CN105680453B - Improved parallel hybrid unified power flow controller - Google Patents
Improved parallel hybrid unified power flow controller Download PDFInfo
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- CN105680453B CN105680453B CN201610143754.1A CN201610143754A CN105680453B CN 105680453 B CN105680453 B CN 105680453B CN 201610143754 A CN201610143754 A CN 201610143754A CN 105680453 B CN105680453 B CN 105680453B
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- 230000002457 bidirectional effect Effects 0.000 claims description 38
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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
- H02J3/18—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
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
- H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
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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
- H02J3/20—Arrangements for adjusting, eliminating or compensating reactive power in networks in long overhead lines
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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
- Y02E40/10—Flexible AC transmission systems [FACTS]
Abstract
The invention provides an improved parallel hybrid unified power flow controller, which comprises a first converter, a second converter, first offset compensation equipment, second offset compensation equipment, a series transformer and a parallel transformer; the first winding of the series transformer is connected in series with a power transmission line or a bus of an alternating current system, the second winding is connected in parallel with an alternating current end of the first converter, and the third winding is connected in parallel with first offset compensation equipment; the first winding of the parallel transformer is connected in parallel to a power transmission line or a bus of an alternating current system, the second winding is connected in parallel to an alternating current end of the second converter, and the third winding is connected in parallel to the second offset compensation equipment. Compared with the prior art, the improved parallel hybrid unified power flow controller provided by the invention can provide a certain amount of capacitive or inductive offset by the offset compensation equipment, reduce the cost of the converter, improve the utilization rate of the transformer, and can also be used in a power transmission line or a distribution line, improve the transmission capacity of the line and improve the stability level of the system.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to an improved parallel hybrid unified power flow controller.
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; in the dynamic aspect, the voltage of the access point can be dynamically supported through rapid reactive throughput, so that the voltage stability of the system is improved; 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 more flexible functional configuration, needs to combine series compensation with the unified power flow controller, and the simple fixed-capacity series compensation cannot meet the system requirements of complex changes.
Disclosure of Invention
In order to meet the needs of the prior art, the invention provides an improved parallel hybrid unified power flow controller.
The technical scheme of the invention is as follows:
the unified power flow controller comprises a first converter, a second converter the first offset compensation equipment, the second offset compensation equipment, the series transformer and the parallel transformer;
the series transformer is a three-winding transformer: the first winding is connected in series with a power transmission line or a bus of an alternating current system, and bypass switches are connected in parallel at two ends of the winding; the second winding is connected with the alternating-current end of the first converter in parallel; the third winding is connected with the first offset compensation equipment in parallel;
the parallel transformer is a three-winding transformer: the first winding is connected in parallel to a power transmission line or a bus of an alternating current system, the second winding is connected in parallel to an alternating current end of the second converter, and the third winding is connected in parallel to the second offset compensation equipment;
the direct current end of the first converter is connected with the direct current end of the second converter.
One preferred embodiment provided by the invention is:
when the first converter adopts a three-phase bridge converter, one end of the first offset compensation equipment is connected with a third winding of the series transformer, and the other end of the first offset compensation equipment is connected with a neutral point of the series transformer or any neutral point of other neutral points in an alternating current system;
when the second converter adopts a three-phase full-bridge converter, one end of the second offset compensation equipment is connected with the third winding of the parallel transformer, and the other end of the second offset compensation equipment is connected with the neutral point of the parallel transformer or any neutral point of other neutral points in an alternating current system.
One preferred embodiment provided by the invention is:
the first offset compensation equipment and the second offset compensation equipment comprise any one of capacitive offset compensation equipment, inductive offset compensation equipment and bidirectional offset compensation equipment;
the capacitive offset compensation apparatus includes a capacitor unit and a first switching device connected in series;
the inductive offset compensation apparatus comprises a reactor unit and a second switching device connected in series;
the bi-directional offset compensation equipment comprises the capacitive offset compensation equipment and the inductive offset compensation equipment which are connected in parallel.
One preferred embodiment provided by the invention is:
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 which is used for switching in and switching out the capacitors in the parallel capacitor bank so as to realize the capacitance adjustment of the parallel capacitor bank;
the reactor unit comprises a reactor, or a parallel reactor group formed by connecting a plurality of reactors in parallel, or a series reactor group formed by connecting a plurality of reactors in series; the reactor of the series reactor group is provided with a tap.
