WO2022213525A1

WO2022213525A1 - Ac-ac converter

Info

Publication number: WO2022213525A1
Application number: PCT/CN2021/112550
Authority: WO
Inventors: 邓占锋; 赵国亮; 葛菁; 于弘洋
Original assignee: 全球能源互联网研究院有限公司; 国家电网有限公司
Priority date: 2021-04-07
Filing date: 2021-08-13
Publication date: 2022-10-13
Also published as: CN113098295A

Abstract

Embodiments of the present application disclose an AC-AC converter, comprising: a first voltage conversion apparatus, a first end of which is connected to a first AC system; a second voltage conversion apparatus, a first end of which is connected to a second AC system; a frequency conversion apparatus, which is separately connected to a second end of the first voltage conversion apparatus and a second end of the second voltage conversion apparatus, wherein the voltage conversion ratio of the first voltage conversion apparatus is determined according to the capacity of the frequency conversion apparatus, the maximum through-current capability of a device, and the voltage of the first AC system, and the voltage conversion ratio of the second voltage conversion apparatus is determined according to the capacity of the frequency conversion apparatus, the maximum through-current capacity of the device, and the voltage of a second power grid.

Description

an alternating current converter

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on the Chinese patent application with the application number of 202110374367.X and the application date of April 7, 2021, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby incorporated by reference. Application.

technical field

The present application relates to the field of smart grids, and in particular, to an AC converter.

Background technique

With the development of the national economy, the demand for electric energy continues to increase, and the requirements for the power transmission capacity of the power grid are getting higher and higher. In the power transmission process of the power grid, the AC converter is a particularly important electronic power device. .

The electronic power devices in the existing AC converters generally include converters, and the converters are generally directly connected to the power transmission grid. Therefore, the normal input voltage to the converter is relatively large, resulting in a relatively small operating current carried by the converter itself. , which in turn leads to a lower use efficiency of the converter.

SUMMARY OF THE INVENTION

In view of this, the embodiment of the present application provides an AC converter to solve the problem that the voltage input to the converter is normally large, resulting in a small current carried by the converter itself, which in turn leads to a low use efficiency of the converter The problem.

An embodiment of the present application provides an AC converter, comprising: a first voltage conversion device, the first end of which is connected to the first AC system; the second voltage conversion device, the first end of which is connected to the second AC system; and a frequency conversion device, are respectively connected to the second end of the first voltage conversion device and the second end of the second voltage conversion device; wherein, the voltage transformation ratio of the first voltage conversion device is based on the capacity of the frequency conversion device, the device The maximum current capacity and the voltage of the first AC system are determined; the transformation ratio of the second voltage conversion device is determined according to the capacity of the frequency conversion device, the maximum current capacity of the device, and the voltage of the second AC system.

In some optional embodiments, the first end of the first voltage conversion device is an input end and the second end is an output end; or, the second end of the second voltage conversion device is an input end and the first end is an output end.

In some optional embodiments, when the first end of the first voltage conversion device is the input end and the second end is the output end: the first voltage conversion device is configured to obtain the first voltage input by the first AC system , convert the first voltage into a second voltage, the amplitude of the second voltage is less than or equal to the amplitude of the first voltage; the frequency conversion device is configured to convert the second voltage into a third voltage, the frequency of the third voltage is less than or equal to the frequency of the second voltage; the second voltage conversion device is configured to convert the third voltage into a fourth voltage, the third voltage The magnitude of is less than or equal to the magnitude of the fourth voltage;

Or; when the second end of the second voltage conversion device is the input end and the first end is the output end: the second voltage conversion device is configured to obtain the fourth voltage input by the second AC system, and the The fourth voltage is converted into a third voltage, and the amplitude of the third voltage is less than or equal to the amplitude of the fourth voltage; the frequency conversion device is configured to convert the third voltage into the second voltage, The frequency of the third voltage is less than or equal to the frequency of the second voltage; the first voltage conversion device is configured to convert the second voltage into a first voltage, and the amplitude of the second voltage is less than or equal to the magnitude of the first voltage.

In some optional embodiments, the transformation ratio of the first voltage transformation device is based on the input voltage of the frequency transformation device determined based on the capacity of the frequency transformation device and the maximum current capacity of the device, and the first The voltage of an AC system is determined.

