CN105024364A - Analysis method for influence on distance protection caused by access of large-scale wind power equipment to AC/DC hybrid system - Google Patents

Abstract

The invention discloses an analysis method for influence on distance protection caused by access of large-scale wind power equipment to an AC/DC hybrid system. The method mainly includes defining measurement impedance; analyzing distance protection principle based on power frequency phasor aiming at different fault types; analyzing criteria forpower frequency variation distance protection; and analyzing influence on power frequency variation distance caused by system impedance. According to the invention, by using the analysis method, shortcomings of high distance protection operation incorrectness and poor power supply reliability and the like are overcome and an advantage of enhancement of power supply reliability and power grid safety when the large-scale wind power equipment accesses to the AC/DC hybrid system is realized.

Description

Scale wind power integration alternating current-direct current combined hybrid system is adjusted the distance and is protected the analytical method of impact

Technical field

The present invention relates to technical field of wind power, particularly, relate to scale wind power integration alternating current-direct current combined hybrid system adjust the distance protection impact analytical method.

Background technology

The large-scale wind electricity base majority that China's wind-powered electricity generation produces after entering the large-scale development stage is positioned at " three northern areas of China " (northwest, northeast, North China); large-scale wind electricity base is generally away from load center, and its electric power needs to be transported to load center to dissolve through long-distance, high voltage.Due to the intermittence of wind-resources, randomness and fluctuation, cause the fluctuation that the wind power output of large wind power base can occur in a big way thereupon, cause the fluctuation of electric power transmission network charge power further, bring series of problems to safe operation of electric network.

By in November, 2013, the installed capacity of Gansu Power Grid grid connected wind power has reached 6,680,000 kilowatts, accounts for 21% of Gansu Power Grid total installation of generating capacity, becomes the second largest main force power supply being only second to thermoelectricity.Along with the improving constantly of wind-electricity integration scale, operation that 750kV ultrahigh-voltage alternating-current sends circuit outside and Jiuquan-Zhuzhou ± 800kV extra-high voltage direct-current send the reply of circuit outside, the new forms of energy development model that Jiuquan ten million multikilowatt wind power base extensive, highly to be concentrated starting, remote, ultrahigh-voltage alternating-current combines conveying with extra-high voltage direct-current.Due to the fluctuation of large wind-powered electricity generation, introduce a large amount of power electronic device in wind power system, when making fault, transient process is more complicated, and this fault signature that relaying protection system is faced there occurs marked change.Hexi Corridor 750kV electrical network is as wind-powered electricity generation Transmission Corridor; except power supply has fluctuation feature; due to ± 800kV extra-high voltage direct-current transmission technology will be adopted; it also has the feature of AC-DC hybrid power grid; the power electronic equipment that extra-high voltage direct-current transmission is introduced makes power network electricity transmission line fault transient process more complicated; duration is longer, and harmonic content is enriched, and relaying protection will be brought to the impact of can not ignore.Therefore need to carry out in-depth analysis research to the AC-DC hybrid power grid relaying protection problem of large wind power integration, especially need the relaying configuration scheme of the transmission line studying each electric pressure, ensure power network safety operation.

The defects such as realizing in process of the present invention, it is high that inventor finds at least there is distance protection incorrect operation rate in prior art, power supply reliability difference.

Summary of the invention

The object of the invention is to, for the problems referred to above, proposition scale wind power integration alternating current-direct current combined hybrid system is adjusted the distance and is protected the analytical method of impact, to realize the advantage improving power supply reliability and electric network security.

For achieving the above object, the technical solution used in the present invention is: scale wind power integration alternating current-direct current combined hybrid system is adjusted the distance and protected the analytical method of impact, mainly comprises:

A, for different faults type, the principle of distance relay based on power frequency phasor to be analyzed;

B, to based on power frequency variation distance protection criterion analyze;

C, the impact of system impedance on power frequency variation distance to be analyzed.

