CN105846408A - Pilot protection method for power distribution network having distributed DFIG type wind motor - Google Patents

Abstract

The invention discloses a pilot protection method for a power distribution network having a distributed DFIG type wind motor. The method comprises the following steps: fault current waveforms at protection installation places positioned at two ends of a line are extracted and analyzed, a Prony algorithm is applied to discrete data of currents, magnitude of attenuation factors of fault currents at the two ends is calculated, attenuation factor difference between the currents at the two ends under failure conditions can be obtained after the attenuation factors of the two ends are compared with each other, and whether an internal fault or an external fault occurs can be corrected determined after the attenuation factor difference is compared with a protection setting value. The method provided in the invention can effectively and reliably distinguish internal and external faults in the line, specific characteristics of a distributed power source can be effectively utilized, and the method has certain application value in practical engineering.

Description

Power distribution network longitudinal protection method containing distributed DFIG type wind turbine

Technical field

The invention belongs to power distribution network technical field of relay protection, be specifically related to a kind of joining containing distributed DFIG type wind turbine Electrical network longitudinal protection method.

Background technology

After wind-driven generator accesses power distribution network, power distribution network becomes the system of multi-source, especially as wind-power electricity generation permeability Strengthen so that it is the impact on power distribution network becomes apparent from；Simultaneously because the randomness exerted oneself of wind-driven generator and uncertainty, cause Traditional overcurrent protection is difficult in adapt to, and result in distribution protection and arranges more difficulty.In actual engineer applied, Double-fed type influence generator (DFIG, Doubly-fed Induction Generator) is mainstream model, and double-fed type wind-force Its fault characteristic of electromotor is increasingly complex compared with for inverse distributed power, therefore, for the research of its fault transient characteristic Most important.

At present, both at home and abroad the guard method containing distributed power source is mainly had: (1) proposes a kind of direction over current protection The scheme protected, this method solve distributed power source and access the problem of protection directivity brought, it is to avoid protection element is reverse The situation of malfunction；(2) utilize fault location and analysis method that distribution protection is carried out certain improvement, also achieve certain Effect；(3) output capacity of distributed power source has been carried out certain restriction so that it is protection original to power distribution network will not cause shadow Ring；(4) for the protection in terms of distributed power source transient characterisitics.For (1), it utilizes power direction to solve multi-source event The differentiation in barrier direction, but used voltage, it is difficulty with in actual power distribution network.(2) make use of the mode of communication to joining in The fault of electrical network processes, and has bigger uncertainty in terms of reliability.Output capacity to distributed power source in (3) Limit, do not meet country's purpose to energy development.Although a kind of transient characterisitics to distributed power source are carried out Research, but the aspect that the transient characterisitics of double-feedback aerogenerator are combined with distribution protection almost without.

Summary of the invention

It is an object of the invention to provide a kind of power distribution network longitudinal protection method containing distributed DFIG type wind turbine, solve For being connected to that the guard method of the power distribution network of DFIG is complicated present in prior art, do not adapt to the asking of transient characterisitics of DFIG Topic.

The technical solution adopted in the present invention is, a kind of power distribution network pilot protection side containing distributed DFIG type wind turbine Method, specifically implements according to following steps:

Step 1: gathered respectively by the head end current transformer of power distribution network of DFIG type wind turbine, end current transformer Current value at head end chopper, end chopper, and the current value recorded is delivered to head end programmable processor, end respectively End programmable processor, carries out data process；

Step 2: head end programmable processor, end programmable processor send respectively according to step 1 data processed result Regulation and control instruction controls head end chopper, end open circuit to head end breaker actuation controller, end breaker actuation controller Device, it is achieved the longitudinal protection method of the power distribution network of DFIG type wind turbine.

The feature of the present invention also resides in:

Step 1 carries out data process detailed process:

Step 1.1: calculate the current value at head end chopper, end chopper initially with Prony algorithm corresponding Current attenuation factor values, be designated as α respectively₁、α₂；

Step 1.2: calculate α₁、α₂Between difference, by absolute value and the α of difference_setCompare, realize the vertical of circuit UNPROFOR is protected:

1) as | α₁-α₂| ＞ α_set, it determines occur between circuit for fault, the protection device action at circuit two ends, cut off Fault；

2) as | α₁-α₂| ＜ α_set, it determines occurring outside circuit for fault, the protection device at circuit two ends is failure to actuate.

