Converter system

Abstract

The utility model provides a current conversion system, which comprises an alternating current source end, a direct current line end and at least one phase of main circuit, the at least one phase of main circuit is connected between the alternating current source end and the direct current line end, the at least one phase of main circuit comprises an upper bridge arm and a lower bridge arm, the upper bridge arm and the lower bridge arm are respectively connected to the direct current line end; the reactor assembly is arranged between the upper bridge arm and the lower bridge arm of the at least one phase of main circuit; when the upper bridge arm and the lower bridge arm of the at least one phase of main circuit work, the current rising rate is limited through at least one part of the reactor assembly. The converter system provided by the utility model not only can greatly reduce the demand for the saturable reactor, but also can effectively suppress the current oscillation caused by the discharge of the stray capacitor in the periodic trigger opening process, and meanwhile, the reactor is externally arranged, thereby reducing the risk of the vibration of the valve and the water leakage of the reactor to the safe operation of the valve.

Description

TECHNICAL FIELD

[0001] The utility model relates to high voltage direct current transmission technical field, concretely relates to a converter system. BACKGROUND

[0002] As the core component of the DC transmission system and the high-power converter, the safety and reliability of the commutation process of the converter have an important influence on the system operation. The traditional controllable commutation converter usually uses a reactor to limit the current rise rate in the process of opening through the power electronic device, and at the same time, suppresses the oscillation that may occur between the stray capacitance of the converter transformer and the bridge arm inductance. The reactor plays a key role in ensuring the safe operation of the device.

[0003] However, the topology structure in the prior art is complex, which not only has high requirements for the valve tower space and installation position, but also increases the cost and loss, is not conducive to improving the overall efficiency, and at the same time, the high-performance integrated gate commutated thyristor (IGCT) cannot fully exert the advantages of current impact resistance and opening ability.

[0004] Therefore, there is an urgent need for a new converter system to suppress the current oscillation caused by the stray capacitance, while improving the stability and engineering feasibility of the system operation. SUMMARY

[0005] In order to solve the above technical problems, the embodiments of the utility model provide a converter system, the converter system includes a circuit topology, which comprises: an AC source end, a DC line end and at least one phase main road, the at least one phase main road is connected between the AC source end and the DC line end, the at least one phase main road includes an upper bridge arm and a lower bridge arm, the upper bridge arm and the lower bridge arm are connected to the DC line end respectively; a reactor assembly is arranged between the upper bridge arm and the lower bridge arm of the at least one phase main road; when the upper bridge arm and the lower bridge arm of the at least one phase main road work, the current rise rate is limited by at least a part of the reactor assembly.

[0006] The converter system further comprises a current limiting switch, the current limiting switch comprises a first current limiting switch and a second current limiting switch, one end of the reactor assembly is electrically connected to the upper bridge arm of the phase main road through the first current limiting switch, and the other end of the reactor assembly is electrically connected to the lower bridge arm of the phase main road through the second current limiting switch.

[0007] In some embodiments, the reactor assembly comprises one of an air-core reactor and a saturation reactor.

[0008] The reactor assembly is a coupled reactor, the reactor assembly has two ends, the upper bridge arm and the lower bridge arm of the at least one phase main road are electrically connected to one end of the reactor assembly, and the AC source end is electrically connected to the other end of the reactor assembly.

[0009] The reactance component is a coupling reactance, and the reactance component comprises a core and a first coil and a second coil, when the upper bridge arm of the at least one phase main circuit works, the current rising rate of the upper bridge arm is limited via the first coil, and when the lower bridge arm of the at least one phase main circuit works, the current rising rate of the upper bridge arm is limited via the second coil.

[0010] The coupling reactance component comprises a saturated reactance or a non-saturated reactance.

[0011] The reactance component comprises a coil, and the upper bridge arm and the lower bridge arm of the at least one phase main circuit are connected to one end of the reactance component, and the AC source end of the phase main circuit is connected to the other end of the reactance component.

[0012] The upper bridge arm and the lower bridge arm are respectively provided with a plurality of single valve components, and the reactance component is arranged between the single valve components and the AC source end.

[0013] The circuit topology comprises at least three phase main circuits, and each phase main circuit comprises a corresponding upper bridge arm and a lower bridge arm.

[0014] The single valve components of the upper bridge arm and the lower bridge arm in the converter system form an integrated module, and the reactance component is arranged separately from the integrated module.

[0015] Compared with the prior art, the embodiments of the present disclosure have the following beneficial effects:

[0016] The reactance component arranged between the upper bridge arm and the lower bridge arm of the at least one phase main circuit greatly reduces the demand for a saturated reactance and effectively suppresses the current oscillation caused by the discharge of stray capacitance in the period trigger opening process.

