Power distribution network multi-element power quality treatment method and device based on time sequence cooperative control

Abstract

This application discloses a method and device for multi-phase power quality management of distribution networks based on time-series coordinated control. The management method includes: isolating and measuring the three-phase voltage and current to obtain the original analog signals, then standardizing them to convert them into digital signals, and obtaining the power quality index parameters of each phase and the power grid system; judging voltage over-limit, three-phase imbalance, and reactive power / power factor based on the digital signals and power quality index parameters, and setting priority ranking rules for the management strategies, performing voltage over-limit processing, imbalance processing, and reactive power / power factor processing in descending order of priority; inserting a delay after completing the processing actions, re-collecting the power grid status data, and judging whether the management effect meets the standards and whether further intervention is needed according to the priority ranking rules, forming a dynamic closed-loop mode with good comprehensive management effect, high economy, and high robustness.

Description

Technical Field

[0001] This invention relates to the field of collaborative power quality management technology, and in particular to a method and apparatus for multi-element power quality management of distribution networks based on time-series collaborative control. Background Technology

[0002] In modern power systems, power quality is a key indicator for measuring power supply reliability and efficiency. Especially in low-voltage distribution networks, such as in rural and suburban areas with long power supply radii, various power quality problems are common due to the randomness and uneven distribution of single-phase loads (such as residential electricity consumption and electric vehicle charging stations), as well as factors such as line impedance, load fluctuations, and distributed photovoltaic (PV) integration. These problems mainly include: three-phase imbalance, voltage deviation (excessively high or low voltage), insufficient reactive power, and low power factor.

[0003] These power quality problems are not isolated; they are often interconnected and mutually influential. For example, three-phase imbalance can lead to localized transformer overheating, neutral line overload, increased line losses, and may further cause voltage imbalance, affecting the normal operation of sensitive equipment and even endangering grid safety. Excessive neutral line current, for instance, can cause overheating or even fire. Insufficient reactive power and low power factor can increase line losses. Voltage deviations can directly damage user equipment, causing it to fail to start or burn out.

[0004] Traditional power quality management solutions typically have limitations. On the one hand, existing technologies often employ separate, single-function devices. For example, independent reactive power compensation devices (such as thyristor-switched capacitors, TSCs) can only effectively compensate for reactive power, but are ineffective at addressing imbalances caused by resistive loads; independent commutator switches can only balance inter-phase loads, but cannot solve reactive power issues or voltage deviations; independent voltage regulation modules can only stabilize voltage, but cannot solve imbalances and reactive power problems. This piecemeal approach often fails to achieve comprehensive power quality improvement. On the other hand, while active power quality management devices such as Static Var Generators (SVG) or Unified Power Quality Conditioners (UPQCs) can simultaneously manage reactive power and imbalances, they are usually expensive, have high inherent losses, and are complex to maintain, making large-scale deployment in vast distribution areas difficult.

[0005] Furthermore, if discrete devices are simply combined, the lack of a unified collaborative control strategy will cause each device to act independently based on its own detection target, which may easily lead to control conflicts (for example, switching capacitors for reactive power compensation while the voltage regulator module is boosting the voltage may cause the voltage to be too high), or the governance response timing may be chaotic, making it difficult to achieve the best comprehensive governance effect. Summary of the Invention

[0006] This application provides a method and apparatus for multi-element power quality management of distribution networks based on time-series collaborative control. It can deeply couple passive / low-source management devices and achieve distributed collaborative management of "source-grid-load" according to a predetermined management strategy. This surpasses the protection value of specific hardware combinations and provides a new, cost-effective "control paradigm" for solving complex coupling problems. It achieves a comprehensive management effect comparable to active devices while also possessing the economy and robustness of passive devices.

[0007] The first aspect of this application provides a method for managing the power quality of a distribution network based on time-series coordinated control, comprising the following steps:

[0008] S10 performs isolated measurements of the three-phase voltage and current at the outlet of the distribution transformer and / or specific nodes to obtain the original analog signal. The original analog signal is then standardized and converted into a digital signal for calculation by the integrated controller, thereby acquiring the power quality index parameters of each phase and the power grid system in real time.

[0009] S20, based on the digital signal and the power quality index parameters, voltage over-limit judgment, three-phase imbalance judgment and reactive power / power factor judgment are performed, and priority sorting rules for governance strategies are set. All event identifiers are described in real time, and voltage over-limit processing, imbalance processing and reactive power / power factor processing are performed in order of priority from high to low. Under the premise of satisfying priority constraints, the optimal control command is calculated and the actions are ensured to be non-conflicting.

[0010] To address three-phase imbalance, a commutation strategy is initiated. The integrated controller uses topology identification to determine the current phase and load size of each commutable branch, calculates the load to be transferred, and performs a commutation operation, executing only one commutation operation at a time. Regarding reactive power / power factor, after the voltage is qualified and the imbalance meets the standard, the current reactive power deficit Q_need is calculated, and a command is sent to the TSC to connect several sets of capacitors for compensation.

[0011] S30 inserts a predetermined delay after completing different processing actions, then re-collects power grid status data, and judges whether the governance effect meets the standard and whether further intervention is needed according to the priority ranking rules, forming a dynamic closed-loop mode of monitoring -> analysis -> decision -> execution -> re-monitoring.

[0012] In one possible implementation, in step S10, the power quality index parameters include the effective value of voltage, the effective value of current, active power, reactive power, power factor, phase angle, frequency, and three-phase imbalance.

[0013] In one possible implementation, in step S20, for voltage exceeding the limit, a voltage quality classification interval and a management strategy are established, wherein, according to the size of the voltage range, the voltage quality classification interval includes, in order, an emergency zone for exceeding the upper limit, a warning zone for exceeding the upper limit, an excellent zone, a warning zone for exceeding the lower limit, and an emergency zone for exceeding the lower limit.

[0014] For emergency zones exceeding the upper limit, the management strategy is as follows: immediately activate the voltage regulation module to reduce the voltage by switching the tap changer. If the voltage regulation capacity is insufficient, inductive reactive power absorption will be carried out in conjunction with it.

[0015] For areas exceeding the upper limit warning zone, the governance strategy is as follows: initiate preventive adjustment, prioritize the absorption of inductive reactive power through reactive power compensation, and if ineffective, fine-tune the voltage regulation module to perform voltage reduction operation;

[0016] For areas with excellent air quality, only monitoring and data recording are performed.

[0017] For areas exceeding the lower limit warning zone, the governance strategy is as follows: initiate preventive adjustment, prioritize the generation of capacitive reactive power through reactive power compensation, and if ineffective, fine-tune the voltage regulation module to perform voltage boosting operation;

[0018] For emergency zones exceeding the lower limit, the management strategy is as follows: immediately activate the voltage regulation module to perform voltage boosting operation by switching taps; if the voltage regulation capacity is insufficient, then perform capacitive reactive power compensation.

[0019] In one possible implementation, in step S20, for three-phase imbalance, a three-phase imbalance classification interval and a management strategy are established, wherein, according to the magnitude of the three-phase imbalance, the three-phase imbalance classification intervals include, in order, a severe imbalance zone, a moderate imbalance zone, a qualified warning zone, and a good zone.

[0020] For the severely unbalanced area, the treatment strategy is as follows: immediately initiate the commutation operation, prioritize switching part of the load of the high current phase in each commutation branch to the light load phase, re-evaluate after each operation, if it is still in the severely unbalanced area and the commutation interval is met, continue commutation, and so on, until it is determined to enter the moderate unbalanced area after re-evaluation.

[0021] For the moderate imbalance zone, the governance strategy is as follows: based on the governance strategy for the severe imbalance zone, reduce the switching branches and extend the switching interval, and continue to perform the cycle of switching, evaluation, switching, and evaluation until the zone is re-evaluated and judged to have entered the qualified warning zone or the excellent zone.

[0022] For qualified early warning areas, only monitoring and trend recording are performed;

[0023] For areas with excellent air quality, monitoring is only conducted.

[0024] In one possible implementation, in step S20, the phase switching operation is allocated based on the optimal load of a greedy / genetic algorithm. In each iteration, the greedy algorithm switches the branch that contributes the most to reducing the imbalance until it can no longer be improved or the number of actions is limited. The genetic algorithm solves for the optimal phase combination by encoding, selection, crossover, and mutation in sequence.

