UPQC adaptive harmonic suppression method and system based on intelligent terminal

Abstract

The invention relates to a UPQC adaptive harmonic suppression method and system based on an intelligent terminal, and the method comprises the steps: collecting the multi-node electrical quantity of a medium-voltage transformer area through the intelligent terminal, and carrying out the sequential decoupling, thereby obtaining positive, negative and zero-sequence components; carrying out harmonic analysis, counting the content ratio, the phase and the power direction of each order of harmonic, forming a harmonic portrait containing the harmonic source intensity, the impedance resonance risk and the interphase coupling coefficient, identifying dominant and cross harmonics according to the harmonic portrait, and generating a UPQC parallel unit target compensation current instruction and a series unit reference voltage instruction on line; and the parallel side of the UPQC executes selective harmonic injection and dynamic damping, and the series side is matched to perform voltage compensation so as to realize combined suppression. The terminal continuously senses environment change and capacitor switching, and dynamically adjusts a sampling window and inhibits bandwidth. According to the method and the system, accurate perception is realized by constructing a harmonic portrait, and adaptive decision and control are carried out, so that the combined suppression effect and the system stability of the UPQC in a complex harmonic environment can be improved.

Description

Technical Field

[0001] This invention relates to the field of power system technology, specifically to a UPQC adaptive harmonic suppression method and system based on a smart terminal. Background Technology

[0002] With the rapid development of power electronics technology, a large number of nonlinear loads, distributed power sources, and flexible loads have been connected to medium-voltage distribution substations. While improving energy utilization efficiency, this has also led to increasingly complex harmonic problems in the power grid. Harmonic pollution not only causes equipment overheating and malfunctions but can also trigger system resonance, seriously threatening the safe and stable operation of the power grid and power quality. To mitigate harmonics, Unified Power Quality Conditioners (UPQCs), as a comprehensive device integrating series and parallel compensation, have been widely used. Traditional UPQC control strategies are usually based on compensation algorithms with fixed parameters, which can effectively suppress harmonics of specific orders. However, the load composition and operation mode of medium-voltage distribution substations are highly time-varying, and their harmonic spectrum characteristics are not static, exhibiting complex characteristics such as multi-source, wideband, and cross-coupling. In addition, existing reactive power compensation devices (such as switched capacitor banks) in the substation may change the network impedance characteristics during switching, interacting with UPQCs or background harmonics and inducing new resonance risks.

[0003] Faced with the aforementioned complex operating conditions, some existing technologies have attempted to improve adaptability by adding harmonic detection steps. However, most of these methods still focus on compensating for single types of harmonics or local nodes, lacking a global perception and collaborative analysis of the overall harmonic situation of the transformer area. This makes it difficult to achieve refined modeling and joint optimization of sequence components, interphase coupling, and impedance resonance risks.

[0004] Therefore, how to enable UPQC systems to have stronger environmental awareness, situational understanding and adaptive control capabilities, so as to achieve accurate, safe and coordinated suppression of dominant harmonics and cross-coupled harmonics in complex and ever-changing medium-voltage distribution area environments, has become a topic worthy of in-depth research in the field of power quality management. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a UPQC adaptive harmonic suppression method and system based on a smart terminal. It achieves accurate perception by constructing a harmonic profile and performs adaptive decision-making and control, which can improve the joint suppression effect and system stability of UPQC in complex harmonic environments.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a UPQC adaptive harmonic suppression method based on a smart terminal, comprising: The intelligent terminal collects the current and voltage waveforms of multiple nodes in the medium-voltage test area in real time, and performs sequence decoupling on the current and voltage waveforms to obtain positive sequence, negative sequence and zero sequence components. Harmonic analysis is performed on each sequence component, and the content, phase and harmonic power direction of each order harmonic are statistically analyzed to form a harmonic profile of the transformer area that includes the harmonic source intensity distribution, impedance resonance risk index and phase coupling coefficient. The intelligent terminal takes the harmonic profile as input, identifies the dominant harmonic order and cross-coupled harmonics under the current operating conditions, calculates the target compensation current to be injected into the UPQC parallel unit online based on the identification results, determines the weight coefficient of each sequence component, generates the target reference current command, and generates the reference voltage command for voltage mode correction of the series unit based on the voltage quality assessment results. The UPQC device receives the target reference current command and the reference voltage command. Its parallel unit performs selective harmonic injection and dynamic active damping, and its series unit performs voltage compensation to achieve joint suppression of dominant and cross-order harmonics. The intelligent terminal continuously senses environmental changes in the transformer area and switching signals of the capacitors in the reactive power compensation device, and dynamically adjusts the sampling window length and suppression bandwidth.

[0007] Furthermore, the method for constructing the harmonic profile includes: Harmonic analysis of positive-sequence, negative-sequence, and zero-sequence components is performed using fast Fourier transform or wavelet transform to obtain the content rate and phase information of each harmonic. The direction of harmonic power flow is determined by comparing the phase difference between harmonic voltage and harmonic current at different nodes. The harmonic source intensity distribution is determined based on the harmonic current amplitude and harmonic power flow direction information of each node. It is determined by analyzing the direction of harmonic power flow from the node to the power grid and combining it with the magnitude of the harmonic current amplitude. The impedance resonance risk index is based on harmonic analysis results and is quantified by calculating the ratio of the change in node harmonic voltage to the change in harmonic current. The interphase coupling coefficient is quantified by analyzing the correlation between the amplitude and phase of the harmonic voltage and harmonic current at different nodes.

