A fault ride-through control method for new energy station group considering active and reactive power collaborative support

Abstract

The application provides a new energy station group fault ride-through control method considering active and reactive power collaborative support, comprising the following steps: when a fault occurs in a station group, dividing fault branches and non-fault branches according to whether the fault station is included; constructing a post-fault station group model based on the Thevenin equivalent method, wherein the post-fault station group model comprises a first equivalent current source corresponding to a system between a fault point and a grid connection point of a fault branch, and a second equivalent current source corresponding to a system between a non-fault branch and the grid connection point; based on the post-fault station group model, obtaining first active current active support instructions and first reactive current active support instructions by using a station current limit utilization method, and controlling the station group. The method optimizes the collaborative support of active power and reactive power for the new energy station group, reduces the active power shortage of the station group during the fault under the premise of fully utilizing the controllable capacity and overcurrent capacity of each station, and ensures the safe and stable operation of the power system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system fault ride-through control, and particularly relates to a new energy station group fault ride-through control method considering active and reactive power collaborative support. BACKGROUND

[0002] The total installed capacity of a new energy large base exceeds tens of millions of kilowatts, which is jointly constituted by a new energy station group and a conventional system, and the proportion of new energy exceeds 70%. The existing fault ride-through scheme of the new energy station aims to provide voltage support, while ignoring the support demand for active power; and the controllable ability of the new energy station group is not fully utilized, and the controllable ability is not fully utilized. Therefore, when a short-circuit fault occurs, the existing fault ride-through control strategy based on voltage support will cause tens of millions of kilowatts of active power shortage in the new energy large base, and in severe cases, it will also cause a large drop in the grid frequency, and even trigger the action of the stability control system, affecting the safe and stable operation of the new energy power system. SUMMARY

[0003] The present application provides a new energy station group fault ride-through control method considering active and reactive power collaborative support for optimizing the collaborative support of active power and reactive power of a new energy station group, which reduces the active power shortage of the station group during the fault under the premise of fully utilizing the controllable ability and overcurrent ability of each station, and ensures the safe and stable operation of the power system.

[0004] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a new energy station group fault ride-through control method considering active and reactive power collaborative support, comprising the following steps: obtaining grid point electrical quantities, station group parameters and station group electrical quantities; the station group includes a plurality of station branches, and each station branch includes at least one station;

[0005] When a fault occurs in the station group, the plurality of station branches are divided into fault branches and non-fault branches according to whether the fault station is included, and the fault branch is the station branch where the fault station is located;

[0006] Based on the Thevenin equivalent method, a post-fault station group model is constructed according to the station group parameters and the station group electrical quantities, the post-fault station group model includes a first equivalent current source and a second equivalent current source, the first equivalent current source is an equivalent current source corresponding to the system between the fault point of the fault branch and the grid point, and the second equivalent current source is an equivalent current source corresponding to the system between the non-fault branch and the grid point;

[0007] obtaining a first current upper limit value, the first current upper limit value being a substation current output upper limit value; based on the post-fault substation group model, using a substation current limit utilization method, calculating a first active current active support instruction and a first reactive current active support instruction according to the first current upper limit value and the grid-connected point electrical quantity, the first active current support instruction being a substation active current support instruction, and the first reactive current support instruction being a substation reactive current support instruction;

[0008] controlling the substation group according to the first active current active support instruction and the first reactive current active support instruction.

[0009] In some embodiments, the substation group parameters include a first equivalent resistance, a first equivalent reactance, a second equivalent resistance, and a second equivalent reactance; the first equivalent resistance is an equivalent resistance between the fault branch substation and the grid-connected point, the first equivalent reactance is an equivalent reactance between the fault branch substation and the grid-connected point, the second equivalent resistance is an equivalent resistance between the non-fault branch substation and the grid-connected point, and the second equivalent reactance is an equivalent reactance between the non-fault branch substation and the grid-connected point.

[0010] The substation group electrical quantity includes a fault branch grid-connected point voltage phase angle, a non-fault branch grid-connected point voltage phase angle, a fault branch current output value, and a non-fault branch current output value.

[0011] In some embodiments, the first active current active support instruction includes a fault branch active current reference value and a non-fault branch active current reference value.

