A kind of AC-AC converter and power system

Abstract

The present invention discloses an AC-AC inverter and an electric power system. The AC-AC inverter comprises: a plurality of frequency conversion devices consisting of a plurality of chain-level energy dissipation devices and a plurality of bridge arms, the input end of each bridge arm is correspondingly connected to a single-phase AC bus of a first AC system, the output end of each bridge arm is connected to the same-phase AC bus of a second AC system, each-phase AC bus of the first AC system and the second AC system is connected to a system-level energy dissipation device, the bridge arm is composed of a plurality of cascade-connected frequency conversion modules, the frequency conversion module is composed of a module-level energy dissipation device and a frequency conversion circuit connected in parallel, the system-level energy dissipation device is used to discharge the redundant electric energy on the AC side of the first AC system and the second AC system, the module-level energy dissipation device is used to discharge the redundant electric energy of the frequency conversion circuit, thereby realizing system-level and module-level energy dissipation, and further improving the safety of the AC-AC inverter.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to an AC-AC converter and an electric power system. Background Art

[0002] Energy is an important material basis for economic and social development. Accelerating the establishment of a safe, reliable, economically efficient, clean and environmentally friendly modern energy supply system has become a common strategic goal of all countries in the world. In order to effectively solve the problems of energy depletion and environmental pollution, the development of new energy has become the only way to cope with the three major challenges of energy security, environmental pollution and climate change and achieve sustainable development of human society. Wind power generation is one of the most mature and large-scale development methods in new energy power generation technology. In some areas, the distribution of wind power resources and load centers are reversely distributed, and large-capacity long-distance power transmission is required to achieve optimal allocation of resources. In order to realize the low-frequency power transmission function, the existing power transmission system usually sets a frequency conversion device on the power frequency side of the AC power grid. The frequency conversion device obtains electric energy through the AC power grid on the power frequency side. However, if the energy of the AC power grid on the power frequency side or the AC power grid on the low frequency side is overshot, or the energy of the frequency conversion device is overshot, it will cause damage to the AC power grid and the frequency conversion device on the power frequency side and the low frequency side. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that if the energy of the AC power grid on the industrial frequency side or the AC power grid on the low frequency side is overshot, or the energy of the frequency conversion device is overshot, it will cause damage to the AC power grid on the industrial frequency side or the low frequency side, and the frequency conversion device, thereby providing an AC-AC inverter and a power system.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, an embodiment of the present invention provides an AC-AC inverter, comprising: at least one frequency conversion device and multiple system-level energy dissipation devices, wherein the frequency conversion device comprises multiple bridge arms, the input end of each bridge arm is correspondingly connected to a single-phase AC bus of a first AC system, and the output end of each bridge arm is connected to the same-phase AC bus of a second AC system; each phase AC bus of the first AC system and the second AC system is connected to the system-level energy dissipation device; the bridge arm is composed of multiple cascade-connected frequency conversion modules, and the frequency conversion module is composed of module-level energy dissipation devices and frequency conversion circuits connected in parallel; the system-level energy dissipation device is used to discharge excess electric energy on the AC side of the first AC system and the second AC system; the module-level energy dissipation device is used to discharge excess electric energy of the frequency conversion circuit.

[0006] In one embodiment, the AC-AC converter further includes: a plurality of chain-level energy dissipation devices, each of which is connected in parallel with a bridge arm to discharge excess electrical energy of the bridge arm.

[0007] In one embodiment, the AC-AC converter further includes: for each frequency conversion device, the input end of each bridge arm is correspondingly connected to a phase AC bus of the first AC system through a switch module, and / or the output end of each bridge arm is connected to the same AC bus of the second AC system through a switch module.

[0008] In one embodiment, the system-level energy dissipation device includes: a plurality of lightning arresters connected in parallel or in series, or a plurality of resistors connected in series in sequence.

[0009] In one embodiment, the chain-level energy dissipation device includes: a plurality of lightning arresters connected in parallel or in series, or a plurality of resistors connected in series in sequence.

[0010] In one embodiment, the module-level energy dissipation device includes: a plurality of lightning arresters connected in parallel or in series, or a plurality of resistors connected in series in sequence.

[0011] In one embodiment, the frequency conversion circuit is a full-bridge structure, which includes two groups of switching device bridge arms and a DC capacitor. The two groups of switching device bridge arms are connected in parallel, each group of switching device bridge arms includes two switching devices connected in series, and the DC capacitor is connected in parallel with the two groups of switching device bridge arms.

