voltage output is a negative half-wave, another group of device cascade structures S2p is turned on, and one group of device cascade structures S1p is turned off , the sub-module cascade structure outputs a DC voltage Vd/2, which is used to support the positive DC voltage.

For mode 1) when the conversion unit of the middle bridge arm is used as the conversion unit of the lower bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1n is turned on, and the other group of device cascade structure S2n is turned off, and the sub The module cascade structure SMn outputs a DC voltage Vd/2, which is used to support the negative DC voltage; when the AC voltage output is a negative half-wave, one of the device cascade structures S1n is turned off, and the other device cascade structure S2n is turned on , the sub-module cascade structure SMn outputs the absolute value of the AC voltage |Uc|, which is used to support the AC voltage;

②For mode 2) when the conversion unit of the middle bridge arm is used as the conversion unit of the upper bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1p is turned on, and the other group of device cascade structure S2p is turned off. The sub-module cascade structure outputs the difference Vd/2-Uc between the DC positive voltage and the AC voltage, which is used to support the AC voltage; when the AC voltage output is a negative half-wave, another group of device cascade structure S2p is turned on, and one of the The device cascade structure S1p is turned off, and the sub-module cascade structure outputs a DC voltage Vd/2, which is used to support the positive DC voltage;

For mode 2) when the conversion unit of the middle bridge arm is used as the conversion unit of the lower bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1n is turned on, and the other group of device cascade structure S2n is turned off, and the sub The module cascade structure SMn outputs a DC voltage Vd/2, which is used to support the negative DC voltage; when the AC voltage output is a negative half-wave, one of the device cascade structures S1n is turned off, and the other device cascade structure S2n is turned on , the sub-module cascade structure SMn outputs the difference between the AC voltage and the DC negative voltage Vd/2+Uc, which is used to support the AC voltage;

③ For mode 3) when the middle bridge arm conversion unit is used as the upper bridge arm conversion unit, when the AC voltage output is a positive half wave, one group of device cascade structure S1p is turned on, and the other group of device cascade structure S2p is turned off. The sub-module cascade structure outputs the difference Vd/2-Uc between the DC positive voltage and the AC voltage, which is used to support the AC voltage; when the AC voltage output is a negative half-wave, another group of device cascade structure S2p is turned on, and one of the The device cascade structure S1p is turned off, and the sub-module cascade structure outputs the absolute value of the AC voltage |Uc|, which is used to support the AC voltage;

For mode 3) when the conversion unit of the middle bridge arm is used as the conversion unit of the lower bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1n is turned on, and the other group of device cascade structure S2n is turned off, and the sub The module cascade structure SMn outputs AC voltage Uc to support the AC voltage; when the AC voltage output is a negative half-wave, S1n is turned off, S2n is turned on, and the sub-module cascade structure SMn outputs the difference Vd between the AC voltage and the DC negative voltage /2+Uc for supporting AC voltage.

The excellent effect that technical scheme provided by the invention has is:

1. Only adopt the device series structure and a certain number of sub-modules in series to realize electric energy conversion, with less investment, less loss and less land occupation;

2. The waveforms of the AC side and the DC side are of high quality, and the required filter capacity is small, or even no filter is required;

3. By using the full bridge sub-module, part of the structure can effectively realize the isolation of DC faults, which is suitable for overhead line systems;

3. By adjusting the input quantity of the sub-module cascade structure when the device cascade structure is turned on or off, the soft switching of the device cascade structure can be effectively realized.

