An active power distribution network voltage control method of energy storage virtual impedance

Abstract

The application discloses an active power distribution network voltage control method of energy storage virtual impedance, relates to the technical field of voltage control, and is used for solving the problem of excessive intervention or insufficient intervention of an energy storage system. The energy storage access node in a to-be-tested power distribution network region is called, real-time voltage data of each energy storage access node is collected, voltage diffusion state is analyzed, the energy storage access node in an abnormal diffusion state is marked, voltage flicker data and power flow change data of the marked energy storage access node are detected, an impedance adjustment direction is determined, an impedance adjustment amplitude is calculated, virtual impedance adjustment is implemented on an energy storage inverter, the reactive power output change amount of the energy storage inverter and the voltage out-of-limit subsiding time of the marked energy storage access node are detected, whether to stop the virtual impedance adjustment is judged according to the detection result, voltage rapid support is ensured, excessive intervention of the energy storage system is avoided, and the stability and reliability of active power distribution network voltage control are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of voltage control, and more particularly to an active power distribution network voltage control method of energy storage virtual impedance. BACKGROUND

[0002] In modern active power distribution networks, with the large-scale access of distributed energy storage, photovoltaic and wind power and other renewable energy sources, the problem of power distribution network voltage fluctuation is increasingly prominent, especially in high-penetration energy storage access areas, due to the uneven distribution of energy storage nodes and the influence of load fluctuation, local voltage may appear abnormal diffusion phenomenon, leading to voltage overrun, flicker and power flow fluctuation.

[0003] The prior art has the following disadvantages:

[0004] At present, the prior art mainly relies on traditional reactive power regulation, fixed impedance control or single-node energy storage regulation method, which is difficult to cope with local abnormal voltage diffusion and rapid voltage flicker, lacks real-time voltage state analysis of energy storage access nodes, impedance regulation direction and amplitude optimization and dynamic regulation strategy, leading to excessive intervention or insufficient intervention of energy storage system, voltage recovery is not timely, and the stability of the power distribution network is reduced, therefore, an active power distribution network voltage control method of energy storage virtual impedance is proposed.

[0005] The above information disclosed in the background section is only intended to enhance the understanding of the background of the present disclosure, and therefore it can include information that does not constitute the prior art known to those of ordinary skill in the art. SUMMARY

[0006] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide an active power distribution network voltage control method of energy storage virtual impedance, which uses a voltage diffusion identification method based on real-time voltage data analysis of energy storage access nodes, combines virtual impedance regulation direction and amplitude calculated by fusing voltage flicker data and power flow change data, and uses a dynamic regulation strategy based on the change amount of reactive power output of energy storage inverter and voltage overrun decay time to solve the problems raised in the above background.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme, an active power distribution network voltage control method of energy storage virtual impedance, comprising the following steps:

[0008] Step S1: In the energy storage access area to be measured in the power distribution network, the energy storage access nodes in the power distribution network to be measured are retrieved, the real-time voltage data of each energy storage access node is collected and the voltage diffusion state is analyzed, the energy storage access nodes in abnormal diffusion state are marked and the energy storage intervention is carried out;

[0009] Step S2: Before energy storage intervention, detect the voltage flicker data of the marked energy storage access node and set the impedance adjustment direction, collect the power flow change data of the marked energy storage access node, and calculate the impedance adjustment amplitude combined with the voltage flicker data;

[0010] Step S3: After retrieving the impedance adjustment direction and impedance adjustment amplitude, the marked energy storage access node is virtually adjusted, the evaluation period is set, the reactive power output change of the energy storage inverter is detected, and the voltage out-of-limit decay time of the marked energy storage access node is detected;

[0011] Step S4: Analyze the reactive power regulation characteristics using the reactive power output change, and analyze the voltage recovery stage of the marked energy storage access node combined with the voltage out-of-limit decay time and determine whether to stop the virtual impedance adjustment.

[0012] In a preferred embodiment, in step S1, in the to-be-tested power distribution network region of the energy storage access, the energy storage access nodes in the to-be-tested power distribution network region are retrieved;

[0013] A preset monitoring period is divided into multiple monitoring moments, and the voltage amplitude of the energy storage access node at each monitoring moment is obtained by the edge collection unit in the preset monitoring period, and the voltage amplitude is taken as real-time voltage data;

[0014] The voltage change intensity of the energy storage access node is calculated based on the real-time voltage data at each monitoring moment;

[0015] The sign result of the voltage change intensity is taken as the voltage change direction of the energy storage access node;

[0016] If the absolute value of the voltage change intensity of the current energy storage access node is greater than the preset voltage change threshold, the neighbor access node set of the current energy storage access node is retrieved through the power distribution network topology relationship library;

[0017] Conversely, the neighbor access node set of the current energy storage access node is not retrieved.

