Power supply end voltage monitoring and cooperative regulation method and system based on currentless sampling

Abstract

The application discloses a kind of based on currentless sampling area end voltage monitoring and collaborative control method and system, comprising: by parallelly arranged in low-voltage distribution area end voltage monitoring device, real-time acquisition area end three-phase voltage instantaneous signal;According to three-phase voltage instantaneous signal extraction fundamental voltage complex phasor;Fundamental voltage complex phasor is carried out symmetrical component transformation, obtains positive sequence voltage component and negative sequence voltage component;According to positive sequence voltage component and negative sequence voltage component, generate comprehensive state index;According to comprehensive state index, generate target compensation voltage complex phasor including positive sequence control amount and negative sequence compensation amount;According to target compensation voltage complex phasor, by parallelly connected control device that accesses area end, injects compensation current to area end.This application aims at solving prior art in dependence on current transformer leads to installation complex, there is power failure construction risk;Voltage, overvoltage and three-phase unbalance problem scattered management, lack unified processing framework;Voltage monitoring and control are independent of each other, cannot form collaborative closed loop and other problems, realize without dependence on current transformer installation, can unifiedly process various voltage problems, and make voltage monitoring and control form collaborative closed loop.

Description

Technical Field

[0001] This invention belongs to the field of power distribution network technology, specifically relating to a method and system for voltage monitoring and coordinated control at the end of a transformer substation based on current-free sampling. Background Technology

[0002] Low-voltage distribution transformer areas are a crucial link in the power system that directly faces end users, and their power supply quality directly impacts residents' lives and production operations. With the seasonal increase in rural load, the connection of charging piles, and the large-scale grid connection of distributed photovoltaic power, the frequency of voltage fluctuations at the end of the transformer area has increased significantly, and voltage issues are becoming more complex, placing higher demands on the real-time performance and control precision of voltage management.

[0003] Currently, the following methods are mainly used to manage voltage at the end of transformer substations: Line upgrades or capacity increases are traditional methods for solving voltage problems, such as replacing conductors with larger cross-section ones, increasing line corridors, or adding transformers to improve power supply capacity. However, this method involves high investment costs, long construction periods, and difficulty in adapting to dynamic load changes, often resulting in new voltage problems shortly after the upgrades are completed.

[0004] Another common approach is to install voltage regulation devices, such as automatic voltage regulators and reactive power compensation devices. These devices typically require current transformers installed on the line to collect load current information for generating control strategies. However, installing current transformers often involves power outages, and the installation location and wiring methods are limited by site conditions, making the project complex. Furthermore, some older transformer substations lack the necessary conditions for installing current transformers, further limiting the application scope of these devices.

[0005] Voltage monitoring devices are widely used in transformer substations for voltage quality detection and analysis. Existing portable or fixed voltage monitoring equipment possesses high-precision sampling and multi-condition simulation capabilities, accurately reflecting the voltage status at the end of the substation. However, these monitoring devices are mainly used for offline analysis or fault diagnosis; the voltage data they collect does not participate in real-time control decisions, resulting in a disconnect between monitoring and control functions.

[0006] In recent years, flexible control devices with parallel connection capabilities have emerged. These devices can be installed under power without modifying the wiring, making them highly applicable to engineering projects. However, the control logic of existing parallel control devices mainly focuses on voltage compensation itself, lacking a coordination mechanism with high-precision voltage monitoring equipment, making it difficult to dynamically optimize the control strategy based on changes in the terminal voltage state.

[0007] In summary, the existing technology has the following problems: relying on current transformers leads to complex installation and the risk of power outages during construction; undervoltage, overvoltage and three-phase imbalance problems are managed separately and lack a unified processing framework; voltage monitoring and control are independent of each other and cannot form a coordinated closed loop. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a method and system for voltage monitoring and coordinated control at the end of a transformer substation based on current-free sampling. The aim is to solve problems such as the complexity of installation and the risk of power outages due to reliance on current transformers; the fragmented management of undervoltage, overvoltage, and three-phase imbalance issues without a unified framework; and the independent operation of voltage monitoring and control, preventing the formation of a coordinated closed loop. This invention achieves a unified approach to various voltage issues without relying on current transformers, and enables voltage monitoring and control to form a coordinated closed loop.

[0009] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: According to a first aspect of the present invention, a method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling is provided, comprising: The instantaneous three-phase voltage signal at the end of the low-voltage distribution transformer area is collected in real time by a voltage monitoring device connected in parallel at the end of the transformer area. Extract the fundamental voltage complex phase quantity from the instantaneous three-phase voltage signal; The fundamental voltage complex phasor is subjected to symmetrical component transformation to obtain positive-sequence voltage components and negative-sequence voltage components; A comprehensive state index is generated based on the positive-sequence voltage component and the negative-sequence voltage component; Based on the comprehensive state index, a target compensation voltage complex quantity containing positive sequence control quantity and negative sequence compensation quantity is generated; Based on the target compensation voltage phase quantity, compensation current is injected into the end of the transformer area through a parallel control device connected in parallel to the end of the transformer area.

[0010] In one possible implementation of the first aspect, generating a comprehensive state index based on the positive-sequence voltage component and the negative-sequence voltage component includes: A positive-sequence voltage deviation is generated based on the positive-sequence voltage component and a preset reference voltage; Obtain the amplitude of the negative sequence voltage component; The comprehensive state index is generated by weighted summation based on the magnitudes of the positive-sequence voltage deviation and the negative-sequence voltage component.