One preferred embodiment provided by the invention is: the first switching device and the second switching device comprise any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch;
the power electronic switch comprises a thyristor bidirectional switch composed of thyristors connected in inverse parallel, and the equivalent impedance of the reactor unit is adjusted by changing the firing angle of the thyristors.
One preferred embodiment provided by the invention is: the bidirectional offset type compensation device comprises a capacitive offset mode and a inductive offset mode;
the capacitive offset mode includes:
the first switching device is closed, the second switching device is opened, and the bidirectional offset compensation equipment works in a capacitive offset mode; or,
when the second switching device adopts thyristor bidirectional switching, the equivalent reactance of the reactor unit is smaller than the equivalent capacitance of the capacitor unit by adjusting the triggering angle of the thyristor, and the bidirectional offset type compensation equipment works in a capacitive offset mode;
the perceptual offset mode includes:
the first switching device is opened, the second switching device is closed, and the bidirectional offset compensation equipment works in an inductive offset mode; or,
when the second switching device adopts thyristor bidirectional switching, the trigger angle of the thyristor is adjusted to enable the equivalent reactance of the reactor unit to be larger than the equivalent capacitance of the capacitor unit, so that the bidirectional offset type compensation equipment works in an inductive offset mode.
One preferred embodiment provided by the invention is: the unified power flow controller comprises a serial side offset structure and a parallel side offset structure.
One preferred embodiment provided by the invention is: when the unified power flow controller adopts a serial side offset structure, the unified power flow controller comprises: the first converter, the second converter, the first offset compensation equipment, the series transformer and the parallel transformer;
the series transformer is a three-winding transformer: the first winding is connected in series with a power transmission line or a bus of an alternating current system, and bypass switches are connected in parallel at two ends of the winding; the second winding is connected with the alternating-current end of the first converter in parallel; the third winding is connected with the first offset compensation equipment in parallel; the direct current end of the first converter is connected with the direct current end of the second converter;
the parallel transformer is a double-winding transformer: the first winding is connected in parallel to a power transmission line or a bus of an alternating current system, and the second winding is connected in parallel to an alternating current end of the second converter.
One preferred embodiment provided by the invention is: when the unified power flow controller adopts a parallel side offset structure, the method comprises the following steps: a first converter, a second offset compensation equipment a series transformer and a parallel transformer;
the series transformer is a double-winding transformer: the first winding is connected in series to a transmission line or bus of an ac system, the two ends of the winding are connected with a bypass switch in parallel; the second winding is connected with the alternating current end of the first converter in parallel, and the direct current end of the first converter is connected with the direct current end of the second converter;
the parallel transformer is a three-winding transformer: the first winding is connected in parallel to a power transmission line or a bus of an alternating current system, the second winding is connected in parallel to an alternating current end of the second converter, and the third winding is connected in parallel to the second offset compensation equipment.
One preferred embodiment provided by the invention is: the first current converter and the second current converter comprise any one or at least two of a two-level current converter, a three-level current converter, a diode clamping type current converter, a flying capacitor type current converter, a modularized multi-level current converter and an H-bridge cascading type multi-level current converter;
the structures of the first current converter and the second current converter adopt any one of a single-phase structure, a three-phase structure and a three-single-phase structure.
Compared with the closest prior art, the invention has the beneficial effects that:
1. the improved parallel hybrid unified power flow controller provided by the invention can be used in a power transmission line or a power 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. the improved parallel hybrid unified power flow controller provided by the invention reduces the insulation level of the reactor and the capacitor and improves the dynamic response performance; while the capacity of the voltage source converter may be reduced.
3. According to the improved parallel hybrid unified power flow controller provided by the invention, 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 an improved parallel hybrid unified power flow controller structure schematic diagram;
fig. 2: the embodiment of the invention provides another improved parallel hybrid unified power flow controller structure schematic diagram;
fig. 3: the embodiment of the invention also discloses an improved parallel hybrid unified power flow controller structure schematic diagram;
fig. 4: in the embodiment of the invention, a schematic diagram of a serial side offset structure is provided;
fig. 5: in the embodiment of the invention, a parallel side offset structure schematic diagram is provided;
fig. 6: the embodiment of the invention provides a schematic structural diagram of inductive offset compensation equipment;
fig. 7: the embodiment of the invention provides a structural schematic diagram of a capacitive offset type compensation device;
fig. 8: bidirectional offset in embodiments of the present invention schematic structural diagram of the type compensation equipment;
fig. 9: another bidirectional offset type compensation equipment structure schematic diagram in the embodiment of the invention;
wherein, 101: a first inverter; 102: a second inverter; 103: a first offset compensation device; 104: a second offset compensation device; 105: a series transformer; 106: a parallel transformer; 107: a bypass switch; 108: ground resistance.
