CN110544925A - Method and system for determining the line protection range of the fault point of the outgoing line of a photovoltaic station - Google Patents

Abstract

The invention discloses a method for determining the line protection range of the fault point of a _photovoltaic field station _sending line. , transition resistance threshold Rg _max ; S3: Obtain the positive sequence voltage and positive sequence current fault value at the protection installation of the transmission line of the photovoltaic station, and the equivalent positive sequence impedance value of the exit and entrance of the photovoltaic station; S4: Express according to Z _M Formula, D _d expression, n _max , Rg _max determine the action boundary of the curved polygon; S5 : analyze the distance protection of the fault point of the photovoltaic field station sending line according to the action boundary of the curved polygon and its plane. The present invention effectively ensures that when the photovoltaic transmission line has a grounding fault through the transition resistance, the fault in the area will act instantaneously or after a time delay, and the fault outside the area will not malfunction, ensuring the stable and reliable operation of the photovoltaic field.

Description

Method and system for determining the line protection range of the fault point of the outgoing line of a photovoltaic station

technical field

The invention belongs to the technical field of electrical technology and power system protection, and in particular relates to a method and a system for determining the line protection range of a photovoltaic field station sending line fault point.

Background technique

In recent years, new energy power generation represented by photovoltaics has become an important development area of the power industry, and the installed capacity of photovoltaics has increased sharply. However, the connection of large-capacity photovoltaics to the power grid will have an impact on the traditional relay protection, and the obvious weak-feedback characteristics of photovoltaic stations will seriously affect the reliable operation of traditional distance protection.

Affected by the weak feed-in of new energy stations, the traditional distance protection has poor resistance to transition resistance. For this reason, adaptive distance protection schemes are proposed in the existing technology, but they cannot guarantee the stable and reliable operation of photovoltaic stations.

SUMMARY OF THE INVENTION

The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

Therefore, the first objective of the present invention is to propose a method for determining the line protection range of the fault point of the outgoing line of the photovoltaic station. Effectively ensure that when the photovoltaic transmission line has a grounding fault through the transition resistance, the fault in the area will act instantaneously or after a delay, and the fault outside the area will not malfunction, ensuring the stable and reliable operation of the photovoltaic station.

In order to achieve the above purpose, the method for determining the line protection range of the fault point of the photovoltaic field station transmission line proposed by the embodiment of the first aspect of the present invention includes:

S1: Determine the measurement impedance expression of the power outlet of the photovoltaic station, and the measurement impedance expression Z _M is:

In formula (1), n is the fault location coefficient, and its value is the percentage of the distance from the distance protection installation to the fault point to the total length of the photovoltaic field station transmission line; the Rg is the transition resistance;

The Z _MN is the total impedance of the transmission line of the photovoltaic field, _ZΣ is the sum of the sequence impedances of the photovoltaic field, and C _M1 and C _M0 are the positive sequence current distribution coefficient and zero of the photovoltaic field power supply respectively. sequence current distribution coefficient, the D _d is the comprehensive coefficient,

In formula (2), Z _SM1 and Z _SN1 respectively represent the equivalent positive sequence impedance at the exit and entrance of the photovoltaic station, and the equivalent positive sequence impedance at the exit of the photovoltaic station is determined by the positive sequence voltage at the exit of the photovoltaic station. The fault value and positive sequence current fault value are determined. The ρ represents the ratio of the electromotive force amplitudes of the PV field station exit and the inlet power supply before the failure of the PV field station transmission line; δ represents the occurrence of the photovoltaic field station transmission line. The phase difference of the electromotive force between the exit and entrance of the photovoltaic station before the failure;

S2: Set the fault location coefficient threshold n _max , and the transition resistance threshold Rg _max ;

S3: Obtain the positive-sequence voltage and positive-sequence current fault values at the protection installation location of the transmission line of the photovoltaic station, and the equivalent positive-sequence impedance values at the exit and entrance of the photovoltaic station;

S4: According to the Z _M expression in the S1, the value determined by the n _max , and the Rg _max , the action boundary of the curved polygon is formed, and the plane where the action boundary is located is the measured impedance value, the The fault location factor is the plane formed by the axial coordinates.

S5: Analyze the line protection range from the fault point of the photovoltaic power station sending line according to the action boundary of the curved polygon and the plane.

According to an embodiment of the present invention, the polygon in the S4 includes:

Curve I, the curve I represents a curve formed according to the value of the Z _M expression in the plane when the fault location coefficient n is zero and the transition resistance Rg takes a value from zero to Rg _max .

Curve II, the curve II represents a curve formed by the value of the Z _M expression in the plane when the value of the transition resistance Rg is from zero to Rg _max when the fault location coefficient is n _max .

Curve III, the curve III represents a curve formed according to the value of the Z _M expression in the plane when the transition resistance Rg is zero and the fault location coefficient is from zero to n _max .