[0025] In one possible implementation, for a qualified warning zone, if the recorded data remains within the qualified warning zone for a predetermined duration, a preventative switching operation is performed during low-load periods. After each operation, a reassessment is conducted. If the zone remains within the qualified warning zone and the switching interval is met, switching continues, and so on, until a reassessment determines that the zone has entered the excellent zone.

[0026] In one possible implementation, in step S20, for reactive power / power factor, a power factor classification interval and a governance strategy are established, wherein according to the magnitude of the power factor, the power factor classification interval includes, in turn, a severely under-compensated area, an under-compensated governance area, a qualified economic area, an excellent area, and an over-compensated area.

[0027] For areas with severe under-compensation, the remediation strategy is to immediately activate the reactive power compensation module, add capacitors according to the calculated amount, compensate to the target value in one go, and reassess after compensation;

[0028] For areas with insufficient power factor, the management strategy is as follows: activate the reactive power compensation module and gradually add the predetermined capacitors until the power factor reaches the qualified economic zone.

[0029] For qualified economic zones, the governance strategy is as follows: monitor the load; if the load is stable and there is no reactive power to adjust, fine-tune the power factor to approach the excellent zone; if frequent switching is required, maintain the status quo.

[0030] For areas with excellent air quality, only data is monitored and recorded;

[0031] For the overcompensation zone, the mitigation strategy is to immediately disconnect a predetermined number of capacitors to bring the power factor back to the lag zone.

[0032] In one possible implementation, in step S20, a queue-style cyclic switching is performed based on the reactive power deviation, and the capacitor bank is dynamically switched according to the reactive power deficit to make the power factor reach the target value, while avoiding frequent switching and circulating current.

[0033] In one possible implementation, the governance method further includes step S40, which involves continuously collecting and analyzing the effective voltage value data after the voltage regulating module completes the tap changer switching action.

[0034] First, short-term average values ​​are calculated and changes are assessed. The integrated controller maintains a sliding data window, and the short-term average value is calculated based on the effective voltage data within the window. The formula is as follows: ;

[0035] in, This represents the effective voltage value calculated in the i-th power frequency cycle before the current time k, where N is the length of the sliding window;

[0036] Subsequently, the integrated controller continuously tracks the changes in the short-term average value and calculates the difference between the current short-term average value and the previous short-term average value, i.e., the rate of change Delta_V_avg(k), where Delta_V_avg(k) = |V_avg(k) - V_avg(k-1)|. Simultaneously, the integrated controller calculates the fluctuation degree of the effective voltage value within the same sliding data window, with the fluctuation degree Sigma(k) calculated using the formula: ;

[0037] Finally, convergence and stability conditions are determined. If condition 1: the short-term average change rate of the effective voltage value is continuously lower than the first preset threshold, i.e., Delta_V_avg(k) < Epsilon_avg, and condition 2: the fluctuation of the effective voltage value is continuously lower than the second preset threshold, i.e., Sigma(k) < Epsilon_sigma, and these two conditions are met for a predetermined number of sampling periods, then the integrated controller determines that the power grid has stabilized and immediately updates the operating status of the voltage regulating module from "in operation" to "idle".

[0038] A second aspect of this application provides a multi-element power quality management device for distribution networks based on time-series coordinated control, used to implement the management method described above. The management device includes:

[0039] The sensing layer includes a sensing unit, a signal processing unit, and a monitoring unit. The sensing unit is used to perform isolated measurements of the three-phase voltage and current at the outlet of the distribution transformer and / or specific nodes of the line to obtain the original analog signal. The signal processing unit is used to standardize the original analog signal and then convert it into a digital signal for calculation by the integrated controller. The monitoring unit is used to calculate in real time to obtain the power quality index parameters of each phase and the power grid system.

[0040] The control layer includes an integrated controller. The integrated controller performs voltage over-limit judgment, three-phase imbalance judgment, and reactive power / power factor judgment based on the digital signal and the power quality index parameters, and sets priority ranking rules for governance strategies, and describes all event identifiers in real time.

[0041] The execution layer performs governance actions based on the judgments of the control layer and the priority ranking rules of the governance strategy.

[0042] Beneficial Effects: Compared with existing technologies, the distribution network multi-element power quality governance method and device based on time-series collaborative control provided in this application ensures that, under limited control resources, the issues with the greatest impact on grid security and stability are addressed first through time-sharing priority collaborative control. This avoids sacrificing high-priority indicators for solving low-priority issues, thus guaranteeing the robustness and security of the governance method (or system). Through state-based interlocking, strategic timing delays, and capacity coordination, control conflicts, system oscillations, or misjudgments can be effectively prevented, further enhancing system robustness and security. Regardless of the technology of future execution units, the collaborative control framework and conflict avoidance mechanism based on time-series priority proposed in this invention are equally applicable, possessing a broader protection scope and longer technical lifespan. Furthermore, it features all-weather online monitoring, intelligent diagnosis, and closed-loop feedback capabilities, achieving refined adaptive control through hierarchical interval evaluation, reducing unnecessary actions, and extending equipment lifespan.

[0043] Furthermore, instead of treating all minor voltage fluctuations as instability, the concepts of "trend" and "fluctuation characteristics" are introduced. By analyzing the short-term average change trend and fluctuation degree of the effective voltage value in real time, it is possible to determine whether the power grid is "calming down" and has "converged" to a new equilibrium. This method can effectively distinguish between the real power grid transient process and the micro-fluctuations caused by filter performance drift and background noise superposition. It can complete the transformation from "static point inspection" to "flexible process assessment". This allows the governance method (or system) to still have a deeper insight into the real operating state of the power grid when facing long-term accumulated filter performance drift and normalized increase in background noise.

[0044] Beyond its direct power quality improvement effects, this application can significantly extend the lifespan of distribution transformers and user equipment. For example, it reduces localized overheating of transformers by lowering negative sequence current and protects user electrical equipment by providing stable and balanced voltage. Simultaneously, it reduces the skill requirements for maintenance personnel and lowers maintenance costs. Through online monitoring and intelligent diagnostics, it enables "condition-based maintenance" instead of "planned maintenance," solidifying expert experience into algorithmic logic and improving maintenance efficiency and intelligence.

[0045] These and other objects, features and advantages of the present invention will become fully apparent from the following detailed description. Attached Figure Description

[0046] Figure 1 A flowchart illustrating the multi-element power quality governance method for distribution networks based on time-series coordinated control, as presented in this application, is shown.

[0047] Figure 2 A schematic diagram of the voltage quality classification range and governance strategy in the governance method of this application is shown.

[0048] Figure 3 A schematic diagram of the three-phase imbalance classification interval and governance strategy in the governance method of this application is shown.

[0049] Figure 4 A schematic diagram of the power factor classification interval and governance strategy in the governance method of this application is shown.

[0050] Figure 5 A schematic diagram of the basic process of the governance method of this application is shown. Detailed Implementation

[0051] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0052] Those skilled in the art should understand that, in the disclosure of this specification, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0053] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will also be understood that terms, such as those defined in commonly used dictionaries, shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art and shall not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein.

[0054] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0055] The root cause of three-phase imbalance in power quality management lies in the fact that while the connection points of a large number of downstream single-phase loads on the three phases are relatively fixed, their usage behavior is random and uneven over time. This results in the actual total load carried by the three phases being unequal at any given moment; that is, the "uneven distribution of load in physical connections" is the cause. In contrast, traditional compensation devices, such as SVG or active power filters (APF), typically address imbalance by "compensation." This involves monitoring the unbalanced current in the grid (considered a "symptom" or "result" of the imbalance) and then injecting a compensating current of equal magnitude but opposite direction into the grid through their own power electronic inverter. This "symptomatic treatment" only "neutralizes" the unbalanced current at the parallel connection point. However, the unbalanced current may still exist on the line between the SVG and the unbalanced load, and the risks of uneven operation and overheating within the transformer may still exist. Furthermore, the SVG itself also incurs losses during energy conversion.