[0018] In a preferred embodiment, in step S1, if the voltage change direction of the energy storage access node in the neighbor access node set is the same as that of the current energy storage access node, the energy storage access node in the neighbor access node set is marked as a target adjacent node;

[0019] Conversely, the energy storage access nodes in the neighbor access node set are not marked;

[0020] The voltage change intensity whose voltage change intensity is greater than the preset voltage change threshold is marked;

[0021] The voltage diffusion index is calculated based on the marked voltage change intensity;

[0022] If the voltage diffusion index is greater than the preset voltage diffusion threshold, it is judged that the voltage diffusion state of the current energy storage access node is an abnormal diffusion state, and energy storage intervention is performed on the current energy storage access node;

[0023] Otherwise, it is judged that the voltage diffusion state of the current energy storage access node is a normal diffusion state.

[0024] In a preferred embodiment, in step S2, a preset statistical time is set, and a plurality of voltage instantaneous values of the marked energy storage access node are detected by the edge acquisition unit;

[0025] The voltage instantaneous values at adjacent time points are subtracted to obtain voltage difference values, the voltage difference values greater than a preset voltage difference threshold are counted as voltage sudden change quantities, and the voltage flicker data is calculated based on the voltage sudden change quantities;

[0026] The target voltage reference value of the marked energy storage access node is obtained through the voltage setting parameter table, and if the real-time voltage data of the current marked energy storage access node is greater than the target voltage reference value, the impedance adjustment direction is set to a value of -1; otherwise, the impedance adjustment direction is set to a value of 1.

[0027] In a preferred embodiment, in step S2, the associated line set of the marked energy storage access node is called through the dispatch monitoring interface, including each associated line connected to the energy storage access node;

[0028] The power measurement value of each associated line in the associated line set is obtained;

[0029] If the signs of the power measurement values at adjacent time points are inconsistent within the preset statistical time, it is recorded as a flow direction change event;

[0030] Otherwise, it is not a flow direction change event;

[0031] The number of flow direction change events of each associated line is counted as the flow direction change number, and the ratio of the flow direction change number to the preset statistical time is taken as the flow direction change frequency. The flow direction change frequency is used to calculate the power flow change data of the marked energy storage access node;

[0032] The impedance adjustment amplitude is calculated by integrating the power flow change data and the voltage flicker data.

[0033] In a preferred embodiment, in step S3, the original virtual impedance of the energy storage inverter is called, and then the target virtual impedance value is calculated according to the impedance adjustment direction and the impedance adjustment amplitude, and the expression is:

[0034] ;

[0035] Wherein, target virtual impedance value, original virtual impedance value, impedance adjustment direction, taking +1 or -1, impedance adjustment amplitude;

[0036] In each control cycle, the output current of the energy storage inverter is collected, and the target virtual impedance value is multiplied by the output current cycle by cycle to calculate the virtual voltage drop amount;

[0037] The virtual voltage drop amount is deducted from the static voltage reference value of the energy storage inverter to obtain an updated voltage reference value after virtual impedance adjustment.

[0038] In a preferred embodiment, in step S3, the current loop controller in the energy storage inverter generates a pulse width modulation signal in real time based on the updated voltage reference value, so that the equivalent impedance of the actual output port of the inverter is consistent with the target virtual impedance value, thereby realizing real-time adjustment of the virtual impedance of the marked energy storage access node;

[0039] An evaluation period is set for continuous monitoring of the reactive power output of the energy storage inverter and the voltage recovery state of the marked energy storage access node during the virtual impedance adjustment;

[0040] The reactive power output value of the energy storage inverter at the start time of the evaluation period and the reactive power output value at the end time are recorded, and the difference between the two is calculated as the reactive power output change amount;

[0041] During the evaluation period, the real-time voltage curve of the marked energy storage access node is recorded based on the node voltage sampling device at the same sampling frequency, and the voltage out-of-limit subsidence time is obtained;

[0042] The voltage out-of-limit subsidence time is defined as the time taken for the node voltage to recover from outside the out-of-limit threshold to within the rated voltage tolerance and remain unchanged.

[0043] In a preferred embodiment, in step S4, based on the reactive power output change amount in the evaluation period, the reactive power adjustment feature is calculated, which is defined as the ratio of the average change rate of the reactive power output change amount in the evaluation period to the reactive power fluctuation level, and the specific calculation is:

[0044] ;

[0045] wherein, reactive power adjustment feature, evaluation period length, reactive power output change amount, reactive power fluctuation level, i.e. the standard deviation of the reactive power output change amount;

[0046] The recovery speed of the node voltage in the evaluation period is calculated based on the voltage out-of-limit extinction time, and the voltage recovery speed is obtained.

[0047] In a preferred embodiment, in step S4, the reactive power regulation characteristic is multiplied by the voltage recovery speed to obtain a regulation effect coefficient;

[0048] When the regulation effect coefficient is greater than or equal to the preset recovery shutdown threshold, it is determined that the node voltage is still in the observable recovery stage, and the current virtual impedance regulation is continued to be maintained;

[0049] When the regulation effect coefficient is less than the preset recovery shutdown threshold, it is determined that the node voltage recovery has been completed, and the virtual impedance regulation is stopped to avoid unnecessary inverter reactive power fluctuation.

