High-permeability photovoltaic transformer area voltage main and distribution collaborative grading treatment method and system

Abstract

The invention discloses a high-permeability photovoltaic transformer area voltage main and distribution collaborative grading treatment method and system. The method comprises the steps that high-permeability photovoltaic transformer area out-of-limit scenes are classified; if the condition that the voltage of the distribution transformer gateway exceeds the upper limit in a piece is judged, a cooperative treatment method of bus voltage time-sharing adjustment, distribution transformer gear adjustment and low-voltage capacitor time-sharing input is adopted in sequence; if it is judged that the user voltage is in a piece-of-piece out-of-limit scene, a cooperative treatment method of distribution transformer gear adjustment and low-voltage capacitor time-sharing input is adopted in sequence; if it is judged that the voltage of the photovoltaic user severely exceeds the upper limit scene, a photovoltaic inverter adjusting method is adopted; and if a photovoltaic user voltage bidirectional out-of-limit scene is judged, a cooperative treatment method of photovoltaic inverter adjustment, low-voltage capacitor time-sharing input and distributed SVG adjustment or transformer area energy storage or low-voltage flexible direct-current interconnection is adopted in sequence. A main network and distribution network cooperative governance method is provided, the problem that the voltage of the distribution network fluctuates greatly is effectively solved, and the photovoltaic bearing capacity and the reactive voltage regulation capacity of the distribution network are improved.

Description

Technical Field

[0001] This invention belongs to the field of distribution network voltage management technology. It relates to a method and system for coordinated hierarchical management of voltage in high-penetration photovoltaic distribution areas, which is particularly suitable for managing large voltage fluctuations and serious over-limit problems of users in photovoltaic distribution areas. Background Technology

[0002] With the continuous growth of distributed photovoltaic (PV) grid connection, a large number of residential PV systems adopt the "full grid connection" model, connecting to the rural distribution network locally via low-voltage public distribution transformers. The overall load rate of rural low-voltage transformer areas is relatively low, making it difficult for the load within these areas to absorb the PV power generation locally, leading to significant backfeeding of active power. This large-scale backfeeding of active power from distributed PV alters the inherent characteristics of traditional unidirectional radial power supply in distribution networks, causing significant changes in the direction and distribution characteristics of power flow. This results in frequent voltage exceeding the upper limit on the user side, and even voltage fluctuations exceeding 30V within a single day, directly impacting residential electricity safety.

[0003] Publication No. CN 117650565 A discloses a comprehensive method, device, and equipment for managing grid-connected voltage exceedance in distributed photovoltaic (PV) systems. This method adjusts the reactive and active power outputs of each distributed PV inverter within the distribution area, tests the voltage change at the grid connection point to assess its voltage sensitivity, and determines the reactive and active power outputs of each inverter based on its grid connection point voltage sensitivity, thus achieving comprehensive management of grid-connected voltage exceedance in low-voltage distributed PV systems within the distribution area. However, this method only addresses voltage exceedance, essentially representing a single-measure approach, and its effectiveness in addressing significant voltage fluctuations in the distribution network is limited. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas, proposing a method for coordinated management of the main grid and distribution grid, effectively solving the problem of large voltage fluctuations in the distribution grid, and improving the photovoltaic carrying capacity and reactive power regulation capability of the distribution grid.

[0005] The technical solution to achieve the purpose of this invention is as follows: A method for coordinated and hierarchical management of voltage in high-penetration photovoltaic power distribution areas includes the following steps: The scenarios of high-penetration photovoltaic (PV) distribution areas exceeding the limit are classified into: distribution transformer gate voltage exceeding the limit for a large area, user voltage exceeding the limit for a large area, PV user voltage severely exceeding the limit, and PV user voltage exceeding the limit in both directions. If it is determined that the voltage at the distribution transformer gate exceeds the upper limit in a large area, a coordinated management method of time-sharing adjustment of bus voltage, distribution transformer tap adjustment, and time-sharing connection of low-voltage capacitors shall be adopted in sequence. If it is determined that the user voltage exceeds the limit in a large area, a coordinated management method of adjusting the distribution transformer level and time-sharing the low-voltage capacitors will be adopted in sequence. If it is determined that the voltage of the photovoltaic user is seriously exceeding the upper limit, the photovoltaic inverter adjustment method shall be adopted. If the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, a coordinated governance approach will be adopted in sequence, including photovoltaic inverter regulation, time-sharing connection of low-voltage capacitors, and distributed SVG regulation or distribution area energy storage or low-voltage flexible DC interconnection.

[0006] In the preferred technical solution, before classifying the scenarios of exceeding the limits in high-penetration photovoltaic power stations, the following is also included: Photovoltaic penetration rate P:

[0007] Wherein: S PV S represents the total installed capacity of photovoltaic power in the distribution area. trans For distribution transformer capacity; If P > threshold, it indicates that the area is a high-penetration photovoltaic area.

[0008] In the preferred technical solution, the method for determining the scenario where the distribution transformer switching voltage exceeds the upper limit includes: Based on the connection relationship between the substation, distribution line, and distribution transformer, the distribution transformer cutoff voltage U within the power supply range of the substation and distribution line is obtained. trans-j , j For the coordinate variable index, if U trans-j >U trans-up This indicates that the transformer has a voltage exceeding the upper limit. trans-up The threshold for voltage rise at the distribution transformer cut-off point; The number N of transformers with voltage exceeding the upper limit within the power supply range of this substation and distribution line was statistically determined. sub N line ; If N sub ≥threshold or N line If the voltage exceeds the threshold, it is determined that there is a scenario where the voltage at the distribution transformer point exceeds the upper limit across an area within the power supply range of the upstream substation and distribution line of the photovoltaic area.

