A power distribution network overvoltage regulation method and system

Abstract

This application discloses an overvoltage regulation method and system for a distribution network, belonging to the field of distribution network technology. The method includes: determining the current voltage regulation condition; determining a dynamic droop coefficient reference value when the current voltage regulation condition is an emergency voltage regulation condition or a transition from an emergency voltage regulation condition to an iterative supplementary regulation condition; determining a target reactive power adjustment amount for the photovoltaic inverter based on the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous voltage regulation, a preset voltage reference value, a preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the reactive power distribution coefficient of the photovoltaic inverter, and preset safety constraint verification rules; updating the current reactive power output value based on the target reactive power adjustment amount, and repeating the step of determining the dynamic droop coefficient reference value when the current voltage is greater than a preset voltage difference, until the iteration stops when the current voltage is less than or equal to the preset voltage difference. This application can achieve overvoltage regulation.

Description

Technical Field

[0001] This application relates to the field of power distribution network technology, and in particular to an overvoltage control method and system for power distribution networks. Background Technology

[0002] The power distribution network is a crucial link in the power system that directly faces end users. Like the "capillaries" of the power system, it plays an irreplaceable role in ensuring power supply, supporting economic and social development, and improving people's livelihoods.

[0003] However, the randomness and volatility of distributed photovoltaic (PV) output after a high proportion of it is connected to the distribution network pose a serious challenge to the stable operation of the network. Especially under conditions of ample sunlight and light local load, the excessive injection of active power from PV generation can easily lead to a significant increase in the Point of Common Coupling (PCC) voltage, causing serious overvoltage problems. Such overvoltage phenomena not only degrade power quality but also directly threaten the safe operation of distribution lines, transformers, and user-side household appliances, causing anything from equipment burnout to insulation breakdown and fires. If this problem is not effectively addressed, it will severely restrict the healthy development and large-scale application of distributed PV.

[0004] Therefore, researching effective overvoltage control methods for photovoltaic grid integration has become an urgent need to ensure the safe and stable operation of the grid and promote the sustainable development of the new energy industry. Summary of the Invention

[0005] A method and system for overvoltage regulation in a power distribution network are provided to achieve overvoltage regulation of photovoltaic power generation connected to the power distribution network.

[0006] Firstly, an overvoltage regulation method for a power distribution network is provided, wherein multiple photovoltaic inverters are connected to the power distribution network; the method includes: The current voltage regulation condition is determined based on the current voltage at the common grid connection point of multiple photovoltaic inverters, the preset voltage reference value, and the preset voltage hysteresis threshold. When the current voltage regulation condition is an emergency voltage regulation condition or when transitioning from an emergency voltage regulation condition to an iterative compensation condition, determine the benchmark value of the dynamic droop coefficient. The target reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient benchmark value, the voltage feedback value of the common grid connection point after the previous voltage regulation, the preset voltage benchmark value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the photovoltaic inverter, and the preset safety constraint verification rules; wherein, the voltage deviation of the common grid connection point is the difference between the preset voltage benchmark value and the current voltage of the common grid connection point. Update the current reactive power output value according to the target reactive power adjustment amount, and if the current voltage is greater than the preset voltage difference, return to repeat the step of determining the dynamic droop coefficient reference value until the current voltage is less than or equal to the preset voltage difference, at which point the iteration stops; the preset voltage difference is the difference between the preset voltage reference value and the preset voltage hysteresis threshold.

[0007] In some embodiments, the current voltage regulation condition is determined based on the current voltage of the common grid connection point of multiple photovoltaic inverters, a preset voltage reference value, and a preset voltage hysteresis threshold, including: If the current voltage is less than or equal to the difference between the preset voltage reference value and the preset voltage hysteresis threshold, the current voltage regulation condition is determined to be a steady-state non-voltage regulation condition. If the current voltage is greater than the preset voltage reference value, the current voltage regulation condition is determined to be an emergency no-voltage regulation condition. If the current voltage is greater than the difference between the preset voltage reference value and the preset voltage hysteresis threshold, but less than the preset voltage reference value, the current voltage regulation condition is determined to be an iterative adjustment condition.

[0008] In some embodiments, the formula for calculating the dynamic droop coefficient reference value is as follows: k_V_base(t) = k_V0 × k1 × k2; Where k_V_base(t) represents the dynamic droop coefficient base value; k_V0 represents the base droop coefficient; k1 represents the voltage deviation correction factor; and k2 represents the total active power output correction factor.

[0009] In some embodiments, the formula for calculating the voltage deviation correction factor is: k1=1+min(0.8×(U(t)-U_ref) / (0.03×U_N), 0.8); The formula for calculating the total active power output correction factor is: k2=1-min(0.5×(ΣP_i(t) / ΣP_rated_i), 0.5); Where U(t) represents the current voltage; U_ref represents the preset voltage reference value; U_N represents the rated voltage of the distribution network; P_i(t) represents the active power output value; and P_rated_i represents the rated active capacity.

[0010] In some embodiments, the target reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous voltage adjustment, the preset voltage reference value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the reactive power distribution coefficient of the photovoltaic inverter, and the preset safety constraint verification rules, including: The dynamic droop coefficient adjustment value is determined based on the preset voltage reference value, the preset voltage hysteresis threshold, and the voltage feedback value of the common grid connection point after the previous voltage regulation. The initial reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient benchmark value, the voltage deviation at the common grid connection point, and the reactive power distribution coefficient of the photovoltaic inverter. The target reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment amount, and the preset safety constraint verification rules.

[0011] In some embodiments, the initial reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient reference value, the voltage deviation at the common grid connection point, and the reactive power distribution coefficient of the photovoltaic inverter, including: The total global reactive power adjustment is determined based on the dynamic droop coefficient benchmark value and the voltage deviation at the common grid connection point. The initial reactive power adjustment of the photovoltaic inverter is determined based on the total global reactive power adjustment and the reactive power distribution coefficient of the photovoltaic inverter.

[0012] In some embodiments, the formula for calculating the total global reactive power adjustment is: ΔQ_total(t)=k_V_base(t)×(U_ref-U(t)); The formula for calculating the initial reactive power adjustment of a photovoltaic inverter is: ΔQ_i_alloc(t)=α_i×ΔQ_total(t); Wherein, ΔQ_total(t) represents the total global reactive power adjustment; k_V_base(t) represents the dynamic droop coefficient reference value; ΔQ_i_alloc(t) represents the initial reactive power adjustment; α_i represents the reactive power allocation coefficient; U(t) represents the current voltage; and U_ref represents the preset voltage reference value.

[0013] In some embodiments, the target reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment amount, and the preset safety constraint verification rules, including: The intermediate reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient adjustment value and the initial reactive power adjustment amount. Using preset safety constraint verification rules, the intermediate reactive power adjustment is verified to determine the target reactive power adjustment of the photovoltaic inverter.

[0014] In some embodiments, the formula for calculating the intermediate reactive power adjustment of a photovoltaic inverter is: ΔQ_i_corr(t)=ΔQ_i_alloc(t)×(1+(U'(t)-(U_ref-ΔU)) / U_ref); Where ΔQ_i_corr(t) represents the intermediate reactive power adjustment; ΔQ_i_alloc(t) represents the initial reactive power adjustment; U'(t) represents the voltage feedback value of the common grid connection point after the previous voltage regulation; U_ref represents the preset voltage reference value; and ΔU represents the preset voltage hysteresis threshold.