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.
An improved parallel hybrid unified power flow controller according to an embodiment of the present invention is described below with reference to the accompanying drawings.
Fig. 1 is a schematic diagram of an improved parallel hybrid unified power flow controller according to an embodiment of the present invention, where the unified power flow controller includes a first converter 101, a second converter 102, a first offset compensation device 103, a second offset compensation device 104, a series transformer 105, and a parallel transformer 106. Wherein,
the series transformer 105 is a three-winding transformer: the first winding is connected in series with a power transmission line or bus of an alternating current system, and two ends of the winding are connected with a bypass switch 107 in parallel; the second winding is connected in parallel with the ac end of the first converter 101; the third winding is connected in parallel with the first offset compensation means 103.
The shunt transformer 106 is a three-winding transformer: the first winding is connected in parallel to a transmission line or bus of an alternating current system, the second winding is connected in parallel with the ac-side of the second converter 102 and the third winding is connected in parallel with the second offset compensation arrangement 104.
The dc terminals of the first converter 101 are interconnected with the dc terminals of the second converter 102.
The first converter 101 and the second converter 102 in the invention comprise any one or at least two 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; the structures of the first inverter 101 and the second inverter 102 each adopt any one of a single-phase structure, a three-phase structure, and a three-single-phase structure.
Fig. 2 is a schematic structural diagram of another improved parallel hybrid unified power flow controller according to an embodiment of the present invention, and fig. 3 is a schematic structural diagram of another improved parallel hybrid unified power flow controller according to an embodiment of the present invention, as shown in the drawings, in which:
when the first converter 101 is a three-phase bridge converter, one end of the first offset compensation equipment 103 is connected to the third winding of the series transformer 105, and the other end is connected to the neutral point of the series transformer 105 or the neutral point of any one of the transmission lines in the ac system. When the second converter 102 adopts a three-phase bridge converter, one end of the second offset compensation equipment 104 is connected to the third winding of the parallel transformer 104, and the other end is connected to the neutral point of the parallel transformer 104 or the neutral point of any one of the transmission lines in the ac system.
The unified power flow controller comprises a serial side offset structure and a parallel side offset structure, wherein the serial side offset structure is connected with the parallel side offset structure;
1. series side offset structure
Fig. 4 is a schematic diagram of a serial side offset structure of the embodiment of the present invention, where, as shown in the drawing, when the unified power flow controller in this embodiment adopts the serial side offset structure, the method includes: a first converter 101, a second converter 102, a first offset compensation arrangement 103, a series transformer 105 and a shunt transformer 106.
The series transformer 105 is a three-winding transformer: the first winding is connected in series with a power transmission line or bus of an alternating current system, and two ends of the winding are connected with a bypass switch 107 in parallel; the second winding is connected in parallel with the ac end of the first converter 101; the third winding is connected in parallel with the first offset compensation device 103; the direct current end of the first converter 101 is connected with the direct current end of the second converter 102;
the shunt transformer 106 is a dual winding transformer: the first winding is connected in parallel to a transmission line or a bus of the ac system, and the second winding is connected in parallel to an ac end of the second inverter 102.
In this embodiment, the reactor unit, the capacitor unit and the inverter 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 switching device, 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.
2. Parallel side offset structure
Fig. 5 is a schematic diagram of a parallel side offset structure in an embodiment of the present invention, where, as shown in the drawing, when a parallel side offset structure is adopted in a unified power flow controller in this embodiment, the parallel side offset structure includes: a first converter 101, a second converter 102, a second offset compensation arrangement 104, a series transformer 105 and a shunt transformer 106.
The series transformer 105 is a dual winding transformer: the first winding is connected in series with a power transmission line or bus of an alternating current system, and two ends of the winding are connected with a bypass switch 107 in parallel; the second winding is connected in parallel with the alternating current end of the first converter 101, and the direct current end of the first converter 101 is connected with the direct current end of the second converter 102;
the shunt transformer 106 is a three-winding transformer: the first winding is connected in parallel to a transmission line or bus of the ac system, the second winding is connected in parallel to the ac end of the second converter 102, and the third winding is connected in parallel to the second offset compensation arrangement 104.