[0017] The reactance component is connected in series with the current limiting switch, the first current limiting switch and the lower bridge arm and the second current limiting switch and the upper bridge arm are respectively controlled in coordination, so that the opening of the bridge arm is constrained and protected.

[0018] The single valve components of the upper bridge arm form an integrated module, and the reactance component is arranged separately from the integrated module, so that the arrangement flexibility and the maintainability of the system are improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Other features and advantages of the present application will be better understood through the following detailed description of the optional embodiments with reference to the accompanying drawings, wherein the same reference signs represent the same or similar parts, and wherein:

[0020] Figure 1 A schematic diagram of a converter system of the embodiments of the present disclosure is shown;

[0021] Figure 2A circuit structure schematic diagram of a single valve assembly is shown.

[0022] Figures 3 to 5 A commutation system schematic diagram according to an embodiment of the present application is shown.

[0023] The following are the figure labels:

[0024] 1 is an AC source end, 2 is a DC line end, 3 is an AC source, 4 is an upper bridge arm, 5 is a lower bridge arm, 7 is a reactor assembly, 8 is a device module, 9 is a valve arrester, 10 is a line stray inductance, 11 is a power electronic device, 12 is a buffer circuit capacitor, 13 is a buffer circuit resistor, 14 is a DC resistor, 15 is a device arrester, 16 is a commutation inductance, 17 is a stray capacitor, 18 is a DC side inductance, 19 is a first current limiting switch, 20 is a second current limiting switch, 21 is a first coil, 22 is a second coil, 23 is an iron core, 31 is an A-phase AC source, 32 is a B-phase AC source, 33 is a C-phase AC source, 61 to 66 are single valve assemblies, and 701 to 703 are reactor assemblies of embodiments. DETAILED DESCRIPTION

[0025] 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 are only some embodiments but not all embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0026] To solve the problems in the prior art, such as too many saturated reactors, large volume, increased cost and loss, stray capacitor oscillation, and insufficient utilization of device performance, in a hybrid controllable commutation converter.

[0027] The embodiments of the present application propose a hybrid commutation valve system which can be externally arranged on a valve tower based on reusable reactors, and the system comprises a circuit topology, which comprises an AC source end, a DC line end and at least one phase main circuit, the at least one phase main circuit is connected between the AC source end and the DC line end, the at least one phase main circuit comprises an upper bridge arm and a lower bridge arm, the upper bridge arm and the lower bridge arm are respectively connected to the DC line end, the upper bridge arm and the lower bridge arm are respectively provided with a plurality of single valve assemblies, a reactor assembly is arranged between the upper bridge arm and the lower bridge arm of the at least one phase main circuit, and the upper bridge arm and the lower bridge arm of the at least one phase main circuit work by limiting the current rise rate of at least a part of the reactor assembly.

[0028] The preferred embodiments according to the present application will be described in detail below with reference to the drawings.

[0029] Referring to Figure 1 , a converter system of the embodiments of the present disclosure is shown, which includes a circuit topology including an AC source end 1 and a DC line end 2, and connecting each phase AC source 3 of the AC source end 1 with the DC line end 2 through a main circuit, and the circuit topology includes at least one phase main circuit. The at least one main circuit includes an upper bridge arm 4 and a lower bridge arm 5, and the upper bridge arm 4 and the lower bridge arm 5 are connected to the DC line end 2 respectively. Between the upper bridge arm 4 and the lower bridge arm 5 of the main circuit belonging to the same phase, an electric reactor assembly 7 is further provided. In the phase main circuit connected with the current source 3, the single valve assembly of the upper bridge arm 4 and the single valve assembly of the lower bridge arm 5 share at least a part of the electric reactor assembly 7 when conducting, and the upper bridge arm 4 and the lower bridge arm 5 of the phase main circuit do not work at the same time.

[0030] In some embodiments, the AC source end 1 can be a three-phase AC power source, or an AC power source composed of several three-phase AC power sources connected in a delta or star shape. The AC source end 1 of the embodiments of the present disclosure is composed of three AC sources 3 with a phase difference of 120°, and the DC line end 2 is located on the other side of the circuit topology. If it is other number of multi-phase AC power sources, it can also be analogized in this way.

[0031] In some embodiments, the several single valve assemblies form an integrated module, constituting a valve tower. In some embodiments, the electric reactor assembly 7 is provided outside the valve tower, which can reduce the influence of the vibration of the electric reactor assembly 7 on the valve tower, reduce the risk caused by the leakage of the electric reactor, and improve the arrangement flexibility and system maintainability.