[0050] Technical effects and advantages of the present application:

[0051] The present application retrieves the energy storage access node in the power distribution network area to be tested, collects real-time voltage data of each energy storage access node and analyzes the voltage diffusion state, marks the energy storage access node in the abnormal diffusion state, detects the voltage flicker data and power flow change data of the marked energy storage access node, determines the impedance regulation direction and calculates the impedance regulation amplitude, implements virtual impedance regulation on the energy storage inverter, detects the reactive power output change of the energy storage inverter and the voltage out-of-limit extinction time of the marked energy storage access node, and judges whether to stop the virtual impedance regulation according to the detection result, so as to ensure the rapid voltage support and avoid the excessive intervention of the energy storage system, and improve the stability and reliability of the active power distribution network voltage control. BRIEF DESCRIPTION OF DRAWINGS

[0052] Fig. 1 The implementation flowchart of the active power distribution network voltage control method of the energy storage virtual impedance of the present application.

[0053] Fig. 2 The step schematic diagram of the active power distribution network voltage control method of the energy storage virtual impedance of the present application. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0055] The application collects real-time voltage data of each energy storage access node and analyzes voltage diffusion state by calling energy storage access nodes in the to-be-tested power distribution network region, marks energy storage access nodes in abnormal diffusion state, detects voltage flicker data and power flow change data of the marked energy storage access nodes, determines impedance adjustment direction and calculates impedance adjustment amplitude, implements virtual impedance adjustment on the energy storage inverter, detects reactive power output change of the energy storage inverter and voltage out-of-limit decay time of the marked energy storage access nodes, and judges whether to stop virtual impedance adjustment according to the detection result, so as to ensure rapid voltage support while avoiding excessive intervention of the energy storage system.

[0056] Embodiment 1, as shown in Figs. 1-2 An active power distribution network voltage control method of energy storage virtual impedance includes the following steps:

[0057] Step S1: In the to-be-tested power distribution network region with energy storage access, call energy storage access nodes in the to-be-tested power distribution network region, collect real-time voltage data of each energy storage access node and analyze voltage diffusion state, mark energy storage access nodes in abnormal diffusion state and perform energy storage intervention.

[0058] Step S2: Before energy storage intervention on the marked energy storage access node, detect voltage flicker data of the marked energy storage access node and set impedance adjustment direction, collect power flow change data of the marked energy storage access node, and calculate impedance adjustment amplitude in combination with the voltage flicker data.

[0059] Step S3: After calling the energy storage inverter, input impedance adjustment direction and impedance adjustment amplitude to the marked energy storage access node for virtual impedance adjustment, set an evaluation period, detect reactive power output change of the energy storage inverter and voltage out-of-limit decay time of the marked energy storage access node.

[0060] Step S4: Analyze reactive power regulation characteristics by using the reactive power output change, analyze voltage recovery stage of the marked energy storage access node in combination with the voltage out-of-limit decay time, and judge whether to stop virtual impedance adjustment.

[0061] The specific implementation is as follows:

[0062] In step S1, during the operation of the active power distribution network, due to distributed power output fluctuation, load change and frequent reconstruction of power flow structure, node voltage presents the characteristics of diffusion from local to periphery, short-term and local transient fluctuation is easily misjudged as abnormal state needing adjustment, leading to frequent action or improper intervention of the energy storage.

[0063] In the to-be-tested power distribution network region with energy storage access, call energy storage access nodes in the to-be-tested power distribution network region, the energy storage access node refers to a node connected to the to-be-tested power distribution network region through an energy storage inverter, and the voltage state reflects the operation in the range electrically adjacent to the energy storage grid-connected point.

[0064] A preset monitoring period is divided into multiple monitoring time points, and the voltage amplitude of the energy storage access node at each monitoring time point is obtained by the edge acquisition unit within the preset monitoring period, and the voltage amplitude is taken as real-time voltage data;

[0065] The real-time voltage data at the current monitoring time point is subtracted from the real-time voltage data at the previous monitoring time point to obtain a voltage change amount, and the average value of the voltage change amount is taken as the voltage change intensity of the energy storage access node;

[0066] The sign result of the voltage change intensity is taken as the voltage change direction of the energy storage access node. For example, when the voltage change intensity is positive, it indicates that the voltage of the corresponding energy storage access node changes in the upward direction; when the voltage change intensity is negative, it indicates that the voltage of the corresponding energy storage access node changes in the downward direction.