[0011] In one possible implementation of the first aspect, after generating the comprehensive state index, the method further includes: The comprehensive status index is compared with the preset input threshold and the preset exit threshold, respectively; When the comprehensive status index is greater than the input threshold, it is determined to be an overvoltage-dominated state; When the comprehensive status index is less than the negative value of the input threshold, it is determined to be an undervoltage-dominated state. When the absolute value of the comprehensive status index is less than the exit threshold, the current control state is maintained.

[0012] In one possible implementation of the first aspect, generating the target compensation voltage complex quantity, which includes a positive-sequence control quantity and a negative-sequence compensation quantity, based on the comprehensive state index includes: Based on the deviation between the positive sequence voltage component and the preset reference voltage, a positive sequence control amplitude is generated through proportional-integral adjustment. The positive-sequence modulation amplitude is projected onto the phase direction of the positive-sequence voltage component to generate the complex phase quantity of the positive-sequence modulation quantity; The complex phase of the negative sequence voltage component is multiplied by a preset negative sequence suppression coefficient and then inverted to generate the complex phase of the negative sequence compensation. The complex phase quantity of the positive sequence control quantity is superimposed with the complex phase quantity of the negative sequence compensation quantity to generate the target compensation voltage complex phase quantity.

[0013] In one possible implementation of the first aspect, after injecting compensation current into the end of the transformer substation, the method further includes: The instantaneous three-phase voltage signals at the end of the transformer area are reacquired, and the updated positive-sequence voltage components and the updated negative-sequence voltage components are calculated based on the reacquired instantaneous three-phase voltage signals. When the updated positive-sequence voltage component fails to return to the preset reference range, or the amplitude of the updated negative-sequence voltage component fails to drop below the preset threshold, at least one of the following is corrected: the proportional-integral coefficient used to generate the positive-sequence control quantity, the negative-sequence suppression coefficient used to generate the negative-sequence compensation quantity, or the weighting coefficient used to generate the comprehensive state index.

[0014] According to a second aspect of the present invention, a system for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling is provided, comprising: A voltage monitoring device is installed in parallel at the end of the low-voltage distribution transformer area to collect the instantaneous three-phase voltage signal at the end of the transformer area in real time. A controller, connected to the voltage monitoring device, is configured to: Extract the fundamental voltage complex phase quantity from the instantaneous three-phase voltage signal; The fundamental voltage complex phasor is subjected to symmetrical component transformation to obtain positive-sequence voltage components and negative-sequence voltage components; A comprehensive state index is generated based on the positive-sequence voltage component and the negative-sequence voltage component; Based on the comprehensive state index, a target compensation voltage complex quantity containing positive sequence control quantity and negative sequence compensation quantity is generated; A parallel control device is connected to the controller and connected in parallel to the end of the transformer area, used to inject compensation current into the end of the transformer area according to the target compensation voltage phase quantity.

[0015] In one possible implementation of the second aspect, the controller is further configured to: A positive-sequence voltage deviation is generated based on the positive-sequence voltage component and a preset reference voltage; Obtain the amplitude of the negative sequence voltage component; The comprehensive state index is generated by weighted summation based on the magnitudes of the positive-sequence voltage deviation and the negative-sequence voltage component.

[0016] In one possible implementation of the second aspect, the controller is further configured to: The comprehensive status index is compared with the preset input threshold and the preset exit threshold, respectively; When the comprehensive status index is greater than the input threshold, it is determined to be an overvoltage-dominated state; When the comprehensive status index is less than the negative value of the input threshold, it is determined to be an undervoltage-dominated state. When the absolute value of the comprehensive status index is less than the exit threshold, the current control state is maintained.

[0017] In one possible implementation of the second aspect, the controller is further configured to: Based on the deviation between the positive sequence voltage component and the preset reference voltage, a positive sequence control amplitude is generated through proportional-integral adjustment. The positive-sequence modulation amplitude is projected onto the phase direction of the positive-sequence voltage component to generate the complex phase quantity of the positive-sequence modulation quantity; The complex phase of the negative sequence voltage component is multiplied by a preset negative sequence suppression coefficient and then inverted to generate the complex phase of the negative sequence compensation. The complex phase quantity of the positive sequence control quantity is superimposed with the complex phase quantity of the negative sequence compensation quantity to generate the target compensation voltage complex phase quantity.

[0018] In one possible implementation of the second aspect, the controller is further configured to: The instantaneous three-phase voltage signals at the end of the transformer area are reacquired, and the updated positive-sequence voltage components and the updated negative-sequence voltage components are calculated based on the reacquired instantaneous three-phase voltage signals. When the updated positive-sequence voltage component fails to return to the preset reference range, or the amplitude of the updated negative-sequence voltage component fails to drop below the preset threshold, at least one of the following is corrected: the proportional-integral coefficient used to generate the positive-sequence control quantity, the negative-sequence suppression coefficient used to generate the negative-sequence compensation quantity, or the weighting coefficient used to generate the comprehensive state index.

[0019] According to a third aspect of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the aforementioned method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling.

[0020] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program, which, when executed by a processor, implements the aforementioned method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling.