[0009] In the preferred technical solution, if it is determined that the distribution transformer switching voltage exceeds the upper limit, after implementing time-sharing adjustment of the bus voltage, it is determined whether there is a partial distribution transformer switching voltage U. trans-i Low voltage problem, if U trans-j <U trans-down U trans-down If the voltage drop threshold at the distribution transformer is too large, the upper limit voltage drop of the busbar is reduced, and the transformer tap is adjusted. Then, it is further determined whether there is any user voltage U. user-i Low voltage problem iIndex for users; if U user-i <U user-down U user-down If the user voltage drop threshold is met, a low-voltage capacitor switching strategy is implemented, switching on capacitors during periods of low voltage to compensate for capacitive reactive power Q. C Reduce line voltage drop ΔU:

[0010] In the formula: P and Q are the active power and reactive power of the line load, respectively; R and X are the line resistance and reactance, respectively; and U is the real-time voltage at the distribution transformer junction.

[0011] In the preferred technical solution, the method for judging user voltage exceeding the limit scenario includes: If N sub <threshold or N line If the voltage exceeds the threshold, then count the number N of transformers with voltage exceeding the limit within the photovoltaic distribution area. trans ; If N trans If the voltage exceeds the threshold, it is determined that there is a scenario where users in the photovoltaic area are experiencing widespread voltage exceeding the limit.

[0012] In the preferred technical solution, if it is determined that the user voltage is exceeding the limit for a large area, after adjusting the transformer speed, it is determined whether there are any users with voltage U. user-i Low voltage problem; if U user-i <U user-down U user-down If a threshold for user voltage drop is set, it is determined that some users experience low voltage issues after the overall user voltage drop. During the period when low voltage occurs, capacitors are connected to compensate for capacitive reactive power Q. C Reduce line voltage drop ΔU:

[0013] In the formula: P and Q are the active power and reactive power of the line load, respectively; R and X are the line resistance and reactance, respectively; and U is the real-time voltage at the distribution transformer junction.

[0014] In the preferred technical solution, the methods for determining scenarios where photovoltaic user voltage severely exceeds the upper limit and scenarios where photovoltaic user voltage bidirectionally exceeds the upper limit include: If N trans If the threshold is less than 1, then calculate the photovoltaic user voltage U within the photovoltaic distribution area. PV-user-i ; If U PV-user-i >U ex-user-up U ex-user-up If the threshold for a severe voltage rise is set, then it is determined that the photovoltaic user has a scenario where the user voltage has severely exceeded the upper limit. If U PV-user-i ≤U ex-user-upThen determine the user voltage U in the photovoltaic area. user-i Is there a situation where the voltage exceeds both the upper and lower limits within a single day? If the user voltage U at time t1... user-i-t1 >U user-up And the user voltage U at time t2 user-i-t2 <U user-down Then, in the case of a photovoltaic user's voltage exceeding the limit in both directions, U user-up This is the threshold for the user's voltage rise.

[0015] In the preferred technical solution, if the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, after adjusting the photovoltaic inverter and time-sharing the low-voltage capacitors, it is determined whether some user voltage U still exists. user-i Out-of-limit problem; if U user-i <U user-down or U user-i >U user-up In this case, distributed SVG regulation, transformer area energy storage regulation, or low-voltage flexible DC interconnection can be adopted.

[0016] This invention also discloses a high-penetration photovoltaic (PV) distribution area voltage main-distribution coordinated hierarchical management system, used to implement the aforementioned high-penetration PV distribution area voltage main-distribution coordinated hierarchical management method, comprising: The module for classifying over-limit scenarios in high-penetration photovoltaic (PV) distribution areas categorizes over-limit scenarios into: distribution transformer gate voltage exceeding the upper limit for a large area, user voltage exceeding the upper limit for a large area, PV user voltage severely exceeding the upper limit for a large area, and PV user voltage exceeding the upper limit in both directions. The collaborative hierarchical governance module, if it is determined that the voltage at the distribution transformer gate exceeds the upper limit in a large area, will sequentially adopt a collaborative governance method of time-sharing adjustment of bus voltage, adjustment of distribution transformer tap, and time-sharing activation of low-voltage capacitors. If it is determined that the user voltage exceeds the limit in a large area, a coordinated management method of adjusting the distribution transformer level and time-sharing the low-voltage capacitors will be adopted in sequence. If it is determined that the voltage of the photovoltaic user is seriously exceeding the upper limit, the photovoltaic inverter adjustment method shall be adopted. If the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, a coordinated governance approach will be adopted in sequence, including photovoltaic inverter regulation, time-sharing connection of low-voltage capacitors, and distributed SVG regulation or distribution area energy storage or low-voltage flexible DC interconnection.

[0017] This invention also discloses a computer storage medium storing a computer program, wherein when the computer executes the computer program, it implements the high-penetration photovoltaic area voltage main and distribution coordinated hierarchical management method described in any of the above claims.