[0015] In some embodiments, a preset safety constraint verification rule is used to perform a safety constraint verification on the intermediate reactive power adjustment to determine the target reactive power adjustment of the photovoltaic inverter, including: The step size limit adjustment amount is determined based on the intermediate reactive power adjustment amount and the maximum reactive power adjustment step size of the photovoltaic inverter; The predicted reactive power output value is determined based on the current reactive power output value and the step size limit adjustment. If the predicted reactive power output value is less than the current allowable reactive power limit or the rated reactive power limit, the target reactive power adjustment amount is determined based on the current allowable reactive power limit and the current reactive power output value. If the predicted reactive power output value is greater than or equal to the current allowable reactive power limit or the rated reactive power limit, the target reactive power adjustment amount is determined based on the step size limit adjustment amount.

[0016] In some embodiments, the formula for calculating the step size limit adjustment is: ΔQ_i_lim(t)=max(-ΔQ_max, min(ΔQ_i_corr(t), ΔQ_max)); The formula for calculating the predicted reactive power output is: Q_i_pred(t)=Q_i_curr(t)+ΔQ_i_lim(t); The formula for calculating the target reactive power adjustment is: If the predicted reactive power output value is less than the current allowable reactive power limit or the rated reactive power limit of the photovoltaic inverter, then the formula for calculating the target reactive power adjustment is as follows: ΔQ_i_safe(t)=Q_allow_i(t)-Q_i_curr(t); Otherwise, the formula for calculating the target reactive power adjustment is: ΔQ_i_safe(t) = ΔQ_i_lim(t); Where Q_allow_i(t) represents the current allowed reactive power limit; The current formula for calculating the maximum allowable reactive power is: ; Wherein, ΔQ_max represents the maximum allowable reactive power adjustment step size for a single photovoltaic inverter; Q_i_curr(t) represents the reactive power output value; ΔQ_i_lim(t) represents the step size limit adjustment amount; ΔQ_i_safe(t) represents the target reactive power adjustment amount; Q_allow_i(t) represents the current allowable reactive power upper limit; ΔQ_i_corr(t) represents the intermediate reactive power adjustment amount; Q_i_pred(t) represents the predicted reactive power output value; and Q_rated_i represents the rated reactive power upper limit.

[0017] In some embodiments, the method further includes: verifying that the total apparent power of all photovoltaic inverters after adjustment does not exceed the sum of the rated apparent power of each photovoltaic inverter.

[0018] In some embodiments, the formula for calculating the dynamic droop coefficient adjustment value is as follows: k_V_i_adj(t)=(1+(U'(t)-(U_ref-ΔU)) / U_ref); Where k_V_i_adj(t) represents the dynamic droop coefficient adjustment value; U'(t) represents the voltage feedback value of the common grid connection point after the previous voltage regulation; U_ref represents the preset voltage reference value; and ΔU represents the preset voltage hysteresis threshold.

[0019] In some embodiments, the method further includes: not performing voltage regulation when the current voltage regulation condition is a steady-state non-voltage regulation condition, or when transitioning from a steady-state non-voltage regulation condition to an iterative supplementary regulation condition.

[0020] Secondly, this application also provides an overvoltage control system for a power distribution network, wherein multiple photovoltaic inverters are connected to the power distribution network; the system includes: The first determining module is used to determine the current voltage regulation condition based on the current voltage of the common grid connection point of multiple photovoltaic inverters, the preset voltage reference value, and the preset voltage hysteresis threshold. The second determining module is used to determine the reference value of the dynamic droop coefficient when the current voltage regulation condition is an emergency voltage regulation condition or when transitioning from an emergency voltage regulation condition to an iterative adjustment condition. The third determining module is used to determine the target reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient benchmark value, the voltage feedback value of the common grid connection point after the previous voltage adjustment, the preset voltage benchmark value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the reactive power distribution coefficient of the photovoltaic inverter, and the preset safety constraint verification rules; wherein, the voltage deviation of the common grid connection point is the difference between the preset voltage benchmark value and the current voltage of the common grid connection point; The update module is used to update the current reactive power output value according to the target reactive power adjustment. The iteration module is used to repeatedly execute the step of determining the dynamic droop coefficient reference value when the current voltage is greater than the preset voltage difference, until the current voltage is less than or equal to the preset voltage difference, at which point the iteration stops; the preset voltage difference is the difference between the preset voltage reference value and the preset voltage hysteresis threshold.

[0021] Beneficial Effects: This application provides an overvoltage regulation method and system for a distribution network. The overvoltage regulation method includes: determining the current voltage regulation condition based on the current voltage of the common grid connection point of multiple photovoltaic inverters, a preset voltage reference value, and a preset voltage hysteresis threshold; determining a dynamic droop coefficient reference value when the current voltage regulation condition is an emergency voltage regulation condition or a transition from an emergency voltage regulation condition to an iterative supplementary regulation condition; and determining the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous voltage regulation, the preset voltage reference value, the preset voltage hysteresis threshold, and the common grid connection point... The method determines the target reactive power adjustment of the photovoltaic inverter based on the voltage deviation, the reactive power distribution coefficient of the photovoltaic inverter, and preset safety constraint verification rules. The voltage deviation at the common grid connection point is the difference between a preset voltage reference value and the current voltage at the common grid connection point. The current reactive power output value is updated according to the target reactive power adjustment. If the current voltage is greater than the preset voltage difference, the method returns to repeatedly execute the step of determining the dynamic droop coefficient reference value until the current voltage is less than or equal to the preset voltage difference, at which point the iteration stops. The preset voltage difference is the difference between the preset voltage reference value and the preset voltage hysteresis threshold. The overvoltage control method for the distribution network provided in this application dynamically determines the dynamic droop coefficient reference value and the target reactive power adjustment of the photovoltaic inverter based on real-time voltage and inverter operating data. This dynamically updates the current reactive power output value of the photovoltaic inverter, thereby dynamically adjusting the voltage at the common grid connection point according to the updated current reactive power output value, stabilizing the voltage at the common grid connection point, and achieving closed-loop control of overvoltage in photovoltaic grid connection. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0024] Figure 1 This is a flowchart of an overvoltage control method for a power distribution network provided in the embodiments of this application; Figure 2 This is a schematic diagram of the overall process of an overvoltage control method for a power distribution network provided in the embodiments of this application; Figure 3 This is a schematic diagram of the total photovoltaic output variation curve provided in the embodiments of this application; Figure 4 This is a schematic diagram of the voltage variation curve at the common grid connection point provided in the embodiments of this application; Figure 5 This is a schematic diagram of the reactive power output curve of a typical inverter provided in the embodiments of this application; Figure 6 This is a schematic diagram of the overvoltage control system for a power distribution network provided in the embodiments of this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0026] In the embodiments of this application, "at least one" refers to one or more; "multiple" refers to two or more. In the description of this application, the terms "first," "second," "third," etc., are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance, nor should they be construed as indicating or implying order.

[0027] References such as “one embodiment” or “some embodiments” as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the terms “comprising,” “including,” “having,” and variations thereof, as used in this specification, mean “including, but not limited to,” unless otherwise specifically emphasized.

[0028] It should be noted that in the embodiments of this application, "and / or" describes the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after it are in an "or" relationship.

[0029] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0030] The applicant's research found that the power distribution network is a key link in the power system that directly faces end users. It is like the "capillaries" of the power system, playing an irreplaceable role in ensuring power supply, supporting economic and social development, and serving to improve people's livelihoods.