[0008] Furthermore, the process of constructing the harmonic profile is based on a dynamically updated harmonic spectrum database and a pattern recognition algorithm; The harmonic spectrum database is used to record the harmonic amplitude, phase, harmonic power flow direction, and time-varying trend of each node. The pattern recognition algorithm is used to analyze data in the harmonic spectrum database to identify the dominant harmonic source types and their dynamic propagation paths within the region.

[0009] Furthermore, the online calculation model for the target compensation current to be injected into the UPQC parallel unit simultaneously considers downstream harmonic current suppression and upstream background harmonic voltage isolation. The objective function is set to minimize the weighted sum of the total harmonic distortion rate of the current and the total harmonic distortion rate of the voltage at the common connection point. The weighted sum incorporates an adaptive weight allocation strategy, which dynamically adjusts the weight ratio of total harmonic distortion of current and total harmonic distortion of voltage in the objective function based on the phase coupling coefficient and impedance resonance risk index in the harmonic profile.

[0010] Furthermore, the generation processes of the target reference current command and the reference voltage command are decoupled at the control target level but coordinated at the system-level control level. When generating the target reference current command, the main objective is to suppress the harmonic current at the point of common coupling and the balanced three-phase current, and an impedance resonance risk index is introduced as a damping constraint. When generating reference voltage commands, the main objectives are to maintain the stability of the common coupling point voltage and eliminate specific subharmonic voltages, while also considering the power exchange balance between series and parallel units.

[0011] Furthermore, the dynamic active damping is achieved by introducing a virtual negative resistance feedback loop corresponding to the resonant frequency point in the control algorithm of the parallel unit. The resistance value of the virtual negative resistance is adaptively adjusted according to the impedance resonance risk index in the harmonic profile.

[0012] Furthermore, the specific method for dynamically adjusting the sampling window and suppression bandwidth is as follows: when a signal indicating a change in the transformer area environment or a switching action signal of a capacitor indicates that the system is in a transient process, the sampling window is automatically shortened and the suppression bandwidth is widened. Once the system reaches a steady state, it automatically extends the sampling window and narrows the suppression bandwidth.

[0013] Furthermore, the smart terminal receives the global optimization strategy issued by the main station as the priority strategy; When a communication interruption with the main station is detected or the received policy is significantly inconsistent with the current local harmonic profile, the system automatically switches to a local backoff control policy based on the local harmonic profile.

[0014] Furthermore, the local backoff control strategy is a predictive control mode based on historical harmonic profiles and real-time data: when communication with the main station is interrupted, the intelligent terminal calls the optimal suppression strategy similar to the current operating condition in the historical database as the initial strategy, and makes fine adjustments in combination with the real-time harmonic profile.

[0015] The present invention also provides a UPQC adaptive harmonic suppression system based on a smart terminal, for implementing the above method, comprising: Data sensing module: The intelligent terminal collects the current and voltage waveforms of multiple nodes in the medium-voltage test area in real time, and performs sequence decoupling on the current and voltage waveforms to obtain positive sequence, negative sequence and zero sequence components; Harmonic profile construction module: Performs harmonic analysis on each sequence component, statistically analyzes the content, phase and harmonic power direction of each order harmonic, and forms a harmonic profile of the transformer area including the harmonic source intensity distribution, impedance resonance risk index and interphase coupling coefficient. Optimization Decision Module: The intelligent terminal takes the harmonic profile as input, identifies the dominant harmonic order and cross-coupled harmonics under the current operating conditions, calculates the target compensation current to be injected into the UPQC parallel unit online based on the identification results, determines the weight coefficient of each sequence component, generates the target reference current command, and generates the reference voltage command for voltage mode correction of the series unit based on the voltage quality assessment results. Command execution module: The UPQC device receives the target reference current command and the reference voltage command. Its parallel unit performs selective harmonic injection and dynamic active damping, and its series unit performs voltage compensation to achieve joint suppression of dominant and cross-order harmonics. Dynamic adjustment module: The intelligent terminal continuously senses the environmental change signals in the transformer area and the switching action signals of the switching capacitors in the reactive power compensation device, and dynamically adjusts the sampling window length and suppression bandwidth.

