CN106301037B - A high-voltage AC-DC power conversion device and its control method - Google Patents

Abstract

The invention relates to a high-voltage AC-DC power conversion device, which is composed of a three-phase structure, a single-phase structure is composed of upper and lower bridge arm conversion units connected, and the bridge arm conversion unit is composed of two sets of device cascade structures and sub-module cascade structures. The technical scheme provided by the present invention performs switching operations on cascaded sub-modules through a device series structure, thereby realizing AC/DC power conversion. Some of the proposed topologies can also achieve self-clearing of DC faults by using a full-bridge sub-module structure, which satisfies the requirements of overhead. line application requirements.

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. On the basis of 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 has achieved engineering applications up to ±320kV/1000MW.

The existing flexible DC technology mainly uses cables for power transmission. In order to further promote the flexible DC technology to the overhead line system, it is necessary to replace the half-bridge sub-module structure (Fig. 1(a)) with the full-bridge sub-module structure (Fig. 1(b)). However, this method causes system losses and investment has risen sharply, making it difficult to meet engineering needs.

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

In response to the application requirements of overhead line systems, "AMultilevelConverterwith Hybrid Full Bridge Cells" of patent WO2014/111164A1 proposes to change the bridge arm to a hybrid structure of half bridge and full bridge, which reduces system loss and investment; patent WO2011/098117A1 "AMultilevelConverterwith Hybrid Full Bridge Cells" Converter for High voltage DC Transmission" proposes a switching bridge-arm converter, which realizes power conversion by combining two-level and modular multi-level structures, but requires complex and accurate energy balance control, and the actual implementation is relatively difficulty.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a high-voltage AC-DC power conversion device and a control method thereof, the high-voltage AC-DC power conversion device performs switching operations on cascaded sub-modules through a device series structure, The AC-DC power conversion 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 to meet the application requirements of overhead lines.

The purpose of this invention is to adopt following technical scheme to realize:

The invention provides a high-voltage AC-DC power conversion device, which is improved in 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 upper and lower bridges. The arm transformation unit is connected to form.

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

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

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

3) The two groups of device cascading structures and the sub-module cascading structure are connected in a star shape, wherein one end of one set of device cascading 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 cascading structure connection; the other end of the sub-module cascade structure is connected to the AC terminal; one end of the other group of device cascade structures 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, the power electronic device is composed of a fully controlled device and its anti-parallel diode, and the fully controlled device includes an insulated gate bipolar transistor IGBT, a gate adjustable Turn-off thyristor GTO, integrated gate commutated thyristor IGCT and electron injection enhanced gate transistor IEGT.

Wherein, the sub-module cascade structure is composed of half-bridge sub-modules or full-bridge sub-modules cascade, and reactors are connected in series on the bridge arms of the sub-module cascade structure.

Wherein, when the sub-module cascade structure is composed of a cascade of full-bridge sub-modules, the self-clearing of the DC fault can be realized, and the application requirements of the overhead line can be met.

The present invention also provides a control method for a high-voltage AC-DC power conversion device, which is improved in that the method includes the following implementations:

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

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

② For the mode 2), when the bridge arm transformation unit is used as the upper bridge arm transformation unit, when the AC voltage output is a positive half-wave, one set of device cascade structure S1p is turned on, and the other set 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, the other group of device cascade structure S2p is turned on, and one group 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 bridge arm transformation unit is used as the lower bridge arm transformation unit, when the AC voltage output is a positive half-wave, one group of device cascade structure S1n is turned on, the other group of device cascade structure S2n is turned off, and the sub- The module cascade structure SMn outputs the DC voltage Vd/2, which is used to support the negative DC voltage; when the AC voltage output is a negative half-wave, one group of the device cascade structure S1n is turned off, and the other group 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 bridge arm transformation unit is used as the upper bridge arm transformation 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, the other group of device cascade structure S2p is turned on, and one group 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 bridge arm transformation unit is used as the lower bridge arm transformation unit, when the AC voltage output is a positive half-wave, one group of the device cascade structure S1n is turned on, the other group of device cascade structure S2n is turned off, and the sub- The module cascade structure SMn outputs the AC voltage Uc, which is used to support the AC voltage; when the AC voltage output is negative half-wave, S1n is turned off, S2n is turned on, and the sub-module cascade structure SMn outputs the difference between the AC voltage and the DC negative voltage Vd /2+Uc, used to support AC voltage.

