New energy field station group fault ride-through control method considering active and reactive cooperative support

Abstract

The invention provides a new energy field station group fault ride-through control method considering active and reactive cooperative support, and the method comprises the following steps: dividing a fault branch and a non-fault branch according to whether a fault field station is included or not when a fault occurs in a field station group; constructing a post-fault station group model based on a Thevenin equivalent method, wherein the post-fault station group model comprises a first equivalent current source corresponding to a system between a fault point of a fault branch and a grid-connected point, and a second equivalent current source corresponding to a system between a non-fault branch and the grid-connected point; and based on the post-fault station group model, obtaining a first active current active support instruction and a first reactive current active support instruction by adopting a station current limit utilization method, and controlling the station group. According to the method, cooperative support optimization calculation of active power and reactive power is carried out on a new energy station group, the active power vacancy of the station group during a fault period is reduced on the premise of fully utilizing the controllable capability and the over-current capability of each station, and safe and stable operation of a power system is ensured.

Description

Technical Field

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

[0002] The total installed capacity of large new energy bases exceeds tens of millions of kilowatts, which is jointly composed of a new energy power station group and a conventional system, and the proportion of new energy exceeds 70%. The existing fault ride-through solutions for new energy power stations aim to provide voltage support while ignoring the support demand for active power; moreover, the controllable capabilities of the new energy power station group are not fully utilized, and the controllable capabilities cannot be utilized to the limit. Therefore, when a short-circuit fault occurs, the existing fault ride-through control strategy based on voltage support will result in an active power deficit of tens of millions of kilowatts in the large new energy base, and in severe cases, it will even cause a significant drop in the power 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 of the Invention

[0003] Aiming at the problems existing in the prior art, the present invention provides a fault ride-through control method for a new energy power station group considering active and reactive power collaborative support, which optimizes the collaborative support of active power and reactive power for the new energy power station group. On the premise of fully utilizing the controllable capabilities and over-current capabilities of each power station, this fault ride-through control method reduces the active power deficit of the power station group during the fault and ensures the safe and stable operation of the power system.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows: A fault ride-through control method for a new energy power station group considering active and reactive power collaborative support, comprising the following steps: acquiring 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 a plurality of power station branches, and each power station branch includes at least one power station;

[0005] When a fault occurs in the power station group, divide the plurality of power station branches into fault branches and non-fault branches according to whether they include a fault power station, and the fault branch is the power station branch where the fault power station is located;

[0006] Based on the Thevenin equivalent method, construct a post-fault power station group model according to the parameters of the power station group and the electrical quantities of the power station group. The post-fault power station 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;

[0007] Obtain a first current upper limit value, where the first current upper limit value is the upper limit value of the substation current output; based on the post-fault substation group model, adopt a method for making full use of the substation current, and calculate 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 connection point electrical quantities. The first active current support instruction is the substation active current support instruction, and the first reactive current support instruction is the substation reactive current support instruction;

[0008] Control 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 the equivalent resistance between the substation of the fault branch and the grid connection point, the first equivalent reactance is the equivalent reactance between the substation of the fault branch and the grid connection point, the second equivalent resistance is the equivalent resistance between the substation of the non-fault branch and the grid connection point, and the second equivalent reactance is the equivalent reactance between the substation of the non-fault branch and the grid connection point;

[0010] The substation group electrical quantities include the voltage phase angle of the grid connection point of the fault branch, the voltage phase angle of the grid connection point of the non-fault branch, the current output value of the fault branch, and the current output value of the non-fault branch.

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

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

[0013] In some embodiments, based on the Thevenin equivalent method, the steps of constructing the post-fault substation group model according to the substation group parameters and the substation group electrical quantities are as follows:

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

[0015] Construct a first current output expression according to the number of substations before 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 about the reference value of the active current of the fault branch and the reference value of the reactive current of the fault branch;

[0016] Construct a first equivalent impedance expression based on the number of front - end stations 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;

[0017] Construct a second current output expression based on the number of stations in the non - fault branch and the voltage phase angle of the grid connection point of the non - fault 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 regarding the reference value of the active current of the non - fault branch and the reference value of the reactive current of the non - fault branch;

[0018] Construct a second equivalent impedance expression based on the number of stations in the non - fault branch, the second equivalent resistance, the second equivalent reactance, the current output value of the non - fault 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.

