CN107086573B - Plug-and-play integrated modular active series compensator - Google Patents
Plug-and-play integrated modular active series compensator Download PDFInfo
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- CN107086573B CN107086573B CN201710365031.0A CN201710365031A CN107086573B CN 107086573 B CN107086573 B CN 107086573B CN 201710365031 A CN201710365031 A CN 201710365031A CN 107086573 B CN107086573 B CN 107086573B
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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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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- 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
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase 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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
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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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/60—Planning or developing urban green infrastructure
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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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- 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
- Y02E40/40—Arrangements for reducing harmonics
-
- 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
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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Abstract
The invention discloses a plug-and-play integrated modular active series compensator, comprising: the current detection module, the inversion control module and the special mutual inductor; the current detection module is used for detecting fundamental wave current in the network access current and feedback current generated after voltage is applied to the secondary side of the special transformer through the inverter; the special transformer comprises a primary side winding and a secondary side winding, wherein the primary side winding is connected into a power grid as a busbar, and the secondary side winding is wound along the axial direction and is connected with the output end of the inversion control module; the input end of the inversion control module is connected with the direct current side voltage, the control end of the inversion control module is connected to the output end of the current detection module, and the inversion control module is used for outputting control voltage used for controlling the secondary side of the mutual inductor to generate feedback current according to a reference current signal. The invention adopts a closed current transformer type or open transformer type access mode, the access is simple and the structure of the power grid is not influenced.
Description
Technical Field
The invention belongs to the technical field of power compensators, and particularly relates to a plug-and-play integrated modular active series compensator.
Background
With the economic development, the scale of the power system in China continuously increases, and a plurality of technical problems are also encountered. In the high-voltage field, the problems of voltage boosting, capacitive reactive power surplus, over-standard grounding short-circuit current and the like exist; in the field of low-voltage power distribution, a large number of power electronic nonlinear loads are connected, and the problems of reactive power loss, voltage fluctuation, harmonic pollution and the like exist.
The adjustable reactor is a reactor capable of adjusting a reactance value in real time. The variable reactor is connected in series in the power system, so that the voltage of a power grid can be adjusted, reactive power can be compensated, the problem of three-phase imbalance is solved, short-circuit current is limited, soft starting is realized, and the problems can be effectively solved.
The existing adjustable reactors can be roughly classified into the following types:
(1) the mechanical adjustable reactor is generally divided into a turn-adjusting type and an air gap adjusting type, namely, a reactance value is equivalently changed by changing the number of turns of a coil or the length of an air gap of an iron core. The disadvantages are that: the turn-adjusting mode cannot be continuously adjusted, the automation level is low, and gear shifting needs to be stopped; the air gap adjusting type air gap has low design precision, limited adjusting range and large noise.
(2) The direct current magnetic control type controllable reactor changes the magnetic saturation of an iron core by changing the control current of a control loop, so that the inductance value of the reactor is changed, and the capacity of the reactor can be continuously adjusted. Its advantages are simple structure and control, small capacity of control part, low cost, high harmonic content and low response speed.
(3) The power switch type adjustable reactor is based on the adjustment and switching control of an inverter formed by power electronic switches, the high voltage is limited by the capacity of a tube, harmonic waves exist, and the reliability is low. Such as UPFC, UPQC, DVR, the harmonics generated by the inverter generate large harmonic losses when passing through the transformer.
(4) The alternating current magnetic control type reactor changes the magnetic flux in the reactor by generating reverse magnetic flux through the additional winding, thereby changing the magnetic resistance of the iron core and achieving the purpose of changing the inductance value of the reactor. The novel alternating current magnetic control type reactor has the outstanding advantages that the power of the reactor can be smoothly adjusted, and the higher harmonic content in the working current is low.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a plug-and-play integrated modular active series compensator, aiming at solving the problems of power grid voltage fluctuation, reactive power loss, three-phase imbalance and the like.
