A power distribution network multi-type adjustable resource in-situ collaborative harmonic suppression method and system

Abstract

The present application provides a kind of power distribution network multi-type adjustable resource in situ collaborative harmonic suppression method and system, it is related to power electronics and power quality technical field, the present application is to each adjustable resource of harmonic overproof grid connection point association and is judged to carry out management function, determine the adjustable resource set with harmonic management function;The actual capacity range of each adjustable resource participating in harmonic management is measured;With the target that grid connection point harmonic distortion rate reaches standard, in combination with the actual capacity range and operating constraint of each adjustable resource, harmonic compensation capacity is optimally distributed, and the harmonic compensation capacity instruction of each adjustable resource is generated;Harmonic compensation current is output through internal power loop control architecture, and grid connection point harmonic distortion rate is monitored in real time.The present application can fully tap the harmonic suppression potential of power distribution network source network load side multi-type adjustable resource, realize the accurate measurement and optimal distribution of harmonic compensation capacity, effectively reduce harmonic management cost, and improve power quality of power distribution network.

Description

Technical Field

[0001] This invention relates to the fields of power electronics and power quality technology, and in particular to a method and system for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network. Background Technology

[0002] With the construction of a new power system aimed at achieving "dual carbon" goals, the distribution network, as a key link in energy consumption and supply-demand interaction, is rapidly developing towards a "dual high" direction: high proportion of renewable energy integration and high penetration of power electronic equipment. Building an efficient, economical, and reliable power quality governance system for the distribution network has become a core strategic requirement for promoting energy transformation and high-quality industrial development. The installed capacity of distributed photovoltaic, wind power, and other renewable energy sources on the distribution network side in my country continues to climb. Power electronic loads and distributed power sources have become core components of the distribution network. Harmonic pollution, as one of the most prominent power quality problems in the distribution network, is experiencing increasingly severe distortion rate exceedances with the large-scale integration of power electronic equipment. Statistics show that over 80% of harmonic interference in power distribution networks originates from the nonlinear characteristics of power electronic devices. The harmonic distortion rate in industrial clusters and new energy grid-connected areas exceeds the standard by more than 40%. This not only leads to overheating and reduced lifespan of equipment such as distribution transformers and instrument transformers, but also severely restricts the efficient absorption of renewable energy. It causes equipment failures and a decline in product yield in industries such as precision manufacturing and high-end electronics. The economic losses caused by harmonic problems in power distribution networks exceed 100 billion yuan annually nationwide. Harmonic suppression has become a top priority in the governance of power quality in power distribution networks.

[0003] To address the harmonic mitigation needs of power distribution networks, domestic and international research and engineering applications still primarily rely on installing dedicated harmonic mitigation equipment as the core solution. This involves deploying active power filters (APFs), passive power filters (PFs), and hybrid power filters (HPFs) at nodes with severe harmonic pollution to achieve localized harmonic suppression. International companies like Siemens and ABB have developed high-precision digital active harmonic mitigation equipment based on advanced power electronic control technology, enabling accurate compensation for specific frequency harmonics. However, this equipment is expensive, requires a large footprint, and is only suitable for harmonic mitigation needs under fixed operating conditions. Domestic research institutions and enterprises, on the other hand, focus on optimizing the performance of dedicated equipment. They improve the response speed and compensation accuracy of filters through topology improvements and control algorithm upgrades. Some studies have proposed a hybrid "active + passive" mitigation scheme, achieving a certain balance between cost and mitigation effectiveness. However, existing dedicated harmonic mitigation equipment generally suffers from prominent problems such as limited functionality, poor adaptability to operating conditions, and low equipment utilization. A single piece of equipment can only mitigate harmonics in a specific frequency band and amplitude, making it difficult to adapt to the dynamic operating conditions of fluctuating distribution network loads and random renewable energy output. At the same time, dedicated equipment is mostly a fixed mitigation solution deployed at specific locations. Faced with the multi-node and decentralized harmonic pollution characteristics of the distribution network, large-scale installations are required to achieve full-area mitigation. This not only significantly increases the construction and operation and maintenance costs of the power grid, but also easily leads to long-term equipment idleness, forming a vicious cycle of "high mitigation costs and poor overall results".

[0004] Compared to the large-scale addition of dedicated harmonic mitigation equipment, the diverse and widely distributed adjustable resources on the power generation, grid, and load sides of the distribution network have become high-quality distributed power electronic resources with harmonic suppression potential. Adjustable resources such as distributed photovoltaic inverters and wind turbine converters on the power generation side, SVG and distribution grid converters on the grid side, and charging pile converters and industrial frequency converters on the load side all possess the technical characteristics of power electronic conversion and rapid power regulation. Harmonic current detection and compensation can be achieved through software reconfiguration and control strategy optimization, participating in harmonic suppression without additional hardware investment. This is a crucial approach to achieving low-cost harmonic mitigation in the distribution network. Therefore, fully exploring the harmonic suppression potential of the diverse adjustable resources in the distribution network and promoting their synergistic cooperation with traditional dedicated mitigation equipment has become the core path to solving the current pain points in harmonic mitigation in the distribution network.