Description of drawings

Fig. 1 is a submodule cascade structure topology diagram provided by the present invention, wherein: (a) is a half bridge structure topology diagram, (b) is a full bridge structure topology diagram, and (c) is a submodule cascade structure diagram;

Fig. 2 is a structural diagram of the bridge arm conversion unit provided by the present invention, wherein: (a) is a structural diagram of the upper bridge arm conversion unit realization mode 1, (b) is a structural diagram of the upper bridge arm conversion unit realization mode 2, and (c) is Structural diagram of the third implementation of the upper bridge arm conversion unit; (a') is the first structural diagram of the lower bridge arm conversion unit, (b') is the second structural diagram of the lower bridge arm conversion unit, and (c') is the lower bridge arm conversion unit. Structural diagram of the third implementation mode of the arm transformation unit;

Fig. 3 is a single-phase structural diagram of a high-voltage AC-DC power conversion device provided by the present invention;

Fig. 4 is a three-phase structure diagram of the high-voltage AC-DC power conversion device provided by the present invention.

detailed description

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The following description and drawings illustrate specific embodiments of the invention sufficiently to enable those skilled in the art to practice them. In order to provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is presented below. This summary is not an overview, nor is it intended to identify key/critical elements or delineate the scope of these embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later. Other embodiments may incorporate structural, logical, electrical, process, and other changes. The examples merely represent 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 in or substituted for those of other embodiments. The scope of embodiments of the present invention includes the full scope of the claims, and all available equivalents of the claims. These embodiments of the present invention may be referred to herein, individually or collectively, by the term "invention", which is for convenience only and is not intended to automatically limit the application if in fact more than one invention is disclosed The scope is any individual invention or inventive concept.

Example

The invention provides a high-voltage AC/DC power conversion device, which is composed of a three-phase structure, each phase is a single-phase conversion structure, and the single-phase structure is composed of upper and lower bridge arm conversion units.

The bridge arm transformation unit structure consists of a device cascade structure and a sub-module cascade structure, including three implementation methods:

1) As shown in Figure 2(a) and (a'), two sets of device cascade structures and sub-module cascade structures are connected in a star shape, and the other end of the device cascade structure S1p (S2n) is connected to the AC terminal, and the other end The other end of the device cascade structure S2p (S1n) is connected to the DC positive (negative) terminal; the other end of the sub-module cascade structure SMp (SMn) is connected to the ground point.

2) As shown in Figure 2(b) and (b'), two sets of device cascade structures and sub-module cascade structures are connected in a star shape, and the other end of the device cascade structure S1p (S2n) is connected to the AC terminal, and the other end The other end of the device cascade structure S2p (S1n) is connected to the ground point; the other end of the sub-module cascade structure SMp (SMn) is connected to the DC positive (negative) terminal.

3) As shown in Figure 2(c) and (c'), two sets of device cascade structures and sub-module cascade structures are connected in a star shape, and the remaining end of the device cascade structure S1p (S2n) is connected to the DC positive (negative) terminal , the remaining end of another group of device cascading structures S2p (S1n) is connected to the ground point; the remaining end of the sub-module cascading structure SMp (SMn) is connected to the AC terminal.

The device cascade structure is composed of multiple power electronic devices in series, including fully controlled devices (such as IGBT, GTO, etc.) and their anti-parallel diodes.

The sub-module cascading structure is composed of a plurality of half-bridge or full-bridge sub-modules as shown in Figure 1 in series, and a reactor is connected in series on the bridge arm formed by the sub-module cascading structure.

The present invention also provides a control method for a high-voltage AC/DC power conversion device. The bridge arm conversion unit structure realizes the power conversion function through a certain bridge arm control method, including:

1) For the structure shown in Figure 2(a), when the AC voltage output is a positive half-wave, S1p is turned on, S2p is turned off, and the sub-module cascaded structure SMp outputs the positive half-wave of the AC voltage Uc, which is used to support the AC voltage ; When the AC voltage output is a negative half-wave, S2p is turned on, S1p is turned off, and the sub-module cascade structure SMp outputs a DC voltage Vd/2, which is used to support the positive DC voltage.

For the structure shown in Figure 2(a'), when the AC voltage output is a positive half-wave, S1n is turned on, S2n is turned off, and the sub-module cascade structure SMn outputs a DC voltage Vd/2 to support the negative DC voltage; When the AC voltage output is a negative half-wave, S1n is turned off, S2n is turned on, and the sub-module cascade structure SMn outputs the absolute value of the AC voltage |Uc|, which is used to support the AC voltage.