Further, described step a, specifically comprises:

(1) single phase ground fault, for A phase single-phase grounding fault:

Under A phase ground fault condition, have:

In formula (3), represent the A phase voltage at k place, fault point; represent voltage, the electric current of protection installation place A phase; z ₁represent the positive sequence impedance of protected circuit unit length; represent zero-sequence current; L _krepresent the measuring distance of protection installation place to fault point; K represents zero sequence current compensation factor,

When metallic earthing fault, have:

There is transition resistance R _fduring earth fault, have:

Further, described step a, specifically also comprises:

(2) two-phase phase to phase fault, for AB two-phase short-circuit fault:

When breaking down, have:

When metallicity fault, two formulas are subtracted each other above, have:

There is transition resistance R _ftime, have:

In formula (7), it is protection installation place, circuit A, B opposite end electric current.

Further, described step a, specifically also comprises:

Double earthfault, for AB two-phase short circuit and ground fault:

When breaking down, have:

When breaking down, two formulas are subtracted each other above, have:

Further, described step b, specifically comprises:

Its operating criterion is set up, when operating criterion is in critical condition when protection zone end fault according to the voltage boundary condition of fault point; The fault component voltage of protection zone end is:

For phase distance protection,

For ground distance protection, φ=A, B or C, k=(Z ₀-Z ₁)/Z ₁;

The operating criterion of Comparison of Sudden Changing Rate of Power Frequency Components distance protection is:

In formula (10), be fault front protection zone terminal voltage value, play amplitude reference effect.

Further, described step b, specifically comprises:

The operation equation of power frequency variation distance is expressed as:

Consider system impedance, above formula be deformed into:

that is:

From formula (12), the essence of power frequency variation distance protection is a kind of power frequency variation current protection;

Find out that its impact being subject to system operation mode and system impedance is comparatively large by its operation equation, below provide labor:

According to setting principle, generally establish safety factor k _rel=1.2, then, when transmission line dorsal part is Infinite bus system, its operation equation is electric current when namely protecting the Sudden Changing Rate electric current of installation place to be greater than 1.2 times of protection end faults could action, and the scope that is protected comparatively power frequency amount distance protection reduces 20%;

If consider according to the strategy of " inverse time lag " open and protection scope, reliable system will be taken as 2.0 or larger, and when fault transient, power frequency variation electric current is greater than 2 times of electric currents when protecting end fault, and protection range is less;

When considering system impedance, situation will become even more serious; Adopt and analyze identical method above, when system impedance is identical with the impedance of adjusting of protection, only having the fault component electric current when protection installation place to meet: time, the action of protection ability, namely now only have fault component electric current to be greater than the setting current protection ability action of 2.4 times, if system impedance strengthens further, protection range will reduce further.

The scale wind power integration alternating current-direct current combined hybrid system of various embodiments of the present invention is adjusted the distance and is protected the analytical method of impact, owing to mainly comprising: define measurement impedance; For different faults type, the principle of distance relay based on power frequency phasor is analyzed; Criterion based on the protection of power frequency variation distance is analyzed; The impact of system impedance on power frequency variation distance is analyzed; Thus it is high to overcome prior art middle distance protection incorrect operation rate, the defect of power supply reliability difference, to realize the advantage improving power supply reliability and electric network security.

Other features and advantages of the present invention will be set forth in the following description, and, partly become apparent from specification, or understand by implementing the present invention.

Below by drawings and Examples, technical scheme of the present invention is described in further detail.

Accompanying drawing explanation

Accompanying drawing is used to provide a further understanding of the present invention, and forms a part for specification, together with embodiments of the present invention for explaining the present invention, is not construed as limiting the invention.In the accompanying drawings:

Fig. 1 is that scale wind power integration alternating current-direct current combined hybrid system of the present invention is adjusted the distance the schematic flow sheet of analytical method of protection impact.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described, should be appreciated that preferred embodiment described herein is only for instruction and explanation of the present invention, is not intended to limit the present invention.

