CN-121791183-B - System frequency response estimation method and system based on fault position

CN121791183BCN 121791183 BCN121791183 BCN 121791183BCN-121791183-B

Abstract

The invention provides a system frequency response estimation method and system based on fault positions, which belong to the technical field of new energy power grids and comprise the steps of constructing a new energy multi-operation state model, solving node voltage after faults on the state model based on superposition principles and iterative calculation, establishing a mapping model of the fault positions and low-pass clusters, obtaining initial values of active power shortages, comprehensively considering the differences of the active power shortages initial values and active recovery rates among stations in different fault positions, calculating the total active power shortages of a system level considering the differences of low-pass characteristics of the stations, constructing a system frequency response model based on the differences of frequency modulation capability caused by the fault positions, and estimating system frequency response by adopting the response model. The invention realizes the quantitative description of active power deficiency and system equivalent frequency modulation capacity loss after disturbance at different fault positions so as to improve the accuracy of frequency response analysis.

Inventors

YUAN ZHIHAO
MA YANYU

Assignees

山东大学

Dates

Publication Date: 20260512
Application Date: 20260304

Claims (8)

1. A method for estimating a system frequency response based on a location of a fault, comprising: constructing a new energy multi-operation state model, wherein the multi-operation state comprises a steady-state operation state, a fault ride-through state and a frequency adjustment state; Solving node voltage after faults on the state model based on superposition principle and iterative calculation, establishing a mapping model of a fault position and a low-penetration cluster, determining the voltage drop degree of a unit based on the mapping model to obtain an initial value of active power deficiency, comprehensively considering the initial value of active power deficiency and the difference of active recovery rate between stations at different fault positions, and calculating the total active power deficiency of a system level considering the difference of low-penetration characteristics of the stations; Adopting a new energy station frequency modulation capability state switching coefficient, weighting and polymerizing to form a system equivalent frequency modulation capability availability, constructing a system frequency response model based on frequency modulation capability difference caused by fault positions, and estimating system frequency response by adopting the response model; the method for determining the voltage drop degree of the unit based on the mapping model to obtain the initial value of the active power shortage specifically comprises the following steps: The node voltage vector after the fault is taken as core input, and is compared with a preset low voltage crossing threshold value to determine the constitution of a low-pass cluster corresponding to the fault position; Determining the dropping degree of the new energy node voltage according to the node voltage solving model, and calculating the initial value of the active power deficiency: In the formula, An initial value for the active power deficiency; And Reactive current and active current which are respectively injected into the wind turbine generator set during the low-pass period; And Respectively the rated voltage and the rated current of the new energy node, The current limit value of the wind turbine generator is set; The grid-connected point voltage is the voltage of the new energy; Grid-connected point for new energy a direct axis component of the voltage; The initial value of the active power of the new energy is used; n represents the number of all wind power stations of the whole system; the expression of the system frequency response model based on the fault position induced frequency modulation capability difference is as follows: In the formula, Is the frequency deviation; representing transfer functions Is the j-th residue; representing transfer functions Is the jth pole of (2); representing the active recovery rate of the ith wind turbine entering the low-penetration wind turbine; the active power initial value of the ith wind power station; m is the number of wind power stations entering the low penetration; The time of occurrence of the fault is the time of occurrence of the fault; The fault clearing time is the fault clearing time; the active resume completion time for the mth station.
2. The method for estimating a system frequency response based on a fault location according to claim 1, wherein the step of solving the state model for the post-fault node voltage based on a superposition principle and an iterative calculation comprises the steps of: Step 1, setting iteration times, taking a trend solution before failure as an initial node voltage column vector, and initializing an equivalent model of each new energy node according to control logic of each new energy node based on the initial node voltage column vector; Step 2, forming a node admittance matrix based on an operation topological structure, regarding the fault as adding one or more new branches in a network according to the type and the position of the fault, correcting and forming the node admittance matrix under the fault state, solving and obtaining a node voltage correction amount based on the node admittance matrix under the fault state and an injection current vector, and updating voltage based on the node voltage correction amount to obtain a new solution of the node voltage of the whole network; Step 3, judging whether each new energy node meets the condition again according to the new voltage solution of the nodes of the whole network, and dynamically updating the low-penetration cluster; Step 4, checking whether the node voltage and the low-pass cluster output current tend to be stable, stopping iteration if the convergence tolerance is met, and outputting an iteration result, otherwise, increasing the iteration result And returns to step 2.
