CN111049147A - Hybrid compensation type inter-line power transfer device and control method thereof - Google Patents
Hybrid compensation type inter-line power transfer device and control method thereof Download PDFInfo
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- CN111049147A CN111049147A CN202010039825.XA CN202010039825A CN111049147A CN 111049147 A CN111049147 A CN 111049147A CN 202010039825 A CN202010039825 A CN 202010039825A CN 111049147 A CN111049147 A CN 111049147A
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- 230000005540 biological transmission Effects 0.000 claims description 62
- 238000004146 energy storage Methods 0.000 claims description 16
- 239000003990 capacitor Substances 0.000 claims description 3
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1807—Arrangements for adjusting, eliminating or compensating reactive power in networks using series compensators
- H02J3/1814—Arrangements for adjusting, eliminating or compensating reactive power in networks using series compensators wherein al least one reactive element is actively controlled by a bridge converter, e.g. unified power flow controllers [UPFC]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1878—Arrangements for adjusting, eliminating or compensating reactive power in networks using tap changing or phase shifting transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
Abstract
The invention provides a hybrid inter-line power transfer device which comprises two groups of series compensation devices, wherein each group of series compensation devices comprises at least one series transformer, a voltage source converter and at least one bypass switch, and at least one group of series compensation devices comprises at least one reactor unit. A first side winding of a series transformer in each group of series compensation devices is connected with a bypass switch in parallel and then connected with a line in series; the second side windings of the series transformers in each group of series compensation devices are connected with the alternating current side of the voltage source converter, or the second side windings of the series transformers are connected with the reactor unit and then connected with the alternating current side of the voltage source converter; the DC sides of the voltage source converters of the two groups of series compensation devices are connected. The invention also provides a corresponding control method. The technical scheme of the invention can reduce the total capacity of the device, reduce the cost and the occupied area, and simultaneously has the fault current limiting capability and improves the reliability of equipment.
Description
Technical Field
The invention belongs to the technical field of flexible alternating current transmission in an electric power system, and particularly relates to a compensator for power transfer between lines and a control method thereof.
Background
The power system is rapidly developed, and with the continuous increase of loads, the increasing complexity of grid structures and the large-scale access of new energy, the problems of uneven power flow distribution, insufficient voltage supporting capability, electromechanical oscillation and the like are often interwoven, so that a new challenge is brought to the operation control of a power grid. Due to saturation of transmission corridors and commercial operation of grid companies, it will become increasingly difficult to increase transmission capacity by building new transmission lines. The continuous increase of user load requires a power flow control means to improve the existing power transmission capability; the complex exchange of power between the booming smart grid and the electricity market requires frequent tidal current control.
The interline Power Flow controller (also called IPFC) is a flexible alternating current transmission device, can control the Power of a plurality of transmission lines, balances the active Power Flow and the reactive Power Flow among a plurality of lines, reduces the burden of an overloaded line through the balance and mediation of the active Power, improves the overall transmission capacity of the plurality of lines, increases the overall compensation effect of a system under dynamic disturbance, and provides an efficient control mode for the Power Flow management of a plurality of lines of a transformer substation.
The compensator with the functions of series compensation, phase shift control and the like of the voltage source converter can optimize and adjust the system power flow, but the capacity and the price advantage are weak. The traditional reactor can be used for line series compensation and fault current limitation, but cannot meet the requirement of accurate and rapid adjustment. The traditional reactor is combined with the compensator adopting the voltage source converter to form a hybrid type compensator, and the advantages of the traditional reactor and the compensator can be fully exerted. In addition, the scheme of the power transfer device between lines applied to the existing multi-circuit power transmission channel needs voltage source converters with the same number as the lines, the occupied area and the cost are high, and the control function is complex to realize. In order to save the investment and the occupied area of engineering application, reduce the complexity of a control system and increase the reliability of the system, a simpler and more practical structure is needed.
Disclosure of Invention
The invention aims to provide a hybrid compensation type inter-line power transfer device, which can save the overall cost and the occupied area of the device while meeting the requirement of power transfer regulation of a power grid line and is suitable for engineering application. The invention also provides a corresponding control method.