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

1. Only the device series structure and a certain number of sub-modules are used in series to realize electric energy conversion, with low investment, low loss and small footprint;

2. The waveform quality of the AC side and the DC side is high, 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 isolate the DC fault, which is suitable for overhead line systems;

3. The soft switching of the device cascade structure can be effectively realized by adjusting the number of sub-module cascade structure inputs when the device cascade structure is turned on or off.

Description of drawings

Fig. 1 is a sub-module 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 sub-module cascade structure diagram;

2 is a structural diagram of a bridge arm transformation unit provided by the present invention, wherein: (a) is a structural diagram of a first implementation of the upper bridge arm transformation unit, (b) is a structural diagram of a second implementation of the upper bridge arm transformation unit, and (c) is The structure diagram of the realization mode 3 of the upper bridge arm conversion unit; (a') is the structure diagram of the realization mode 1 of the lower bridge arm conversion unit, (b') is the structure diagram of the realization mode 2 of the lower bridge arm conversion unit, and (c') is the lower bridge arm conversion unit. The third structure diagram of the arm transformation unit implementation mode;

3 is a single-phase structure diagram of the 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 ways

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

The following description and drawings sufficiently illustrate specific embodiments of the invention 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 given below. This summary is not intended to be an extensive review, nor is it intended to identify key/critical elements or delineate the scope of protection of these embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the detailed description that follows. Other embodiments may include structural, logical, electrical, process, and other changes. The examples represent only possible variations. Unless explicitly required, individual components and functions are optional 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 invention includes the full scope of the claims, along with all available equivalents of the claims. These embodiments of the invention may be referred to herein by the term "invention," individually or collectively, for convenience only and not to automatically limit the application if more than one invention is in fact disclosed. The scope is any single 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 conversion unit structure is composed of a device cascade structure and a sub-module cascade structure, including three implementations:

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

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

The sub-module cascade structure is formed by connecting a plurality of half-bridge or full-bridge sub-modules as shown in Figure 1 in series, and reactors are connected in series on the bridge arms formed by the sub-module cascade 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 given 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 cascade structure SMp outputs a positive half-wave of 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 given 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, 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 absolute value of the AC voltage |Uc|, which is used to support the AC voltage.

2) For the structure given 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 given 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 between the AC voltage and the DC negative voltage Vd/2+Uc, which is used to support the AC voltage.

3) For the structure given 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 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 given 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 cascade structure SMn outputs the AC voltage Uc, which is used to support the AC voltage; when the AC voltage When the output is negative half-wave, S1n is turned off, S2n is turned on, and 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.

The high-voltage AC-DC power conversion device suitable for high-voltage grades provided by the present invention effectively reduces the quantity demand for energy storage capacitors in the converter, reduces system investment and land occupation, and provides a flexible DC technology performance improvement. new program.

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. Modifications or equivalent replacements are made in any manner, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are all within the protection scope of the claims of the present invention for which the application is pending.

Claims (5)

