New energy gathering area short circuit capacity demand quantitative analysis method and device

Abstract

The invention discloses a new energy collection area short circuit capacity demand quantitative analysis method and device. The method comprises the following steps: establishing a new energy delivery system equivalent model; the new energy delivery system equivalent system is obtained from a to-be-analyzed large-scale new energy delivery system equivalent value; analyzing the influence of power distribution on the voltage drop range after the new energy system fails by using the model; generating a thermal power generating unit delivery system equivalent model with the same capacity according to the circuit parameters obtained by the new energy delivery system equivalent model; according to the principle that the steady-state voltage drop range of the same fault is consistent, determining a reactive demand model of the new energy station during the low-voltage ride-through period; and considering the current constraint, and determining the short-circuit capacity demand of the new energy station. According to the new energy collection area short-circuit capacity demand quantitative analysis method and device, the short-circuit capacity demand can be quantified, and the system fault extension range can be effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system stability analysis, and in particular relates to a method and device for quantitatively analyzing short-circuit capacity demand in a new energy collection area. Background Art

[0002] In deserts, Gobi and wasteland areas, large-scale renewable energy is transmitted over long distances. When a new energy system fails, the voltage is more seriously disturbed than that of traditional thermal power plants, and the voltage drop range is wider at the same line length. During the period when the new energy system encounters a fault and enters low voltage ride-through, under the existing active and reactive power distribution curves, the system maintains a relatively low voltage, and the fault has a large impact range. Therefore, in order to further optimize the new energy system, taking traditional thermal power units as an example, under the same system initial operating conditions and the same fault conditions, the principle of consistent steady-state values ​​of voltage drop between new energy power sources and synchronous power sources of the same capacity is followed, the power distribution curve of the new energy system after the fault is optimized, and the short-circuit capacity demand of the new energy collection area is analyzed and calculated.

[0003] The existing short-circuit capacity method is no longer suitable for the needs of short-circuit capacity analysis in the new energy collection area, and cannot guide the power distribution of the new energy system after a fault, which leads to a large impact range after the fault. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method and device for quantitative analysis of short-circuit capacity demand in a new energy collection area, which can quantify short-circuit capacity demand and effectively reduce the scope of system fault expansion.

[0005] Technical solution: A quantitative analysis method for short-circuit capacity demand in a new energy collection area of ​​the present invention comprises the following steps:

[0006] Step 1: Equivalent the large-scale new energy transmission system to be analyzed to a new energy transmission system equivalent model;

[0007] Step 2: Use the equivalent model of the new energy transmission system to analyze and calculate the impact of power distribution on the voltage drop range after the new energy system fails;

[0008] Step 3: Generate an equivalent model of a thermal power unit transmission system of the same capacity according to the circuit parameters obtained from the equivalent model of the new energy transmission system;

[0009] Step 4: According to the principle of consistent steady-state voltage drop range for the same fault, determine the reactive power demand model of the new energy station during the low voltage ride-through period;

[0010] Step 5: Consider the current constraints and determine the short-circuit capacity requirements of the new energy station.

[0011] Furthermore, the establishment of an equivalent model of the new energy delivery system includes:

[0012] The large-scale new energy transmission system to be analyzed is equivalent to the new energy transmission system equivalent model;

[0013] Furthermore, the voltage calculation model is used to calculate the voltage of each node of the equivalent model of the new energy transmission system, including:

[0014] The voltage calculation model is used to calculate the voltage at the new energy grid connection point and the voltage at different line positions of the new energy transmission system equivalent model.

[0015] The node voltage is used to analyze the impact of different active power and reactive power on the voltage at the grid connection point and the line after the new energy is low-voltage.

[0016] Furthermore, generating an equivalent model of the thermal power unit transmission system of the same capacity according to the acquired circuit parameters includes:

[0017] Using the circuit parameters, an equivalent model of the transmission system of thermal power units with the same capacity is constructed;

[0018] The voltage calculation model is used to calculate the grid connection point voltage of the thermal power unit and the voltages at different line positions of the equivalent model of the thermal power unit transmission system.

[0019] Furthermore, the reactive power demand model of the new energy station during the low voltage ride-through period is determined according to the principle of consistent steady-state voltage drop range for the same fault, including:

[0020] According to the principle of consistent steady-state voltage drop range for the same fault, the reactive power demand model of the new energy station during the low voltage ride-through period is determined.