In some optional embodiments, the transformation ratio of the second voltage transformation device is based on the output voltage of the frequency transformation device determined based on the capacity of the frequency transformation device and the maximum current capacity of the device, and the first 2. The voltage of the AC system is determined.

In some optional embodiments, the topology of the frequency conversion module includes a matrix topology, a series combination topology or a parallel combination topology based on multiple cascaded frequency conversion modules.

In some optional embodiments, the first voltage conversion device and the second voltage conversion device respectively include: a single three-phase transformer or three single-phase transformers, the single three-phase transformer and the three single-phase transformers The phase transformers respectively include three-winding transformers or double-winding transformers, the three single-phase transformers are independent of each other, and the three single-phase transformers are respectively connected to the A-phase voltage, B-phase voltage, and C-phase voltage of the first AC system. voltage connection.

In some optional embodiments, when the single-phase transformer or the three-phase transformer is the double-winding transformer, the input windings are in a star connection or delta connection, and the output windings are in a star connection or Delta connection mode; when the output end winding is in the star connection mode, the grounding mode of the output end winding is determined according to the target requirements, and the grounding modes include: direct grounding mode, grounding mode via target coil, grounding mode via target coil Resistance grounding method or non-grounding method;

In some optional embodiments, when the single-phase transformer or the three-phase transformer is the three-winding transformer, the input windings are in a star connection or delta connection, and the output windings are in a star connection or In delta connection mode, the third winding is in delta connection mode, and the first end or the second end of the third winding is grounded; when the output end winding is in the star connection mode, the output end is determined according to the target requirements The grounding method of the winding includes: direct grounding method, grounding method through target coil, grounding method through target resistance or non-grounding method.

In some optional embodiments, the first voltage conversion device is further configured to isolate the fault current of the first AC system; the second voltage conversion device is further configured to isolate the fault current of the second AC system.

An AC converter provided by an embodiment of the present application includes: a first voltage conversion device, the first end of which is connected to the first AC system; the second voltage conversion device, the first end of which is connected to the second AC system, the first AC system The frequency is different from that of the second AC system; the frequency conversion device is respectively connected to the second end of the first voltage conversion device and the second end of the second voltage conversion device; wherein, the voltage transformation ratio of the first voltage conversion device is based on the frequency conversion device. The capacity of the frequency conversion device, the maximum current capacity of the device, and the voltage of the first AC system are determined; the transformation ratio of the second voltage conversion device is determined according to the capacity of the frequency conversion device, the maximum current capacity of the device, and the voltage of the second AC system.

By implementing the embodiment of the present application, combining the capacity of the frequency conversion device, the maximum current capacity of the device, and the voltage of the power grid to determine the transformation ratio of the voltage conversion device, the voltage value input into the frequency conversion device can be controlled, thereby improving the frequency conversion The use efficiency of the device realizes the bidirectional flow of electric energy between the two power grids.

Description of drawings

In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the accompanying drawings that need to be used in the description of the specific embodiments or the prior art will be briefly introduced below. The drawings are some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of an AC/AC converter in an embodiment of the present application;

2 is a schematic diagram of a matrix topology structure of an intermediate frequency conversion device of an AC-AC converter in an embodiment of the present application;

3 is a schematic diagram of a series combination topology structure of an AC-AC converter frequency conversion device in an embodiment of the present application;

FIG. 4 is a schematic diagram of a parallel combination topology structure of an AC/AC converter in an embodiment of the present application.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

An embodiment of the present application provides an AC converter, which can be applied to a specific application scenario of AC power transmission in a power system. As shown in FIG. 1 , the AC converter includes: a first voltage conversion device 200, a second voltage converter Transforming device 400 and frequency transforming device 300; wherein,

The first voltage conversion device 200, the first end of which is connected to the first AC system 100; in this embodiment, the first AC system 100 may be at least one of a substation, a power station, and a distribution station set on land , or at least one of a substation, a power station, and a distribution station set on the sea surface to provide AC power for electrical equipment, and the AC power may be power frequency high-voltage power. Exemplarily, the first voltage transformation device 200 is a passive voltage transformation device, which is used to realize the amplitude transformation of the same frequency voltage.

The first end of the second voltage conversion device 400 is connected to the second AC system 500; in this embodiment, the second AC system 500 may be a substation installed on land, or at least one of a power station and a power distribution station First, it can also be at least one of a substation, a power station, and a distribution station set on the sea, which is used to provide AC power for electrical equipment, and the AC power can be power frequency high-voltage power. Exemplarily, the second voltage transformation device 400 is a passive voltage transformation device, which is used to realize the amplitude transformation of the same frequency voltage.