[0031] However, the randomness and volatility of distributed photovoltaic (PV) output after a high proportion of PV power is integrated into the distribution network pose a severe challenge to the stable operation of the network. Especially under conditions of ample sunlight and light local load, the excessive injection of active power from PV generation can easily lead to a significant increase in the Point of Common Coupling (PCC) voltage, causing serious overvoltage problems. Such overvoltage phenomena not only degrade power quality but also directly threaten the safe operation of distribution lines, transformers, and user-side electrical appliances, causing anything from equipment burnout to insulation breakdown and fires. If this problem is not effectively addressed, it will severely restrict the healthy development and large-scale application of distributed PV. Therefore, researching effective overvoltage control methods for PV integration into the distribution network has become an urgent need to ensure the safe and stable operation of the distribution network and promote the sustainable development of the new energy industry.

[0032] Controlling the reactive power output of inverters helps mitigate overvoltage problems in distribution networks caused by distributed photovoltaic (PV) grid integration. Related technologies employ voltage-reactive power droop control methods based on distributed PV, a common approach in voltage control. However, existing overvoltage mitigation control methods for PV-integrated distribution networks suffer from the following problems: Firstly, relying on local inverter information for independent decision-making, lacking system-level coordination, can easily lead to reactive power imbalance among multiple devices, causing voltage overshoot or regulation lag.

[0033] Secondly, using a fixed droop coefficient for control cannot adapt to the dynamic changes in photovoltaic output and grid conditions, the voltage regulation sensitivity does not match the actual needs, and the voltage stabilization effect is limited.

[0034] Third, the control process generally lacks a complete safety constraint mechanism, making it difficult to prevent sudden changes in reactive power commands and the risk of equipment overload, and failing to balance governance effectiveness and operational safety.

[0035] Therefore, there is an urgent need to design a photovoltaic grid-connected overvoltage control method that is highly collaborative, adaptable, and safe, in order to solve the above-mentioned technical bottlenecks.

[0036] In view of this, embodiments of this application provide an overvoltage control method and system for a distribution network. The overvoltage control method for a distribution network provided in this application, based on real-time voltage and inverter operating data, dynamically determines the dynamic droop coefficient benchmark value and the target reactive power adjustment amount of the photovoltaic inverter under emergency voltage regulation conditions or transitioning from emergency voltage regulation conditions to iterative adjustment conditions. This dynamically updates the current reactive power output value of the photovoltaic inverter, thereby dynamically adjusting the voltage at the common grid connection point according to the updated current reactive power output value, stabilizing the voltage at the common grid connection point, and realizing closed-loop control of overvoltage of photovoltaic grid connection.

[0037] Figure 1 This is a flowchart illustrating an overvoltage control method for a distribution network provided in this application embodiment. This application embodiment provides an overvoltage control method for a distribution network, applicable to a distribution network voltage control system, for controlling overvoltage in a distribution network connected to photovoltaic inverters. This method can be executed by an overvoltage control system for the distribution network, which can be implemented in software and / or hardware. This system can be configured in the processor or controller of the distribution network voltage control system (e.g., a centralized controller deployed at a common grid connection point for multiple photovoltaic inverters). Please refer to... Figure 1 The method includes the following steps: Step 110: Determine the current voltage regulation condition based on the current voltage of the common grid connection point of multiple photovoltaic inverters, the preset voltage reference value, and the preset voltage hysteresis threshold.

[0038] A centralized controller is deployed at the common grid connection point of multiple photovoltaic (PV) inverters. The centralized controller collects the current voltage U(t) of the common grid connection point in real time and obtains the active power output value P_i(t), the current reactive power output value Q_i_curr(t), the apparent power output value S_i(t), and the rated parameters of each PV inverter from its local controller via communication. Here, i represents the PV inverter number, and its value range is consistent with the total number of PV inverters in the system.

[0039] The rated parameters of the photovoltaic inverter include the rated active capacity P_rated_i, the rated apparent power S_rated_i, and the rated reactive power limit Q_rated_i for each photovoltaic inverter.

[0040] The formula for calculating the rated apparent power S_rated_i is as follows: S_rated_i = P_rated_i / 0.9; The formula for calculating the rated reactive power upper limit Q_rated_i is as follows: ; Among them, the calculation formula for the preset voltage reference value U_ref is: U_ref = 1.07×U_N; Among them, U_N represents the rated voltage of the distribution network.

[0041] Among them, the value range of the preset voltage hysteresis threshold is: 0.5%U_N to 1%U_N.

[0042] In some embodiments, according to the current voltage, preset voltage reference value, and preset voltage hysteresis threshold of the common connection point of multiple photovoltaic inverters, determine the current voltage regulation condition, including: when the current voltage is less than or equal to the difference between the preset voltage reference value and the preset voltage hysteresis threshold, determine that the current voltage regulation condition is a steady-state non-voltage regulation condition; when the current voltage is greater than the preset voltage reference value, determine that the current voltage regulation condition is an emergency voltage regulation condition; when the current voltage is greater than the difference between the preset voltage reference value and the preset voltage hysteresis threshold and less than the preset voltage reference value, determine that the current voltage regulation condition is an iterative compensation regulation condition.

[0043] Specifically, based on the collected current voltage U(t) of the common connection point, combined with the preset voltage reference value U_ref and the preset voltage hysteresis threshold ΔU, determine the current voltage regulation condition. Among them, the current voltage regulation conditions include: When U(t) ≤ U_ref - ΔU, determine that the current voltage regulation condition is a steady-state non-voltage regulation condition.

[0044] When U(t) > U_ref, determine that the current voltage regulation condition is an emergency voltage regulation condition.

[0045] When U_ref - ΔU < U(t) ≤ U_ref, determine that the current voltage regulation condition is an iterative compensation regulation condition.

[0046] In some embodiments, the method further includes: when the current voltage regulation condition is a steady-state non-voltage regulation condition, or when transitioning from a steady-state non-voltage regulation condition to an iterative compensation regulation condition, do not perform voltage regulation.

[0047] Specifically, when voltage regulation is not started at the beginning, voltage regulation only starts when an emergency voltage regulation condition appears. When transitioning from a steady-state non-voltage regulation condition to an iterative compensation regulation condition, there is no voltage regulation. When transitioning from an emergency voltage regulation condition to an iterative non-regulation condition, voltage regulation still needs to continue until it is adjusted to a steady-state non-voltage regulation condition to end voltage regulation.

[0048] Step 120, when the current voltage regulation condition is an emergency voltage regulation condition or when transitioning from an emergency voltage regulation condition to an iterative compensation regulation condition, determine the dynamic droop coefficient reference value.

[0049] Specifically, no voltage regulation is required when the current voltage regulation condition is determined to be a steady-state condition without voltage regulation. When the current voltage regulation condition is an emergency voltage regulation condition or when transitioning from an emergency voltage regulation condition to an iterative supplementary regulation condition, the centralized controller calculates a unified dynamic droop coefficient base value k_V_base(t) for the entire system, so as to dynamically determine the target reactive power adjustment amount in the future, realize dynamic voltage regulation, and achieve overvoltage control when photovoltaic inverters are connected to the distribution network.

[0050] In some embodiments, the method for determining the reference value of the dynamic droop coefficient includes: determining a voltage deviation correction factor and a total active power output correction factor; and determining the reference value of the dynamic droop coefficient based on the voltage deviation correction factor, the total active power output correction factor, and a preset reference droop coefficient.

[0051] Specifically, the formula for calculating the dynamic droop coefficient base value k_V_base(t) is as follows: k_V_base(t) = k_V0 × k1 × k2; Where k_V0 represents the reference droop coefficient, which can be 1.2 kvar / V for example. k1 represents the voltage deviation correction factor; k2 represents the total active power output correction factor.

[0052] In some embodiments, the method for determining the voltage deviation correction factor and the total active power output correction factor includes: determining the voltage deviation correction factor based on the current voltage, a preset voltage reference value, and the rated voltage of the distribution network; and determining the total active power output correction factor based on the active power output value and rated active power capacity of the photovoltaic inverter.

