CN105703370B - Unified power flow controller combining series compensation and current converter - Google Patents
Unified power flow controller combining series compensation and current converter Download PDFInfo
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- CN105703370B CN105703370B CN201610129892.4A CN201610129892A CN105703370B CN 105703370 B CN105703370 B CN 105703370B CN 201610129892 A CN201610129892 A CN 201610129892A CN 105703370 B CN105703370 B CN 105703370B
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Classifications
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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
- 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
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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
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Abstract
The invention provides a unified power flow controller combining serial compensation and converters, wherein one end of a first converter is connected with a winding on one side of a series transformer in parallel, and the other end of the first converter is sequentially connected with a second converter and a parallel transformer; the other side winding of the series transformer is connected with a power transmission line; the reactor unit is connected in series with the first switch and then connected in parallel with the first converter; the capacitor unit is connected in series with the second switch and then connected in parallel with the first converter. Compared with the prior art, the unified power flow controller combining series compensation and the converter can provide inductive fixed offset adjustment by the reactor and can also provide capacitive fixed offset adjustment by the capacitor. The device can be used in a power transmission line or a distribution line for capacity or inductance adjustment, improves the transmission capacity of the line, improves the stability level of the system, controls the flow of the line, enhances the damping of the system and reduces the cost. And the reactor unit and the capacitor unit are arranged at the converter side, the insulation level of both is relatively lowered.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a unified power flow controller combining series compensation and an inverter.
Background
With the vigorous development of the power system, the problems of large-scale access of new energy, increasingly complex grid structure, uneven tide distribution, insufficient voltage supporting capability and the like bring new challenges to the safe and stable operation of the power grid. The power supply bottleneck appears in partial areas, and the load development needs can not be met. From the practical situation of the power grid, uneven power flow distribution is an important factor for limiting the transmission capacity of the power grid. The traditional power grid lacks an effective tide adjusting means, the system operation condition is improved by adopting a novel FACTS (Flexible Alternative Current Transmis System) device, and the improvement of the power grid conveying capacity is a realistic and ideal choice.
The unified power flow controller (Unified Power Flow Controller, UPFC) is used as the representative of 3 rd generation FACTS equipment, is the most comprehensive-function FACTS device so far, and can respectively or simultaneously realize multiple basic functions such as parallel compensation, series compensation, phase shifting, terminal voltage regulation and the like. UPFC can realize tide regulation in the aspect of power system stability, reasonably control active power and reactive power, improve the transmission capacity of a circuit and realize optimized operation; and in the dynamic aspect, through rapid reactive throughput, dynamically supporting the voltage of the access point, and improving the voltage stability of the system; and the damping of the system can be improved, and the stability of the power angle can be improved.
The conventional unified power flow controller has flexible and excellent control function, but is popularized and used in a power system and does not have the advantages of capacity and price. The traditional capacitor and the reactor can be used as line series compensation, but the flexibility and the action speed can not meet the requirement of accurate adjustment. The unified power flow controller needs a more flexible functional configuration and needs to combine series compensation with the unified power flow controller.
Disclosure of Invention
In order to meet the needs of the prior art, the invention provides a unified power flow controller combining series compensation and a converter.
The technical scheme of the invention is as follows:
the unified power flow controller comprises a reactor unit, a capacitor unit, a first converter, a second converter, a first switch, a second switch, a third switch, a series transformer and a parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the winding on the other side of the series transformer is connected with a power transmission line, and the winding is connected with the third switch in parallel;
the reactor unit is connected with a first switch in series and then connected with the first converter in parallel, and the other end of the first switch is connected with the series transformer;
the capacitor unit is connected in series with the second switch and then connected in parallel with the first converter, and the other end of the second switch is connected into the series transformer.
The invention further provides preferred embodiments as follows:
the capacitor unit comprises one capacitor or a series capacitor bank consisting of a plurality of capacitors or a parallel capacitor bank consisting of a plurality of capacitors; the parallel capacitor bank comprises an automatic switching switch, and the automatic switching switch is used for switching in and switching out of the capacitors in the parallel capacitor bank, so that the capacitance value of the parallel capacitor bank is adjusted.