The frequency conversion device 300 is respectively connected to the second end of the first voltage conversion device 200 and the second end of the second voltage conversion device 400; in this embodiment, the frequency conversion device 300 is an active frequency conversion device 300, which are respectively connected with The first voltage conversion device 200 is connected to the second voltage conversion device 400 .

The transformation ratio of the first voltage conversion device 200 is determined according to the capacity of the frequency conversion device 300 , the maximum current capacity of the device, and the voltage of the first AC system 100 .

In this embodiment, the capacity of the frequency conversion device 300 is used to represent the maximum electrical energy that the frequency conversion device 300 can carry, and the unit is MVA; the maximum current capacity of the device is used to represent the maximum current used by the frequency conversion device 300 , the maximum use current of the frequency conversion device 300 can be determined according to user requirements, and can be set to 50%-80% of the continuous collector current. Therefore, the maximum use current of the frequency conversion device can be set to 50%-80% of the continuous current of the collector according to the actual working conditions of the device and the continuous current of the collector.

Exemplarily, the input voltage of the frequency conversion device 300 may be determined according to the capacity of the frequency conversion device 300 and the maximum current capacity of the device, and the first voltage conversion device 200 may be determined according to the input voltage and the voltage of the first AC system 100 . transformation ratio.

In this embodiment, the transformation ratio of the second voltage conversion device 400 is determined according to the capacity of the frequency conversion device 300 , the maximum current capacity of the device, and the voltage of the second AC system 500 . Exemplarily, the output voltage of the frequency conversion device 300 may be determined according to the capacity of the frequency conversion device 300 and the maximum current capacity of the device, and the second voltage conversion device 400 may be determined according to the output voltage and the voltage of the second AC system 500 . transformation ratio.

An AC converter provided by the present application includes: a first voltage conversion device 200, the first end of which is connected to the first AC system 100; the second voltage conversion device 400, the first end of which is connected to the second AC system 500, the first The frequency of the AC system 100 is different from that of the second AC system 500; the frequency conversion device 300 is connected to the second end of the first voltage conversion device 200 and the second end of the second voltage conversion device 400 respectively; wherein, the first voltage conversion device 200 The transformation ratio of the frequency transformation device 300 is determined according to the capacity of the frequency transformation device 300, the maximum current flow capacity of the device, and the voltage of the first AC system 100; the transformation ratio of the second voltage transformation device 400 is determined according to the capacity of the frequency transformation device 300, the maximum flow through the device capacity, and the voltage of the second AC system 500 is determined.

By implementing the present application, combining the capacity of the frequency conversion device 300, the maximum current capacity of the device, and the voltage of the power grid to determine the transformation ratio of the voltage conversion device, the voltage value input to the frequency conversion device 300 can be controlled, that is to say, Through the transformation ratio of the first voltage conversion device and the second voltage conversion device calculated in the above manner, the input voltage of the frequency conversion device can be controlled, the current in the frequency conversion device can be adjusted, and the use efficiency of the frequency conversion device 300 can be improved. For bidirectional flow of electrical energy between two power grids, the AC-AC converter provided by the embodiment of the present application has no common DC link, and can realize direct AC-AC conversion of the frequency or voltage of the AC systems on both sides.

In an optional embodiment, the topology of the AC converter is as follows: the first terminal of the first voltage conversion device 200 is the input terminal, and the second terminal is the output terminal.

In this embodiment, when the first end of the first voltage conversion device 200 is the input end and the second end is the output end, at this time, the transmission direction of the AC power in the system may flow from the first AC system 100 to the second Two AC system 500. The first AC system 100 may be an AC power grid of power frequency high-voltage power output in actual production and life, and the second AC system 500 may be a low-frequency AC power grid for supplying power to low-frequency equipment. In this case, the power supply of the first AC system 100 The high-frequency power can realize voltage amplitude transformation through the first voltage transformation device 200, and then realize the voltage-frequency transformation through the frequency transformation device 300, and finally realize the voltage amplitude transformation through the second voltage transformation device 400, and then flow into the second AC system. 500 , realize the flow of alternating current power from the first alternating current system 100 to the second alternating current system 500 , and realize the conversion between power frequency alternating current and low frequency alternating current.