[0053] Specifically, the formula for calculating the voltage deviation correction factor k1 is as follows: k1=1+min(0.8×(U(t)-U_ref) / (0.03×U_N), 0.8); The formula for calculating the total active power output correction factor is: k2=1-min(0.5×(ΣP_i(t) / ΣP_rated_i), 0.5); Therefore, it can be seen that the embodiments of this application construct a dynamic droop coefficient model with two factors (i.e., voltage deviation correction factor and total active power output correction factor), and adaptively adjust the parameters according to the changes in voltage deviation and photovoltaic output, which can solve the problem of poor adaptability of fixed coefficients and improve the voltage stabilization effect under complex working conditions.

[0054] Step 130: Determine the target reactive power adjustment amount of the photovoltaic inverter based on the dynamic droop coefficient benchmark value, the voltage feedback value of the common grid connection point after the previous voltage adjustment, the preset voltage benchmark value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the reactive power distribution coefficient of the photovoltaic inverter, and the preset safety constraint verification rules.

[0055] Among them, the voltage feedback value U'(t) of the public grid connection point after the previous voltage regulation can be obtained in real time by voltage detection elements, such as voltage transformers.

[0056] The voltage deviation at the common grid connection point is: preset voltage reference value U_ref - current voltage U(t). The reactive power allocation factor α_i for each photovoltaic inverter represents the rated capacity percentage of each inverter. The formula for calculating the reactive power allocation factor α_i is: α_i = P_rated_i / P_rated_i; The preset security constraint verification rules are two-level security constraint verification, including local security constraints and global security constraints.

[0057] In some embodiments, the target reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous voltage regulation, the preset voltage reference value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the reactive power allocation coefficient of the photovoltaic inverter, and the preset safety constraint verification rules. This includes: determining the dynamic droop coefficient adjustment value based on the preset voltage reference value, the preset voltage hysteresis threshold, and the voltage feedback value of the common grid connection point after the previous voltage regulation; determining the initial reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient reference value, the voltage deviation of the common grid connection point, and the reactive power allocation coefficient of the photovoltaic inverter; and determining the target reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment, and the preset safety constraint verification rules.

[0058] The formula for calculating the dynamic droop coefficient adjustment value k_V_i_adj(t) based on the preset voltage reference value U_ref, the preset voltage hysteresis threshold ΔU, and the voltage feedback value U'(t) of the common grid connection point after the previous voltage regulation is as follows: k_V_i_adj(t)=(1+(U'(t)-(U_ref-ΔU)) / U_ref); Specifically, no voltage regulation is required when the current voltage regulation condition is determined to be a steady-state, no-voltage-regulation condition. When the current voltage regulation condition is an emergency voltage regulation condition or when transitioning from an emergency voltage regulation condition to an iterative supplementary regulation condition, the centralized controller calculates a unified dynamic droop coefficient reference value k_V_base(t) for the entire system. After receiving k_V_base(t), the local controller of each photovoltaic inverter, combined with the common grid connection point voltage feedback value U'(t) after the previous round of voltage regulation, calculates the local dynamic droop coefficient fine-tuning value k_V_i_adj(t), i.e., the dynamic droop coefficient adjustment value. Then, based on the dynamic droop coefficient reference value, the voltage deviation of the common grid connection point, and the reactive power distribution coefficient of the photovoltaic inverter, the initial reactive power adjustment amount of each photovoltaic inverter is calculated. Finally, the final reactive power adjustment (i.e., target reactive power adjustment) of each photovoltaic inverter is dynamically determined based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment amount, and the preset safety constraint verification rules. This allows for subsequent updates to the current reactive power output value based on the target reactive power adjustment amount, thereby dynamically adjusting the voltage at the common grid connection point and achieving overvoltage management when photovoltaic inverters are connected to the distribution network. Therefore, this embodiment overcomes the action conflicts and voltage overshoot problems caused by independent decision-making based on local information by multiple inverters in distributed control technologies by using a centralized controller to uniformly sense the system voltage status and generate reference control commands (i.e., target reactive power adjustment amounts), achieving consistency in the voltage regulation target across the entire network. Furthermore, through a reactive power allocation mechanism based on the inverter's rated capacity ratio, it ensures that each device undertakes voltage regulation tasks according to its capacity proportion, avoiding the problem of some devices being overloaded while others are underutilized.

[0059] In some embodiments, determining the initial reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient reference value, the voltage deviation at the common grid connection point, and the reactive power allocation coefficient of the photovoltaic inverter includes: determining the total global reactive power adjustment based on the dynamic droop coefficient reference value and the voltage deviation at the common grid connection point; and determining the initial reactive power adjustment of the photovoltaic inverter based on the total global reactive power adjustment and the reactive power allocation coefficient of the photovoltaic inverter.

[0060] Specifically, based on the dynamic droop coefficient base value k_V_base(t) and the voltage deviation at the common grid connection point (U_ref-U(t)), the formula for calculating the global total reactive power adjustment ΔQ_total(t) is as follows: ΔQ_total(t)=k_V_base(t)×(U_ref-U(t)); Based on the total global reactive power adjustment ΔQ_total(t) and the reactive power allocation coefficient α_i of the photovoltaic inverter, the formula for calculating the initial reactive power adjustment ΔQ_i_alloc(t) of a single photovoltaic inverter is as follows: ΔQ_i_alloc(t)=α_i×ΔQ_total(t); In some embodiments, determining the target reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment amount, and the preset safety constraint verification rules includes: determining the intermediate reactive power adjustment amount of the photovoltaic inverter based on the dynamic droop coefficient adjustment value and the initial reactive power adjustment amount; and performing safety constraint verification on the intermediate reactive power adjustment amount using the preset safety constraint verification rules to determine the target reactive power adjustment amount of the photovoltaic inverter.

[0061] Specifically, based on the dynamic droop coefficient adjustment value k_V_i_adj(t) and the initial reactive power adjustment ΔQ_i_alloc(t), the calculation formula for the intermediate reactive power adjustment ΔQ_i_corr(t) (i.e., the precise reactive power adjustment) of the photovoltaic inverter is as follows: ΔQ_i_corr(t)=ΔQ_i_alloc(t)×(1+(U'(t)-(U_ref-ΔU)) / U_ref); In some embodiments, a preset safety constraint verification rule is used to perform safety constraint verification on the intermediate reactive power adjustment to determine the target reactive power adjustment of the photovoltaic inverter. This includes: determining a step-size limit adjustment based on the intermediate reactive power adjustment and the maximum reactive power adjustment step size of the photovoltaic inverter; determining a predicted reactive power output value based on the current reactive power output value and the step-size limit adjustment; determining the target reactive power adjustment based on the current allowed reactive power upper limit and the current reactive power output value when the predicted reactive power output value is less than the current allowed reactive power upper limit or the rated reactive power upper limit; and determining the target reactive power adjustment based on the step-size limit adjustment when the predicted reactive power output value is greater than or equal to the current allowed reactive power upper limit or the rated reactive power upper limit.

[0062] The preset safety constraint verification rule is a two-level safety constraint verification, including local safety constraints and global safety constraints. Local safety constraints are implemented by limiting the reactive power adjustment step size, specifically: first, the adjustment amount after step size limitation (i.e., the step size limitation adjustment amount) ΔQ_i_lim(t) is calculated, and its calculation formula is: ΔQ_i_lim(t)=max(-ΔQ_max, min(ΔQ_i_corr(t), ΔQ_max)); Wherein, ΔQ_max represents the maximum allowable reactive power adjustment step size for a single photovoltaic inverter, and its value ranges from 5% to 10% of the absolute value of the rated reactive power upper limit of the photovoltaic inverter.