Curve IV, the curve IV represents that when the transition resistance is Rg _max , the fault location coefficient forms a curve according to the value of the Z _M expression in the plane when the fault location coefficient is from zero to n _max .

According to an embodiment of the present invention, the polygon in the S4 further includes:

Curve V, the curve V represents the curve formed according to the value of the Z _M expression on the plane when the fault location coefficient is 0.8 and the value of the transition resistance Rg ranges from zero to Rg _max .

Curve VI, the curve VI indicates that when a fault occurs at the end of the adjacent line outside the failure point of the photovoltaic field station, the value of the transition resistance Rg is from zero to Rg _max according to the Z _M expression. A curve formed from the values of the plane.

According to an embodiment of the present invention, in the step S5, analyzing the distance protection of the fault point of the photovoltaic field station sending line according to the action boundary of the curved polygon and the plane includes:

The plane enclosed by the curve V, the curve IV, and the curve VI is the maximum line range within which the outgoing line fault of the photovoltaic field station falls within the protection range of the photovoltaic field station send-out line line.

According to an embodiment of the present invention, in the step S5, the distance protection of the fault point of the photovoltaic field station transmission line is analyzed according to the action boundary of the curved polygon and the plane, further comprising:

The plane enclosed by the curve II, the curve III, the curve IV, the curve V, and the curve VI and the coordinate curve is the delay action line range of the transmission line protection range of the photovoltaic field station.

A system for determining the line protection range of a photovoltaic field station send-out line fault point proposed by the embodiment of the second aspect of the present invention, the system includes:

The modeling unit is used to determine the measured impedance expression of the power outlet of the photovoltaic station, and the measured impedance expression Z _M is:

In formula (1), n is the fault location coefficient, and its value is the percentage of the distance from the distance protection installation to the fault point to the total length of the photovoltaic field station transmission line; the Rg is the transition resistance;

The Z _MN is the total impedance of the transmission line of the photovoltaic field, _ZΣ is the sum of the sequence impedances of the photovoltaic field, and C _M1 and C _M0 are the positive sequence current distribution coefficient and zero of the photovoltaic field power supply respectively. sequence current distribution coefficient, the D _d is the comprehensive coefficient,

In formula (2), Z _SM1 and Z _SN1 respectively represent the equivalent positive sequence impedance at the exit and entrance of the photovoltaic station, and the equivalent positive sequence impedance at the exit of the photovoltaic station is determined by the positive sequence voltage at the exit of the photovoltaic station. The fault value and positive sequence current fault value are determined. The ρ represents the ratio of the electromotive force amplitudes of the PV field station exit and the inlet power supply before the failure of the PV field station transmission line; δ represents the occurrence of the photovoltaic field station transmission line. The phase difference of the electromotive force between the exit and entrance of the photovoltaic station before the failure.

The setting unit is used to set the fault location coefficient threshold n _max and the transition resistance threshold Rg _max .

The obtaining unit is configured to obtain the positive sequence voltage and positive sequence current fault values at the protection installation of the transmission line of the photovoltaic field station, and the equivalent positive sequence impedance value of the exit and entrance of the photovoltaic field station.

a calculation unit, configured to form the action boundary of the curved polygon according to the Z _M expression in the modeling unit, the value determined by the n _max and the Rg _max in the setting unit, where the action boundary is located The plane is the plane formed by the measured impedance value and the fault location coefficient is the axial coordinate.

The analysis unit is configured to analyze the line protection range from the fault point of the photovoltaic field station sending line according to the action boundary of the curved polygon and the plane.

According to an embodiment of the present invention, the computing unit includes:

The first calculation unit is configured to calculate the value of the transition resistance Rg on the plane according to the Z _M expression when the value of the transition resistance Rg ranges from zero to Rg _max when the fault location coefficient n is zero.

The second calculation unit is configured to calculate the value of the transition resistance Rg on the plane according to the Z _M expression when the value of the transition resistance Rg ranges from zero to Rg _max when the fault location coefficient is n _max .

The third calculation unit is configured to calculate, when the transition resistance Rg is zero, the value of the fault location coefficient on the plane according to the Z _M expression when the fault location coefficient is from zero to n _max .

The fourth calculation unit is configured to calculate the value of the fault location coefficient on the plane according to the Z _M expression when the transition resistance is Rg _max and the fault location coefficient is from zero to n _max .

According to an embodiment of the present invention, the calculation unit further includes: a fifth calculation unit, configured to calculate the value of the transition resistance Rg from zero to Rg _max according to the Z when the fault location coefficient is 0.8 The value of _M expression in the plane.

The sixth calculation unit is used to calculate the value of the transition resistance Rg from zero to Rg _max according to the Z _M expression in the plane value.

According to an embodiment of the present invention, the analysis unit includes: a first analysis unit, configured to analyze the photovoltaic field station send-out line according to the fourth calculation unit, the fifth calculation unit, and the sixth calculation unit The external fault falls within the maximum line range of the line protection range of the transmission line of the photovoltaic field station.