[0067] The greater the voltage change intensity, the more intense the voltage fluctuation of the energy storage access node within the current monitoring period, the higher the voltage abnormality degree, and the greater the possibility of regional diffusion risk; the smaller the voltage change intensity, the more stable the voltage change of the energy storage access node, and the relatively stable voltage operating state;

[0068] If the absolute value of the voltage change intensity of the current energy storage access node is greater than a preset voltage change threshold, the neighbor access node set of the current energy storage access node is retrieved through the power distribution network topology relationship library;

[0069] On the contrary, the neighbor access node set of the current energy storage access node is not retrieved;

[0070] The neighbor access node set refers to the node set that has a direct electrical connection relationship with the current energy storage access node in the power distribution network topology structure, including each energy storage access node adjacent to the current energy storage access node;

[0071] If the voltage change direction of the energy storage access node in the neighbor access node set is the same as that of the current energy storage access node, the energy storage access node in the neighbor access node set is marked as a target adjacent node;

[0072] On the contrary, the energy storage access nodes in the neighbor access node set are not marked;

[0073] The voltage change intensity of the target adjacent node whose voltage change intensity is greater than the preset voltage change threshold is marked;

[0074] The average value of the absolute value of the marked voltage change intensity is taken as the adjacent voltage diffusion intensity;

[0075] The ratio result of the absolute value of the voltage change intensity of the current energy storage access node to the adjacent voltage diffusion intensity is taken as the voltage diffusion index;

[0076] The voltage diffusion index is compared with a preset voltage diffusion threshold to analyze the voltage diffusion state:

[0077] If the voltage diffusion index is greater than the preset voltage diffusion threshold, it is determined that the voltage diffusion state of the current energy storage access node is an abnormal diffusion state;

[0078] On the contrary, it is determined that the voltage diffusion state of the current energy storage access node is a normal diffusion state;

[0079] When the voltage diffusion state of the current energy storage access node is an abnormal diffusion state, the current energy storage access node is marked and energy storage intervention is performed. The energy storage intervention refers to adjusting the energy storage inverter corresponding to the energy storage access node, so that the energy storage system participates in the control behavior of the node voltage regulation process, and the energy storage system is used for voltage regulation.

[0080] It should be noted that the preset monitoring period can be set according to the operation characteristics of the to-be-measured power distribution network region; the edge collection unit is used for real-time collection of voltage, current and other operation parameters of the energy storage access node; the preset voltage change threshold can be set according to the voltage allowable fluctuation range, the power quality standard or the historical operation data statistical result; the power distribution network topology relationship library is used for storing the electrical connection relationship between each node in the power distribution network; the preset voltage diffusion threshold can be set according to the voltage abnormal diffusion scale, the voltage out-of-limit occurrence probability or the energy storage intervention effect evaluation result in the historical operation process.

[0081] In step S2, before the energy storage intervention of the marked energy storage access node, a preset statistical time is set, the edge collection unit detects a plurality of voltage instantaneous values of the marked energy storage access node, the voltage instantaneous values of adjacent time points are subtracted to obtain voltage difference values, and the voltage difference values greater than the preset voltage difference threshold are counted as the voltage sudden change number;

[0082] The ratio of the voltage sudden change number to the total number of voltage difference values in the preset statistical time is taken as the voltage flicker data;

[0083] The target voltage reference value of the marked energy storage access node is obtained through the voltage setting parameter table. The target voltage reference value refers to the target voltage level of the stable operation of the marked energy storage access node;

[0084] If the real-time voltage data of the current marked energy storage access node is greater than the target voltage reference value, it is determined that the impedance adjustment direction is the adjustment direction of inhibiting voltage upward deviation, and the impedance adjustment direction is set to the value -1; on the contrary, it is determined that the impedance adjustment direction is the adjustment direction of inhibiting voltage downward deviation, and the impedance adjustment direction is set to the value 1;

[0085] The voltage flicker data reflects the frequency and intensity of the voltage rapid fluctuation of the energy storage access node in the statistical time. The greater the voltage flicker data is, the more the times of the rapid change of the voltage instantaneous value and the more frequent the voltage fluctuation, and the more unstable the node voltage operation state is;

[0086] The associated line set of the energy storage access node is called through the dispatch monitoring interface. The associated line set refers to the line set with the energy storage access node as an endpoint and having a direct electrical connection relationship with the energy storage access node, including each associated line connected with the energy storage access node;

[0087] The power measurement value of each associated line in the associated line set is obtained. The power measurement value reflects the transmission state of the electric energy between the energy storage access node and the associated line. When the power measurement value is greater than 0, it indicates that the electric energy is output from the energy storage access node to the corresponding associated line. When the power measurement value is less than 0, it indicates that the electric energy flows into the energy storage access node from the corresponding associated line;

[0088] In the preset statistical time, the sign change of the power measurement value of each associated line is counted, and the power flow direction of the associated line is analyzed;

[0089] If the signs of the power measurement values of adjacent time points are different, it is recorded as a flow direction change event;

[0090] On the contrary, it is not a flow direction change event;

[0091] The number of flow direction change events of each associated line is counted as the flow direction change number, and the ratio of the flow direction change number to the preset statistical time is taken as the flow direction change frequency;