[0012] In one embodiment, the frequency conversion circuit is a half-bridge structure, which includes a group of switching device bridge arms and a DC capacitor. The group of switching device bridge arms includes two power electronic devices connected in series, and the DC capacitor is connected in parallel with the switching device bridge arms.

[0013] In a second aspect, an embodiment of the present invention provides an electric power system, comprising: the AC-AC converter of the first aspect, a first AC system and a second AC system, wherein the input end of each bridge arm of each frequency conversion device of the AC-AC converter is correspondingly connected to a single-phase AC bus of the first AC system, and the output end of each bridge arm is connected to the same-phase AC bus of the second AC system; the AC-AC converter is used to convert a first-frequency three-phase voltage of the first AC system into a second-frequency three-phase voltage, and transmit the second-frequency three-phase voltage to the second AC system.

[0014] In one embodiment, the first AC system includes: a distribution station, and / or a power station, and / or a transformer substation, and / or a new energy power generation base.

[0015] In one embodiment, the second AC system includes: a plurality of offshore wind power plants, and / or a plurality of offshore solar power plants, and / or a plurality of offshore tidal power plants.

[0016] The technical solution of the present invention has the following advantages:

[0017] 1. The AC-AC inverter provided by the present invention comprises a plurality of chain-level energy dissipation devices and a plurality of bridge arms, the input end of each bridge arm is correspondingly connected to a single-phase AC bus of a first AC system, the output end of each bridge arm is connected to the same-phase AC bus of a second AC system, each-phase AC bus of the first AC system and the second AC system is connected to a system-level energy dissipation device, the bridge arm is composed of a plurality of cascade-connected frequency conversion modules, the frequency conversion module is composed of a module-level energy dissipation device and a frequency conversion circuit connected in parallel, the system-level energy dissipation device is used to discharge the excess electric energy on the AC side of the first AC system and the second AC system, and the module-level energy dissipation device is used to discharge the excess electric energy of the frequency conversion circuit, thereby realizing system-level and module-level energy dissipation, and further improving the safety of the AC-AC inverter.

[0018] 2. In the cross-converter provided by the present invention, each bridge arm is connected in parallel with a chain-level energy dissipation device. When a bridge arm fails, the chain-level energy dissipation device is closed to eliminate excess electrical energy on the bridge arm, thereby achieving chain-level energy dissipation.

[0019] 3. In the power system provided by the present invention, the AC-AC inverter converts the three-phase voltage of the first frequency of the first AC system into a three-phase voltage of the second frequency. The AC-AC inverter includes a system-level energy dissipation device, a chain-level energy dissipation device and a module-level energy dissipation device, thereby effectively suppressing energy overshoot between the two AC systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A composition diagram of a specific example of a cross-converter provided in an embodiment of the present invention;

[0022] Figure 2 A composition diagram of another specific example of a cross-converter provided in an embodiment of the present invention;

[0023] Figure 3 A composition diagram of another specific example of a cross-converter provided in an embodiment of the present invention;

[0024] Figure 4 A circuit diagram of a specific example of a frequency conversion circuit provided by an embodiment of the present invention;

[0025] Figure 5 A circuit diagram of another specific example of a frequency conversion circuit provided by an embodiment of the present invention;

[0026] Figure 6 A composition diagram of another specific example of a cross-converter provided in an embodiment of the present invention;

[0027] Figure 7 A composition diagram of a specific example of a power system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Example 1

[0033] The embodiment of the present invention provides a cycloconverter, which is applied to occasions where variable frequency power transmission is required, such as Figure 1 As shown, it includes: at least one frequency conversion device 1 and a plurality of system-level energy dissipation devices 2.

[0034] like Figure 2As shown, the frequency conversion device 1 includes multiple bridge arms 11, the input end of each bridge arm 11 is correspondingly connected to a phase AC bus of the first AC system #1, and the output end of each bridge arm 11 is connected to the same phase AC bus of the second AC system #2; each phase AC bus of the first AC system and the second AC system is connected to the system-level energy dissipation device 2; the bridge arm 11 is composed of multiple cascade-connected frequency conversion modules 111, and the frequency conversion module 111 is composed of a module-level energy dissipation device 1111 and a frequency conversion circuit 1112 connected in parallel.