The invention further provides preferred embodiments as follows:
the first switch comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch; the first switch is used for controlling the input and the withdrawal of the reactor unit;
the second switch comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch; the second switch is used for controlling the input and the output of the capacitor unit.
The third switch comprises a circuit breaker any one switch of an isolating switch and a power electronic switch or any two switches connected in parallel; the third switch is used for controlling the input and the output of the series transformer.
The invention further provides preferred embodiments as follows:
when the first switch and the second switch comprise the power electronic switch, the power electronic switch comprises a thyristor bidirectional switch, and the thyristor bidirectional switch comprises thyristors which are connected in anti-parallel;
the thyristor bidirectional switch of the first switch is also used for adjusting the equivalent impedance of the reactor unit by changing the triggering angle of the thyristor.
The invention further provides preferred embodiments as follows: the unified power flow controller comprises a fixed capacitive offset structure and a fixed inductive offset structure.
The invention further provides preferred embodiments as follows:
when the unified power flow controller is of a fixed capacity offset structure: the power supply comprises a capacitor unit, a first converter, a second switch, a third switch, a series transformer and a parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the winding on the other side of the series transformer is connected with a power transmission line, and the winding is connected with the third switch in parallel;
the capacitor unit is connected in series with the second switch and then connected in parallel with the first converter, and the other end of the second switch is connected into the series transformer.
The invention further provides preferred embodiments as follows:
when the unified power flow controller is of a fixed inductive offset structure: the power supply comprises a reactor unit, a first converter, a second converter, a first switch, a third switch, a series transformer and a parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the winding on the other side of the series transformer is connected with a power transmission line, and the winding is connected with the third switch in parallel;
the reactor unit is connected with the first switch in series and then connected with the first converter in parallel, and the other end of the first switch is connected with the series transformer.
The invention further provides preferred embodiments as follows: closing the first switch, opening the second and third switches, the unified power flow controller is used for realizing inductive offset compensation; closing the second switch, opening the first switch and the third switch, wherein the unified power flow controller is used for realizing capacitive offset compensation; and the first switch, the second switch and the third switch are disconnected, and the unified power flow controller is used for realizing offset-free compensation.
The invention further provides preferred embodiments as follows:
when the power electronic switch included in the first switch is a thyristor bidirectional switch, the second switch is closed so as to directly connect the capacitor unit with the first converter in parallel, the third switch is opened, and the triggering angle of the thyristor in the thyristor bidirectional switch is changed, so that the capacitive compensation or the inductive compensation is performed on the power transmission line:
when the triggering angle of the thyristor in the thyristor bidirectional switch is changed, the equivalent reactance of the reactor unit is smaller than the equivalent capacitance of the capacitor unit, and the unified power flow controller works in a capacitive compensation mode to perform capacitive compensation on the power transmission line;
when the triggering angle of the thyristor in the thyristor bidirectional switch is changed, the equivalent reactance of the reactor unit is larger than the equivalent capacitance of the capacitor unit, and then the unified power flow controller works in an inductive compensation mode to perform inductive compensation on the power transmission line.
The invention further provides preferred embodiments as follows: the first converter and the second converter comprise any one or more converters of a two-level converter, a three-level converter, a diode clamping converter, a flying capacitor converter, a modularized multi-level converter and an H-bridge cascading multi-level converter.
Compared with the closest prior art, the invention has the beneficial effects that:
1. the unified power flow controller combining series compensation and the converter can be used in a power transmission line or a distribution line for capacity or inductive adjustment, improves the transmission capacity of the line, improves the stability level of the system, controls the power flow of the line, enhances the damping of the system, solves the problem that the conventional unified power flow controller cannot be continuously and quickly adjusted in a large range, and reduces the cost of the unified power flow controller.
2. According to the unified power flow controller combining series compensation and the converter, provided by the invention, the insulation level of the reactor and the capacitor is reduced, and the dynamic response performance is improved; while the capacity of the voltage source converter may be reduced.