3. The method of estimating a system frequency response based on a fault location of claim 1, wherein the system level total active power deficiency expression is: In the formula, Active power shortage of the wind turbine generator; the active power initial value of the ith wind power station; Is that M is the number of stations entering the low-pass station; the time of failure occurrence; fault removal time; the active recovery completion time for the mth station; is the active recovery rate; Is that Time unit step function.
4. The method for estimating system frequency response based on fault location as claimed in claim 1, wherein said adopting new energy station frequency modulation capability state switching coefficient, weighting and aggregating to form system equivalent frequency modulation capability availability is specifically as follows: Defining a fan single machine state switching coefficient, and mapping the fan single machine state switching coefficient into an equivalent frequency modulation coefficient representing the availability of the wind power frequency modulation capability of the whole system through weighted aggregation: In the formula, Is an equivalent frequency modulation coefficient; The state switching coefficient is the single fan state; virtual inertia for the ith incoming low pass wind farm; the virtual inertia of the j-th low-penetration wind power station; , The rated capacity of the j-th wind power station is the rated capacity of the i-th wind power station, n represents the number of all wind power stations of the whole system, and m represents the number of wind power stations entering the low pass wind power station after the fault.
5. The method of estimating a system frequency response based on a fault location as claimed in claim 4, wherein the system frequency response based on the equivalent frequency modulation factor is connected in series with a basic equivalent model to form a complete dynamic equivalent fan model, and the output is: In the formula, In order for the frequency deviation to be a function of, Is a virtual inertia time constant of the wind turbine generator, The droop control coefficient of the wind turbine generator is used.
6. A fault location based system frequency response estimation system comprising: The system comprises a state construction module, a control module and a control module, wherein the state construction module is configured to construct a new energy multi-operation state model, and the multi-operation state comprises a steady-state operation state, a fault ride-through state and a frequency adjustment state; The parameter calculation module is configured to solve node voltage after faults on the basis of superposition principles and iterative calculation, establish a mapping model of a fault position and a low-penetration cluster, determine the voltage drop degree of a unit based on the mapping model to obtain an initial value of active power deficiency, comprehensively consider the difference between the initial value of active power deficiency and active recovery rate among stations at different fault positions, and calculate a system-level total active power deficiency considering the difference of low-penetration characteristics of the stations; The frequency response module is configured to adopt a new energy station frequency modulation capability state switching coefficient, weight and aggregate the new energy station frequency modulation capability state switching coefficient to form a system equivalent frequency modulation capability availability, construct a system frequency response model based on a fault position induced frequency modulation capability difference, and estimate system frequency response by adopting the response model; the method for determining the voltage drop degree of the unit based on the mapping model to obtain the initial value of the active power shortage specifically comprises the following steps: The node voltage vector after the fault is taken as core input, and is compared with a preset low voltage crossing threshold value to determine the constitution of a low-pass cluster corresponding to the fault position; Determining the dropping degree of the new energy node voltage according to the node voltage solving model, and calculating the initial value of the active power deficiency: In the formula, An initial value for the active power deficiency; And Reactive current and active current which are respectively injected into the wind turbine generator set during the low-pass period; And Respectively the rated voltage and the rated current of the new energy node, The current limit value of the wind turbine generator is set; The grid-connected point voltage is the voltage of the new energy; Grid-connected point for new energy a direct axis component of the voltage; The initial value of the active power of the new energy is used; n represents the number of all wind power stations of the whole system; the expression of the system frequency response model based on the fault position induced frequency modulation capability difference is as follows: In the formula, Is the frequency deviation; representing transfer functions Is the j-th residue; representing transfer functions Is the jth pole of (2); representing the active recovery rate of the ith wind turbine entering the low-penetration wind turbine; the active power initial value of the ith wind power station; m is the number of wind power stations entering the low penetration; The time of occurrence of the fault is the time of occurrence of the fault; The fault clearing time is the fault clearing time; the active resume completion time for the mth station.
7. An electronic device comprising a memory and a processor, and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the fault location based system frequency response estimation method of any one of claims 1-5.
8. A computer readable storage medium storing computer instructions which, when executed by a processor, perform the fault location based system frequency response estimation method of any one of claims 1-5.