Step 1.1 uses Prony algorithm to calculate the electric current that the current value at head end chopper, end chopper is corresponding Decay factor value, detailed process is:

Different types of fault, the fault current transient state number that will obtain is there is by PSCAD emulation experiment simulation power distribution network According to importing matlab program, calculate declining of head end chopper and end circuit breaker current under different faults by Prony algorithm The value of subtracting coefficient；

Wherein the principle of Prony algorithm is as follows:

$\begin{array}{c}\hat{x}\left(n\right)=\underset{m=1}{\overset{p}{\Σ}}{b}_m{z}_m^n,\left(n=0,1,\mathrm{...},N-1,\mathrm{...}\right)\\ b_m=A_m\exp \left({\mathrm{j\θ}}_m\right)\\ z_m=\exp \[\left({\mathrm{\α}}_m+j2{\mathrm{\πf}}_m\right)\mathrm{\Δ}t\]\end{array}---\left(1\right)$

In formula: the sinusoidal component number that n decomposes；The exponent number of p Prony model；The number of N sampled data points； A_mAmplitude；α_mDamping factor；f_mFrequency of oscillation；θ_mPhase place；The Δ t sampling interval；

The detailed process utilizing above-mentioned principle to calculate decay factor is:

(1) definition:

$r(i,j)=\underset{n=p}{\overset{N-1}{\Σ}}x(n-j)x^{*}(n-i)---\left(2\right)$

In formula: x^*(.) is the conjugate complex number of x (.)；

(2) the fault current Temporal Data that l-G simulation test obtains is utilized, in conjunction with formula (2), structural matrix:

$R=\left[\begin{array}{cccc}r\left(1,0\right)& r\left(1,1\right)& \mathrm{...}& r\left(1,p_e\right)\\ r\left(2,0\right)& r\left(2,1\right)& & r\left(2,p_e\right)\\ \mathrm{...}& \mathrm{...}& & \mathrm{...}\\ \mathrm{...}& \mathrm{...}& & \mathrm{...}\\ r\left(p_e,0\right)& r\left(p_e,0\right)& \mathrm{...}& r\left(p_e,p_e\right)\end{array}\right],p_e>>p---\left(3\right)$

(3) the auto-regressive parameter a of R is determined by SVD-TLS method₁,...,a_p；

(4) multinomial is solved

1+a₁z^-1+...+a_pz^-p=0 (4)

Obtain root z_i(i=1 ..., p)

(5) parameter b is calculated

$\left[\begin{array}{cccc}1& 1& \mathrm{...}& 1\\ z_1& z_2& \mathrm{...}& z_p\\ .& .& & .\\ .& .& \mathrm{...}& .\\ .& .& & .\\ .& .& & .\\ .& .& \mathrm{...}& .\\ .& .& & .\\ z_1^{N-1}& z_2^{N-1}& \mathrm{...}& z_p^{N-1}\end{array}\right]\·\left[\begin{array}{c}{b}_1\\ b_2\\ .\\ .\\ .\\ .\\ .\\ .\\ b_p\end{array}\right]=\left[\begin{array}{c}\hat{x}\left(0\right)\\ \hat{x}\left(1\right)\\ .\\ .\\ .\\ .\\ .\\ .\\ \hat{x}\left(N-1\right)\end{array}\right]---\left(5\right)$

Wherein,

$\hat{x}\left(n\right)=\underset{i=1}{\overset{p}{\Σ}}{\mathrm{\α}}_i\hat{x}\left(n-i\right),n=0,1,2,\mathrm{...}N-1;$

Then:

(6) attenuation factor is calculated_i

α_i=ln | z_i/Δt| (6)

Wherein i=1 ..., p.

The distribution network system of DFIG type wind turbine includes power supply, and power supply is connected by step-down transformer and the first bus, from Draw a feeder line at first bus, feeder line be provided with the second bus, DFIG wind energy turbine set by the first booster transformer, the Two booster transformers are linked at the second bus；Head end chopper and detection head end open circuit it is provided with in the exit of the first bus The head end current transformer of current value at device, head end chopper is connected with head end breaker actuation controller, and head end electric current is mutual Sensor and head end breaker actuation controller are all connected with head end programmable processor；Second bus exit is provided with end The end current transformer of current value at chopper and detection end chopper, end chopper controls with end breaker actuation Device is connected, and end current transformer and end breaker actuation controller are all connected with end programmable processor.

The invention has the beneficial effects as follows: 1) present invention take into account the transient characterisitics that distributed power source is intrinsic, for protection Setting can be more accurate, reliability and the selectivity of the distribution protection being connected to DFIG can be greatly improved；2) exist Make use of pilot protection in dual power supply form, only use the magnitude of current, it is the most relatively simple that it calculates process, and more traditional For pilot protection, the highest for its adaptability of circuit having branch line, the practicality in power distribution network is high.

