CN105846459B - The adaptive distance protection method combined based on intrinsic frequency with characteristic frequency - Google Patents
The adaptive distance protection method combined based on intrinsic frequency with characteristic frequency Download PDFInfo
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- H02J3/386—
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
- H02H7/262—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of switching or blocking orders
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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
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/76—Power conversion electric or electronic aspects
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Abstract
The invention discloses a kind of adaptive distance protection methods combined based on intrinsic frequency with characteristic frequency, according to the rotating speed of wind energy conversion system before failure, when intrinsic frequency and characteristic frequency are applied to failure in the analysis of fault signature, voltage and current not only explicit physical meaning is expressed after failure using intrinsic frequency and characteristic frequency, and closer to practical implementation, the adaptive distance protection that intrinsic frequency proposed by the present invention is combined with characteristic frequency, Reliability of Microprocessor of the wind-electricity integration relay protection under various operating modes can be improved, to improving the correct action of wind-electricity integration relay protection, with higher use value.
Description
Technical Field
The invention relates to a self-adaptive distance protection method based on combination of natural frequency and characteristic frequency, and belongs to the technical field of power system automation.
Background
In recent years, the proportion of wind power generation in the total power generation portion is more and more important, and wind power generation has become a trend as a typical new energy power generation form, but the relay protection problem of wind power integration becomes a difficult problem due to the characteristics of a fan, and related cases caused by misoperation of the relay protection problem have occurred in China. The problem that needs to be solved at present is that the distance protection of the sending-out line is influenced by wind power access, the distance protection of the sending-out line wind power plant side needs wind power plant side voltage and current information, wherein the frequency of the wind power plant fault current changes along with the rotating speed of the generator set before short circuit, the frequency change range is generally 35 to 65Hz, the power frequency is not maintained any longer, the fundamental wave phasor cannot be accurately extracted by a protection algorithm (such as a Fourier algorithm) based on the power frequency phasor, and the impedance measured according to the power frequency voltage and the current ratio is not accurate any longer.
Disclosure of Invention
The invention aims to solve the problem that the wind power grid-connected outgoing line is not applicable based on the traditional power frequency distance protection. According to the self-adaptive distance protection method based on the combination of the natural frequency and the characteristic frequency, the natural frequency and the characteristic frequency are applied to the analysis of fault characteristics during fault, the reliability of the action of the wind power grid-connected relay protection under various working conditions can be improved, the correct action of the wind power grid-connected relay protection is improved, and the self-adaptive distance protection method has high use value.
In order to achieve the purpose, the invention adopts the technical scheme that:
a self-adaptive distance protection method based on combination of natural frequency and characteristic frequency is characterized in that: comprises the following steps of (a) carrying out,
determining fixed frequency and characteristic frequency after a wind power plant outgoing line fault;
(A1) after a wind power plant line is sent out, a fan is put into Crowbar circuit protection to realize fault ride-through, at the moment, the double-fed fan is equivalent to an asynchronous generator, the rotor current is attenuated direct current, the terminal voltage of the double-fed fan consists of alternating current electromotive force and power frequency electromotive force of rotating speed frequency before fault, and the wind power plant side fault current IsAs shown in the formula (1),