[0012] The first reactive current active support instruction includes a fault branch reactive current reference value and a non-fault branch reactive current reference value.

[0013] In some embodiments, based on the Thevenin equivalent method, the step of constructing the post-fault substation group model according to the substation group parameters and the substation group electrical quantity is:

[0014] obtaining the number of substations before the fault point in the fault branch and the number of substations in the non-fault branch;

[0015] constructing a first current output expression according to the number of substations before the fault point in the fault branch and the grid-connected point voltage phase angle of the fault branch, the first current output expression being a current output expression of the first equivalent current source; the first current output expression being an expression about the fault branch active current reference value and the fault branch reactive current reference value;

[0016] constructing a first equivalent impedance expression according to the number of substations in the fault branch, the first equivalent resistance, the first equivalent reactance, the fault branch current output value and the first current output expression, the first equivalent impedance being an equivalent impedance between the first equivalent current source and the point of common coupling;

[0017] constructing a second current output expression according to the number of substations in the non-fault branch and the phase angle of the voltage at the point of common coupling of the non-fault branch, the second current output expression being a current output expression of the second equivalent current source; the second current output expression being an expression about active current reference values and reactive current reference values of the non-fault branch;

[0018] constructing a second equivalent impedance expression according to the number of substations in the non-fault branch, the second equivalent resistance, the second equivalent reactance, the non-fault branch current output value and the second current output expression, the second equivalent impedance being an equivalent impedance between the second equivalent current source and the point of common coupling.

[0019] In some embodiments, when the fault point position is known: obtaining fault point parameters and substation group bus parameters;

[0020] constructing a total active power expression according to the fault point parameters, the substation group bus parameters and the electrical quantities at the point of common coupling based on the post-fault substation group model;

[0021] obtaining a second current upper limit value and a third current upper limit value, the second current upper limit value being a current output upper limit value of the first equivalent current source, and the third current upper limit value being a current output upper limit value of the second equivalent current source;

[0022] obtaining a second active current active support instruction and a second reactive current active support instruction according to the second current upper limit value, the third current upper limit value and the total active power expression by using a substation current limit utilization method based on the post-fault substation group model, the second active current active support instruction being an active current active support instruction of the post-fault substation group model, and the second reactive current active support instruction being a reactive current active support instruction of the post-fault substation group model;

[0023] controlling the substation group according to the second active current active support instruction and the second reactive current active support instruction.

[0024] In some embodiments, the second active current active support instruction includes a first equivalent current source active current active support instruction and a second equivalent current source active current active support instruction;

[0025] The second reactive current active support instruction comprises a first equivalent current source reactive current active support instruction and a second equivalent current source reactive current active support instruction.

[0026] In some embodiments, the station group bus parameters comprise a third equivalent impedance, the third equivalent impedance being an impedance between the station group bus and the point of common coupling;

[0027] The fault point parameters comprise a fourth equivalent impedance, the fourth equivalent impedance being an impedance between the first equivalent current source and the fault point;

[0028] The point of common coupling electrical quantity comprises a point of common coupling grid voltage and a point of common coupling grid voltage phase angle.

[0029] In some embodiments, based on the post-fault station group model, the step of constructing a total active power expression according to the fault point parameters, the station group bus parameters and the point of common coupling electrical quantity is:

[0030] Based on the post-fault station group model and the superposition theorem, a first voltage expression and a second voltage expression are respectively constructed according to the third equivalent impedance, the fourth equivalent impedance and the point of common coupling grid voltage; the first voltage is a first equivalent current source point of common coupling voltage; the second voltage is a second equivalent current source point of common coupling voltage;

[0031] A first active power expression is constructed according to the first voltage expression and the first current output expression, the first active power being an active power of the first equivalent current source;

[0032] A second active power expression is constructed according to the second voltage expression and the second current output expression, the second active power being an active power of the second equivalent current source;

[0033] The total active power expression is constructed according to the first active power expression and the second active power expression.

