CN101752839A - Method for improving valve short circuit protection and setting performance of current converter - Google Patents

Abstract

The invention relates to a method for improving the valve short circuit protection and setting the performance of a current converter. With a valve short circuit action function, the invention has a function of positioning a fault bridge and improves the overall performance of a constant value for the valve short circuit protection. In addition, aiming at the defects of braking function of the valve short circuit protection, the invention provides a sectional type braking function considering the selectivity and the sensitive requirements; and by combining the running characteristics of a high-voltage direct current power output system, the invention provides a practical parameter determination method aiming at the sectional type function. For the valve short circuit protection of the high-voltage direct current power output system, the invention can consider the requirements for meeting the sensitivity and the selectivity during fault generation.

Description

A kind of method that improves valve short circuit protection and setting performance of current converter

Technical field

The invention belongs to the HVDC (High Voltage Direct Current) transmission system technical field of relay protection, be specifically related to a kind of method that improves valve short circuit protection and setting performance of current converter, belong to the innovative technology of the method that improves valve short circuit protection and setting performance of current converter.

Background technology

For the safety that ensures a main equipment of direct current and the stable operation of alternating current-direct current interconnected network, disposed complete direct current protecting system in HVDC (High Voltage Direct Current) transmission system (being called for short HVDC (High Voltage Direct the Current)) engineering.The overstress of converter valve is one of the most serious accident of DC transmission system.When converter valve short circuit, converter AC side phase fault or the dc terminal outlet short circuit of the rectification side valve Room when (claiming that hereinafter these faults are the specified fault of valve short circuit protection), all may cause converter valve to suffer overstress.For this reason, existing HVDC engineering has all disposed valve short circuit protection.When above-mentioned fault takes place, protection action outlet, locking converter, tripping AC circuit breaker and carry out the utmost point and isolate are to guarantee the safety of converter.

At present, obtain to mainly contain two classes than the valve short circuit protection operation equation of extensive use.After the main valve short circuit protection of two classes of HVDC engineering all utilizes specified fault to take place, the bare maximum of converter ac-side current greater than this phenomenon of direct current as the protection criterion.The differential current function in operation equation left side is called function of movement, and the action definite value function on right side is called the braking function.All there are certain difference in the function of movement in this two classes operation equation left side and the braking function on right side.The left side of one class operation equation is taken as the poor of the alternating current of corresponding bridge and smaller that dc terminal goes out line current, and the right side is taken as constant; The left side of another kind of operation equation is taken as the poor of the greater of Y bridge and D bridge alternating current and the greater that dc terminal goes out line current, and the right side is taken as the orthoscopic function.Under other faults, the action situation of two class operation equations is analyzed in the specified fault of valve short circuit protection and district, its characteristic can be summarized as follows:

1) two class valve short circuit protections have adopted different operation equations.But this two classes valve short circuit protection is under the valve short circuit protection specified fault, and sensitivity is identical;

2) in the district under the specified fault of non-valve short circuit protection, first kind protection may be moved, and the protection of second class reliably is failure to actuate;

3) first kind protection has been adopted different operation equations at the Y bridge respectively with the D bridge, has possessed the function of correct fault location bridge under the valve short circuit protection specified fault.

From above analysis as can be known, there is following defective in the valve short circuit protection operation equation of extensive use at present: 1. the second class valve short circuit protection has only adopted an operation equation to whole converter, thereby does not possess the function of fault location bridge; 2. the braking function of two class valve short circuit protections is respectively constant and orthoscopic braking function, when the external area error short circuit current increases, increases the possible malfunction of first kind protection owing to enter the unsymmetrical current of protection; Second class protection selectivity when guaranteeing external area error requires the restraint coefficient value bigger, might tripping under the active fault in the district.

Summary of the invention

The objective of the invention is to consider the problems referred to above and provide a kind of can be when the valve short circuit protection troubles inside the sample space takes place, take into account the method for the raising valve short circuit protection and setting performance of current converter that satisfies sensitivity and optionally require.The present invention possesses the function of fault location bridge, can improve the overall performance of protection definite value.