[0016] This invention provides a UPQC adaptive harmonic suppression method and system based on a smart terminal. The method uses a smart terminal to collect current and voltage waveforms from multiple nodes within a medium-voltage distribution area in real time, and performs sequence decoupling on the current and voltage waveforms to obtain positive-sequence, negative-sequence, and zero-sequence components. Harmonic analysis is performed on each sequence component to statistically analyze the content, phase, and harmonic power direction of each harmonic order, forming a harmonic profile of the distribution area including harmonic source intensity distribution, impedance resonance risk index, and interphase coupling coefficient. Using the harmonic profile as input, the smart terminal identifies the dominant harmonic order and cross-coupled harmonics under the current operating conditions, and calculates the UPQC online based on the identification results. The parallel unit needs to inject the target compensation current and determine the weighting coefficients of each sequence component to generate a target reference current command. Simultaneously, based on the voltage quality assessment results, a reference voltage command is generated for voltage pattern correction in the series unit. The UPQC device receives the target reference current command and the reference voltage command. Its parallel unit performs selective harmonic injection and dynamic active damping, while its series unit cooperates to perform voltage compensation, achieving joint suppression of dominant and cross-order harmonics. The intelligent terminal continuously senses environmental change signals in the transformer area and switching action signals of the switching capacitors in the reactive power compensation device, and dynamically adjusts the sampling window length and suppression bandwidth. The resulting benefits include: 1. By constructing a harmonic profile that includes the intensity distribution of harmonic sources, impedance resonance risk index, and interphase coupling coefficient, the accurate perception and quantitative assessment of the harmonic state of the transformer area are realized. It can accurately locate the dominant harmonic source, identify resonance risk points, and quantify the degree of interphase harmonic coupling, thereby providing accurate input information for the UPQC suppression strategy and improving the joint suppression effect of dominant and cross-order harmonics. 2. Based on the dynamic changes of the harmonic profile, the optimal target reference command is generated online, so that the compensation behavior of UPQC always matches the current harmonic situation. An adaptive weight allocation strategy based on the interphase coupling coefficient and resonance risk index is introduced to dynamically adjust the priority of current and voltage management targets, thereby avoiding the failure of the fixed weight strategy under complex working conditions. 3. By sensing environmental changes and capacitor switching actions, the sampling window and suppression bandwidth are automatically adjusted, avoiding the risk of resonance with the reactive power compensation device and ensuring the stability and effectiveness of the system under different operating scenarios. Attached Figure Description

[0017] Figure 1 A flowchart of a UPQC adaptive harmonic suppression method based on a smart terminal is provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of a UPQC adaptive harmonic suppression system based on a smart terminal, provided as an embodiment of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] like Figure 1 As shown, this embodiment provides a UPQC adaptive harmonic suppression method based on a smart terminal, including the following steps: S1. The intelligent terminal collects the current and voltage waveforms of multiple nodes in the medium-voltage test area in real time, and performs sequence decoupling on the current and voltage waveforms to obtain positive sequence, negative sequence and zero sequence components. S2. Perform harmonic analysis on each sequence component, and statistically analyze the content, phase and harmonic power direction of each order harmonic to form a harmonic profile of the transformer area that includes the harmonic source intensity distribution, impedance resonance risk index and phase coupling coefficient. S3. The intelligent terminal takes the harmonic profile as input, identifies the dominant harmonic order and cross-coupled harmonics under the current operating conditions, calculates the target compensation current to be injected into the UPQC parallel unit online based on the identification results, determines the weight coefficient of each sequence component, generates the target reference current command, and generates the reference voltage command for voltage mode correction of the series unit based on the voltage quality assessment results. The S4 and UPQC devices receive the target reference current command and the reference voltage command. Their parallel units perform selective harmonic injection and dynamic active damping, while their series units cooperate to perform voltage compensation, thereby achieving joint suppression of dominant and cross-order harmonics. S5. The intelligent terminal continuously senses the environmental change signals in the transformer area and the switching action signals of the switching capacitors in the reactive power compensation device, and dynamically adjusts the sampling window length and suppression bandwidth.