According to an embodiment of the present invention, the analysis unit further includes: a second analysis unit, configured to and the sixth calculation unit analyzes the delay action line range of the protection range of the transmission line line of the photovoltaic field station.

The technical effects achieved by the invention are as follows: firstly, the method effectively solves the problem of the influence of the weak feed-in property of the photovoltaic power source on the distance protection; secondly, the adaptive distance polygon is obtained by measuring the impedance expression, which has better adaptability to the high-resistance grounding fault; Thirdly, by dividing the action areas with different time limits, it is ensured that the faults in the protected area operate correctly, and the faults outside the area do not malfunction, which provides a guarantee for the stable and reliable operation of the photovoltaic station.

Description of drawings

Exemplary embodiments of the present invention may be more fully understood by reference to the following drawings:

1 is a schematic diagram of a single-phase grounding short circuit of a double-ended system disclosed according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an action area division disclosed according to an embodiment of the present invention;

3 is a schematic diagram of a simulation system disclosed according to an embodiment of the present invention;

FIG. 4 is a flowchart of a method for determining a line protection range of a photovoltaic field station sending line fault point disclosed according to an embodiment of the present invention.

Detailed ways

In order to make those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments are part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first", "second" and the like in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It is to be understood that the data so used may be interchanged under appropriate circumstances such that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having" and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed Rather, those steps or units may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to specific embodiments.

Example 1:

In recent years, new energy power generation represented by photovoltaics has become an important development area of the power industry, and the installed capacity of photovoltaics has increased sharply. However, the connection of large-capacity photovoltaics to the power grid will have an impact on the traditional relay protection, and the obvious weak-feedback characteristics of photovoltaic stations will seriously affect the reliable operation of traditional distance protection. Affected by the weak feed-in of new energy stations, the traditional distance protection has poor resistance to transition resistance. For this reason, some scholars have proposed an adaptive distance protection scheme:

Taking a single-phase-to-ground fault as an example, the dual-source power supply system with photovoltaics is short-circuited through a single-phase to ground through a transition resistance, as shown in Figure 1. The measured impedance expression of the photovoltaic M side is:

In formula (1), n is the fault location coefficient, which is the percentage of the distance from the protection installation to the fault point to the total length of the line, △Z is the additional measurement impedance, ZMN is the total line impedance, and _ZΣ is the _sum of the sequence impedances. and. Dd is defined as the comprehensive coefficient, and its expression is:

In formula (2), Z _SM1 and Z _SN1 represent the equivalent positive sequence impedance of the M-side and N-side systems, respectively, and formula (3) is the expression of the equivalent positive sequence impedance of the photovoltaic side, where ΔU _M1 and ΔI _M1 They are the positive sequence voltage and current fault components of the PV power outlet respectively. ρ represents the ratio of the electromotive force amplitudes of the two ends of the power supply before the fault, and δ represents the phase difference of the electromotive force of the two ends of the power supply before the fault.

Equation (4) is the proportional expression of the power supply electromotive force relationship between the two ends of the M-side and N-side faults. In Equation (5), C _M1 and C _M0 are the positive sequence current distribution coefficient and the zero-sequence current distribution coefficient, respectively, indicating that the protection installations are The ratio of the sequence fault current to the corresponding sequence currents at the fault point, In order to protect the fault component of the positive sequence current of the faulty phase at the installation, To protect the zero-sequence current at the installation. and are the positive-sequence and zero-sequence currents at the fault point, respectively.

Because the M-side system is a photovoltaic station, since the photovoltaic station generally adopts the control strategy of suppressing negative sequence current, the photovoltaic side can be equivalent to no negative sequence current output after a fault, so there is no negative sequence current distribution coefficient.

It can be found from the measured impedance expression that the size of the additional impedance is related to the size of parameters such as n, Rg, ρ, δ and Z _SM1 . The size of ρ, δ and Z _SM1 can be determined by the way the system operates. In addition, according to the actual engineering needs, the range of the protected line and the withstand transition resistance value can be determined in advance, and the range of n and Rg can be determined to form the action area of the curved quadrilateral. As shown in Figure 2, the action area is composed of curves I～IV The meanings of the four curves are as follows:

Curve I: n=0, the value range of Rg is 0 to R _gmax ;

Curve II: n=n _max , the value range of Rg is 0 to R _gmax ;

Curve III: Rg=0, the value range of n is 0 to n _max ;

Curve IV: Rg=R _gmax , and the value of n ranges from 0 to n _max . Among them, R _gmax is the maximum transition resistance value that the current impedance relay can withstand, n _max is the ratio of the maximum protected length of the line to the total length of the line, usually n _max is 1, which means the full length of the protection line.