[0021] Considering current constraints, determine the short-circuit capacity requirements of new energy stations.

[0022] In a second aspect, the present invention provides a device for quantitatively analyzing short-circuit capacity demand in a new energy collection area, comprising:

[0023] New energy equivalent module, used to convert the large-scale new energy transmission system to be analyzed into a new energy transmission system equivalent model;

[0024] Voltage drop range analysis module, used to analyze the impact of power distribution on voltage drop range after a new energy system failure;

[0025] The thermal power unit equivalent module generates an equivalent model of the thermal power unit transmission system with the same capacity and the same network parameters according to the circuit parameters obtained from the equivalent model of the new energy transmission system;

[0026] The reactive power calculation module determines the reactive power demand model of new energy stations during low voltage ride-through by following the principle of consistent steady-state voltage drop range under the same fault.

[0027] The short-circuit capacity calculation module considers current constraints and determines the short-circuit capacity requirements of new energy stations.

[0028] The present invention also discloses a computer device, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method of the present invention.

[0029] The present invention also discloses a computer-readable storage medium on which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, the steps of the method of the present invention are implemented.

[0030] The present invention also discloses a computer program product, comprising a computer program / instruction, which implements the steps of the method of the present invention when executed by a processor.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0032] (1) The method and device for quantitative analysis of short-circuit capacity demand in the new energy collection area provided by the present invention establish an equivalent model of the new energy transmission system; the equivalent system of the new energy transmission system is obtained by the equivalent value of the large-scale new energy transmission system to be analyzed; the model is used to analyze the influence of power distribution on the voltage drop range after the new energy system fails; the equivalent model of the transmission system of thermal power units with the same capacity is generated according to the circuit parameters obtained from the equivalent model of the new energy transmission system; according to the principle of consistency of the steady-state voltage drop range for the same fault, the demand model for reactive power of the new energy station during the low voltage ride-through period is determined; considering the current constraint, the short-circuit capacity demand of the new energy station is determined. The method and device for quantitative analysis of short-circuit capacity demand in the new energy collection area provided by the present invention can quantify the short-circuit capacity demand and effectively reduce the expansion range of system faults.

[0033] (2) Under the same operating conditions, traditional thermal power units have stronger voltage stability and larger maximum transmission power, while new energy units have poor interference resistance and relatively small power transmission limits. Referring to the dynamic characteristics of thermal power units, enhancing the dynamic characteristics of new energy units is beneficial to the stability of the power grid. At present, the grid connection of new energy stations meets the requirements of the short-circuit ratio of new energy multiple stations. The short-circuit ratio of new energy multiple stations does not take into account the system state during the dynamic period. Considering the voltage drop range and drop depth after the fault, determining the short-circuit ratio of new energy is beneficial to the stability of the system after the fault. In addition, the short-circuit capacity requirements of new energy units with different system strengths are different. This method is more targeted in combination with actual operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of a method for quantitatively analyzing short-circuit capacity demand in a new energy collection area provided by an embodiment of the present invention;

[0035] Figure 2 It is a schematic diagram of the structure of a large-scale new energy delivery system to be analyzed provided by an embodiment of the present invention;

[0036] Figure 3 is a diagram of a new energy delivery system after equalization provided by an embodiment of the present invention;

[0037] Figure 4 is a diagram of a thermal power transmission system after equalization provided by an embodiment of the present invention;

[0038] Figure 5 It is a schematic diagram of the structure of a device for quantitatively analyzing short-circuit capacity demand in a new energy collection area provided by an embodiment of the present invention;

[0039] Figure 6 is a schematic diagram of the physical structure of an electronic device provided by an embodiment of the present invention;

[0040] Figure 7 Wind turbine power ride-through curve diagram;

[0041] Figure 8 It is the voltage drop curve diagram;

[0042] Fig. 9 This is the reactive power multiple diagram. DETAILED DESCRIPTION

[0043] The mathematical model of the new energy / thermal power equivalent transmission system is established based on Matlab, where X s =0.3, X=0.2, E1=1.1, U G =1.0, power factor cosφ=0.98, and the voltage at the grid connection point of thermal power units and new energy units is analyzed. When the system encounters a fault and the voltage fluctuates, if the new energy side does not generate additional reactive power, the crossing curve is as follows: Figure 7 Shown