[0018] Compared with the prior art, the significant advantages of this invention are: Based on the quantity, type, and severity of voltage exceedances by distribution transformers and users, and following a step-by-step tracing approach from substations, feeders, distribution transformers, to users, a collaborative governance method for the main grid and distribution network is proposed. This method effectively addresses the issue of large voltage fluctuations in the distribution network, improves the photovoltaic carrying capacity and reactive power regulation capabilities of the distribution network, enhances the dynamic voltage regulation capability of photovoltaic distribution areas, improves the voltage quality for all users in photovoltaic distribution areas, increases the distribution network's capacity to absorb distributed photovoltaic power, and alleviates three-phase load imbalance within distribution areas. Some typical cases show that, after governance based on this method, the voltage qualification rate in the affected areas has increased to over 95%. Attached Figure Description

[0019] Figure 1 This is a flowchart of the voltage main and distribution coordinated hierarchical management method for high-penetration photovoltaic power distribution areas in this embodiment; Figure 2 This is a schematic diagram of the voltage main and distribution coordinated hierarchical management method for high-penetration photovoltaic power distribution areas in this embodiment; Figure 3 The busbar curves of the substation before and after treatment in this embodiment; Figure 4 This embodiment describes the voltage curves of typical users within the front-end and back-end areas for governance. Figure 5 The voltage curves of the front and back zones are used to address the issue in this embodiment. Detailed Implementation

[0020] The principle of this invention is: combining the number, type and degree of voltage exceedances by distribution transformers and users, and based on the step-by-step tracing approach of substations, feeders, distribution transformers and users, a method for coordinated management of the main grid and distribution network is proposed to effectively solve the problem of large voltage fluctuations in the distribution network.

[0021] Example: like Figure 1 As shown, a method for coordinated and hierarchical management of voltage in high-penetration photovoltaic power distribution areas includes the following steps: The scenarios of high-penetration photovoltaic (PV) distribution areas exceeding the limit are classified into: distribution transformer gate voltage exceeding the limit for a large area, user voltage exceeding the limit for a large area, PV user voltage severely exceeding the limit, and PV user voltage exceeding the limit in both directions. If it is determined that the voltage at the distribution transformer gate exceeds the upper limit in a large area, a coordinated management method of time-sharing adjustment of bus voltage, distribution transformer tap adjustment, and time-sharing connection of low-voltage capacitors shall be adopted in sequence. If it is determined that the user voltage exceeds the limit in a large area, a coordinated management method of adjusting the distribution transformer level and time-sharing the low-voltage capacitors will be adopted in sequence. If it is determined that the voltage of the photovoltaic user is seriously exceeding the upper limit, the photovoltaic inverter adjustment method shall be adopted. If the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, a coordinated governance approach will be adopted in sequence, including photovoltaic inverter regulation, time-sharing connection of low-voltage capacitors, and distributed SVG regulation or distribution area energy storage or low-voltage flexible DC interconnection.

[0022] Specifically, comprehensive voltage management strategies for different scenarios: (1) For distribution transformers with voltage exceeding the limit in a large area, the bus voltage time-sharing regulation measures should be taken first. If some distribution transformers still exceed the upper limit after the bus voltage time-sharing regulation measures are taken, the bus voltage time-sharing regulation and distribution transformer tap adjustment should be considered as a coordinated management method. If some users still exceed the lower limit after the bus voltage time-sharing regulation measures are taken, the bus voltage time-sharing regulation and low-voltage capacitor time-sharing activation should be considered as a coordinated management method.

[0023] (2) For users whose voltage exceeds the limit in a large area, the transformer tap adjustment measures should be taken first; if some users' voltage still exceeds the lower limit after the transformer tap adjustment, the transformer tap adjustment and low-voltage capacitors should be put into operation in a coordinated manner.

[0024] (3) For photovoltaic users whose voltage exceeds the limit, photovoltaic inverter regulation measures should be prioritized; if the photovoltaic inverter in the distribution area cannot adjust the reactive power operation mode, consider installing distributed SVG to regulate reactive power.

[0025] (4) In response to the large voltage fluctuations of photovoltaic users, priority should be given to the coordinated management of the main and distribution networks by multiple measures, including time-sharing regulation of bus voltage, time-sharing connection of low-voltage capacitors, and regulation of photovoltaic inverters. If the above methods are not effective, consider the adoption of the reactive power management method of adding distributed SVG.

[0026] In a preferred embodiment, the method further includes, before classifying high-penetration photovoltaic substations that exceed capacity limits: Photovoltaic penetration rate P:

[0027] Wherein: S PV S represents the total installed capacity of photovoltaic power in the distribution area. trans For distribution transformer capacity; If P > threshold, it indicates that the area is a high-penetration photovoltaic area.

[0028] In a preferred embodiment, the method for determining when the distribution transformer switching voltage exceeds the upper limit includes: Based on the connection relationship between the substation, distribution line, and distribution transformer, the distribution transformer cutoff voltage U within the power supply range of the substation and distribution line is obtained. trans-j , j For the coordinate variable index, if U trans-j >U trans-up This indicates that the transformer has a voltage exceeding the upper limit. trans-upThe threshold for voltage rise at the distribution transformer cut-off point; The number N of transformers with voltage exceeding the upper limit within the power supply range of this substation and distribution line was statistically determined. sub N line ; If N sub ≥threshold or N line If the voltage exceeds the threshold, it is determined that there is a scenario where the voltage at the distribution transformer point exceeds the upper limit across an area within the power supply range of the upstream substation and distribution line of the photovoltaic area.