According to the embodiment of the present invention; as shown in Figure 1; provide scale wind power integration alternating current-direct current combined hybrid system adjust the distance protection impact analytical method; belong to the AC-DC hybrid power grid transmission line Simulation and Modeling Technology field in large-scale wind power access situation, be specifically related to a kind of large-scale wind power access alternating current-direct current combined hybrid system and adjust the distance the simulating, verifying analytical method of protection impact.

The scale wind power integration alternating current-direct current combined hybrid system of the present embodiment is adjusted the distance and is protected the analytical method of impact, specifically comprises following content:

1) measurement impedance is defined

In distance protection, measurement impedance uses Z usually _mrepresent, it is defined as protection installation place measuring voltage with measurement electric current ratio, that is:

In formula (1), Z _mbe a plural number, namely

In formula (2), | Z _m| represent the resistance value of measurement impedance; represent the impedance angle of measurement impedance; R _mrepresent the real part of measurement impedance, be called measuring resistance; X _mrepresent the imaginary part of measurement impedance, be called measurement reactance.

According to measurement impedance Z _mthe difference of amplitude and phase place under the different operation conditions of electric power system, protective device just can distinguish whether system there occurs fault, fault to occur in district still outside district.

2) for different faults type, the principle of distance relay based on power frequency phasor is analyzed

(1) single phase ground fault

For A phase single-phase grounding fault.

Under A phase ground fault condition, have:

In formula (3), represent the A phase voltage at k place, fault point; represent voltage, the electric current of protection installation place A phase; z ₁represent the positive sequence impedance of protected circuit unit length; represent zero-sequence current; L _krepresent the measuring distance of protection installation place to fault point; K represents zero sequence current compensation factor,

When metallic earthing fault, have:

There is transition resistance R _fduring earth fault, have:

(2) two-phase phase to phase fault

For AB two-phase short-circuit fault.When breaking down, have:

When metallicity fault, two formulas are subtracted each other above, have:

There is transition resistance R _ftime, have:

In formula (7), it is protection installation place, circuit A, B opposite end electric current.

(3) double earthfault

For AB two-phase short circuit and ground fault.When breaking down, have:

When breaking down, two formulas are subtracted each other above, have:

3) criterion based on the protection of power frequency variation distance is analyzed

Its operating criterion is set up, when operating criterion is in critical condition when protection zone end fault according to the voltage boundary condition of fault point.The fault component voltage of protection zone end is:

For phase distance protection, ( );

For ground distance protection, [φ=A, B or C, k=(Z ₀-Z ₁)/Z ₁].

The operating criterion of Comparison of Sudden Changing Rate of Power Frequency Components distance protection is:

In formula (10), be fault front protection zone terminal voltage value, play amplitude reference effect.

4) impact of system impedance on power frequency variation distance is analyzed

The operation equation of power frequency variation distance can be expressed as:

Consider system impedance, above formula be deformed into:

that is:

From formula (12), the essence of power frequency variation distance protection is a kind of power frequency variation current protection.Can find out that its impact being subject to system operation mode (system impedance) is comparatively large by its operation equation, below provide labor.

According to setting principle, generally establish safety factor k _rel=1.2, then, when transmission line dorsal part is Infinite bus system, its operation equation is electric current when namely protecting the Sudden Changing Rate electric current of installation place to be greater than 1.2 times of protection end faults could action, and the scope that is protected comparatively power frequency amount distance protection reduces 20%.If consider according to the strategy of " inverse time lag " open and protection scope, reliable system will be taken as 2.0 or larger, and when fault transient, power frequency variation electric current is greater than 2 times of electric currents when protecting end fault, and protection range is less.

When considering system impedance, situation will become even more serious.Adopt and analyze identical method above, when system impedance is identical with the impedance of adjusting of protection, only having the fault component electric current when protection installation place to meet time, the action of protection ability, namely now only have fault component electric current to be greater than the setting current protection ability action of 2.4 times, if system impedance strengthens further, protection range will reduce further.

Therefore for the situation that system impedance is larger, may there is the situation not having protection range and tripping in the protection of power frequency variation distance.