[0005] However, at present, the participation of various types of adjustable resources in the distribution network in harmonic suppression still faces many key technical bottlenecks: First, the equipment topology, rated parameters, and control characteristics of adjustable resources on the source / grid / load sides vary significantly, and are affected by factors such as random power output from new energy sources, dynamic changes in load conditions, and strict grid connection constraints, making it difficult to accurately assess and tap their actual adjustability and harmonic suppression potential; Second, existing research mostly focuses on the harmonic suppression application of single types of resources, and has not yet formed a mature method for on-site coordinated suppression of multiple types of adjustable resources, lacking a comprehensive coordinated governance strategy for distributed harmonic pollution in the distribution network, making it difficult to achieve optimal allocation of resource control capabilities; Third, harmonic suppression of adjustable resources needs to take into account their original main functions (such as power supply, charging, and reactive power regulation). How to achieve reasonable allocation of suppression capacity and on-site coordinated control while ensuring the normal operation of the main functions of resources remains a key unsolved problem.

[0006] In summary, against the backdrop of increasingly prominent "high-voltage and high-efficiency" characteristics of distribution networks and increasingly severe harmonic pollution problems, breakthroughs in the suppression potential tapping and local collaborative control technologies of various types of adjustable resources in distribution networks, replacing and supplementing traditional dedicated harmonic control equipment, and achieving low-cost, efficient, and comprehensive harmonic control of distribution networks have become an urgent need for the development of distribution networks in the construction of new power systems. Summary of the Invention

[0007] One objective of this invention is to disclose a method for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network. By determining the governance function of adjustable resources associated with the grid connection point where harmonics exceed the standard, calculating the suppression capacity range, optimizing the allocation of compensation capacity, and controlling the current precisely, this method achieves efficient local coordinated suppression of harmonics at the grid connection point of the distribution network. It fully taps the harmonic governance potential of adjustable resources on the source, grid, and load sides, and solves the problems of high governance costs and low utilization rates of traditional dedicated equipment.

[0008] Another objective of this invention is to propose a local coordinated harmonic suppression system for multiple types of adjustable resources in a power distribution network.

[0009] To achieve the above objectives, a first aspect of the present invention proposes a method for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network, comprising:

[0010] S1, determine the governance function of each adjustable resource associated with the harmonic exceeding the grid connection point, and determine the set of adjustable resources with harmonic governance function; S2, based on the rated capacity, current operating status and hardware limitation parameters of each adjustable resource in the adjustable resource set, calculate the actual capacity range of each adjustable resource participating in harmonic governance; S3 aims to achieve the target harmonic distortion rate at the grid connection point. It optimizes the allocation of harmonic compensation capacity based on the actual capacity range and operational constraints of each adjustable resource and generates harmonic compensation capacity instructions for each adjustable resource. S4, each adjustable resource outputs harmonic compensation current through the internal power loop control architecture according to the harmonic compensation capacity instruction, and monitors the harmonic distortion rate at the grid connection point in real time. If the standard is not met, it returns to step S3 to redistribute the compensation capacity until the standard is met.

[0011] In one embodiment of the present invention, the step of determining the harmonic mitigation function of each adjustable resource associated with the harmonic-exceeding grid connection point, and identifying the set of adjustable resources with harmonic mitigation function, includes: Real-time monitoring of harmonic distortion rate indicators at each grid connection point in the distribution network, comparison with national power quality standards, screening out grid connection points with excessive harmonic distortion, and simultaneously acquiring basic information on all adjustable resources on the source, grid, and load sides, such as photovoltaic inverters, energy storage converters, and load-side converters connected to the grid connection point. Retrieve the factory parameters, hardware topology, and software control function modules of each adjustable resource to determine whether it has the hardware support conditions and software implementation capabilities for harmonic current detection and compensation. Based on the actual operating conditions of the distribution network, the activation of the harmonic mitigation function of each adjustable resource under the current grid connection state is verified. Resources that cannot participate in harmonic suppression due to factors such as hardware failure, software lockout, and grid connection constraints are eliminated. Finally, the set of adjustable resources with harmonic mitigation function at the grid connection point with excessive harmonics is determined.

[0012] In one embodiment of the present invention, verifying the activatability of the harmonic mitigation function of each adjustable resource under the current grid connection state includes: The comprehensive judgment logic is adopted, and the judgment and governance function can be activated only when the three conditions are met simultaneously: the equipment has no hardware failure, the software function is not locked, and the grid connection regulation constraint is met.

[0013] In one embodiment of the present invention, calculating the actual capacity range of each adjustable resource participating in harmonic mitigation based on the rated capacity, current operating status, and hardware limitation parameters of each adjustable resource in the adjustable resource set includes: Read the rated capacity and current operating status of each converter in the adjustable resource set, and calculate the active and reactive capacity required by each converter to complete special tasks such as photovoltaic grid-connected power generation, energy storage charging and discharging, and load power supply. Based on the dedicated task capacity requirements, and combined with the converter power factor, apparent capacity and other operating constraints, the upper limit of reactive power capacity of each converter participating in harmonic control is calculated, and the reactive power regulation margin that can be allocated to harmonic suppression is clarified. By retrieving the hardware limiting parameters such as current tracking accuracy, switching frequency, and rated current of power devices of each converter, and combining them with the upper limit of reactive power capacity, the ideal capacity range for each converter to participate in harmonic mitigation is determined. Considering the line impedance between adjustable resources and the grid connection point where harmonics exceed the standard, the power loss during the harmonic mitigation process is calculated, the ideal capacity range is corrected, and finally the actual output harmonic mitigation capacity range of each adjustable resource is obtained.