[0021] According to a fifth aspect of the present invention, a computer program product is provided, which, when executed by a processor, implements the aforementioned method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: This invention achieves voltage regulation without current sampling. Traditional voltage management devices for distribution transformers typically require the installation of current transformers on the lines to collect load current information for generating control strategies. The installation of current transformers often involves power outages, and the installation location and wiring methods are limited by site conditions, making implementation difficult in scenarios such as old urban areas or rural power grids. The method of this invention generates control decisions entirely based on voltage monitoring data, eliminating the need for external installation of current transformers or clamp-on current sensors on the distribution lines. The parallel control device can be connected to the end of the distribution transformer while energized, and can be put into operation directly while maintaining the original feeder structure and load connection method. The current-sampling-free design of this invention eliminates the need for power outages during the installation of the voltage management device, significantly reducing the difficulty of engineering implementation.

[0023] This invention achieves unified processing of various voltage problems. In existing technologies, undervoltage, overvoltage, and three-phase imbalance problems are often addressed separately using different methods, such as reactive power compensation for low voltage and phase switching for three-phase imbalance. This decentralized approach not only requires significant equipment investment but also lacks coordination between different control methods, leading to potential interference. This invention maps the three-phase voltage to the sequence component domain using symmetrical component transformation. The positive-sequence voltage component characterizes the overall supply voltage level, while the negative-sequence voltage component characterizes the degree of three-phase imbalance, unifying different types of voltage problems under a single analytical framework for quantitative description. Furthermore, through a control strategy that decouples positive and negative sequences, the positive-sequence control quantity and the negative-sequence compensation quantity are superimposed to generate a target compensation command, enabling parallel control devices to simultaneously perform voltage level regulation and imbalance suppression functions. This unified processing approach avoids functional overlap and mutual interference between various control devices, improving the overall effectiveness of voltage management.

[0024] This invention achieves a collaborative closed-loop monitoring and control system. While existing voltage monitoring devices possess high-precision sampling capabilities, the data they collect is primarily used for offline analysis or fault diagnosis, and does not participate in real-time control decisions. Furthermore, the control logic of control devices is relatively independent, lacking dynamic response capabilities to the voltage status at the distribution terminals. This invention directly uses voltage monitoring results to generate control decisions and re-collects voltage signals after control execution to verify the control effect. When the control effect does not meet expectations, the system adaptively corrects the proportional-integral coefficient, negative-sequence suppression coefficient, or weighting coefficient based on the changing trends of positive-sequence deviation and negative-sequence indicators. Through this closed-loop mechanism of monitoring-judgment-control-re-monitoring, the system can dynamically adjust control parameters according to load fluctuations and changes in distributed photovoltaic output, improving the stability of voltage operation at the distribution terminal. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a flowchart of a method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling, according to the present invention.

[0027] Figure 2 This is a schematic diagram showing the parallel connection of voltage monitoring devices in a voltage monitoring and coordinated control system at the end of a distribution area. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, this invention provides a method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling. This method achieves flexible regulation of the voltage at the end of the substation without the need to install current transformers. Specifically, it includes the following steps: S1. By using a voltage monitoring device connected in parallel at the end of the low-voltage distribution transformer area, the instantaneous three-phase voltage signal at the end of the transformer area is collected in real time.

[0030] Specifically, a voltage monitoring device is installed in parallel at the end of a low-voltage distribution substation to synchronously acquire the instantaneous voltage signals of phases A, B, and C, forming raw three-phase voltage data reflecting the operating status of the substation end. The voltage monitoring device can be fixedly installed or deployed portablely. Its function is to acquire the amplitude, phase, and fluctuation of the voltage at the substation end. In this invention, the voltage monitoring device is used to construct a voltage status observation system at the substation end. Its acquisition results directly participate in the positive and negative sequence component analysis and control decision-making process, thereby achieving integrated and coordinated monitoring and control.

[0031] S2. Extract the fundamental voltage complex phase quantity based on the instantaneous three-phase voltage signal.

[0032] In other words, after acquiring the instantaneous three-phase voltage signals, the fundamental voltage complex phasor is extracted from these signals. To ensure accurate and stable sequence component separation, state discrimination, and decoupling control calculations, the acquired three-phase voltage signals need to undergo fundamental characteristic construction processing to reduce the impact of factors such as DC bias, harmonic components, measurement noise, and asynchronous sampling on control decisions. Specifically, the fundamental phasor is extracted from each phase's instantaneous voltage signal within a sliding time window. A combination of DC bias removal and windowed sliding discrete Fourier transform is used to obtain the fundamental voltage complex phasor of the corresponding phase at time k. This method enables a comprehensive characterization of the voltage level, phase relationship, and imbalance characteristics at the transformer substation terminals without the need for current sampling.

[0033] S3. Perform symmetrical component transformation on the fundamental voltage complex to obtain the positive sequence voltage component and the negative sequence voltage component.

[0034] Specifically, after obtaining the three-phase fundamental voltage complex phasors, a symmetrical component transformation is performed on the fundamental voltage complex phasors to obtain positive-sequence and negative-sequence voltage components. By mapping the three-phase voltages from the phasor domain to the sequence component domain, different types of voltage problems can be quantitatively described within a unified analytical framework. The positive-sequence voltage component is used to characterize the overall power supply voltage level at the end of the distribution area and to determine whether there is undervoltage or overvoltage operation at the end of the distribution area; the negative-sequence voltage component is used to characterize the degree of three-phase voltage imbalance at the end of the distribution area and to determine whether there is three-phase unbalance operation at the end of the distribution area.

[0035] S4. Generate a comprehensive state index based on the positive-sequence voltage component and the negative-sequence voltage component. The comprehensive state index unifies different types of voltage problems under the same analytical framework for quantitative description.