[0032] The circuit topology further includes a commutation inductance 16 and a stray capacitance 17, and a DC side inductance 18. The circuit topology in the embodiments of the present disclosure can realize the rectification process of converting AC into DC, or the inversion process of converting DC into AC. In the rectification process, the AC source 3 is connected to the circuit through the commutation inductance 16; in the inversion process, the DC line end 2 is connected to the circuit through the DC side inductance 18, and the commutation inductance 16 and the DC side inductance 18 play a role in buffering current and improving commutation conditions. The stray capacitance 17 represents the parasitic capacitance in the converter transformer and the line. The valve arrester 9 is connected in parallel across the single valve assembly, for overall overvoltage protection.

[0033] Continuing to refer to Figure 1, the upper bridge arm 4 includes single valve assembly 62, single valve assembly 64, single valve assembly 66, the lower bridge arm 5 includes single valve assembly 61, single valve assembly 63, single valve assembly 65. The AC source 3 is the equivalent AC source of grid topology, the AC source end 1 includes current source 31, current source 32, current source 33 in A phase, B phase, C phase respectively.

[0034] In some embodiments, when the circuit topology is in the rectification process, the AC source end 1 provides three-phase AC source 3, and the phase difference is 120°, and the single gate assembly is opened and closed in a certain order to make one of the single gate assemblies of the upper bridge arm 4 and one of the single gate assemblies of the lower bridge arm 5 simultaneously in the conducting state, forming a current loop. The working conditions of the converter are introduced below.

[0035] In the AC source end 1, the current source 3 with the highest voltage and the lowest voltage; in the upper bridge arm 4, the single gate assembly connected to the lowest voltage; and in the lower bridge arm 5, the single valve assembly connected to the highest voltage, together constitute a current loop.

[0036] Specifically, the current source 31 and the current source 33 have the highest voltage and the lowest voltage in the AC source 3 respectively, then in the single gate assembly of the upper bridge arm 4, the single valve assembly 62 has the lowest voltage, and in the single gate assembly of the lower bridge arm 5, the single valve assembly 61 has the highest voltage, together constitute a current loop.

[0037] Among them, the current flow path includes: from the current source 31, through the commutation inductance 16 and the stray capacitance 17, through the reactor assembly 7 connected to the current source 31, and at least through part of the reactor assembly 7, and then the current flows to the single valve assembly 61 of the lower bridge arm 5.

[0038] After the phase passes through 60°, the single valve assembly 61, the single valve assembly 62, the single valve assembly 63, the single valve assembly 64, the single valve assembly 65, and the single valve assembly 66 are opened and closed in sequence to perform the commutation process.

[0039] When the current source 32 and the current source 31 have the highest voltage and the lowest voltage in the AC source 3 respectively, the single valve assembly 63 and the single valve assembly 64 are opened, and the current flow path includes: current from the single valve assembly 64 of the upper bridge arm 4, through the reactor assembly 7 connected to the current source 31, and at least through part of the reactor assembly 7, and then through the stray capacitance 17 and the commutation inductance 16 in turn, and then flows to the current source 31.

[0040] In the inverter process, the current flow direction in the formed current loop is the same, which is not described here.

[0041] In the embodiments of the present disclosure, the reactor assembly 7 can have various forms, such as a hollow reactor assembly, a saturation reactor assembly or a coupling reactor assembly.

[0042] With reference to Figure 2 , the upper bridge arm 4 and the lower bridge arm 5 are respectively provided with a plurality of single valve assemblies, each of which includes a plurality of device modules 8, a valve arrester 9 and a line stray inductance 10. The device module 8 includes a power electronic device 11, a snubber circuit capacitor 12, a snubber circuit resistor 13, a direct current resistor 14 and a device arrester 15, etc. In some embodiments, the power electronic device 11 is a semi-controlled device such as a thyristor, or a fully-controlled device such as an integrated gate-commutated thyristor (IGCT). In the embodiments of the present disclosure, the single valve assembly includes a plurality of the device modules 8 connected in series, which are used for voltage division, and the number of the device modules 8 is related to the number of voltage levels.

[0043] In the embodiments of the present disclosure, the power electronic device 11 preferably adopts an IGCT device, which has strong resistance; the snubber circuit capacitor 12 and the snubber circuit resistor 13 are connected in series, which are used for weakening the switching transient overvoltage; the direct current resistor 14 is connected in parallel across the power electronic device 11, which is used for improving voltage balance and discharging charge; and the device arrester 15 is connected in parallel across the power electronic device 11, which is used for suppressing overvoltage impact and improving device safety.