Accompanying drawing explanation

Fig. 1 is the structural representation of the distribution network system of DFIG type wind turbine in the present invention；

Fig. 2 is the flow chart of power distribution network longitudinal protection method of the present invention；

Fig. 3 is the fault current characteristics schematic diagram of the power distribution network of DFIG type wind turbine of the present invention.

In figure, 1. power supply, 2. step-down transformer, 3. the first bus, 4.DFIG wind energy turbine set, 5. the second bus, 6. first liter Pressure transformer, 7. the second booster transformer, 8. end chopper, 9. head end chopper, 10. end current transformer, 11. head ends Current transformer, 12. end programmable processors, 13. head end programmable processors, 14. end breaker actuation controllers, 15. head end breaker actuation controllers.

Detailed description of the invention

The present invention is described in detail with detailed description of the invention below in conjunction with the accompanying drawings.

The distribution network system of DFIG type wind turbine in the present invention, structure is as it is shown in figure 1, include power supply 1, and power supply 1 is by fall Pressure transformer 2 is connected with the first bus 3, draws a feeder line, be provided with the second bus 5 on feeder line at the first bus 3, DFIG wind energy turbine set 4 is linked at the second bus 5 by first booster transformer the 6, second booster transformer 7；At the first bus 3 Exit is provided with the head end current transformer 11 of current value, head end chopper at head end chopper 9 and detection head end chopper 9 9 are connected with head end breaker actuation controller 15, head end current transformer 11 and head end breaker actuation controller 15 all with Head end programmable processor 13 connects；It is provided with at end chopper 8 and detection end chopper 8 in the second bus 5 exit The end current transformer 10 of current value, end chopper 8 is connected with end breaker actuation controller 14, and end current is mutual Sensor 10 and end breaker actuation controller 14 are all connected with end programmable processor 12.

A kind of power distribution network longitudinal protection method containing distributed DFIG type wind turbine of the present invention, flow process is as in figure 2 it is shown, concrete Implement according to following steps:

Step 1: by the head end current transformer 11 of power distribution network of DFIG type wind turbine, end current transformer 10 respectively Gather the current value at head end chopper 9, end chopper 8, and the current value recorded is delivered to respectively head end place able to programme Reason device 13, end programmable processor 12, carry out data process, and detailed process is:

Step 1.1: calculate the current value pair at head end chopper 9, end chopper 8 initially with Prony algorithm The current attenuation factor values answered, is designated as α respectively₁、α₂, detailed process is:

Different types of fault, the fault current transient state number that will obtain is there is by PSCAD emulation experiment simulation power distribution network According to importing matlab program, calculate declining of head end chopper and end circuit breaker current under different faults by Prony algorithm The value of subtracting coefficient；

Wherein the principle of Prony algorithm is as follows:

$\begin{array}{c}\hat{x}\left(n\right)=\underset{m=1}{\overset{p}{\Σ}}{b}_m{z}_m^n,\left(n=0,1,\mathrm{...},N-1,\mathrm{...}\right)\\ b_m=A_m\exp \left({\mathrm{j\θ}}_m\right)\\ z_m=\exp \[\left({\mathrm{\α}}_m+j2{\mathrm{\πf}}_m\right)\mathrm{\Δ}t\]\end{array}---\left(1\right)$

In formula: the sinusoidal component number that n decomposes；The exponent number of p Prony model；The number of N sampled data points； A_mAmplitude；α_mDamping factor；f_mFrequency of oscillation；θ_mPhase place；The Δ t sampling interval；

The detailed process utilizing above-mentioned principle to calculate decay factor is:

(1) definition:

$r(i,j)=\underset{n=p}{\overset{N-1}{\Σ}}x(n-j)x^{*}(n-i)---\left(2\right)$

In formula: x^*(.) is the conjugate complex number of x (.)；

(2) the fault current Temporal Data that l-G simulation test obtains is utilized, in conjunction with formula (2), structural matrix:

$R=\left[\begin{array}{cccc}r\left(1,0\right)& r\left(1,1\right)& \mathrm{...}& r\left(1,p_e\right)\\ r\left(2,0\right)& r\left(2,1\right)& & r\left(2,p_e\right)\\ \mathrm{...}& \mathrm{...}& & \mathrm{...}\\ \mathrm{...}& \mathrm{...}& & \mathrm{...}\\ r\left(p_e,0\right)& r\left(p_e,0\right)& \mathrm{...}& r\left(p_e,p_e\right)\end{array}\right],p_e>>p---\left(3\right)$

(3) the auto-regressive parameter a of R is determined by SVD-TLS method₁,...,a_p；

(4) multinomial is solved

1+a₁z^-1+...+a_pz^-p=0 (4)