[0034] In some embodiments, the step of determining that the station group is faulty is:

[0035] A reference voltage and a station point of common coupling voltage are obtained;

[0036] When the station point of common coupling voltage is less than the reference voltage, the corresponding station is a faulty station, and the station branch where the faulty station is located is a faulty branch;

[0037] When the station group comprises at least one faulty station, the station group is faulty.

[0038] In some embodiments, the reference voltage is 0.9 p.u., and p.u. is a per unit value.

[0039] Compared with the prior art, the application has the following beneficial effects:

[0040] The fault ride-through control method provided by the application optimizes the coordinated support of active power and reactive power of the new energy station group, reduces the active power shortage of the station group during the fault under the premise of fully utilizing the controllable capacity and overcurrent capacity of each station, and ensures the safe and stable operation of the power system. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The flowchart of the new energy station group fault ride-through control method considering active and reactive power coordinated support in the application;

[0042] Figure 2 The system structure diagram of the new energy station group in the example of the application;

[0043] Figure 3 The simplified system structure diagram of the new energy station group in the example of the application;

[0044] Figure 4 The active power-reactive power simulation curve diagram obtained by using different methods for fault ride-through control in the example of the application: (a) is the conventional current reference value method, and (b) is the new energy station group fault ride-through control method considering active and reactive power coordinated support provided by the application. DETAILED DESCRIPTION

[0045] To clearly illustrate the technical features of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings and examples, so that the implementation process of how the present application applies technical means to solve technical problems and achieves the corresponding technical effects can be fully understood and implemented. The embodiments of the present application and each feature in the examples can be combined with each other without conflict, and the formed technical solutions are all within the protection scope of the present application.

[0046] Referring to Figure 1 , the embodiment of the present application provides a new energy station group fault ride-through control method considering active and reactive power coordinated support, including the following steps: obtaining grid-connected point electrical quantities, station group parameters and station group electrical quantities; the station group includes a plurality of station branches, and each station branch includes at least one station; the station group parameters include a first equivalent resistance R f-k , a first equivalent reactance X f-k , a second equivalent resistance R nf-i and a second equivalent reactance X nf-i ; the first equivalent resistance R f-k is the equivalent resistance between the fault branch station and the grid-connected point, i.e. R f-krepresents the equivalent resistance between the kth station of the fault branch and the point of common coupling, k is the sequence number of the fault station in the fault branch, the first equivalent reactance X f-k is the equivalent reactance between the fault station and the point of common coupling, i.e. X f-k represents the equivalent reactance between the kth station of the fault branch and the point of common coupling, the second equivalent resistance R nf-i is the equivalent resistance between the non-fault station and the point of common coupling, i.e. R nf-i represents the equivalent resistance between the ith station of the non-fault branch and the point of common coupling, i is the sequence number of the non-fault station in the non-fault branch, the second equivalent reactance X nf-i is the equivalent reactance between the non-fault station and the point of common coupling, i.e. X nf-i represents the equivalent reactance between the ith station of the non-fault branch and the point of common coupling;

[0047] When the station group fails, a number of station branches are divided into fault branches and non-fault branches according to whether they contain fault stations, and the fault branch is the station branch where the fault station is located;

[0048] Based on the Thevenin equivalent method, a post-fault station group model is constructed according to the station group parameters and the station group electrical quantities, and the station group electrical quantities include the fault branch point of common coupling voltage phase angle δ f-k , the non-fault branch point of common coupling voltage phase angle δ nf-i , the fault branch current output value and the non-fault branch current output value i.e. δ f-k represents the fault branch kth station point of common coupling voltage phase angle, δ nf-i represents the non-fault branch ith station point of common coupling voltage phase angle, represents the fault branch kth station current output value, represents the non-fault branch ith station current output value, the post-fault station group model includes a first equivalent current source and a second equivalent current source, the first equivalent current source is an equivalent current source corresponding to the system between the fault point of the fault branch and the point of common coupling, and the second equivalent current source is an equivalent current source corresponding to the system between the non-fault branch and the point of common coupling; see Figure 2 When a three-phase short-circuit fault occurs in at least one station branch in the station group, the other station branches that do not fail are regarded as non-fault branches. Due to the existence of the fault point, the station between the fault point and the end of the fault branch cannot transmit power to the power grid; therefore, when the station group fails, the classification method of the fault system (the system between the fault point of the fault branch and the point of common coupling) and the non-fault system (the system between the non-fault branch and the point of common coupling) is used for simplification;