[0036] S5. Generate a target compensation voltage complex quantity that includes positive sequence control quantity and negative sequence compensation quantity based on the comprehensive state index.

[0037] Specifically, the positive sequence control quantity is used to regulate the overall voltage level, while the negative sequence compensation quantity is used to suppress three-phase imbalance.

[0038] S6. Based on the target compensation voltage phase quantity, a compensation current is injected into the end of the transformer area through a parallel control device connected in parallel to the end of the transformer area.

[0039] like Figure 2 As shown, the parallel control device is connected to the end of the transformer area in parallel through the output filter branch. Under the condition of maintaining the original feeder structure and load connection method, it injects compensation current and directly controls the voltage of the end node.

[0040] The method in this embodiment eliminates the reliance on current transformers through purely voltage-driven control logic, avoiding power outages for construction and enabling flexible voltage regulation at the end of the distribution area without altering the original line structure. Furthermore, this method directly uses voltage monitoring results for control decisions, achieving integrated and coordinated monitoring and control.

[0041] Specifically, the parallel control device generates a corresponding three-phase time-domain reference signal based on the target compensation voltage multiphase quantity, and injects it into the terminal line of the transformer area in parallel through the output filter branch. Since the control device is connected in parallel, its injection effect is reflected as an equivalent adjustment of the terminal node voltage, without changing the original feeder structure or load connection method.

[0042] In practical engineering applications, considering factors such as device capacity, current carrying capacity, and thermal stability, this implementation method constrains the compensation amplitude through internal limiting and protection logic to ensure safe and continuous live control under different operating conditions.

[0043] In one possible implementation, in step S2, the fundamental voltage complex quantity is extracted based on the instantaneous three-phase voltage signal, specifically as follows: S21. Perform DC bias removal processing on the instantaneous three-phase voltage signal to eliminate the DC component that may be introduced during the sampling process.

[0044] S22. Using windowed sliding discrete Fourier transform (Sliding DFT), the fundamental voltage complex phasor of each phase voltage is extracted, specifically:

[0045] in, Indicates separation; For the sake of separation At any moment The fundamental voltage complex phasor; These are the instantaneous sampled values ​​corresponding to the phases; The sliding window length is the number of sampling points per power frequency cycle. For example, when the power frequency is 50Hz and the sampling frequency is 12.8kHz, Take 256; For the window function, you can choose either the Hanning window or the Hamming window to suppress spectral leakage.

[0046] To ensure that the obtained fundamental voltage amplitude matches the actual effective value, the sliding DFT results are calibrated using a window function coherent gain. This involves normalizing the obtained complex phasors according to preset calibration coefficients. The magnitude of the complex phasor represents the fundamental voltage amplitude, and the phase angle represents the phase information. In this way, the obtained three-phase fundamental voltage complex phasors can serve as a unified and stable voltage state description, providing accurate input for sequence component analysis.

[0047] In other words, the fundamental characteristics of the acquired three-phase voltage instantaneous signals are processed to reduce the impact of factors such as DC bias, harmonic components, measurement noise, and asynchronous sampling on control decisions.

[0048] In one possible implementation, in step S3, a symmetrical component transformation is performed on the fundamental voltage complex phasor to obtain the positive-sequence voltage component and the negative-sequence voltage component, specifically using the following calculation formula:

[0049] in, Represents the complex phasor of the three-phase fundamental voltage; These represent the zero-sequence, positive-sequence, and negative-sequence voltage complexes, respectively. Represents the rotation operator; This indicates the overall power supply voltage level; This indicates the degree of three-phase imbalance.

[0050] Based on this, a voltage imbalance index is constructed to quantify governance objectives and evaluate control effectiveness.

[0051] in, Indicates the degree of voltage imbalance (%). , Indicates the positive and negative sequence voltage amplitudes.

[0052] In one possible implementation, step S4 involves generating a comprehensive state index based on the positive-sequence voltage component and the negative-sequence voltage component, specifically including: S41. Generate a positive sequence voltage deviation based on the positive sequence voltage component and the preset reference voltage, as follows:

[0053] in, Indicates time Positive sequence voltage deviation; This represents the positive sequence voltage amplitude. The preset reference voltage can be set according to the rated voltage of the transformer area, such as 220V, or it can be dynamically adjusted by the operation and maintenance strategy.

[0054] S42. Obtain the amplitude of the negative sequence voltage component. It directly reflects the degree of imbalance of the three-phase voltage at the end of the transformer substation.

[0055] S43. Based on the magnitudes of the positive-sequence voltage deviation and the negative-sequence voltage component, the comprehensive state index is generated by weighted summation, specifically as follows:

[0056] in, It is a comprehensive status indicator; This is the imbalance weighting coefficient, used to adjust the degree of influence of three-phase imbalance control in the overall control. It should be noted that the imbalance weighting coefficient can be adjusted according to the requirements of the transformer substation for three-phase imbalance control. When the substation is sensitive to imbalance issues, it can be appropriately increased. The value of .

[0057] In actual operation at the end of a distribution transformer area, undervoltage, overvoltage, and three-phase imbalance often occur alternately or in combination. Furthermore, load fluctuations and changes in distributed photovoltaic output cause frequent voltage state switching within a short period. To avoid frequent start-ups and shutdowns of the control strategy and improve regulation stability, this invention introduces a comprehensive state discrimination mechanism based on the analysis results of positive and negative sequence voltage components. This mechanism provides a unified quantitative assessment of the voltage operating state at the end of the distribution transformer area and generates control targets accordingly.