For the action of single-phase ground fault outside the inspection area of this protection. When a point outside the zone is grounded through different transition resistances, the measured impedance trace may be as shown in the curve V in Figure 2, and some of the measured impedance values (as shown in the dotted box) fall into the protection action area, which may lead to misoperation happened.

Aiming at this problem, the patent of the present invention makes technical improvements to the existing adaptive curved-sided quadrilateral characteristic distance protection. Aiming at the problem that the obvious weak feed characteristics of photovoltaic stations seriously affect the reliable operation of traditional distance protection and the existing self-adaptive distance quadrilateral characteristics have the problem of out-of-area fault misoperation, the invention provides an adaptive distance protection scheme that divides action areas with different time limits . The method can effectively distinguish the intra-area and out-of-area faults of the photovoltaic transmission line, realize the instantaneous action of the intra-area fault, and avoid the malfunction by delaying the out-of-area fault. At the same time, the maximum withstand transition resistance value can be changed according to the actual engineering requirements, and it has a strong ability to withstand transition resistance. The calculation of relevant parameters only needs to use the photovoltaic side electrical quantity of the outgoing line, and does not need the related electrical quantity of the system on the opposite side of the line.

The specific analysis process of the method is as follows:

Taking a single-phase ground fault as an example, the fault components of the three-phase positive-sequence voltage and positive-sequence current at the protection installation are obtained first, and the photovoltaic equivalent positive-sequence impedance is calculated in real time, and then the four action boundaries of the curved quadrilateral are determined by the photovoltaic side measurement impedance formula. as shown in picture 2,

Curve I: n=0, the value range of Rg is 0 to R _gmax ;

Curve II: n=n _max , the value range of Rg is 0 to R _gmax ;

Curve III: Rg=0, the value range of n is 0 to n _max ;

Curve IV: Rg=R _gmax , and the value of n ranges from 0 to n _max .

Secondly, in order to distinguish the fault at the end of the line and the fault at the outlet of the adjacent line, another curve V is determined: at 80% of the full length of the protected line, the transition resistance is from 0 to R _gmax .

Then, in order to solve the problem that the fault outside the zone falls into the action zone and causes the protection to malfunction, the curve VI: fault at the end of the adjacent line is determined, and the transition resistance is from 0 to R _gmax . Curve IV, curve V and curve VI enclosed by the red curve shaded area is the largest area where the fault outside the area falls into the protection range of this line.

Then the instantaneous action area of the adaptive distance protection is shown in Figure 2, which consists of curve I, curve II, curve III, curve IV, curve V and curve VI; the figure is composed of curve II, curve III, curve IV, curve V and The shaded area formed by the curve VI is used as the delayed action area. When the measurement impedance falls into the instantaneous action zone, the adaptive distance protection acts instantaneously. When the measurement impedance falls into the delay action zone, the adaptive distance protection judges whether the measurement impedance is still in the action zone after a delay, and the criterion is established. then action.

The technical effect achieved by the present invention: through the division of different delay action zones, the part that may fall into the action zone and the end part of the line when the fault outside the zone is divided into the delay action zone, so that under the condition of the out-of-zone fault, adjacent The line protection trips first, and then the fault is removed, and the line protection will not malfunction. Therefore, this scheme can effectively ensure that when a grounding fault occurs in the photovoltaic transmission line through the transition resistance, the fault in the area will act instantaneously or after a delay, and the fault outside the area will not be malfunctioned, ensuring the stable and reliable operation of the photovoltaic station.

Embodiment 2:

The dual power supply system model including the photovoltaic station, the model topology is shown in Figure 3, the corresponding simulation model is established in the PSCAD simulation software, the system voltage level is 110kV, the photovoltaic station capacity is 1.5MW, the two lines L1 and The lengths of L2 are 80km and 50km respectively, and the line parameters are Z1=0.105+j1.258Ω/km, Z0=0.315+j3.774Ω/km. The action of protection 1 is studied, and the faults are set as the fault at point K1 of this line and the faults of points K2 and K3 of adjacent lines.

First, obtain the three-phase positive-sequence voltage and positive-sequence current fault components at the protection installation site, as well as the three-phase measured voltage and current and zero-sequence current, calculate the photovoltaic equivalent positive-sequence impedance in real time, and then determine the six actions of the curved polygon by the photovoltaic side measured impedance formula boundary. The maximum transition resistance is 100Ω to protect the full length of the line, and 80% of the line is quick to operate. Divide the action area according to Figure 2,

Curve I: Line L1 head-end fault, Rg from 0 to 100.

Curve II: The end of line L1 is faulty, and the value of Rg ranges from 0 to 100;

Curve III: Rg is 0, the fault location is from the beginning to the end of the line L1.

Curve IV: Rg is 100, the fault location is from the beginning to the end of line L1.

Curve V: Rg from 0 to 100 at 80% of line L1.

Curve VI: Fault at the end of line L2, Rg from 0 to 100. Instantaneous action in the white area, delayed action in the shaded area.