[0049] Due to the current-carrying capability limit of semiconductor devices in the converter equipment in the station, the main factor limiting the output of the station when a fault occurs is the current amplitude constraint. At the same time, in order to realize the rapid fault response of the station and avoid overcurrent, the converter in the station switches to the current loop low-voltage ride-through link to directly control the current, therefore, according to the classification of fault system and non-fault system, the new energy station group in the large base can be approximately regarded as two current sources, i.e., a first equivalent current source and a second equivalent current source, as shown in the figure. Figure 3

[0050] Based on the Thevenin equivalent method, the steps for constructing the post-fault station group model according to the station group parameters and the station group electrical quantities are as follows:

[0051] Obtain the number n of stations before the fault point in the fault branch and the number m of stations in the non-fault branch;

[0052] According to the number n of stations before the fault point in the fault branch and the voltage phase angle δ of the grid connection point of the fault branch f-k Construct a first current output expression, which is the current output expression of the first equivalent current source; the first current output expression is an expression about the active current reference value of the fault branch and the reactive current reference value of the fault branch;

[0053]

[0054] In the formula, is the current output value of the first equivalent current source, I d_f-k_ref is the active current reference value of the kth station in the fault branch, I q_f-k_ref is the reactive current reference value of the kth station in the fault branch;

[0055] According to the number n of stations before the fault point in the fault branch, the first equivalent resistance R f-k , the first equivalent reactance X f-k , the current output value I of the fault branch and the first current output expression, construct a first equivalent impedance expression, and the first equivalent impedance Z f is the equivalent impedance between the first equivalent current source and the grid connection point;

[0056]

[0057] In the formula, Z f is the first equivalent impedance, R f is the equivalent resistance between the first equivalent current source and the grid connection point, and X f is the equivalent reactance between the first equivalent current source and the grid connection point;

[0058] According to the number m of stations in the non-fault branch and the voltage phase angle δ nf-i ​constructing a second current output expression, the second current output expression being a current output expression of the second equivalent current source; the second current output expression being an expression about the non-fault branch active current reference value and the non-fault branch reactive current reference value;

[0059]

[0060] in the formula, is a current output value of the second equivalent current source, I d_nf-i_ref is the non-fault branch i th station active current reference value, I q_nf-i_ref is the non-fault branch i th station reactive current reference value;

[0061] According to the number of stations m in the non-fault branch, the second equivalent resistance R nf-i , the second equivalent reactance X nf-i , the non-fault branch current output value and the second current output expression, the second equivalent impedance expression is constructed, and the second equivalent impedance Z nf is the equivalent impedance between the second equivalent current source and the grid connection point:

[0062]

[0063] in the formula, Z nf is the second equivalent impedance, R nf is the equivalent resistance between the second equivalent current source and the grid connection point, X nf is the equivalent reactance between the second equivalent current source and the grid connection point.

[0064] obtaining a first current upper limit value, the first current upper limit value being a station current output upper limit value; the station current output value includes the fault branch station current output value and the non-fault branch station current output value, for the fault branch, the first current upper limit value is I f-k_lim , that is, I f-k_lim represents the fault branch k th station current output upper limit value, for the non-fault branch, the first current upper limit value is I nf-i_lim , that is, I nf-i_lim represents the non-fault branch i th station current output upper limit value;

[0065] Based on the post-fault station group model, the station current limit utilization method is adopted, and the first active current active support instruction and the first reactive current active support instruction are calculated according to the first current upper limit value and the grid connection point electrical quantity, the first active current support instruction being a station active current support instruction, and the first reactive current support instruction being a station reactive current support instruction; the first active current active support instruction includes the fault branch active current reference value I d_f-k_ref and the non-fault branch active current reference value I d_nf-i_ref , that is, Id_f-k_ref I represents the reference value of the active current of the kth substation in the faulty branch. d_nf-i_ref This represents the active current reference value of the i-th substation in the non-faulty branch; the first reactive current active power support command includes the reactive current reference value I of the faulty branch. q_f-k_ref Reference value of reactive current I for non-faulty branches q_nf-i_ref , that is I q_f-k_ref I represents the reference value of reactive current at the kth substation in the faulty branch. q_nf-i_ref This represents the reference value of reactive current for the i-th station in the non-faulty branch.