In order to achieve the above purpose, the solution of the invention is:
a hybrid compensation type power transfer device between lines comprises two groups of series compensation devices, wherein the first group of series compensation devices comprises a voltage source converter, at least one series transformer and at least one bypass switch; the second group of series compensation devices comprises at least one voltage source converter, at least one series transformer, at least one bypass switch and at least one fixed compensation unit; the first set of series compensation devices is accessed into a first power line channel and the second set of series compensation devices is accessed into a second power line channel. Two ends of a first side winding of a series transformer of the first group of series compensation devices are connected in series with a first transmission line channel, and the first side winding is connected with at least one bypass switch in parallel; and the three-phase outgoing line of the second side winding is connected with the alternating current side branch of the voltage source converter of the first group of series compensation devices. Two ends of a first side winding of a series transformer of the second group of series compensation devices are connected in series with a second transmission line channel, and the first side winding is connected with at least one bypass switch in parallel; and a three-phase outgoing line of the second side winding is connected with the first side of the fixed compensation unit, and the second side of the fixed compensation unit is connected with the alternating current side of the voltage source converter of the second group of series compensation devices. The direct current sides of the voltage source converters of the two groups of series compensation devices are mutually connected.
As a further preferable aspect of the present invention, the voltage source converter of at least one set of series compensation devices is a modular multilevel converter, and includes three phase units, each phase unit includes two branch units, each branch unit is formed by connecting N1 half-bridge sub-module units and N2 full-bridge sub-module units in series, N1 and N2 are both integers greater than or equal to 0, and N1 is not less than N2.
As a further preferable aspect of the present invention, the fixed compensation unit includes at least one reactor and at least one mechanical switch, each reactor being connected in parallel with one mechanical switch.
As a further preferable aspect of the present invention, the hybrid compensation type inter-line power transfer device further includes a dc energy storage unit, and the dc energy storage unit is connected to the dc sides of the voltage source converters of the two series compensation devices.
As a further preferable aspect of the present invention, the energy storage unit includes at least one of a capacitor, an energy storage battery, a converter, and a UPS uninterruptible power supply.
As a further preferable aspect of the present invention, the hybrid compensation type inter-line power transfer device further includes a dc voltage converter, a first side of the dc voltage converter is connected to a dc side of the voltage source converters of the two series compensation devices, and a second side of the dc voltage converter is connected to the dc energy storage unit.
As a further preferable aspect of the present invention, the hybrid compensation type inter-line power transfer device further includes a set of parallel compensation devices, and the parallel compensation devices include a voltage source converter and a parallel transformer. The direct current side of the voltage source converter of the parallel compensation device is connected with the direct current side of the voltage source converter of the two groups of series compensation devices; the first side of a shunt transformer of the shunt compensation device is connected with the alternating current side of a voltage source converter of the shunt compensation device, and the second side of the shunt transformer is connected with any alternating current bus.
As a further preferable aspect of the present invention, the bypass switch includes a mechanical switch or a switch formed by power electronics.
As a further preferable aspect of the present invention, when the hybrid compensation type inter-line power transfer device is applied to two sets of multi-circuit transmission channels, the hybrid compensation type inter-line power transfer device includes two sets of series compensation devices. The number of series transformers of the first group of series compensation devices is equal to that of the first group of multi-circuit lines, the number of bypass switches of the first group of series compensation devices is not less than that of the first group of multi-circuit lines, and the first group of series compensation devices comprises a voltage source converter; two ends of a first side winding of each series transformer are respectively connected with each line of the first group of power transmission channels in series, and the first side winding of each series transformer is connected with at least one bypass switch in parallel; three-phase outgoing lines of the second side windings of all the series transformers are connected in parallel and then connected with the alternating current side part of the voltage source converter of the first group of series compensation devices. The number of the series transformers of the second group of series compensation devices is equal to that of the second group of multi-circuit lines, and the number of the bypass switches of the second group of series compensation devices is not less than that of the second group of multi-circuit lines; the number of the second group of fixed compensation units is equal to that of the second group of multi-loop lines; the second group of series compensation devices comprises a voltage source converter; two ends of a first side winding of each series transformer are respectively connected with each line of the second group of power transmission channels in series, and the first side winding of each series transformer is connected with at least one bypass switch in parallel; and the three-phase outgoing line of the second side winding of each series transformer is connected with the first side phase of one fixed compensation unit, and the second side phase of all the fixed compensation units are connected in parallel and then connected with the alternating current side phase of the voltage source converter of the second group of series compensation devices.