Taking the single-phase grounding short circuit as an example, when the K1 point in the area is faulty (fault position n=0.5, transition resistance is 80Ω), the measured impedance (123.06+j33.03Ω) falls within the instantaneous action area, and the protection can act instantaneously.

When the fault of K2 point outside the zone (fault position n=1.6, transition resistance is 15Ω), the measured impedance (161.64+j47.81Ω) falls within the delay action zone, waiting for the line protection action outside the zone, the measurement impedance becomes 28.165+ j163.54Ω, which falls outside the protection range, this line will not act after the protection delay.

K3 point fault outside the zone (fault position is n=1.2 (K3), transition resistance is 10Ω), the measured impedance (47.06+j111.71Ω) falls outside the delay action zone, and the protection does not act.

The technical effects achieved by the present application are as follows: firstly, the method effectively solves the problem of the influence of the weak feed-through of photovoltaic power sources on distance protection; secondly, the adaptive distance polygon is obtained by measuring the impedance expression, which has better adaptability to high-resistance grounding faults ; Thirdly, by dividing the action areas with different time limits, it is ensured that the faults in the protected area operate correctly, and the faults outside the area do not malfunction, providing guarantee for the stable and reliable operation of the photovoltaic station.

Embodiment three:

The method for determining the line protection range of the fault point of the photovoltaic field station transmission line proposed by the embodiment of the first aspect of the present invention, as shown in FIG. 4 , includes:

S1: Determine the measurement impedance expression of the power outlet of the photovoltaic station, and the measurement impedance expression Z _M is:

In formula (1), n is the fault location coefficient, and its value is the percentage of the distance from the distance protection installation to the fault point to the total length of the photovoltaic field station transmission line; the Rg is the transition resistance;

The Z _MN is the total impedance of the transmission line of the photovoltaic field, _ZΣ is the sum of the sequence impedances of the photovoltaic field, and C _M1 and C _M0 are the positive sequence current distribution coefficient and zero of the photovoltaic field power supply respectively. sequence current distribution coefficient, the D _d is the comprehensive coefficient,

In formula (2), Z _SM1 and Z _SN1 respectively represent the equivalent positive sequence impedance at the exit and entrance of the photovoltaic station, and the equivalent positive sequence impedance at the exit of the photovoltaic station is determined by the positive sequence voltage at the exit of the photovoltaic station. The fault value and positive sequence current fault value are determined. The ρ represents the ratio of the electromotive force amplitudes of the PV field station exit and the inlet power supply before the failure of the PV field station transmission line; δ represents the occurrence of the photovoltaic field station transmission line. The phase difference of the electromotive force between the exit and entrance of the photovoltaic station before the failure;

S2: Set the fault location coefficient threshold n _max , and the transition resistance threshold Rg _max ;

S3: Obtain the positive-sequence voltage and positive-sequence current fault values at the protection installation location of the transmission line of the photovoltaic station, and the equivalent positive-sequence impedance values at the exit and entrance of the photovoltaic station;

S4: Determine the action boundary of the curved polygon according to the Z _M expression, the D _d expression, the n _max , and the Rg _max in the S1, and the plane where the action boundary is located is the measured impedance value, the fault location coefficient is a plane composed of axial coordinates.

S5: Analyze the line protection range from the fault point of the photovoltaic power station sending line according to the action boundary of the curved polygon and the plane.

According to an embodiment of the present invention, the polygon in the S4 includes:

Curve I, the curve I represents a curve formed according to the value of the Z _M expression in the plane when the fault location coefficient n is zero and the transition resistance Rg takes a value from zero to Rg _max .

Curve II, the curve II represents a curve formed by the value of the Z _M expression in the plane when the value of the transition resistance Rg is from zero to Rg _max when the fault location coefficient is n _max .

Curve III, the curve III represents a curve formed according to the value of the Z _M expression in the plane when the transition resistance Rg is zero and the fault location coefficient is from zero to n _max .

Curve IV, the curve IV represents that when the transition resistance is Rg _max , the fault location coefficient forms a curve according to the value of the Z _M expression in the plane when the fault location coefficient is from zero to n _max .

According to an embodiment of the present invention, the polygon in the S4 further includes:

Curve V, the curve V represents the curve formed according to the value of the Z _M expression on the plane when the fault location coefficient is 0.8 and the value of the transition resistance Rg ranges from zero to Rg _max .

Curve VI, the curve VI indicates that when a fault occurs at the end of the adjacent line outside the failure point of the photovoltaic field station, the value of the transition resistance Rg is from zero to Rg _max according to the Z _M expression. A curve formed from the values of the plane.

According to an embodiment of the present invention, in the step S5, analyzing the distance protection of the fault point of the photovoltaic field station sending line according to the action boundary of the curved polygon and the plane includes:

The plane enclosed by the curve V, the curve IV, and the curve VI is the maximum line range within which the outgoing line fault of the photovoltaic field station falls within the protection range of the photovoltaic field station send-out line line.