[0022] In this embodiment, the method for constructing the harmonic profile includes: Harmonic analysis of positive-sequence, negative-sequence, and zero-sequence components is performed using fast Fourier transform or wavelet transform to obtain the content rate and phase information of each harmonic. The direction of harmonic power flow is determined by comparing the phase difference between harmonic voltage and harmonic current at different nodes. The harmonic source intensity distribution is determined based on the harmonic current amplitude and harmonic power flow direction information of each node. It is determined by analyzing the direction of harmonic power flow from the node to the power grid and combining it with the magnitude of the harmonic current amplitude. The impedance resonance risk index is based on harmonic analysis results and is quantified by calculating the ratio of the change in node harmonic voltage to the change in harmonic current. The interphase coupling coefficient is quantified by analyzing the correlation between the amplitude and phase of harmonic voltage and harmonic current at different nodes. Specifically, the construction of the harmonic profile begins with the intelligent terminal simultaneously acquiring three-phase current and voltage waveform data through measurement units deployed at key nodes in the medium-voltage distribution area, such as transformer outlets, the beginning of important branch lines, and large nonlinear load connection points. The terminal applies the symmetrical component method to decouple the original three-phase waveforms, decomposing them into independent positive-sequence, negative-sequence, and zero-sequence components. The purpose is to transform the complex asymmetrical harmonic problem into an independent sequence component space for processing, thereby simplifying the analysis complexity. The terminal then processes the decomposed components... Harmonic analysis is performed on each sequence component. A Fast Fourier Transform (FFT) algorithm is used to convert the time-domain waveform data into a frequency-domain spectrum, accurately extracting the content of each specific harmonic within each sequence component—that is, the ratio of the effective value of that harmonic component to the effective value of the fundamental component—as well as its phase angle information. This allows for a comprehensive understanding of the spectral characteristics and phase relationships of the harmonics. Based on this, to determine the direction of harmonic power flow, the intelligent terminal further calculates the phase difference between the harmonic voltage and harmonic current of the same harmonic at the same node, and makes a judgment based on the characteristics of the power factor angle: if it is determined that the harmonic power flows from the node to the grid, then the node is identified as a harmonic emission source; conversely, if the power flows from the grid to the node, ... If a node is considered a harmonic load, then the terminal first filters out all suspected harmonic sources based on the power flow direction discrimination results. Then, it comprehensively considers the magnitude of the harmonic current amplitude injected into the grid by each node to quantify the intensity. The larger the current amplitude, the higher the source intensity level. Based on this, all harmonic sources are sorted to form a clear harmonic source intensity distribution map. For the quantification of the impedance resonance risk index, the terminal injects a small, specific frequency harmonic current disturbance into the system or utilizes the current changes caused by natural load fluctuations, simultaneously monitoring the harmonic voltage changes at the corresponding frequency points. Then, it estimates the harmonic voltage change by calculating the ratio of the harmonic voltage change to the harmonic current change. The system's equivalent harmonic impedance at this frequency point; if the equivalent harmonic impedance value is significantly higher than the system's normal impedance level, it is determined that there is a high risk of resonance at this frequency point, otherwise it is a low risk, thus drawing the system's impedance resonance risk index spectrum; for the quantification of the interphase coupling coefficient, the terminal analyzes the correlation characteristics between different phase sequence components based on the harmonic voltage and current data of the three phases of each node. For example, by calculating the ratio of negative sequence harmonic voltage to positive sequence harmonic current under a specific harmonic, the coupling strength between positive and negative sequences is evaluated. The higher the ratio, the stronger the interphase harmonic transmission effect, and the interphase coupling coefficient also increases accordingly. Similar methods are used to analyze the interaction relationship between other phase sequences;The intelligent terminal integrates all the data obtained above, including the content, phase, and power flow of each harmonic, the harmonic source intensity distribution at each node, the impedance resonance risk index at each frequency, and the interphase coupling coefficient between each phase sequence, along with their changing trends over time, into a dynamically updated harmonic spectrum database. This forms a multi-dimensional, quantifiable harmonic profile of the transformer area, providing comprehensive and accurate data support for the intelligent suppression decisions of the subsequent UPQC device.

[0023] In this embodiment, the process of constructing the harmonic profile is based on a dynamically updated harmonic spectrum database and a pattern recognition algorithm. The harmonic spectrum database is used to record the harmonic amplitude, phase, harmonic power flow direction, and time-varying trend of each node. The pattern recognition algorithm is used to analyze data in the harmonic spectrum database to identify the dominant harmonic source types and their dynamic propagation paths within the medium-voltage substation area. Specifically, the construction of the harmonic profile relies on a continuously and dynamically updated harmonic spectrum database and the pattern recognition algorithm running on it. This harmonic spectrum database systematically records the harmonic amplitude, phase, harmonic power flow direction, and their changing trends over time at each monitoring node within the medium-voltage substation area. Its update mechanism is based on periodic or event-triggered data acquisition from intelligent terminals. Each harmonic feature data obtained from the analysis is timestamped and stored in a database organized using a time series model, and the data is maintained through a rolling time window management strategy. The system is scalable and focuses on recent conditions. It automatically calculates and updates the statistical characteristics of key harmonic indicators to support trend analysis. Based on this data, the pattern recognition algorithm preprocesses and extracts features from the multidimensional historical and real-time data in the database. Then, through cluster analysis, it automatically identifies load types with similar harmonic emission characteristics within the transformer area, thereby distinguishing different types of dominant harmonic sources. Furthermore, it uses association rule mining and time-series correlation analysis techniques to track the response order and correlation degree of harmonic indicators of each node in the transformer area when a specific harmonic source is active. This allows for the reconstruction of the dynamic propagation path of harmonic disturbances, ultimately forming a comprehensive and intelligent description of the harmonic state of the transformer area from microscopic features to macroscopic laws.