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

[0020] Based on the post - fault substation group model, construct a total active power expression according to the fault point parameters, the bus parameters of the substation group, and the electrical quantities of the grid connection point;

[0021] Obtain a second current upper limit value and a third current upper limit value. 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;

[0022] Based on the post - fault substation group model, adopt the method of making full use of the station current limit, and calculate the second active current active support instruction and the 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. The second active current active support instruction is the active current active support instruction of the post - fault substation group model, and the second reactive current active support instruction is the reactive current active support instruction of the post - fault substation group model;

[0023] Control 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 the active current active support instruction of the first equivalent current source and the active current active support instruction of the second equivalent current source;

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

[0026] In some embodiments, the substation cluster bus parameters include a third equivalent impedance, which is the impedance between the substation cluster bus and the grid connection point;

[0027] The fault point parameters include a fourth equivalent impedance, which is the impedance between the first equivalent current source and the fault point;

[0028] 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.

[0029] In some embodiments, the steps of constructing the total active power expression based on the post-fault substation cluster model according to the fault point parameters, the substation cluster bus parameters, and the electrical quantities at the grid connection point are as follows:

[0030] Based on the post-fault substation cluster 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 grid voltage at the grid connection point; the first voltage is the grid connection point voltage of the first equivalent current source; the second voltage is the grid connection point voltage of the second equivalent current source;

[0031] A first active power expression is constructed according to the first voltage expression and the first current output expression, and the first active power is the 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, and the second active power is the 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 steps of determining that a fault has occurred in the substation cluster are as follows:

[0035] Obtain the reference voltage and the grid connection point voltage of the substation;

[0036] When the grid connection point voltage of the substation is less than the reference voltage, the corresponding substation is a faulty substation, and the substation branch where the faulty substation is located is a faulty branch;

[0037] When the substation cluster includes at least one of the faulty substations, a fault has occurred in the substation cluster.

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

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

[0040] The fault ride-through control method proposed by the present invention performs collaborative support optimization calculation of active power and reactive power for a new energy power station group. On the premise of making full use of the controllable capacity and over-current capacity of each power station, it reduces the active power deficit of the power station group during the fault period and ensures the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flowchart of the fault ride-through control method for a new energy power station group considering active and reactive power collaborative support in the present invention;

[0042] Figure 2 is a system structure diagram of the new energy power station group in the calculation example of the present invention;

[0043] Figure 3 is a simplified system structure diagram of the new energy power station group in the calculation example of the present invention;

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

[0045] To clearly illustrate the technical features of the present solution, the following will combine the drawings and embodiments to detail the implementation manner of the present application, so as to fully understand how the present application uses technical means to solve technical problems and achieve the corresponding technical effects and implement them accordingly. Each feature in the embodiments of the present application and the embodiments can be combined with each other without conflict, and the formed technical solutions are all within the protection scope of the present application.

[0046] See Figure 1 , an embodiment of the present invention provides a fault ride-through control method for a new energy power station group considering active and reactive power collaborative support, including the following steps: obtaining 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; the parameters of the power station group include the first equivalent resistance R f-k , the first equivalent reactance X f-k , the second equivalent resistance R nf-i , and the second equivalent reactance X nf-i ; the first equivalent resistance R f-k is the equivalent resistance between the power station of the fault branch and the grid connection point, that is, R f-kDenote the equivalent resistance between the k-th substation of the faulty branch and the grid connection point, where k is the serial number of the faulty substation in the faulty branch, and the first equivalent reactance X f-k is the equivalent reactance between the substation of the faulty branch and the grid connection point, that is, X f-k Denote the equivalent reactance between the k-th substation of the faulty branch and the grid connection point, and the second equivalent resistance R nf-i is the equivalent resistance between the substation of the non-faulty branch and the grid connection point, that is, R nf-i Denote the equivalent resistance between the i-th substation of the non-faulty branch and the grid connection point, where i is the serial number of the non-faulty substation in the non-faulty branch, and the second equivalent reactance X nf-i is the equivalent reactance between the substation of the non-faulty branch and the grid connection point, that is, X nf-i Denote the equivalent reactance between the i-th substation of the non-faulty branch and the grid connection point;