According to an embodiment of the present invention, in the step S5, the distance protection of the fault point of the photovoltaic field station transmission line is analyzed according to the action boundary of the curved polygon and the plane, further comprising:

The plane enclosed by the curve II, the curve III, the curve IV, the curve V, and the curve VI and the coordinate curve is the delay action line range of the transmission line protection range of the photovoltaic field station. That is, the area surrounded by the curve II, the curve III, the curve IV, the curve V and the curve VI and the coordinate curve and the coordinate curve are the delay action lines of the protection range of the transmission line of the photovoltaic field station The range is filled with horizontal lines in Figure 2, and the remaining blank parts are the non-delayed action line range of the transmission line protection range of the photovoltaic field station.

A system for determining the line protection range of a photovoltaic field station send-out line fault point proposed by the embodiment of the second aspect of the present invention, the system includes:

The modeling unit is used to determine the measured impedance expression of the power outlet of the photovoltaic station, and the measured impedance expression Z _M is:

In formula (1), n is the fault location coefficient, and its value is the percentage of the distance from the distance protection installation to the fault point to the total length of the photovoltaic field station transmission line; the Rg is the transition resistance;

The Z _MN is the total impedance of the transmission line of the photovoltaic field, _ZΣ is the sum of the sequence impedances of the photovoltaic field, and C _M1 and C _M0 are the positive sequence current distribution coefficient and zero of the photovoltaic field power supply respectively. sequence current distribution coefficient, the D _d is the comprehensive coefficient,

In formula (2), Z _SM1 and Z _SN1 respectively represent the equivalent positive sequence impedance at the exit and entrance of the photovoltaic station, and the equivalent positive sequence impedance at the exit of the photovoltaic station is determined by the positive sequence voltage at the exit of the photovoltaic station. The fault value and positive sequence current fault value are determined. The ρ represents the ratio of the electromotive force amplitudes of the PV field station exit and the inlet power supply before the failure of the PV field station transmission line; δ represents the occurrence of the photovoltaic field station transmission line. The phase difference of the electromotive force between the exit and entrance of the photovoltaic station before the failure.

The setting unit is used to set the fault location coefficient threshold n _max and the transition resistance threshold Rg _max .

The obtaining unit is configured to obtain the positive sequence voltage and positive sequence current fault values at the protection installation of the transmission line of the photovoltaic field station, and the equivalent positive sequence impedance value of the exit and entrance of the photovoltaic field station.

A calculation unit, configured to determine the action boundary of the curved polygon according to the Z _M expression, the D _d expression, the n _max in the setting unit, and the Rg _max in the setting unit. The plane where the action boundary is located is the plane formed by the measured impedance value and the fault location coefficient is the axial coordinate.

The analysis unit is configured to analyze the line protection range from the fault point of the photovoltaic field station sending line according to the action boundary of the curved polygon and the plane.

According to an embodiment of the present invention, the computing unit includes:

The first calculation unit is configured to calculate the value of the transition resistance Rg on the plane according to the Z _M expression when the value of the transition resistance Rg ranges from zero to Rg _max when the fault location coefficient n is zero.

The second calculation unit is configured to calculate the value of the transition resistance Rg on the plane according to the Z _M expression when the value of the transition resistance Rg ranges from zero to Rg _max when the fault location coefficient is n _max .

The third calculation unit is configured to calculate, when the transition resistance Rg is zero, the value of the fault location coefficient on the plane according to the Z _M expression when the fault location coefficient is from zero to n _max .

The fourth calculation unit is configured to calculate the value of the fault location coefficient on the plane according to the Z _M expression when the transition resistance is Rg _max and the fault location coefficient is from zero to n _max .

According to an embodiment of the present invention, the calculation unit further includes: a fifth calculation unit, configured to calculate the value of the transition resistance Rg from zero to Rg _max according to the Z when the fault location coefficient is 0.8 The value of _M expression in the plane.

The sixth calculation unit is used to calculate the value of the transition resistance Rg in the plane according to the Z _M expression when the value of the transition resistance Rg is from zero to Rg _max when the adjacent line outside the fault point of the photovoltaic field station fails. value of .

According to an embodiment of the present invention, the analysis unit includes: a first analysis unit, configured to analyze the photovoltaic field station send-out line according to the fourth calculation unit, the fifth calculation unit, and the sixth calculation unit The external fault falls within the maximum line range of the line protection range of the transmission line of the photovoltaic field station.

According to an embodiment of the present invention, the analysis unit further includes: a second analysis unit, configured to and the sixth calculation unit analyzes the delay action line range of the protection range of the transmission line line of the photovoltaic field station.