[0014] In one embodiment of the present invention, the step of optimizing the allocation of harmonic compensation capacity based on the target of achieving the harmonic distortion rate at the grid connection point, combined with the actual capacity range and operational constraints of each adjustable resource, and generating harmonic compensation capacity instructions for each adjustable resource includes: With the core objective of reducing the harmonic distortion rate of grid connection points exceeding harmonic standards to within the national standard range, while also taking into account the highest utilization rate and most balanced allocation of harmonic governance capacity of each adjustable resource, a multi-objective harmonic compensation capacity optimization allocation model is constructed. The harmonic control capacity range of each adjustable resource, the capacity constraint of dedicated tasks, and the grid-connected operation limit are used as constraints of the optimization model to determine the variable boundaries and solution range of the model. An improved multi-objective optimization algorithm was used to solve the model, and the optimal allocation value of harmonic compensation capacity of each converter in the set of adjustable resources associated with the harmonic exceedance grid connection point was obtained. Based on the optimal allocation value, generate harmonic compensation capacity instructions for each adjustable resource converter, and specify the specific parameters of the harmonic mitigation capacity that each converter needs to output.

[0015] In one embodiment of the present invention, solving the model using an improved multi-objective optimization algorithm includes: An improved NSGA-Ⅲ multi-objective optimization algorithm is adopted. The optimization objectives, constraints and capacity ranges are entered into the algorithm system. After the population is initialized, the results are gradually optimized through iterative calculations and screening comparisons until the calculation results tend to be stable. Finally, the optimal allocation scheme that meets all objectives and constraints is selected.

[0016] In one embodiment of the present invention, the adjustable resources output harmonic compensation current through the internal power loop control architecture according to the harmonic compensation capacity command, including: Each adjustable resource converter receives a harmonic compensation capacity command and, through its internal harmonic detection module, collects the harmonic current signal at the grid connection point in real time. Combined with the compensation capacity command, it calculates the harmonic mitigation reference current. The calculated harmonic mitigation reference current includes: using the real-time measured harmonic current at the grid connection point as the base value, multiplying it by a harmonic compensation correction coefficient adapted to the grid operating conditions, and then dynamically correcting it by combining the ratio of the current allocated compensation capacity of a single device to the maximum compensation capacity of the device. The converter starts its internal power loop control architecture, takes the harmonic mitigation reference current as a given value, and uses composite control algorithms such as proportional-integral and repetitive control to adjust the converter output current in real time. Based on the power loop control results, the power devices of the drive converter are switched on and off, and each converter is controlled to accurately output harmonic compensation current, thereby achieving local harmonic suppression of each adjustable resource.

[0017] In one embodiment of the present invention, the real-time adjustment of the converter output current using a composite control algorithm such as proportional-integral and repetitive control includes: A PI plus repetitive composite control algorithm is adopted. The PI control is responsible for quickly responding to sudden changes in grid current and suppressing dynamic deviations, while the repetitive control accurately tracks periodic harmonic disturbances based on the periodic characteristics of grid harmonics and eliminates steady-state harmonic errors. The output regulation voltage of the composite control strategy is composed of the superposition of the output voltage components of the PI controller and the output voltage components of the repetitive controller.

[0018] In one embodiment of the present invention, the real-time monitoring of the harmonic distortion rate at the grid connection point, and if it fails to meet the standard, returning to step S3 to reallocate the compensation capacity until the standard is met, includes: The total harmonic distortion rate at the grid connection point is collected in real time and continuously by the power quality monitoring unit. Based on the national standard, if the indicator meets the national standard after treatment, the current compensation capacity and control strategy are maintained; if it does not meet the standard, the closed-loop correction mechanism is triggered, returning to the harmonic compensation capacity optimization and allocation step, resolving and issuing compensation capacity instructions until the harmonic distortion rate at the grid connection point meets the standard.

[0019] The local coordinated harmonic suppression method for multiple types of adjustable resources in the distribution network according to the present invention can fully tap the harmonic suppression potential of multiple types of adjustable resources on the source, grid and load sides of the distribution network, realize efficient local coordinated harmonic control, reduce harmonic control costs and improve power quality.

[0020] Another objective of this invention is to propose a local coordinated harmonic suppression system for multiple types of adjustable resources in a distribution network, comprising: The function determination module is used to determine the governance function of each adjustable resource associated with the harmonic exceeding the grid connection point, and to determine the set of adjustable resources with harmonic governance function. The capacity calculation module is used to calculate the actual capacity range of each adjustable resource participating in harmonic mitigation based on the rated capacity, current operating status and hardware limitation parameters of each adjustable resource in the adjustable resource set. The optimization allocation module is used to optimize the allocation of harmonic compensation capacity based on the actual capacity range and operational constraints of each adjustable resource, with the goal of achieving the harmonic distortion rate at the grid connection point. It generates harmonic compensation capacity instructions for each adjustable resource. The power control module is used by each adjustable resource to output harmonic compensation current through the internal power loop control architecture according to the harmonic compensation capacity command, and to monitor the harmonic distortion rate at the grid connection point in real time. If the standard is not met, the module will return to reallocate the compensation capacity until the standard is met.