[0066] To expedite response time and avoid fault location identification, the current output amplitude of each substation can be continuously maintained at its upper limit. Simultaneously, the control master station monitors the grid voltage phase angle δ at the grid connection point via devices such as PMUs. grid And the grid voltage phase angle δ at the grid connection point grid The data is sent to each power station, which then uses the grid voltage phase angle δ at the grid connection point obtained through communication. grid It can calculate the first active current active support command and the first reactive current active support command, realize active-reactive coordinated support control during fault ride-through, and effectively reduce the amount of communication data.

[0067] The electrical quantities at the grid connection point include the grid voltage U at the grid connection point. grid Phase angle δ of the grid voltage at the grid connection point grid Based on the grid voltage U at the grid connection point grid Phase angle δ of the grid voltage at the grid connection point grid The expression for total active power is:

[0068]

[0069] In the formula, P ∑ Z represents the total active power, i.e., the total active power output of the substation group after a fault. grid Z is the impedance between the station group bus and the grid connection point. gnd Let δ be the impedance between the first equivalent current source and the fault point. The Re(·) function represents finding the real part, and the (·)* function represents finding the conjugate. f δ is the phase angle of the grid-connected voltage of the first equivalent current source. nf The phase angle of the grid-connected voltage of the second equivalent current source;

[0070] Since the impedance values ​​of each station group remain constant after a fault occurs, the voltage phase angle δ at the grid connection point of the first equivalent current source is maintained if and only if... f The phase angle δ of the grid-connected voltage of the second equivalent current source nf The phase angle δ with the grid voltage at the connection point respectively gridWhen the equivalent value of the station current output is the first current upper limit value (the current amplitude reaches the sum of the current upper limits of each station in the station group), the active power output of the station group reaches the maximum value:

[0071]

[0072] In the formula, P ∑max is the total active power maximum value, that is, the total active power output maximum value of the station group, I f_lim is the current upper limit value of the first equivalent current source, I nf_lim is the current upper limit value of the second equivalent current source;

[0073] The first active current active support instruction and the first reactive current active support instruction satisfy:

[0074]

[0075] The first active current active support instruction and the first reactive current active support instruction are calculated as follows:

[0076] I d_f-k_ref = I f-k_lim cosδ grid ;

[0077] I q_f-k_ref = I f-k_lim sinδ grid ;

[0078] I d_nf-i_ref = I nf-i_lim cosδ grid ;

[0079] I q_nf-i_ref = I nf-i_lim sinδ grid ;

[0080] The station group is controlled according to the first active current active support instruction and the first reactive current active support instruction.

[0081] In some embodiments, when the fault point position is known: the fault point parameters and the station group bus parameters are obtained; the station group bus parameters include a third equivalent impedance, the third equivalent impedance being the impedance Z grid between the station group bus and the grid connection point; the fault point parameters include a fourth equivalent impedance, the fourth equivalent impedance being the impedance Z gnd between the first equivalent current source and the fault point;

[0082] Based on the post-fault station group model, the total active power expression is constructed according to the fault point parameters, the station group bus parameters and the electrical quantity of the grid connection point, and the specific steps are as follows:

[0083] The first voltage expression and the second voltage expression are respectively constructed according to the third equivalent impedance, the fourth equivalent impedance and the grid voltage at the grid connection point based on the post-fault station group model and the superposition theorem; the first voltage is the grid voltage at the grid connection point of the first equivalent current source; and the second voltage is the grid voltage at the grid connection point of the second equivalent current source.

[0084]

[0085] In the formula, the first voltage is the second voltage is

[0086] The resistance of the collection line between the new energy station groups and the active power loss caused by the resistance are ignored.

[0087] The first active power expression is constructed according to the first voltage expression and the first current output expression under the symmetrical short-circuit fault, and the first active power is the active power P f of the first equivalent current source.