Technical scheme of the present invention is: the present invention improves the method for valve short circuit protection and setting performance of current converter, proposes valve short circuit protection operation equation and valve short circuit protection segmented braking function,

Wherein the valve short circuit protection operation equation is to adopt i at Y bridge and D bridge respectively in its left side function of movement _VYAnd i _VD, make this protection possess the function of fault location bridge, the function of movement that is proposed is suc as formula shown in (1), (2)

i _dY＝i _VY-max(i _dH，i _dN) (1)

i _dD＝i _VD-max(i _dH，i _dN) (2)

In the formula: i _VYAnd i _VDBe respectively Y bridge three-phase alternating current i _AcYjWith D bridge three-phase alternating current i _AcDjBare maximum (j=a, b, c); i _DHAnd i _DNBe respectively the high-pressure side and the neutral line side direct current of converter; Protection measuring amount i _AcYj, i _AcDj, i _DHAnd i _DNPoint position sees accompanying drawing 4 for details.

The expression formula of valve short circuit protection segmented braking function and operating characteristics are respectively suc as formula (3)

g＝max{I ₀，m(i _res-I _res0)+I ₀} (3)

I in the formula ₀Be starting current; I _ResBBe keen current; i _ResBe stalling current.

As shown in Figure 1: i _Vi=i _VY, i _VDOr max{i _VY, i _VD; i _Dj=min{i _DH, i _DNOr max{i _DH, i _DN; i _d=i _Vi-i _DjBe differential current.Work as i _Dj≤ I _Res0The time, get g=I ₀Work as i _Dj＞I _Res0The time, get g=m (i _Res-I _Res0)+I ₀Like this, both can reduce I ₀To improve the sensitivity of protection, also can improve restraint coefficient k _ResTo guarantee the selectivity of protection.Owing to when the fault that the B point is corresponding takes place, i must be arranged _ResB＜1.0, so desirable keen current I _ResB=1.0.Slope m and maximum restraint coefficient k _Resmax, maximum stalling current I _ResmaxBetween satisfy following relation:

k _resmaxI _resmax＝m(I _resmax-I _res0)+I ₀

(4)

Therefore, ask for m and only need determine starting current I ₀With maximum restraint coefficient k _Resmax

Definite method of relevant parameter is as follows in the above-mentioned segmented braking function:

When adopting aforementioned segmented to brake function, valve short circuit protection need be determined starting current I ₀With maximum restraint coefficient k _ResmaxThe caused unsymmetrical current of error of determining main consideration current transformer of these parameters; consider that measuring the loop in the HVDC system adopts the redundancyization configuration; protection was failure to actuate when Current Transformer Secondary broke in the time of need not considering normally to move in definite process of parameter; the analogy AC transmission system gets following parameter determination method:

(1) I ₀Determine by the unsymmetrical current that reliably escapes under the maximum overload operating mode, that is:

I ₀＝K _relK _erK _stK _ovl (5)

In the formula: K _RelBe safety factor, get 1.3 ~ 1.5; K _ErFor the worst error coefficient of current transformer, get 0.1; K _StBe the homotype coefficient of current transformer, because i _ViAnd i _DjRecord by AC current transformer and DC current transformer respectively, get K _St=1; K _OvlBe maximum overload multiple;

(2) k _ResmaxMaximum imbalance current when escaping external area error determines, that is:

i _opmax＝K _relK _er′K _sti _kmax (6)

In the formula: i _OpmaxMaximum actuation electric current for protection; i _KmaxFlow through the maximum short circuit current of the external area error of current transformer; K _Er' be that current transformer is at i _KmaxUnder the worst error coefficient;

Consider i _Resmax=i _Kmax, obtain according to the definition of restraint coefficient:

$k_{\mathrm{res}\max }=\frac{K_{\mathrm{rel}}{K}_{\mathrm{er}}^{\′}{K}_{\mathrm{st}}{i}_{k\max }}{i_{\mathrm{res}\max }}=K_{\mathrm{rel}}{K}_{\mathrm{er}}^{\′}{K}_{\mathrm{st}}---\left(7\right)$

K _RelBe safety factor, get 1.3 ~ 1.5, K _ErFor the worst error coefficient of current transformer, get 0.1; K _Er' be that current transformer is at i _KmaxUnder the worst error coefficient, get 0.1; k _StBe the homotype coefficient of current transformer, because i _ViAnd i _DjRecord by AC current transformer and DC current transformer respectively, get K _St=1; K _OvlFor maximum overload multiple, get 1.5 usually;

Above-mentioned K _Rel=1.5, K _Er=0.1, K _Er'=0.1, K _St=1, K _Ovl=1.5, desirable I ₀=0.3, K _Resmax=0.2.

The method of above-mentioned sensitivity verification is as follows:

Valve short circuit protection also must be in the harshest mode, that is: the minimum mode of AC system, direct current system transmission power minimum) sensitivity of verification protection down, promptly should satisfy following relation:

$K_{\mathrm{sen}}=\frac{i_{\min }}{I_0}\≥2---\left(8\right)$

In the formula: K _SenBe sensitivity; i _MinFlow into the minimum current of protection when taking place for active fault in distinguishing.