[0056] Currently, the core issue remains: in low-voltage distribution networks with long power supply lines in rural and suburban areas, how to utilize cost-effective and reliable passive or low-power equipment to achieve coordinated, efficient, and comprehensive management of these interrelated problems that may cause control conflicts, such as voltage deviation, three-phase imbalance, and insufficient reactive power, caused by factors such as uneven distribution of single-phase loads, line impedance, and load fluctuations. This is to improve the safety, stability, and economy of power grid operation, while avoiding the limitations of traditional separate management solutions and the cost and complexity of expensive active equipment.

[0057] refer to Figures 1 to 5 The first aspect of this application provides a multi-faceted power quality management method for distribution networks based on time-series coordinated control. This method deeply couples passive or low-energy devices such as load commutation, reactive power compensation, and voltage regulation through a unified intelligent integrated controller (also referred to as a system). This enables coordinated management of various power quality problems, including voltage deviation, three-phase imbalance, and insufficient reactive power, forming a multi-objective optimization control strategy for comprehensive power quality management. Specifically, this management method includes the following steps:

[0058] S10 uses high-precision voltage transformers (VT) and current transformers (CT) to isolate and measure the three-phase voltage and current at the distribution transformer outlet and / or specific nodes (such as branches, line ends, and new energy access points), obtaining raw analog signals. These raw analog signals are then standardized by signal conditioning circuitry (including filtering, amplification, and level conversion) and converted into digital signals for calculation by the integrated controller. This allows for real-time acquisition of power quality parameters for each phase and the power grid system, including RMS voltage (U), RMS current (I), active power (P), reactive power (Q), power factor (PF), phase angle (φ), frequency (f), and three-phase imbalance. The integrated controller can use a dual-core architecture of DSP+ARM, where the DSP excels in high-speed numerical computation for real-time calculation of electrical parameters and control algorithms, while the ARM handles system management, communication, and human-machine interaction.

[0059] S20: Based on the digital signal and the power quality index parameters, voltage over-limit judgment, three-phase imbalance judgment, and reactive power / power factor judgment are performed. Priority ranking rules for the governance strategy are set, all event identifiers are described in real time, and voltage over-limit processing, imbalance processing, and reactive power / power factor processing are performed sequentially from high to low priority. The optimal control command is calculated under the premise of satisfying priority constraints, ensuring that actions do not conflict. If a high-priority event exists, low-priority control is suspended until the high-priority event is resolved or stabilized before proceeding to the next level. For events of the same priority (e.g., two phases simultaneously exceeding limits), they are sorted and processed according to severity (deviation).

[0060] For example, a rated voltage U_N (e.g., 220V) and an allowable voltage deviation range (e.g., +7%, -10%) are set. If any phase voltage U_x is lower than the lower limit U_low or higher than the upper limit U_high, a voltage over-limit event is triggered. An unbalance threshold ε_th (e.g., 15%) is set. If the voltage unbalance ε_u or current unbalance ε_i exceeds the threshold, an unbalance event is triggered. A lower power factor limit PF_th (e.g., 0.9) is set. If PF is lower than the threshold, a low power factor event is triggered.

[0061] This priority order is not a simple functional ranking, but the core of ensuring the safe and stable operation of the power grid and avoiding control logic conflicts. Its necessity and uniqueness are mainly reflected in the profound understanding of the control coupling effect under different operating conditions.

[0062] For example, if an "imbalance priority" strategy is adopted, in a scenario where phase A is heavily loaded, phases B and C are lightly loaded, and the voltage of phase A is at the acceptable lower limit, if the controller prioritizes the commutation operation, it may cause the voltage of phase B to drop below the lower limit instantaneously, triggering a more dangerous "voltage over-limit" event, which could then lead to control conflicts and system oscillations. A "voltage priority" strategy, on the other hand, first addresses the low voltage problem by using a voltage regulator or reactive power compensation to raise the overall voltage to a safe range before addressing the imbalance problem, thus avoiding cascading conflicts.

[0063] Similarly, if a "power factor priority" strategy is adopted, in scenarios where the power factor is low and the voltage at the end of the line is close to the lower limit, if the controller prioritizes switching capacitors for reactive power compensation, the voltage may momentarily exceed the upper limit, triggering a dangerous "voltage exceeding the upper limit" event. A "voltage priority" strategy, however, checks the voltage first. If the voltage is too high, it prohibits or restricts the activation of the reactive power compensation module, or even first reduces the voltage through a voltage regulator module, reserving sufficient voltage safety margin for reactive power compensation. Therefore, this prioritization is based on a deep understanding of the inherent physical coupling relationships between various power quality indicators, establishing a hierarchical decision-making framework of "safety-stability-economy" to ensure that solving low-priority problems does not come at the expense of high-priority indicators, thereby guaranteeing the robustness and safety of the entire collaborative control system. This governance method includes a sophisticated "conflict avoidance mechanism," which is not a simple "mutually exclusive" logic, but a comprehensive management strategy that includes state prediction and resource coordination.

[0064] This governance method is designed based on "state" rather than "event". When an execution unit (such as a voltage regulator) receives an action command, the integrated controller immediately updates the system status flag of that module from "idle" to "in action". At this time, the control logic of other modules will check this status flag before initiating a decision. If it is not "idle", the current calculation is skipped and the system waits for the next cycle. More importantly, there is "post-action state prediction and locking": after the voltage regulator completes the gear switching, its state does not immediately return to "idle", but enters a preset "stable observation period" (e.g., a delay T_VR plus several power frequency cycles). During this period, the integrated controller continuously collects voltage data to determine whether the power grid has stabilized from the transient process of switching. Only when the data from multiple consecutive sampling points show that the voltage has stabilized at the new level, does the integrated controller truly release the status flag back to "idle". This locking, which includes two stages, "in action" and "post-action observation", can effectively prevent other modules from making incorrect decisions based on unstable measurement data containing transient components. For example, it can prevent the commutation module from misjudging due to voltage fluctuations during voltage regulation.

[0065] For voltage exceeding limits: The integrated controller first calls the voltage regulation module to calculate the required adjustment level. If the voltage regulation capability is insufficient, it considers calling the reactive power compensation module for auxiliary voltage regulation. After voltage regulation, the integrated controller waits for a preset stabilization observation period (e.g., a delay T_VR plus several power frequency cycles), resamples, and confirms that the voltage has returned to normal.

[0066] To address three-phase imbalance, a commutation strategy is initiated. The integrated controller identifies the current phase and load size of each commutable branch through topology analysis, calculates the load to be transferred, and performs a commutation operation only once at a time to avoid oscillations caused by simultaneous operation of multiple switches. After commutation, the system waits for at least T_swap time (e.g., 5 minutes) to observe the effect. During the commutation process, the reactive power compensation module maintains its current state to avoid interference.

[0067] Regarding reactive power / power factor, after the voltage is qualified and the imbalance meets the standard, the current reactive power deficit Q_need is calculated, a command is sent to the TSC, and Q_set=Q_need is output (but must be limited within the TSC capacity). Several sets of capacitors are then connected for compensation, and capacitor switching is performed for compensation. The reactive power compensation module responds quickly, completing compensation in milliseconds, and does not affect the voltage (if the reactive power adjustment range is too large, it may affect the voltage, and voltage constraints must be considered in the command).

[0068] S30 inserts a predetermined delay after completing different processing actions, then re-collects grid status data, and judges whether the governance effect meets the standard and whether further intervention is needed according to the priority ranking rules, forming a dynamic closed-loop mode of monitoring -> analysis -> decision -> execution -> re-monitoring. If TSC has been used for voltage regulation, the reactive power already generated is deducted in advance when processing reactive power priority.

[0069] Delay, also known as timing delay, includes the aforementioned "stable observation period" delay, as well as strategic delays between tasks of different priorities. For example, when both voltage and imbalance exceed limits, the system prioritizes voltage regulation. After the voltage regulation is completed, the system does not immediately initiate imbalance mitigation but waits for a complete "stable observation period" to end. Because changes in voltage levels affect the current magnitude of each phase at the end of the line, waiting for the system to fully stabilize before performing accurate imbalance calculations and decisions improves the accuracy of commutation strategies.