In an optional embodiment, the topology of the AC converter is as follows: the second terminal of the second voltage conversion device 400 is an input terminal, and the first terminal is an output terminal.

In this embodiment, when the second terminal of the second voltage conversion device 400 is the input terminal and the first terminal is the output terminal, the transmission direction of the AC power in the system may be from the second AC system 500 to the first terminal. An AC system 100. The second AC system 500 can be a low-frequency wind farm that directly outputs low-frequency AC power; that is, the power-frequency high-voltage power of the second AC system 500 can realize voltage amplitude conversion through the second voltage conversion device 400, and then pass through the frequency conversion device. 300 realizes voltage frequency conversion, and finally realizes voltage amplitude conversion through the first voltage conversion device 200 , and then flows into the first AC system 100 to realize the flow of AC power from the second AC system 500 to the first AC system 100 .

The AC converter provided by the embodiment of the present application, combined with the input and output terminals of the first voltage conversion device 200 and the second voltage conversion device 400 determined according to actual needs, can realize the bidirectional flow of AC power, which can be from the first AC system. 100 flows to the second AC system 500 , and may also flow from the second AC system 500 to the first AC system 100 .

In an optional embodiment, when the first end of the first voltage conversion device 200 is the input end and the second end is the output end:

The first voltage conversion device 200 is configured to obtain a first voltage input by the first AC system 100 and convert the first voltage into a second voltage. In this embodiment, the first voltage input by the first alternating current system 100 may be power frequency high voltage power. For example, it may be a power frequency high-voltage electricity with a voltage amplitude of 220kv and a frequency of 50Hz. Optionally, the amplitude of the first voltage and the amplitude of the second voltage may be different, and the frequency of the first voltage and the frequency of the second voltage may be the same. For example, the second voltage may have a voltage amplitude of 60kv and a frequency of 50Hz. Power frequency low voltage electricity.

Optionally, when the transformation ratio k of the first voltage transformation device 200 is 1, at this time, the amplitude of the first voltage is the same as the amplitude of the second voltage. That is to say, after the electrical energy input by the first AC system 100 passes through the first voltage conversion device 200, the second voltage obtained by conversion has the same frequency as the input first voltage, and the voltage amplitude may be the same or different.

The frequency conversion device 300 is configured to convert the second voltage of the first voltage conversion device 200 into a third voltage.

In this embodiment, the output terminal of the first voltage conversion device 200 is connected to the frequency conversion device 300 , that is, the frequency conversion device 300 receives the second voltage input from the first voltage conversion device 200 , and the voltage amplitude may be 60kv 2. Power frequency low-voltage power with a frequency of 50Hz, the frequency conversion device 300 converts the second voltage into a third voltage, and the third voltage can be a low-frequency low-voltage power with a voltage amplitude of 60kv and a frequency of 15Hz, that is, the frequency conversion The device 300 is used to transform the frequency of the input electrical energy.

Optionally, when adjusting the control strategy in the frequency conversion device 300, the voltage amplitude of the second voltage and the voltage amplitude of the third voltage may be the same or different; the frequency of the second voltage and the frequency of the third voltage may be The same or different.

The second voltage conversion device 400 is configured to convert the third voltage adjusted by the frequency conversion device 300 into a fourth voltage. In this embodiment, the third voltage input by the frequency conversion device 300 to the second voltage conversion device 400 may be low-frequency low-voltage electricity. For example, it can be AC power with a voltage amplitude of 60kv and a frequency of 15Hz. Optionally, the amplitude of the third voltage may be different from the amplitude of the fourth voltage, and the frequency of the third voltage may be the same as the frequency of the fourth voltage. For example, the fourth voltage may have a voltage amplitude of 220kv and a frequency of 15Hz. Low frequency high voltage electricity.

Optionally, when the transformation ratio of the second voltage transformation device 400 is k=1, at this time, the amplitude of the third voltage is the same as the amplitude of the fourth voltage. That is to say, after the electrical energy input by the frequency conversion device 300 passes through the second voltage conversion device 400, the third voltage obtained by conversion has the same frequency as the input fourth voltage, and the voltage amplitudes may be the same or different.