[0088]

[0089] The second active power expression is constructed according to the second voltage expression and the second current output expression under the symmetrical short-circuit fault, and the second active power is the active power P nf of the second equivalent current source.

[0090]

[0091] The total active power expression is constructed according to the first active power expression and the second active power expression.

[0092]

[0093] The second current upper limit value and the third current upper limit value are obtained, the second current upper limit value is the current output upper limit value I f_lim of the first equivalent current source, and the third current upper limit value is the current output upper limit value I nf_lim of the second equivalent current source.

[0094] The second active current active support instruction and the second reactive current active support instruction are calculated according to the second current upper limit value, the third current upper limit value and the total active power expression based on the post-fault station group model and by using the station current limit utilization method; the second active current active support instruction is the active current active support instruction of the post-fault station group model, and the second reactive current active support instruction is the reactive current active support instruction of the post-fault station group model; the second active current active support instruction includes the first equivalent current source active current active support instruction I f_d_ref and the second equivalent current source active current active support instruction I nf_d_ref; the second reactive current active support instruction includes a first equivalent current source reactive current active support instruction I f_q_ref and a second equivalent current source reactive current active support instruction I nf_q_ref .

[0095] To achieve the best utilization of the station current, each station current should be output according to the maximum current value, that is, the current output value of the first equivalent current source and the current output value of the second equivalent current source satisfy:

[0096]

[0097] In the formula, I f_d is the active current of the fault branch, I f_q is the reactive current of the fault branch, I nf_d is the active current of the non-fault branch, and I nf_q is the reactive current of the non-fault branch.

[0098] As can be seen from the total active power expression, the grid-connected point voltage phase angle δ f of the first equivalent current source and the grid-connected point voltage phase angle δ nf of the second equivalent current source are respectively equal to the grid-connected point grid voltage phase angle δ grid , and the station current is output to the limit, the total active power output of the station group reaches the maximum value:

[0099]

[0100] Therefore, when the total active power output of the station group reaches the maximum value, the grid-connected point voltage phase angle δ f of the first equivalent current source and the grid-connected point voltage phase angle δ nf of the second equivalent current source are respectively equal to the grid-connected point grid voltage phase angle δ grid , and the station current amplitude takes the upper limit value, at this time, the fault branch complex power S f of the station group and the non-fault branch complex power S nf are respectively:

[0101]

[0102]

[0103] Based on the fault branch complex power S f of the station group, the non-fault branch complex power S nf , and the grid-connected point grid voltage U grid , the second active current active support instruction and the second reactive current active support instruction are respectively obtained, that is, the first equivalent current source active current active support instruction I f_d_ref and the first equivalent current source reactive current active support instruction I f_q_ref, second equivalent current source active current active support instruction I nf_d_ref and second equivalent current source reactive current active support instruction I nf_q_ref :

[0104]

[0105] In the formula, the Im(·) function represents the imaginary part.

[0106] The power plant group is controlled according to the second active current active support instruction and the second reactive current active support instruction.

[0107] In some embodiments, the step of determining that the power plant group is faulty is:

[0108] The reference voltage U * and the power plant point of interconnection voltage U l , preferably the reference voltage U * is 0.9 p.u., p.u. is the per unit value, and when the power plant group is not faulty, the power plants in the power plant group are not distinguished between faulty branches and non-faulty branches, i.e. U l represents the power plant point of interconnection voltage of the lth power plant in the power plant group, and l is the serial number of the power plant in the power plant group;

[0109] When the power plant point of interconnection voltage U l is less than the reference voltage U * , the corresponding power plant is a faulty power plant, i.e. the lth power plant in the power plant group is a faulty power plant, and the power plant branch in which the faulty power plant is located is a faulty branch.

[0110] When the power plant group includes at least one faulty power plant, the power plant group is faulty.

[0111] The implementation process and effects of the new energy power plant group fault ride-through control method considering active and reactive power collaborative support disclosed in the present disclosure are described in detail below with a specific example.