[0029] In a preferred embodiment, if it is determined that the distribution transformer switching voltage exceeds the upper limit, after implementing time-sharing adjustment of the bus voltage, it is determined whether there is a partial distribution transformer switching voltage U. trans-i Low voltage problem, if U trans-j <U trans-down U trans-down If the voltage drop threshold at the distribution transformer is too large, the upper limit voltage drop of the busbar is reduced, and the transformer tap is adjusted. Then, it is further determined whether there is any user voltage U. user-i Low voltage problem i Index for users; if U user-i <U user-down U user-down If the user voltage drop threshold is met, a low-voltage capacitor switching strategy is implemented, switching on capacitors during periods of low voltage to compensate for capacitive reactive power Q. C Reduce line voltage drop ΔU:

[0030] In the formula: P and Q are the active power and reactive power of the line load, respectively; R and X are the line resistance and reactance, respectively; and U is the real-time voltage at the distribution transformer junction.

[0031] In a preferred embodiment, the method for determining user voltage exceeding limits includes: If N sub <threshold or N line If the voltage exceeds the threshold, then count the number N of transformers with voltage exceeding the limit within the photovoltaic distribution area. trans ; If N trans If the voltage exceeds the threshold, it is determined that there is a scenario where users in the photovoltaic area are experiencing widespread voltage exceeding the limit.

[0032] In a preferred embodiment, if it is determined that the user voltage is exceeding the limit across a large area, after adjusting the transformer speed, it is determined whether there are any users with voltage U. user-i Low voltage problem; if U user-i <U user-down U user-downIf a threshold for user voltage drop is set, it is determined that some users experience low voltage issues after the overall user voltage drop. During the period when low voltage occurs, capacitors are connected to compensate for capacitive reactive power Q. C Reduce line voltage drop ΔU:

[0033] In the formula: P and Q are the active power and reactive power of the line load, respectively; R and X are the line resistance and reactance, respectively; and U is the real-time voltage at the distribution transformer junction.

[0034] In a preferred embodiment, the method for determining scenarios of severe voltage overruns and bidirectional voltage overruns by photovoltaic users includes: If N trans If the threshold is less than 1, then calculate the photovoltaic user voltage U within the photovoltaic distribution area. PV-user-i ; If U PV-user-i >U ex-user-up U ex-user-up If the threshold for a severe voltage rise is set, then it is determined that the photovoltaic user has a scenario where the user voltage has severely exceeded the upper limit. If U PV-user-i ≤U ex-user-up Then determine the user voltage U in the photovoltaic area. user-i Is there a situation where the voltage exceeds both the upper and lower limits within a single day? If the user voltage U at time t1... user-i-t1 >U user-up And the user voltage U at time t2 user-i-t2 <U user-down Then, in the case of a photovoltaic user's voltage exceeding the limit in both directions, U user-up This is the threshold for the user's voltage rise.

[0035] In a preferred embodiment, if the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, after adjusting the photovoltaic inverter and time-sharing the low-voltage capacitors, it is determined whether some user voltage U still exists. user-i Out-of-limit problem; if U user-i <U user-down or U user-i >U user-up In this case, distributed SVG regulation, transformer area energy storage regulation, or low-voltage flexible DC interconnection can be adopted.

[0036] Another embodiment provides a high-penetration photovoltaic (PV) distribution area voltage main-distribution coordinated hierarchical management system for implementing the aforementioned high-penetration PV distribution area voltage main-distribution coordinated hierarchical management method, comprising: The module for classifying over-limit scenarios in high-penetration photovoltaic (PV) distribution areas categorizes over-limit scenarios into: distribution transformer gate voltage exceeding the upper limit for a large area, user voltage exceeding the upper limit for a large area, PV user voltage severely exceeding the upper limit for a large area, and PV user voltage exceeding the upper limit in both directions. The collaborative hierarchical governance module, if it is determined that the voltage at the distribution transformer gate exceeds the upper limit in a large area, adopts a collaborative governance method of time-sharing adjustment of bus voltage, distribution transformer tap adjustment, or time-sharing activation of low-voltage capacitors. If it is determined that the user voltage is exceeding the limit in a large area, a coordinated management method of adjusting the distribution transformer speed or putting low-voltage capacitors on in a time-sharing manner shall be adopted. If it is determined that the voltage of the photovoltaic user is seriously exceeding the upper limit, the photovoltaic inverter adjustment method shall be adopted. If the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, a collaborative governance approach should be adopted, which includes photovoltaic inverter regulation, time-sharing connection of low-voltage capacitors, or distributed SVG regulation / distribution area energy storage / low-voltage flexible DC interconnection.