[0044] Figure 7 In the figure, the green curve is the reactive power curve under the capacity constraint of the wind turbine, the red curve is the active output curve of the wind turbine as the voltage drops, and the blue curve is the theoretical reactive power curve derived from formula (21). According to formula (22), the reactive power output value of the new energy side is adjusted, and the reactive power multiple is set. Adjust the reactive power multiple according to different voltage drop levels to make the new energy system correspond Figure 8 The blue curve shows that some additional reactive power is emitted, and the reactive power multiple k is as follows: Fig. 9 As shown, the voltage value of the measuring node is obtained.

[0045] Wind turbines provide reactive power support according to the theoretical reactive power curve in case of faults. Under faults with different drop depths, the measured node voltage height is similar to that of thermal power units under the same capacity. At this time, the wind power system needs to provide at least 2.2 times the short-circuit capacity support.

[0046] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0047] Taking the server as an execution subject as an example, the specific implementation process of the method for quantitative analysis of short-circuit capacity demand in a new energy collection area provided in an embodiment of the present invention is explained.

[0048] Figure 1 FIG. 1 is a flow chart of a method for quantitatively analyzing short-circuit capacity demand in a new energy collection area provided by an embodiment of the present invention. Figure 1 As shown, the quantitative analysis method of short-circuit capacity demand in a new energy collection area provided by the present invention includes:

[0049] S101: Establish an equivalent model of the new energy delivery system;

[0050] S102: using the model to analyze and calculate the impact of power distribution on the voltage drop range after a new energy system failure;

[0051] S103: Generate an equivalent model of a thermal power transmission system of the same capacity according to circuit parameters obtained from the equivalent model of the new energy transmission system;

[0052] S104: Based on the principle of consistent steady-state voltage drop range for the same fault, determine the reactive power demand model of the new energy station during the low voltage ride-through period.

[0053] S105: Short-circuit capacity calculation module, considering current constraints, determines the short-circuit capacity requirements of new energy stations.

[0054] from Figure 1 It can be seen from the process shown that the quantitative analysis method of short-circuit capacity demand in the new energy collection area provided by the present invention is achieved by establishing an equivalent model of the new energy transmission system; the equivalent system of the new energy transmission system is obtained by the equivalent value of the large-scale new energy transmission system to be analyzed; the model is used to analyze the impact of power distribution on the voltage drop range after the new energy system fails; the equivalent model of the transmission system of thermal power units of the same capacity is generated according to the circuit parameters obtained from the equivalent model of the new energy transmission system; according to the principle of consistent steady-state voltage drop range for the same fault, the demand model for reactive power of the new energy station during low voltage crossing is determined; considering the current constraint, the short-circuit capacity demand of the new energy station is determined. The quantitative analysis method and device for short-circuit capacity demand in the new energy collection area provided by the present invention can quantify the short-circuit capacity demand and effectively reduce the scope of system fault extension. Each step is explained in detail below.

[0055] S101: Establishing an equivalent model of a new energy transmission system; the new energy transmission system equivalent system is obtained by equivalently evaluating a large-scale new energy transmission system to be analyzed;

[0056] Specifically, the server equates the large-scale new energy delivery system to be analyzed to a new energy delivery system equivalent model. In one embodiment, Figure 2 Schematic diagram of the structure of the large-scale new energy delivery system to be analyzed, which includes 17 new energy stations, but the present invention is not limited to this.

[0057] The power of the same type of units in the same area is equal, and the network impedance is calculated using the loss consistency principle.

[0058] Equivalent power of doubly-fed unit:

[0059] Equivalent power of direct drive unit:

[0060] Photovoltaic equivalent power:

[0061] The power of the external transmission section is:

[0062] New energy power and: S SUMeq =S Deq +S Peq +S Veq , network loss S Neq =S SUMeq -S S (5)

[0063] Network impedance

[0064] Where P DK , Q DK , P PK , Q PK , P VK , Q VK are the active power of the doubly-fed unit, the reactive power of the doubly-fed unit, the active power of the direct-drive unit, the reactive power of the direct-drive unit, the photovoltaic active power and the photovoltaic reactive power of the kth renewable energy station in the large-scale renewable energy transmission system; S Deq , S Peq and S Veq are the equivalent double-fed unit power, direct-drive unit power and photovoltaic power respectively; S l is the power of the lth line of the transmission section, S s is the power sum of the transmission section; S Neq is the network loss including line and transformer losses, Z Neq is the network impedance including line and transformer losses, and E1 is the equivalent potential of the AC system.