[0047] When a fault occurs in the substation group, several substation branches are divided into faulty branches and non-faulty branches according to whether they contain faulty substations. The faulty branches are the substation branches where the faulty substations are located;

[0048] Based on the Thevenin equivalent method, construct a post-fault substation group model according to the substation group parameters and substation group electrical quantities. The substation group electrical quantities include the voltage phase angle δ of the grid connection point of the faulty branch f-k , the voltage phase angle δ of the grid connection point of the non-faulty branch nf-i , the current output value of the faulty branch and the current output value of the non-faulty branch That is, δ f-k Denote the voltage phase angle of the grid connection point of the k-th substation of the faulty branch, and δ nf-i Denote the voltage phase angle of the grid connection point of the i-th substation of the non-faulty branch, Denote the current output value of the k-th substation of the faulty branch, Denote the current output value of the i-th substation of the non-faulty branch. 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 and the grid connection point of the faulty branch, and the second equivalent current source is the equivalent current source corresponding to the system between the non-faulty branch and the grid connection point; see Figure 2 , when a three-phase short-circuit fault occurs in at least one substation branch in the substation group, the other non-faulty substation branches are regarded as non-faulty branches. Due to the existence of the fault point, the substations between the fault point and the end of the faulty branch cannot transmit electrical energy to the power grid; therefore, when a fault occurs in the substation group, it is simplified according to the classification method of the fault system (the system between the fault point and the grid connection point of the faulty branch) and the non-fault system (the system between the non-faulty branch and the grid connection point);

[0049] Due to the limitation of the overcurrent capacity of semiconductor devices in the converter equipment at the substation, the main factor restricting the output of the substation during a fault is the current amplitude constraint. At the same time, in order to achieve a fast fault response of the substation and avoid overcurrent, the converter in the substation switches to the low-voltage ride-through link of the current loop to directly control the current. Therefore, classified according to the fault system and the non-fault system, the new energy substation group in the large base can be approximately regarded as composed of Figure 3 the two current sources shown, namely the first equivalent current source and the second equivalent current source.

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

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

[0052] According to the number n of substations in front of the fault point in the fault branch and the voltage phase angle δ f-k Construct the first current output expression, and the first current output expression 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 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 substation in the fault branch, I q_f-k_ref is the reactive current reference value of the kth substation in the fault branch;

[0055] According to the number n of substations in front of 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 of the fault branch and the first current output expression to construct the first equivalent impedance expression, and the first equivalent impedance Z f is the equivalent impedance between the first equivalent current source and the 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 connection point, X f is the equivalent reactance between the first equivalent current source and the connection point;

[0058] According to the number m of substations in the non-fault branch and the voltage phase angle δ nf-iConstruct the second current output expression, where the second current output expression is the current output expression of the second equivalent current source; the second current output expression is an expression regarding the active current reference value and the reactive current reference value of the non-faulty branch.

[0059]

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

[0061] According to the number of stations m in the non-faulty branch, the second equivalent resistance R nf-i , the second equivalent reactance X nf-i , the current output value of the non-faulty branch and the second current output expression, construct the second equivalent impedance expression, where 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] Obtain the first current upper limit value, where the first current upper limit value is the upper limit of the station current output; the station current output value includes the station current output value of the faulty branch and the station current output value of the non-faulty branch. For the faulty branch, the first current upper limit value is I f-k_lim , that is, I f-k_lim represents the upper limit of the current output of the k-th station in the faulty branch. For the non-faulty branch, the first current upper limit value is I nf-i_lim , that is, I nf-i_lim represents the upper limit of the current output of the i-th station in the non-faulty branch;

[0065] Based on the post-fault station group model, adopt the method of making full use of the station current limit, and calculate the first active current active support instruction and the first reactive current active support instruction according to the first current upper limit value and the grid connection point electrical quantities. The first active current support instruction is the active current support instruction of the station, and the first reactive current support instruction is the reactive current support instruction of the station; the first active current active support instruction includes the active current reference value I d_f-k_ref of the faulty branch and the active current reference value I d_nf-i_ref of the non-faulty branch, that is, Id_f-k_ref represents the reference value of the active current of the k-th station in the faulty branch, I d_nf-i_ref represents the reference value of the active current of the i-th station in the non-faulty branch; the first reactive current active support command includes the reference value of the reactive current of the faulty branch I q_f-k_ref and the reference value of the reactive current of the non-faulty branch I q_nf-i_ref , that is, I q_f-k_ref represents the reference value of the reactive current of the k-th station in the faulty branch, I q_nf-i_ref represents the reference value of the reactive current of the i-th station in the non-faulty branch.