[0024] In this embodiment, the online calculation model for the target compensation current to be injected into the UPQC parallel unit simultaneously considers downstream harmonic current suppression and upstream background harmonic voltage isolation. The objective function is set to minimize the weighted sum of the total harmonic distortion rate of the current and the total harmonic distortion rate of the voltage at the common connection point. The weighted sum incorporates an adaptive weight allocation strategy, dynamically adjusting the weight ratio of total harmonic distortion (THD) of the current and total harmonic distortion (THD) of the voltage in the objective function based on the phase coupling coefficient and impedance resonance risk index in the harmonic profile. Specifically, the target compensation current injected by the UPQC parallel unit is calculated online through a comprehensive optimization model. This model simultaneously covers the dual control objectives of suppressing downstream load harmonic current and isolating upstream grid background harmonic voltage. The core framework of the optimization model integrates the two independent performance indicators of minimizing the THD at the point of common coupling into a unified objective function, i.e., constructing a weighted sum of the two distortion rates. To achieve precise coordination between the control strategy and the real-time operating status of the system, this objective function introduces an adaptive weight allocation strategy. Its decision logic directly depends on the dynamically updated phase coupling coefficient and impedance resonance risk index in the harmonic profile. Specifically, the intelligent terminal reads the phase coupling coefficient and impedance resonance risk index in the harmonic profile in real time during each calculation cycle. The interphase coupling coefficient and impedance resonance risk index are used to determine the system's stability. When the impedance resonance risk index is high, it indicates a risk of system resonance instability. The control algorithm will automatically increase the weight of the total harmonic distortion (THD) of the voltage in the objective function, prioritizing the UPQC's compensation action to ensure the quality of the voltage waveform at the point of common coupling. By enhancing the isolation and compensation of harmonic voltages, system resonance is suppressed, thus prioritizing system stability. When the interphase coupling coefficient is high, it indicates a significant harmonic propagation effect between phases. The control algorithm will correspondingly increase the weight of the total harmonic distortion (THD) of the current, concentrating the UPQC's control resources on suppressing harmonic currents flowing into the grid and blocking the spread of harmonics through interphase coupling, prioritizing the improvement of current quality. Based on this adaptive weight control mechanism that senses the system state in real time, the objective function is transformed into a decision core with dynamic optimization characteristics. By solving this adaptive objective function, the optimal solution is obtained, and a target compensation current command matching the current harmonic situation is generated in real time, ultimately driving the UPQC parallel unit to achieve precise power quality compensation.

[0025] In this embodiment, the generation processes of the target reference current command and the reference voltage command are decoupled in terms of control target but coordinated in terms of system-level control. When generating the target reference current command, the main objective is to suppress the harmonic current at the point of common coupling and the balanced three-phase current, and an impedance resonance risk index is introduced as a damping constraint. When generating the reference voltage command, the primary objectives are to maintain stable voltage at the point of common coupling (PCC) and eliminate specific harmonic voltages, while also considering the power exchange balance between series and parallel units. Specifically, the generation mechanisms of the target reference current command and the reference voltage command follow the principles of control objective decoupling and system-level control coordination. When generating the target reference current command, the control logic focuses on suppressing harmonic current components at the PCC and balancing three-phase harmonic currents. This process first involves real-time detection of the load current to accurately extract harmonic and negative-sequence components. Based on this, an impedance resonance risk index from the harmonic profile is introduced as a dynamic damping constraint. This impedance resonance risk index is converted into a corresponding virtual damping admittance value. As the system resonance risk increases, this admittance value increases accordingly, resulting in a final calculated target reference current command that includes not only compensation components for offsetting load harmonics but also a component superimposed to suppress system resonance. The active damping current component; when generating the reference voltage command, the control logic focuses on maintaining the stability of the point of common coupling voltage and eliminating specific sub-background harmonic voltages. By monitoring the grid-side voltage waveform, it calculates the voltage value required to maintain the rated and sinusoidal point of common coupling voltage. At the same time, this process comprehensively considers the power exchange balance requirements between series and parallel units, that is, the stable maintenance of the DC-side capacitor voltage is incorporated into the calculation of the voltage command as an inherent constraint, so as to ensure that the reference voltage command can achieve the voltage compensation function while avoiding device instability due to power imbalance. The generation processes of the above two commands are independent in terms of control objectives, but at the system level, they are coordinated through a unified upper-level coordinator. This coordinator globally optimizes the operation priority and output amplitude of the two-sided units based on the real-time updated harmonic profile, thereby ensuring that the unified power quality regulator can achieve efficient and stable coordinated operation under complex operating conditions.

[0026] In this embodiment, the dynamic active damping is achieved by introducing a virtual negative resistance feedback loop corresponding to the resonant frequency point into the control algorithm of the parallel unit. The resistance value of the virtual negative resistance is adaptively adjusted according to the impedance resonance risk index in the harmonic profile. The core of the dynamic active damping function is that, in the control algorithm of the parallel unit of the unified power quality regulator, a virtual negative resistance feedback loop is embedded for the system resonant frequency point identified by the harmonic profile. This implementation process begins by accurately determining one or more specific frequency points in the current system that have resonance risk based on the impedance frequency characteristics analysis in the harmonic profile. Subsequently, the control algorithm monitors the harmonic current component flowing through the output terminal of the parallel unit at the target resonant frequency point in real time through a high-precision sensing device, and uses this current signal as the input signal of the virtual negative resistance feedback loop. This feedback loop multiplies the harmonic current component by an adjustable negative resistance gain coefficient, and the result produces a negative voltage component that is linearly proportional to the harmonic current. This voltage component is superimposed on the original harmonic compensation of the parallel unit. Above the voltage command; from the system side, this control behavior is equivalent to connecting a negative resistor element in parallel at the resonant frequency point. By offsetting the inherent parasitic positive resistance of the power grid line, the peak equivalent impedance at that frequency point is effectively reduced, thereby suppressing resonance. The resistance value of this virtual negative resistor, i.e., the negative resistance gain coefficient, is adaptively adjusted according to the impedance resonance risk index dynamically updated in the harmonic profile: when the impedance resonance risk index is lower than the preset warning threshold, the algorithm sets the virtual negative resistor value to a higher absolute value, keeping its damping effect at a low level to avoid interfering with the normal dynamic response of the control system; when the impedance resonance risk index reaches or exceeds the preset warning threshold, the algorithm dynamically reduces the absolute value of the virtual negative resistor, enhancing its negative admittance effect, thereby increasing the active damping strength at that frequency point and rapidly suppressing the formation and amplification of resonance. This adaptive adjustment mechanism based on real-time system impedance state perception ensures that the dynamic active damping function can achieve the optimal balance between maintaining control accuracy and providing strong resonance suppression.