[0021] The local coordinated harmonic suppression system for multiple types of adjustable resources in the distribution network according to the present invention can fully tap the harmonic suppression potential of multiple types of adjustable resources on the source, grid and load sides of the distribution network, realize efficient local coordinated harmonic control, reduce harmonic control costs and improve power quality.

[0022] The beneficial effects of this invention are as follows: This invention accurately determines the harmonic suppression capabilities of adjustable resources associated with grid connection points that exceed harmonic limits, thus identifying the main resource entities with harmonic suppression capabilities on the power source, grid, and load sides of the distribution network. Compared to the traditional model that relies solely on dedicated control equipment, this invention broadens the scope of harmonic control resources and fully taps the control potential of existing power electronic devices in the distribution network.

[0023] This invention takes into account both the capacity requirements of adjustable resources for dedicated tasks and the limitations of the hardware itself. By combining line power loss correction, it achieves accurate calculation of the harmonic control capacity range of each adjustable resource, effectively solving the problem of difficulty in quantifying suppression capacity due to different equipment characteristics and complex operating conditions, and providing a scientific basis for subsequent capacity allocation.

[0024] This invention constructs a multi-objective optimization model and uses an improved algorithm to solve it, achieving the optimal allocation of harmonic compensation capacity for multiple types of adjustable resources. This not only ensures the harmonic control effect at the grid connection point but also improves the capacity utilization rate of each resource, avoiding the over-allocation of a single resource from affecting its dedicated task execution, and achieving global optimization of local collaborative suppression.

[0025] This invention achieves precise output of harmonic compensation current through the power loop control architecture inside the converter. Combined with closed-loop feedback adjustment of the harmonic state at the grid connection point, it ensures the real-time performance and accuracy of harmonic suppression, effectively suppresses harmonic pollution at the grid connection point of the distribution network, improves the power quality of the distribution network, and eliminates the need for large-scale addition of dedicated treatment equipment, thus significantly reducing the economic and maintenance costs of harmonic treatment.

[0026] This invention is adapted to the operating characteristics of distribution networks with high proportion of renewable energy access and high power electronics. It can be flexibly applied to harmonic control at the grid connection point of distribution networks of different scales and operating conditions. It has good scalability and engineering applicability, and provides a new technical path for low-cost and efficient power quality control of distribution networks, thus contributing to the construction of new power systems.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1This is a flowchart illustrating a method for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network, provided in an embodiment of the present invention. Figure 2 This is an overall flowchart of the method for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network provided in an embodiment of the present invention; Figure 3 A flowchart illustrating the method for determining the adjustable resource management function associated with the grid connection point for excessive harmonics in a distribution network, as provided in this embodiment of the invention. Figure 4 A flowchart illustrating the method for calculating the range of adjustable resource harmonic mitigation capacity in a distribution network, as provided in this embodiment of the invention. Figure 5 This is a diagram illustrating the harmonic mitigation capacity characteristic of a power distribution network adjustable resource converter, provided in an embodiment of the present invention. Figure 6 The diagram shows the construction and solution architecture of the harmonic compensation capacity optimization allocation model for multiple types of adjustable resources in the distribution network provided in this embodiment of the invention. Figure 7 A flowchart illustrating the precise control method for harmonic compensation current of adjustable resource converter in distribution network provided in this embodiment of the invention; Figure 8 This is a diagram of the internal power loop harmonic compensation control architecture of an adjustable resource converter provided in an embodiment of the present invention. Figure 9 This is a schematic diagram illustrating the application effect of local coordinated harmonic suppression of multiple types of adjustable resources in the distribution network provided in an embodiment of the present invention. Figure 10 This is a structural diagram of a local coordinated harmonic suppression system for multiple types of adjustable resources in a power distribution network, provided in an embodiment of the present invention. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] The following description, with reference to the accompanying drawings, describes a method and system for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network, according to an embodiment of the present invention.

[0032] Example 1 This embodiment provides a method for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network. For example... Figure 1 As shown, it includes: S1, determine the governance function of each adjustable resource associated with the harmonic exceeding the grid connection point, and identify the set of adjustable resources with harmonic governance function.

[0033] Specifically, the governance function of each adjustable resource associated with a grid connection point exceeding harmonic standards is determined. This aims to accurately identify resource entities with harmonic current detection and compensation capabilities from the widely distributed power electronic devices on the power source, grid, and load sides of the distribution network, laying a reliable and controllable foundation for subsequent collaborative governance. The determination process first filters out grid connection points with excessive harmonic indicators based on real-time monitoring results of the harmonic distortion rate at the grid connection point, and simultaneously obtains basic information on all adjustable resources connected to that grid connection point, including equipment type, rated parameters, and current operating status.