[0058] In this way, the overall voltage level and the degree of three-phase imbalance are quantified in a single index, enabling unified identification of undervoltage, overvoltage and three-phase imbalance problems, and providing a single control basis for regulation and decision-making.

[0059] In one possible implementation, after generating the comprehensive state index, to avoid frequent start-stop of the control strategy and improve the stability of regulation, the comprehensive state index is compared with preset input thresholds. and preset exit threshold Compare. Input threshold. Greater than the exit threshold This creates a hysteresis range, suppresses state jitter, avoids frequent start-stop of the control system near the boundary, and improves control stability.

[0060] The specific judgment logic is as follows: The comprehensive status index is compared with the preset input threshold and the preset exit threshold, respectively; When the comprehensive status index is greater than the input threshold, it is determined to be an overvoltage-dominated state. At this time, the system enters the suppression and regulation zone and the voltage at the end of the transformer area needs to be reduced. When the comprehensive status index is less than the negative value of the input threshold, it is determined to be an undervoltage-dominated state. At this time, the system enters the boost adjustment zone and needs to increase the voltage at the end of the distribution area. When the absolute value of the comprehensive status index is less than the exit threshold, the voltage is considered to be within the acceptable range, the current control state is maintained, and the strong control zone is exited.

[0061] The discrimination logic can be expressed as follows:

[0062] By setting input thresholds and exit threshold ,and This forms a state discrimination mechanism with hysteresis characteristics, thereby creating a hysteresis band and suppressing state jitter.

[0063] For example, the input threshold can be set to 5V and the output threshold to 3V. When the positive sequence voltage deviation reaches 5V or more, the adjustment is started and will stop when the deviation falls back to below 3V. This can effectively suppress state jitter and improve the stability of system operation.

[0064] In one possible implementation, in step S5, a target compensation voltage complex quantity containing positive-sequence control and negative-sequence compensation quantities is generated based on the comprehensive state index. The specific implementation process is as follows: S51. Based on the deviation between the positive sequence voltage component and the preset reference voltage, a positive sequence control amplitude is generated through proportional-integral adjustment, specifically as follows:

[0065] in, Indicates the positive sequence control amplitude; This represents the positive sequence voltage deviation. These are the proportional and integral coefficients, respectively. This is the sampling period. It should be noted that the proportional-integral coefficient can be tuned according to the dynamic response requirements of the transformer area.

[0066] In other words, the goal of positive sequence control is to bring the overall voltage level at the end of the transformer area back to the reference range, and the control amount is obtained by proportional-integral adjustment of the positive sequence voltage deviation.

[0067] S52. Project the positive sequence control amplitude onto the phase direction of the positive sequence voltage component to generate the complex phase quantity of the positive sequence control quantity.

[0068] In other words, after generating the positive-sequence control amplitude, to ensure that the direction of the control action is consistent with the physical meaning of the positive-sequence voltage, it needs to be projected onto the phase direction of the positive-sequence voltage component, generating a complex phasor of the positive-sequence control quantity. Through phase projection, it can be ensured that the positive-sequence compensation only affects the amplitude adjustment without introducing phase disturbances. The projection calculation formula is as follows:

[0069] in, The multiphase quantity is the positive-sequence control quantity; It is a positive-sequence voltage complex phasor; This represents the positive sequence voltage amplitude.

[0070] S53. Multiply the complex phase quantity of the negative sequence voltage component with the preset negative sequence suppression coefficient and invert it to generate the complex phase quantity of the negative sequence compensation quantity.

[0071] In other words, a reverse injection strategy is adopted for the negative sequence voltage component, and its control objective is to reduce the amplitude of the negative sequence voltage, thereby suppressing three-phase imbalance.

[0072] in, The multiphase quantity is the negative sequence compensation quantity; It is a negative sequence voltage complex phasor; This is the negative order suppression coefficient, which takes a value between 0 and 1 and can be adjusted according to the required intensity of imbalance suppression.

[0073] S54. The complex phase quantity of the positive sequence control quantity is superimposed with the complex phase quantity of the negative sequence compensation quantity to generate the target compensation voltage complex phase quantity.

[0074] In other words, based on the decoupling of positive and negative sequences, the two types of compensation quantities are superimposed to form the target compensation command of the parallel control device. That is, the complex phase quantity of the positive sequence control quantity is superimposed with the complex phase quantity of the negative sequence compensation quantity to generate the target compensation voltage complex phase quantity.

[0075] in, The target compensation voltage complex quantity injected in parallel is used to uniformly describe the comprehensive control effect of positive sequence voltage regulation and negative sequence suppression.

[0076] By using this positive-negative sequence decoupling generation method, overall voltage regulation and imbalance suppression are unified under the same control framework. The two are independent yet synergistic, avoiding the mutual coupling between different control objectives.

[0077] The core of this implementation lies in the coordinated implementation of undervoltage / overvoltage regulation and three-phase imbalance mitigation within a unified control framework. Unlike traditional control methods that only address a single voltage problem, this invention utilizes the physical decoupling characteristics of positive and negative sequence components to map overall voltage level regulation and imbalance suppression to positive and negative sequence control channels respectively. This avoids mutual coupling between different regulation objectives and improves regulation stability and interpretability.