2) For the structure shown in Figure 2(b), when the AC voltage output is a positive half-wave, S1p is turned on, S2p is turned off, and the sub-module cascade structure SMp outputs the difference between the DC positive voltage and the AC voltage Vd/2- Uc is used to support the AC voltage; when the AC voltage output is a negative half-wave, S2p is turned on, S1p is turned off, and the sub-module cascade structure SMp outputs a DC voltage Vd/2, which is used to support the positive DC voltage.

For the structure shown in Figure 2(b'), when the AC voltage output is a positive half-wave, S1n is turned on, S2n is turned off, and the sub-module cascade structure SMn outputs a DC voltage Vd/2, which is used to support the negative DC voltage; When the AC voltage output is a negative half-wave, S1n is turned off, S2n is turned on, and the sub-module cascade structure SMn outputs the difference Vd/2+Uc between the AC voltage and the DC negative voltage to support the AC voltage.

3) For the structure shown in Figure 2(c), when the AC voltage output is a positive half-wave, S1p is turned on, S2p is turned off, and the sub-module cascade structure SMp outputs the difference between the DC positive voltage and the AC voltage Vd/2- Uc is used to support the AC voltage; when the AC voltage output is a negative half-wave, S2p is turned on, S1p is turned off, and the sub-module cascade structure SMp outputs the absolute value of the AC voltage |Uc|, which is used to support the AC voltage.

For the structure shown in Figure 2(c'), when the AC voltage output is a positive half-wave, S1n is turned on, S2n is turned off, and the sub-module cascaded structure SMn outputs an AC voltage Uc to support the AC voltage; when the AC voltage When the output is a negative half-wave, S1n is turned off, S2n is turned on, and the sub-module cascade structure SMn outputs the difference Vd/2+Uc between the AC voltage and the DC negative voltage to support the AC voltage.

The high-voltage AC-DC power conversion device suitable for high-voltage levels provided by the present invention effectively reduces the demand for the number of energy storage capacitors in the converter, reduces system investment and land occupation, and provides a method for improving the performance of flexible DC technology. new scheme.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still implement the present invention Any modification or equivalent replacement that does not deviate from the spirit and scope of the present invention is within the protection scope of the claims of the pending application of the present invention.

Claims (6)