[0027] In this embodiment, the specific strategy for dynamically adjusting the sampling window and suppression bandwidth is as follows: when a signal indicating a change in the transformer area environment or a switching capacitor switching action signal indicates that the system is in a transient process, the sampling window is automatically shortened and the suppression bandwidth is widened. Once the system reaches steady state, it automatically extends the sampling window and narrows the suppression bandwidth. Specifically, the strategy of dynamically adjusting the sampling window and suppression bandwidth constitutes the core of the system's adaptability, and its operating mechanism is based on the accurate identification and classification of the substation's operating state. This strategy divides the operating state into transient and steady-state processes according to the system's dynamic characteristics, and implements differentiated parameter configuration strategies for different states, aiming to ensure that the harmonic mitigation system maintains rapid response capabilities while guaranteeing high-precision measurement and suppression effects.

[0028] When the intelligent terminal detects signals indicating a sudden change in the system through the sensing unit, including but not limited to switching commands of capacitors, large nonlinear load start-up and shutdown operations detected by load monitoring devices, or environmental changes in the distribution area indicating drastic fluctuations in electrical parameters, the system determines that it has entered a transient state. In this state, the core objective of the control algorithm is to improve the system's response speed and robustness, preventing instantaneous instability caused by parameter mutations. To achieve this objective, the control algorithm performs the following adjustments: It automatically shortens the sampling window length for harmonic analysis, reducing the number of data points used in the analysis, allowing the algorithm to perform spectral calculations based on waveform data with a shorter time scale. While this reduces frequency resolution to some extent, it significantly shortens the computational delay from data acquisition to analysis result output, enabling the unified power quality regulator to quickly detect harmonic state changes and promptly initiate compensation. Simultaneously, it automatically widens the bandwidth of the suppression algorithm, temporarily increasing the equivalent bandwidth of the compensation current tracking control loop, enabling the control system to respond to higher frequency dynamic changes, improving the tracking capability of rapidly changing harmonics, and ensuring that the compensation current follows the load harmonic current changes in a timely manner, thereby maintaining common connectivity. The quality of the current waveform at the point effectively suppresses voltage fluctuations and potential oscillation risks during transient processes. When the aforementioned abrupt signals disappear, and key system parameters, including the effective values ​​of voltage and current, and the content of each major subharmonic, remain within a preset stable threshold range for several consecutive power frequency cycles, the system is determined to have entered a steady-state process. In this state, the goal of the control algorithm is to improve the accuracy and selectivity of harmonic mitigation. The control algorithm accordingly performs the following adjustments: automatically extending the sampling window length of harmonic analysis, i.e., increasing the number of data points used in the analysis, so that the spectrum analysis obtains higher frequency resolution, accurately distinguishing harmonics and interharmonic components with similar frequencies and accurately measuring their amplitude and phase characteristics, providing a guarantee for generating high-precision compensation commands; at the same time, automatically narrowing the bandwidth of the suppression algorithm, i.e., adjusting the bandwidth of the control system to a narrower range, so that the control system has higher compensation gain and selectivity for specific subharmonics, and at the same time has stronger suppression capabilities for high-frequency noise and non-target spectrum components. This helps to unify the centralized control resources of the power quality regulator to accurately suppress specific dominant harmonics, avoid interference with non-target frequency components, thereby improving the mitigation accuracy and overall system efficiency.