The first offset compensation equipment and the second offset compensation equipment in the invention comprise any one of a capacitive offset compensation equipment, a inductive offset compensation equipment or a bidirectional offset compensation equipment, wherein:
fig. 6 is a schematic structural diagram of an inductive offset type compensation apparatus according to an embodiment of the present invention, and as shown in the drawing, the inductive offset type compensation apparatus according to the embodiment includes a reactor unit and a second switching device connected in series.
Fig. 7 is a schematic structural diagram of a capacitive offset compensation apparatus according to an embodiment of the present invention, where the capacitive offset compensation apparatus includes a capacitor unit and a first switching device connected in series.
Fig. 8 is a schematic structural diagram of a bidirectional offset type compensation device according to an embodiment of the present invention, and as shown in the drawing, the bidirectional offset type compensation device in this embodiment includes a capacitive offset type compensation device and a inductive offset type compensation device connected in parallel. The bi-directional offset compensation apparatus includes a capacitive offset mode and a inductive offset mode.
Fig. 9 is a schematic structural diagram of another bidirectional offset type compensation equipment according to an embodiment of the present invention, and as shown in the drawing, the bidirectional offset type compensation equipment in this embodiment includes a reactor, a capacitor, a bidirectional thyristor switch, a lightning arrester MOV and a bypass switch S.
1. The capacitive offset mode includes two technical schemes:
the first technical scheme is as follows:
the first switching device is closed and the second switching device is opened, and the bidirectional offset compensation equipment works in a capacitive offset mode.
The second technical scheme is as follows:
when the second switching device adopts thyristor bidirectional switch, the trigger angle of the thyristor is adjusted to make the equivalent reactance of the reactor unit smaller than the equivalent capacitance of the capacitor unit, so that the bidirectional offset type compensation equipment works in a capacitive offset mode.
2. The perceptual offset mode includes two technical schemes:
the first technical scheme is as follows:
the first switching means is opened and the second switching means is closed, the bi-directional offset compensation apparatus operates in an inductive offset mode.
A second technical scheme;
when the second switching device adopts a thyristor bidirectional switch, the trigger angle of the thyristor is adjusted to enable the equivalent reactance of the reactor unit to be larger than the equivalent capacitance of the capacitor unit, so that the bidirectional offset type compensation equipment works in an inductive offset mode.
The reactor unit, the capacitor unit and the switching device in the invention have the following structures:
1. capacitor unit
The capacitor unit in this embodiment includes one capacitor or a series capacitor bank composed of a plurality of capacitors or a parallel capacitor bank composed of 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 to effect capacitance adjustment of the parallel capacitor bank.
1. Capacitive compensation mode
In this embodiment, the capacitance reactance of the capacitor unit 101 is set to Xc, the equivalent impedance range of the first converter 101 is within a circle with Zinv as a radius, and the capacitive compensation is forward compensation, so that the compensation range of the improved parallel hybrid unified power flow controller in the capacitive compensation mode at the device side is the vector sum of the capacitance reactance Xc and the converter impedance Zinv.
In this embodiment, the triggering angle of the thyristor of the first switching device may be continuously adjusted, and the impedance of the first converter 101 connected in series may also be adjusted, so that the first converter 101 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. The capacitive reactance Xc can be obtained by inputting different capacitor capacities, so that the improved parallel hybrid unified power flow controller realizes dynamic adjustment while carrying out hierarchical adjustment, and has a larger dynamic adjustment range.
2. Reactor unit
The reactor unit in this embodiment includes one reactor, or a parallel reactor group formed by connecting a plurality of reactors in parallel, or a series reactor group formed by connecting a plurality of reactors in series; the reactors of the series reactor group are provided with taps.
In this embodiment, the reactance of the reactor is set to be XL, the equivalent impedance range of the first converter 101 is within a circle with Zinv as a radius, and the capacitive compensation is forward compensation, so that the compensation range of the improved parallel hybrid unified power flow controller in the inductive compensation mode at the device side is the vector sum of the reactance XL and the converter impedance Zinv.
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 second switching device are controlled to be fully turned on, and meanwhile, the impedance value of the first converter 101 series connection can be quickly adjusted, so as to improve the dynamic response capability of the system. When dynamic adjustment of the capacitive compensation mode to the inductive compensation mode is realized, the maximum inductive compensation of the improved parallel hybrid unified power flow controller at the device side is-XL-Zinv, and the maximum capacitive compensation is Xc+Zinv.