3. According to the unified power flow controller combining series compensation and the current converter, the reactor unit can realize the adjustment of capacitance capacity through the automatic switching switch, and the thyristor bidirectional switch connected in parallel with the reactor unit can continuously adjust reactance, so that the grading and continuous adjustment of equivalent capacitance reactance are realized, and the steady-state control is focused; the converter can provide continuous and rapid bidirectional regulation capability, focusing on dynamic control.
Drawings
Fig. 1: the embodiment of the invention discloses a unified power flow controller structure schematic diagram combining serial compensation and an inverter;
fig. 2: another unified power flow controller structure diagram combining series compensation and an inverter in the embodiment of the invention;
fig. 3: in the embodiment of the invention, a structure diagram of a unified power flow controller combining series compensation and an inverter is provided;
fig. 4: in the embodiment of the invention, a connection schematic diagram of a reactor unit and a capacitor unit is provided;
fig. 5: the equivalent impedance range of the current converter in the embodiment of the invention is shown in a schematic diagram;
fig. 6: the embodiment of the invention discloses a compensation range schematic diagram of a unified power flow controller combining series compensation and an inverter;
wherein, 101: a reactor unit; 102: a capacitor unit; 103: a first inverter; 104: a series transformer; 105: a second inverter; 106: and a parallel transformer.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The following describes a unified power flow controller with serial compensation and converter according to an embodiment of the present invention with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a unified power flow controller combined with a series compensation converter according to an embodiment of the present invention, as shown in the drawing, the unified power flow controller combined with a series compensation converter in this embodiment includes:
a reactor unit 101, a capacitor unit 102, a first converter 103, a series transformer 104, a second converter 105, a shunt transformer 106, a first switch, a second switch, and a third switch. Wherein,
one end of the first converter 103 is connected with one side winding of the series transformer 104 in parallel, the other end of the first converter is sequentially connected with the second converter 105 and the parallel transformer 106, and the other end of the parallel transformer 106 is connected into a bus or a power transmission line; the other side winding of the series transformer 104 is connected to the transmission line, which winding is connected in parallel with the third switch.
The reactor unit 101 is connected in series with a first switch, and then connected in parallel with the first converter 103, and the other end of the first switch is connected to the series transformer 104.
The capacitor unit 102 is connected in series with the second switch and then connected in parallel with the first converter 103, and the other end of the second switch is connected to the series transformer 104.
The capacitor unit 102 in the embodiment of the present invention includes one capacitor or a series capacitor group formed by a plurality of capacitors or a parallel capacitor group formed by a plurality of capacitors; the parallel capacitor bank includes an automatic switching switch for switching in and out of the capacitors in the parallel capacitor bank, thereby achieving capacitance adjustment of the parallel capacitor bank.
In the embodiment of the invention, the first switch comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch, and is used for controlling the input and the output of the reactor unit. When the power electronic switch is a thyristor bidirectional switch, the power electronic switch comprises a thyristor which is reversely connected in parallel, the second switch is closed to directly connect the capacitor unit with the first converter in parallel, the third switch is opened, the triggering angle of the thyristor in the thyristor bidirectional switch is changed, and the equivalent impedance of the reactor unit 101 is adjusted, so that the capacitive compensation or the inductive compensation is performed on the power transmission line:
when the trigger angle of the thyristor in the thyristor bidirectional switch is changed, the equivalent reactance of the reactor unit 101 is smaller than the equivalent capacitive reactance of the capacitor unit 102, and the unified power flow controller works in a capacitive compensation mode to perform capacitive compensation on the power transmission line.
When the trigger angle of the thyristor in the thyristor bidirectional switch is changed, the equivalent reactance of the reactor unit 101 is larger than the equivalent capacitance of the capacitor unit 102, and then the unified power flow controller works in an inductive compensation mode to perform inductive compensation on the power transmission line.
By controlling the first converter and the second converter, the phase angle of the line can be accurately adjusted by controlling the series impedance while the capacitive or inductive compensation function is realized.
In the embodiment of the invention, the second switch comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch, and is used for controlling the input and the output of the capacitor unit. The two switches connected in parallel can be a breaker connected in parallel with a disconnecting switch, the breaker is connected in parallel with a power electronic switch, and the disconnecting switch is connected in parallel with the power electronic switch.