As a further preferable aspect of the present invention, when the hybrid compensation type inter-line power transfer device is applied to multiple groups of power transmission line channels, the N groups of power transmission line channels include N groups of series compensation devices, and each group of series compensation devices is connected to one group of line power transmission channels. The number of series transformers of each group of series compensation devices is the same as the number of lines in the corresponding power transmission channel; the number of the bypass switches of each group of the series compensation devices is not less than the number of the lines in the corresponding power transmission channel; each group of series compensation devices only comprises one voltage source converter; at most N-1 sets of series compensation devices comprise fixed compensation units. In the series compensation device without the fixed compensation unit, two ends of a first side winding of each series transformer are respectively connected in series with each line of the group of power transmission channels, and the first side winding of each series transformer is connected in parallel with at least one bypass switch; the three-phase outgoing lines of the second side windings of all the series transformers are connected in parallel and then connected with the alternating current side part of the voltage source converter of the group of series compensation devices. In the series compensation device comprising fixed compensation units, the number of the fixed compensation units is the same as the number of lines in the corresponding power transmission channel; two ends of a first side winding of each series transformer are respectively connected with each line of the group of power transmission channels in series, and the first side winding of each series transformer is connected with at least one bypass switch in parallel; the three-phase outgoing line of the second side winding of each series transformer is connected with the first side phase of one fixed compensation unit, and the second side phase of all the fixed compensation units are connected in parallel and then connected with the alternating current side phase of the voltage source converter of the group of series compensation devices. The direct current sides of the voltage source converters of all the series compensation devices are connected in parallel.
The invention also provides a control method of the hybrid compensation type inter-line power transfer device, which comprises the following steps: disconnecting the mechanical switch in the stationary compensation unit when the power to be reduced in the second power transmission line channel exceeds a set power threshold; when the reactor in the fixed compensation unit needs to be repaired due to a fault, the mechanical switch in the fixed compensation unit is closed.
The invention provides a control method of a hybrid compensation type inter-line power transfer device, which specifically comprises the following steps: and when the line current of the second transmission line channel is smaller than the set current threshold, closing the mechanical switch in the fixed compensation unit, and separating the mechanical switch in the fixed compensation unit after the current of the line connected to the hybrid compensation type inter-line power transfer device is larger than the set current threshold.
The invention provides another control method of a hybrid compensation type inter-line power transfer device, which specifically comprises the following steps: when the alternating current system is in a small operation mode, closing a mechanical switch in the fixed compensation unit; when the AC system is in a large operation mode, the mechanical switch in the compensation unit is separated and fixed.
The invention provides a control method of a hybrid compensation type inter-circuit power transfer device, which specifically comprises the following steps: the mechanical switches in the fixed compensation unit are disconnected upon detecting that the voltage generated by the voltage source converter in the second set of series compensation devices is greater than a set voltage threshold and that the generated voltage causes the line current to decrease.
The invention has the beneficial effects that: the hybrid power transfer device between lines provided by the invention can reduce the total capacity of the device, reduce the cost and the occupied area, and simultaneously has the fault current limiting capability and improves the reliability of equipment.
Drawings
Fig. 1 is a schematic diagram of a hybrid compensation type inter-line power transfer device proposed in the present application, which includes two sets of series compensation devices, each set of series compensation devices includes a series transformer 2, a bypass switch 1 and a voltage source converter 3, and the second set of series compensation devices further includes a fixed compensation unit 4;
fig. 2 is a block diagram of a modular multilevel converter according to the present application;
fig. 3 is a schematic diagram of another preferred hybrid compensation type inter-line power transfer apparatus according to the present application, in which a dc energy storage unit 5 is added compared with fig. 1;
fig. 4 is a schematic diagram of another preferred hybrid compensated inter-line power transfer apparatus of the present application, compared to fig. 1, with the addition of a voltage source converter 3 and a shunt transformer 6;
fig. 5 is a schematic diagram of a hybrid compensation type inter-line power transfer device suitable for a double-circuit line, each group of series compensation devices includes two series transformers 2, two bypass switches 1 and a voltage source converter 3; the second group of series compensation devices also comprises two fixed compensation units 4; the DC sides of the two voltage source converters are connected back-to-back.