The invention provides a plug-and-play integrated modular active series compensator, comprising: the current detection module, the inversion control module and the special mutual inductor; the current detection module is used for detecting fundamental wave current in the network access current and feedback current generated after voltage is applied to the secondary side of the specially-made mutual inductor through the inverter; the special transformer comprises a primary side winding and a secondary side winding, wherein the primary side winding is connected into a power grid as a busbar, and the secondary side winding is wound along the axial direction and is connected with the output end of the inversion control module; the input end of the inversion control module is connected with the direct current side voltage, the control end of the inversion control module is connected to the output end of the current detection module, and the inversion control module is used for outputting control voltage used for controlling the secondary side of the mutual inductor to generate feedback current according to a reference current signal.
Still further, the current detection module includes: a fundamental current detection unit, a feedback current detection unit and an adder; the input of fundamental wave current detection unit is connected to the electric wire netting, feedback current detection unit's input is connected to the mutual-inductor secondary side, the first input of adder is connected to fundamental wave current detection unit's output, the second input of adder is connected to feedback current detection unit's output, the adder be used for with fundamental wave current with output after the feedback current adds the reference current signal.
Still further, the inverter control module includes: the device comprises an inverter, a PWM control driving unit and a filtering unit; the input end of the PWM control driving unit is connected to the output end of the adder, the input of the inverter is connected with direct-current side voltage, the control end of the inverter is connected to the output end of the PWM control driving unit, the input end of the filtering unit is connected to the output end of the inverter, and the output end of the filtering unit is connected with the secondary side of the mutual inductor; the PWM control driving unit is used for generating a PWM wave signal for controlling the conduction of a switch tube in the inverter according to the reference current signal; the inverter inverts a dc side voltage into the control voltage under control of the PWM wave signal.
Furthermore, the turn ratio k of the primary winding and the secondary winding in the special transformer is W1/W2, wherein W1 is the number of turns of the primary winding, W2 is the number of turns of the secondary winding, and W2 is larger than W1.
Furthermore, the inductance L ═ W1 of the special transformer2Mu A/l, mu is the magnetic conductivity of the iron core, A is the sectional area of the iron core, and l is the average magnetic path length.
Furthermore, the iron core of the special mutual inductor is in a shape of a slender cylinder or a cuboid.
The active series compensator provided by the invention is of a single-phase structure, is plug-and-play, and adopts an access mode of a closed current special transformer type or an open special transformer type; the method is characterized in that a rectifier of direct-current bus voltage of an inverter and the inverter are designed together initially, and the rectifier and the inverter are made into a standardized module with a specially designed current transformer, and if the impedance of a system is insufficient, a plurality of direct-current bus voltage rectifiers can be connected in series in a circuit.
The inversion control module multiplies the detected fundamental wave current on the primary side of the special transformer by a gain coefficient to be used as the instruction current of the special transformer, then the power electronic inverter generates a fundamental wave current to be applied to the secondary side of the special transformer, and the output current of the power electronic inverter is accessed into the system through a special transformer unit after passing through an LC filter circuit.
The special iron core of the special transformer is in a slender cylinder shape or a cuboid shape so as to reduce the average magnetic path length and increase the magnetic path sectional area, thereby increasing the equivalent impedance of the primary side. The conventional current transformer only plays a role of detecting current, so that the length of an iron core thereof is relatively short. The specially-made mutual inductor provided by the scheme mainly plays a compensation role, if a conventional current mutual inductor structure is adopted, the equivalent impedance of the primary side of the mutual inductor is too small to play a compensation role, so that the scheme obtains the specially-made mutual inductor by increasing the length of an iron core of the current mutual inductor, and the equivalent impedance of a power grid side meets requirements. In practical application, the actual structural size of the transformer can be specifically determined according to the reactive power quantity needing to be compensated.
When the special transformer works, the magnetic potential of the secondary side of the special transformer can be changed by adjusting alpha, so that the main flux in the iron core of the special transformer is changed, and the primary side of the special transformer can present stepless adjustable impedance.
The plug-and-play modular active series compensator has the outstanding advantages that:
(1) plug and play, adopt the access mode of closed current transformer formula or open transformer formula, insert simply and do not have the influence to electric wire netting structure itself.
(2) The structure is specially made, and the conventional current transformer mainly plays a current detection role, so that the length of an iron core of the current transformer is short. The specially-made mutual inductor provided by the scheme mainly plays a role in reactive power compensation, if a conventional current mutual inductor structure is adopted, the equivalent impedance of the primary side of the mutual inductor is too small to play a compensation role, so that the length of the iron core of the current mutual inductor is increased to obtain the specially-made mutual inductor, and the equivalent impedance of the power grid side meets the requirement.