The technical effects achieved by the invention are as follows: firstly, the method effectively solves the problem of the influence of the weak feed-in property of the photovoltaic power source on the distance protection; secondly, the adaptive distance polygon is obtained by measuring the impedance expression, which has better adaptability to the high-resistance grounding fault; Thirdly, by dividing the action areas with different time limits, it is ensured that the faults in the protected area operate correctly, and the faults outside the area do not malfunction, which provides a guarantee for the stable and reliable operation of the photovoltaic station.

The above-mentioned serial numbers of the embodiments of the present application are only for description, and do not represent the advantages or disadvantages of the embodiments.

In the above-mentioned embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are only illustrative, for example, the division of the units or modules is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or modules or components May be combined or may be integrated into another system, or some features may be omitted, or not implemented. On the other hand, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, indirect coupling or communication connection of modules or units, and may be in electrical or other forms.

The units or modules described as separate components may or may not be physically separated, and components shown as units or modules may or may not be physical units or modules, that is, they may be located in one place, or may be distributed to on multiple network elements or modules. Some or all of the units or modules may be selected according to actual needs to achieve the purpose of the solution in this embodiment.

In addition, each functional unit or module in each embodiment of the present application may be integrated into one processing unit or module, or each unit or module may exist physically alone, or two or more units or modules may be integrated into one unit or module. The above-mentioned integrated units or modules may be implemented in the form of hardware, or may be implemented in the form of software functional units or modules.

The integrated unit, if implemented in the form of a software functional unit and sold or used as an independent product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the present application can be embodied in the form of software products in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, and the computer software products are stored in a storage medium , including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes .

The above are only the preferred embodiments of the present application. It should be pointed out that for those skilled in the art, without departing from the principles of the present application, several improvements and modifications can also be made. It should be regarded as the protection scope of this application.

Claims (10)

1. The method for determining the line protection range of the fault point of the photovoltaic station outgoing line is characterized in that the analysis method comprises the following steps:

S1: determining a measured impedance expression of the power outlet of the photovoltaic station, wherein the measured impedance expression ZM is as follows:

In the formula (1), n is a fault position coefficient, and the value of n is the percentage of the distance from the distance protection installation position to the fault point to the total length of the sending line of the photovoltaic station; the Rg is a transition resistance;

ZMN is the total impedance of the photovoltaic station outgoing line, Z sigma is the sum of each sequence impedance of the photovoltaic station, CM1 and CM0 are the positive sequence current distribution coefficient and the zero sequence current distribution coefficient of the photovoltaic station power supply respectively, Dd is a comprehensive coefficient,

in the formula (2), ZSM1 and ZSN1 respectively represent the equivalent positive sequence impedance of the outlet and inlet of the photovoltaic yard, the equivalent positive sequence impedance of the outlet of the photovoltaic yard is determined by the positive sequence voltage fault value and the positive sequence current fault value of the outlet of the photovoltaic yard, and p represents the ratio of the electromotive force amplitude of the outlet and inlet of the photovoltaic yard before the outlet line of the photovoltaic yard fails; delta represents the phase difference of the electromotive force of the power supplies at the outlet and the inlet of the photovoltaic station before the failure of the outlet line of the photovoltaic station;

s2: setting a fault position coefficient threshold value nmax and a transition resistance threshold value Rgmax;

s3: acquiring positive sequence voltage and positive sequence current fault values at the protection installation position of the photovoltaic station outgoing line, and positive sequence impedance values equivalent to the outlet and the inlet of the photovoltaic station;

S4: forming an action boundary of a curved polygon according to the values determined by the ZM expression, the nmax and the Rgmax in the S1, wherein a plane where the action boundary is located is a plane formed by the measured impedance value and the fault position coefficient being an axial coordinate;

s5: and analyzing the line protection range of the fault point of the line which is away from the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon.

2. the method according to claim 1, wherein the polygon in S4 comprises:

a curve I, wherein the curve I represents a curve formed by values of the ZM expression on the plane when the value of the transition resistance Rg is from zero to Rgmax when the fault position coefficient n is zero;

a curve II, wherein the curve II represents a curve formed by values of the transition resistance Rg on the plane according to the ZM expression when the value of the transition resistance Rg is from zero to Rgmax when the fault position coefficient is nmax;

a curve III representing a curve formed by values of the ZM expression at the plane when the fault location coefficient is from zero to nmax when the transition resistance Rg is zero;

a curve IV representing the values of the fault location coefficient at the plane from zero to nmax when the transition resistance is Rgmax, according to the ZM expression.

3. The method according to claim 2, wherein the polygon in S4 further comprises:

A curve V, wherein the curve V represents a curve formed by values of the ZM expression on the plane when the value of the transition resistance Rg is from zero to Rgmax when the fault position coefficient is 0.8;

And a curve VI, wherein the curve VI represents a curve formed by values of the ZM expression on the plane when the value of the transition resistor Rg is from zero to Rgmax when the tail end of the adjacent line outside the fault point of the photovoltaic station outgoing line fails.