3. First and second switching devices
In this embodiment, the first switching device and the second switching device each include any one switch of a circuit breaker, an isolating switch and a power electronic switch or any two switches connected in parallel;
the power electronic switch comprises a thyristor bidirectional switch consisting of thyristors connected in anti-parallel, and the equivalent impedance of the reactor unit is adjusted by changing the firing angle of the thyristors.
The following describes the operation procedure of the improved parallel hybrid unified power flow controller according to the preferred embodiment of the present invention:
1. improved parallel hybrid unified power flow controller unaccessed system
Before the improved parallel hybrid unified power flow controller is connected into the system, the bypass switch device is closed, the thyristor bidirectional switches of the first converter 101, the first switch device and the second switch device are locked, and the improved parallel hybrid unified power flow controller is in a bypass state and does not influence the running state of the system.
2. Improved parallel hybrid unified power flow controller access system
The improved parallel hybrid unified power flow controller 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. The improved parallel hybrid unified power flow controller works in a capacitive compensation mode or an inductive compensation mode by controlling the on-off of the first switching device and the second switching device or adjusting the triggering angle of the thyristors of the thyristor bidirectional switch in the second switching device, and meanwhile, the operation of the first converter 101 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 improved parallel hybrid unified power flow controller in the embodiment of the invention mainly comprise:
1. in order to protect the improved parallel hybrid unified power flow controller when a fault occurs on the system side, such as a single-phase earth fault or line overcurrent, the second switching device needs to be closed and the operation of the first converter 101 is stopped.
2. When a fault occurs in the first converter 101, the switching device trigger pulse of the first converter 101 needs to be locked out, and the operation of the first converter 101 is stopped, and at this time, the reactor unit and the capacitor unit can still perform capacitive compensation or inductive compensation.
Those skilled in the art will appreciate that all or part of the processes implementing the methods of the embodiments described above may be implemented by computer programs instructing the relevant hardware, the program may be stored in a computer readable storage medium, and the program may include the flow of the embodiments of the methods described above when executed. 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 isolating switches, circuit breakers, current measuring devices and voltage measuring devices which are not marked in the drawings of the embodiment, these devices are not present when the engineering is not actually implemented.
The improved parallel hybrid unified power flow controller provided by the embodiment of the invention can be used in a power transmission line or a power distribution line for capacity or inductive adjustment, so that the transmission capacity of the line is improved, the stable level of the system is improved, the power flow of the line is controlled, the damping of the system is enhanced, the problem that the conventional unified power flow controller cannot be continuously and quickly adjusted in a large range is solved, and the cost of the unified power flow controller is reduced.
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 (6)
1. An improved parallel hybrid unified power flow controller, characterized in that the unified power flow controller comprises a first converter, a second converter, a first offset compensation device, a second offset compensation device, a series transformer and a parallel transformer;
the series transformer is a three-winding transformer: the first winding is connected in series with a power transmission line or a bus of an alternating current system, and bypass switches are connected in parallel at two ends of the winding; the second winding is connected with the alternating-current end of the first converter in parallel; the third winding is connected with the first offset compensation equipment in parallel;
the parallel transformer is a three-winding transformer: the first winding is connected in parallel to a power transmission line or a bus of an alternating current system, the second winding is connected in parallel to an alternating current end of the second converter, and the third winding is connected in parallel to the second offset compensation equipment;
the direct current end of the first converter is connected with the direct current end of the second converter;
the first offset compensation equipment and the second offset compensation equipment comprise any one of capacitive offset compensation equipment, inductive offset compensation equipment or bidirectional offset compensation equipment;
the capacitive offset compensation apparatus includes a capacitor unit and a first switching device connected in series;
the inductive offset compensation apparatus comprises a reactor unit and a second switching device connected in series;
the bidirectional offset type compensation equipment comprises the capacitive offset type compensation equipment and the inductive offset type compensation equipment which are connected in parallel;
the capacitor unit comprises a capacitor or consists of a plurality of capacitors a series capacitor bank consisting of a plurality of capacitors; the parallel capacitor bank comprises an automatic switching switch which is used for switching in and switching out the capacitors in the parallel capacitor bank so as to realize the capacitance adjustment of the parallel capacitor bank;
the reactor unit comprises a reactor, or a parallel reactor group formed by connecting a plurality of reactors in parallel, or a series reactor group formed by connecting a plurality of reactors in series; the reactor of the series reactor group is provided with a tap;
the first switching device and the second switching device comprise any one switch or any two switches connected in parallel of a breaker, an isolating switch and a power electronic switch;