[0066] To speed up the response time and avoid identifying the fault point location, the amplitude of the current output of each station can be continuously maintained at the upper limit value, and at the same time, the control master station monitors the grid voltage phase angle δ grid of the grid connection point through devices such as PMU, and sends the grid voltage phase angle δ grid of the grid connection point to each station. Based on the grid voltage phase angle δ grid obtained by communication at the grid connection point, each station can calculate the first active current active support command and the first reactive current active support command, realizing the active-reactive coordinated support control for fault ride-through and effectively reducing the communication data volume.

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

[0068]

[0069] In the formula, P ∑ is the total active power, that is, the total active power output value of the station group after the fault, Z grid is the impedance between the bus of the station group and the grid connection point, Z gnd is the impedance between the first equivalent current source and the fault point, the Re(·) function represents obtaining the real part, the (·)* function represents obtaining the conjugate, δ f is the grid connection point voltage phase angle of the first equivalent current source, δ nf is the grid connection point voltage phase angle of the second equivalent current source;

[0070] Since the impedance values of each station group remain constant after the fault occurs, if and only if the grid connection point voltage phase angle δ f of the first equivalent current source, the grid connection point voltage phase angle δ nf of the second equivalent current source are respectively equal to the grid connection point voltage phase angle δ gridEqual, when the substation current output value is the first current upper limit value (when the current amplitude reaches the sum of the current upper limits of each substation in the substation group), the active power output of the substation group reaches the maximum value:

[0071]

[0072] In the formula, P ∑max is the maximum total active power, that is, the maximum active power output of the substation 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] Thus, the first active current active support instruction and the first reactive current active support instruction are calculated as:

[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] Control the substation group 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 location is known: Obtain the fault point parameters and the substation group bus parameters; The substation group bus parameters include the third equivalent impedance, and the third equivalent impedance is the impedance Z grid between the substation group bus and the grid connection point; The fault point parameters include the fourth equivalent impedance, and the fourth equivalent impedance is the impedance Z gnd between the first equivalent current source and the fault point;

[0082] Based on the post-fault substation group model, construct the total active power expression according to the fault point parameters, the substation group bus parameters and the grid connection point electrical quantities. The specific steps are:

[0083] Based on the post-fault substation cluster 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 point voltage of the first equivalent current source; the second voltage is the grid connection point voltage of the second equivalent current source;

[0084]

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

[0086] Ignore the resistance of the collection line between substations in the new energy substation cluster and the active power loss generated by it.

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

[0088]

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

[0090]

[0091] Construct the total active power expression according to the first active power expression and the second active power expression;

[0092]

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

[0094] Based on the post-fault substation cluster model, adopt the method of making full use of the substation current limit. According to the second current upper limit value, the third current upper limit value, and the total active power expression, calculate and obtain the second active current active support instruction and the second reactive current active support instruction. The second active current active support instruction is the active current active support instruction of the post-fault substation cluster model, and the second reactive current active support instruction is the reactive current active support instruction of the post-fault substation cluster 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 power support command includes the first equivalent current source reactive current active power support command I f_q_ref and the second equivalent current source reactive current active power support command I nf_q_ref .

[0095] To achieve the maximum utilization of the substation current, the current of each substation should be output according to the maximum current limit value, that is, the current output values of the first equivalent current source and 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, I nf_q is the reactive current of the non-fault branch;

[0098] From the total active power expression, it can be seen that the grid connection point voltage phase angle δ f of the first equivalent current source, the grid connection point voltage phase angle δ nf of the second equivalent current source are respectively equal to the grid connection point power grid voltage phase angle δ grid . When the substation current is output to the maximum limit, the total active power output of the substation group reaches the maximum value:

[0099]

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

[0101]

[0102]

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

[0104]

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

[0106] Control the substation group according to the second active power support command and the second reactive power support command.