[0070] Capacity coordination is an example of predictive and feedforward control. When a system needs to boost voltage through reactive power compensation, its integrated controller first calculates the required voltage boost and predicts the necessary compensation capacity using a simplified grid model. The integrated controller "virtually" marks this portion of the total reactive power compensation module (TSC) capacity as "dedicated to voltage support and cannot be redistributed." Later, when the system handles the low-priority task of power factor adjustment, it calculates the total compensation required to achieve the power factor target, but the final command must meet the constraint that the compensation amount cannot exceed the total capacity minus the capacity reserved for voltage support. In this way, the system can anticipate the demand for shared resources (TSC capacity) from high-priority tasks and make reservations accordingly, ensuring that meeting low-priority objectives does not compromise the achievement of high-priority objectives.

[0071] In short, this application is successful.

[0072] In some embodiments, in step S20, combined Figure 2 In response to voltage exceeding limits, voltage quality classification intervals and governance strategies are established. Based on the size of the voltage range, the voltage quality classification intervals include, in order, the emergency zone for exceeding the upper limit, the early warning zone for exceeding the upper limit, the excellent zone, the early warning zone for exceeding the lower limit, and the emergency zone for exceeding the lower limit.

[0073] For emergency zones exceeding the upper limit, the management strategy is as follows: immediately activate the voltage regulation module to reduce the voltage by switching the tap changer. If the voltage regulation capacity is insufficient, inductive reactive power absorption will be carried out in conjunction with it.

[0074] For areas exceeding the upper limit warning zone, the governance strategy is as follows: initiate preventive adjustment, prioritize the absorption of inductive reactive power through reactive power compensation, and if ineffective, fine-tune the voltage regulation module to perform voltage reduction operation;

[0075] For areas with excellent air quality, only monitoring and data recording are performed.

[0076] For areas exceeding the lower limit warning zone, the governance strategy is as follows: initiate preventive adjustment, prioritize the generation of capacitive reactive power through reactive power compensation, and if ineffective, fine-tune the voltage regulation module to perform voltage boosting operation;

[0077] For emergency zones exceeding the lower limit, the management strategy is as follows: immediately activate the voltage regulation module to perform voltage boosting operation by switching taps; if the voltage regulation capacity is insufficient, then perform capacitive reactive power compensation.

[0078] Example 1, Scene Setting - Voltage Over-Limit Correction:

[0079] Distribution Area Overview: This is a rural distribution area with a long power supply radius and large voltage fluctuations at the end. Installing an on-load tap changer (compensated tap changer) allows for voltage adjustment in series at the mid-section of the line, with a voltage adjustment range of ±10%, divided into 9 levels (each level approximately 2.5%).

[0080] Initial state (peak electricity consumption on a certain evening):

[0081] The monitoring point is located at the end of the line (user side):

[0082] Ua=198V, Ub=200V, Uc=199V (all are near the lower limit of 198V, but phase A is critical).

[0083] The three-phase current is basically balanced (approximately 150A).

[0084] Power factor 0.92 (pass), voltage imbalance 3% (pass);

[0085] However, the voltage of phase A, 198V, has already reached the lower limit threshold (198V) and is showing a downward trend (the load is still increasing).

[0086] Problem: The voltage is at a critical lower limit. If no intervention is taken, the user equipment will not be able to work properly. This is a first-priority event.

[0087] Governance actions:

[0088] Analysis and Judgment: The controller detected Ua = 198V ≤ U_low, triggering a voltage lower limit event. Since the voltage imbalance and power factor are both within acceptable limits, voltage is the priority issue to address.

[0089] Voltage regulation strategy calculation:

[0090] The target voltage is set at 215V (-2.3% of the rated voltage of 220V, with a margin), requiring a voltage increase of ΔU = 215 - 198 = 17V.

[0091] The voltage change per level of the voltage regulator depends on the installation location and line parameters. Assuming each level increases the voltage at the end of the line by approximately 6V, the required number of levels is n = round(17 / 6) ≈ 3 levels.

[0092] Assuming the current voltage regulator setting is 0 (intermediate setting), after increasing to setting 3, the terminal voltage is expected to increase by 18V, reaching 216V, which is safe.

[0093] Command issued: The controller sends a command to the voltage regulator to increase the voltage by 3 levels.

[0094] The voltage regulation module can use a compensated voltage regulator or a power electronic voltage stabilizer. It uses a digital PID controller to calculate the voltage regulation step size based on the voltage deviation, so as to slightly adjust the transformer output voltage or line voltage and stabilize the voltage near the target value.

[0095] In some embodiments, in step S20, combined Figure 3To address three-phase imbalance, a classification range and governance strategy for three-phase imbalance are established. Based on the degree of three-phase imbalance, the classification ranges for three-phase imbalance include, in order, a severe imbalance zone, a moderate imbalance zone, a qualified warning zone, and an excellent zone.

[0096] For the severely unbalanced area, the treatment strategy is as follows: immediately initiate the commutation operation, prioritize switching part of the load of the high current phase in each commutation branch to the light load phase, re-evaluate after each operation, if it is still in the severely unbalanced area and the commutation interval is met, continue commutation, and so on, until it is determined to enter the moderate unbalanced area after re-evaluation.

[0097] For the moderate imbalance zone, the governance strategy is as follows: based on the governance strategy for the severe imbalance zone, reduce the switching branches and extend the switching interval, and continue to perform the cycle of switching, evaluation, switching, and evaluation until the zone is re-evaluated and judged to have entered the qualified warning zone or the excellent zone.

[0098] For qualified early warning areas, only monitoring and trend recording are performed;

[0099] For areas with excellent air quality, monitoring is only conducted.

[0100] Example 2, Scenario Setting - Three-phase Imbalance Management:

[0101] Overview of the distribution area: A residential distribution transformer with a rated capacity of 400kVA and an output voltage of 400V (three-phase four-wire system) supplies power to multiple residential buildings.

[0102] Initial state (voltage is qualified after voltage priority adjustment):

[0103] Three-phase voltage: Ua=222V, Ub=220V, Uc=221V (all within 198~235.4V).

[0104] Three-phase current: Ia=380A, Ib=190A, Ic=130A (total load current 700A);

[0105] The calculated current imbalance is: є_i=(I_max-I_min) / I_avg=(380-130) / 233.3=107%, which far exceeds the 15% threshold.

[0106] Voltage imbalance: є_u = 0.9%, acceptable.

[0107] Power factor: 0.95 (compensated), qualified.

[0108] Problem: The three-phase current is severely unbalanced, causing the transformer neutral point to shift, the neutral line to overload, and localized overheating of the transformer. This needs to be addressed immediately.

[0109] Governance actions:

[0110] Analysis and judgment: The core controller detected that the voltage and power factor were qualified, but the current imbalance exceeded the standard, triggering the second priority (three-phase imbalance) treatment.

[0111] Commutation strategy calculation:

[0112] The controller identifies the current phase and load of each commutable branch through topology recognition. Assuming there are 12 single-phase branches (each with a current of approximately 30A), the current distribution is: 6 phases A (180A), 4 phases B (120A), and 2 phases C (60A). Adding other fixed three-phase loads (phase A 200A, phase B 70A, phase C 70A), the total current is 380A, 190A, and 130A respectively.

[0113] Objective: To make the three-phase current as balanced as possible, with an ideal average current of I_avg = 700 / 3 = 233.3A.

[0114] The current phase A is overloaded by 146.7A, and some phase A branches need to be switched to phase B or C. Phase B is short of 43.3A, and phase C is short of 103.3A. Switching should be prioritized to phase C, which has the larger shortfall.

[0115] In the switchable branch system, phase A has 6 branches (each 30A). If 3 phase A branches (total 90A) are switched to phase C, the new currents are: phase A: 380-90=290A; phase B: 190A (unchanged); phase C: 130+90=220A. The new average current is 233.3A, and the imbalance є_i=(290-190) / 233.3=42.8%, which still exceeds the limit.

[0116] If the four A-phase branches (120A) are switched to the C-phase, then: A-phase: 380-120=260A; B-phase: 190A; C-phase: 130+120=250A; the imbalance є_i=(260-190) / 233.3=30%, which is still above the standard but has improved.