Fig. 6 is a schematic diagram of another hybrid compensation type inter-line power transfer device suitable for a double-circuit line according to the present application, in which a voltage source converter 3 and a shunt transformer 6 are added compared with fig. 5;
fig. 7 is a schematic diagram of a hybrid compensation type inter-line power transfer device suitable for three sets of double-circuit lines, each set of series compensation device includes two series transformers 2, two bypass switches 1 and a voltage source converter 3; the second group of series compensation devices also comprises two fixed compensation units 4; the direct current sides of the three voltage source converters are connected back to back.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
The inter-line power transfer device of the hybrid compensation type inter-line power transfer device provided by the invention is shown in fig. 1 and comprises two groups of series compensation devices, wherein the first group of series compensation devices are connected into a first transmission line channel and used for improving the power of the first transmission line channel, and the second group of series compensation devices are connected into a second transmission line channel and used for reducing the power of the second transmission line channel; each series compensation device group comprises a voltage source converter 3, at least one series transformer 2 and at least one bypass switch 1, and the second series compensation device group further comprises a fixed compensation unit 4.
Two ends of a first side winding of a series transformer of the first group of series compensation devices are connected in series with a first transmission line channel, and the first side winding is connected with a bypass switch in parallel; and the three-phase outgoing line of the second side winding is connected with the alternating current side branch of the voltage source converter of the first group of series compensation devices. Two ends of a first side winding of a series transformer of the second group of series compensation devices are respectively connected in series with a second transmission line channel, and the first side winding is connected in parallel with a bypass switch; and a three-phase outgoing line of the second side winding is connected with the first side of the fixed compensation unit, and the second side of the fixed compensation unit is connected with the alternating current side of the voltage source converter of the second group of series compensation devices. The direct current sides of the voltage source converters of the two groups of series compensation devices are mutually connected. The fixed compensation unit comprises a reactor and a mechanical switch, and the reactor is connected with the mechanical switch in parallel.
In this embodiment, the second group of series compensation devices is formed by mixing the voltage source converter and the fixed compensation unit and performing series compensation together, so that the capacity of the voltage source converter of the group of series compensation devices can be saved, and the overall cost and the occupied area of the power transfer device between lines can be reduced.
In the hybrid compensation type inter-line power transfer device, the voltage source converter 3 of at least one group of series compensation devices is a modular multilevel converter, and as shown in fig. 2, the modular multilevel converter has a structure that the converter includes three phase units, each phase unit includes two branch units, each branch unit is formed by connecting N1 half-bridge sub-module units and N2 full-bridge sub-module units in series, N1 and N2 are integers greater than or equal to 0, and N1 is not less than N2.
In practical engineering applications, each branch unit of the voltage source converter 3 with a large capacity in the two series compensation devices of the hybrid compensation type inter-line power transfer device can be a modular multilevel converter formed by mixing full-bridge sub-module units and half-bridge sub-module units, and the ratio of the number of the full-bridge sub-module units to the number of the half-bridge sub-module units can be determined according to the ratio of the capacities of the voltage source converters 3 in the two series compensation devices. After the converter mixed by the full-bridge submodule and the half-bridge submodule is adopted, the voltage of an internal direct current system of the power transfer device between lines can be reduced, and the cost and the occupied area of the converter with smaller capacity are reduced.
Further, the bypass switches 1 in the two series compensation devices in the hybrid compensation type inter-line power transfer device include, but are not limited to, a mechanical switch and a switch formed by power electronic devices;
another preferred hybrid compensation type inter-line power transfer device shown in fig. 3 further includes a dc energy storage unit 5 based on the embodiment shown in fig. 1. The dc energy storage unit 5 is connected to the dc side of the voltage source converter 3 of the two series compensation devices. In another preferred embodiment, on the basis of the embodiment shown in fig. 1, the dc-dc converter further includes a dc energy storage unit 5 and a dc voltage converter, a first side of the dc voltage converter is connected to the dc sides of the voltage source converters 3 of the two sets of series compensation devices, and a second side of the dc voltage converter is connected to the dc energy storage unit 5. The dc energy storage unit 5 includes at least one of a capacitor, an energy storage battery, a converter, and an UPS uninterruptible power supply.
In another preferred hybrid compensation type inter-line power transfer device shown in fig. 4, a set of parallel compensation devices may be further included on the basis of the embodiment shown in fig. 1. The parallel compensation device comprises a voltage source converter 3 and a parallel transformer 6; the direct current side of the voltage source converter 3 of the parallel compensation device is connected with the direct current side of the voltage source converter 3 of the two groups of series compensation devices; the ac side connection of the voltage source converter 3 of the parallel compensation arrangement is connected with the first side of the shunt transformer 6; the second side of the shunt transformer 3 is connected to any ac bus.