wherein,the initial phase angle is the initial phase angle when the Crowbar circuit is put into operation; a is1、a2、a3The value of the coefficient is a conventional coefficient and depends on the doubly-fed wind turbine parameter and the voltage drop level; omega1For angular frequency of the grid；ωrIs the rotor speed angular frequency;τ'sis the stator loop time constant, τ'rIs the rotor loop time constant;
(A2) obtaining the fault current I on the wind power plant side according to the formula (1)sThe frequency of the attenuation alternating current component depends on the rotating speed of the double-fed fan before the fault, so that the frequency of the double-fed fan before the fault is obtained as a characteristic frequency, and the 50Hz frequency of a power grid is a natural frequency;
step (B), according to the determined fixed frequency and characteristic frequency, carrying out self-adaptive distance protection of wind power integration;
(B1) after the failure of the wind power plant sending-out line is set, the voltage and the current of the bus protection installation position on the side of the wind turbine are shown as formulas (2) and (3),
wherein, ω and ω' are a natural angular frequency and a characteristic angular frequency respectively; f. f' is the natural frequency and the characteristic frequency respectively; phi is au、φ′uThe voltage initial phase angles corresponding to the natural frequency and the characteristic frequency components respectively; phi is ai、φ′iCurrent initial phase angles corresponding to the natural frequency and the characteristic frequency components respectively; A. c is the voltage and current amplitude corresponding to the natural frequency respectively; B. d is the voltage and current amplitude corresponding to the characteristic frequency, and the magnitude of the voltage and current amplitude is related to the motor parameter and the voltage drop level; n is the rotating speed of the double-fed fan before the fault, nNThe rated rotating speed of the double-fed fan is set;
(B2) the hybrid impedance Z is defined according to the rotation speed of the doubly-fed wind turbine before the fault, as shown by company (4),
wherein,respectively are voltage phasor and current phasor corresponding to the natural frequency and the characteristic frequency; k is a radical of1、k2Is a mixing factor, andthe i and i' are current amplitudes corresponding to the natural frequency and the characteristic frequency respectively;
(B3) from (B2), the hybrid impedance measured at the wind farm transmission line protection installation, as shown in equation (5),
(B4) obtaining an impedance setting value Z according to a formula (6)set，
Wherein l is the line protection length; r is1、L1、x1The resistance value, the inductance value and the reactance value of the line unit length are respectively;
(B5) if Z is less than ZsetAnd the wind power grid-connected relay protection outlet acts.
The foregoing adaptive distance protection method based on combination of natural frequency and characteristic frequency is characterized in that: (A2) and obtaining the frequency of the double-fed fan at the rotating speed before the fault as the characteristic frequency, and extracting the characteristic frequency of the voltage and the current after the fault by adopting a prony algorithm after the fault.
The invention has the beneficial effects that: according to the self-adaptive distance protection method based on the combination of the natural frequency and the characteristic frequency, the natural frequency and the characteristic frequency are applied to the analysis of fault characteristics during the fault according to the rotating speed of a wind turbine before the fault, the natural frequency and the characteristic frequency are utilized to express the voltage and the current after the fault, the physical significance is clear, and the self-adaptive distance protection method is closer to the practical engineering application.
Drawings
Fig. 1 is a grid-connected wiring diagram of the doubly-fed wind turbine of the invention.
Fig. 2 is a grid-connected wiring diagram of a doubly-fed wind turbine with impedance elements installed at a wind farm outgoing line protection installation.
Fig. 3 is a schematic diagram of the impedance characteristic of the adaptive frequency varying impedance protection device of the present invention.