[0035] Specifically, combined Figure 1 and Figure 2 It can be seen that the AC-AC inverter of the embodiment of the present invention is a nine-phase inverter, and a system-level energy dissipation device 2 is connected to each AC bus, and a module-level energy dissipation device 1111 is connected in parallel to each frequency conversion circuit 1112, wherein when the AC bus has no energy overshoot, the frequency conversion circuit 1112 has no fault, and the bridge arm 11 has no fault, the system-level energy dissipation device 2 and the module-level energy dissipation device 1111 are both in a disconnected state, and when the AC bus has energy overshoot, the system-level energy dissipation device 2 is closed to discharge the excess electric energy on the AC side of the first AC system and the second AC system, and when the frequency conversion circuit 1112 has a fault, the module-level energy dissipation device 1111 is closed to discharge the excess electric energy of the frequency conversion circuit 1112.

[0036] In addition, when the frequency conversion circuit 1112 fails or the bridge arm 11 fails, the module-level energy dissipation devices 1111 can be closed to discharge the excess electric energy of the bridge arm 11 and the frequency conversion circuit 1112, which is not limited here.

[0037] The AC-AC inverter of the embodiment of the present invention can convert a three-phase voltage of a first frequency of a first AC system into a three-phase voltage of a second frequency, wherein the first frequency can be less than the second frequency, and the range of the first frequency and the second frequency can be determined according to actual applications, thereby determining the operating state of each frequency conversion circuit 1112, and the operating state of the frequency conversion circuit 1112 is not limited to the switching frequency of the frequency conversion circuit 1112.

[0038] In a specific embodiment, if Figure 3 As shown, the cross-converter further includes: a plurality of chain-level energy dissipation devices 12, each chain-level energy dissipation device 12 is connected in parallel with a bridge arm 11, and when the bridge arm 11 fails, the chain-level energy dissipation device 12 can be closed to discharge excess electric energy.

[0039] In a specific embodiment, the system-level energy dissipation device 2, the chain-level energy dissipation device 12 and the module-level energy dissipation device 1111 of the embodiment of the present invention can have the same structure, and all three can include: multiple lightning arresters connected in parallel or series, or multiple resistors connected in series in sequence.

[0040] It should be noted that, in addition to the above-mentioned structures, the three energy dissipation devices in the embodiments of the present invention may also include other existing devices for reducing voltage and consuming electric energy, and the lightning arrester also used in the embodiments of the present invention may be a resistor type or a gap type, which is not limited here.

[0041] In a specific embodiment, if Figure 4 As shown, the frequency conversion circuit 1112 is a full-bridge structure, which includes two groups of switching device bridge arms and a DC capacitor. The two groups of switching device bridge arms are connected in parallel, and each group of switching device bridge arms includes two switching devices connected in series. The DC capacitor is connected in parallel with the two groups of switching device bridge arms.

[0042] In a specific embodiment, if Figure 5 As shown, the frequency conversion circuit 1112 is a half-bridge structure, which includes a group of switching device bridge arms and a DC capacitor. A group of switching device bridge arms includes two power electronic devices connected in series, and the DC capacitor is connected in parallel with the switching device bridge arms.

[0043] like Figure 4 and Figure 5 The switching device shown is an IGBT with an anti-parallel diode. In addition, the switching device in the embodiment of the present invention is not limited to IGBT, but can also be a controllable power electronic switching device such as MOSFET, GTR, GTO, etc., which is not limited here.

[0044] In a specific embodiment, if Figure 6 As shown, the AC-AC converter also includes: for each frequency conversion device 1, the input end of each bridge arm 11 is correspondingly connected to a single-phase AC bus of the first AC system through a switch module 3, and / or the output end of each bridge arm 11 is connected to the same AC bus of the second AC system through a switch module.

[0045] The switch module of the embodiment of the present invention can be a power electronic switch or a mechanical switch, and the switch module can be arranged at the input end and the output end of the bridge arm 11 at the same time, or only at the input end of the bridge arm 11, or only at the output end of the bridge arm 11, without limitation here.

[0046] Example 2

[0047] An embodiment of the present invention provides a power system, such as Figure 7 As shown, it includes: the AC-AC converter 4 of embodiment 1, the first AC system 5 and the second AC system 6.

[0048] like Figure 7As shown, the AC-AC inverter 4 of the embodiment of the present invention is a nine-phase inverter, the input end of each bridge arm 11 of each frequency conversion device 1 of the AC-AC inverter is correspondingly connected to a one-phase AC bus of the first AC system 5, and the output end of each bridge arm 11 is connected to the same-phase AC bus of the second AC system 6; the AC-AC inverter 4 is used to convert the first-frequency three-phase voltage of the first AC system 5 into a second-frequency three-phase voltage, and transmit the second-frequency three-phase voltage to the second AC system 6.