[0117] If the five A-phase branches are disconnected, then phase A will only have a fixed load of 200A + 30A from the phase changer, phase B will have 190A, and phase C will become 130 + 150 = 280A. The imbalance will be (280 - 190) / 233.3 = 38.6%, and phase A will change from overload to normal, but phase C will remain overloaded. Comprehensive optimization is required.

[0118] Considering the branch switching limit, a maximum of 4 branches can be switched in one action. Decision: First, switch 3 branches from phase A to phase C, and switch 2 branches from phase A to phase B (so that both B and C are replenished). Calculation: Phase A: 380 - (3 × 30 + 2 × 30) = 380 - 150 = 230A; Phase B: 190 + 2 × 30 = 250A; Phase C: 130 + 3 × 30 = 220A;

[0119] New current distribution: Phase A 230A, Phase B 250A, Phase C 220A, average 233.3A, unbalance є_i=(250-220) / 233.3=12.9%, reduced to below 15%, qualified!

[0120] Command issued: The controller sends a switching command to the selected 5 phase switching switches (3 original A phases now switched to C phases, and 2 original A phases now switched to B phases).

[0121] In some embodiments, in step S20, the phase switching operation is allocated based on the optimal load of a greedy / genetic algorithm, wherein the greedy algorithm switches the branch that contributes the most to reducing the imbalance at each iteration until it can no longer improve or the number of actions is limited, and the genetic algorithm obtains the optimal phase combination by encoding, selection, crossover and mutation in sequence.

[0122] The commutation module can be composed of high-speed magnetic latching relays or thyristors. By switching the power supply phase line where a single-phase load is located, it optimizes load distribution from the source. Its dynamic optimal load distribution strategy aims to minimize the three-phase current imbalance and employs specific methods such as greedy algorithms or genetic algorithms to achieve this. For example, in a scenario with an initial current distribution of (380, 190, 130) A, the algorithm simulates switching multiple branch loads of phase A (e.g., 30 A per branch) to phase B or C, evaluates the imbalance of various combinations, and finally selects the scheme that minimizes the imbalance without generating new overloads (e.g., switching 2 branches from A to B and 3 branches from A to C, making the current distribution (230, 250, 220) A, reducing the imbalance to approximately 12.9%). The control parameters of this module can be further optimized. For example, setting the imbalance threshold to 15% is an optimization result after a technical trade-off between "improvement effect" and "equipment life / grid stability". If the threshold is set too low (e.g., below 10%), the commutation switches will operate frequently under normal load fluctuations, drastically shortening equipment lifespan and causing minor disturbances to the power grid. If the threshold is set too high (e.g., above 20%), the power grid system may "ignore" more severe imbalances, causing transformers to operate in an overheated and inefficient state for extended periods. Therefore, the 15% value was found as an "optimal balance point" after long-term load data monitoring and simulation analysis of multiple typical distribution areas. The minimum commutation interval is set at 5 minutes, striking a balance between "real-time management" and "reliability of switching equipment." Excessively frequent operation can easily cause contact overheating, arc wear, and other problems, severely affecting its reliability and lifespan. The 5-minute interval was determined after comprehensively considering the performance specifications of mainstream switching components and allowing sufficient safety margins. Furthermore, most load changes have a certain degree of continuity; setting a 5-minute "cooling-off period" is to confirm that an imbalance event is "trend-driven" rather than "impulse-driven," thus avoiding an overreaction of the system to brief disturbances.

[0123] In some embodiments, for a qualified warning zone, if the recorded data remains within the qualified warning zone for a predetermined duration, a preventative commutation operation is performed during low-load periods. After each operation, a reassessment is conducted. If the zone remains within the qualified warning zone and the commutation interval is met, commutation continues, and so on, until a reassessment determines that the zone has entered the excellent zone.

[0124] In some embodiments, in step S20, combined Figure 4 For reactive power / power factor, a power factor classification range and governance strategy are established. According to the magnitude of the power factor, the power factor classification range includes, in order, a severely under-compensated area, an under-compensated governance area, a qualified economic area, an excellent area, and an over-compensated area.

[0125] For areas with severe under-compensation, the remediation strategy is to immediately activate the reactive power compensation module, add capacitors according to the calculated amount, compensate to the target value in one go, and reassess after compensation;

[0126] For areas with insufficient power factor, the management strategy is as follows: activate the reactive power compensation module and gradually add the predetermined capacitors until the power factor reaches the qualified economic zone.

[0127] For qualified economic zones, the governance strategy is as follows: monitor the load; if the load is stable and there is no reactive power to adjust, fine-tune the power factor to approach the excellent zone; if frequent switching is required, maintain the status quo.

[0128] For areas with excellent air quality, only data is monitored and recorded;

[0129] For the overcompensation zone, the mitigation strategy is to immediately disconnect a predetermined number of capacitors to bring the power factor back to the lag zone.

[0130] Example 3, Scenario Setting - Power Factor Improvement:

[0131] Distribution area overview: Capacity 400kVA, most of the load is inductive (motor). Equipped with a thyristor switched capacitor (TSC) device, with a total compensation capacity of 120kVar, divided into 12 groups (10kVar each), which can be quickly switched.

[0132] Initial state (after voltage and imbalance correction):

[0133] Three-phase voltage: Uab=395V, Ubc=398V, Uca=397V (line voltage, corresponding to a phase voltage of approximately 230V, which is acceptable).

[0134] Three-phase current: Ia=220A, Ib=210A, Ic=215A (basically balanced, unbalance <5%).

[0135] The total active power P = 150kW, the total reactive power Q = 110kVar (inductive), and the power factor PF = 150 / √(150² + 100²) ≈ 0.81. The voltages are all within the acceptable range, and the imbalance meets the standard, but the power factor is far below 0.9 and needs to be compensated.

[0136] Problem: Low power factor leads to high line losses and may result in penalties from the power company for adjusting power consumption.

[0137] Governance actions:

[0138] Analysis and judgment: The controller detected that the voltage was qualified and the three phases were balanced, but the power factor was 0.81 < 0.9, triggering the third priority (reactive power) management.

[0139] Compensation amount calculation:

[0140] The target power factor is set to 0.95, corresponding to cosφ2=0.95 and tanφ2=0.3287.

[0141] The current power factor angle φ1 = arccos0.81 ≈ 35.9°, tanφ1 ≈ 0.723.

[0142] The reactive power to be compensated is Q_c = P * (tanφ1 - tanφ2) = 150 * (0.723 - 0.3287) = 59.3.

[0143] Each TSC group is 10kVar, so the number of groups to be invested is n=59.3 / 10=5.93, which is rounded up to 6 groups (60kVar). This is slightly more than the required number, but it can avoid frequent investment switching.

[0144] Command issued: The controller sends a command to the TSC device, requesting that capacitors in groups 1-6 be put into operation.

[0145] The reactive power compensation module can use thyristor switched capacitor (TSC) devices or magnetically controlled reactor (MCR) devices. Based on reactive power deviation and cyclic switching strategies, it can achieve graded and smooth reactive power compensation to avoid frequent switching and circulating current, and can significantly improve the power factor and stabilize the system voltage.

[0146] In some embodiments, in step S20, a queue-style cyclic switching is performed based on the reactive power deviation, and the capacitor bank is dynamically switched according to the reactive power deficit to make the power factor reach the target value, while avoiding frequent switching and circulating current.

[0147] The second aspect of this application provides a multi-element power quality management device for distribution networks based on time-series coordinated control, used to implement the management method described above, wherein the management device includes a sensing layer, a control layer and an execution layer.

[0148] The sensing layer is equipped with a sensing unit, a signal processing unit, and a monitoring unit. The sensing unit is used to isolate and measure the three-phase voltage and current at the outlet of the distribution transformer and / or specific nodes of the line to obtain the original analog signal. The signal processing unit is used to standardize the original analog signal and then convert it into a digital signal for calculation by the integrated controller. The monitoring unit is used to calculate in real time to obtain the power quality index parameters of each phase and the power grid system.