[0029] In this embodiment, the smart terminal receives the global optimization strategy issued by the main station as the priority strategy; When a communication interruption with the master station is detected, or when the received strategy is significantly inconsistent with the current local harmonic profile, the system automatically switches to a local backoff control strategy based on the local harmonic profile. In this embodiment, the local backoff control strategy is a predictive control mode based on historical harmonic profiles and real-time data: when communication with the master station is interrupted, the intelligent terminal calls the optimal suppression strategy similar to the current operating condition in the historical database as the initial strategy, and performs fine-tuning based on the real-time harmonic profile. Specifically, the intelligent terminal's control strategy execution follows the principle of combining master station priority with local autonomous backoff. During normal system operation, the intelligent terminal prioritizes receiving and executing the strategy initiated by the superior station. The master station issues a global optimization strategy based on the overall operation status of the power grid. When the intelligent terminal detects an interruption in the communication connection with the master station through continuous heartbeat detection and data verification mechanisms, or discovers a fundamental conflict between the received master station strategy parameters and the actual system state reflected in the harmonic profile generated by local real-time analysis through consistency verification, the system automatically triggers the control switching logic, seamlessly switching from the master station strategy mode to a fallback control mode that relies entirely on local calculations. This local fallback control strategy is a predictive control mode based on historical experience and real-time situational awareness. Its core implementation mechanism includes two consecutive stages: Upon confirmation of the communication interruption, the smart terminal immediately queries its built-in historical database. This database archives harmonic profile snapshots under different historical operating conditions and their corresponding optimal suppression strategy parameter sets, verified through practice. The terminal then uses a multi-dimensional similarity matching algorithm to compare the currently generated harmonic profile with historical records, retrieving the historical scenario most similar to the current system state and invoking its corresponding optimal suppression strategy as the initial control parameters. Subsequently, a dynamic fine-tuning phase begins. This phase does not end with simply applying historical strategies, but rather uses the initial strategy as a baseline framework, combining it with continuously updated real-time harmonic profile data for closed-loop optimization. The fine-tuning algorithm compares the expected compensation effect of historical strategies with the actual compensation effect reported by sensors, and adaptively adjusts key parameters in the initial strategy, including harmonic compensation weight allocation, active damping strength, and target harmonic selectivity, based on changes in system state revealed by real-time harmonic profiles, such as fluctuations in specific harmonic content, migration of resonance risk levels, or changes in interphase coupling strength. This ensures that the control output maintains a precise match with the real-time state of the system. Through this mechanism, when the master station strategy fails, the system can autonomously maintain efficient and stable harmonic suppression functions by relying on historical experience and real-time learning capabilities.

[0030] like Figure 2 As shown, this embodiment also provides a UPQC adaptive harmonic suppression system based on a smart terminal to achieve the above, specifically including: Data sensing module: The intelligent terminal collects the current and voltage waveforms of multiple nodes in the medium-voltage test area in real time, and performs sequence decoupling on the current and voltage waveforms to obtain positive sequence, negative sequence and zero sequence components; Harmonic profile construction module: Performs harmonic analysis on each sequence component, statistically analyzes the content, phase and harmonic power direction of each order harmonic, and forms a harmonic profile of the transformer area including the harmonic source intensity distribution, impedance resonance risk index and interphase coupling coefficient. Optimization Decision Module: The intelligent terminal takes the harmonic profile as input, identifies the dominant harmonic order and cross-coupled harmonics under the current operating conditions, calculates the target compensation current to be injected into the UPQC parallel unit online based on the identification results, determines the weight coefficient of each sequence component, generates the target reference current command, and generates the reference voltage command for voltage mode correction of the series unit based on the voltage quality assessment results. Command execution module: The UPQC device receives the target reference current command and the reference voltage command. Its parallel unit performs selective harmonic injection and dynamic active damping, and its series unit performs voltage compensation to achieve joint suppression of dominant and cross-order harmonics. Dynamic adjustment module: The intelligent terminal continuously senses the environmental change signals in the transformer area and the switching action signals of the switching capacitors in the reactive power compensation device, and dynamically adjusts the sampling window length and suppression bandwidth.

[0031] It should be noted that the UPQC adaptive harmonic suppression system based on a smart terminal provided in this embodiment and the UPQC adaptive harmonic suppression method based on a smart terminal provided in this embodiment belong to the same concept. The specific operation methods of each module and unit have been described in detail in the method embodiment and will not be repeated here. In practical applications, the UPQC adaptive harmonic suppression system based on a smart terminal provided in the above embodiment can be assigned to different functional modules as needed, that is, the internal structure of the system can be divided into different functional modules to complete all or part of the functions described above. This is not a limitation here.

[0032] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application 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, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0033] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. 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... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0034] 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.

[0035] 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.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A smart terminal-based UPQC adaptive harmonic suppression method, characterized in that, The method comprises the following steps: The intelligent terminal real-time collects current waveforms and voltage waveforms of multiple nodes in the medium-voltage distribution area, and decouples the current waveforms and the voltage waveforms to obtain positive sequence, negative sequence and zero sequence components; Harmonic analysis is performed on each sequence component to statistically obtain the harmonic content rate, phase and harmonic power direction of each order, and a harmonic image of the distribution area is formed, which contains harmonic source intensity distribution, impedance resonance risk index and inter-phase coupling coefficient; The intelligent terminal takes the harmonic image as input to identify the dominant harmonic order and cross-coupling harmonic under the current working condition, and based on the identification result, online calculates the target compensation current to be injected by the parallel unit of the UPQC, determines the weight coefficient of each sequence component, generates the target reference current instruction, and generates the reference voltage instruction for the series unit to correct the voltage form according to the voltage quality evaluation result; The UPQC device receives the target reference current instruction and the reference voltage instruction, the parallel unit of the UPQC device performs selective harmonic injection and dynamic active damping, and the series unit of the UPQC device performs voltage compensation, thereby realizing joint suppression of the dominant order and cross-order harmonics; The intelligent terminal continuously senses the change signal of the environment of the distribution area and the switching capacitor switching action signal in the reactive power compensation device, and dynamically adjusts the sampling window length and the suppression bandwidth.

2. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 1, characterized in that, The construction method of the harmonic image comprises the following steps: Fast Fourier transform or wavelet transform is used to perform harmonic analysis on the positive sequence, negative sequence and zero sequence components to obtain the harmonic content rate and phase information of each order, and the harmonic power flow direction is determined by comparing the phase difference between the harmonic voltage and the harmonic current of different nodes; The harmonic source intensity distribution is determined by analyzing the direction of the harmonic power flow from the node to the power grid and combining the harmonic current amplitude based on the harmonic current amplitude and the harmonic power flow direction information of each node; The impedance resonance risk index is quantified by calculating the ratio of the harmonic voltage variation and the harmonic current variation based on the harmonic analysis result; The inter-phase coupling coefficient is quantified by analyzing the correlation between the amplitude and the phase of the harmonic voltage and the harmonic current of different nodes.

3. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 1, characterized in that, The construction process of the harmonic image is realized based on a dynamically updated harmonic spectrum database and a pattern recognition algorithm; The harmonic spectrum database is used to record the harmonic amplitude, phase, harmonic power flow direction and change trend over time of each node; The pattern recognition algorithm is used to analyze the data in the harmonic spectrum database to identify the dominant harmonic source type and its dynamic propagation path in the distribution area.

4. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 1, characterized in that, The calculation model of the target compensation current to be injected by the parallel unit of the UPQC simultaneously considers the downstream harmonic current suppression and the upstream background harmonic voltage isolation, and the objective function is set as the weighted sum of the current total harmonic distortion rate and the voltage total harmonic distortion rate at the point of common coupling; The weighted sum introduces an adaptive weight distribution strategy, dynamically adjusts the weight proportion of the current total harmonic distortion rate and the voltage total harmonic distortion rate in the objective function based on the inter-phase coupling coefficient and the impedance resonance risk index in the harmonic image.

5. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 1, characterized in that, The generation process of the target reference current instruction and the reference voltage instruction is decoupled in the control target and coordinated in the system-level control. The target reference current instruction is generated to mainly suppress the common connection point harmonic current and balance the three-phase current, and an impedance resonance risk index is introduced as a damping constraint; The reference voltage instruction is generated to mainly maintain the common connection point voltage stability and eliminate specific harmonic voltage, and the power exchange balance between the series unit and the parallel unit is considered.

6. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 1, characterized in that, The dynamic active damping is realized by introducing a virtual negative resistance feedback link corresponding to the resonance frequency point in the control algorithm of the parallel unit, and the resistance value of the virtual negative resistance is adaptively adjusted according to the impedance resonance risk index in the harmonic image.

7. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 1, characterized in that, The specific method of dynamically adjusting the sampling window and the suppression bandwidth is that when the system is in a transient process indicated by the sensed substation environment change signal or the switch capacitor switching action signal, the sampling window is automatically shortened and the suppression bandwidth is automatically expanded; When the system enters a steady state, the sampling window is automatically lengthened and the suppression bandwidth is automatically narrowed.

8. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 1, characterized in that, The intelligent terminal receives the global optimization strategy issued by the main station as a priority strategy; When it is detected that the communication with the main station is interrupted or the received strategy is seriously inconsistent with the current local harmonic image, the intelligent terminal automatically switches to a local fallback control strategy based on the local harmonic image.

9. The UPQC adaptive harmonic suppression method based on intelligent terminal according to claim 8, characterized in that, The local fallback control strategy is a predictive control mode based on historical harmonic images and real-time data: when the communication with the main station is interrupted, the intelligent terminal calls the optimal suppression strategy similar to the current working condition in the historical database as the initial strategy, and fine-tunes it in combination with the real-time harmonic image.

10. A smart terminal based UPQC adaptive harmonic suppression system for implementing the method as claimed in any one of claims 1 to 9, characterized in that, It comprises: A data sensing module: the intelligent terminal real-time samples the current waveform and voltage waveform of multiple nodes in the substation, and decouples the current waveform and voltage waveform to obtain positive sequence, negative sequence and zero sequence components; An image construction module: harmonic analysis is performed on each sequence component to statistically obtain the harmonic content rate, phase and harmonic power direction, forming a substation harmonic image containing harmonic source intensity distribution, impedance resonance risk index and inter-phase coupling coefficient; An optimization decision module: the intelligent terminal takes the harmonic image as input, identifies the dominant harmonic order and cross-coupling harmonic under the current working condition, calculates the target compensation current to be injected by the UPQC parallel unit based on the identification result, determines the weight coefficient of each sequence component, generates the target reference current instruction, and generates the reference voltage instruction for the series unit to perform voltage shape correction according to the voltage quality evaluation result; An instruction execution module: the UPQC device receives the target reference current instruction and the reference voltage instruction, the parallel unit of which executes selective harmonic injection and dynamic active damping, and the series unit cooperates to execute voltage compensation, realizing the joint suppression of the dominant order and cross-order harmonics; A dynamic adjustment module: the intelligent terminal continuously senses the substation environment change signal and the switching action signal of the switch capacitor in the reactive power compensation device, and dynamically adjusts the sampling window length and the suppression bandwidth.

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