(3) The control is improved, a current with the same frequency and the opposite phase with the current on the primary side is injected into the secondary side of the special current transformer in an active mode, and the continuous adjustment of the main magnetic flux of the special current can be realized by changing the size of the injected current on the secondary side of the special current transformer, so that the continuous adjustment of the impedance on the primary side of the special current transformer is realized.
(4) The method is characterized in that a rectifier of direct-current bus voltage of an inverter and the inverter are designed together, and the rectifier and the inverter are made into a standardized module with a specially designed current transformer.
(5) When the module is used in a three-phase system, the phase relation among different modules is transmitted through wireless communication; when a plurality of modules are used in a single-phase system, the magnitude relationship of the compensation quantities between the different modules is transmitted by wireless communication.
(6) High and low voltage are commonly used, active series compensators are commonly used in low voltage systems, but the present invention can be used in both low and high voltage systems.
Drawings
FIG. 1 is a schematic diagram of a single-phase principle circuit structure of an active series compensator connected to a power grid through a special transformer;
fig. 2(a) and (b) are schematic diagrams of a primary side and a secondary side of a closed-end columnar iron core special transformer according to the present invention, respectively; the transformer comprises a closed hollow cylindrical iron core, a closed hollow cylindrical iron core and a transformer, wherein (a) is a primary side structural schematic diagram of the closed hollow cylindrical iron core specially-made transformer, and (b) is a secondary side structural schematic diagram of the closed hollow cylindrical iron;
fig. 3(a) and (b) are schematic diagrams of a primary side and a secondary side of the open-ended cylindrical iron core tailored transformer according to the present invention, respectively; the transformer comprises a transformer body, a transformer core and a transformer core, wherein (a) is a primary side structure schematic diagram of the special transformer with the open hollow columnar iron core, and (b) is a secondary side structure schematic diagram of the;
fig. 4(a) and (b) are schematic diagrams of a primary side and a secondary side of a closed-end special transformer suitable for a busbar according to the present invention; the transformer comprises a busbar, a closed-end specially-made transformer, a transformer core and a transformer core, wherein (a) is a schematic diagram of a primary side structure of the closed-end specially-made transformer suitable for the busbar; (b) the structure of the secondary side of the closed special transformer is a schematic diagram;
fig. 5(a) and (b) are schematic diagrams of a primary side and a secondary side of an open-ended special transformer for a busbar according to the present invention; the transformer comprises a busbar, a transformer core and a transformer core, wherein (a) is a primary side structure schematic diagram of an open-ended special transformer suitable for the busbar; (b) a schematic diagram of a secondary side structure of an open-ended special transformer suitable for a busbar;
FIG. 6 is a T-shaped equivalent circuit diagram of a special mutual inductor;
wherein, 1 is the electric wire netting line, 2 is the cylinder iron core, 3 are secondary winding, 4 are female arranging, 5 are the cuboid iron core.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention is based on the principle of a magnetic flux controllable adjustable reactor, and the main magnetic flux of the transformer can be continuously adjusted by injecting a current with the same frequency and opposite phase to the primary current into the secondary side of a special transformer with an air gap on an iron core in an active mode and changing the magnitude of the injected current into the secondary side of the special transformer, thereby realizing the continuous adjustment of the primary impedance of the transformer. Compared with the existing adjustable reactor, when the transformer iron core is provided with the air gap, the adjustable reactor with the controllable magnetic flux has no saturation phenomenon, does not generate harmonic waves and can realize stepless adjustment of reactance values. However, when the adjustable reactor with controllable magnetic flux is used as an active series compensator, the primary side of the adjustable reactor needs to be connected into a power grid in series, the power grid needs to be powered off, and a power grid line needs to be disconnected, so that the original structure of the power grid is changed.
The invention provides a plug-and-play modular active series compensator, which is easy to access a power grid and does not change the original structure of the power grid.