[0037] The following example illustrates the workflow of a high-penetration photovoltaic (PV) distribution area voltage main and distribution coordinated hierarchical management system. Figure 2 As shown, it includes the following steps: Set the voltage rise threshold U at the distribution transformer. trans-up and voltage drop threshold U trans-down User voltage rise threshold U user-up and voltage drop threshold U user-down Typically, the default transformer shut-off point and the user voltage rise threshold U are... trans-up It is 107% of the rated voltage, i.e., 235.4V; the voltage drop threshold U at the distribution transformer cutoff point. trans-up It is 93% of the rated voltage, i.e., 213.4V; the user voltage drop threshold U trans-up It is 90% of the rated voltage, i.e., 198V; Step 1: Determine the photovoltaic (PV) penetration rate P in the PV distribution area. Based on the connection relationship between the substation, distribution line, and distribution transformer, trace the upstream substation and distribution line to which the PV distribution area belongs, and analyze the distribution transformer voltage U within the power supply range of the substation and distribution line. trans-j. The photovoltaic penetration rate P in a photovoltaic distribution area is calculated using the following formula:

[0038] In the formula: S PV For the photovoltaic installed capacity of the distribution area, S trans For distribution transformer capacity, j For the distribution variable index (j=1, 2, ... N) trans ), N trans This refers to the total number of transformers within the power supply range of the substation and distribution lines.

[0039] If P > 50%, it indicates that the area is a high-penetration photovoltaic area, and the method of this invention is applicable to the voltage problem management of the area. Otherwise, this method is not applicable.

[0040] If U trans-j >Utrans-up This indicates that the transformer has a voltage exceeding the upper limit.

[0041] Step 2: Count the number N transformers whose voltage exceeds the upper limit within the power supply range of this substation and distribution line. sub、 N line ; If N sub ≥100 or N line If ≥10, then S2=1, indicating that there is a problem of the voltage at the distribution transformer point exceeding the upper limit in the power supply range of the upstream substation and distribution line of the photovoltaic area. The third step is to implement the main grid voltage management strategy and carry out time-sharing adjustment of the substation bus voltage.

[0042] If N sub <100 or N line If the value is less than 10, then S2 = 0, indicating that there is no problem of the voltage at the distribution transformer point exceeding the upper limit within the power supply range of the photovoltaic area's upstream substation and distribution line. Then proceed to step five.

[0043] The specific implementation method of substation bus voltage time-sharing regulation is as follows: the bus voltage limit is set by the AVC system according to the time period. Generally, during the photovoltaic output period, the upper limit of the bus voltage is reduced from 10.6 / 10.65 kV to 10.35 kV, and during the non-output period, the upper limit of the bus voltage is increased to 10.6 / 10.65 kV, so as to realize the regulation of the distribution transformer voltage within the power supply range.

[0044] Step 3: Assess whether there is any voltage U at some distribution transformer outlets after implementing time-sharing regulation of the substation bus voltage. trans-i Low voltage problem; If U trans-j <U trans-down If S3=1, it means that the voltage drop of the upper limit of the bus voltage is too large. Consider reducing the voltage drop of the upper limit of the bus voltage and combine it with the measure of reducing the transformer tap to reduce the overall voltage drop of the transformer outlet. Continue to execute the fourth step.

[0045] If U trans-j ≥U trans-down If S3=0, it means the overall voltage problem has been solved, and the management strategy is output.

[0046] Step 4: Determine whether there are still users U after reducing the upper limit voltage drop of the bus voltage. user-i Low voltage problem i Retrieve for users (i=1, 2, ... N) user ), N user This represents the total number of users in the photovoltaic distribution area. If U user-i <U user-downThen S4=1, and the low-voltage capacitor switching strategy is implemented. Capacitors are switched on during periods of low voltage at the user location to compensate for capacitive reactive power Q. C Reduce line voltage drop △U ， Increase the voltage at the end user. Line voltage drop ΔU ， Calculate using the following formula:

[0047] In the formula: P and Q are the active power and reactive power of the line load, R and X are the line resistance and reactance, and U is the real-time voltage at the distribution transformer junction.

[0048] If U user-i ≥U user-down If S4=0, it means the overall voltage problem has been solved, and the management strategy is output.

[0049] Step 5: Count the number N of voltage-over-limit transformers for users within the photovoltaic distribution area. trans ; If N trans If the voltage is ≥40, then S5=1, indicating that there is a problem of users' voltage exceeding the limit in a large area of ​​the photovoltaic distribution area. Step 6 is to implement the distribution network voltage management strategy and carry out the adjustment of the distribution transformer tap.

[0050] If N trans If the value is less than 40, then S5 = 0, indicating that there is no problem with the voltage exceeding the limit for users in this photovoltaic area, and proceed to step seven.

[0051] The specific implementation method of distribution transformer tap adjustment is as follows: Generally, the distribution transformer tap is set to 10(10.5)±2×2.5% or 10(10.5)±5%, that is, three-stage distribution transformer and five-stage distribution transformer. By reducing the distribution transformer tap, the voltage at the cut-off point is reduced, thereby realizing voltage regulation for all users in the transformer area.

[0052] Step 6: Assess whether there are any issues with some users' U-turns after adjusting the distribution transformer tap position. user-i Low voltage problem; If U user-i <U user-down If S6=1, it indicates that some users experience low voltage after the overall voltage drop. Consider connecting capacitors during the periods of low voltage to compensate for capacitive reactive power Q. C Reduce line voltage drop △U ， The principle for increasing the voltage at the end user is the same as above.

[0053] If U user-i ≥U user-down If S6=0, it means the overall voltage problem has been solved, and the management strategy is output.

[0054] Step 7: Analyze the voltage U of photovoltaic users within the photovoltaic distribution area.PV-user-i , Set a threshold for severe voltage rise in users. ex-user-up Normally, the default threshold for a severe rise in user voltage is U. ex-user-up It is 115% of the rated voltage, i.e., 253V.