[0063] Then, the adjusted reactive power output value (i.e., the predicted reactive power output value) Q_i_pred(t) is predicted, and its calculation formula is as follows: Q_i_pred(t)=Q_i_curr(t)+ΔQ_i_lim(t); Where Qi_i_curr(t) represents the reactive power output value.

[0064] Next, it is determined whether the predicted reactive power output value Q_i_pred(t) is less than the current allowed reactive power limit Q_allow_i(t) or the rated reactive power limit Q_rated_i of the photovoltaic inverter.

[0065] If the predicted reactive power output value Q_i_pred(t) is less than the current allowable reactive power limit Q_allow_i(t) or the rated reactive power limit Q_rated_i of the photovoltaic inverter, then the final safe reactive power adjustment (i.e., the target reactive power adjustment) ΔQ_i_safe(t) is determined as follows: ΔQ_i_safe(t)=Q_allow_i(t)-Q_i_curr(t); Otherwise, the final safe reactive power adjustment (i.e., the target reactive power adjustment) ΔQ_i_safe(t) is determined as follows: ΔQ_i_safe(t) = ΔQ_i_lim(t); The formula for calculating the current allowed reactive power limit Q_allow_i(t) is as follows: ; In some embodiments, the overvoltage control method for the distribution network further includes: verifying that the total apparent power of all photovoltaic inverters after adjustment does not exceed the sum of the rated apparent power of each photovoltaic inverter.

[0066] The global security constraint is: the total apparent power of all photovoltaic inverters after adjustment shall not exceed the sum of the rated apparent power of each inverter.

[0067] Step 140: Update the current reactive power output value according to the target reactive power adjustment amount, and if the current voltage is greater than the preset voltage difference, return to repeat the step of determining the dynamic droop coefficient reference value until the current voltage is less than or equal to the preset voltage difference, then stop the iteration.

[0068] The preset voltage difference is: preset voltage reference value U_ref - preset voltage hysteresis threshold ΔU.

[0069] Specifically, after obtaining the final reactive power adjustment amount (i.e., the target reactive power adjustment amount) for safety and compliance of each photovoltaic inverter, each photovoltaic inverter outputs reactive power according to the final reactive power adjustment amount ΔQ_i_safe(t) and simultaneously feeds back its operating status to the central controller. The central controller collects the current voltage U(t) after voltage regulation. If U(t) > U_ref – ΔU, it means that the current voltage does not meet the standard. Then, steps 120 to 140 are repeated for iterative adjustment until U(t) ≤ U_ref – ΔU.

[0070] Each photovoltaic inverter updates its output reactive power (i.e., updates the current reactive power output value) according to the final reactive power adjustment amount ΔQ_i_safe(t). This is done by outputting reactive power according to Q_i(t)=Q_i_curr(t)+ΔQ_i_safe(t) and simultaneously updating the current reactive power output value Q_i_curr(t) =Q_i(t).

[0071] Therefore, through a closed-loop iterative control strategy, when a single adjustment fails to fully meet the target, fine-tuning can be automatically initiated to gradually converge to the target voltage range, ensuring long-term voltage stability.

[0072] It is understood that the overvoltage control method for distribution networks provided in this application provides system-level coordination by deploying a centralized controller at the common grid connection point of multiple photovoltaic inverters. The centralized controller determines the voltage regulation demand (i.e., determines the current voltage regulation condition) based on the real-time voltage and generates a baseline control strategy (i.e., the target reactive power adjustment amount). Each photovoltaic inverter then executes the baseline control strategy after localization adaptation and safety verification based on its own capacity (i.e., reactive power allocation coefficient) and operating status. The core innovation of this application lies in the introduction of a dynamic droop coefficient model, a reactive power balancing allocation mechanism based on capacity ratio, and a two-level safety constraint, thereby achieving precise, coordinated, and safe overvoltage control. This provides a photovoltaic-connected distribution network overvoltage control method with strong coordination, excellent adaptability, and high safety, solving the problems of regulation conflicts caused by independent decision-making by multiple inverters, the inability of fixed droop coefficients to adapt to dynamic conditions, and equipment risks caused by the lack of safety verification in related technologies using distributed droop control. Furthermore, the method of this application has the following beneficial effects: First, by using a centralized controller to uniformly sense the system voltage status and generate reference control commands, the problem of action conflict and voltage overshoot caused by multiple inverters making independent decisions based on local information in the distributed control of related technologies is overcome, thus achieving consistency of the voltage regulation target across the entire network.

[0073] Secondly, by constructing a two-factor dynamic droop coefficient model, the parameters are adaptively adjusted according to the voltage deviation and photovoltaic output changes, which solves the problem of poor adaptability of fixed coefficients and improves the voltage stabilization effect under complex working conditions.

[0074] Third, a reactive power allocation mechanism based on the inverter's rated capacity ratio is used to ensure that each device undertakes voltage regulation tasks according to its capacity proportion, avoiding overload of some devices while underutilization of others. Furthermore, combined with local output boundary constraints and system-level apparent power verification, reactive power commands are strictly limited to the safe operating range of the equipment, fundamentally eliminating the risk of equipment overload or grid disconnection caused by overmodulation.

[0075] Fourth, through a closed-loop iterative control strategy, fine-tuning can be automatically initiated when a single adjustment fails to fully meet the target, gradually converging to the target voltage range and ensuring long-term voltage stability. Furthermore, the method in this application does not rely on line impedance parameters that are difficult to measure accurately; it has a clear structure, is easy to deploy, and possesses good engineering applicability and promotional value, effectively supporting the safe and high-quality operation of high-proportion photovoltaic distribution networks.

[0076] Figure 2 This is a schematic diagram of the overall process of an overvoltage control method for a distribution network provided in an embodiment of this application. For example, see [link to relevant documentation]. Figure 2 The overall implementation process of the overvoltage control method for this power distribution network includes: Step S1, Data Acquisition: Deploy a centralized controller at the common grid connection point of multiple photovoltaic inverters. The centralized controller collects the common grid connection point voltage U(t), the active power output value P_i(t) of each photovoltaic inverter, and the rated parameters of each photovoltaic inverter in real time. At the same time, the local controller of each photovoltaic inverter records its current reactive power output value Q_i_curr(t).

[0077] Step S2, Voltage regulation requirement determination: Based on the current voltage U(t) of the collected common grid connection point, combined with the preset voltage reference value U_ref and voltage hysteresis threshold ΔU, the current voltage regulation condition is determined.

[0078] Step S3, Dynamic droop coefficient calculation: Based on the current voltage regulation condition determined in step S2, the central controller calculates the unified dynamic droop coefficient base value k_V_base(t) for the entire system; after receiving k_V_base(t), the local controller of each photovoltaic inverter calculates the local dynamic droop coefficient fine-tuning value k_V_i_adj(t) by combining it with the common grid connection point voltage feedback value U'(t) after the previous round of voltage regulation.

[0079] Step S4, Reactive Power Adjustment Allocation and Correction: The centralized controller calculates the global total reactive power adjustment ΔQ_total(t) based on the dynamic droop coefficient base value k_V_base(t) and the voltage deviation at the common grid connection point (U_ref-U(t)). Then, according to the rated capacity ratio of each photovoltaic inverter, the initial reactive power adjustment ΔQ_i_alloc(t) is allocated to each inverter. Each local controller then combines the dynamic droop coefficient fine-tuning value k_V_i_adj(t) to correct the initial reactive power adjustment, obtaining the precise reactive power adjustment ΔQ_i_corr(t).