The invention provides a single-phase active series compensator, comprising: the current detection module, the inversion control module and the special mutual inductor; the current detection module is used for detecting fundamental wave current in the network access current and feedback current generated after the fundamental wave current is applied to the secondary side of the special transformer through the inverter; the special transformer comprises a primary side winding and a secondary side winding, wherein the primary side winding is connected into a power grid as a busbar, and the secondary side winding is wound along the axial direction and is connected with the output end of the inversion control module; the input end of the inversion control module is connected with the direct current side voltage, the control end of the inversion control module is connected to the output end of the current detection module, and the inversion control module is used for outputting control voltage used for controlling the secondary side of the mutual inductor to generate feedback current according to a reference current signal.
The current detection module includes: a fundamental current detection unit, a feedback current detection unit and an adder; the input of fundamental current detecting element is connected to the electric wire netting, and feedback current detecting element's input is connected to the mutual-inductor secondary side, and the first input of adder is connected to fundamental current detecting element's output, and the second input of adder is connected to feedback current detecting element's output, and the adder is used for with fundamental current with output after the feedback current adds the reference current signal.
The inversion control module includes: the system comprises an inverter, a PWM control driving unit and an LC filtering unit; the input end of the PWM control driving unit is connected to the output end of the adder, the input of the inverter is connected with direct-current side voltage, the control end of the inverter is connected to the output end of the PWM control driving unit, the input end of the filtering unit is connected to the output end of the inverter, and the output end of the filtering unit is connected with the secondary side of the mutual inductor; the PWM control driving unit is used for generating a PWM wave signal for controlling the conduction of a switch tube in the inverter according to the reference current signal; the inverter inverts the dc side voltage into the control voltage under the control of the PWM wave signal.
The primary side of the special mutual inductor is a power line of a power grid and is connected between the power grid and a load, and the secondary side of the special mutual inductor is connected to the output end of the inversion control module.
Fundamental current detectionThe module includes: a current transformer and a fundamental current detection link. A current transformer is formed by winding a coil on the secondary side of the special transformer, the output of the current transformer is connected with the input end of the fundamental current detection link, and the fundamental current detection unit is used for detecting the primary side current of the special transformer
The detected fundamental current signal is used as a unit output signal and is sent to a current gain circuit of the inversion control module.
The inversion control module multiplies the detected fundamental wave current on the primary side of the special transformer by a gain coefficient to be used as the instruction current of the special transformer, then the power electronic inverter generates a magnetic flux compensation current to be applied to the secondary side of the special transformer, and the output current of the power electronic inverter passes through an LC filter circuit and then is accessed into a system through a special transformer unit. The LC filter circuit is used for suppressing high-frequency ripples generated by the inverter.
The specially-made transformer unit is used for connecting the control voltage output by the inverter control module into a system through fundamental compensation current generated by the transformer.
The dc bus voltage Ud can be obtained in three ways: (1) induction electricity taking is carried out on site; (2) the active power flowing into the inverter is controlled by controlling the inverter, so that the Ud is controlled; (3) the storage battery is directly connected to the direct current bus side, and the bus voltage is constant by controlling the inverter.
The working principle of the invention is that the fundamental current of the specially-made mutual inductor is detected by a fundamental current detection unit (the gain of the link is set as ku)
Will be provided with
As reference signal I of current generating circuitrefGenerating a current source by means of a power electronic inverter
(the current isThe source can use
And represents that α is a ratio coefficient of a fundamental wave of a primary side current and a secondary side current of the transformer). Will be provided with
And the system is accessed through a special mutual inductor. The magnetic potential of the secondary side of the special transformer can be changed by adjusting alpha, so that the main flux in the iron core of the special transformer is changed, and the primary side of the special transformer can present stepless adjustable impedance.
In order to further explain the plug-and-play integrated modular active series compensator provided by the present invention, the principle of the active series compensator and the tailored transformer are further explained in detail below with reference to the accompanying drawings and specific examples:
as shown in fig. 1, when the number of turns of the primary winding AX is W1 (here, 1) and the number of turns of the secondary winding AX is W2, the primary-to-secondary turn ratio k is W1/W2. If the primary side AX of the special transformer is connected in series between the grid and a load, a current i1 flows through the primary side AX. By detecting the primary side current i of a specially-made mutual inductor1And tracking the current by a voltage-type inverter to generate a current i2I is to2And injecting the opposite phase into the secondary side of the special transformer. The T-shaped equivalent circuit of the special transformer is shown in FIG. 6 (i)2Is converted into i after the primary side of the special mutual inductor2') wherein Z1＝r1+jx1Is the leakage impedance of the primary side AX coil; z'2＝r2'+jx'2Converting the secondary side of the special transformer into the leakage impedance of the primary side; zm ═ rm+jxmThe transformer is a special transformer excitation impedance.