The use method of the second series compensation device in the foregoing embodiment includes the following steps:
(1) disconnecting the mechanical switch in the stationary compensation unit when the power to be reduced in the second power transmission line channel exceeds a set power threshold; when the reactor in the fixed compensation unit needs to be repaired due to a fault, the mechanical switch in the fixed compensation unit is closed.
(2) And when the line current of the second transmission line channel is smaller than the set current threshold, closing the mechanical switch in the fixed compensation unit, and separating the mechanical switch in the fixed compensation unit after the current of the line connected to the hybrid compensation type inter-line power transfer device is larger than the set current threshold.
(3) When the alternating current system is in a small operation mode, closing a mechanical switch in the fixed compensation unit; when the AC system is in a large operation mode, the mechanical switch in the compensation unit is separated and fixed.
(4) The mechanical switches in the fixed compensation unit are disconnected upon detecting that the voltage generated by the voltage source converter in the second set of series compensation devices is greater than a set voltage threshold and that the generated voltage causes the line current to decrease.
The hybrid compensation type inter-line power transfer device can also be applied to two groups of multi-circuit line power transmission channels. As shown in fig. 5: the number of the series transformers 2 of the first group of series compensation devices is equal to that of the first group of multi-circuit lines, the number of the bypass switches 1 of the first group of series compensation devices is not less than that of the first group of multi-circuit lines, and the first group of series compensation devices comprises a voltage source converter 3; two ends of a first side winding of each series transformer 2 are respectively connected with each line of the first group of power transmission channels in series, and the first side winding of each series transformer 2 is connected with at least one bypass switch 1 in parallel; three-phase outgoing lines of windings on the second side of all the series transformers 2 are connected in parallel and then connected with an alternating-current side of a voltage source converter 3 of the first group of series compensation devices. The number of the series transformers 2 of the second group of series compensation devices is equal to that of the second group of multi-circuit lines, the number 1 of the bypass switches of the second group of series compensation devices is not less than that of the second group of multi-circuit lines, and the second group of series compensation devices comprises a voltage source converter 3; the number of the second group of fixed compensation units 4 is equal to the number of the second group of multi-loop lines. Three-phase outgoing lines of second side windings of two series transformers 2 in the first group of series compensation devices are connected in parallel and then connected with an alternating current side branch of a voltage source converter 3; second side windings of two series transformers 2 in the second group of series compensation devices are connected with a first side phase of a fixed compensation unit 4, and after the second side phases of the two fixed compensation units 4 are connected, the second side phases are connected with an alternating current side phase of a voltage source converter 3.
Another hybrid compensation type inter-line power transfer device suitable for two groups of multi-circuit transmission channels as shown in fig. 6 may further include a group of parallel compensation devices on the basis of the embodiment shown in fig. 5; the direct current side of the voltage source converter 3 of the parallel compensation device is connected with the direct current side of the voltage source converter 3 of the two groups of series compensation devices; the ac side connection of the voltage source converter 3 of the parallel compensation arrangement is connected with the first side of the shunt transformer 6; the second side of the shunt transformer 3 is connected to any ac bus.
The hybrid compensated inter-line power transfer apparatus of the present invention may also be applied to multiple sets of transmission line channels, as shown in fig. 7. And for the N groups of transmission line channels, N groups of series compensation devices are included, and each group of series compensation devices is accessed into one group of transmission line channels. The number of series transformers of each group of series compensation devices is the same as the number of lines in the corresponding power transmission channel; the number of the bypass switches of each group of the series compensation devices is not less than the number of the lines in the corresponding power transmission channel; each group of series compensation devices only comprises one voltage source converter; at most N-1 sets of series compensation devices comprise fixed compensation units. In the series compensation device without the fixed compensation unit, two ends of a first side winding of each series transformer are respectively connected in series with each line of the group of power transmission channels, and the first side winding of each series transformer is connected in parallel with at least one bypass switch; the three-phase outgoing lines of the second side windings of all the series transformers are connected in parallel and then connected with the alternating current side part of the voltage source converter of the group of series compensation devices. In the series compensation device comprising fixed compensation units, the number of the fixed compensation units is the same as the number of lines in the corresponding power transmission channel; two ends of a first side winding of each series transformer are respectively connected with each line of the group of power transmission channels in series, and the first side winding of each series transformer is connected with at least one bypass switch in parallel; the three-phase outgoing line of the second side winding of each series transformer is connected with the first side phase of one fixed compensation unit, and the second side phase of all the fixed compensation units are connected in parallel and then connected with the alternating current side phase of the voltage source converter of the group of series compensation devices. The direct current sides of the voltage source converters of all the series compensation devices are connected in parallel. As shown in fig. 7, the hybrid compensation type inter-line power transfer device applied to the power transmission channels of three groups of double-circuit lines includes a fixed compensation unit in the second group of series compensation devices, and separates a mechanical switch in the fixed compensation unit when the power of the line needs to be reduced in the second power transmission line channel; or when it is desired to reduce the fault current of the second power line channel, the mechanical switch in the compensation unit is fixed separately.