[0065] In one embodiment, the external power grid uses the ward equivalent method to simplify the network and obtains equivalent parameters of the transmission system of the new energy-single synchronous machine.

[0066] S102: using the model to analyze and calculate the impact of power distribution on the voltage drop range after a new energy system failure;

[0067] Will be like Figure 2 The large-scale new energy transmission system to be analyzed is equivalent to the new energy transmission system equivalent model. The equivalent new energy transmission system is as follows: Figure 3 As shown. P and Q are the active power and reactive power injected into the new energy node, U is the voltage of the new energy grid connection point, U1 is the voltage in the middle area of ​​the line, and θ1 is the reference bus power angle. The impedance from U1 to the AC grid is X and the resistance is R, and the impedance from E1 to the new energy grid connection point is Xs and the resistance is Rs. , E1 is the equivalent potential of the AC system, I is the injected current at the grid connection point, i d and i q are the currents on the d-axis and q-axis.

[0068] Reference busbar grid connection point voltage:

[0069]

[0070] New energy grid-connected point injection power:

[0071]

[0072] Combining equations (8), (9), and (10), we can obtain:

[0073]

[0074] Multiply both sides by R S 2 +X S 2 , and obtain the relationship between the grid connection point voltage and the injected active and reactive power.

[0075]

[0076] Ignore the line resistance parameter R S .

[0077]

[0078] For a single-feed system containing renewable energy, there is a point in the line with an impedance of X to the AC grid. Let the voltage at this point be U1.

[0079]

[0080] In the formula

[0081] It can be seen from formula (13) that for the new energy system, when the fault enters the low voltage ride-through, different active and reactive power distribution will affect the voltage of the new energy grid connection point, and then affect the voltage at the system line. Therefore, after the system fault, by adjusting the active and reactive power distribution of the new energy system, the extension range of the voltage fault can be effectively reduced.

[0082] S103: Generate an equivalent model of a thermal power transmission system of the same capacity according to circuit parameters obtained from the equivalent model of the new energy transmission system;

[0083] Specifically, the thermal power transmission system is obtained by calculating the equivalent value of the new energy transmission system parameters based on the server. The equivalent thermal power transmission system is as follows: Figure 4 Show.

[0084] The input node of the thermal power unit is regarded as a PV node, P G is the power injected into the PV node, U G is the PV node input voltage, I2 is the current flowing into the PV node, U2 is the line voltage node on the thermal power unit side, E1 is the equivalent potential of the AC system, and θ2 is the PV node power angle.

[0085] When the system is in steady state, we can get from formula (15):

[0086]

[0087] in

[0088] S104: Based on the principle of consistent steady-state voltage drop range for the same fault, determine the reactive power demand model of the new energy station during the low voltage ride-through period.

[0089] When the system experiences voltage fluctuations and enters a new stable state, it is considered that the infinite power grid becomes E2. It is considered that after the system fault causes voltage fluctuations, the changes in active power and reactive power P and Q injected by the new energy node conform to the low voltage ride-through curve. That is, it is considered that when the voltage drops to 0-0.2pu, it enters the 0 ride-through period, and during the 0.2-0.9pu period, the active power changes in proportion to the voltage. The inertia of traditional thermal power units is large, so it is considered that the power angle of the thermal power unit remains unchanged at the moment of voltage change, that is, P G The infinite grid E2 value changes in direct proportion.

[0090] When a fault occurs in the system and causes a voltage drop, the wind turbine enters low voltage ride-through, with active power reduced and reactive current increased. Under the same fault condition, the voltage drop of the new energy unit is ΔU1=U1-U1′, and the voltage drop of the thermal power unit is ΔU2=U2-U2′, where U1′ and U2′ are the voltage values ​​after voltage fluctuation.