In an optional embodiment, when the second terminal of the second voltage conversion device 400 is the input terminal and the first terminal is the output terminal:

The second voltage conversion device 400 is configured to obtain a fourth voltage input from the second AC system 500 and convert the fourth voltage into a third voltage. In this embodiment, the input from the second AC system 500 to the second voltage conversion device 400 may be power frequency high-voltage power with a voltage amplitude of 220 kV and a frequency of 15 Hz, and the second voltage conversion device 400 is used to convert the input power. voltage amplitude. Optionally, the power frequency high-voltage power with a voltage amplitude of 220kv and a frequency of 15Hz can be converted into a low-frequency low-voltage power with a voltage amplitude of 60kv and a frequency of 15Hz, that is, the amplitude of the fourth voltage is equal to the third voltage. Amplitudes can vary.

Optionally, when the transformation ratio of the second voltage transformation device 400 is k=1, at this time, the amplitude of the third voltage is the same as the amplitude of the fourth voltage. That is to say, after the electrical energy input by the second AC system 500 passes through the second voltage conversion device 400, the third voltage obtained by conversion has the same frequency as the input fourth voltage, and the voltage amplitudes may be the same or different.

The frequency conversion device 300 is configured to convert the third voltage into the second voltage;

In this embodiment, the output end of the second voltage conversion device 400 is connected to the frequency conversion device 300 , that is, the frequency conversion device 300 receives the third voltage input from the second voltage conversion device 400 , and the voltage amplitude may be 60kv , a low-frequency low-voltage power with a frequency of 15Hz, the frequency conversion device 300 converts the third voltage into a second voltage, and the second voltage can be a power-frequency low-voltage power with a voltage amplitude of 60kv and a frequency of 50Hz, that is, the frequency conversion The device 300 is used to transform the frequency of the input electrical energy.

Optionally, when adjusting the topology in the frequency conversion device 300, the voltage amplitude of the second voltage and the voltage amplitude of the third voltage may be the same or different; the frequency of the second voltage and the frequency of the third voltage Can be the same or different.

The first voltage conversion device 200 is configured to convert the second voltage into the first voltage. In this embodiment, the second voltage input by the frequency conversion device 300 to the first voltage conversion device 200 may be low-voltage power at power frequency. For example, it may be AC power with a voltage amplitude of 60kv and a frequency of 50Hz. Optionally, the amplitude of the second voltage may be different from the amplitude of the transformed first voltage, and the frequency of the second voltage may be the same as the frequency of the first voltage. 50Hz power frequency high voltage;

Optionally, when the transformation ratio of the second voltage transformation device 400 is k=1, at this time, the amplitude of the second voltage is the same as the amplitude of the first voltage. That is, after the electrical energy input by the frequency conversion device 300 passes through the first voltage conversion device 200 , the first voltage obtained by conversion has the same frequency as the input second voltage, and the voltage amplitudes may be the same or different.

As an optional embodiment of the present application, the transformation ratio of the first voltage transformation device 200 is based on the input voltage of the frequency transformation device 300 determined based on the capacity of the frequency transformation device 300 and the maximum current capacity of the device, and the first AC system The voltage of 100 is determined.

In this embodiment, the capacity of the frequency conversion device 300 may be the maximum power capacity that the device can carry. Optionally, the capacity of the frequency conversion device 300 may be determined according to the capacity of the first AC system 100; the device of the frequency conversion device 300 has the largest The current-carrying capacity can be the maximum current used to characterize the frequency conversion device 300; and then the input voltage of the frequency conversion device 300 can be determined according to the maximum current capacity and capacity of the device of the frequency conversion device 300; The conversion device 200 is connected, and the first AC system 100 is also connected to the first voltage conversion device 200 . Therefore, the transformation ratio of the first voltage conversion device 200 is determined by the input voltage and output voltage of the first voltage conversion device 200 . That is, the transformation ratio of the first voltage conversion device 200 is determined according to the input voltage of the frequency conversion device 300 and the voltage of the first AC system 100 . Exemplarily, the transformation ratio K1 of the first voltage transformation device can be determined by the following formula:

K1=U1/U2;

Wherein, U1 is the input voltage of the frequency conversion device 300 , and U2 is the voltage of the first AC system 100 .

U1=P/I;

Among them, P represents the capacity of the frequency conversion device 300 , and I represents the maximum current capacity of the device of the frequency conversion device 300 .

As an optional embodiment of the present application, the transformation ratio of the second voltage transformation device 400 is based on the output voltage of the frequency transformation device 300 determined based on the capacity of the frequency transformation device 300 and the maximum current capacity of the device, and the second AC system The voltage of 500 is determined.