Finally, it should be noted that: the technical solutions of the present invention are only illustrated in conjunction with the above-mentioned embodiments, and not limited thereto. Those of ordinary skill in the art will understand that: modifications and equivalents may be made to the embodiments of the invention by those skilled in the art, which modifications and equivalents are within the scope of the claims appended hereto.
Claims (14)
1. A hybrid compensated inter-line power transfer device, comprising:
the system comprises two groups of series compensation devices, wherein the first group of series compensation devices comprises a voltage source converter, at least one series transformer and at least one bypass switch; the second group of series compensation devices comprises at least one voltage source converter, at least one series transformer, at least one bypass switch and at least one fixed compensation unit; the first group of series compensation devices is accessed into a first transmission line channel, and the second group of series compensation devices is accessed into a second transmission line channel;
two ends of a first side winding of a series transformer of the first group of series compensation devices are connected in series with a first transmission line channel, and the first side winding is connected with at least one bypass switch in parallel; the three-phase outgoing line of the second side winding is connected with the alternating current side branch of the voltage source converter of the first group of series compensation devices;
two ends of a first side winding of a series transformer of the second group of series compensation devices are connected in series with a second transmission line channel, and the first side winding is connected with at least one bypass switch in parallel; a three-phase outgoing line of the second side winding is connected with a first side of the fixed compensation unit, and a second side of the fixed compensation unit is connected with an alternating current side of a voltage source converter of the second group of series compensation devices;
the direct current sides of the voltage source converters of the two groups of series compensation devices are mutually connected.
2. The hybrid compensated inter-line power transfer device of claim 1, wherein: the voltage source converter of at least one group of series compensation devices is a modular multilevel converter and comprises three phase units, each phase unit comprises two branch units, each branch unit is formed by connecting N1 half-bridge sub-module units and N2 full-bridge sub-module units in series, N1 and N2 are integers which are more than or equal to 0, and N1 is not less than N2.
3. The hybrid compensated inter-line power transfer device of claim 1, wherein: the fixed compensation unit comprises at least one reactor and at least one mechanical switch, and each reactor is connected with one mechanical switch in parallel.
4. The hybrid compensated inter-line power transfer device of claim 1, wherein: the direct current energy storage unit is connected with the direct current sides of the voltage source converters of the two groups of series compensation devices.
5. The hybrid compensated inter-line power transfer device of claim 4, wherein: the energy storage unit comprises at least one of a capacitor, an energy storage battery, a converter and a UPS.
6. The hybrid compensated line-to-line power transfer device of claim 4, further comprising a DC voltage converter having a first side connected to the DC side of the voltage source converters of the two series compensation devices and a second side connected to the DC energy storage unit.
7. The hybrid compensated inter-line power transfer device of claim 1, wherein: the parallel compensation device comprises a voltage source converter and a parallel transformer;
the direct current side of the voltage source converter of the parallel compensation device is connected with the direct current side of the voltage source converter of the two groups of series compensation devices; the first side of a shunt transformer of the shunt compensation device is connected with the alternating current side of a voltage source converter of the shunt compensation device, and the second side of the shunt transformer is connected with any alternating current bus.
8. The hybrid compensated inter-line power transfer device of claim 1, wherein: the bypass switch may comprise a mechanical switch or a switch formed by power electronics.