[0049] In a specific embodiment, the first AC system 5 includes: a distribution station, and / or a power station, and / or a transformer substation, and / or a new energy power generation base, and the second AC system 6 includes: multiple offshore wind power stations, and / or multiple offshore solar power stations, and / or multiple offshore tidal power stations.

[0050] Specifically, the new energy power generation base of the embodiment of the present invention is used to provide electric energy to the second AC system 6. The new energy power generation base here can be a plurality of offshore wind power stations and / or a plurality of solar power stations and / or a plurality of tidal power stations. Since the new energy power generation base belongs to renewable energy, which is inexhaustible, the comprehensive utilization of new energy such as wind energy, solar energy or tidal energy can reduce the consumption of other energy sources, and to a large extent, can save other energy sources. In addition, wind energy, solar energy or tidal energy are clean energy, which has less pollution to the environment and is conducive to ensuring the healthy life of residents. The second AC system 6 here is mainly a power station and / or a solar power station and / or a tidal power station set up at sea. Therefore, the new energy power generation base set up at sea can provide electric energy to the AC power grid set up on land, and can make full use of the new energy at sea, thereby saving more other electric energy.

[0051] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A cycloconverter, characterized in that: include: At least one frequency conversion device, a plurality of chain-level energy dissipation devices and a plurality of system-level energy dissipation devices, wherein: The frequency conversion device comprises a plurality of bridge arms, the input end of each bridge arm is correspondingly connected to a phase AC bus of the first AC system, and the output end of each bridge arm is connected to the same phase AC bus of the second AC system; Each phase AC bus of the first AC system and the second AC system is connected to a system-level energy dissipation device; The bridge arm is composed of a plurality of frequency conversion modules connected in cascade, and the frequency conversion module is composed of a module-level energy dissipation device and a frequency conversion circuit connected in parallel; The system-level energy discharge device is used to discharge the redundant electric energy on the AC side of the first AC system and the second AC system; The module-level energy dissipation device is used to discharge the excess electric energy of the frequency conversion circuit; A plurality of chain-level energy dissipation devices, each of which is connected in parallel with a bridge arm, is used to discharge excess electrical energy of the bridge arm.

2. The cross-converter according to claim 1, characterized in that: Also includes: For each frequency conversion device, the input end of each bridge arm is correspondingly connected to a phase AC bus of the first AC system through a switch module, and / or the output end of each bridge arm is connected to the same AC bus of the second AC system through a switch module.

3. The cross-converter according to claim 1, characterized in that: The system-level energy dissipation device includes: a plurality of lightning arresters connected in parallel or in series, or a plurality of resistors connected in series in sequence.

4. The cross-converter according to claim 1, characterized in that: The chain-level energy dissipation device includes: a plurality of lightning arresters connected in parallel or in series, or a plurality of resistors connected in series in sequence.

5. The cross-converter according to claim 1, characterized in that: The module-level energy dissipation device includes: a plurality of lightning arresters connected in parallel or in series, or a plurality of resistors connected in series in sequence.

6. The cross-converter according to claim 1, characterized in that: The frequency conversion circuit is a full-bridge structure, which includes two groups of switch device bridge arms and a DC capacitor. The two groups of switch device bridge arms are connected in parallel, each group of switch device bridge arms includes two switch devices connected in series, and the DC capacitor is connected in parallel with the two groups of switch device bridge arms.

7. The cross-converter according to claim 1, characterized in that: The frequency conversion circuit is a half-bridge structure, which includes a group of switching device bridge arms and a DC capacitor. The group of switching device bridge arms includes two power electronic devices connected in series, and the DC capacitor is connected in parallel with the switching device bridge arms.

8. A power system, characterized in that: include: The AC-AC converter, the first AC system and the second AC system according to any one of claims 1 to 7, wherein: The input end of each bridge arm of each frequency conversion device of the AC-AC converter is correspondingly connected to a phase AC busbar of the first AC system, and the output end of each bridge arm is connected to the same phase AC busbar of the second AC system; The AC-AC converter is used to convert the first frequency three-phase voltage of the first AC system into a second frequency three-phase voltage, and transmit the second frequency three-phase voltage to the second AC system.

9. The power system according to claim 8, characterized in that: The first AC system includes: a distribution station, and / or a power station, and / or a transformer substation, and / or a new energy power generation base.

10. The power system according to claim 8, characterized in that: The second AC system includes: a plurality of offshore wind power stations, and / or a plurality of offshore solar power stations, and / or a plurality of offshore tidal power stations.

Images