The present invention can take into account the method for the raising valve short circuit protection and setting performance of current converter that satisfies sensitivity and optionally require when the valve short circuit protection troubles inside the sample space takes place.The present invention possesses the function of fault location bridge, can improve the overall performance of protection definite value.Be that a kind of design is ingenious, function admirable, the method for convenient and practical raising valve short circuit protection and setting performance of current converter.

Description of drawings

Fig. 1 is valve short circuit protection segmented braking function curve diagram of the present invention;

Fig. 2 is the break down change curve of inversion side correlated current when adopting two kinds of operation equations at 4 o'clock respectively of inversion side of the present invention;

Fig. 3 is the break down change curve of rectification side correlated current when adopting two kinds of operation equations at 8 o'clock respectively of rectification side of the present invention;

Fig. 4 is the present invention's 12 pulse conversion device wiring and converter typical case short trouble distribution map.Fig. 4 has mainly manifested in the protection operation equation in function of movement and the braking function used measuring point i in the formula _AcYj, i _AcDj(j=a, b, c), i _DH, i _DNDeng the position, and signal such as fault 4.

Embodiment

Embodiment:

The present invention improves the method for valve short circuit protection and setting performance of current converter, proposes valve short circuit protection operation equation and valve short circuit protection segmented braking function,

Wherein the valve short circuit protection operation equation is to adopt i at Y bridge and D bridge respectively in its left side function of movement _VYAnd i _VD, make this protection possess the function of fault location bridge, the function of movement that is proposed is suc as formula shown in (1), (2)

i _dY＝i _VY-max(i _dH，i _dN) (1)

i _dD＝i _VD-max(i _dH，i _dN) (2)

The expression formula of valve short circuit protection segmented braking function and operating characteristics are respectively suc as formula (3)

g＝max{I ₀，m(i _res-I _res0)+I ₀} (3)

Among Fig. 1: i _Vi=i _VY, i _VDOr max{i _VY, i _VD; i _Dj=min{i _DH, i _DNOr max{i _DH, i _DN; i _d=i _Vi-i _DjBe differential current.Work as i _Dj≤ I _Res0The time, get g=I ₀Work as i _Dj＞I _Res0The time, get g=m (i _Res-I _Res0)+I ₀Like this, both can reduce I ₀To improve the sensitivity of protection, also can improve restraint coefficient k _ResTo guarantee the selectivity of protection.Owing to when the fault that the B point is corresponding takes place, i must be arranged _ResB＜1.0, so desirable keen current I _ResB=1.0.Slope m and maximum restraint coefficient k _Resmax, maximum stalling current I _ResmaxBetween satisfy following relation:

k _resmaxI _resmax＝m(I _resmax-I _res0)+I ₀

(4)

Therefore, ask for m and only need determine starting current I ₀With maximum restraint coefficient k _Resmax

Definite method of relevant parameter is as follows in the above-mentioned segmented braking function:

When adopting aforementioned segmented to brake function, valve short circuit protection need be determined starting current I ₀With maximum restraint coefficient k _ResmaxThe caused unsymmetrical current of error of determining main consideration current transformer of these parameters; consider that measuring the loop in the HVDC system adopts the redundancyization configuration; protection was failure to actuate when Current Transformer Secondary broke in the time of need not considering normally to move in definite process of parameter; the analogy AC transmission system gets following parameter determination method:

(1) I ₀Determine by the unsymmetrical current that reliably escapes under the maximum overload operating mode, that is:

I ₀＝K _relK _erK _stK _ovl (5)

In the formula: K _RelBe safety factor, get 1.3 ~ 1.5; K _ErFor the worst error coefficient of current transformer, get 0.1; K _StBe the homotype coefficient of current transformer, because i _ViAnd i _DjRecord by AC current transformer and DC current transformer respectively, get K _St=1; K _OvlBe maximum overload multiple;

(2) k _ResmaxMaximum imbalance current when escaping external area error determines, that is:

i _opmax＝K _relK _er′K _sti _kmax (6)

In the formula: i _OpmaxMaximum actuation electric current for protection; i _KmaxFlow through the maximum short circuit current of the external area error of current transformer; K _Er' be that current transformer is at i _KmaxUnder the worst error coefficient;

Consider i _Resmax=i _Kmax, obtain according to the definition of restraint coefficient:

$k_{\mathrm{res}\max }=\frac{K_{\mathrm{rel}}{K}_{\mathrm{er}}^{\′}{K}_{\mathrm{st}}{i}_{k\max }}{i_{\mathrm{res}\max }}=K_{\mathrm{rel}}{K}_{\mathrm{er}}^{\′}{K}_{\mathrm{st}}---\left(7\right)$

K _RelBe safety factor, get 1.3 ~ 1.5, K _ErFor the worst error coefficient of current transformer, get 0.1; K _Er' be that current transformer is at i _KmaxUnder the worst error coefficient, get 0.1; K _StBe the homotype coefficient of current transformer, because i _ViAnd i _DjRecord by AC current transformer and DC current transformer respectively, get K _St=1; K _OvlFor maximum overload multiple, get 1.5 usually; Provided under the special parameter value, according to the calculating gained I of (5) and (7) formula ₀And K _Resmax, for example: if K _Rel=1.5, K _Er=0.1, K _Er'=0.1, K _St=1, K _Ovl=1.5, desirable I ₀=0.3, k _Resmax=0.2.

The method of above-mentioned sensitivity verification is as follows:

Valve short circuit protection also must be in the harshest mode, that is: the minimum mode of AC system, direct current system transmission power minimum) sensitivity of verification protection down, promptly should satisfy following relation:

$K_{\mathrm{sen}}=\frac{i_{\min }}{I_0}\≥2---\left(8\right)$

In the formula: K _SenBe sensitivity; i _MinFlow into the minimum current of protection when taking place for active fault in distinguishing.

Be example with CIGRE direct current transportation standard testing system below, to verifying of above-mentioned operation equation.At measuring point i _DHDuring near line side dc terminal outlet short circuit, obtain the maximum short circuit current i of external area error _KmaxThe unsymmetrical current of external area error is by simulating the noise jamming of measuring electric current adding current amplitude 10% size.After adopting time constant to be the low-pass first order filter of 2ms, i _Kmax=2.124, i _Min=1.8, continue to use the aforementioned parameters choosing method, get m=0.11, K _Sen=1.8/0.3＞2.After bringing formula (3) into, obtain the valve short circuit protection operation equation that following two classes adopt segmented braking function in conjunction with the aforementioned activities function:

i _VY(i _VD)-min(i _dH，i _dN)＞max{0.3，0.11{min(i _dH，i _dN)-1.0]+0.3}

(9)

i _VY(i _VD)-max(i _dH，i _dN)＞max{0.3，0.11{max(i _dH，i _dN)-1.0]+0.3}

(10)

Adopt the valve short circuit protection based on operation equation (9) and (10) respectively, under 12 kinds of faults and some external area errors in the district of CIGRE test macro rectification side and inversion side, the action situation of protection is tested.For simplifying the analysis, omit the action policy emulation (, throwing the bypass equity) of protection, be i.e. remove fault immediately after the protection action as phase shift.As space is limited, only provide the inversion side break down 4 and the rectification side broke down 8 o'clock, the electric current change curve of each measurement point when adopting two kinds of valve short circuit protections, as shown in Figures 2 and 3.As seen from Figure 2, when the inversion side breaks down 4 the time, based on the equal correct operation of valve short circuit protection of operation equation (9) and (10), the measurement point current variation is identical, so only provided one group of electric current change curve.As seen from Figure 3, when the rectification side breaks down 8 the time,, correctly be failure to actuate based on the valve short circuit protection of operation equation (10) based on the valve short circuit protection correct operation of operation equation (9).

Simulation result shows: (1) adopts the action situation of valve short circuit protection of segmented braking function consistent with the valve short circuit protection of present extensive use under all faults, shows the method that the proposed correctness aspect theoretical; (2) the segmented braking function that is proposed makes valve short circuit protection have good selectivity and sensitivity concurrently.

Claims (4)

1. a method that improves valve short circuit protection and setting performance of current converter is characterized in that proposing valve short circuit protection operation equation and valve short circuit protection segmented braking function,

Wherein the valve short circuit protection operation equation is to adopt i at Y bridge and D bridge respectively in its left side function of movement _VYAnd i _VD, make this protection possess the function of fault location bridge, the function of movement that is proposed is suc as formula shown in (1), (2)

i _dY＝i _VY-max(i _dH，i _dN)(1)

i _dD＝i _VD-max(i _dH，i _dN)(2)

In the formula: i _VYAnd i _VDBe respectively Y bridge three-phase alternating current i _AcYjWith D bridge three-phase alternating current i _AcDjBare maximum (j=a, b, c); i _DHAnd i _DNBe respectively the high-pressure side and the neutral line side direct current of converter;