[0034] Based on this, the hardware topology and software control functions of each adjustable resource are further verified to determine whether they possess the physical conditions and control capabilities required for harmonic mitigation. At the hardware level, it needs to be confirmed whether the power conversion circuit supports rapid tracking and compensation output of harmonic currents. At the software level, it needs to be confirmed whether functional modules such as harmonic detection, calculation, and command generation are configured. Assuming both hardware and software conditions are met, the activation capability of the harmonic mitigation function of each adjustable resource under the current grid connection state needs to be verified in conjunction with the actual operating conditions of the distribution network. Resources that cannot be used for mitigation due to hardware failure, software locking, or grid connection constraints are eliminated, ultimately determining the set of adjustable resources with harmonic mitigation capabilities at the grid connection point where harmonics exceed the standard.

[0035] As one implementation method, the determination process can be carried out in a three-level process of monitoring and determination, hardware and software verification, and operational activation verification. By verifying the hardware support conditions, software function configuration and current operating status of each adjustable resource item by item, it is ensured that the determined set of adjustable resources is real and effective and can be directly used for subsequent harmonic governance scheduling.

[0036] This step, through a systematic functional determination process, clarifies the resource entities in the distribution network that have harmonic suppression capabilities, effectively avoiding governance blind spots or ineffective scheduling caused by unclear resource capabilities. It provides a reliable and controllable equipment object basis for the accurate calculation and optimized allocation of subsequent harmonic governance capacity, thereby ensuring the pertinence and effectiveness of the harmonic collaborative governance strategy.

[0037] Furthermore, this embodiment provides a detailed description of the specific implementation of step S1 in the method for on-site coordinated harmonic suppression of multiple types of adjustable resources in a distribution network, which determines the governance function of each adjustable resource associated with the grid connection point where harmonics exceed the standard, and identifies the set of adjustable resources with harmonic governance functions.

[0038] In this embodiment, the governance function of each adjustable resource associated with the harmonic exceeding the grid connection point is determined to identify the set of adjustable resources with harmonic governance function, which is specifically implemented through a three-level process.

[0039] First, the three-phase voltage waveforms are collected in real time by the online power quality monitoring device installed at the grid connection point. A harmonic analysis algorithm is used to decompose the signal, obtaining the fundamental voltage and each harmonic voltage component. The total harmonic distortion (THD) is then calculated, and the calculated distortion value is compared with the national power quality standards to identify grid connection points that exceed the harmonic standards. Simultaneously with the standard determination, the system acquires basic information on all adjustable resources on the grid-connected side, including photovoltaic inverters, energy storage converters, and load-side converters, through communication acquisition, ledger reading, and status monitoring. This information includes equipment factory parameters, hardware topology, current grid-connected operating status, control software version, and function enablement status, forming a complete equipment information database.

[0040] Secondly, the factory parameters, hardware topology, and software control function modules of each adjustable resource are retrieved to determine whether they possess the hardware support and software implementation capabilities for harmonic current detection and compensation. Hardware assessment primarily verifies whether the power conversion circuit supports harmonic current detection, tracking, and compensation output; for example, it checks whether a PWM rectifier bridge topology is used and whether it has fast current loop control capabilities. Software assessment primarily verifies whether harmonic detection, harmonic calculation, compensation command generation, and closed-loop regulation function modules are configured. Based on the combined hardware and software assessment results, equipment that simultaneously meets both hardware support and software function requirements is selected.

[0041] Finally, based on the actual operating conditions of the distribution network, the activatability of harmonic mitigation functions of each adjustable resource under the current grid connection status was verified. This verification employed a comprehensive judgment logic, determining that the mitigation function could be activated only when all three conditions were simultaneously met: no hardware faults in the equipment, no locked software functions, and grid connection control constraints. Specifically, each item was checked for hardware faults, module anomalies, or protection actions; whether harmonic mitigation-related functions were locked by software, restricted by permissions, or manually disabled; and whether the voltage, frequency, and power flow at the current grid connection point were within the normal range and without grid dispatch constraints or grid connection restrictions preventing the activation of the mitigation function. Through this activation verification, resources unable to participate in harmonic suppression due to hardware faults, software locking, or grid connection constraints were eliminated, ultimately determining the set of adjustable resources with harmonic mitigation functions at the grid connection point exceeding harmonic limits. This provides clear, reliable, and directly controllable equipment for subsequent multi-device collaborative harmonic mitigation.

[0042] This specific implementation method achieves precise screening of adjustable resource governance functions through a three-level judgment process, ensuring that all resources included in the collaborative suppression system have practically usable harmonic governance capabilities. This avoids governance failure or scheduling chaos caused by equipment unavailability, provides a reliable data foundation for subsequent capacity calculation and optimized allocation, and improves the execution efficiency and reliability of the harmonic suppression strategy.

[0043] S2, based on the rated capacity, current operating status and hardware limitation parameters of each adjustable resource in the adjustable resource set, calculate the actual capacity range of each adjustable resource participating in harmonic mitigation.

[0044] Specifically, based on the rated capacity, current operating status, and hardware limitation parameters of each adjustable resource in the adjustable resource set, the actual capacity range of each adjustable resource participating in harmonic mitigation is calculated. Specifically, the rated capacity of each adjustable resource and the active and reactive power capacity required to perform dedicated tasks such as power generation, energy storage, and charging under the current grid connection conditions are first obtained, thereby determining the remaining capacity base available for harmonic mitigation.