When the special mutual inductor runs without load, an iron core is built
Of the magnetic field, main flux phi generated by the no-load magnetic fieldmNThe main magnetic fluxInduced electromotive force generated at primary side of specially-made mutual inductor
And the primary side voltage equation of the special transformer is as follows:
if the current I is injected into the secondary side of the special mutual inductor in an active mode.2The size is as follows:
wherein alpha is a real number, and alpha is more than or equal to 0 and less than or equal to 1. The total magnetic potential in the iron core of the specially-made mutual inductor is
The main magnetic flux in the iron core of the special transformer is (1-alpha) phi mN, and the induced electromotive force generated by the main magnetic flux on the primary side of the special transformer
Substituting formula (4) for formula (2) to obtain
Then looking into from the AX end, the equivalent impedance of the specially-made mutual inductor is as follows:
as can be seen from the formula (5), the impedance presented by the special transformer viewed from the AX end is a variable quantity, and the magnitude of the variable quantity and alpha satisfy a certain proportional relation. Therefore, the magnetic potential of the secondary side of the special transformer can be changed by adjusting the size of alpha, so that the main flux in the iron core of the special transformer is changed, and the primary side of the special transformer can present stepless adjustable impedance.
Because the active series compensator based on the fundamental wave magnetic flux compensation is connected in series in the line, and the access to the line is inconvenient, a specially-made mutual inductor is proposed to replace a series transformer. FIGS. 2(a) and (b) are specific structural diagrams of a closed hollow cylindrical iron core specially-produced transformer, wherein (a) is a schematic diagram of the iron core of the transformer and a power grid line, and (b) is a schematic diagram of the transformerWinding the secondary side winding on the iron core along the axial direction of the iron core; fig. 3(a) and (b) are specific structural diagrams of a special transformer with an open hollow cylindrical iron core, wherein (a) is a schematic diagram of the iron core of the transformer and a power grid line, and (b) is a diagram of a winding diagram of a secondary side winding of the transformer on the iron core, and the winding is carried out along the axial direction of the iron core; fig. 4(a) and (b) are specific structural diagrams of a closed-end special transformer suitable for a busbar, wherein (a) is a schematic diagram of an iron core and the busbar of the transformer, and (b) is a diagram of a winding diagram of a secondary side winding of the transformer on a cuboid iron core, and the winding is carried out along the axial direction of the iron core; fig. 5(a) and (b) are specific structural diagrams of the open-ended special transformer suitable for the busbar, wherein (a) is a schematic diagram of an iron core and the busbar of the transformer, and (b) is a diagram of a winding diagram of a secondary side winding of the transformer on a cuboid iron core, and the winding is carried out along the axial direction of the iron core. The open type purpose-built mutual inductor can be connected to a power grid in a current clamp mode, and in consideration of the fact that current clamps are well known to those skilled in the art, detailed descriptions of specific structures in the current clamp mode in the schematic diagrams 3(a) and (b), 5(a) and (b) are omitted here. The primary side of the special mutual inductor only has one turn of system line, and the inductor
(wherein W1 is the primary side turn number of the purpose-made mutual inductor, mu is the magnetic conductivity of the iron core, A is the iron core sectional area, L is the average magnetic path length) if the ordinary iron core is used, the equivalent inductance of the power grid side is too small, so the iron core of the purpose-made mutual inductor shown in figures 2-5 is made into a slender cylinder or a cuboid shape to reduce the magnetic path length and increase the iron core sectional area, thereby increasing the inductance L. If the inductance value still does not meet the requirement, a plurality of plug-and-play compensators can be connected into the power grid in series.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (5)
1. A plug and play integrated modular active series compensator comprising: the current detection module, the inversion control module and the special mutual inductor;
the current detection module is used for detecting fundamental wave current in the network access current and feedback current generated after voltage is applied to the secondary side of the specially-made mutual inductor through the inverter;