[0078] In one possible implementation, after injecting compensation current into the end of the transformer area, the method further includes: The three-phase voltage instantaneous signal at the end of the transformer area is reacquired, and the updated positive-sequence voltage component and the updated negative-sequence voltage component are calculated based on the reacquired three-phase voltage instantaneous signal. Specifically, the fundamental wave extraction and symmetrical component transformation are repeatedly performed based on the reacquired three-phase voltage instantaneous signal to calculate the updated positive-sequence voltage component and the updated negative-sequence voltage component.

[0079] When the updated positive-sequence voltage component fails to return to the preset reference range, or the amplitude of the updated negative-sequence voltage component fails to drop below the preset threshold, at least one of the following is corrected: the proportional-integral coefficient used to generate the positive-sequence control quantity, the negative-sequence suppression coefficient used to generate the negative-sequence compensation quantity, or the weighting coefficient used to generate the comprehensive state index.

[0080] For example, the voltage acceptable range and the unbalance threshold are used as the evaluation criteria for the control effect. The preset reference range for the positive sequence voltage is set to -5% to +5% of the rated voltage. For example, for a 220V system, the reference range is 209V to 231V. The preset threshold for the negative sequence voltage amplitude is set to 2% of the rated voltage, i.e., 4.4V.

[0081] When the updated positive-sequence voltage component returns to the preset reference range and the amplitude of the updated negative-sequence voltage component drops below the preset threshold, it is determined that the regulation has achieved the expected effect and the system enters a steady-state maintenance state.

[0082] If the updated positive-sequence voltage component fails to return to the preset reference range, or if the amplitude of the updated negative-sequence voltage component fails to decrease below the preset threshold, it indicates that the control effect does not meet the requirements. In this case, the control parameters are adaptively corrected based on the changing trends of the positive-sequence deviation and negative-sequence index. The correction targets include the proportional-integral coefficients used to generate the positive-sequence control quantity. The negative order suppression coefficient used to generate the negative order compensation quantity Or the weighting coefficients used to generate the comprehensive state index. At least one of the following. The correction adopts a small step approach, for example, each correction is 5% of the original coefficient, in order to enhance the system's adaptability to unsteady conditions such as load fluctuations and changes in distributed photovoltaic output, and to avoid control oscillations caused by sudden parameter changes.

[0083] Through the above verification and correction mechanisms, a closed-loop collaborative process of monitoring-judgment-control-re-monitoring is formed, thereby achieving continuous, stable and flexible management of the voltage at the end of the transformer area.

[0084] The present invention provides a voltage monitoring and coordinated control system for transformer substations based on current-free sampling. The system is used to perform the method described in any of the above embodiments. The system includes a voltage monitoring device, a controller, and a parallel control device.

[0085] Voltage monitoring devices are installed in parallel at the end of the low-voltage distribution transformer area to collect real-time three-phase voltage instantaneous signals at the end of the area. The voltage monitoring devices can be fixed or portable, and the installation location is chosen at a voltage-sensitive point at the end of the transformer area.

[0086] The controller is connected to a voltage monitoring device and receives voltage signals collected by the device. The controller has an internal algorithm module configured to perform the following functions: extract the fundamental voltage complex phase from the instantaneous three-phase voltage signal; perform symmetrical component transformation on the fundamental voltage complex phase to obtain positive-sequence and negative-sequence voltage components; generate a comprehensive state index based on the positive-sequence and negative-sequence voltage components; and generate a target compensation voltage complex phase containing positive-sequence control and negative-sequence compensation quantities based on the comprehensive state index.

[0087] The parallel control device is connected to the controller and connected in parallel to the end of the distribution area. It is used to inject compensation current into the end of the distribution area according to the target compensation voltage phase quantity. The parallel control device includes a parallel converter and an output filter branch. The parallel converter is connected in parallel to the distribution line at the end of the distribution area through the output filter branch. The parallel connection method does not require changes to the original feeder structure or power outage construction, and has good engineering applicability.

[0088] In practical engineering applications, considering factors such as device capacity, current carrying capacity and thermal stability, this implementation method constrains the compensation amplitude through internal limiting and protection logic to ensure safe and continuous live control under different operating conditions.

[0089] This system does not require the external installation of current transformers or clamp-on current sensors on the power distribution lines during operation. All control decisions are generated based on voltage monitoring data, avoiding the construction complexity and power outage risks associated with the installation of current sampling devices.

[0090] In one possible implementation, the controller is also configured as follows: A positive-sequence voltage deviation is generated based on the positive-sequence voltage component and a preset reference voltage, as follows:

[0091] in, Indicates time Positive sequence voltage deviation; This represents the positive sequence voltage amplitude. The preset reference voltage can be set according to the rated voltage of the transformer area, such as 220V, or it can be dynamically adjusted by the operation and maintenance strategy.

[0092] Obtain the amplitude of the negative sequence voltage component. .

[0093] The comprehensive state index is generated by weighted summation based on the magnitudes of the positive-sequence voltage deviation and the negative-sequence voltage component, specifically as follows:

[0094] in, It is a comprehensive status indicator; This is the imbalance weighting coefficient, used to adjust the degree of influence of three-phase imbalance control in the overall control. It should be noted that the imbalance weighting coefficient can be adjusted according to the requirements of the transformer substation for three-phase imbalance control. When the substation is sensitive to imbalance issues, it can be appropriately increased. The value of .