[0149] The control layer is equipped with an integrated controller. This controller performs voltage over-limit judgment, three-phase imbalance judgment, and reactive power / power factor judgment based on the digital signals and power quality index parameters. It also sets priority ranking rules for governance strategies and describes all event identifiers in real time. The control layer can evaluate the effectiveness of each governance effort through preset classification intervals. For example, when all indicators enter the excellent or qualified zone and there is no warning trend, governance for that indicator is stopped and switched to monitoring; if the indicator drops from the severe zone to the moderate zone but does not enter the qualified zone, governance continues (subject to action interval limits); if the indicator does not change or even worsens after governance, fault diagnosis is triggered and an alarm is issued. This graded interval-based evaluation mechanism enables refined adaptive control, ensuring grid safety while minimizing unnecessary actions and extending equipment life.

[0150] The execution layer performs governance actions based on the judgment and priority ranking rules of the governance strategy of the control layer. For example, the voltage regulation module adjusts the voltage regulator level, the phase switching module switches the phase of the single-phase load, and the reactive power compensation module switches the capacitor.

[0151] After the execution layer's governance actions are applied to the distribution network, the perception layer immediately collects new grid status data and feeds it back to the control layer. Based on this data, the control layer evaluates the governance effectiveness, determining whether standards are met and whether further intervention is necessary. This hierarchical evaluation mechanism enables refined adaptive control, minimizes unnecessary actions, extends equipment lifespan, and achieves closed-loop feedback and evaluation.

[0152] The above description of this scheme presents an advanced, time-series coordinated control-based multi-element power quality management method and device for distribution networks, which is operating stably in a low-voltage distribution substation. Its aim is to address common problems within the substation, such as voltage deviation, three-phase imbalance, and insufficient reactive power, by coordinating control functions such as voltage regulation, reactive power compensation, and load commutation. One of its core mechanisms is "time-series priority coordination control," which includes a sophisticated "interlocking" mechanism to ensure system stability when different execution units operate. Specifically, when the voltage regulator module receives an instruction and begins adjusting the tap changer, the central controller immediately updates the voltage regulator module's operating status from "idle" to "operating." During this period, other control modules, such as the commutation module responsible for three-phase imbalance management, will first check the voltage regulator module's status before initiating their own decision calculations. If the voltage regulator module is found to be in an "operating" state, the commutation module's decision calculation for this round will be strategically skipped to wait for the voltage regulation action to complete and the grid to stabilize. Furthermore, after the voltage regulator completes the gear switching, its status indicator does not immediately return to "idle." Instead, it enters a preset "stable observation period," which typically includes a fixed delay period and several power frequency cycles. During this observation period, the controller continuously collects high-frequency voltage data from the power grid and performs detailed analysis to determine whether the power grid has fully recovered from the transient changes caused by the voltage regulation action and reached a new stable state. Only when data from multiple consecutive sampling points clearly show that the voltage has stabilized at the new level will the controller finally release the voltage regulator module's status indicator, returning it to the "idle" state, thus allowing other modules to continue executing their control logic. The purpose of this mechanism is to effectively prevent other control modules from making erroneous decisions based on measurement data containing transient components when the power grid is in an unstable or transitional state. This ensures that the power grid has reached a predictable stable state before any subsequent operations are performed, avoiding control conflicts and system oscillations.

[0153] However, after the system had been in operation for several years, some subtle changes began to accumulate. First, the anti-aliasing filter in the system's internal signal conditioning circuit, particularly its key passive components such as certain capacitors or inductors, experienced slight aging of their material properties due to long-term exposure to periodic changes in ambient temperature and continuous electrical stress. This aging caused a slight shift in the filter's frequency response characteristics, specifically a slight decrease in its attenuation capability for certain high-frequency components. This performance drift was not a sudden fault and therefore did not trigger the system's conventional fault alarm threshold. It was also difficult to detect directly during routine maintenance and inspection; it was merely a manifestation of the system's "unhealthy" state.

[0154] Meanwhile, the external power grid environment of the distribution substation is also quietly changing. In recent years, with the widespread adoption of electric vehicle charging stations, variable frequency air conditioners, and other nonlinear loads using switching power supplies among residential users, the background levels of high-frequency harmonics and switching noise in the distribution substation power grid have shown a consistent upward trend compared to the initial system design. The frequencies of these newly added noise components overlap with the frequency bands where the attenuation capability of the aforementioned aging filters decreases. This means that filters originally designed to suppress high-frequency interference, while experiencing a slight decline in their own performance, are now facing stronger noise input in specific frequency bands, further weakening their suppression effect on these specific high-frequency noises.

[0155] The combined effect of these two factors results in the analog voltage and current signals, after being processed by the signal conditioning circuit, containing significantly more high-frequency noise components than anticipated during system design when they enter the analog-to-digital converter (ADC). While this noise is insufficient to cause drastic fluctuations in voltage or current on a macroscopic level, it continuously and randomly superimposes on the effective signal at a microscopic level, leading to more "glitch" and uncertainty in the original digital sampled data.

[0156] The digital filtering logic in the integrated controller used to calculate the RMS voltage was initially optimized for sudden grid interference (such as lightning strikes and short circuits) and power frequency harmonics (such as the third and fifth harmonics). However, its suppression capability is limited for long-term, non-sudden, high-frequency noise caused by both filter performance drift and increased background noise. This means that even after digital filtering, the calculated RMS voltage will still exhibit more frequent and subtle fluctuations at the microscopic level than the actual grid voltage. These fluctuations are not actual voltage changes, but rather manifestations of noise in the calculation results, making the voltage reading appear "unsmooth" in the short term.

[0157] After the voltage regulator module completes a tap changer switch according to the instruction, the power grid system immediately enters the preset "stable observation period". At this time, the integrated controller needs to determine whether the power grid has stabilized from the transient process of the switching action based on the continuously collected voltage data. However, due to the micro-fluctuations in the above-mentioned voltage RMS value calculation results, and the fact that the design of the number of continuous sampling points for power grid stability determination did not fully consider this long-term noise accumulation effect, the controller may misjudge these minor fluctuations caused by noise as the system not being fully stable during the judgment process. For example, if the logic of stability determination requires that the voltage fluctuation be less than a certain minimum threshold for 10 consecutive sampling cycles, then the continuous small fluctuations caused by noise can easily make this condition difficult to meet, thus causing the voltage regulator module's operating status indicator to fail to be released from "in operation" back to "idle" in a timely manner. As a result, the actual duration of the "stable observation period" is unnecessarily extended, sometimes even several times longer than normal.

[0158] The prolonged locking of the voltage regulator module's operating status directly impacts other, lower-priority but equally important governance functions. For example, the commutation module, responsible for three-phase imbalance governance, is designed to skip decision calculations when the voltage regulator module is in an "operating" state. Therefore, during the extended "stable observation period" of the voltage regulator module, the commutation module is forcibly delayed and unable to initiate its load transfer operation. Under certain specific conditions, such as during the extended observation period, if a large single-phase load (e.g., a high-power agricultural irrigation pump or multiple residential users simultaneously starting high-power appliances) suddenly starts or stops, the three-phase current imbalance rapidly worsens and exceeds the commutation threshold. In this case, because the commutation module is forcibly delayed, it cannot perform load transfer operations in a timely manner, causing the power grid to operate under severe three-phase imbalance conditions for longer than expected. This prolonged unbalanced operation not only increases the risk of local overheating of distribution transformers and neutral line overload, but also easily causes the voltage of other phases to deviate further from the qualified range, exacerbating power quality problems. It may even trigger higher-level voltage over-limit alarms, forming a chain reaction. This makes the interlocking mechanism, which was originally intended to avoid conflicts, become a cause of delayed response and worsening of problems in the power grid system under certain cumulative effects.

[0159] In some embodiments, the governance method further includes step S40, which abandons the traditional grid stability determination method based on fixed thresholds and fixed durations, and instead adopts a more intelligent and flexible adjustment strategy. It determines whether the grid has truly recovered from the transient process caused by voltage regulation and reached a new equilibrium by analyzing the short-term average change trend and fluctuation characteristics of the effective voltage value in real time. This method, like an experienced expert, can accurately distinguish between real grid transient fluctuations and micro-fluctuations caused by noise in the complex environment of current distribution networks where filter performance drift and background noise are constantly increasing. This ensures that the operating status indicator of the voltage regulator module can be released in a timely and accurate manner, avoiding system response delays and power quality deterioration caused by misjudgment.