[0080] Step S5, Safety constraint verification: Perform a two-level safety constraint verification on the precise reactive power adjustment ΔQ_i_corr(t) obtained in step S4 to obtain the final safe and compliant reactive power adjustment ΔQ_i_safe(t).

[0081] Step S6, Reactive Power Output Control and Closed-Loop Iteration: Each photovoltaic inverter outputs reactive power according to the final reactive power adjustment amount ΔQ_i_safe(t) and synchronously feeds back the operating status to the centralized controller; The centralized controller collects the common grid connection point voltage U'(t) after voltage regulation. If U'(t)>U_ref-ΔU (not up to standard), then steps S3 to S6 are repeated for iterative adjustment until U'(t)≤U_ref–ΔU.

[0082] For example, taking a low-voltage photovoltaic distribution network containing 8 photovoltaic inverters (e.g., 6 10kW inverters and 2 20kW inverters) as an example, the effectiveness of the overvoltage control method for photovoltaic grid connection provided in this application embodiment is verified by building a simulation model, as follows: For example, the core parameter settings of the simulation implementation example of the method provided in this application embodiment are shown in Table 1 below.

[0083] Table 1: Core Parameter Settings Table

[0084] Figure 3 This is a schematic diagram of the total photovoltaic output variation curve provided in the embodiments of this application. For example, it simulates four typical output conditions of the photovoltaic inverter, and their output conditions are as follows: Figure 3 As shown, specifically: Between 0s and 30s, the total output of photovoltaic power stabilizes at 40kW, which is a low-output condition. At this time, the active power gap in the distribution network is relatively large, and low voltage is likely to occur.

[0085] Between 31s and 60s, the total photovoltaic output linearly increases from 40kW to 100kW, which is the output increase condition. The sudden increase in active power can easily cause overvoltage at the grid connection point.

[0086] Between 61s and 90s, the total photovoltaic output linearly decreases from 100kW to 50kW, which is a power reduction condition. A sudden drop in active power can easily lead to a voltage drop.

[0087] Between 91s and 120s, the total photovoltaic output linearly increases from 50kW to 80kW, which is the output recovery condition. Output fluctuations can easily cause voltage oscillations.

[0088] This demonstrates that the entire power output process covers the typical operating condition of "low output → rapid increase → decrease → rebound," effectively verifying the adaptability of the overvoltage mitigation method under different photovoltaic power output scenarios. This curve provides a typical fluctuating operating condition basis for subsequent verification of the overvoltage mitigation effect, ensuring that the simulation scenario closely matches the actual photovoltaic power output characteristics. Specific simulation results are as follows: Figure 4 and Figure 5 As shown.

[0089] Figure 4 This is a schematic diagram of the voltage variation curve at the common grid connection point provided in an embodiment of this application. Figure 4 As can be seen, the overvoltage regulation method for distribution networks provided in this application, through hierarchical voltage regulation logic (rapid adjustment above 428V, fine adjustment between 424-428V, and stable control ≤424V), achieves full-process control of the grid connection point voltage within the qualified range of 428V, and more than 75% of the time is within the optimal range of 424V, thus solving the core problem of excessive voltage oscillation in related technologies.

[0090] Figure 5 This is a schematic diagram of the reactive power output curve of a typical inverter provided in the embodiments of this application. The overvoltage regulation method for the distribution network provided in the embodiments of this application adopts a reactive power control strategy of "distributing reactive power according to the inverter capacity ratio" and "two-level safety constraint verification", such as... Figure 5 Simulation results demonstrate the effectiveness of the relevant strategies. For example, taking the 10kW inverter #1 and the 20kW inverter #7 as examples, their reactive power output ratio is strictly ≈2:1, which perfectly matches the capacity ratio, and the reactive power output of the inverters does not exceed the rated upper limit, so there is no risk of overload.

[0091] Figure 6 This is a schematic block diagram of an overvoltage control system for a distribution network provided in an embodiment of this application. This application also provides an overvoltage control system for a distribution network; please refer to [link to relevant documentation]. Figure 6 The overvoltage control system 100 of the power distribution network includes: a first determining module 101, used to determine the current voltage regulation condition based on the current voltage of the common grid connection point of multiple photovoltaic inverters, a preset voltage reference value, and a preset voltage hysteresis threshold; a second determining module 102, used to determine the dynamic droop coefficient reference value when the current voltage regulation condition is transitioning from an emergency voltage regulation condition to an emergency voltage regulation condition or an iterative supplementary regulation condition; and a third determining module 103, used to determine the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous round of voltage regulation, the preset voltage reference value, the preset voltage hysteresis threshold, and the voltage deviation of the common grid connection point. The system uses the reactive power distribution coefficient of the photovoltaic inverter and preset safety constraint verification rules to determine the target reactive power adjustment amount of the photovoltaic inverter. The voltage deviation of the common grid connection point is the difference between the preset voltage reference value and the current voltage of the common grid connection point. The update module 104 is used to update the current reactive power output value according to the target reactive power adjustment amount. The iteration module 105 is used to return to the step of determining the dynamic droop coefficient reference value when the current voltage is greater than the preset voltage difference, until the current voltage is less than or equal to the preset voltage difference, and then stop the iteration. The preset voltage difference is the difference between the preset voltage reference value and the preset voltage hysteresis threshold.

[0092] The technical solution of this application provides an overvoltage control system for a distribution network. By dynamically determining the dynamic droop coefficient benchmark value and the target reactive power adjustment amount of the photovoltaic inverter based on real-time voltage and inverter operating data, under emergency voltage regulation conditions or transitioning from emergency voltage regulation conditions to iterative adjustment conditions, the system dynamically updates the current reactive power output value of the photovoltaic inverter. This allows for dynamic adjustment of the voltage at the common grid connection point based on the updated current reactive power output value, thereby stabilizing the voltage at the common grid connection point and achieving closed-loop control of overvoltage when photovoltaics are connected to the distribution network.

[0093] In some embodiments, the first determining module 101 is further configured to: determine the current voltage regulation condition as a steady-state no voltage regulation condition when the current voltage is less than or equal to the difference between a preset voltage reference value and a preset voltage hysteresis threshold; determine the current voltage regulation condition as an emergency no voltage regulation condition when the current voltage is greater than the preset voltage reference value; and determine the current voltage regulation condition as an iterative adjustment condition when the current voltage is greater than the difference between the preset voltage reference value and the preset voltage hysteresis threshold value, but less than the preset voltage reference value.

[0094] In some embodiments, the formula for calculating the dynamic droop coefficient base value is: k_V_base(t)=k_V0×k1×k2; Wherein, k_V_base(t) represents the reference value of the dynamic droop coefficient; k_V0 represents the reference droop coefficient; k1 represents the voltage deviation correction factor; and k2 represents the total active power output correction factor.

[0095] In some embodiments, the voltage deviation correction factor is calculated using the formula: k1 = 1 + min(0.8 × (U(t) - U_ref) / (0.03 × U_N), 0.8); The formula for calculating the total active power output correction factor is: k2=1-min(0.5×(ΣP_i(t) / ΣP_rated_i), 0.5); Where U(t) represents the current voltage; U_ref represents the preset voltage reference value; U_N represents the rated voltage of the distribution network; P_i(t) represents the active power output value; and P_rated_i represents the rated active capacity.

[0096] In some embodiments, the third determining module 103 is further configured to: determine the dynamic droop coefficient adjustment value based on a preset voltage reference value, a preset voltage hysteresis threshold, and the voltage feedback value of the common grid connection point after the previous voltage regulation; determine the initial reactive power adjustment amount of the photovoltaic inverter based on the dynamic droop coefficient reference value, the voltage deviation of the common grid connection point, and the reactive power distribution coefficient of the photovoltaic inverter; and determine the target reactive power adjustment amount of the photovoltaic inverter based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment amount, and the preset safety constraint verification rules.