Description

System frequency response estimation method and system based on fault position Technical Field The invention belongs to the technical field of new energy power grids, and particularly relates to a system frequency response estimation method and system based on a fault position. Background The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art. With the continuous access of high-proportion new energy, a traditional power system taking a synchronous machine as a main component is moving towards a novel power system with electric power electronization, the inertia level and frequency modulation capability of the system are reduced, and the frequency safety problem under fault disturbance is more remarkable. In the high-proportion new energy power grid, new energy is required to have the capacity of actively participating in frequency modulation, and when a large number of new energy units capable of actively participating in frequency modulation enter low voltage ride-through (LVRT), the new energy units do not have the frequency supporting capacity any more, so that the high-capacity power shortage caused by the frequency supporting capacity can cause the system to fall deeper, change faster, even trigger low-frequency load shedding, and the safe and stable operation of the system is threatened. In a large-scale power grid with continuously improved permeability, the range of a unit entering a low-penetration control mode can change along with the fault position, and besides the lack of active power, the integral frequency modulation capability of a new energy unit in the system can also show a more complex change rule according to different fault positions. Therefore, accurate calculation of the frequency response after a high proportion of new energy systems are subjected to large disturbances will become more complex. In the prior art, the system frequency response method considering that the fan actively participates in frequency modulation tends to carry out integral aggregation or simplified characterization on the response of distributed wind power, although the calculation efficiency is improved, the space dimension of fault disturbance spreading in a power grid is ignored, and the active power deficiency differentiation characteristics caused by different voltage drop degrees and active recovery rates at different fault positions are not comprehensively considered. Disclosure of Invention In order to overcome the defects of the prior art, the invention provides a system frequency response estimation method and system based on a fault position, which are used for constructing a system frequency response improvement model considering active power deficiency and frequency modulation capacity loss caused by the fault position and recovering differentiation characteristics, quantifying initial active power deficiency and frequency modulation capacity loss, and carrying out weighted aggregation to form the availability of equivalent frequency modulation capacity of the system by introducing a new energy station frequency modulation state switching coefficient so as to realize the differential correction of the fault position of the traditional frequency response model. To achieve the above object, one or more embodiments of the present invention provide the following technical solutions: in a first aspect, the present invention discloses a system frequency response estimation method based on fault location, including: constructing a new energy multi-operation state model, wherein the multi-operation state comprises a steady-state operation state, a fault ride-through state and a frequency adjustment state; Solving node voltage after faults on the state model based on superposition principle and iterative calculation, establishing a mapping model of a fault position and a low-penetration cluster, determining the voltage drop degree of a unit based on the mapping model to obtain an initial value of active power deficiency, comprehensively considering the initial value of active power deficiency and the difference of active recovery rate between stations at different fault positions, and calculating the total active power deficiency of a system level considering the difference of low-penetration characteristics of the stations; And (3) adopting a new energy station frequency modulation capability state switching coefficient, weighting and polymerizing to form a system equivalent frequency modulation capability availability, constructing a system frequency response model based on the frequency modulation capability difference caused by the fault position, and estimating the system frequency response by adopting the response model. In a second aspect, the present invention discloses a system frequency response estimation system based on fault location, comprising: The system comprises a state construction module, a cont