1. A high-voltage AC-DC power conversion device is characterized in that, the AC-DC power conversion device is made up 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; The bridge arm conversion unit is composed of two sets of device cascade structures and sub-module cascade structures, including the following three composition modes: 1) The two sets of device cascade structures and the sub-module cascade structures are connected in a star shape, 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 is connected to the AC terminal. One end of the cascade structure is connected to the DC positive terminal when it is used as the upper arm conversion unit structure, and is connected to the DC negative terminal when it is used as the lower arm conversion unit structure; one end of the sub-module cascade structure is connected to one of the two sets of device cascade structures. The common point between them, and the other end is connected to the ground point; 2) The two groups of device cascade structures and the sub-module cascade structures are connected in a star shape, wherein one end of one group of device cascade structures is connected to the AC terminal, and the other end is connected to one end of the sub-module cascade structure; One end of the device cascade structure is connected to the ground point, and the other end is connected to one end of the sub-module cascade structure; the other end of the sub-module cascade structure is connected to the DC positive terminal or the DC negative terminal; 3) The two groups of device cascading structures and the sub-module cascading structure are connected in a star shape, wherein one end of one set of device cascading 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 cascading structure connection; the other end of the sub-module cascade structure is connected to the AC terminal; one end of the other group of device cascade structures 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 ; The device cascade structure is composed of power electronic devices in series, the power electronic device is composed of a fully controlled device and its anti-parallel diode, the fully controlled device is composed of an insulated gate bipolar transistor IGBT, and the gate can be turned off. at least one of a thyristor GTO, an integrated gate commutated thyristor IGCT and an electron injection enhanced gate transistor IEGT; 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 arms of the sub-module cascading structure. 2. The high-voltage AC-DC power conversion device according to claim 1, wherein when the sub-module cascade structure is composed of full-bridge sub-module cascade, self-clearing of DC faults can be realized, and the application of overhead lines can be satisfied. need. 3. A control method for a high-voltage AC-DC power conversion device according to any one of claims 1-2, wherein the method comprises the following implementations: For composition mode 1), when the bridge arm transformation unit is used as the upper bridge arm transformation 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 a positive half-wave Uc of the AC voltage, which is used to support the AC voltage; when the AC voltage output is a negative half-wave, another set of device cascade structures S2p is turned on, and one set of device cascade structures S1p is turned off , the sub-module cascade structure outputs the DC voltage Vd/2, which is used to support the positive DC voltage; For composition mode 1), when the bridge arm transformation unit is used as the lower bridge arm transformation unit, 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, The sub-module cascade structure SMn outputs the DC voltage Vd/2, which is used to support the negative DC voltage; when the AC voltage output is a negative half-wave, one set of the device cascade structure S1n is turned off, and the other set of the 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. 4. A control method of a high-voltage AC-DC power conversion device as claimed in claim 3, characterized in that, when the bridge arm conversion unit is used as the upper bridge arm conversion unit in the composition mode 2), when the AC voltage output is a positive half During the wave, one set of device cascade structure S1p is turned on, the other set of device cascade structure S2p is turned off, and the sub-module cascade structure outputs the difference between the DC positive voltage and the AC voltage Vd/2-Uc, which is used to support the AC voltage ; When the AC voltage output is a negative half-wave, the other group of device cascade structure S2p is turned on, one of the device cascade structure S1p is turned off, and the sub-module cascade structure outputs DC voltage Vd/2, which is used to support the positive DC Voltage; For composition mode 2), when the bridge arm transformation unit is used as the lower bridge arm transformation unit, when the AC voltage output is a positive half-wave, one set of the device cascade structure S1n is turned on, and the other set of device cascade structure S2n is turned off, The sub-module cascade structure SMn outputs the DC voltage Vd/2, which is used to support the negative DC voltage; when the AC voltage output is a negative half-wave, one set of the device cascade structure S1n is turned off, and the other set of the device cascade structure S2n is turned on. The sub-module cascade structure SMn outputs the difference Vd/2+Uc between the AC voltage and the DC negative voltage, which is used to support the AC voltage. 5. A control method of a high-voltage AC-DC electric energy conversion device as claimed in claim 3, wherein, when the bridge arm conversion unit is used as the upper bridge arm conversion unit in the composition mode 3), when the AC voltage output is a positive half During the wave, one set of device cascade structure S1p is turned on, the other set of device cascade structure S2p is turned off, and the sub-module cascade structure outputs the difference between the DC positive voltage and the AC voltage Vd/2-Uc, which is used to support the AC voltage ; When the AC voltage output is a negative half-wave, the other group of device cascade structure S2p is turned on, one of the device cascade structure S1p is turned off, and the sub-module cascade structure outputs the absolute value of AC voltage |Uc|, which is used to support AC voltage; For composition mode 3), when the bridge arm transformation unit is used as the lower bridge arm transformation unit, when the AC voltage output is a positive half-wave, one set of device cascade structure S1n is turned on, and the other set of device cascade structure S2n is turned off, The sub-module cascade structure SMn outputs the AC voltage Uc, which is used 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 between the AC voltage and the DC negative voltage Vd/2+Uc, used to support AC voltage.