[0095] In one possible implementation, the controller is also configured as follows: The comprehensive status index is compared with the preset input threshold and the preset exit threshold, respectively; When the comprehensive status index is greater than the input threshold, it is determined to be an overvoltage-dominated state. At this time, the system enters the suppression and regulation zone and the voltage at the end of the transformer area needs to be reduced. When the comprehensive status index is less than the negative value of the input threshold, it is determined to be an undervoltage-dominated state. At this time, the system enters the boost adjustment zone and needs to increase the voltage at the end of the distribution area. When the absolute value of the comprehensive status index is less than the exit threshold, the voltage is considered to be within the acceptable range, the current control state is maintained, and the strong control zone is exited.

[0096] In one possible implementation, the controller is also configured as follows: Based on the deviation between the positive sequence voltage component and the preset reference voltage, a positive sequence control amplitude is generated through proportional-integral adjustment, specifically as follows:

[0097] in, Indicates the positive sequence control amplitude; This represents the positive sequence voltage deviation. These are the proportional and integral coefficients, respectively. This is the sampling period. It should be noted that the proportional-integral coefficient can be tuned according to the dynamic response requirements of the transformer area.

[0098] The positive-sequence modulation amplitude is projected onto the phase direction of the positive-sequence voltage component to generate the complex phase of the positive-sequence modulation quantity. The projection calculation formula is as follows:

[0099] in, The multiphase quantity is the positive-sequence control quantity; It is a positive-sequence voltage complex phasor; This represents the positive sequence voltage amplitude.

[0100] The complex phase of the negative sequence voltage component is multiplied by a preset negative sequence suppression coefficient and then inverted to generate the complex phase of the negative sequence compensation quantity.

[0101] in, The multiphase quantity is the negative sequence compensation quantity; It is a negative sequence voltage complex phasor; This is the negative order suppression coefficient, which takes a value between 0 and 1 and can be adjusted according to the required intensity of imbalance suppression.

[0102] The complex phase quantity of the positive sequence control quantity is superimposed with the complex phase quantity of the negative sequence compensation quantity to generate the target compensation voltage complex phase quantity:

[0103] in, The target compensation voltage complex quantity injected in parallel is used to uniformly describe the comprehensive control effect of positive sequence voltage regulation and negative sequence suppression.

[0104] In one implementation, the controller is further configured to calculate updated positive-sequence voltage components and updated negative-sequence voltage components based on the re-acquired three-phase voltage instantaneous signals. When the updated positive-sequence voltage component does not return to a preset reference range, e.g., 209V to 231V, or the amplitude of the updated negative-sequence voltage component does not decrease below a preset threshold, e.g., 4.4V, the proportional-integral coefficient used to generate the positive-sequence control quantity is adjusted. The negative order suppression coefficient used to generate the negative order compensation quantity Or the weighting coefficients used to generate the comprehensive state index. At least one of the parameters should be corrected. The correction should be made in small increments, for example, each correction should be 5% of the original coefficient, to ensure that the system can adjust smoothly during dynamic changes and avoid control oscillations caused by sudden parameter changes.

[0105] The method and system provided by this invention achieve comprehensive voltage management at the end of a transformer substation by synergistically combining voltage monitoring and flexible regulation, without relying on current sampling. The method, based on a positive-negative sequence decoupled control framework, can simultaneously handle undervoltage, overvoltage, and three-phase imbalance problems. Furthermore, through closed-loop verification and parameter adaptive correction mechanisms, it improves the system's adaptability to load fluctuations and changes in renewable energy output. The system adopts a parallel connection method, avoiding power outages for construction and exhibiting good engineering applicability.

[0106] In another embodiment of the present invention, a computer device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to achieve a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used in the operation of a method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling.

[0107] In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be Random Access Memory (RAM) or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the above embodiment regarding a method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling.

[0108] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, etc.) containing computer-usable program code.

[0109] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0110] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0111] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0112] This invention also provides a computer program product, which is used to execute any of the above-described methods for monitoring and coordinating voltage at the end of a transformer substation based on current-free sampling. Since the computer program product provided by this invention and the above-described method for monitoring and coordinating voltage at the end of a transformer substation based on current-free sampling belong to the same inventive concept, the computer program product provided by this invention possesses all the advantages of the above-described method for monitoring and coordinating voltage at the end of a transformer substation based on current-free sampling. Therefore, the beneficial effects of the computer program product provided by this invention will not be elaborated upon here.

[0113] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0114] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling, characterized in that, include: The instantaneous three-phase voltage signal at the end of the low-voltage distribution transformer area is collected in real time by a voltage monitoring device connected in parallel at the end of the transformer area. Extract the fundamental voltage complex phase quantity from the instantaneous three-phase voltage signal; The fundamental voltage complex phasor is subjected to symmetrical component transformation to obtain positive-sequence voltage components and negative-sequence voltage components; A comprehensive state index is generated based on the positive-sequence voltage component and the negative-sequence voltage component; Based on the comprehensive state index, a target compensation voltage complex quantity containing positive sequence control quantity and negative sequence compensation quantity is generated; Based on the target compensation voltage phase quantity, compensation current is injected into the end of the transformer area through a parallel control device connected in parallel to the end of the transformer area.

2. The method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling according to claim 1, characterized in that, The step of generating a comprehensive state index based on the positive-sequence voltage component and the negative-sequence voltage component includes: A positive-sequence voltage deviation is generated based on the positive-sequence voltage component and a preset reference voltage; Obtain the amplitude of the negative sequence voltage component; The comprehensive state index is generated by weighted summation based on the magnitudes of the positive-sequence voltage deviation and the negative-sequence voltage component.