The third switch in the embodiment of the invention comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch; and the third switch is used for controlling the input and the output of the series transformer.
In this embodiment, the unified power flow controller can be used to implement inductive offset compensation by closing the first switch, opening the second switch, and opening the third switch; closing the second switch, opening the first switch, opening the third switch, and enabling the unified power flow controller to be used for realizing capacitive offset compensation; the first switch is opened, the second switch is opened, the third switch is opened, and the unified power flow controller can be used to implement offset-free compensation.
In the embodiment of the present invention, the first converter 103 and the second converter 105 include any one or more converters of a two-level converter, a three-level converter, a diode clamp type converter, a flying capacitor type converter, a modularized multi-level converter and an H-bridge cascade type multi-level converter.
Fig. 2 is a schematic diagram of a unified power flow controller combined with a series compensation converter according to an embodiment of the present invention, where as shown in the drawing, the reactor unit 101 includes a reactor L, the capacitor unit 102 includes a capacitor C, the first converter 103 and the second converter 105 are converters VSC, and the series transformer 104 is a series transformer Tse. The reactor L is connected with the first switch in series and then connected with two ends of the first converter VSC in parallel, the capacitor C is connected with the second switch in series and then connected with two ends of the first converter VSC in parallel, the first switch and the second switch are respectively connected into one side winding of the series transformer Tse, the other side winding of the series transformer Tse is connected into a power transmission line between the system 1 and the system 2, and the two ends of the winding are connected with the third switch in parallel. The shunt transformer 106 is connected to the system side.
Fig. 3 is a schematic diagram of a unified power flow controller combined with a series compensation converter according to another embodiment of the present invention, where, as shown in the drawing, the reactor unit 101 includes a reactor L, the capacitor unit 102 includes a capacitor C, the converter 103 is a converter VSC, and the coupling transformer 104 is a coupling transformer Tse. The reactor L is connected with the first switch in series, the capacitor C is connected in parallel with two ends of a branch circuit formed by the reactor L and the first switch, a series-parallel branch circuit formed by the reactor L, the first switch and the capacitor C is connected with the converter VSC in series and then connected in parallel with two ends of one side winding of the coupling transformer Tse, the other side winding of the coupling transformer Tse is connected in a power transmission line between the system 1 and the system 2, and two ends of the winding are connected with the second switch in parallel.
Fig. 4 is a schematic diagram of connection between a reactor unit 101 and a capacitor unit 102, where the reactor unit 101 includes a reactor, the capacitor unit includes a capacitor and a switching switch, and the first switch is a thyristor bidirectional switch. The reactor is connected in series with the thyristor bidirectional switch and then connected in parallel with the capacitor, and the lightning arrester MOV and the mechanical switch S are respectively connected in parallel with the capacitor. Wherein the mechanical switch S is used to bypass the reactor unit 101 and the capacitor unit 102 when the reactor unit 101 or the capacitor unit 102 fails.
Fig. 5 is a schematic diagram of an equivalent impedance range of the first converter 103 according to an embodiment of the present invention, where the converter 103 according to the embodiment can obtain that the equivalent impedance range of the converter is within a circle with Zinv as a radius and the reactance value range is [ -X ] by adjusting the relation between the output voltage and the amplitude and phase angle of the current flowing through the transmission line inv ，+ X inv ]The capacitive compensation is set to be forward compensation.
Fig. 6 is a schematic diagram of a compensation range of a unified power flow controller combined with a series compensation converter according to an embodiment of the present invention, where the unified power flow controller combined with a series compensation converter includes a capacitive compensation mode and an inductive compensation mode, as shown in the figure, so that compensation of different impedances can be achieved. By controlling the first converter and the second converter, the phase angle of the line can be accurately adjusted by controlling the series impedance while the capacitive or inductive compensation function is realized.
The unified power flow controller comprises a fixed capacitive offset structure and a fixed inductive offset structure. Wherein,
1. fixed volume nature offset structure
The unified power flow controller in this embodiment includes a capacitor unit, a first converter the second converter, the second switch, the third switch, the series transformer and the parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the other side winding of the series transformer is connected with the power transmission line, and the winding is connected with the third switch in parallel; the capacitor unit is connected in series with the second switch and then connected in parallel with the first converter, and the other end of the second switch is connected into the series transformer.