[0160] This solution aims to address the following issues in a comprehensive power quality management system for distribution networks: Slight performance deviations occur in the anti-aliasing filters of the signal conditioning circuit after long-term operation; and the widespread use of nonlinear loads such as electric vehicle charging stations and variable frequency air conditioners in distribution substations leads to a normalized increase in high-frequency harmonics and switching noise background levels. This results in higher-than-expected noise levels in the analog-to-digital converter input signal, causing micro-fluctuations in the calculated voltage RMS value in the integrated controller. These micro-fluctuations cause the voltage regulator module to misjudge the grid's stable state during the stable observation period, resulting in its operating status being unnecessarily locked for extended periods. Ultimately, this delays the commutation module's response to three-phase imbalance problems and exacerbates the deterioration of grid power quality.

[0161] Specifically, after the voltage regulating module completes the tap changer switching action, the integrated controller no longer relies solely on whether the effective voltage value fluctuates within a fixed small range or waits for a preset fixed time to determine whether the power grid is stable. Instead, it continuously collects and analyzes the effective voltage value data.

[0162] First, short-term average values ​​are calculated and changes are assessed. The integrated controller maintains a sliding data window, for example, containing the effective voltage values ​​calculated over the most recent N power frequency cycles (e.g., N = 5 to 10 cycles). The short-term average value is calculated based on the effective voltage value data within the window, using the following formula: ;

[0163] in, This represents the effective voltage value calculated in the i-th power frequency cycle before the current time k, where N is the length of the sliding window;

[0164] Subsequently, the integrated controller continuously tracks the changes in the short-term average value and calculates the difference between the current short-term average value and the previous short-term average value, i.e., the rate of change Delta_V_avg(k), Delta_V_avg(k) = |V_avg(k) - V_avg(k-1)|. If this rate of change Delta_V_avg(k) remains below a preset minimum threshold Epsilon_avg (e.g., 0.05% of the rated voltage) for multiple consecutive calculation cycles, it indicates that the voltage no longer has a significant upward or downward trend and is approaching a stable value. The setting of this threshold Epsilon_avg needs to take into account the normally increasing background noise in the power grid, ensuring that it can tolerate minor fluctuations caused by noise while still identifying the true voltage trend changes. Simultaneously, the integrated controller also calculates the degree of fluctuation of the effective voltage value within the same sliding data window. Here, standard deviation can be used to quantify the dispersion of the data, effectively reflecting the distribution between data points and the average value, thus demonstrating the "smoothness" of the voltage reading. The formula for the degree of fluctuation Sigma(k) is: If this fluctuation level Sigma(k) remains at a very low level, and this low level is consistent with the minor fluctuation level caused by filter performance drift and background noise superposition under normal, undisturbed grid conditions, then it indicates that the drastic changes caused by voltage regulation in the grid have subsided, and what remains are only minor, normalized disturbances in the environment. This "very low level" is defined by a flexibly adjustable threshold Epsilon_sigma, which is adjusted according to the statistical characteristics of the current background noise in the grid to avoid misjudging noise as instability.

[0165] Finally, convergence and stability conditions are determined. If condition 1: the rate of change of the short-term average value of the effective voltage is consistently lower than the first preset threshold (Delta_V_avg(k) < Epsilon_avg), and condition 2: the fluctuation of the effective voltage is consistently lower than the second preset threshold (Sigma(k) < Epsilon_sigma), and these two conditions are met for a predetermined number of sampling periods (i.e., duration T_stable), then the integrated controller determines that the power grid has stabilized and immediately updates the operating status of the voltage regulation module from "in operation" to "idle". This T_stable is no longer a fixed value, but is flexibly adjusted according to the actual recovery characteristics of the power grid and the current background noise level. For example, if the system detects a high current background noise level (which is consistent with the scenario of filter performance drift and increased nonlinear load), T_stable will be appropriately extended to ensure reliable judgment can be made even in noisy environments; conversely, if the power grid recovers rapidly and the noise level is low, T_stable can be shortened to accelerate the response speed. This flexible adjustment mechanism can effectively address the micro-fluctuations in the effective voltage value caused by filter performance drift and increased background noise, avoiding misjudging these fluctuations as system instability.

[0166] Once the integrated controller determines that the power grid is stable based on the above logic, it immediately updates the voltage regulator module's operating status from "active" to "idle." This allows other control modules, such as the commutation module responsible for three-phase imbalance mitigation, to promptly check the voltage regulator module's idle status and initiate their own decision calculations and load transfer operations. This directly solves the problem of the voltage regulator module being locked for an extended period due to misjudgment, leading to delayed response from the commutation module, which in turn exacerbates three-phase imbalance and can even trigger a chain reaction. In this way, the system can respond to power grid changes more intelligently and promptly, improving the overall efficiency and reliability of power quality management.

[0167] In other words, the integrated controller performs in-depth analysis from two aspects simultaneously: observing the "major trend" of voltage and quantifying the "minor fluctuations." Specifically, it calculates the dispersion of the effective voltage value within the same time period—the range of data points around the average value. If this fluctuation remains at a very low level, and this low level matches the level of minor jitter that would normally exist in the current power grid environment due to slight degradation in filter performance and increased background noise, then it indicates that the drastic changes caused by voltage regulation have subsided, leaving only minor, normalized environmental disturbances. This flexible adjustment limit and observation time are designed to adapt to the actual situation of filter performance drift and increased background noise, avoiding misjudging micro-fluctuations caused by noise as system instability. Once the power grid is determined to be stable, the integrated controller immediately releases the operating status flag of the voltage regulator module. This allows the commutation module responsible for three-phase imbalance mitigation to start working promptly, avoiding delays caused by the voltage regulator module being locked for an extended period. This effectively prevents the three-phase imbalance problem from worsening during the waiting period, improving the overall system's response speed and mitigation effectiveness in addressing power quality issues.

[0168] Conventional stability determination methods typically employ fixed voltage range thresholds and fixed observation times. This approach performs well in scenarios with relatively clean power grid environments and low noise levels. However, in current distribution substation environments where filter performance has degraded and background noise has consistently increased, using a fixed, overly strict voltage fluctuation threshold can lead to frequent triggering of the threshold even after the power grid has recovered from voltage regulation. This results in the system misjudging instability and unnecessarily extending the lockout time of the voltage regulator module. Conversely, relaxing the threshold may prevent the timely detection of genuine power grid instability.

[0169] Therefore, step S40 completely changes the way the system understands and judges the "stable" state of the power grid, transforming it from the past static "black and white" inspection into a more intelligent and flexible "process assessment".

[0170] This shift from "static point inspection" to "flexible process assessment" enables the system to maintain a deeper understanding of the actual operating status of the power grid, even in the face of long-term accumulated filter performance drift and normally increasing background noise. It avoids decision-making delays caused by information distortion, ensures the timely release of voltage regulator module status indicators, and allows the commutation module to intervene promptly, effectively mitigating three-phase imbalance. This deeper understanding and judgment mechanism of "stability" is an innovative response to the complex noise environment of the current distribution network, significantly improving the system's intelligence and reliability in actual operation.

[0171] Therefore, this solution can significantly improve the accuracy and timeliness of stability judgment in the comprehensive power quality management system of the distribution network under complex noise environments. It effectively avoids misjudging the grid stability state due to micro-fluctuations in the voltage regulator module's RMS voltage calculation, thus ensuring that its operating status indicator is released in a timely manner. This avoids unnecessary long-term delays in other management functions such as the commutation module, ultimately effectively alleviating power quality problems such as three-phase imbalance and improving the overall system's operating efficiency and reliability.

[0172] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the invention. The advantages of the present invention have been fully and effectively realized. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments; any variations or modifications can be made to the implementation of the present invention without departing from these principles.