[0092] The average value of the flow direction change frequency of each associated line is taken to obtain the power flow change data of the energy storage access node marked;

[0093] The greater the power flow change data is, the higher the frequency of the power flow direction switching in the multiple associated lines related to the energy storage access node marked is, the more frequent the electric energy transmission path adjustment is, and the power flow structure around the node is in an unstable state;

[0094] The voltage flicker coefficient and the power flow change coefficient are obtained after the voltage flicker data and the power flow change data are standardized respectively;

[0095] The comprehensive disturbance intensity is calculated based on the voltage flicker coefficient and the power flow change coefficient , wherein, is the comprehensive disturbance intensity, is the voltage flicker coefficient, is the power flow change coefficient, is the preset adjustment weight;

[0096] The greater the comprehensive disturbance intensity is, the more frequent the node voltage disturbance is and the more unstable the power flow structure is, and the energy storage system needs to adopt stronger virtual impedance adjustment to suppress the spread of voltage anomaly. The smaller the comprehensive disturbance intensity is, the weaker the node operation disturbance is, and the virtual impedance adjustment can be correspondingly reduced to avoid over intervention of the energy storage.

[0097] The impedance adjustment amplitude range is called from the energy storage control strategy library, and the impedance adjustment amplitude allowable range is used to limit the safe upper and lower limits of the virtual impedance adjustment.

[0098] The impedance adjustment amplitude is calculated based on the impedance adjustment amplitude range and the comprehensive disturbance intensity: ;

[0099] wherein, is the impedance adjustment amplitude, is the lower limit value of the impedance adjustment amplitude range, is the upper limit value of the impedance adjustment amplitude range, is the comprehensive disturbance intensity.

[0100] It should be noted that the preset statistical time can be set according to the time scale of the fluctuation of the distributed power output in the to-be-tested distribution network region or the data refresh period of the scheduling system; the voltage setting parameter table is a parameter configuration table used to store the target voltage reference values of the energy storage access node under different operating conditions; the scheduling monitoring interface is an operating data acquisition interface provided by the distribution network scheduling system, which is used to acquire the power measurement values of each node and line in the distribution network; the preset adjustment weight can be set according to the voltage stability requirement or the energy storage response characteristic; the standardization processing mode includes but is not limited to the standard linear transformation based on interval scaling, the Z-Score standardization method based on statistics or the normalization method based on a nonlinear mapping function, and the application method of the standardization processing is not described here; the energy storage control strategy library is a control strategy set used to store the virtual impedance adjustment strategies and adjustment amplitude ranges of the energy storage inverters.

[0101] In step S3, the impedance adjustment direction and the impedance adjustment amplitude are read in each control period, and the equivalent output impedance of the energy storage inverter is increased or decreased according to the sign of the impedance adjustment direction, and the change amount of the equivalent output impedance is quantitatively set according to the numerical value of the impedance adjustment amplitude. Specifically, the original virtual impedance of the energy storage inverter is called, and the target virtual impedance value is calculated according to the impedance adjustment direction and the impedance adjustment amplitude, and the expression is:

[0102] ;

[0103] wherein, is the target virtual impedance value, is the original virtual impedance, is the impedance adjustment direction, which is +1 or -1, to adjust the amplitude of impedance.

[0104] After obtaining the target virtual impedance value, the output current of the energy storage inverter is collected in each control cycle, and the target virtual impedance value is multiplied by the output current cycle by cycle to calculate the virtual voltage drop value:

[0105]

[0106] wherein, the virtual voltage drop value, the target virtual impedance value, the output current.

[0107] The virtual voltage drop value is a quantitative voltage compensation value, reflecting the equivalent impedance effect that the energy storage inverter should superimpose on the voltage reference value in the current control cycle.

[0108] The virtual voltage drop value is deducted from the static voltage reference value of the energy storage inverter to obtain an updated voltage reference value after virtual impedance adjustment:

[0109] wherein, the updated voltage reference value, the static voltage reference value, the virtual voltage drop value.

[0110] It should be noted that the static voltage reference value is used to represent the reference output voltage instruction of the energy storage inverter when the virtual impedance adjustment is not triggered, which is derived from the setting of the grid-connected point rated voltage by the voltage outer loop controller of the energy storage inverter.

[0111] The current loop controller in the energy storage inverter generates a pulse width modulation signal in real time based on the updated voltage reference value, so that the equivalent impedance of the actual output port of the inverter is consistent with the target virtual impedance value. In the control cycle, the reactive current output by the energy storage inverter changes quantitatively due to the change of the equivalent impedance, thereby directly acting on the voltage offset of the marker energy storage access node.

[0112] Through the above cycle-by-cycle calculation and adjustment process, the virtual impedance of the marker energy storage access node is adjusted in real time, so that the equivalent electrical characteristics of the inverter participate in the rapid support process of the node voltage under the control of quantifiable impedance parameters.