the special transformer comprises a primary side winding and a secondary side winding, wherein the primary side winding is connected into a power grid as a busbar, and the secondary side winding is wound along the axial direction and is connected with the output end of the inversion control module;
the input end of the inversion control module is connected with direct current side voltage, the control end of the inversion control module is connected to the output end of the current detection module, and the inversion control module is used for outputting control voltage for controlling the secondary side of the specially-made mutual inductor to generate feedback current according to a reference current signal;
the current detection module includes: a fundamental current detection unit, a feedback current detection unit and an adder;
the input end of the fundamental current detection unit is connected to a power grid, the input end of the feedback current detection unit is connected to the secondary side of the transformer, the first input end of the adder is connected to the output end of the fundamental current detection unit, the second input end of the adder is connected to the output end of the feedback current detection unit, and the adder is used for adding the fundamental current and the feedback current and then outputting the reference current signal;
the plug-and-play integrated modular active series compensator detects the fundamental current of a special mutual inductor through a fundamental current detection unit
Will be provided with
As reference signal I of current generating circuitrefGenerating a current source by means of a power electronic inverter
For current sources
The method comprises the following steps that alpha is a ratio coefficient of a fundamental wave of primary side current and secondary side current of a transformer; will be provided with
Connecting the special transformer into a system, and changing the magnetic potential of the secondary side of the special transformer by adjusting alpha;
t-shaped equivalent circuit of specially-made mutual inductor i2Is converted into i after the primary side of the special mutual inductor2', wherein Z1＝r1+jx1Is the leakage impedance of the primary side AX coil; z'2＝r2'+jx'2Converting the secondary side of the special transformer into the leakage impedance of the primary side; zm ═ rm+jxmThe transformer is a special transformer excitation impedance.
2. The compensator of claim 1, wherein the inverter control module comprises: the device comprises an inverter, a PWM control driving unit and a filtering unit;
the input end of the PWM control driving unit is connected to the output end of the adder, the input end of the inverter is connected with direct-current side voltage, the control end of the inverter is connected to the output end of the PWM control driving unit, the input end of the filtering unit is connected to the output end of the inverter, and the output end of the filtering unit is connected with the secondary side of the special mutual inductor; the PWM control driving unit is used for generating a PWM wave signal for controlling the conduction of a switch tube in the inverter according to the reference current signal; the inverter inverts a dc side voltage into the control voltage under control of the PWM wave signal.
3. The compensator of any one of claims 1-2, wherein the turn ratio k of the primary winding and the secondary winding in the tailored transformer is W1/W2, wherein W1 is the number of turns of the primary winding, W2 is the number of turns of the secondary winding, and W2 is greater than W1.
4. The compensator of claim 3, wherein the inductance L-W1 of the purpose built transformer2μ A/l, μ is the magnetic permeability of the core, A is the core cross-sectional area, l is the average magnetic path length, and W1 is the number of turns of the primary winding.
5. A compensator as claimed in claim 3, wherein the iron core of the tailored transformer is elongate cylindrical or cuboid.
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| CN103036236A (en) * | 2012-12-04 | 2013-04-10 | 湖南大学 | Control method of wide frequency range multi-type harmonic comprehensive governance system |
| CN104993484A (en) * | 2015-04-27 | 2015-10-21 | 深圳市今朝时代新能源技术有限公司 | Active electrical filter |
| CN206850430U (en) * | 2017-05-22 | 2018-01-05 | 华中科技大学 | A kind of plug and play integrated modular cascade active compensator |
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| CN103036236A (en) * | 2012-12-04 | 2013-04-10 | 湖南大学 | Control method of wide frequency range multi-type harmonic comprehensive governance system |
| CN104993484A (en) * | 2015-04-27 | 2015-10-21 | 深圳市今朝时代新能源技术有限公司 | Active electrical filter |
| CN206850430U (en) * | 2017-05-22 | 2018-01-05 | 华中科技大学 | A kind of plug and play integrated modular cascade active compensator |
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