[0091] For the renewable energy side, the reactive current can be adjusted to adjust the reactive voltage value of the renewable energy side to stabilize the voltage on the renewable energy side. When a system failure occurs, the renewable energy unit adjusts the reactive current to keep the voltage drops ΔU1 and ΔU2 consistent.

[0092]

[0093] Where θ1' and θ2' are the power angles of PQ and PV nodes after the fault respectively. The simultaneous equations (17) and (18) can be obtained.

[0094]

[0095] The theoretical maintenance value U' of the new energy outlet voltage under the same drop depth is obtained:

[0096]

[0097] Combining equations (13) and (20), we can get the theoretical value of reactive power Q' of new energy export:

[0098]

[0099] The theoretical value divided by the actual output value is the additional output reactive power multiple k.

[0100]

[0101] From formula (21), it can be concluded that under the same fault level and at the same line distance, the voltage drop depth of the traditional thermal power unit is smaller than that of the new energy unit. The new energy unit needs to generate additional reactive power to keep the voltage drop consistent. That is, the new energy unit needs to provide capacity

[0102] S105: Considering the current constraint, determine the short-circuit capacity requirement of the new energy station.

[0103] If current constraints are used for system model analysis, the output current of the grid-connected point is decomposed in the dq rotating coordinate system, and the relationship between it and the dq axis current component can be obtained as follows:

[0104] I=(i d +ji q ) jθ (twenty three)

[0105] Considering the current constraint of k1 times, it is assumed that during the fault period:

[0106]

[0107] The voltage U of the new energy grid connection point can be obtained as:

[0108]

[0109] For the PV node, consider the internal resistance X of the thermal power unit d , the thermal power unit E q is considered constant. Then:

[0110]

[0111] If the system active power P=1 is maintained unchanged, it is considered that the wind turbine is in full power state:

[0112]

[0113] Substituting equation (27) into equation (25) yields the relationship between the voltage E1 and U at both ends under the constraint of current k1:

[0114]

[0115] If the voltage drop on both sides is assumed to be equal, and U G =U, we get:

[0116]

[0117] Through thermal power unit U G Based on the drop curve and the active power maintenance requirements of the wind turbine, calculate the reactive current i required by the wind turbine at this moment. d 、i q value:

[0118]

[0119] Substitute into equation (24) to verify whether the current constraint is met. At this moment, the short-circuit capacity required by the wind turbine system is

[0120]

[0121] The present invention provides a method for quantitative analysis of short-circuit capacity demand in a new energy collection area, and establishes an equivalent model of a new energy delivery system; the new energy delivery system equivalent system is obtained by the equivalent value of a large-scale new energy delivery system to be analyzed; the model is used to analyze the impact of power distribution on the voltage drop range after a new energy system failure; an equivalent model of a thermal power unit delivery system of the same capacity is generated according to the circuit parameters obtained from the equivalent model of the new energy delivery system; according to the principle of consistency of the steady-state voltage drop range for the same fault, a demand model for reactive power at a new energy station during low voltage ride-through is determined; and the short-circuit capacity demand of a new energy station is determined by taking into account current constraints. The method and device for quantitative analysis of short-circuit capacity demand in a new energy collection area provided by the present invention can quantify short-circuit capacity demand and effectively reduce the scope of system failure extension.

[0122] Based on the same inventive concept, an embodiment of the present invention further provides a device for quantitatively analyzing short-circuit capacity demand in a new energy collection area, which can be used to implement the method described in the above embodiment, as described in the following embodiment.

[0123] Since the principle of solving the problem by the short-circuit capacity demand quantitative analysis device for the new energy convergence area is similar to the short-circuit capacity demand quantitative analysis method for the new energy convergence area, the implementation of the short-circuit capacity demand quantitative analysis device for the new energy convergence area can refer to the implementation of the method based on software performance benchmark determination, and the repeated parts will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the system described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0124] Figure 5 : is a schematic diagram of a short-circuit capacity demand quantitative analysis device for a new energy collection area provided by an embodiment of the present invention, such as Figure 5 As shown, the device comprises:

[0125] A new energy equivalent unit 501 is used to equate the large-scale new energy transmission system to be analyzed to a new energy transmission system equivalent model;

[0126] The voltage drop range analysis unit 502 is used to analyze the impact of power distribution on the voltage drop range after a new energy system failure;

[0127] The thermal power unit equivalent unit 503 generates an equivalent model of the thermal power unit transmission system with the same capacity and the same network parameters according to the circuit parameters obtained from the equivalent model of the new energy transmission system;

[0128] The reactive power calculation unit 504 determines the reactive power demand model of the new energy station during the low voltage ride-through period by following the principle of consistent steady-state voltage drop range under the same fault.