Last it is noted that the foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, although with reference to previous embodiment to invention has been detailed description, for a person skilled in the art, it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein portion of techniques feature.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (6)

1. scale wind power integration alternating current-direct current combined hybrid system is adjusted the distance and is protected the analytical method of impact, it is characterized in that, mainly comprises:

A, for different faults type, the principle of distance relay based on power frequency phasor to be analyzed;

B, to based on power frequency variation distance protection criterion analyze;

C, on system impedance on power frequency variation distance protection impact analyze.

2. scale wind power integration alternating current-direct current combined hybrid system according to claim 1 is adjusted the distance and is protected the analytical method of impact, and it is characterized in that, described step a, specifically comprises:

(1) single phase ground fault, for A phase single-phase grounding fault:

Under A phase ground fault condition, have:

${\stackrel{\·}{U}}_A={\stackrel{\·}{U}}_{kA}+({\stackrel{\·}{I}}_A+K\×3{\stackrel{\·}{I}}_0)z_1{L}_k---\left(3\right);$

In formula (3), represent the A phase voltage at k place, fault point; represent voltage, the electric current of protection installation place A phase; z ₁represent the positive sequence impedance of protected circuit unit length; represent zero-sequence current; L _krepresent the measuring distance of protection installation place to fault point; K represents zero sequence current compensation factor,

When metallic earthing fault, have:

${\stackrel{\·}{U}}_A=({\stackrel{\·}{I}}_A+K\×3{\stackrel{\·}{I}}_0)z_1{L}_k---\left(4\right);$

There is transition resistance R _fduring earth fault, have:

${\stackrel{\·}{U}}_A=({\stackrel{\·}{I}}_A+K\×3{\stackrel{\·}{I}}_0)z_1{L}_k+3{\stackrel{\·}{I}}_0{R}_f---\left(5\right).$

3. scale wind power integration alternating current-direct current combined hybrid system according to claim 1 is adjusted the distance and is protected the analytical method of impact, and it is characterized in that, described step b, specifically also comprises:

(2) two-phase phase to phase fault, for AB two-phase short-circuit fault:

When breaking down, have:

${\stackrel{\·}{U}}_A={\stackrel{\·}{U}}_{kA}+({\stackrel{\·}{I}}_A+K\×3{\stackrel{\·}{I}}_0)z_1{L}_k;$

${\stackrel{\·}{U}}_B={\stackrel{\·}{U}}_{kB}+({\stackrel{\·}{I}}_B+K\×3{\stackrel{\·}{I}}_0)z_1{L}_k;$

When metallicity fault, two formulas are subtracted each other above, have:

${\stackrel{\·}{U}}_A-{\stackrel{\·}{U}}_B=({\stackrel{\·}{I}}_A+{\stackrel{\·}{I}}_B)\×z_1{L}_k---\left(6\right);$

There is transition resistance R _ftime, have:

${\stackrel{\·}{U}}_A-{\stackrel{\·}{U}}_B=({\stackrel{\·}{I}}_A-{\stackrel{\·}{I}}_B)\×z_1{L}_k+({\stackrel{\·}{U}}_{kA}-{\stackrel{\·}{U}}_{kB})=({\stackrel{\·}{I}}_A-{\stackrel{\·}{I}}_B)\×z_1{L}_k+R_f\×{\stackrel{\·}{I}}_f---\left(7\right);$

In formula (7), ${\stackrel{\·}{I}}_f={\stackrel{\·}{I}}_A+{\stackrel{\·}{I}}_{nA}-{\stackrel{\·}{I}}_B-{\stackrel{\·}{I}}_{nB},$ it is protection installation place, circuit A, B opposite end electric current.