[0045] Based on this, and considering grid-connected operation constraints such as the power factor and apparent capacity of each adjustable resource, the upper limit of its reactive power capacity for harmonic mitigation is calculated to define its maximum adjustable capacity without affecting the normal operation of the main functions. Further, hardware limiting parameters such as current tracking accuracy, switching frequency, and rated current of power devices for each adjustable resource are retrieved, and combined with the aforementioned upper limit of reactive power capacity, the range of harmonic mitigation capacity that each adjustable resource can output under ideal operating conditions is determined. Finally, considering the line impedance parameters between each adjustable resource and the grid connection point where harmonics exceed the standard, the power loss during the harmonic mitigation process is calculated, and the ideal capacity range is corrected to obtain the actual output harmonic mitigation capacity range of each adjustable resource. As one implementation method, the rated capacity and current active power output of each converter can be read first to calculate the capacity required for its dedicated task. Then, the upper limit of reactive power capacity is calculated based on power factor constraints. Subsequently, the ideal capacity range is determined by combining hardware limitations such as current tracking accuracy and switching frequency. Finally, the power loss caused by line impedance is taken into account for correction to obtain the actual capacity range.

[0046] This step, by comprehensively considering the rated parameters, real-time operating status, hardware performance limitations, and line transmission losses of adjustable resources, achieves accurate quantification of the harmonic mitigation capacity of each adjustable resource. This provides a scientific and reliable data foundation for the subsequent optimized allocation of harmonic compensation capacity, effectively avoiding overcompensation or undercompensation problems caused by inaccurate capacity estimation, and ensuring the feasibility and economy of harmonic mitigation.

[0047] Furthermore, this embodiment provides a detailed description of the specific implementation of step S2 in the method for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network, which calculates the actual capacity range of each adjustable resource participating in harmonic control based on the rated capacity, current operating status, and hardware limitation parameters of each adjustable resource in the set of adjustable resources.

[0048] In this embodiment, step S2 calculates the actual capacity range of each adjustable resource participating in harmonic mitigation based on its rated capacity, current operating status, and hardware limitation parameters. This is achieved through the following specific sub-steps: First, the rated capacity and current operating status of each converter in the adjustable resource set are read through the monitoring platform. The active and reactive power capacities required for each converter to complete dedicated tasks such as photovoltaic grid-connected power generation, energy storage charging and discharging, and load power supply are calculated, forming the basic dataset for capacity calculation. For example, the current active power output of the photovoltaic inverter is 40kW, the current charging and discharging active power of the energy storage converter is 30kW, and the current charging active power of the charging converter is 25kW. These data are used as the capacity occupied by dedicated tasks to be deducted in subsequent calculations. Second, based on the capacity requirements of dedicated tasks and combined with the converter power factor, apparent capacity, and other operating constraints, the upper limit of reactive power capacity for each converter participating in harmonic mitigation is calculated, clarifying the reactive power adjustment margin that can be allocated to harmonic suppression. Specifically, a simplified engineering calculation formula is used with a power factor cosφ=0.95 as a constraint. Calculate the upper limit of reactive power capacity available for harmonic mitigation for each converter, where The current active power output of the converter is used as an example. For instance, the upper limit of reactive power capacity for a single photovoltaic inverter is approximately 40 × 0.3287 ± 14.8 kVar, for an energy storage converter it is approximately 30 × 0.3287 ± 36.9 kVar, and for a single charging converter it is approximately 25 × 0.3287 ± 17.9 kVar. For dedicated harmonic mitigation equipment such as APF and SVG, the rated value or remaining capacity is directly taken. Then, the hardware limiting parameters such as current tracking accuracy, switching frequency, and rated current of power devices for each converter are retrieved. Combined with the upper limit of reactive power capacity, the ideal capacity range for each converter to participate in harmonic mitigation is determined. For example, under the conditions of 5% current tracking accuracy and 10kHz switching frequency, the ideal mitigation capacity for photovoltaic inverters, energy storage converters, and charging converters are 12~14kW, 30~35kW, and 15~17kW, respectively. Finally, considering the line impedance between adjustable resources and the grid connection point exceeding harmonic limits, the power loss during the harmonic mitigation process is calculated, and a correction formula is used. The ideal capacity range is corrected, among which For actual harmonic mitigation capacity, For ideal harmonic mitigation capacity, To account for the power loss factor of line impedance, for example, when the line impedance Z=0.12+j0.35Ω, the power loss factor is 6%. After correction, the actual capacity range of a single photovoltaic inverter is 11.28~13.16kW, the energy storage converter is 28.2~32.9kW, and the single charging converter is 14.1~15.98kW. Finally, the actual output harmonic control capacity range of each adjustable resource is obtained, providing accurate variable boundaries for subsequent capacity optimization and allocation.

[0049] This specific implementation method achieves accurate quantification of the harmonic mitigation capacity of each adjustable resource through a progressive capacity calculation process, combined with hardware limitations and line loss correction. It effectively avoids overcompensation or undercompensation problems caused by capacity estimation deviations, and provides a reliable data foundation for the coordinated suppression of multiple types of resources.

[0050] S3 aims to achieve the target harmonic distortion rate at the grid connection point. It optimizes the allocation of harmonic compensation capacity based on the actual capacity range and operational constraints of each adjustable resource, and generates harmonic compensation capacity instructions for each adjustable resource.