[0055] If U PV-user-i >U ex-user-up If S7=1, it means that the photovoltaic user has a serious problem of voltage exceeding the upper limit. The distribution network user-side voltage management strategy should be implemented, and reactive power regulation of the photovoltaic inverter should be carried out.

[0056] If U PV-user-i ≤U ex-user-up If S7=0, it means that the photovoltaic user does not have a serious problem of voltage exceeding the upper limit, and proceed to step eight.

[0057] The specific implementation method of reactive power regulation of photovoltaic inverter is as follows: the photovoltaic inverter is enabled in reactive voltage control mode. Under the condition that the active power output of photovoltaic remains unchanged, the reactive power output of the inverter is adjusted according to the change of grid connection point voltage to ensure that the grid connection point voltage operates within the specified voltage limit range.

[0058] Step 8: Analyze the user voltage U within the photovoltaic distribution area user-i Is there a situation where the voltage exceeds both the upper and lower limits within a single day? If the user voltage U at time t1 user-i-t1 >U user-up And the user voltage U at time t2 user-i-t2 <U user-down If S8=1, it indicates that the user has a bidirectional voltage over-limit problem. The distribution network user-side combined voltage management strategy should be implemented, and reactive power regulation of photovoltaic inverters and switching of low-voltage capacitors should be carried out.

[0059] If the user voltage U at time t1 user-i-t1 ≤U user-up Or the user voltage U at time t2 user-i-t2 ≥U user-down If S8=0, it means the overall voltage problem has been solved, and the management strategy is output.

[0060] The specific implementation method is as follows: when the photovoltaic inverter is activated in reactive power and voltage control mode, during the peak photovoltaic power generation period, the inverter outputs inductive reactive power to reduce the user voltage; during the evening peak electricity consumption period, the inverter outputs capacitive reactive power and low-voltage capacitors are connected to raise the user voltage.

[0061] Step 9: Determine whether some users still experience voltage U after implementing reactive power regulation of the photovoltaic inverter and switching of low-voltage capacitors. user-i Exceeding limits; If U user-i <Uuser-down or U user-i >U user-up If S9=1, it means that after implementing reactive power regulation of photovoltaic inverters and switching of low-voltage capacitors, there are still some users with voltage exceeding the limit. Consider adopting distributed SVG regulation or regional energy storage regulation or implementing low-voltage flexible DC interconnection.

[0062] If U user-down <U user-i <U user-up If S9=0, it means the overall voltage problem has been solved, and the management strategy is output.

[0063] The specific implementation method is as follows: 1) Distributed SVG regulation: It absorbs reactive power when photovoltaic power generation is high and generates reactive power when the load increases, thus completing bidirectional continuous voltage regulation.

[0064] 2) Distribution area energy storage regulation: By controlling the AC side current, the energy storage converter and the distribution network side are transmitted in both directions, and reactive power compensation on the distribution network side is achieved. By equipping lithium iron phosphate batteries as energy buffer components, active power fluctuations are smoothed according to the load change law of the distribution network, and active power adjustment in low-voltage distribution areas is achieved. Through reactive power compensation and active power adjustment, voltage over-limit management is achieved.

[0065] 3) Implement low-voltage flexible DC interconnection: Utilize two low-voltage flexible DC power exchanges (AC / DC) to interconnect on the DC bus side, forming a complete AC-DC-AC circuit (AC / DC-DC / AC). In low-voltage management of the distribution area, the rectifier cabinet is installed near the transformer voltage stabilization point, and the inverter cabinet is installed near the low-voltage user location. A DC bus is erected between the rectifier cabinet and the inverter cabinet, and the front-end energy is directly transmitted to the low-voltage user end through DC transmission, using a flexible DC solution to achieve voltage limit management.

[0066] In a preferred embodiment, for voltage issues in four scenarios, voltage management can also be achieved by adjusting the distributed grid connection method. Specifically, in areas where photovoltaic power cannot be fully absorbed, the grid connection method is adjusted to "low-voltage combiner, dedicated transformer boosting," utilizing dedicated low-voltage lines for photovoltaic combiners to achieve physical separation of low-voltage generation and supply, thus completely resolving the overvoltage problem caused by residential photovoltaic grid connection. The specific implementation plan is as follows: (1) New distribution transformer locations: Utilize the existing low-voltage network to build new distribution transformers, medium-voltage lines and a small number of low-voltage lines, and cut off some of the original low-voltage lines and corresponding users and new photovoltaics to the new distribution transformer locations, so as to better achieve local balance within the source-load distribution area. However, it is not convenient for centralized management of large-scale distributed photovoltaics. It is more suitable for photovoltaic access in areas with sporadic access or high electricity load.

[0067] (2) Centralized aggregation access: New photovoltaic power is aggregated through a three-phase AC line. This method is convenient for centralized management and control and has no voltage quality issues, but it has problems such as redundant construction of low-voltage networks and the inability to balance source and load locally at low voltage. It is more suitable for photovoltaic access in areas with large-scale village development and low electricity load.

[0068] (3) Low-voltage branch AC aggregation access: The newly added distributed photovoltaic low-voltage aggregation is connected to the same branch of the distribution transformer JP cabinet for grid connection, and the load is connected through other branches of the JP cabinet. This method can better achieve local balance within the source and load area, and facilitates centralized management and control of distributed photovoltaic, but requires the construction of new low-voltage aggregation lines. It is suitable for photovoltaic access in areas with large-scale village development and high electricity load.