Obtain root z_i(i=1 ..., p)

(5) parameter b (5) is calculated

$\left[\begin{array}{cccc}1& 1& \mathrm{...}& 1\\ z_1& z_2& \mathrm{...}& z_p\\ .& .& & .\\ .& .& \mathrm{...}& .\\ .& .& & .\\ .& .& & .\\ .& .& \mathrm{...}& .\\ .& .& & .\\ z_1^{N-1}& z_2^{N-1}& \mathrm{...}& z_p^{N-1}\end{array}\right]\·\left[\begin{array}{c}{b}_1\\ b_2\\ .\\ .\\ .\\ .\\ .\\ .\\ b_p\end{array}\right]=\left[\begin{array}{c}\hat{x}\left(0\right)\\ \hat{x}\left(1\right)\\ .\\ .\\ .\\ .\\ .\\ .\\ \hat{x}\left(N-1\right)\end{array}\right]---\left(5\right)$

Wherein,

$\hat{x}\left(n\right)=\underset{i=1}{\overset{p}{\Σ}}{\mathrm{\α}}_i\hat{x}\left(n-i\right),n=0,1,2,\mathrm{...}N-1;$

Then:

(6) attenuation factor is calculated_i

α_i=ln | z_i/Δt| (6)

Wherein i=1 ..., p.

Step 1.2: calculate α₁、α₂Between difference, by absolute value and the α of difference_setCompare, realize the vertical of circuit UNPROFOR is protected:

1) as | α₁-α₂| ＞ α_set, it determines occur between circuit for fault, the protection device action at circuit two ends, cut off Fault；

2) as | α₁-α₂| ＜ α_set, it determines occurring outside circuit for fault, the protection device at circuit two ends is failure to actuate.

Step 2: head end programmable processor 13, end programmable processor 12 are according to step 1 data processed result respectively Send regulation and control instruction to head end breaker actuation controller 15, end breaker actuation controller 14 to control head end chopper 9, End chopper 8, it is achieved the longitudinal protection method of the power distribution network of DFIG type wind turbine.

Embodiment:

Step 1: with the fault current under the three-phase ground fault of the output of DFIG wind energy turbine set shown in Fig. 3 (a) and Fig. 3 (b) institute The big power supply shown is tested as a example by the fault current under three-phase ground fault, and algorithm time window is quick in view of protection Property, select 20ms.Current waveform is filtered, filters serious wave distortion point.

Step 2: utilize above-mentioned Prony algorithm that above-mentioned data are carried out decay factor calculating, draws each self-corresponding decline The size of subtracting coefficient is α₁、α₂。

Step 3: solve | α₁-α₂| value, be designated as Δ α.

Step 4: in view of the measurement error in reality, arranges α here_set=0.5, program calculated result is as shown in table 1:

Table 1 protection differentiates result

Δ α ＞ 0.5 as seen from the above table, protection can correct operation.

Step 5: to as shown in table 2 with a large amount of test results of protection under different capabilities:

A large amount of test results of table 2 protection

As seen from the above table, use the power distribution network longitudinal protection method of the present invention, can correct operation.

Claims (4)

1. the power distribution network longitudinal protection method containing distributed DFIG type wind turbine, it is characterised in that specifically according to following step Rapid enforcement:

Step 1: by the head end current transformer (11) of the power distribution network of DFIG type wind turbine, end current transformer (10) respectively Gather head end chopper (9), the current value at end chopper (8) place, and the current value recorded is delivered to head end respectively can compile Thread processor (13), end programmable processor (12), carry out data process；

Step 2: head end programmable processor (13), end programmable processor (12) are according to step 1 data processed result respectively Send regulation and control instruction and control head end open circuit to head end breaker actuation controller (15), end breaker actuation controller (14) Device (9), end chopper (8), it is achieved the longitudinal protection method of the power distribution network of DFIG type wind turbine.

A kind of power distribution network longitudinal protection method containing distributed DFIG type wind turbine the most according to claim 1, its feature Being, described step 1 carries out data process detailed process and is:

Step 1.1: calculate head end chopper (9), the current value pair at end chopper (8) place initially with Prony algorithm The current attenuation factor values answered, is designated as α respectively₁、α₂；

Step 1.2: calculate α₁、α₂Between difference, by absolute value and the α of difference_setCompare, realize the vertical UNPROFOR of circuit Protect:

1) as | α₁-α₂| ＞ α_set, it determines occur between circuit for fault, the protection device action at circuit two ends, disengagement failure；

2) as | α₁-α₂| ＜ α_set, it determines occurring outside circuit for fault, the protection device at circuit two ends is failure to actuate.