2. Fixed inductive offset structure
The unified power flow controller in the embodiment comprises a reactor unit, a first converter, a second converter, a first switch, a third switch, a series transformer and a parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the other side winding of the series transformer is connected with the power transmission line, and the winding is connected with the third switch in parallel; the reactor unit is connected in series with the first switch and then connected in parallel with the first converter, and the other end of the first switch is connected into the series transformer.
1. Capacitive compensation mode
In the present embodiment, the capacitance reactance of the capacitor unit 102 is set to X c The equivalent impedance range of the first converter 103 is within a circle with Zinv as radius, and the capacitive compensation is forward compensation, then the compensation range of the unified power flow controller combined with the converter at the device side in the capacitive compensation mode is capacitive impedance X c Vector sum with the inverter impedance Zinv.
In this embodiment, the triggering angle of the thyristor of the first switch may be continuously adjusted, and the impedance of the first converter 103 connected in series may also be adjusted, so that the first converter 103 has a faster response speed, and may be used to enhance the damping of the system, and further enhance the dynamic response capability of the system. By inputting different capacitor capacities, capacitance X can be obtained c The unified power flow controller combining the series compensation and the current converter realizes dynamic adjustment while carrying out hierarchical adjustment, and has a larger dynamic adjustment range.
2. Perceptual compensation mode
In this embodiment, the reactance of the reactor is set to X L The equivalent impedance range of the first converter 103 is within a circle with Zinv as radius, and the compensation range of the unified power flow controller combined with the converter in series compensation mode at the device side is the reactance X L And the converter impedance ZiVector sum of nv.
In this embodiment, if the power transmission line fails, in order to reduce the short-circuit current of the power transmission line and reduce the energy absorbed by the lightning arrester, the thyristors in the first switch are controlled to be fully turned on, and meanwhile, the impedance value of the first converter 103 series connection can be quickly adjusted, so as to improve the dynamic response capability of the system. When realizing the dynamic adjustment from the capacitive compensation mode to the inductive compensation mode, the maximum inductive compensation of the unified power flow controller combined by the series compensation and the converter at the device side is-X L -Z inv Maximum capacitive compensation is X c +Z inv 。
The following describes the working procedure of the unified power flow controller combined by serial compensation and converter, which is preferred in the embodiment of the present invention:
1. unified power flow controller unaccessed system combining serial compensation and converter
Before the unified power flow controller combined by the series compensation and the current converter is connected into the system, the second switch is closed, the first current converter 103 and the thyristor bidirectional switch of the first switch are locked, and the unified power flow controller combined by the series compensation and the current converter is in a bypass state, so that no influence is caused on the running state of the system.
2. Unified power flow controller access system combining serial compensation and converter
And the unified power flow controller combined with the series compensation and the converter determines the impedance value to be compensated according to the upper layer scheduling instruction and the actual operation condition. When the reactance of the long-distance power transmission line is large, the operation is required to be in a capacitive compensation mode, the reactance of the power transmission line is compensated, and the transmission loss is reduced. When the power transmission line is overloaded due to short-circuit faults or load increase, tripping of parallel lines and the like, the power transmission line needs to operate in an inductive impedance compensation mode to limit the current amplitude. By adjusting the thyristor trigger angle of the thyristor bidirectional switch in the first switch, the unified power flow controller combined by the series compensation and the converter works in a capacitive compensation mode or an inductive compensation mode, and meanwhile, the operation of the first converter 103 is controlled according to the requirement of system damping adjustment, so that the dynamic response of the system is improved.
The protection measures of the unified power flow controller combined by series compensation and the converter in the embodiment of the invention mainly comprise:
1. when a fault occurs at the system side, for example, when a single-phase earth fault occurs in a line or the line flows excessively, the second switch needs to be closed to withdraw from the operation of the first converter 103 in order to protect the unified power flow controller combined with the series compensation converter.