Detailed Description
The invention will be further explained with reference to the drawings attached to the specification. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The invention relates to an adaptive distance protection method based on combination of natural frequency and characteristic frequency, which comprises the following steps,
determining fixed frequency and characteristic frequency after a wind power plant outgoing line fault;
(A1) as shown in figure 1, the grid-connected wiring diagram of the doubly-fed wind turbine is shown when a 110kV lineWhen a three-phase fault occurs on a path, a double-fed fan is put into a Crowbar circuit to protect a rotor side converter, the double-fed fan is equivalent to a common asynchronous generator at the moment, so that the Crowbar circuit is obtained, the double-fed fan in a wind power plant after the Crowbar circuit protection is put into is equivalent to the asynchronous generator, the rotor current is attenuated direct current, the terminal voltage of the double-fed fan is composed of alternating current electromotive force and power frequency electromotive force of rotational speed frequency before the fault, and the side fault current I of the wind power plantsAs shown in the formula (1),
wherein,the initial phase angle is the initial phase angle when the Crowbar circuit is put into operation; a is1、a2、a3The value of the coefficient is a conventional coefficient and depends on the doubly-fed wind turbine parameter and the voltage drop level; omega1Is the grid angular frequency; omegarIs the rotor speed angular frequency;τ′sis the stator loop time constant, τ'rIs the rotor loop time constant;
(A2) obtaining the fault current I on the wind power plant side according to the formula (1)sThe method comprises a steady-state alternating current component, an attenuation direct current component and an attenuation alternating current component, wherein the frequency of the attenuation alternating current component depends on the rotating speed of the double-fed fan before the fault, so that the frequency of the double-fed fan before the fault is obtained as a characteristic frequency, the 50Hz frequency of a power grid is a natural frequency, the characteristic frequency is used for extracting the characteristic frequency of voltage and current after the fault by adopting a Prony algorithm, the Prony algorithm is a method for fitting a group of linear combinations of exponential terms to equidistant sampling data, the information such as amplitude, phase, damping factor, frequency and the like of a signal can be analyzed, the composition of the fault current after the fault comprises the steady-state alternating current corresponding fixed frequency and the attenuation alternating current corresponding characteristic frequency according to a formula (1),extracting corresponding frequency components by adopting a prony algorithm;
step (B), according to the determined fixed frequency and characteristic frequency, carrying out self-adaptive distance protection of wind power integration;
(B1) after the failure of the wind power plant sending-out line is set, the voltage and the current of the bus protection installation position on the side of the wind turbine are shown as formulas (2) and (3),
wherein, ω and ω' are a natural angular frequency and a characteristic angular frequency respectively; f. f' is the natural frequency and the characteristic frequency respectively; phi is au、φ′uThe voltage initial phase angles corresponding to the natural frequency and the characteristic frequency components respectively; phi is ai、φ′iCurrent initial phase angles corresponding to the natural frequency and the characteristic frequency components respectively; A. c is the voltage and current amplitude corresponding to the natural frequency respectively; B. d is the voltage and current amplitude corresponding to the characteristic frequency, and the magnitude of the voltage and current amplitude is related to the motor parameter and the voltage drop level; n is the rotating speed of the double-fed fan before the fault, nNThe rated rotating speed of the double-fed fan is set;
(B2) and defining the mixed impedance Z according to the rotating speed of the double-fed fan before the fault, as shown in a formula (4),
wherein,respectively are voltage phasor and current phasor corresponding to the natural frequency and the characteristic frequency; k is a radical of1、k2Is a mixing factor, andthe i and i' are current amplitudes corresponding to the natural frequency and the characteristic frequency respectively;
(B3) from (B2), the hybrid impedance measured at the wind farm transmission line protection installation, as shown in equation (5),
(B4) obtaining an impedance setting value Z according to a formula (6)set，
Wherein l is the line protection length; r is1、L1、x1The resistance value, the inductance value and the reactance value of the line unit length are respectively;
(B5) if Z is less than ZsetAnd the wind power grid-connected relay protection outlet acts.
As shown in fig. 2, in a specific application example of the self-adaptive distance protection method based on the combination of the natural frequency and the characteristic frequency, after a fault occurs, the measured impedance at the protection installation position of the wind farm outgoing line is as follows: ,
when Z is less than ZsetThe impedance element operates.
Wherein Z issetThe impedance protection is fixed, and the value is adaptively adjusted according to the frequency change:
Zset＝krel*lZ1
＝krel*l(r1+jx1)
＝krel*l[r1+j(k1ωL1+k2ω1L1)]
wherein l is the line protection length; r is1、L1、x1The values of the resistance, the inductance and the reactance of the circuit unit length are respectively.
Fig. 3 is a schematic diagram of impedance characteristics of an impedance protection element with adaptive frequency change, curves 1, 2, and 3 are circular impedance characteristics when a characteristic frequency, a natural frequency, and a mixed frequency are adopted, respectively, the impedance characteristics of a normally operating system are 2 curves, when a frequency after a fault only includes the characteristic frequency, the impedance circular characteristics are changed into 1 curve, and when the frequency after the fault includes both the natural frequency and the characteristic frequency, the impedance circle is changed into 3 curves, in which process, a setting value of a resistor is always unchanged, so that the center of a circle of the impedance circle always moves on a straight line AB.