[0069] The following is an example to illustrate this: Case 1: Voltage management achieved through time-sharing regulation of substation bus voltage. A certain substation has a photovoltaic distribution area accounting for 86% of its capacity. On sunny days, the maximum voltage of the 10kV II section bus of this substation is significantly higher by 0.14kV compared to cloudy days, and the voltage at the 110 distribution transformer substation exceeds the limit. Based on load, photovoltaic output, and voltage change trends, the bus voltage operating range is subdivided into 8 time periods for differentiated control, such as... Figure 3 As shown in the figure. After the treatment was implemented, there were no voltage over-limit issues at the distribution transformer outlets under the substation, demonstrating significant treatment effectiveness.

[0070] Case 2: Voltage management achieved through transformer speed adjustment and low-voltage capacitor switching. In a certain distribution area with a photovoltaic penetration rate of 127%, user voltage consistently exceeded the upper limit, with the highest voltage at the transformer switch reaching 247.2V and the lowest 236.2V, resulting in a coexistence of high and low voltage for users throughout the area. By adjusting the transformer speed control valve from level 4 to level 2 and installing two distributed capacitors (total capacity 120kVar) on the low-voltage branch line, the voltage for users in the area stabilized between 210-230V, and all user voltages operated within the acceptable range.

[0071] Case 3: Voltage Management Through Reactive Power Regulation of Photovoltaic Inverters. A certain distribution area has 8 distributed photovoltaic (PV) users, with a PV penetration rate of 87.5%. The maximum voltage at the control point is 240.5V, and the minimum is 225V. The maximum voltage at each user is 245.5V, and the minimum is 222.6V. The voltage compliance rate for the area is 75.3%. After implementing reactive power regulation on the inverters in the area, the voltage compliance rate increased to 95.7%. Figure 4 As shown.

[0072] Case 4: Voltage Management via Distributed SVG. A certain distribution area has an 80% photovoltaic penetration rate. On a typical sunny day, the maximum voltage drop at the distribution transformer is 241.8V, and the minimum is 232.6V. All users within the area experience voltage exceedances, with a maximum voltage of 262V and a voltage fluctuation of 40.5V. After implementing a 75 kvar distributed SVG at the end of the distribution area, the voltage drop at the transformer outlet is reduced to 15V, and there are no voltage exceedances throughout the day. Figure 5 As shown.

[0073] In summary, this invention develops a high-penetration photovoltaic (PV) distribution area voltage management method that coordinates main and distribution systems to improve the dynamic regulation capability of PV distribution area voltage. This method addresses issues such as voltage exceeding limits at PV distribution area users and distribution transformer points, alleviates significant voltage fluctuations at users, improves the reactive power regulation capability of the distribution network, and enhances the PV carrying capacity of the distribution network. Some typical cases show that the voltage qualification rate in the affected areas has increased to over 95% after the implementation of this method.

[0074] In another embodiment, a computer storage medium stores a computer program thereon, wherein when the computer executes the computer program, it implements the high-penetration photovoltaic distribution area voltage main and distribution coordinated hierarchical management method described in any of the above embodiments.

[0075] The specific implementation method is the one described above, and will not be repeated here.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas, characterized in that, Includes the following steps: The scenarios of high-penetration photovoltaic (PV) distribution areas exceeding the limit are classified into: distribution transformer gate voltage exceeding the limit for a large area, user voltage exceeding the limit for a large area, PV user voltage severely exceeding the limit, and PV user voltage exceeding the limit in both directions. If it is determined that the voltage at the distribution transformer gate exceeds the upper limit in a large area, a coordinated management method of time-sharing adjustment of bus voltage, distribution transformer tap adjustment, and time-sharing connection of low-voltage capacitors shall be adopted in sequence. If it is determined that the user voltage exceeds the limit in a large area, a coordinated management method of adjusting the distribution transformer level and time-sharing the low-voltage capacitors will be adopted in sequence. If it is determined that the voltage of the photovoltaic user is seriously exceeding the upper limit, the photovoltaic inverter adjustment method shall be adopted. If the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, a coordinated governance approach will be adopted in sequence, including photovoltaic inverter regulation, time-sharing connection of low-voltage capacitors, and distributed SVG regulation or distribution area energy storage or low-voltage flexible DC interconnection.

2. The method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas according to claim 1, characterized in that, Before classifying the scenarios of high-penetration photovoltaic power stations exceeding limits, the following also applies: Photovoltaic penetration rate P: Wherein: S PV S represents the total installed capacity of photovoltaic power in the distribution area. trans For distribution transformer capacity; If P > threshold, it indicates that the area is a high-penetration photovoltaic area.

3. The method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas according to claim 1, characterized in that, Methods for determining when the voltage at the distribution transformer junction exceeds the upper limit include: Based on the connection relationship between the substation, distribution line, and distribution transformer, the distribution transformer cutoff voltage U within the power supply range of the substation and distribution line is obtained. trans-j , j For the coordinate variable index, if U trans-j >U trans-up This indicates that the transformer has a voltage exceeding the upper limit. trans-up The threshold for voltage rise at the distribution transformer cut-off point; The number N of transformers with voltage exceeding the upper limit within the power supply range of this substation and distribution line was statistically determined. sub N line ; If N sub ≥threshold or N line If the voltage exceeds the threshold, it is determined that there is a scenario where the voltage at the distribution transformer point exceeds the upper limit across an area within the power supply range of the upstream substation and distribution line of the photovoltaic area.