A kind of power distribution network longitudinal protection method containing distributed DFIG type wind turbine the most according to claim 2, its feature Being, described step 1.1 uses Prony algorithm to calculate head end chopper (9), the current value pair at end chopper (8) place The current attenuation factor values answered, detailed process is:

There is different types of fault by PSCAD emulation experiment simulation power distribution network, the fault current Temporal Data obtained is led Enter matlab program, by Prony algorithm calculate under different faults the decay of head end chopper and end circuit breaker current because of The value of son；

Wherein the principle of Prony algorithm is as follows:

$\hat{x}\left(n\right)=\underset{m=1}{\overset{p}{\Σ}}{b}_m^n{z}_m,(n=0,1,...,N-1,...)$

b_m=A_m exp(jθ_m) (1)

z_m=exp [(α_m+j2πf_m)Δt]

In formula: the sinusoidal component number that n decomposes；The exponent number of p Prony model；The number of N sampled data points；A_mShake Width；α_mDamping factor；f_mFrequency of oscillation；θ_mPhase place；The Δ t sampling interval；

The detailed process utilizing above-mentioned principle to calculate decay factor is:

(1) definition:

$r(i,j)=\underset{n=p}{\overset{N-1}{\Σ}}x(n-j)x^{*}(n-i)---\left(2\right)$

In formula: x^*(.) is the conjugate complex number of x (.)；

(2) the fault current Temporal Data that l-G simulation test obtains is utilized, in conjunction with formula (2), structural matrix:

$R=\left[\begin{array}{cccc}r\left(1,0\right)& r\left(1,1\right)& \mathrm{...}& r\left(1,p_e\right)\\ r\left(2,0\right)& r\left(2,1\right)& & r\left(2,p_e\right)\\ \mathrm{...}& \mathrm{...}& & \mathrm{...}\\ \mathrm{...}& \mathrm{...}& & \mathrm{...}\\ r\left(p_e,0\right)& r\left(p_e,0\right)& \mathrm{...}& r\left(p_e,p_e\right)\end{array}\right],p_e>>p---\left(3\right)$

(3) the auto-regressive parameter a of R is determined by SVD-TLS method₁,...,a_p；

(4) multinomial is solved

1+a₁z^-1+...+a_pz^-p=0 (4)

Obtain root z_i(i=1 ..., p)

(5) parameter b is calculated

$\left[\begin{array}{cccc}1& 1& \mathrm{...}& 1\\ z_1& z_2& \mathrm{...}& z_p\\ .& .& & .\\ .& .& \mathrm{...}& .\\ .& .& & .\\ .& .& & .\\ .& .& \mathrm{...}& .\\ .& .& & .\\ z_1^{N-1}& z_2^{N-1}& \mathrm{...}& z_p^{N-1}\end{array}\right]\·\left[\begin{array}{c}{b}_1\\ b_2\\ .\\ .\\ .\\ .\\ .\\ .\\ b_p\end{array}\right]=\left[\begin{array}{c}\hat{x}\left(0\right)\\ \hat{x}\left(1\right)\\ .\\ .\\ .\\ .\\ .\\ .\\ \hat{x}\left(N-1\right)\end{array}\right]---\left(5\right)$

Wherein,

$\hat{x}\left(n\right)=\underset{i=1}{\overset{p}{\Σ}}{\mathrm{\α}}_i\hat{x}\left(n-i\right),n=0,1,2,\mathrm{...}N-1;$

Then:

(6) attenuation factor is calculated_i

α_i=ln | z_i/Δt| (6)

Wherein i=1 ..., p.

A kind of power distribution network longitudinal protection method containing distributed DFIG type wind turbine the most according to claim 1, its feature Being, the distribution network system of described DFIG type wind turbine includes power supply (1), and power supply (1) is female with first by step-down transformer (2) Line (3) connects, and draws a feeder line, be provided with the second bus (5), DFIG wind energy turbine set (4) on feeder line from the first bus (3) It is linked into the second bus (5) place by the first booster transformer (6), the second booster transformer (7)；In going out of the first bus (3) Being provided with head end chopper (9) and the head end current transformer (11) of detection head end chopper (9) place current value at Kou, head end breaks Road device (9) is connected with head end breaker actuation controller (15), head end current transformer (11) and head end breaker actuation control Device processed (15) is all connected with head end programmable processor (13)；Be provided with in the second bus (5) exit end chopper (8) and The end current transformer (10) of detection end chopper (8) place current value, end chopper (8) and end breaker actuation control Device processed (14) is connected, end current transformer (10) and end breaker actuation controller (14) process all able to programme with end Device (12) connects.