[0044] With reference to Figure 3 An embodiment using a current-limiting switch and a reactor assembly is given. The upper bridge arm 4 and the lower bridge arm 5 are connected to the reactor assembly 701 by limiting the current direction through the switch. The current-limiting switch includes a first current-limiting switch 19 and a second current-limiting switch 20. In the main path connecting the current source 3 of the same phase, the first current-limiting switch 19 is connected to one end of the reactor assembly 701 connected to the upper bridge arm 4, and the second current-limiting switch 20 is connected to the other end of the reactor assembly 701 connected to the lower bridge arm 5.

[0045] In the main path connecting the current source 3 of the same phase, when the first current-limiting switch 19 is turned on, the reactor assembly 701 is used to limit the current rise rate of the lower bridge arm 5. The same parts as those in the Figure 1 embodiment have the same functions, which are not described in detail here.

[0046] For example, in the current loop formed by the current source 31 and the current source 33, the current flowing from the current source 31, sequentially passing through the commutation inductance 16 and the stray capacitance 17, then passing through the first current-limiting switch 19 connected to the current source 31, and then passing through the reactor assembly 701, flows to the single-valve assembly 61 of the lower bridge arm 5.

[0047] In the main path of the same phase current source 3, when the second current-limiting switch 20 is turned on, the reactor assembly 701 is used to limit the current rise rate of the upper bridge arm 4.

[0048] In the current loop formed by the current source 32 and the current source 31, the current passing through the single-valve assembly 64 of the upper bridge arm 4, then passing through the reactor assembly 701 connected to the current source 31, then passing through the second current-limiting switch 20, and then sequentially passing through the stray capacitance 17 and the commutation inductance 16, flows to the current source 31.

[0049] In the period trigger process, the stray capacitance 17 and the bridge arm inductance are easy to form a shock loop. The selective control of the first current-limiting switch 19 and the second current-limiting switch 20 in the embodiment of the present disclosure suppresses the continuous shock process between the stray capacitance 17 and the bridge arm inductance, and makes the reactor assembly 701 controllable, thereby ensuring the stability of the commutation process.

[0050] In the embodiment of the present disclosure, the reactor assembly 701 includes one of an air-core reactor assembly, a saturated reactor assembly, a coupled reactor assembly, or other types of reactors.

[0051] The reactor assembly 701 can effectively limit the current rise rate of the single-valve assembly by using the current-limiting characteristics of the reactor.

[0052] Reference Figure 4 An embodiment of a coupled reactor is given, in which the upper bridge arm 4 and the lower bridge arm 5 are directly connected to the reactor assembly 702. The reactor assembly 702 is a coupled reactor, which includes a first coil 21, a second coil 22, and a core 23, and the core 23 is electrically coupled to the main path of the phase.

[0053] The reactor assembly 702 includes a saturated reactor and a non-saturated reactor. In some embodiments, the core 23 is one of a saturated core or a non-saturated core.

[0054] In the circuit connected to the same AC source 3, the reactor assembly 702 comprises a three-terminal interface, the upper bridge arm 4 is connected to one end of the reactor assembly 702 and connected to the first coil 21, the lower bridge arm 5 is connected to the second end of the reactor assembly 702 and connected to the second coil 22, and the AC source end 1 is connected to the third end of the reactor assembly 702.

[0055] In the main circuit connected to the same phase current source 3, when the upper bridge arm 4 is working, the iron core 23 and the first coil 21 are used to limit the current rise rate of the upper bridge arm 4. When the lower bridge arm 5 is working, the iron core 23 and the second coil 22 are used to limit the current rise rate of the lower bridge arm 5. The coupling direction of the reactor assembly 702 should be the same as the voltage connected to the bridge arm, and no reverse pressure is added to the single valve assembly connected thereto.

[0056] For example, in the current loop formed by the current source 32 and the current source 31, the current flows from the current source 32, through the commutation inductance 16 and the stray capacitance 17, to the second coil 22 of the reactor assembly 702 connected to the current source 32, and then to the lower bridge arm 5 with the single valve assembly 63, and to the DC connection end 2. Then, when the upper bridge arm 4 with the single valve assembly 64 works, the current flows through the first coil 21 of the reactor assembly 702 connected to the current source 31, and then sequentially through the stray capacitance 17 and the commutation inductance 16, and then to the current source 31.

[0057] In other phase circuits, the sequence described above and in the above embodiments can be referred to, and will not be described in detail here.