4. The method according to claim 1, 2 or 3, wherein analyzing the distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon in the S5 comprises:

And the plane enclosed by the curve V, the curve IV and the curve VI is the maximum line range of the line protection range of the outgoing line of the photovoltaic station, wherein the line fault falls into the line protection range of the outgoing line of the photovoltaic station.

5. The method according to claim 1, 2 or 3, wherein the step of analyzing the distance protection of the fault point of the photovoltaic station outgoing line according to the action boundary and the plane of the curved polygon in the step S5 further comprises:

and a plane enclosed by the curve II, the curve III, the curve IV, the curve V and the curve VI, the coordinate curve and the coordinate curve is a delay action line range of the protection range of the photovoltaic station outgoing line.

6. A system for determining line protection limits for a point of failure of a photovoltaic farm outgoing line, the system comprising:

A modeling unit, configured to determine a measured impedance expression of the power outlet of the photovoltaic yard, where the measured impedance expression ZM is:

in the formula (1), n is a fault position coefficient, and the value of n is the percentage of the distance from the distance protection installation position to the fault point to the total length of the sending line of the photovoltaic station; the Rg is a transition resistance;

ZMN is the total impedance of the photovoltaic station outgoing line, Z sigma is the sum of each sequence impedance of the photovoltaic station, CM1 and CM0 are the positive sequence current distribution coefficient and the zero sequence current distribution coefficient of the photovoltaic station power supply respectively, Dd is a comprehensive coefficient,

in the formula (2), ZSM1 and ZSN1 respectively represent the equivalent positive sequence impedance of the outlet and inlet of the photovoltaic yard, the equivalent positive sequence impedance of the outlet of the photovoltaic yard is determined by the positive sequence voltage fault value and the positive sequence current fault value of the outlet of the photovoltaic yard, and p represents the ratio of the electromotive force amplitude of the outlet and inlet of the photovoltaic yard before the outlet line of the photovoltaic yard fails; delta represents the phase difference of the electromotive force of the power supplies at the outlet and the inlet of the photovoltaic station before the failure of the outlet line of the photovoltaic station;

the setting unit is used for setting a fault position coefficient threshold nmax and a transition resistance threshold Rgmax;

The acquisition unit is used for acquiring a positive sequence voltage and a positive sequence current fault value at a protection installation position of the photovoltaic station outgoing line and equivalent positive sequence impedance values of an outlet and an inlet of the photovoltaic station;

the calculating unit is used for forming an action boundary of a curved polygon according to the ZM expression in the modeling unit, the nmax and the Rgmax determined value in the setting unit, and a plane where the action boundary is located is a plane formed by the measured impedance value and the fault position coefficient by an axial coordinate;

And the analysis unit is used for analyzing the line protection range of the fault point of the sending line away from the photovoltaic station according to the action boundary and the plane of the curved polygon.

7. the system of claim 6, wherein the computing unit comprises:

The first calculating unit is used for calculating the value of the transition resistance Rg on the plane according to the ZM expression when the value of the transition resistance Rg is from zero to Rgmax when the fault position coefficient n is zero;

the second calculating unit is used for calculating the value of the transition resistance Rg on the plane according to the ZM expression when the value of the transition resistance Rg is from zero to Rgmax when the fault position coefficient is nmax;

a third calculating unit, configured to calculate a value of the fault location coefficient at the plane according to the ZM expression when the transition resistance Rg is zero and the fault location coefficient is from zero to nmax;

And a fourth calculating unit configured to calculate a value of the fault location coefficient at the plane from zero to nmax according to the ZM expression when the transition resistance is Rgmax.

8. The system of claim 6, wherein the computing unit further comprises:

A fifth calculating unit, configured to calculate a value of the transition resistance Rg at the plane according to the ZM expression when the value of the transition resistance Rg is from zero to Rgmax when the failure position coefficient is 0.8;

And the sixth calculating unit is used for calculating the value of the transition resistor Rg on the plane according to the ZM expression when the value of the transition resistor Rg is from zero to Rgmax when the tail end of the adjacent line outside the fault point of the sending-out line of the photovoltaic station fails.

9. the system of claim 6, 7 or 8, wherein the analysis unit comprises:

and the first analysis unit is used for analyzing the maximum line range of the line protection range of the outgoing line of the photovoltaic station according to the fourth calculation unit, the fifth calculation unit and the sixth calculation unit, wherein the outgoing line fault of the photovoltaic station falls into the maximum line range of the line protection range of the outgoing line of the photovoltaic station.

10. the system of claim 6, 7 or 8, wherein the analysis unit further comprises:

And the second analysis unit is used for analyzing the delay action line range of the protection range of the line sent out from the photovoltaic station according to the second calculation unit, the third calculation unit, the fourth calculation unit, the fifth calculation unit and the sixth calculation unit.