The expression formula of valve short circuit protection segmented braking function and operating characteristics are respectively suc as formula (3)

g＝max{I ₀，m(i _res-I _res0)+I ₀} (3)

I in the formula ₀Be starting current; I _ResBBe keen current; i _ResBe stalling current;

i _Vi=i _VY, i _VDOr max{i _VY, i _VD; i _Dj=min{i _DH, i _DNOr max{i _DH, i _DN; i _d=i _Vi-i _DjBe differential current, work as i _Dj≤ I _Res0The time, get g=I ₀Work as i _Dj＞I _Res0The time, get g=m (i _Res-I _Res0)+I ₀Like this, both reduced I ₀To improve the sensitivity of protection, also improve restraint coefficient k _ResTo guarantee the selectivity of protection, when taking place, i must be arranged owing to the corresponding fault of B point _ResB＜1.0, therefore get keen current I _ResB=1.0.Slope m and maximum restraint coefficient k _Resmax, maximum stalling current I _ResmaxBetween satisfy following relation:

k _resmaxI _resmax＝m(I _resmax-I _res0)+I ₀ (4)

Therefore, ask for m and only need determine starting current I ₀With maximum restraint coefficient k _Resmax

2. the method for raising valve short circuit protection and setting performance of current converter according to claim 1 is characterized in that definite method of relevant parameter in the above-mentioned segmented braking function is as follows:

When adopting aforementioned segmented to brake function, valve short circuit protection need be determined starting current I ₀With maximum restraint coefficient k _ResmaxThe caused unsymmetrical current of error of determining main consideration current transformer of these parameters; consider that measuring the loop in the HVDC system adopts the redundancyization configuration; protection was failure to actuate when Current Transformer Secondary broke in the time of need not considering normally to move in definite process of parameter; the analogy AC transmission system gets following parameter determination method:

(1) I ₀Determine by the unsymmetrical current that reliably escapes under the maximum overload operating mode, that is:

I ₀＝K _relK _erK _stK _ovl (5)

In the formula: K _RelBe safety factor, get 1.3 ~ 1.5; K _ErFor the worst error coefficient of current transformer, get 0.1; K _StBe the homotype coefficient of current transformer, because i _ViAnd i _DjRecord by AC current transformer and DC current transformer respectively, get K _St=1; K _OvlBe maximum overload multiple;

(2) k _ResmaxMaximum imbalance current when escaping external area error determines, that is:

i _opmax＝K _relK _er′K _sti _kmax (6)

In the formula: i _OpmaxMaximum actuation electric current for protection; i _KmaxFlow through the maximum short circuit current of the external area error of current transformer; K _Er' be that current transformer is at i _KmaxUnder the worst error coefficient;

Consider i _Resmax=i _Kmax, obtain according to the definition of restraint coefficient:

$k_{\mathrm{res}\max }=\frac{K_{\mathrm{rel}}{K}_{\mathrm{er}}^{\′}{K}_{\mathrm{st}}{i}_{k\max }}{i_{\mathrm{res}\max }}=K_{\mathrm{rel}}{K}_{\mathrm{er}}^{\′}{K}_{\mathrm{st}}---\left(7\right)$

K _RelBe safety factor, get 1.3 ~ 1.5, K _ErFor the worst error coefficient of current transformer, get 0.1; K _Er' be that current transformer is at i _KmaxUnder the worst error coefficient, get 0.1; K _StBe the homotype coefficient of current transformer, because i _ViAnd i _DjRecord by AC current transformer and DC current transformer respectively, get K _St=1; K _OvlFor maximum overload multiple, get 1.5 usually;

3. the method for raising valve short circuit protection and setting performance of current converter according to claim 1 is characterized in that above-mentioned K _Rel=1.5, K _Er=0.1, K _Er'=0.1, K _St=1, K _Ovl=1.5, I ₀=0.3, k _Resmax=0.2.

4. according to the method for each described raising valve short circuit protection and setting performance of current converter of claim 1 to 3, it is characterized in that the method for above-mentioned sensitivity verification is as follows:

Valve short circuit protection also must be in the harshest mode, that is: the minimum mode of AC system, direct current system transmission power minimum) sensitivity of verification protection down, promptly should satisfy following relation:

$K_{\mathrm{sen}}=\frac{i_{\min }}{I_0}\≥2---\left(8\right)$

In the formula: K _SenBe sensitivity; i _MinFlow into the minimum current of protection when taking place for active fault in distinguishing.

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