[0113] It should be noted that the current loop controller is used for fast closed-loop adjustment of the output current of the energy storage inverter, and is a basic control unit in the internal control system of the inverter.

[0114] An evaluation period is set to continuously monitor the reactive output of the energy storage inverter and the voltage recovery state of the marker energy storage access node during the virtual impedance adjustment. ​​

[0115] Subsequently, reactive power output data of the energy storage inverter is acquired at a sampling frequency of the inverter control cycle throughout the evaluation period, and the reactive power output value at the start time and the reactive power output value at the end time of the evaluation period are recorded respectively, and the difference between the two is calculated as the reactive power output change, which is used to quantify the degree of change of the reactive power support capability of the energy storage inverter caused by the virtual impedance adjustment, and reflects the strength of the reactive current response caused by the target virtual impedance value.

[0116] At the same time, the real-time voltage curve of the energy storage access node is recorded based on the node voltage sampling device at the same sampling frequency within the evaluation period, and the duration of the node voltage out-of-limit state is determined by comparing the deviation change of the node voltage and the rated voltage allowable range. The voltage out-of-limit recovery time is defined as the time experienced by the node voltage from outside the out-of-limit threshold to within the rated voltage allowable range and remains unchanged, which is derived from the time difference between the voltage out-of-limit start time and the voltage recovery completion time.

[0117] The voltage out-of-limit recovery time is used to quantify the degree of influence of the virtual impedance adjustment on the node voltage recovery speed, and can reflect the suppression effect of the energy storage inverter on the node voltage deviation during the disturbance.

[0118] By synchronously detecting the reactive power output change and the voltage out-of-limit recovery time within the evaluation period, the system running state after the virtual impedance adjustment can be evaluated based on the two quantitative parameters, and complete data support is provided for subsequent judgment of whether the voltage recovery phase meets the condition of stopping adjustment.

[0119] It should be noted that the node voltage sampling device is a basic measurement unit for continuous and fixed-frequency acquisition of the voltage of the energy storage access node, which is used to obtain real-time change information of the node voltage in the embodiment.

[0120] In step S4, based on the reactive power output change within the evaluation period, the reactive power regulation feature is calculated, which is defined as the ratio of the average change rate of the reactive power output change within the evaluation period to the reactive power fluctuation level, and the specific calculation is:

[0121] ;

[0122] Wherein, is the reactive power regulation feature, is the evaluation period length, is the reactive power output change, is the reactive power fluctuation level, i.e. the standard deviation of the reactive power output change.

[0123] The reactive power regulation feature is used to quantify the persistence and stability of the virtual impedance regulation on the reactive power support, and the greater the reactive power regulation feature, the more significant and directionally clear the regulation trend of the reactive power output in the evaluation period; the smaller the reactive power regulation feature, the more the reactive power change is composed of random fluctuations, and the weaker the regulation effect caused by the virtual impedance.

[0124] After obtaining the reactive power regulation feature and the voltage excursion extinction time, the voltage recovery state of the energy storage access node is analyzed, and it is determined whether to stop the virtual impedance regulation.

[0125] Specifically, the voltage recovery speed of the node voltage in the evaluation period is calculated based on the voltage excursion extinction time, and the voltage recovery speed is obtained, and the specific calculation expression is:

[0126]

[0127] wherein, is the voltage recovery speed, is the voltage excursion extinction time, is the voltage difference of the node voltage from the outside of the excursion threshold to the boundary of the rated voltage allowable range.

[0128] The voltage recovery speed reflects the recovery efficiency of the node voltage under the action of the virtual impedance regulation.

[0129] The regulation effect coefficient is obtained by jointly quantifying the reactive power regulation feature and the voltage recovery speed to evaluate the contribution degree of the current virtual impedance regulation to the voltage recovery, and the specific calculation formula of the regulation effect coefficient is:

[0130]

[0131] wherein, is the regulation effect coefficient, is the reactive power regulation feature, is the voltage recovery speed.

[0132] When the regulation effect coefficient is greater than or equal to the preset recovery shutdown threshold, it indicates that the virtual impedance regulation not only causes a significant reactive power regulation trend, but also promotes the node voltage to recover to the rated voltage allowable range at a high speed, and the energy storage access node is in an effective recovery stage, and it is determined that the node voltage is still in an observable recovery stage, and the current virtual impedance regulation is continued to be maintained;

[0133] When the regulation effect coefficient is less than the preset recovery shutdown threshold, it indicates that the reactive power regulation effect is weakened and the voltage recovery efficiency is significantly decreased, and the marginal improvement effect of the virtual impedance regulation is insufficient, and it is determined that the node voltage recovery has been completed, and the virtual impedance regulation is stopped to avoid unnecessary inverter reactive power fluctuations.