[0112] A new energy power plant group simulation model is built in this example, and the new energy power supply parameters in the simulation model are shown in Table 1:

[0113] Table I New energy power supply parameters

[0114] Parameter name Value Rated power per station PN / MW 500 Rated line voltage UN / kV 220 Line unit reactance X / (Ω / km). 0.238 Average line length l / km 50 Station current upper limit I / kA. 1.3 Number of stations in the station group 20

[0115] The new energy power plant group outputs at the rated power before the power plant group fault occurs, and the power plant group fault occurs at 0.1s, and the fault type is three-phase ground short circuit. The active power and reactive power simulation results of the new energy power plant group under the fault ride-through control after the power plant group fault are shown in Table 2. Figure 4

[0116] Figure 4 ​​It can be seen that, compared with the control response specified in the existing fault ride-through national standard GB / T 19963.1, the active power output of the new energy station group under the proposed fault ride-through control is increased by 54%, and the reactive power output is increased by 24%, effectively alleviating the impact on the safe and stable operation of the new energy power system during the fault of the station group.

[0117] In summary, the present disclosure can optimize the active support calculation for the new energy station group, improve the active power support capability of the station group during the fault under the premise of fully utilizing the controllable capacity and overcurrent capacity of each station, and ensure the safe and stable operation of the power system.

[0118] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support, characterized in that: Includes the following steps: Obtain the electrical quantities at the grid connection point, the parameters of the power station group, and the electrical quantities of the power station group; the power station group includes several power station branches, and each power station branch includes at least one power station; When a fault occurs in the station group, the several station branches are divided into faulty branches and non-faulty branches according to whether they contain faulty stations. The faulty branch is the station branch where the faulty station is located. Based on the Thevenin equivalent method, a post-fault substation group model is constructed according to the substation group parameters and the substation group electrical quantities. The post-fault substation group model includes a first equivalent current source and a second equivalent current source. The first equivalent current source is the equivalent current source corresponding to the system between the fault point of the fault branch and the grid connection point, and the second equivalent current source is the equivalent current source corresponding to the system between the non-fault branch and the grid connection point. Obtain the first current upper limit value, where the first current upper limit value is the station current output upper limit value; Based on the post-fault substation group model, the substation current utilization method is adopted. The first active current support command and the first reactive current support command are calculated according to the first current upper limit value and the electrical quantity of the grid connection point. The first active current support command is the substation active current support command, and the first reactive current support command is the substation reactive current support command. The power station group is controlled according to the first active current active support command and the first reactive current active support command. When the total active power output of the power station group reaches the maximum value, the voltage phase angle of the grid connection point of the first equivalent current source and the voltage phase angle of the grid connection point of the second equivalent current source are equal to the voltage phase angle of the grid connection point, and the current amplitude of the power station is taken as the upper limit value. At this time, the fault branch complex power and the non-fault branch complex power of the power station group are calculated. Based on the calculation of the fault branch power and non-fault branch power of the power station group and the grid voltage at the grid connection point, the second active current active support command and the second reactive current active support command are obtained respectively, that is, the first equivalent current source active current support command, the first equivalent current source reactive current support command, the second equivalent current source active current support command and the second equivalent current source reactive current support command are obtained. The power station group is controlled according to the second active current active support command and the second reactive current active support command.

2. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 1, characterized in that: The parameters of the power station group include a first equivalent resistance, a first equivalent reactance, a second equivalent resistance, and a second equivalent reactance; the first equivalent resistance is the equivalent resistance between the faulty branch power station and the grid connection point, the first equivalent reactance is the equivalent reactance between the faulty branch power station and the grid connection point, the second equivalent resistance is the equivalent resistance between the non-faulty branch power station and the grid connection point, and the second equivalent reactance is the equivalent reactance between the non-faulty branch power station and the grid connection point; The electrical quantities of the station group include the phase angle of the grid connection voltage of the faulty branch, the phase angle of the grid connection voltage of the non-faulty branch, the current output value of the faulty branch, and the current output value of the non-faulty branch.

3. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 2, characterized in that: The first active current support command includes the active current reference value of the faulty branch and the active current reference value of the non-faulty branch. The first reactive current active power support command includes the reactive current reference value of the faulty branch and the reactive current reference value of the non-faulty branch.

4. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 2, characterized in that: Based on the Thevenin equivalent method, the steps for constructing the post-fault substation group model according to the substation group parameters and the substation group electrical quantities are as follows: Obtain the number of field stations before the fault point in the faulty branch and the number of field stations in the non-faulty branch; A first current output expression is constructed based on the number of field stations in front of the fault point in the fault branch and the voltage phase angle of the grid connection point of the fault branch. The first current output expression is the current output expression of the first equivalent current source. The first current output expression is an expression relating the active current reference value and the reactive current reference value of the faulty branch; The first equivalent impedance expression is constructed based on the number of field stations in front of the fault point in the fault branch, the first equivalent resistance, the first equivalent reactance, the current output value of the fault branch, and the first current output expression. The first equivalent impedance is the equivalent impedance between the first equivalent current source and the grid connection point. A second current output expression is constructed based on the number of field stations in the non-faulty branch and the voltage phase angle at the grid connection point of the non-faulty branch. The second current output expression is the current output expression of the second equivalent current source. The second current output expression is an expression relating the active current reference value and the reactive current reference value of the non-faulty branch. The second equivalent impedance expression is constructed based on the number of field stations in the non-faulty branch, the second equivalent resistance, the second equivalent reactance, the current output value of the non-faulty branch, and the second current output expression. The second equivalent impedance is the equivalent impedance between the second equivalent current source and the grid connection point.

5. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 4, characterized in that: When the location of the fault is known: obtain the fault point parameters and the parameters of the station group bus; Based on the post-fault substation group model, a total active power expression is constructed according to the fault point parameters, the substation group bus parameters, and the grid connection point electrical quantities. Obtain a second current upper limit value and a third current upper limit value, wherein the second current upper limit value is the current output upper limit value of the first equivalent current source, and the third current upper limit value is the current output upper limit value of the second equivalent current source; Based on the post-fault substation group model, the substation current utilization method is adopted. According to the second current upper limit value, the third current upper limit value and the total active power expression, the second active current support command and the second reactive current support command are calculated. The second active current support command is the active current support command of the post-fault substation group model, and the second reactive current support command is the reactive current support command of the post-fault substation group model. The power station group is controlled according to the second active current active support command and the second reactive current active support command.

6. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 5, characterized in that: The second active current support command includes the first equivalent current source active current support command and the second equivalent current source active current support command. The second reactive current active power support command includes the first equivalent current source reactive current active power support command and the second equivalent current source reactive current active power support command.

7. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 6, characterized in that: The parameters of the station group bus include a third equivalent impedance, which is the impedance between the station group bus and the grid connection point. The fault point parameters include a fourth equivalent impedance, which is the impedance between the first equivalent current source and the fault point. The electrical quantities at the grid connection point include the grid voltage at the grid connection point and the phase angle of the grid voltage at the grid connection point.

8. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 7, characterized in that: Based on the post-fault substation group model, the steps for constructing the total active power expression according to the fault point parameters, the substation group bus parameters, and the grid connection point electrical quantities are as follows: Based on the post-fault substation group model and the superposition theorem, a first voltage expression and a second voltage expression are constructed according to the third equivalent impedance, the fourth equivalent impedance, and the grid voltage at the grid connection point, respectively; the first voltage is the grid connection voltage of the first equivalent current source; the second voltage is the grid connection voltage of the second equivalent current source. A first active power expression is constructed based on the first voltage expression and the first current output expression, wherein the first active power is the active power of the first equivalent current source. A second active power expression is constructed based on the second voltage expression and the second current output expression. The second active power is the active power of the second equivalent current source. The total active power expression is constructed based on the first active power expression and the second active power expression.

9. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 1, characterized in that: The steps to determine if the aforementioned station group has experienced a malfunction are as follows: Obtain the reference voltage and the voltage at the power station's grid connection point; When the voltage at the grid connection point of the power station is less than the reference voltage, the corresponding power station is a faulty power station, and the branch of the power station where the faulty power station is located is a faulty branch. The fault occurs when the station group includes at least one of the faulty stations.

10. The fault ride-through control method for new energy power station clusters considering active and reactive power coordinated support according to claim 9, characterized in that: The reference voltage is 0.9 pu, where pu is a per-unit value.

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