[0097] In some embodiments, the third determining module 103 is further configured to: determine the total global reactive power adjustment based on the dynamic droop coefficient reference value and the voltage deviation at the common grid connection point; and determine the initial reactive power adjustment of the photovoltaic inverter based on the total global reactive power adjustment and the reactive power distribution coefficient of the photovoltaic inverter.

[0098] In some embodiments, the formula for calculating the total global reactive power adjustment is: ΔQ_total(t)=k_V_base(t)×(U_ref-U(t)); The formula for calculating the initial reactive power adjustment of a photovoltaic inverter is: ΔQ_i_alloc(t)=α_i×ΔQ_total(t); Wherein, ΔQ_total(t) represents the total global reactive power adjustment; k_V_base(t) represents the dynamic droop coefficient reference value; ΔQ_i_alloc(t) represents the initial reactive power adjustment; α_i represents the reactive power allocation coefficient; U(t) represents the current voltage; and U_ref represents the preset voltage reference value.

[0099] In some embodiments, the third determining module 103 is further configured to: determine the intermediate reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient adjustment value and the initial reactive power adjustment amount; and perform a safety constraint verification on the intermediate reactive power adjustment amount using a preset safety constraint verification rule to determine the target reactive power adjustment amount of the photovoltaic inverter.

[0100] In some embodiments, the formula for calculating the intermediate reactive power adjustment of a photovoltaic inverter is: ΔQ_i_corr(t)=ΔQ_i_alloc(t)×(1+(U'(t)-(U_ref-ΔU)) / U_ref); Where ΔQ_i_corr(t) represents the intermediate reactive power adjustment; ΔQ_i_alloc(t) represents the initial reactive power adjustment; U'(t) represents the voltage feedback value of the common grid connection point after the previous voltage regulation; U_ref represents the preset voltage reference value; and ΔU represents the preset voltage hysteresis threshold.

[0101] In some embodiments, the third determining module 103 is further configured to: determine a step-size limit adjustment amount based on the intermediate reactive power adjustment amount and the maximum reactive power adjustment step size of the photovoltaic inverter; determine a predicted reactive power output value based on the current reactive power output value and the step-size limit adjustment amount; determine a target reactive power adjustment amount based on the current allowed reactive power upper limit and the current reactive power output value if the predicted reactive power output value is less than the current allowed reactive power upper limit or the rated reactive power upper limit; and determine a target reactive power adjustment amount based on the step-size limit adjustment amount if the predicted reactive power output value is greater than or equal to the current allowed reactive power upper limit or the rated reactive power upper limit.

[0102] In some embodiments, the formula for calculating the step size limit adjustment is: ΔQ_i_lim(t)=max(-ΔQ_max, min(ΔQ_i_corr(t), ΔQ_max)); The formula for calculating the predicted reactive power output is: Q_i_pred(t)=Q_i_curr(t)+ΔQ_i_lim(t); The formula for calculating the target reactive power adjustment is: If the predicted reactive power output value is less than the current allowable reactive power limit or the rated reactive power limit of the photovoltaic inverter, then the formula for calculating the target reactive power adjustment is as follows: ΔQ_i_safe(t)=Q_allow_i(t)-Q_i_curr(t); Otherwise, the formula for calculating the target reactive power adjustment is: ΔQ_i_safe(t) = ΔQ_i_lim(t); Where Q_allow_i(t) represents the current allowed reactive power limit; The current formula for calculating the maximum allowable reactive power is: ; Wherein, ΔQ_max represents the maximum allowable reactive power adjustment step size for a single photovoltaic inverter; Q_i_curr(t) represents the reactive power output value; ΔQ_i_lim(t) represents the step size limit adjustment amount; ΔQ_i_safe(t) represents the target reactive power adjustment amount; Q_allow_i(t) represents the current allowable reactive power upper limit; ΔQ_i_corr(t) represents the intermediate reactive power adjustment amount; Q_i_pred(t) represents the predicted reactive power output value; and Q_rated_i represents the rated reactive power upper limit.

[0103] In some embodiments, the system 100 further includes a verification module for verifying that the total apparent power of all photovoltaic inverters after adjustment does not exceed the sum of the rated apparent power of each photovoltaic inverter.

[0104] In some embodiments, the formula for calculating the dynamic droop coefficient adjustment value is as follows: k_V_i_adj(t)=(1+(U'(t)-(U_ref-ΔU)) / U_ref); Wherein, k_V_i_adj(t) represents the dynamic droop coefficient adjustment value; U'(t) represents the voltage feedback value of the common grid connection point after the previous voltage regulation; U_ref represents the preset voltage reference value; and ΔU represents the preset voltage hysteresis threshold.

[0105] In some embodiments, the system 100 is further configured to: not perform voltage regulation when the current voltage regulation condition is a steady-state non-voltage regulation condition, or when transitioning from a steady-state non-voltage regulation condition to an iterative supplementary regulation condition.

[0106] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0107] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for overvoltage control in a power distribution network, characterized in that, The power distribution network is connected to multiple photovoltaic inverters; the method includes: The current voltage regulation condition is determined based on the current voltage of the common grid connection point of the multiple photovoltaic inverters, the preset voltage reference value, and the preset voltage hysteresis threshold. When the current voltage regulation condition is an emergency voltage regulation condition or when transitioning from the emergency voltage regulation condition to the iterative adjustment condition, a reference value for the dynamic droop coefficient is determined. Based on the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous voltage adjustment, the preset voltage reference value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the photovoltaic inverter, and the preset safety constraint verification rules, the target reactive power adjustment of the photovoltaic inverter is determined; wherein, the voltage deviation of the common grid connection point is the difference between the preset voltage reference value and the current voltage of the common grid connection point; The current reactive power output value is updated according to the target reactive power adjustment amount, and if the current voltage is greater than the preset voltage difference, the step of determining the dynamic droop coefficient reference value is repeated until the current voltage is less than or equal to the preset voltage difference, at which point the iteration stops; the preset voltage difference is the difference between the preset voltage reference value and the preset voltage hysteresis threshold.

2. The method according to claim 1, characterized in that, The step of determining the current voltage regulation condition based on the current voltage of the common grid connection point of the multiple photovoltaic inverters, a preset voltage reference value, and a preset voltage hysteresis threshold includes: If the current voltage is less than or equal to the difference between the preset voltage reference value and the preset voltage hysteresis threshold, the current voltage regulation condition is determined to be a steady-state no voltage regulation condition. If the current voltage is greater than the preset voltage reference value, the current voltage regulation condition is determined to be the emergency voltage regulation condition. If the current voltage is greater than the difference between the preset voltage reference value and the preset voltage hysteresis threshold, but less than the preset voltage reference value, the current voltage regulation condition is determined to be the iterative adjustment condition.

3. The method according to claim 1, characterized in that, The formula for calculating the dynamic droop coefficient benchmark value is as follows: k_V_base(t) = k_V0 × k1 × k2; Wherein, k_V_base(t) represents the reference value of the dynamic droop coefficient; k_V0 represents the reference droop coefficient; k1 represents the voltage deviation correction factor; and k2 represents the total active power output correction factor.

4. The method according to claim 3, characterized in that, The formula for calculating the voltage deviation correction factor is as follows: k1=1+min(0.8×(U(t)-U_ref) / (0.03×U_N), 0.8); The formula for calculating the total active power output correction factor is as follows: k2=1-min(0.5×(ΣP_i(t) / ΣP_rated_i), 0.5); Wherein, U(t) represents the current voltage; U_ref represents the preset voltage reference value; U_N represents the rated voltage of the distribution network; P_i(t) represents the active power output value; and P_rated_i represents the rated active capacity.