4. The method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas according to claim 1, characterized in that, If the scenario is determined to be a case where the distribution transformer switching voltage exceeds the upper limit, after implementing time-sharing adjustment of the bus voltage, it is determined whether there is a partial distribution transformer switching voltage U. trans-i Low voltage problem, if U trans-j <U trans-down U trans-down If the voltage drop threshold at the distribution transformer is too high, the upper limit voltage drop of the bus voltage should be reduced, and the transformer tap position adjusted. Further investigation is needed to determine if there is any user voltage U. user-i Low voltage problem i Index for users; if U user-i <U user-down U user-down If the user voltage drop threshold is met, a low-voltage capacitor switching strategy is implemented, switching on capacitors during periods of low voltage to compensate for capacitive reactive power Q. C Reduce line voltage drop ΔU: In the formula: P and Q are the active power and reactive power of the line load, respectively; R and X are the line resistance and reactance, respectively; and U is the real-time voltage at the distribution transformer junction.

5. The method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas according to claim 3, characterized in that, Methods for determining user voltage exceeding limits include: If N sub <threshold or N line If the voltage exceeds the threshold, then count the number N of transformers with voltage exceeding the limit within the photovoltaic distribution area. trans ; If N trans If the voltage exceeds the threshold, it is determined that there is a scenario where users in the photovoltaic area are experiencing widespread voltage exceeding the limit.

6. The method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas according to claim 1, characterized in that, If the scenario is determined to be a case of widespread voltage exceeding limits for a user area, after adjusting the transformer speed, it is determined whether there are any instances of partial user voltage U. user-i Low voltage problem; if U user-i <U user-down U user-down If a threshold for user voltage drop is set, it is determined that some users experience low voltage issues after the overall user voltage drop. During the period when low voltage occurs, capacitors are connected to compensate for capacitive reactive power Q. C Reduce line voltage drop ΔU: In the formula: P and Q are the active power and reactive power of the line load, respectively; R and X are the line resistance and reactance, respectively; and U is the real-time voltage at the distribution transformer junction.

7. The method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas according to claim 5, characterized in that, The methods for determining scenarios where photovoltaic (PV) user voltage severely exceeds the upper limit and scenarios where PV user voltage exceeds the upper limit in both directions include: If N trans If the threshold is less than 1, then calculate the photovoltaic user voltage U within the photovoltaic distribution area. PV-user-i ; If U PV-user-i >U ex-user-up U ex-user-up If the threshold for a severe voltage rise is set, then it is determined that the photovoltaic user has a scenario where the user voltage has severely exceeded the upper limit. If U PV-user-i ≤U ex-user-up Then determine the user voltage U in the photovoltaic area. user-i Is there a situation where the voltage exceeds both the upper and lower limits within a single day? If the user voltage U at time t1... user-i-t1 >U user-up And the user voltage U at time t2 user-i-t2 <U user-down Then, in the case of a photovoltaic user's voltage exceeding the limit in both directions, U user-up This is the threshold for the user's voltage rise.

8. The method for coordinated and hierarchical management of voltage in high-penetration photovoltaic distribution areas according to claim 7, characterized in that, If the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, after implementing photovoltaic inverter regulation and time-sharing connection of low-voltage capacitors, it is determined whether some users still experience voltage U. user-i Out-of-limit problem; if U user-i <U user-down or U user-i >U user-up In this case, distributed SVG regulation, transformer area energy storage regulation, or low-voltage flexible DC interconnection can be adopted.

9. A high-penetration photovoltaic distribution area voltage main and distribution coordinated hierarchical management system, characterized in that, The method for implementing the high-penetration photovoltaic power distribution area voltage main and distribution coordinated hierarchical management method as described in any one of claims 1-8 includes: The module for classifying over-limit scenarios in high-penetration photovoltaic (PV) distribution areas categorizes over-limit scenarios into: distribution transformer gate voltage exceeding the upper limit for a large area, user voltage exceeding the upper limit for a large area, PV user voltage severely exceeding the upper limit for a large area, and PV user voltage exceeding the upper limit in both directions. The collaborative hierarchical governance module, if it is determined that the voltage at the distribution transformer gate exceeds the upper limit in a large area, will sequentially adopt a collaborative governance method of time-sharing adjustment of bus voltage, adjustment of distribution transformer tap, and time-sharing activation of low-voltage capacitors. If it is determined that the user voltage exceeds the limit in a large area, a coordinated management method of adjusting the distribution transformer level and time-sharing the low-voltage capacitors will be adopted in sequence. If it is determined that the voltage of the photovoltaic user is seriously exceeding the upper limit, the photovoltaic inverter adjustment method shall be adopted. If the scenario is determined to be a bidirectional voltage over-limit scenario for photovoltaic users, a coordinated governance approach will be adopted in sequence, including photovoltaic inverter regulation, time-sharing connection of low-voltage capacitors, and distributed SVG regulation or distribution area energy storage or low-voltage flexible DC interconnection.

10. A computer storage medium having a computer program stored thereon, characterized in that, When the computer executes the computer program, it implements the high-penetration photovoltaic power distribution area voltage main and distribution coordinated hierarchical management method as described in any one of claims 1-8.

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