Claims

1. A multi-element power quality management method for distribution networks based on time-series coordinated control, characterized in that, Includes the following steps: S10 performs isolated measurements of the three-phase voltage and current at the outlet of the distribution transformer and / or specific nodes to obtain the original analog signal. The original analog signal is then standardized and converted into a digital signal for calculation by the integrated controller, thereby acquiring the power quality index parameters of each phase and the power grid system in real time. S20, based on the digital signal and the power quality index parameters, voltage over-limit judgment, three-phase imbalance judgment and reactive power / power factor judgment are performed, and priority sorting rules for governance strategies are set. All event identifiers are described in real time, and voltage over-limit processing, imbalance processing and reactive power / power factor processing are performed in order of priority from high to low. Under the premise of satisfying priority constraints, the optimal control command is calculated and the actions are ensured to be non-conflicting. To address three-phase imbalance, a commutation strategy is initiated. The integrated controller uses topology identification to determine the current phase and load size of each commutable branch, calculates the load to be transferred, and performs a commutation operation, executing only one commutation operation at a time. Regarding reactive power / power factor, after the voltage is qualified and the imbalance meets the standard, the current reactive power deficit Q_need is calculated, and a command is sent to the TSC to connect several sets of capacitors for compensation. S30 inserts a predetermined delay after completing different processing actions, then re-collects power grid status data, and judges whether the governance effect meets the standard and whether further intervention is needed according to the priority ranking rules, forming a dynamic closed-loop mode of monitoring -> analysis -> decision -> execution -> re-monitoring.

2. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 1, characterized in that, In step S10, the power quality index parameters include the effective value of voltage, the effective value of current, active power, reactive power, power factor, phase angle, frequency, and three-phase imbalance.

3. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 1, characterized in that, In step S20, for voltage exceeding the limit, voltage quality classification intervals and management strategies are established. According to the size of the voltage range, the voltage quality classification intervals include, in order, the upper limit emergency zone, the upper limit warning zone, the good zone, the lower limit warning zone, and the lower limit emergency zone. For emergency zones exceeding the upper limit, the management strategy is as follows: immediately activate the voltage regulation module to reduce the voltage by switching the tap changer. If the voltage regulation capacity is insufficient, inductive reactive power absorption will be carried out in conjunction with it. For areas exceeding the upper limit warning zone, the governance strategy is as follows: initiate preventive adjustment, prioritize the absorption of inductive reactive power through reactive power compensation, and if ineffective, fine-tune the voltage regulation module to perform voltage reduction operation; For areas with excellent air quality, only monitoring and data recording are performed. For areas exceeding the lower limit warning zone, the governance strategy is as follows: initiate preventive adjustment, prioritize the generation of capacitive reactive power through reactive power compensation, and if ineffective, fine-tune the voltage regulation module to perform voltage boosting operation; For emergency zones exceeding the lower limit, the management strategy is as follows: immediately activate the voltage regulation module to perform voltage boosting operation by switching taps; if the voltage regulation capacity is insufficient, then perform capacitive reactive power compensation.

4. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 3, characterized in that, In step S20, for three-phase imbalance, a classification interval and treatment strategy for three-phase imbalance are established. According to the degree of three-phase imbalance, the classification intervals for three-phase imbalance include severe imbalance zone, moderate imbalance zone, qualified warning zone and excellent zone in sequence. For the severely unbalanced area, the treatment strategy is as follows: immediately initiate the commutation operation, prioritize switching part of the load of the high current phase in each commutation branch to the light load phase, re-evaluate after each operation, if it is still in the severely unbalanced area and the commutation interval is met, continue commutation, and so on, until it is determined to enter the moderate unbalanced area after re-evaluation. For the moderate imbalance zone, the governance strategy is as follows: based on the governance strategy for the severe imbalance zone, reduce the switching branches and extend the switching interval, and continue to perform the cycle of switching, evaluation, switching, and evaluation until the zone is re-evaluated and judged to have entered the qualified warning zone or the excellent zone. For qualified early warning areas, only monitoring and trend recording are performed; For areas with excellent air quality, monitoring is only conducted.

5. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 4, characterized in that, In step S20, the phase switching operation is allocated based on the optimal load of the greedy / genetic algorithm. In each iteration, the greedy algorithm switches the branch that contributes the most to reducing the imbalance until it can no longer be improved or the number of actions is limited. The genetic algorithm solves the optimal phase combination by encoding, selection, crossover and mutation in sequence.

6. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 4, characterized in that, For qualified warning zones, if the recorded data remains within the qualified warning zone for a predetermined duration, a preventative commutation operation will be performed during low-load periods. After each operation, a reassessment will be conducted. If the zone remains qualified and the commutation interval is met, commutation will continue, and so on, until a reassessment determines that the zone has entered the excellent zone.

7. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 4, characterized in that, In step S20, for reactive power / power factor, a power factor classification interval and a management strategy are established. According to the magnitude of the power factor, the power factor classification interval includes, in order, a severely under-compensated area, an under-compensated management area, a qualified economic area, an excellent area, and an over-compensated area. For areas with severe under-compensation, the remediation strategy is to immediately activate the reactive power compensation module, add capacitors according to the calculated amount, compensate to the target value in one go, and reassess after compensation; For areas with insufficient power factor, the management strategy is as follows: activate the reactive power compensation module and gradually add the predetermined capacitors until the power factor reaches the qualified economic zone. For qualified economic zones, the governance strategy is as follows: monitor the load; if the load is stable and there is no reactive power to adjust, fine-tune the power factor to approach the excellent zone; if frequent switching is required, maintain the status quo. For areas with excellent air quality, only data is monitored and recorded; For the overcompensation zone, the mitigation strategy is to immediately disconnect a predetermined number of capacitors to bring the power factor back to the lag zone.

8. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 7, characterized in that, In step S20, a queue-style cyclic switching is performed based on the reactive power deviation. The capacitor bank is dynamically switched according to the reactive power deficit to make the power factor reach the target value, while avoiding frequent switching and circulating current.

9. The method for multi-element power quality management of distribution networks based on time-series coordinated control as described in claim 7, characterized in that, It also includes step S40, which involves continuously collecting and analyzing the effective voltage value data after the voltage regulating module completes the tap changer switching action; First, short-term average values ​​are calculated and changes are assessed. The integrated controller maintains a sliding data window, and the short-term average value is calculated based on the effective voltage data within the window. The formula is as follows: ; in, This represents the effective voltage value calculated in the i-th power frequency cycle before the current time k, where N is the length of the sliding window; Subsequently, the integrated controller continuously tracks the changes in the short-term average value and calculates the difference between the current short-term average value and the previous short-term average value, i.e., the rate of change Delta_V_avg(k), where Delta_V_avg(k) = |V_avg(k) - V_avg(k-1)|. Simultaneously, the integrated controller calculates the fluctuation degree of the effective voltage value within the same sliding data window, with the fluctuation degree Sigma(k) calculated using the formula: ; Finally, convergence and stability conditions are determined. If condition 1: the short-term average change rate of the effective voltage value is continuously lower than the first preset threshold, i.e., Delta_V_avg(k) < Epsilon_avg, and condition 2: the fluctuation of the effective voltage value is continuously lower than the second preset threshold, i.e., Sigma(k) < Epsilon_sigma, and these two conditions are met for a predetermined number of sampling periods, then the integrated controller determines that the power grid has stabilized and immediately updates the operating status of the voltage regulating module from "in operation" to "idle".

10. A distribution network multi-element power quality management device based on time-series coordinated control, used to implement the management method as described in any one of claims 1 to 9, characterized in that, The treatment device includes: The sensing layer includes a sensing unit, a signal processing unit, and a monitoring unit. The sensing unit is used to perform isolated measurements of the three-phase voltage and current at the outlet of the distribution transformer and / or specific nodes of the line to obtain the original analog signal. The signal processing unit is used to standardize the original analog signal and then convert it into a digital signal for calculation by the integrated controller. The monitoring unit is used to calculate in real time to obtain the power quality index parameters of each phase and the power grid system. The control layer includes an integrated controller. The integrated controller performs voltage over-limit judgment, three-phase imbalance judgment, and reactive power / power factor judgment based on the digital signal and the power quality index parameters, and sets priority ranking rules for governance strategies, and describes all event identifiers in real time. The execution layer performs governance actions based on the judgments of the control layer and the priority ranking rules of the governance strategy.

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