[0134] ​​It should be noted that the setting of the preset recovery shutdown threshold is obtained by historical operation data, the reactive power output change sequence and the voltage out-of-limit subsiding time sequence of the marker energy storage access node under typical disturbance conditions are collected, the corresponding reactive power regulation characteristics and voltage recovery speed are calculated, and the statistical distribution of the comprehensive regulation effect coefficient is formed according to the two, and according to the statistical distribution, the lower quantile (for example, the 10th percentile or the 5th percentile) of the regulation effect coefficient is selected as the preset recovery shutdown threshold.

[0135] Finally, it should be noted that in this document, the terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between such entities or operations.

[0136] Moreover, the terms "include", "have" or any other variant thereof are intended to cover non-exclusive inclusions, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "including a" does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0137] In this document, the singular forms "a", "an" and "the" can also include plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "include", "have" or "comprise" or the like specify the presence of stated features, integers, steps, operations, components, parts or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, parts or combinations thereof.

[0138] The various embodiments in the specification are described in a progressive manner, each embodiment focusing on the differences from other embodiments, and the various embodiments can be combined as needed, and the same and similar parts refer to each other.

[0139] The above description of the disclosed embodiments enables those skilled in the art to implement or use the various modifications of the embodiments of the present application, and it will be apparent to those skilled in the art that various modifications can be made to the embodiments of the present application without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An active distribution network voltage control method with energy storage virtual impedance, characterized in that: Includes the following steps: Step S1: In the distribution network area to be tested where energy storage is connected, retrieve the energy storage access nodes in the distribution network area to be tested, collect the real-time voltage data of each energy storage access node and analyze the voltage diffusion status, mark the energy storage access nodes in the abnormal diffusion status and intervene in energy storage. Step S2: Before energy storage intervention on the marked energy storage access node, detect the voltage flicker data of the marked energy storage access node and set the impedance adjustment direction, collect the power flow change data of the marked energy storage access node, and calculate the impedance adjustment amplitude by combining the voltage flicker data. Step S3: Request the input impedance adjustment direction and amplitude of the energy storage inverter to perform virtual impedance adjustment on the marked energy storage access node, set the evaluation cycle, and detect the reactive power output change of the energy storage inverter and the voltage over-limit decay time of the marked energy storage access node. Step S4: Analyze the reactive power regulation characteristics using the reactive power output change, and combine the voltage over-limit decay time to analyze and mark the voltage recovery stage of the energy storage access node and determine whether to stop virtual impedance regulation.

2. The active distribution network voltage control method for energy storage virtual impedance according to claim 1, characterized in that: In step S1, in the distribution network area to be tested where energy storage is connected, the energy storage access nodes in the distribution network area to be tested are retrieved, and the real-time voltage data of each energy storage access node is collected. The monitoring period is preset and divided into multiple monitoring times. Within the preset monitoring period, the voltage amplitude of the energy storage access node at each monitoring time is obtained through the edge acquisition unit, and the voltage amplitude is used as real-time voltage data. The voltage change intensity of the energy storage access node is calculated based on the real-time voltage data at each monitoring time. The sign of the voltage change intensity is taken as the direction of the voltage change at the energy storage access node; Determine whether the absolute value of the voltage change intensity of the current energy storage access node is greater than the preset voltage change threshold. If the absolute value of the voltage change intensity of the current energy storage access node is greater than the preset voltage change threshold, retrieve the set of neighboring access nodes of the current energy storage access node through the distribution network topology database. Conversely, the set of neighboring access nodes of the current energy storage access node is not retrieved.

3. The active distribution network voltage control method for energy storage virtual impedance according to claim 2, characterized in that: In step S1, the voltage diffusion state of the energy storage access node is analyzed, and energy storage access nodes in abnormal diffusion state are marked and energy storage intervention is performed. Determine whether the voltage change direction of the energy storage access node in the neighboring access node set is the same as that of the current energy storage access node. If the voltage change direction of the energy storage access node in the neighboring access node set is the same as that of the current energy storage access node, then mark the energy storage access node in the neighboring access node set as the target neighboring node. Conversely, energy storage access nodes in the neighboring access node set are not marked; The voltage change intensity of the target's adjacent nodes that exceeds the preset voltage change threshold is marked; The voltage diffusion index is calculated by marking the intensity of voltage change. Determine whether the voltage diffusion index is greater than the preset voltage diffusion threshold. If the voltage diffusion index is greater than the preset voltage diffusion threshold, determine that the voltage diffusion state of the current energy storage access node is an abnormal diffusion state, and perform energy storage intervention on the current energy storage access node. Conversely, the voltage diffusion state of the current energy storage access node is determined to be a normal diffusion state.