[0129] The short-circuit capacity calculation unit 505 determines the short-circuit capacity requirement of the new energy station by taking into account the current constraint.

[0130] The present invention provides a method and device for quantitative analysis of short-circuit capacity demand in a new energy collection area, establishes an equivalent model of a new energy transmission system; the equivalent system of the new energy transmission system is obtained by the equivalent value of a large-scale new energy transmission system to be analyzed; uses the model to analyze the impact of power distribution on the voltage drop range after a new energy system failure; generates an equivalent model of a thermal power transmission system of the same capacity according to the circuit parameters obtained from the equivalent model of the new energy transmission system; determines the reactive power demand model of a new energy station during low voltage ride-through according to the principle of consistent steady-state voltage drop range for the same fault; and determines the short-circuit capacity demand of a new energy station by taking into account current constraints. The method and device for quantitative analysis of short-circuit capacity demand in a new energy collection area provided by the present invention can quantify the short-circuit capacity demand and effectively reduce the range of system failure extension.

[0131] Figure 6 It is a schematic diagram of the physical structure of an electronic device provided by an embodiment of the present invention, and the electronic device may include: a processor 1101, a communication interface 1102, a memory 1103 and a communication bus 1104, wherein the processor 1101, the communication interface 1102, and the memory 1103 complete mutual communication through the communication bus 1104. The processor 1101 can call the logic instructions in the memory 1103 to execute the following method: establish an equivalent model of a new energy transmission system; the new energy transmission system equivalent system is obtained by the equivalent value of a large-scale new energy transmission system to be analyzed; use the model to analyze the influence of power distribution on the voltage drop range after a new energy system fault; generate an equivalent model of a thermal power unit transmission system of the same capacity according to the circuit parameters obtained from the equivalent model of the new energy transmission system; determine the demand model for reactive power of a new energy station during low voltage ride-through according to the principle of consistent steady-state voltage drop range for the same fault; and determine the short-circuit capacity demand of a new energy station considering current constraints.

[0132] In addition, the logic instructions in the above-mentioned memory 1103 can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0133] This embodiment discloses a computer program product, which includes a computer program stored on a computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the methods provided by the above-mentioned method embodiments, for example, including: establishing an equivalent model of a new energy transmission system; the new energy transmission system equivalent system is obtained by the equivalent value of a large-scale new energy transmission system to be analyzed; using the model to analyze the impact of power distribution on the voltage drop range after a new energy system fault; generating an equivalent model of a thermal power transmission system of the same capacity according to circuit parameters obtained from the equivalent model of the new energy transmission system; determining a reactive power demand model for new energy stations during low voltage riding according to the principle of consistent steady-state voltage drop range for the same fault; and determining the short-circuit capacity demand of new energy stations considering current constraints.

[0134] The present embodiment provides a computer-readable storage medium, which stores a computer program, and the computer program enables the computer to execute the methods provided by the above-mentioned method embodiments, for example, including: establishing an equivalent model of a new energy transmission system; the new energy transmission system equivalent system is obtained by the equivalent value of a large-scale new energy transmission system to be analyzed; using the model to analyze the impact of power distribution on the voltage drop range after a new energy system fault; generating an equivalent model of a thermal power transmission system of the same capacity according to circuit parameters obtained from the equivalent model of the new energy transmission system; determining a reactive power demand model for new energy stations during low voltage crossing according to the principle of consistent steady-state voltage drop range for the same fault; and determining the short-circuit capacity demand of new energy stations considering current constraints.