In this embodiment, the capacity of the frequency conversion device 300 may be the maximum electrical energy capacity that the device can carry. Optionally, the capacity of the frequency conversion device 300 may be determined according to the capacity of the second AC system 500; the device of the frequency conversion device 300 has the largest capacity. The current-carrying capacity can be the maximum current used to characterize the frequency conversion device 300; and then the input voltage of the frequency conversion device 300 can be determined according to the maximum current capacity and capacity of the device of the frequency conversion device 300; The conversion device 400 is connected, and the second AC system 500 is also connected to the second voltage conversion device 400. Therefore, the transformation ratio of the second voltage conversion device 400 is determined by the input voltage and output voltage of the second voltage conversion device 400, That is, the transformation ratio of the second voltage conversion device 400 is determined according to the input voltage of the frequency conversion device 300 and the voltage of the second AC system 500 . Exemplarily, the transformation ratio K2 of the second voltage transformation device can be determined by the following formula:

K2=U3/U4;

Wherein, U3 is the output voltage of the frequency conversion device 300 , and U4 is the voltage of the second AC system 500 .

U3=P/I;

In the AC converter provided by the embodiment of the present application, the voltages of the input side and the output side of the frequency conversion device 300 can be adjusted by selecting the transformation ratio of the transformer, thereby improving the current flow of the converter device in the frequency conversion device 300 utilization, optimize the key parameters such as the converter module, and reduce the overall cost of the AC converter.

As an optional implementation manner of the present application, the topology of the frequency conversion module includes, but is not limited to, a matrix topology, a series combination topology or a parallel combination topology based on multiple cascaded frequency conversion modules.

Exemplarily, as shown in FIG. 2 , it is a matrix topology structure of a frequency conversion module, wherein A represents the A-phase voltage, B represents the B-phase voltage, and C represents the C-phase voltage. As shown in Figure 3, it is a series combination topology of frequency conversion modules, wherein A represents the A-phase voltage, B represents the B-phase voltage, and C represents the C-phase voltage. The H-bridge series structure includes a plurality of H-bridge structures connected in series. As shown in FIG. 4 , it is a parallel combination topology of frequency conversion modules, wherein A represents the A-phase voltage, B represents the B-phase voltage, and C represents the C-phase voltage. The H-bridge parallel structure includes a plurality of H-bridge structures connected in parallel.

As an optional implementation manner of the present application, the first voltage conversion device 200 and the second voltage conversion device 400 respectively include: a single three-phase transformer or three single-phase transformers, the single three-phase transformer and all The three single-phase transformers respectively include three-winding transformers or double-winding transformers, the three single-phase transformers are independent of each other, and the three single-phase transformers are respectively connected to the A-phase voltage and B-phase voltage of the first AC system 100 . , C-phase voltage is connected.

In this embodiment, the first voltage conversion device 200 and the second voltage conversion device 400 may each include one three-phase transformer, or may also include three single-phase transformers. The three-phase transformer and the single-phase transformer Transformers can be selected three-winding transformer structure or two-winding transformer structure. When the voltage conversion device selects three single-phase transformers, the three single-phase transformers are independent of each other, and the three single-phase transformers are respectively connected with the A-phase voltage, B-phase voltage, and C-phase voltage of the AC grid.

As an optional implementation manner of the present application, when the single-phase transformer or the three-phase transformer is the double-winding transformer, the input windings are connected in star or delta connection, and the output windings are star connected way or delta connection;

When the output winding is in the star connection mode, the grounding mode of the output winding is determined according to the target requirement, and the grounding mode includes: direct grounding, grounding via target coil, grounding via target resistance, or Ungrounded method.

As an optional implementation manner of the present application, when the single-phase transformer or the three-phase transformer is the three-winding transformer, the input windings are in a star connection or delta connection, and the output windings are in a star connection. mode or delta connection mode, the third winding is in a delta connection mode, and the first end or the second end of the third winding is grounded;

The AC converter provided by the embodiment of the present application can provide a reliable grounding point for a system and a device, and cooperate with the grounding mode of the whole system, thereby effectively reducing the requirement on the insulation level of the system.

As an optional implementation manner of the present application, the first voltage conversion device 200 is further configured to isolate the fault current of the first AC system 100; the second voltage conversion device 400 is further configured to isolate the fault current of the second AC system 500, which can be isolated When a fault occurs on the input side of the AC grid, the fault current flowing into the frequency conversion part reduces the impact on the converter.