4. The active distribution network voltage control method for energy storage virtual impedance according to claim 2, characterized in that: In step S2, before energy storage intervention is performed on the marked energy storage access node, the voltage flicker data of the marked energy storage access node is detected and the impedance adjustment direction is set. The system uses a preset statistical time frame to detect and mark multiple instantaneous voltage values ​​of the energy storage access node via an edge acquisition unit. The voltage difference is obtained by taking the absolute value of the difference between the instantaneous voltage values ​​at adjacent times. The voltage difference values ​​that are greater than the preset voltage difference threshold are counted as the number of voltage fluctuations. The voltage flicker data is calculated based on the number of voltage fluctuations. The target voltage reference value of the marked energy storage access node is obtained through the voltage setting parameter table. If the real-time voltage data of the current marked energy storage access node is greater than the target voltage reference value, the impedance adjustment direction is set to the value -1. Conversely, the impedance adjustment direction is set to the value 1.

5. The active distribution network voltage control method for energy storage virtual impedance according to claim 4, characterized in that: In step S2, power flow change data of the marked energy storage access nodes are collected, and the impedance adjustment amplitude is calculated by combining the voltage flicker data. The set of associated lines of the marked energy storage access node is retrieved through the scheduling and monitoring interface, including each associated line connected to the energy storage access node. For each associated line in the associated line set, obtain its power measurement value; If the signs of the power measurement values ​​at adjacent times are inconsistent within the preset statistical time period, it is recorded as a flow direction change event. Conversely, it is not considered a flow change event; The number of flow direction change events for each associated line is counted as the flow direction change count. The ratio of the flow direction change count to the preset statistical time is used as the flow direction change frequency. The flow direction change frequency is used to calculate the power flow change data of the marked energy storage access node. The impedance adjustment range is calculated by combining power flow change data and voltage flicker data.

6. The active distribution network voltage control method for energy storage virtual impedance according to claim 1, characterized in that: In step S3, the direction and magnitude of the input impedance adjustment of the energy storage inverter are retrieved to perform virtual impedance adjustment on the marked energy storage access node. The original virtual impedance of the energy storage inverter is retrieved, and the target virtual impedance value is calculated based on the impedance adjustment direction and magnitude. The expression is as follows: ； in, The target virtual impedance value, For the original virtual impedance, This indicates the direction of impedance adjustment, with a value of +1 or -1. For impedance adjustment amplitude; The output current of the energy storage inverter is collected in each control cycle, and the target virtual impedance value is multiplied by the output current cycle by cycle to calculate the virtual voltage drop. The virtual voltage drop is subtracted from the static voltage reference value of the energy storage inverter to obtain the updated voltage reference value after virtual impedance adjustment.

7. The active distribution network voltage control method for energy storage virtual impedance according to claim 1, characterized in that: In step S3, an evaluation cycle is set to detect the reactive power output change of the energy storage inverter and mark the voltage over-limit decay time of the energy storage access node; The current loop controller in the energy storage inverter generates a pulse width modulation signal in real time based on the updated voltage reference value, so that the equivalent impedance of the actual output port of the inverter is consistent with the target virtual impedance value, thereby realizing the real-time adjustment of the virtual impedance of the marked energy storage access node. An evaluation cycle is set to continuously monitor the reactive power output of the energy storage inverter and the voltage recovery status of the marked energy storage access node during virtual impedance regulation. Record the reactive power output value of the energy storage inverter at the beginning and end of the evaluation cycle, and calculate the difference between the two as the reactive power output change. During the evaluation period, the real-time voltage curves of the marked energy storage access nodes are recorded at the same sampling frequency using the node voltage sampling device, and the voltage over-limit decay time is obtained. The voltage over-limit decay time is defined as the time it takes for the node voltage to recover from outside the over-limit threshold to within the rated voltage allowable range and remain unchanged.

8. The active distribution network voltage control method for energy storage virtual impedance according to claim 1, characterized in that: In step S4, reactive power regulation characteristics are analyzed using reactive power output variation. Based on the reactive power output variation within the assessment period, reactive power regulation characteristics are calculated. The reactive power regulation characteristics are defined as the ratio of the average rate of change of reactive power output variation within the assessment period to the reactive power fluctuation level. Specifically, the calculation is as follows: ； in, It is a reactive power regulation characteristic. To assess the duration of the evaluation period, This represents the change in reactive power output. This refers to the reactive power fluctuation level, i.e., the standard deviation of the reactive power output variation. The voltage recovery rate is obtained by calculating the node voltage recovery rate within the evaluation period based on the voltage over-limit decay time.

9. The active distribution network voltage control method for energy storage virtual impedance according to claim 1, characterized in that: In step S4, the reactive power regulation characteristics are combined with the voltage recovery rate analysis to mark the voltage recovery stage of the energy storage access node and determine whether to stop virtual impedance regulation. The regulation effect coefficient is obtained by multiplying the reactive power regulation characteristic by the voltage recovery speed; When the regulation effect coefficient is greater than or equal to the preset recovery shutdown threshold, it is determined that the node voltage is still in the observable recovery stage, and the current virtual impedance regulation is maintained. When the regulation effect coefficient is less than the preset recovery shutdown threshold, it is determined that the node voltage recovery has been completed, and the virtual impedance regulation is stopped to avoid unnecessary inverter reactive power fluctuations.

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