9. The hybrid compensated inter-line power transfer device of claim 1, wherein: when the hybrid compensation type inter-line power transfer device is applied to two groups of multi-circuit line power transmission channels, the hybrid compensation type inter-line power transfer device comprises two groups of series compensation devices;
the number of series transformers of the first group of series compensation devices is equal to that of the first group of multi-circuit lines, the number of bypass switches of the first group of series compensation devices is not less than that of the first group of multi-circuit lines, and the first group of series compensation devices comprises a voltage source converter; two ends of a first side winding of each series transformer are respectively connected with each line of the first group of power transmission channels in series, and the first side winding of each series transformer is connected with at least one bypass switch in parallel; three-phase outgoing lines of second side windings of all series transformers are connected in parallel and then connected with alternating current side branches of voltage source converters of the first group of series compensation devices;
the number of the series transformers of the second group of series compensation devices is equal to that of the second group of multi-circuit lines, and the number of the bypass switches of the second group of series compensation devices is not less than that of the second group of multi-circuit lines; the number of the second group of fixed compensation units is equal to that of the second group of multi-loop lines; the second group of series compensation devices comprises a voltage source converter; two ends of a first side winding of each series transformer are respectively connected with each line of the second group of power transmission channels in series, and the first side winding of each series transformer is connected with at least one bypass switch in parallel; and the three-phase outgoing line of the second side winding of each series transformer is connected with the first side phase of one fixed compensation unit, and the second side phase of all the fixed compensation units are connected in parallel and then connected with the alternating current side phase of the voltage source converter of the second group of series compensation devices.
10. The hybrid compensated inter-line power transfer device of claim 1, wherein: when the hybrid compensation type inter-line power transfer device is applied to a plurality of groups of transmission line channels, the hybrid compensation type inter-line power transfer device comprises N groups of series compensation devices for N groups of transmission line channels, and each group of series compensation devices is connected to one group of line transmission channels;
the number of series transformers of each group of series compensation devices is the same as the number of lines in the corresponding power transmission channel; the number of the bypass switches of each group of the series compensation devices is not less than the number of the lines in the corresponding power transmission channel; each group of series compensation devices only comprises one voltage source converter; at most N-1 groups of series compensation devices comprise fixed compensation units;
in the series compensation device without the fixed compensation unit, two ends of a first side winding of each series transformer are respectively connected in series with each line of the group of power transmission channels, and the first side winding of each series transformer is connected in parallel with at least one bypass switch; three-phase outgoing lines of second side windings of all series transformers are connected in parallel and then connected with alternating current side parts of voltage source converters of the group of series compensation devices;
in the series compensation device comprising fixed compensation units, the number of the fixed compensation units is the same as the number of lines in the corresponding power transmission channel; two ends of a first side winding of each series transformer are respectively connected with each line of the group of power transmission channels in series, and the first side winding of each series transformer is connected with at least one bypass switch in parallel; the three-phase outgoing line of the second side winding of each series transformer is connected with the first side phase of one fixed compensation unit, and the second side phase of all the fixed compensation units are connected in parallel and then connected with the alternating current side phase of the voltage source converter of the group of series compensation devices;
the direct current sides of the voltage source converters of all the series compensation devices are connected in parallel.
11. The control method of a hybrid compensated inter-line power transfer device according to any of claims 1 to 8, characterized in that: disconnecting the mechanical switch in the stationary compensation unit when the power to be reduced in the second power transmission line channel exceeds a set power threshold; when the reactor in the fixed compensation unit needs to be repaired due to a fault, the mechanical switch in the fixed compensation unit is closed.
12. The control method of a hybrid compensated inter-line power transfer device according to any of claims 1 to 8, characterized in that: and when the line current of the second transmission line channel is smaller than the set current threshold, closing the mechanical switch in the fixed compensation unit, and separating the mechanical switch in the fixed compensation unit after the current of the line connected to the hybrid compensation type inter-line power transfer device is larger than the set current threshold.
13. The control method of a hybrid compensated inter-line power transfer device according to any of claims 1 to 8, characterized in that: when the alternating current system is in a small operation mode, closing a mechanical switch in the fixed compensation unit; when the AC system is in a large operation mode, the mechanical switch in the compensation unit is separated and fixed.
14. The control method of a hybrid compensated inter-line power transfer device according to any of claims 1 to 8, characterized in that: the mechanical switches in the fixed compensation unit are disconnected upon detecting that the voltage generated by the voltage source converter in the second set of series compensation devices is greater than a set voltage threshold and that the generated voltage causes the line current to decrease.
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