[0051] Specifically, in the process of optimizing the allocation of harmonic compensation capacity, the core objective is to reduce the harmonic distortion rate of the grid connection point exceeding the harmonic standard to within the preset standard range. Simultaneously, the utilization efficiency and allocation balance of the harmonic mitigation capacity of each adjustable resource are considered, thus constructing a multi-objective optimization allocation model. This model uses the calculated actual harmonic mitigation capacity range of each adjustable resource, the active power capacity constraints required for its dedicated tasks such as power generation, energy storage, and charging, and operational limitations such as the power factor of the grid connection point as constraint boundaries, thereby clarifying the feasible value space of the harmonic compensation capacity of each adjustable resource. By solving this model using a multi-objective optimization algorithm, a set of harmonic compensation capacity allocation schemes that comprehensively optimize harmonic mitigation effect, capacity utilization, and allocation balance can be obtained while satisfying all constraints. Based on this optimal allocation scheme, harmonic compensation capacity instructions are generated and issued to each adjustable resource converter. These instructions clearly specify the specific parameters of the harmonic mitigation capacity that each adjustable resource converter must output, thus providing a clear capacity basis for the subsequent accurate output of harmonic compensation current by each adjustable resource.

[0052] As one implementation method, a multi-objective optimization model can be constructed with the goal of reducing the harmonic distortion rate at the grid connection point to the national standard limit, and conditions including the actual harmonic mitigation capacity range of each adjustable resource, the active power output constraint of the dedicated task, and the grid power factor constraint. The improved NSGA-Ⅲ multi-objective optimization algorithm is then used to solve the model, thereby obtaining the optimal allocation value of the harmonic compensation capacity of each adjustable resource converter, and generating the corresponding harmonic compensation capacity command accordingly.

[0053] This step, by constructing and solving a multi-objective optimization model, achieves the scientific allocation of harmonic compensation capacity for various types of adjustable resources. While ensuring that the harmonic control effect at the grid connection point meets the standards, it effectively improves the utilization efficiency of each adjustable resource capacity and avoids the main function execution of a single resource being affected by over-allocation. Thus, it achieves the global optimal configuration and local coordination of harmonic suppression resources.

[0054] S4, each adjustable resource outputs harmonic compensation current through the internal power loop control architecture according to the harmonic compensation capacity instruction, and monitors the harmonic distortion rate at the grid connection point in real time. If the standard is not met, it returns to step S3 to redistribute the compensation capacity until the standard is met.

[0055] Specifically, after receiving the harmonic compensation capacity instruction issued by the upper-level scheduling system, each adjustable resource activates its internal power loop control architecture to generate and output a harmonic compensation current that matches the instruction, based on the capacity constraints defined by the instruction.

[0056] Specifically, this power loop control architecture acquires harmonic current signals at the grid connection point in real time and, in conjunction with received harmonic compensation capacity commands, calculates a harmonic mitigation reference current to guide the current output. This reference current is then input as a setpoint into the current loop of the power loop control architecture. A composite control algorithm dynamically adjusts the converter's output current, ensuring that the actual output harmonic compensation current accurately tracks the reference current, thereby achieving on-site cancellation of harmonic components at the grid connection point. Simultaneously with the output harmonic compensation current, the system continuously monitors the harmonic distortion rate at the grid connection point in real time and compares the monitoring results with preset power quality standards. If the monitored harmonic distortion rate meets the standard requirements, the current compensation capacity and control strategy are maintained; if it does not meet the standard, the current compensation scheme is determined to be unable to meet the governance needs, the system automatically triggers the closed-loop correction mechanism, returns to the harmonic compensation capacity optimization and allocation step, re-solves and issues compensation capacity instructions for each adjustable resource based on the real-time grid harmonic status, and executes the above current output and monitoring process again, and so on iteratively until the harmonic distortion rate at the grid connection point meets the standard.

[0057] As one implementation method, each adjustable resource converter can have a built-in dual closed-loop power control architecture. The harmonic mitigation reference current is used as the current loop setpoint. A composite control algorithm of proportional-integral and repetitive control is used to dynamically correct the output current. The power devices are switched on and off using sinusoidal pulse width modulation technology to accurately output the harmonic compensation current. At the same time, the total harmonic distortion rate at the grid connection point is collected in real time by the power quality monitoring unit. If the standard is not met, the system will automatically return to the optimization allocation step for iterative adjustment.

[0058] This technical step, by constructing a precise harmonic compensation current output mechanism based on power loop control and a closed-loop feedback adjustment system for harmonic distortion rate, enables each adjustable resource to respond quickly and accurately to harmonic compensation commands, ensuring the real-time performance and effectiveness of harmonic suppression. At the same time, through a closed-loop iterative mechanism, it adapts to the dynamic changes in power grid operating conditions, ensuring the continuous achievement of harmonic mitigation results and avoiding mitigation failure due to fluctuations in operating conditions.