5. The method according to claim 1, characterized in that, The step of determining the target reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous voltage adjustment, the preset voltage reference value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the reactive power distribution coefficient of the photovoltaic inverter, and the preset safety constraint verification rules includes: Based on the preset voltage reference value, the preset voltage hysteresis threshold, and the voltage feedback value of the common grid connection point after the previous voltage regulation, determine the dynamic droop coefficient adjustment value; The initial reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient benchmark value, the voltage deviation of the common grid connection point, and the reactive power distribution coefficient of the photovoltaic inverter. The target reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment amount, and the preset safety constraint verification rules.

6. The method according to claim 5, characterized in that, The step of determining the initial reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient reference value, the voltage deviation of the common grid connection point, and the reactive power distribution coefficient of the photovoltaic inverter includes: The total global reactive power adjustment is determined based on the dynamic droop coefficient reference value and the voltage deviation at the common grid connection point. The initial reactive power adjustment of the photovoltaic inverter is determined based on the total global reactive power adjustment and the reactive power allocation coefficient of the photovoltaic inverter.

7. The method according to claim 6, characterized in that, The formula for calculating the total global reactive power adjustment is as follows: ΔQ_total(t)=k_V_base(t)×(U_ref-U(t)); The formula for calculating the initial reactive power adjustment of the photovoltaic inverter is as follows: ΔQ_i_alloc(t)=α_i×ΔQ_total(t); Wherein, ΔQ_total(t) represents the global total reactive power adjustment; k_V_base(t) represents the dynamic droop coefficient reference value; ΔQ_i_alloc(t) represents the initial reactive power adjustment; α_i represents the reactive power allocation coefficient; U(t) represents the current voltage; and U_ref represents the preset voltage reference value.

8. The method according to claim 5, characterized in that, The step of determining the target reactive power adjustment of the photovoltaic inverter based on the dynamic droop coefficient adjustment value, the initial reactive power adjustment amount, and the preset safety constraint verification rule includes: The intermediate reactive power adjustment of the photovoltaic inverter is determined based on the dynamic droop coefficient adjustment value and the initial reactive power adjustment amount. Using the preset safety constraint verification rules, the intermediate reactive power adjustment is verified to determine the target reactive power adjustment of the photovoltaic inverter.

9. The method according to claim 8, characterized in that, The formula for calculating the intermediate reactive power adjustment of the photovoltaic inverter is as follows: ΔQ_i_corr(t)=ΔQ_i_alloc(t)×(1+(U'(t)-(U_ref-ΔU)) / U_ref); Wherein, ΔQ_i_corr(t) represents the intermediate reactive power adjustment amount; ΔQ_i_alloc(t) represents the initial reactive power adjustment amount; U'(t) represents the voltage feedback value of the common grid connection point after the previous voltage regulation; U_ref represents the preset voltage reference value; and ΔU represents the preset voltage hysteresis threshold.

10. The method according to claim 8, characterized in that, The step of using the preset safety constraint verification rules to perform safety constraint verification on the intermediate reactive power adjustment amount to determine the target reactive power adjustment amount of the photovoltaic inverter includes: The step size limit adjustment amount is determined based on the intermediate reactive power adjustment amount and the maximum reactive power adjustment step size of the photovoltaic inverter; The predicted reactive power output value is determined based on the current reactive power output value and the step size limit adjustment amount; If the predicted reactive power output value is less than the current allowable reactive power limit or the rated reactive power limit, the target reactive power adjustment amount is determined based on the current allowable reactive power limit and the current reactive power output value. If the predicted reactive power output value is greater than or equal to the current allowed reactive power limit or the rated reactive power limit, the target reactive power adjustment amount is determined according to the step size limit adjustment amount.

11. The method according to claim 10, characterized in that, The formula for calculating the step size limit adjustment is: ΔQ_i_lim(t)=max(-ΔQ_max, min(ΔQ_i_corr(t), ΔQ_max)); The formula for calculating the predicted reactive power output value is as follows: Q_i_pred(t)=Q_i_curr(t)+ΔQ_i_lim(t); The formula for calculating the target reactive power adjustment is: If the predicted reactive power output value is less than the current allowed reactive power limit or the rated reactive power limit of the photovoltaic inverter, then the calculation formula for determining the target reactive power adjustment is: ΔQ_i_safe(t)=Q_allow_i(t)-Q_i_curr(t); Otherwise, the formula for calculating the target reactive power adjustment is: ΔQ_i_safe(t) = ΔQ_i_lim(t); Where Q_allow_i(t) represents the current allowed reactive power limit; The formula for calculating the current allowable reactive power limit is as follows: ； Wherein, ΔQ_max represents the maximum allowable reactive power adjustment step size for a single photovoltaic inverter; Q_i_curr(t) represents the reactive power output value; ΔQ_i_lim(t) represents the step size limit adjustment amount; ΔQ_i_safe(t) represents the target reactive power adjustment amount; Q_allow_i(t) represents the current allowable reactive power upper limit; ΔQ_i_corr(t) represents the intermediate reactive power adjustment amount; Q_i_pred(t) represents the predicted reactive power output value; and Q_rated_i represents the rated reactive power upper limit.

12. The method according to claim 8, characterized in that, The method further includes: verifying that the total apparent power of all the photovoltaic inverters after adjustment does not exceed the sum of the rated apparent power of each photovoltaic inverter.

13. The method according to claim 5, characterized in that, The formula for calculating the dynamic droop coefficient adjustment value is as follows: k_V_i_adj(t)=(1+(U'(t)-(U_ref-ΔU)) / U_ref); Wherein, k_V_i_adj(t) represents the dynamic droop coefficient adjustment value; U'(t) represents the voltage feedback value of the common grid connection point after the previous voltage regulation; U_ref represents the preset voltage reference value; and ΔU represents the preset voltage hysteresis threshold.

14. The method according to claim 1, characterized in that, The method further includes: when the current voltage regulation condition is a steady-state no voltage regulation condition, or when transitioning from the steady-state no voltage regulation condition to the iterative supplementary regulation condition, voltage regulation is not performed.

15. An overvoltage control system for a power distribution network, characterized in that, The power distribution network is connected to multiple photovoltaic inverters; the system includes: The first determining module is used to determine the current voltage regulation condition based on the current voltage of the common grid connection point of the multiple photovoltaic inverters, the preset voltage reference value, and the preset voltage hysteresis threshold. The second determining module is used to determine the dynamic droop coefficient reference value when the current voltage regulation condition is an emergency voltage regulation condition or when the voltage regulation condition transitions to an iterative adjustment condition. The third determining module is used to determine the target reactive power adjustment amount of the photovoltaic inverter based on the dynamic droop coefficient reference value, the voltage feedback value of the common grid connection point after the previous voltage adjustment, the preset voltage reference value, the preset voltage hysteresis threshold, the voltage deviation of the common grid connection point, the reactive power distribution coefficient of the photovoltaic inverter, and the preset safety constraint verification rules; wherein, the voltage deviation of the common grid connection point is the difference between the preset voltage reference value and the current voltage of the common grid connection point; The update module is used to update the current reactive power output value according to the target reactive power adjustment amount; An iterative module is used to repeatedly execute the step of determining the dynamic droop coefficient reference value when the current voltage is greater than the preset voltage difference, until the current voltage is less than or equal to the preset voltage difference, at which point the iteration stops; the preset voltage difference is the difference between the preset voltage reference value and the preset voltage hysteresis threshold.

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