[0135] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0136] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0137] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0138] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0139] In the description of this specification, the description with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0140] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A quantitative analysis method for short-circuit capacity demand in a new energy collection area, characterized in that: The steps include: Step 1: Equivalent the large-scale new energy transmission system to be analyzed to a new energy transmission system equivalent model; Step 2: Use the equivalent model of the new energy transmission system to analyze and calculate the impact of power distribution on the voltage drop range after the new energy system fails; Step 3: Generate an equivalent model of a thermal power unit transmission system of the same capacity according to the circuit parameters obtained from the equivalent model of the new energy transmission system; Step 4: According to the principle of consistent steady-state voltage drop range for the same fault, determine the reactive power demand model of the new energy station during the low voltage ride-through period; Step 5: Consider the current constraints and determine the short-circuit capacity requirements of the new energy station.

2. According to claim 1, a quantitative analysis method for short-circuit capacity demand in a new energy collection area is characterized in that: Step 1 is specifically as follows: establishing an equivalent model of a new energy transmission system; the new energy transmission system is obtained by equivalently evaluating a large-scale new energy transmission system to be analyzed, the power of the same type of units in the same area is equivalent, and the network impedance is calculated by the loss consistency principle; Equivalent power of doubly-fed unit: Equivalent power of direct drive unit: Photovoltaic equivalent power: The power of the external transmission section is: New energy power and: S SUMeq =S Deq +S Peq +S Veq , network loss S Neq =S SUMeq -S S (5) Network impedance Where P DK , Q DK , P PK , Q PK , P VK , Q VK are the active power of the doubly-fed unit, the reactive power of the doubly-fed unit, the active power of the direct-drive unit, the reactive power of the direct-drive unit, the photovoltaic active power and the photovoltaic reactive power of the kth new energy station in the large-scale new energy transmission system; P1 represents the active power of the lth line of the transmission section, Q1 represents the reactive power of the lth line of the transmission section, n represents that there are n lines in the transmission section, and m represents that there are m new energy stations in total; S Deq , S Peq and S Veq are the equivalent double-fed unit power, direct-drive unit power and photovoltaic power respectively; S l is the power of the lth line of the transmission section, S s is the power sum of the transmission section; S Neq is the network loss including line and transformer losses, Z Neq is the network impedance including line and transformer losses, E1 is the equivalent potential of the AC system; The external power grid uses the ward equivalent method to simplify the network and obtains the equivalent parameters of the transmission system of the new energy-single synchronous machine.

3. The method for quantitative analysis of short-circuit capacity demand in a new energy collection area according to claim 1 is characterized in that: Step 2 is specifically as follows: using the equivalent model of the renewable energy transmission system to analyze and calculate the impact of power distribution on the voltage drop range after the failure of the renewable energy system, the large-scale renewable energy transmission system to be analyzed is equivalent to the equivalent model of the renewable energy transmission system, where P and Q are the active power and reactive power injected into the renewable energy node, U is the voltage at the renewable energy grid connection point, U1 is the voltage in the middle area of ​​the line, θ1 is the reference bus power angle, the impedance from U1 to the AC power grid is X and the resistance is R, the impedance from E1 to the renewable energy grid connection point is Xs and the resistance is Rs, E1 is the equivalent potential of the AC system, I is the injected current at the grid connection point, i d and i q is the current on the d-axis and q-axis; Reference bus grid connection point voltage: New energy grid-connected point injection power: Combining equations (8), (9), and (10), we can get: Multiply both sides by R S 2 +X S 2 , get the relationship between the grid connection point voltage and the injected active and reactive power; Ignore the line resistance parameter R S ; For a single-feed system with renewable energy, there is a point in the line with an impedance of X to the AC grid. Let the voltage at this point be U1: In the formula It can be seen from formula (13) that for the new energy system, when the fault enters the low voltage ride-through, different active and reactive power distribution will affect the voltage of the new energy grid connection point, and then affect the voltage at the system line. Therefore, after the system fault, the active and reactive power distribution of the new energy system is adjusted to reduce the extension range of the voltage fault.