[0058] During commutation, the stray capacitance 17 discharges with the line stray inductance 10, and the reactor assembly 4 can reduce the current rise rate during the capacitance discharge process during switching-on.

[0059] Referring to Figure 5 The reactor assembly 703 can be replaced by only one coil, so that the reactor assembly 703 comprises a two-terminal interface, the upper bridge arm 4 and the lower bridge arm 5 of the same phase main circuit are connected to one port of the reactor assembly 703, and the AC source end 1 of the AC source 3 is connected to the other port of the reactor assembly 703. In some embodiments, the upper bridge arm 4 and the lower bridge arm 5 form a common connection point, and are connected in series with the reactor assembly 703.

[0060] In the scheme, the voltage of the reactor assembly 703 can be made to be in the same direction as the voltage connected to the bridge arm by adjusting the direction of the coil of the reactor assembly 703, without increasing the counter pressure on the single valve assembly connected thereto, and no controller is required in the circuit topology.

[0061] In the embodiments of the present disclosure, the upper bridge arm 4 and the lower bridge arm 5 of the same phase share one reactor assembly 7, which reduces the number of reactor assemblies 7 in the circuit topology, reduces the volume of the system, and reduces the cost.

[0062] In the converter system provided by the embodiments of the present disclosure, the single valve assemblies of the upper bridge arm and the lower bridge arm form an integrated module, and the reactor assembly is separately arranged from the integrated module.

[0063] In the converter system of the embodiments of the present disclosure, the reactor assembly is separately arranged from the integrated module, and the reactor assembly is arranged at the AC source end and can be placed outside the valve tower, which reduces the risk of valve safe operation caused by vibration of the valve and leakage of the reactor, and improves the arrangement flexibility and the maintainability of the system.

[0064] The technical content and technical features of the present application have been disclosed above, but it can be understood that, under the creative idea of the present application, those skilled in the art can make various changes and improvements on the disclosed concepts, but all of them belong to the protection scope of the present application. The description of the above embodiments is illustrative rather than limiting, and the protection scope of the present application is determined by the claims.

Claims

1. A converter system, comprising: an AC source end, a DC line end, and at least one phase main connected between the AC source end and the DC line end, the at least one phase main comprising an upper bridge arm and a lower bridge arm, the upper bridge arm and the lower bridge arm being connected to the DC line end, respectively; characterized in that it further comprises: a reactor assembly arranged between the upper bridge arm and the lower bridge arm of the at least one phase main, the upper bridge arm and the lower bridge arm of the at least one phase main, when operating, both limiting a current rise rate via at least a portion of the reactor assembly.

2. The commutation system of claim 1, wherein, The converter system further comprises a current limiting switch, the current limiting switch comprising a first current limiting switch and a second current limiting switch, the first current limiting switch being electrically connected to one end of the reactor assembly with the upper bridge arm of the phase main, the second current limiting switch being electrically connected to the other end of the reactor assembly with the lower bridge arm of the phase main.

3. The commutation system of claim 2, wherein, The reactor assembly comprises one of an air-core reactor and a saturable reactor.

4. The commutation system of claim 1, wherein, The reactor assembly is a coupled reactor, the reactor assembly having two ends, the upper bridge arm and the lower bridge arm of the at least one phase main being electrically connected to one end of the reactor assembly, the AC source end being electrically connected to the other end of the reactor assembly.

5. The commutation system of claim 4, wherein, The reactor assembly is a coupled reactor, the reactor assembly comprising a core and a first coil and a second coil, the upper bridge arm of the at least one phase main, when operating, limiting a current rise rate of the upper bridge arm via the first coil, the lower bridge arm of the at least one phase main, when operating, limiting a current rise rate of the upper bridge arm via the second coil.

6. The commutation system of claim 4, wherein, The coupled reactor comprises a saturable reactor or a non-saturable reactor.

7. The commutation system of claim 1, wherein, The reactor assembly comprises a coil, the upper bridge arm and the lower bridge arm of the at least one phase main both being connected to one end of the reactor assembly, the AC source end of the phase main being electrically connected to the other end of the reactor assembly.

8. The commutation system of any one of claims 1 to 7, wherein, The converter system comprises at least three phase mains, each phase main comprising a corresponding upper bridge arm and a lower bridge arm.

9. The commutation system of claim 8, wherein, The upper bridge arm and the lower bridge arm are respectively provided with a plurality of single valve assemblies.

10. The commutation system of claim 9, wherein, The plurality of single valve assemblies of the upper bridge arm and the lower bridge arm respectively form integrated modules, the reactor assembly being arranged separately from the integrated modules.

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