In summary, the self-adaptive distance protection method based on the combination of the natural frequency and the characteristic frequency applies the natural frequency and the characteristic frequency to the analysis of fault characteristics during the fault according to the rotating speed of a wind turbine before the fault, utilizes the natural frequency and the characteristic frequency to express the voltage and the current after the fault, has clear physical significance and is closer to the practical engineering application.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (2)
1. The self-adaptive distance protection method based on the combination of the natural frequency and the characteristic frequency is characterized in that: comprises the following steps of (a) carrying out,
determining fixed frequency and characteristic frequency after a wind power plant outgoing line fault;
(A1) after the wind power plant sends out a line fault, the fan can be put into Crowbar circuit protection to realize fault ride-through, at the moment, the double-fed fan is equivalent to an asynchronous generator, the rotor current is attenuated direct current, the terminal voltage of the double-fed fan consists of alternating current electromotive force and power frequency electromotive force of the rotating speed frequency before the fault, and the fault current at the wind power plant sideIsAs shown in the formula (1),
wherein,the initial phase angle is the initial phase angle when the Crowbar circuit is put into operation; a is1、a2、a3The value of the coefficient is a conventional coefficient and depends on the doubly-fed wind turbine parameter and the voltage drop level; omega1Is the grid angular frequency; omegarIs the rotor speed angular frequency;τ＇sis the stator loop time constant, τ'rIs the rotor loop time constant;
(A2) obtaining the fault current I on the wind power plant side according to the formula (1)sThe frequency of the attenuation alternating current component depends on the rotating speed of the double-fed fan before the fault, so that the frequency of the double-fed fan before the fault is obtained as a characteristic frequency, and the 50Hz frequency of a power grid is a natural frequency;
step (B), according to the determined fixed frequency and characteristic frequency, carrying out self-adaptive distance protection of wind power integration;
(B1) after the failure of the wind power plant sending-out line is set, the voltage and the current of the bus protection installation position on the side of the wind turbine are shown as formulas (2) and (3),
wherein, ω and ω' are a natural angular frequency and a characteristic angular frequency respectively; f. f' is the natural frequency and the characteristic frequency respectively; phi is au、φu' are respectively fixedThere is a voltage initial phase angle corresponding to the frequency and the characteristic frequency component; phi is ai、φi' are the initial current phase angles corresponding to the natural frequency and the characteristic frequency components respectively; A. c is the voltage and current amplitude corresponding to the natural frequency respectively; B. d is the voltage and current amplitude corresponding to the characteristic frequency, and the magnitude of the voltage and current amplitude is related to the motor parameter and the voltage drop level; n is the rotating speed of the double-fed fan before the fault, nNThe rated rotating speed of the double-fed fan is set;
(B2) and defining the mixed impedance Z according to the rotating speed of the double-fed fan before the fault, as shown in a formula (4),
wherein,respectively are voltage phasor and current phasor corresponding to the natural frequency and the characteristic frequency; k is a radical of1、k2Is a mixing factor, andthe i and i' are current amplitudes corresponding to the natural frequency and the characteristic frequency respectively;
(B3) from (B2), the hybrid impedance measured at the wind farm transmission line protection installation, as shown in equation (5),
(B4) obtaining an impedance setting value Z according to a formula (6)set，
Wherein l is the line protection length; r is1、L1、x1The resistance value, the inductance value and the reactance value of the line unit length are respectively;
(B5) if Z is less than ZsetAnd the wind power grid-connected relay protection outlet acts.
2. The adaptive distance protection method based on the combination of the natural frequency and the characteristic frequency according to claim 1, wherein: (A3) and obtaining the frequency of the double-fed fan at the rotating speed before the fault as the characteristic frequency, and extracting the characteristic frequency of the voltage and the current after the fault by adopting a prony algorithm after the fault.
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