3. The method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling according to claim 2, characterized in that, After generating the comprehensive status index, the following is also included: The comprehensive status index is compared with the preset input threshold and the preset exit threshold, respectively; When the comprehensive status index is greater than the input threshold, it is determined to be an overvoltage-dominated state; When the comprehensive status index is less than the negative value of the input threshold, it is determined to be an undervoltage-dominated state. When the absolute value of the comprehensive status index is less than the exit threshold, the current control state is maintained.

4. The method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling according to claim 1, characterized in that, The step of generating the target compensation voltage complex quantity, which includes positive-sequence control and negative-sequence compensation quantities, based on the comprehensive state index includes: Based on the deviation between the positive sequence voltage component and the preset reference voltage, a positive sequence control amplitude is generated through proportional-integral adjustment. The positive-sequence modulation amplitude is projected onto the phase direction of the positive-sequence voltage component to generate the complex phase quantity of the positive-sequence modulation quantity; The complex phase of the negative sequence voltage component is multiplied by a preset negative sequence suppression coefficient and then inverted to generate the complex phase of the negative sequence compensation. The complex phase quantity of the positive sequence control quantity is superimposed with the complex phase quantity of the negative sequence compensation quantity to generate the target compensation voltage complex phase quantity.

5. The method for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling according to claim 1, characterized in that, After injecting compensation current into the end of the transformer area, the process further includes: The instantaneous three-phase voltage signals at the end of the transformer area are reacquired, and the updated positive-sequence voltage components and the updated negative-sequence voltage components are calculated based on the reacquired instantaneous three-phase voltage signals. When the updated positive-sequence voltage component fails to return to the preset reference range, or the amplitude of the updated negative-sequence voltage component fails to drop below the preset threshold, at least one of the following is corrected: the proportional-integral coefficient used to generate the positive-sequence control quantity, the negative-sequence suppression coefficient used to generate the negative-sequence compensation quantity, or the weighting coefficient used to generate the comprehensive state index.

6. A system for monitoring and coordinating the voltage at the end of a transformer substation based on current-free sampling, characterized in that, include: A voltage monitoring device is installed in parallel at the end of the low-voltage distribution transformer area to collect the instantaneous three-phase voltage signal at the end of the transformer area in real time. A controller, connected to the voltage monitoring device, is configured to: Extract the fundamental voltage complex phase quantity from the instantaneous three-phase voltage signal; The fundamental voltage complex phasor is subjected to symmetrical component transformation to obtain positive-sequence voltage components and negative-sequence voltage components; A comprehensive state index is generated based on the positive-sequence voltage component and the negative-sequence voltage component; Based on the comprehensive state index, a target compensation voltage complex quantity containing positive sequence control quantity and negative sequence compensation quantity is generated; A parallel control device is connected to the controller and connected in parallel to the end of the transformer area, used to inject compensation current into the end of the transformer area according to the target compensation voltage phase quantity.

7. The distribution area end voltage monitoring and coordinated control system based on current-free sampling according to claim 6, characterized in that, The controller is also configured to: A positive-sequence voltage deviation is generated based on the positive-sequence voltage component and a preset reference voltage; Obtain the amplitude of the negative sequence voltage component; The comprehensive state index is generated by weighted summation based on the magnitudes of the positive-sequence voltage deviation and the negative-sequence voltage component.

8. A transformer substation end voltage monitoring and coordinated control system based on current-free sampling according to claim 7, characterized in that, The controller is also configured to: The comprehensive status index is compared with the preset input threshold and the preset exit threshold, respectively; When the comprehensive status index is greater than the input threshold, it is determined to be an overvoltage-dominated state; When the comprehensive status index is less than the negative value of the input threshold, it is determined to be an undervoltage-dominated state. When the absolute value of the comprehensive status index is less than the exit threshold, the current control state is maintained.

9. A transformer substation end voltage monitoring and coordinated control system based on current-free sampling according to claim 6, characterized in that, The controller is also configured to: Based on the deviation between the positive sequence voltage component and the preset reference voltage, a positive sequence control amplitude is generated through proportional-integral adjustment. The positive-sequence modulation amplitude is projected onto the phase direction of the positive-sequence voltage component to generate the complex phase quantity of the positive-sequence modulation quantity; The complex phase of the negative sequence voltage component is multiplied by a preset negative sequence suppression coefficient and then inverted to generate the complex phase of the negative sequence compensation. The complex phase quantity of the positive sequence control quantity is superimposed with the complex phase quantity of the negative sequence compensation quantity to generate the target compensation voltage complex phase quantity.

10. A transformer substation end voltage monitoring and coordinated control system based on current-free sampling according to claim 6, characterized in that, The controller is also configured to: The instantaneous three-phase voltage signals at the end of the transformer area are reacquired, and the updated positive-sequence voltage components and the updated negative-sequence voltage components are calculated based on the reacquired instantaneous three-phase voltage signals. When the updated positive-sequence voltage component fails to return to the preset reference range, or the amplitude of the updated negative-sequence voltage component fails to drop below the preset threshold, at least one of the following is corrected: the proportional-integral coefficient used to generate the positive-sequence control quantity, the negative-sequence suppression coefficient used to generate the negative-sequence compensation quantity, or the weighting coefficient used to generate the comprehensive state index.

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