2. When a fault occurs in the first converter 103, the switching device trigger pulse of the first converter 103 needs to be locked, the second switch is closed, and the operation of the first converter 103 is stopped, so that the reactor unit 101 and the capacitor unit 102 can still perform capacitive compensation or inductive compensation.
Those skilled in the art will appreciate that implementing all or part of the above-described methods in accordance with the embodiments may be accomplished by way of a computer program stored on a computer readable storage medium, which when executed may comprise the steps of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only memory (ROM), a random access memory (Random Access Memory, RAM), or the like. Meanwhile, the invention does not refer to equipment such as lightning arresters, gaps and the like for protecting capacitors, series transformers, converters and switching devices thereof, and does not refer to equipment design, manufacture and engineering practice. In practical engineering implementation, there are many isolation switches, circuit breakers, current measurement devices and voltage measurement devices which are not labeled in the drawings of the embodiment, and these devices are not present when the engineering is not actually implemented.
The unified power flow controller combining series compensation and the converter in the embodiment of the invention can be used in a power transmission line or a distribution line for capacity or inductive adjustment, improves the transmission capacity of the line, improves the stability level of the system, controls the power flow of the line, enhances the damping of the system, solves the problem that the conventional unified power flow controller cannot be continuously and quickly adjusted in a large range, and reduces the cost of the unified power flow controller.
Another embodiment of the invention is shown in fig. 3, where the reactor unit, the capacitor unit and the converter unit are connected in parallel and then connected to one side of the series transformer. By adjusting the thyristor firing angle of the thyristor bidirectional switch in the first switch, the reactance value of the incorporated reactor unit is adjusted, the capacitance value of the incorporated capacitor can be adjusted by automatic switching of the capacitor bank, and the converter unit can realize an impedance circle with Zinv as a radius. The impedance injected to the system side can be controlled by equivalent impedance adjustment of the reactor unit, the capacitor unit and the inverter, thereby realizing dynamic adjustment of a wide range of impedance.
It should be noted that the case of connecting the inductor and the capacitor in series with the inverter is not limited to the structure shown in the embodiment, and any case of implementing a wide range of series compensation by adding or subtracting the inductor and the capacitor falls within the scope of the present invention. It is within the scope of the invention that the parallel side of the unified power flow control may be connected to the bus of the present line as well as to other lines.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (8)
1. The unified power flow controller is characterized by comprising a reactor unit, a capacitor unit, a first converter, a second converter, a first switch, a second switch, a third switch, a series transformer and a parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the winding on the other side of the series transformer is connected with a power transmission line, and the winding is connected with the third switch in parallel;
the reactor unit is connected with a first switch in series and then connected with the first converter in parallel, and the other end of the first switch is connected with the series transformer;
the capacitor unit is connected in series with a second switch and then connected in parallel with the first converter, and the other end of the second switch is connected into the series transformer;
when the power electronic switch included in the first switch is a thyristor bidirectional switch, the second switch is closed so as to directly connect the capacitor unit with the first converter in parallel, the third switch is opened, and the triggering angle of the thyristor in the thyristor bidirectional switch is changed, so that the capacitive compensation or the inductive compensation is carried out on the power transmission line;
when the triggering angle of the thyristor in the thyristor bidirectional switch is changed, the equivalent reactance of the reactor unit is smaller than the equivalent capacitance of the capacitor unit, and the unified power flow controller works in a capacitive compensation mode to perform capacitive compensation on the power transmission line;
when the triggering angle of the thyristor in the thyristor bidirectional switch is changed, the equivalent reactance of the reactor unit is larger than the equivalent capacitance of the capacitor unit, and the unified power flow controller works in an inductive compensation mode to perform inductive compensation on the power transmission line;
closing the first switch, and when the second switch and the third switch are opened, the unified power flow controller is used for realizing inductive offset compensation; closing the second switch, opening the first switch and the third switch, wherein the unified power flow controller is used for realizing capacitive offset compensation; the first switch, the second switch and the third switch are disconnected, and the unified power flow controller is used for realizing offset-free compensation;
the capacitance reactance of the capacitor unit is X c The equivalent impedance range of the first converter is within a circle with Zinv as radius, and the capacitive compensation is forward compensation, and the compensation range of the unified power flow controller combined with the converter at the device side in the capacitive compensation mode is capacitive impedance X c Vector sum with inverter impedance Zinv;
the reactor reactance of unit X L The compensation range of the unified power flow controller combined by series compensation and the converter in the inductive compensation mode at the device side is reactance X L And the current converter resistorVector sum of Zinv resistance;
in the dynamic adjustment of the capacitive compensation mode to the inductive compensation mode, the maximum inductive compensation of the unified power flow controller at the device side is-X L -Zinv, maximum capacitive compensation is xc+zinv.