Obviously, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation manner. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. And the obvious changes or changes derived from this are still within the scope of protection created by the present application.

Claims

An alternating current converter, the alternating current converter includes:

a first voltage conversion device, the first end of which is connected to the first AC system;

a second voltage conversion device, the first end of which is connected to the second AC system;

a frequency conversion device, respectively connected to the second end of the first voltage conversion device and the second end of the second voltage conversion device;

Wherein, the transformation ratio of the first voltage conversion device is determined according to the capacity of the frequency conversion device, the maximum current capacity of the device, and the voltage of the first AC system;

The transformation ratio of the second voltage conversion device is determined according to the capacity of the frequency conversion device, the maximum current capacity of the device, and the voltage of the second AC system.
The interleaver of claim 1, wherein,

The first end of the first voltage conversion device is an input end, and the second end is an output end;

Or, the second end of the second voltage conversion device is the input end, and the first end is the output end.
The interleaver of claim 2, wherein,

When the first end of the first voltage conversion device is the input end and the second end is the output end:

The first voltage conversion device is configured to obtain a first voltage input by the first AC system, and convert the first voltage into a second voltage, the amplitude of the second voltage being less than or equal to the first voltage the magnitude of the voltage;

The frequency conversion device is configured to convert the second voltage into a third voltage, the frequency of the third voltage being less than or equal to the frequency of the second voltage;

a second voltage transforming device, configured to transform the third voltage into a fourth voltage, the amplitude of the third voltage being less than or equal to the amplitude of the fourth voltage;

Or; when the second end of the second voltage conversion device is the input end and the first end is the output end:

The second voltage conversion device is configured to obtain a fourth voltage input from the second AC system, and convert the fourth voltage into a third voltage, where the amplitude of the third voltage is less than or equal to the fourth voltage the magnitude of the voltage;

The frequency conversion device is configured to convert the third voltage into a second voltage, the frequency of the third voltage is less than or equal to the frequency of the second voltage;

The first voltage conversion device is configured to convert the second voltage into a first voltage, and the amplitude of the second voltage is less than or equal to the amplitude of the first voltage.
The AC converter according to claim 1, wherein the transformation ratio of the first voltage conversion device is based on the input voltage of the frequency conversion device determined based on the capacity of the frequency conversion device and the maximum current capacity of the device , and the voltage of the first AC system is determined.
The AC converter according to claim 1, wherein the transformation ratio of the second voltage conversion device is based on the output voltage of the frequency conversion device determined based on the capacity of the frequency conversion device and the maximum current capacity of the device, And the voltage of the second AC system is determined.
The AC-AC converter according to claim 1, wherein the frequency conversion module, its topology structure comprises a matrix topology, a series combination topology or a parallel combination topology based on a plurality of cascaded frequency conversion modules.
The AC converter according to claim 1, wherein the first voltage conversion device and the second voltage conversion device respectively comprise: a single three-phase transformer or three single-phase transformers, the single three-phase transformer and The three single-phase transformers respectively include three-winding transformers or double-winding transformers, the three single-phase transformers are independent of each other, and the three single-phase transformers are respectively connected to the A-phase voltage and B-phase voltage of the first AC system. Phase voltage and C-phase voltage are connected.
The AC converter according to claim 7, wherein when the single-phase transformer or the three-phase transformer is the double-winding transformer, the input winding is in a star connection or a delta connection, and the output winding is Star connection or delta connection;

When the output winding is in the star connection mode, the grounding mode of the output winding is determined according to the target requirements, and the grounding mode includes: direct grounding, grounding via target coil, grounding via target resistance, or Ungrounded method.
The AC converter according to claim 7, wherein when the single-phase transformer or the three-phase transformer is the three-winding transformer, the input winding is in a star connection or a delta connection, and the output winding is Star connection mode or delta connection mode, the third winding is delta connection mode, and the first end or the second end of the third winding is grounded;

When the output winding is in the star connection mode, the grounding mode of the output winding is determined according to the target requirements, and the grounding mode includes: direct grounding, grounding via target coil, grounding via target resistance, or Ungrounded method.
The AC converter of claim 1, wherein the first voltage conversion device is further configured to isolate a fault current of the first AC system; the second voltage conversion device is further configured to isolate the second AC system fault current of the system.