[0107] In some of these embodiments, the steps for determining a fault in the substation group are:

[0108] Obtain the reference voltage U * and the grid connection point voltage U of the substation l , preferably the reference voltage U * is 0.9 p.u., where p.u. is the per-unit value. When no fault occurs in the substation group, the substations in the substation group do not distinguish between fault branches and non-fault branches, that is, U l represents the grid connection point voltage of the l-th substation in the substation group, and l is the substation serial number in the substation group;

[0109] When the grid connection point voltage U of the substation l is less than the reference voltage U * , the corresponding substation is a faulty substation, that is, the l-th substation in the substation group is a faulty substation, and the substation branch where the faulty substation is located is a fault branch;

[0110] When the substation group includes at least one faulty substation, the substation group has a fault.

[0111] Next, a specific numerical example is used to elaborate in detail the implementation process and effect of the fault ride-through control method for a new energy substation group considering active and reactive power collaborative support proposed in this disclosure.

[0112] In this numerical example, a simulation model of a new energy substation group is built. The parameters of the new energy power source in the simulation model are shown in Table 1:

[0113] Table I New Energy Power Source Parameters

[0114] Parameter Name Value Rated Power per Substation PN / MW 500 Rated Line Voltage UN / kV 220 Unit Reactance of Line X / (Ω / km). 0.238 Average Line Length l / km 50 Upper Limit of Substation Current I / kA. 1.3 Number of Substations in Substation Group 20

[0115] The new energy substation group outputs at the rated power before the substation group fault occurs. Suppose a substation group fault occurs at 0.1 s, and the fault type is a three-phase ground short circuit. After the substation group fault, the active power and reactive power simulation results of the new energy substation group under the proposed fault ride-through control are as Figure 4 shown.

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

[0117] In summary, the present disclosure can perform optimized calculations for active power support for a new energy power station group, and on the premise of making full use of the controllable capabilities and overcurrent capabilities of each power station, improve the active power support capability of the power station group during a fault 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 solution of the present invention, rather than a limitation on the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A fault ride-through control method for a new energy station group considering active and reactive collaborative support, characterized in that: The following steps are involved: Obtaining the electrical quantity of the grid connection point, the parameters of the station group and the electrical quantity of the station group; the station group includes a plurality of station branches, and the station branch includes at least one station; When a station group fails, the plurality of station branches are divided into fault branches and non-fault branches according to whether the faulty station is included, and the faulty branch is the station branch where the faulty station is located; Based on the Thevenin equivalent method, a post-fault station group model is constructed according to the station group parameters and the electrical quantities of the station group, wherein the post-fault station group model includes a first equivalent current source and a second equivalent current source, wherein 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 connection point, and the second equivalent current source is an equivalent current source corresponding to the system between the non-fault branch and the grid connection point; Acquire a first current upper limit value, where the first current upper limit value is a station current output upper limit value; Based on the post-fault station group model, a station current limit utilization method is adopted, and a first active current active support instruction and a first reactive current active support instruction are calculated according to the first current upper limit value and the grid connection point electrical quantity, wherein the first active current support instruction is a station active current support instruction, and the first reactive current support instruction is a station reactive current support instruction; The station group is controlled according to the first active current active support instruction and the first reactive current active support instruction.

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

3. The fault ride-through control method for a new energy station group considering active and reactive collaborative support according to claim 2 is characterized in that: The first active current active support instruction includes a fault branch active current reference value and a non-fault branch active current reference value; The first reactive current active support instruction includes a reactive current reference value of a fault branch and a reactive current reference value of a non-fault branch.

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

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

6. The fault ride-through control method for a new energy station group considering active and reactive collaborative support according to claim 5 is characterized in that: 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; The second reactive current active support instruction includes a first equivalent current source reactive current active support instruction and a second equivalent current source reactive current active support instruction.

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

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

9. The fault ride-through control method for a new energy station group considering active and reactive collaborative support according to claim 1 is characterized in that: The steps of determining whether the station group has a fault are as follows: Obtain reference voltage and station grid connection point voltage; When the grid connection point voltage of the station 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; When the station group includes at least one of the faulty stations, the station group fails.

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

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