the power electronic switch comprises a thyristor bidirectional switch composed of thyristors connected in reverse parallel, and the equivalent impedance of the reactor unit is adjusted by changing the triggering angle of the thyristors;
the bidirectional offset type compensation device comprises a capacitive offset mode and a inductive offset mode;
the capacitive offset mode includes:
the first switching device is closed, the second switching device is opened, and the bidirectional offset compensation equipment works in a capacitive offset mode; or,
when the second switching device adopts thyristor bidirectional switching, the equivalent reactance of the reactor unit is smaller than the equivalent capacitance of the capacitor unit by adjusting the triggering angle of the thyristor, and the bidirectional offset type compensation equipment works in a capacitive offset mode;
the capacitive reactance of the capacitor unit is Xc, the equivalent impedance range of the first converter is within a circle with Zinv as radius, and the capacitive compensation is forward compensation, the compensation range of the improved parallel hybrid unified power flow controller at the device side in the capacitive compensation mode is the vector sum of the capacitive reactance Xc and the converter impedance Zinv;
the perceptual offset the modes include:
the first switching device is opened, the second switching device is closed, and the bidirectional offset compensation equipment works in an inductive offset mode; or,
when the second switching device adopts thyristor bidirectional switching, the equivalent reactance of the reactor unit is larger than the equivalent capacitance of the capacitor unit by adjusting the triggering angle of the thyristor, and the bidirectional offset type compensation equipment works in an inductive offset mode;
the reactance of the reactor is XL, the equivalent impedance range of the first converter is within a circle with Zinv as a radius, and the capacitive compensation is forward compensation, so that the compensation range of the improved parallel hybrid unified power flow controller at the device side in the inductive compensation mode is the vector sum of the reactance XL and the converter impedance Zinv.
2. An improved parallel hybrid unified power flow controller according to claim 1 wherein,
when the first converter adopts a three-phase bridge converter, one end of the first offset compensation equipment is connected with the second winding of the series transformer, and the other end of the first offset compensation equipment is connected with the neutral point of the series transformer or any neutral point of other neutral points in an alternating current system;
when the second converter adopts a three-phase bridge converter, one end of the second offset compensation equipment is connected with the second winding of the parallel transformer, and the other end of the second offset compensation equipment is connected with the neutral point of the parallel transformer or any neutral point of other neutral points in an alternating current system.
3. An improved parallel hybrid unified power flow controller as in claim 1 wherein the unified power flow controller comprises a series side offset configuration and a parallel side offset configuration.
4. An improved parallel hybrid unified power flow controller as in claim 3 wherein said unified power flow controller, when in a series side offset configuration, comprises: the first converter, the second converter, the first offset compensation equipment, the series transformer and the parallel transformer;
the series transformer is a three-winding transformer: the first winding is connected in series with a power transmission line or a bus of an alternating current system, and bypass switches are connected in parallel at two ends of the winding; the second winding is connected with the alternating-current end of the first converter in parallel; the third winding is connected with the first offset compensation equipment in parallel; the direct current end of the first converter is connected with the direct current end of the second converter;
the parallel transformer is a double-winding transformer: the first winding is connected in parallel to a power transmission line or a bus of an alternating current system, and the second winding is connected in parallel to an alternating current end of the second converter.
5. An improved parallel hybrid unified power flow controller as in claim 3 wherein said unified power flow controller, when in a parallel side offset configuration, comprises: the first converter, the second offset compensation equipment, the series transformer and the parallel transformer;
the series transformer is a double-winding transformer: the first winding is connected in series with a power transmission line or a bus of an alternating current system, and bypass switches are connected in parallel at two ends of the winding; the second winding is connected with the alternating current end of the first converter in parallel, and the direct current end of the first converter is connected with the direct current end of the second converter;
the parallel transformer is a three-winding transformer: the first winding is connected in parallel to a power transmission line or a bus of an alternating current system, the second winding is connected in parallel to an alternating current end of the second converter, and the first winding is connected in parallel to the second offset compensation equipment.
6. The improved parallel hybrid unified power flow controller of claim 1, wherein the first and second converters each comprise any one or at least two of a two-level converter, a three-level converter, a diode clamped converter, a flying capacitor converter, a modular multilevel converter, and an H-bridge cascaded multilevel converter;
the structures of the first current converter and the second current converter adopt any one of a single-phase structure, a three-phase structure and a three-single-phase structure.
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| CN106208009A (en) * | 2016-09-27 | 2016-12-07 | 上海北堃电力科技有限公司 | A kind of capacitor protection equipment and series compensation device |
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