4. scale wind power integration alternating current-direct current combined hybrid system according to claim 1 is adjusted the distance and is protected the analytical method of impact, and it is characterized in that, described step a, specifically also comprises:

Double earthfault, for AB two-phase short circuit and ground fault:

When breaking down, have:

${\stackrel{\·}{U}}_A={\stackrel{\·}{U}}_{kA}+({\stackrel{\·}{I}}_A+K\×3{\stackrel{\·}{I}}_0)z_1{L}_k;$

${\stackrel{\·}{U}}_B={\stackrel{\·}{U}}_{kB}+({\stackrel{\·}{I}}_B+K\×3{\stackrel{\·}{I}}_0)z_1{L}_k;$

When breaking down, two formulas are subtracted each other above, have:

${\stackrel{\·}{U}}_A-{\stackrel{\·}{U}}_B=({\stackrel{\·}{I}}_A+{\stackrel{\·}{I}}_B)\×z_1{L}_k---\left(8\right).$

5. the scale wind power integration alternating current-direct current combined hybrid system according to any one of claim 2-4 is adjusted the distance and is protected the analytical method of impact, and it is characterized in that, described step c, specifically comprises:

Its operating criterion is set up, when operating criterion is in critical condition when protection zone end fault according to the voltage boundary condition of fault point; The fault component voltage of protection zone end is:

$\mathrm{\Δ}{\stackrel{\·}{U}}^{\′}=\mathrm{\Δ}\stackrel{\·}{U}-\mathrm{\Δ}\stackrel{\·}{I}\×Z_{zd}---\left(9\right);$

For phase distance protection, $\mathrm{\Δ}\stackrel{\·}{U}=\mathrm{\Δ}{\stackrel{\·}{U}}_{\mathrm{\φ}\mathrm{\φ}},\mathrm{\Δ}\stackrel{\·}{I}=\mathrm{\Δ}{\stackrel{\·}{I}}_{\mathrm{\φ}\mathrm{\φ}},$ bC or CA;

For ground distance protection, φ=A, B or C, k=(Z ₀-Z ₁)/Z ₁;

The operating criterion of Comparison of Sudden Changing Rate of Power Frequency Components distance protection is:

$\left|\mathrm{\Δ}{\stackrel{\·}{U}}^{\′}\right|>\left|{\stackrel{\·}{U}}_{\left|0\right|}^{\′}\right|---\left(10\right);$

In formula (10), be fault front protection zone terminal voltage value, play amplitude reference effect.

6. scale wind power integration alternating current-direct current combined hybrid system according to claim 5 is adjusted the distance and is protected the analytical method of impact, and it is characterized in that, described steps d, specifically comprises:

The operation equation of power frequency variation distance is expressed as:

$|\mathrm{\Δ}\stackrel{\·}{U}-\mathrm{\Δ}\stackrel{\·}{I}\×Z_{zd}|>k_{rel}\×E---\left(11\right);$

Consider system impedance, above formula be deformed into:

$\mathrm{\Δ}\stackrel{\·}{I}\left|Z_s+Z_{zd}\right|>k_{rel}\×E;$ That is:

$\mathrm{\Δ}\stackrel{\·}{I}>\frac{k_{rel}\×E}{\left|Z_s+Z_{zd}\right|}---\left(12\right);$

From formula (12), the essence of power frequency variation distance protection is a kind of power frequency variation current protection;

Find out that its impact being subject to system operation mode and system impedance is comparatively large by its operation equation, below provide labor:

According to setting principle, generally establish safety factor k _rel=1.2, then, when transmission line dorsal part is Infinite bus system, its operation equation is electric current when namely protecting the Sudden Changing Rate electric current of installation place to be greater than 1.2 times of protection end faults could action, and the scope that is protected comparatively power frequency amount distance protection reduces 20%;

If consider according to the strategy of " inverse time lag " open and protection scope, reliable system will be taken as 2.0 or larger, and when fault transient, power frequency variation electric current is greater than 2 times of electric currents when protecting end fault, and protection range is less;

When considering system impedance, situation will become even more serious; Adopt and analyze identical method above, when system impedance is identical with the impedance of adjusting of protection, only having the fault component electric current when protection installation place to meet:

time, the action of protection ability, namely now only have fault component electric current to be greater than the setting current protection ability action of 2.4 times, if system impedance strengthens further, protection range will reduce further.