4. The method for quantitative analysis of short-circuit capacity demand in a new energy collection area according to claim 1 is characterized in that: Step 3 is as follows: According to the server calculation, the parameters of the new energy transmission system are obtained to obtain the equivalent transmission system of thermal power. The input nodes of the thermal power units are regarded as PV nodes, U G is the PV node input voltage, P G is the power injected into the PV node, I2 is the current flowing into the PV node, U2 is the line voltage node on the thermal power unit side, E1 is the equivalent potential of the AC system, and θ2 is the power angle of the PV node; When the system is in steady state, we can get from formula (15): in 5. The method for quantitative analysis of short-circuit capacity demand in a new energy collection area according to claim 1 is characterized in that: Step 4 is as follows: according to the principle of consistent steady-state voltage drop range for the same fault, determine the reactive power demand model of the new energy station during the low voltage ride-through period. When the system voltage fluctuates and enters a new stable state, it is considered that the infinite power grid becomes E2. It is considered that after the system fault causes voltage fluctuation, the changes in active power and reactive power P and Q injected by the new energy node conform to the low voltage ride-through curve. That is, it is considered that when the voltage drops to 0-0.2pu, it enters the 0 ride-through period. During the 0.2-0.9pu period, the active power changes in proportion to the voltage. Due to the large inertia of the thermal power unit, it is assumed that the power angle of the thermal power unit remains unchanged at the moment of voltage change, that is, P G The infinite grid E2 value changes in direct proportion; When a fault occurs in the system and causes a voltage drop, the wind turbine enters low voltage ride-through, the active power decreases while the reactive current increases. Under the same fault condition, the voltage drop of the new energy unit is ΔU1=U1-U1′, and the voltage drop of the thermal power unit is ΔU2=U2-U2′, where U1′ and U2′ are the voltage values ​​after voltage fluctuation; For the renewable energy side, the reactive current is adjusted to adjust the reactive voltage value on the renewable energy side to stabilize the voltage on the renewable energy side. When a system failure occurs, the renewable energy unit adjusts the reactive current to keep the voltage drops ΔU1 and ΔU2 consistent. Where θ1' and θ2' are the power angles of PQ and PV nodes after the fault respectively. Combining equations (17) and (18), we can get: The theoretical maintenance value U' of the new energy outlet voltage under the same drop depth is obtained: Combining equations (13) and (20), we can get the theoretical value of reactive power Q' of new energy export: The theoretical value divided by the actual output value is the additional output reactive power multiple k; From formula (21), it can be concluded that under the same fault level and at the same line distance, the voltage drop depth of the thermal power unit is smaller than that of the new energy unit. The new energy unit needs to generate additional reactive power to keep the voltage drop consistent. That is, the new energy unit needs to provide capacity 6. The method for quantitative analysis of short-circuit capacity demand in a new energy collection area according to claim 1 is characterized in that: Step 5 is as follows: considering the current constraint, determining the short-circuit capacity demand of the new energy station, using the current constraint for the system model analysis, decomposing the output current of the grid connection point in the dq rotating coordinate system, and obtaining the relationship between it and the dq axis current component: I=(i d +ji q ) e jθ (23) Considering the current constraint of k1 times, it is assumed that during the fault period: The voltage of the new energy grid connection point is calculated as: For the PV node, consider the internal resistance X of the thermal power unit d , the thermal power unit E q Considered constant, then: If the system active power P=1 is maintained unchanged, it is considered that the wind turbine is in full power state: Substituting equation (27) into equation (25) yields the relationship between the voltage E1 and U at both ends under the constraint of current k1: If the voltage drop on both sides is assumed to be equal, and U G =U, we get: Through thermal power unit U G Based on the drop curve and the active power maintenance requirements of the wind turbine, calculate the reactive current i required by the wind turbine at this moment. d 、i q value: Substitute into equation (24) to verify whether the current constraint is met. At this moment, the short-circuit capacity required by the wind turbine system is 7. A device for quantitative analysis of short-circuit capacity demand in a new energy collection area, used to implement the method described in any one of claims 1 to 6, characterized in that: include: New energy equivalent module, used to convert the large-scale new energy transmission system to be analyzed into a new energy transmission system equivalent model; Voltage drop range analysis module, used to analyze the impact of power distribution on voltage drop range after a new energy system failure; The thermal power unit equivalent module generates an equivalent model of the thermal power unit transmission system with the same capacity and the same network parameters according to the circuit parameters obtained from the equivalent model of the new energy transmission system; The reactive power calculation module determines the reactive power demand model of the new energy station during the low voltage ride-through period by following the principle of consistent steady-state voltage drop range for the same fault; The short-circuit capacity calculation module considers current constraints and determines the short-circuit capacity requirements of new energy stations.

8. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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