2. A unified power flow controller in combination with a series compensation and converter as claimed in claim 1, characterized in that,
the capacitor unit comprises one capacitor or a series capacitor bank consisting of a plurality of capacitors or a parallel capacitor bank consisting of a plurality of capacitors; the parallel capacitor bank comprises an automatic switching switch, and the automatic switching switch is used for switching in and switching out of the capacitors in the parallel capacitor bank, so that the capacitance value of the parallel capacitor bank is adjusted.
3. A unified power flow controller in combination with a series compensation and converter as claimed in claim 1, characterized in that,
the first switch comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch; the first switch is used for controlling the input and the withdrawal of the reactor unit;
the second switch comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch; the second switch is used for controlling the input and the withdrawal of the capacitor unit;
the third switch comprises any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch; the third switch is used for controlling the input and the output of the series transformer.
4. A unified power flow controller in combination with a series compensation and converter as claimed in claim 3,
when the first switch and the second switch comprise the power electronic switch, the power electronic switch comprises a thyristor bidirectional switch, and the thyristor bidirectional switch comprises thyristors which are connected in anti-parallel;
the thyristor bidirectional switch of the first switch is also used for adjusting the equivalent impedance of the reactor unit by changing the triggering angle of the thyristor.
5. A unified power flow controller in combination with a series compensation converter as claimed in claim 1 wherein the unified power flow controller comprises a fixed capacitive offset structure and a fixed inductive offset structure.
6. A unified power flow controller in combination with a series compensation and converter as claimed in claim 5, it is characterized in that the method comprises the steps of,
when the unified power flow controller is of a fixed capacity offset structure: the power supply comprises a capacitor unit, a first converter, a second switch, a third switch, a series transformer and a parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the winding on the other side of the series transformer is connected with a power transmission line, and the winding is connected with the third switch in parallel;
the capacitor unit is connected in series with the second switch and then connected in parallel with the first converter, and the other end of the second switch is connected into the series transformer.
7. A unified power flow controller in combination with a series compensation converter as claimed in claim 5 wherein,
when the unified power flow controller is of a fixed inductive offset structure: the power supply comprises a reactor unit, a first converter, a second converter, a first switch, a third switch, a series transformer and a parallel transformer;
one end of the first converter is connected with one side winding of the series transformer in parallel, the other end of the first converter is sequentially connected with the second converter and the parallel transformer, and the other end of the parallel transformer is connected into a bus or a power transmission line; the winding on the other side of the series transformer is connected with a power transmission line, and the winding is connected with the third switch in parallel;
the reactor unit is connected with the first switch in series and then connected with the first converter in parallel, and the other end of the first switch is connected with the series transformer.
8. A unified power flow controller in combination with a series compensation and converter as claimed in claim 1, it is characterized in that the method comprises the steps of, the first converter and the second converter comprise any one or more converters of a two-level converter, a three-level converter, a diode clamping converter, a flying capacitor converter, a modularized multi-level converter and an H-bridge cascading multi-level converter.
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| WO2019075703A1 (en) * | 2017-10-19 | 2019-04-25 | 全球能源互联网研究院有限公司 | Mixed power flow control device |
| CN108054759B (en) * | 2017-12-18 | 2024-04-30 | 北方工业大学 | Dynamic voltage regulating device and method for power distribution network |
| CN108092250B (en) * | 2017-12-20 | 2023-05-12 | 南京南瑞继保电气有限公司 | Fault current limiting equipment and control method |
| CN109687466B (en) * | 2018-12-30 | 2021-06-08 | 广东电网有限责任公司 | Method and device for selecting address of power flow router |
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