1. A high-voltage AC-DC power conversion device, characterized in that, the AC-DC power conversion device is composed of a three-phase structure, and each phase is a single-phase structure, and the single-phase structure is composed of two upper and lower bridge arm conversion units Connection composition. 2. The high-voltage AC-DC power conversion device according to claim 1, wherein the bridge arm conversion unit is composed of two sets of device cascade structures and sub-module cascade structures, including three composition modes: 1) The two sets of device cascade structures are connected in star form to the sub-module cascade structures, and the two sets of device cascade structures are connected in series; one end of one set of device cascade structures is connected to the AC terminal, and the other set of device cascade structures are connected in series. One end of the cascade structure is connected to the DC positive terminal when it is used as the upper bridge arm conversion unit structure, and connected to the DC negative terminal when it is used as the lower bridge arm conversion unit structure; The common point between, and the other end is connected to the ground point; 2) The two groups of device cascade structures are connected in a star shape to the sub-module cascade structure, wherein one end of one group of device cascade structures is connected to an AC terminal, and the other end is connected to one end of the sub-module cascade structure; the other group One end of the device cascade structure is connected to the ground point, and the other end is connected to one end of the submodule cascade structure; the other end of the submodule cascade structure is connected to a DC positive terminal or a DC negative terminal; 3) The two sets of device cascade structures are connected in a star shape to the sub-module cascade structure, one end of one group of device cascade structures is connected to the DC positive terminal or the DC negative terminal, and the other end is connected to one end of the sub-module cascade structure connection; the other end of the sub-module cascade structure is connected to the AC terminal; the other end of the device cascade structure is connected to the ground point, and the other end is connected to the common point between the device cascade structure and the sub-module cascade structure . 3. The high-voltage AC-DC power conversion device according to claim 2, wherein the device cascade structure is composed of power electronic devices in series, and the power electronic devices are composed of fully controlled devices and anti-parallel diodes thereof, The fully controlled device includes an insulated gate bipolar transistor IGBT, a gate turn-off thyristor GTO, an integrated gate commutation thyristor IGCT and an electron injection enhanced gate transistor IEGT. 4. The high-voltage AC-DC power conversion device according to claim 2, wherein the sub-module cascaded structure is composed of half-bridge sub-modules or full-bridge sub-modules cascaded, and the bridge arm of the sub-module cascaded structure A reactor is connected in series. 5. The high-voltage AC-DC power conversion device according to claim 4, wherein when the sub-module cascading structure is composed of full-bridge sub-module cascading, self-clearing of DC faults can be realized and the application of overhead lines can be satisfied. need. 6. A control method for the high-voltage AC-DC power conversion device according to any one of claims 2-5, characterized in that the method includes the following implementations: ① For mode 1) when the middle bridge arm conversion unit is used as the upper bridge arm conversion unit, when the AC voltage output is a positive half wave, one group of device cascade structure S1p is turned on, and the other group of device cascade structure S2p is turned off. The sub-module cascade structure outputs the positive half-wave AC voltage Uc, which is used to support the AC voltage; when the AC voltage output is a negative half-wave, another group of device cascade structures S2p is turned on, and one group of device cascade structures S1p is turned off , the sub-module cascade structure outputs a DC voltage Vd/2, which is used to support the positive DC voltage; For mode 1) when the conversion unit of the middle bridge arm is used as the conversion unit of the lower bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1n is turned on, and the other group of device cascade structure S2n is turned off, and the sub The module cascade structure SMn outputs a DC voltage Vd/2, which is used to support the negative DC voltage; when the AC voltage output is a negative half-wave, one of the device cascade structures S1n is turned off, and the other device cascade structure S2n is turned on , the sub-module cascade structure SMn outputs the absolute value of the AC voltage |Uc|, which is used to support the AC voltage; ②For mode 2) when the conversion unit of the middle bridge arm is used as the conversion unit of the upper bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1p is turned on, and the other group of device cascade structure S2p is turned off. The sub-module cascade structure outputs the difference Vd/2-Uc between the DC positive voltage and the AC voltage, which is used to support the AC voltage; when the AC voltage output is a negative half-wave, another group of device cascade structure S2p is turned on, and one of the The device cascade structure S1p is turned off, and the sub-module cascade structure outputs a DC voltage Vd/2, which is used to support the positive DC voltage; For mode 2) when the conversion unit of the middle bridge arm is used as the conversion unit of the lower bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1n is turned on, and the other group of device cascade structure S2n is turned off, and the sub The module cascade structure SMn outputs a DC voltage Vd/2, which is used to support the negative DC voltage; when the AC voltage output is a negative half-wave, one of the device cascade structures S1n is turned off, and the other device cascade structure S2n is turned on , the sub-module cascade structure SMn outputs the difference between the AC voltage and the DC negative voltage Vd/2+Uc, which is used to support the AC voltage; ③ For mode 3) when the middle bridge arm conversion unit is used as the upper bridge arm conversion unit, when the AC voltage output is a positive half wave, one group of device cascade structure S1p is turned on, and the other group of device cascade structure S2p is turned off. The sub-module cascade structure outputs the difference Vd/2-Uc between the DC positive voltage and the AC voltage, which is used to support the AC voltage; when the AC voltage output is a negative half-wave, another group of device cascade structure S2p is turned on, and one of the The device cascade structure S1p is turned off, and the sub-module cascade structure outputs the absolute value of the AC voltage |Uc|, which is used to support the AC voltage; For mode 3) when the conversion unit of the middle bridge arm is used as the conversion unit of the lower bridge arm, when the AC voltage output is a positive half wave, one group of device cascade structure S1n is turned on, and the other group of device cascade structure S2n is turned off, and the sub The module cascade structure SMn outputs AC voltage Uc to support the AC voltage; when the AC voltage output is a negative half-wave, S1n is turned off, S2n is turned on, and the sub-module cascade structure SMn outputs the difference Vd between the AC voltage and the DC negative voltage /2+Uc for supporting AC voltage.