[0059] Example 2 This embodiment takes a typical 10kV grid connection point in the distribution network as the target for harmonic mitigation. The measured value of the harmonic distortion rate at this grid connection point is 8.2%, which exceeds the national standard requirement of 6% in GB / T14549-1993 "Power Quality - Harmonics in Public Power Grids". Therefore, it is determined to be a grid connection point with excessive harmonics. The grid connection point connects to various types of adjustable resources and traditional dedicated management equipment on the source, grid, and load sides, including: two 50kW photovoltaic inverters and one 100kWh energy storage converter on the source side; four 60kW electric vehicle charging converters on the load side; and one 50kVar active power filter (APF) and one 100kVar static var generator (SVG) on the traditional dedicated management equipment side. The equivalent line impedance between the grid connection point and each adjustable resource is 0.12 + j0.35Ω. The grid connection power factor constraint complies with GB / T19964—2012 "Technical Regulations for Photovoltaic Power Stations Connected to Power Systems" and GB / T36552-2018 "Technical Regulations for Energy Storage Systems Connected to Power Systems", requiring the power factor to be dynamically adjustable within the range of 0.95 leading to 0.95 lagging.

[0060] like Figure 2 As shown in the figure, the working process and principle of local coordinated harmonic suppression of multiple types of adjustable resources in the distribution network in this embodiment are as follows: Step 1: Determine the adjustable resource management function associated with the grid connection point for harmonic exceedance, such as... Figure 3 As shown, the process includes: real-time monitoring of harmonic distortion rate indicators at each grid connection point in the distribution network, comparison with national power quality standards, screening out grid connection points with excessive harmonic distortion, and simultaneously acquiring basic information on all adjustable resources on the source, grid, and load sides connected to the grid connection point, such as photovoltaic inverters, energy storage converters, and load-side converters; retrieving the factory parameters, hardware topology, and software control function modules of each adjustable resource to determine whether it has the hardware support conditions and software implementation capabilities for harmonic current detection and compensation; verifying the activation of harmonic mitigation functions of each adjustable resource under the current grid connection state in conjunction with the actual operating conditions of the distribution network, eliminating resources that cannot participate in harmonic suppression due to hardware failures, software lockouts, grid connection constraints, etc., and finally determining the set of adjustable resources with harmonic mitigation functions at grid connection points with excessive harmonic distortion.

[0061] Specifically, determining the adjustable resource management function associated with grid-connected points exceeding harmonic limits is the primary technical step in achieving coordinated harmonic management of distributed power sources, energy storage, charging facilities, and dedicated management devices. Its core task is to systematically assess all connected power electronic devices under the premise of harmonic exceeding limits at the grid-connected point, identifying which devices possess harmonic management capabilities and can be included in the control resource pool. This step is strictly implemented according to a three-level process: monitoring and assessment, hardware and software verification, and operational condition activation verification, ensuring that the assessment results are accurate, effective, and directly applicable to subsequent management and scheduling. The specific implementation process is as follows: S101, Harmonic Exceeding Standard Judgment and Comprehensive Information Collection of Associated Equipment at the Grid Connection Point: This step is the prerequisite for the entire judgment process. Its core is to confirm the harmonic exceeding standard status through measured data and to fully acquire the basic and operational information of all power electronic devices at the grid connection point, establishing a data foundation for subsequent judgments. Using the online power quality monitoring device installed at the grid connection point, three-phase voltage waveforms are collected in real time. A harmonic analysis algorithm is used to decompose the signal, obtaining the fundamental voltage and each harmonic voltage component. The total harmonic distortion (THD) of the voltage at this grid connection point is calculated to be 8.2%. According to GB / T14549 "Power Quality - Harmonics in Public Power Grids," the limit for the THD of low-voltage public power grids is 5%. Since 8.2% > 5%, the harmonic exceeding standard judgment condition is met. Therefore, this node is judged as a harmonic exceeding standard grid connection point, and the associated adjustable resource management function judgment process is automatically initiated. While determining if a device exceeds the limit, the system simultaneously acquires information on all power electronic devices at the grid connection point through communication data collection, ledger reading, and status monitoring. This information includes three main categories: equipment factory parameters, hardware topology, and current grid-connected operating status. A total of nine devices were collected: two photovoltaic inverters, one energy storage converter, four charging converters, one APF active power filter, and one SVG static var generator. The collected data includes the device's rated capacity, main circuit topology, control software version, current operating status, fault information, and function enable status, forming a complete device information database to ensure that subsequent determinations cover all related devices, preventing omissions and misjudgments.

[0062] S102, Determining the Hardware and Software Support Conditions for Harmonic Mitigation of Related Equipment: This step is the core of the determination, aiming to confirm whether the equipment possesses the physical conditions and control capabilities for harmonic mitigation. Only equipment that simultaneously meets the requirements of hardware topology support and software function configuration has the foundation for harmonic mitigation. Hardware determination mainly verifies whether the power conversion circuit supports harmonic current detection, tracking, and compensation output. Verification shows that the photovoltaic inverter, energy storage converter, and charging converter all use a PWM rectifier bridge topology, possessing fast current loop control capabilities, enabling harmonic current detection and bidirectional compensation; the APF is a dedicated harmonic mitigation device, with its hardware topology specifically designed for harmonic compensation, and its response speed and compensation accuracy meet the mitigation requirements; the SVG has auxiliary harmonic compensation hardware support, outputting harmonic compensation components while performing reactive power regulation. All equipment meets the harmonic mitigation execution conditions at the hardware level. Software determination mainly verifies whether functional modules such as harmonic detection, harmonic calculation, compensation command generation, and closed-loop regulation are configured. The results show that the photovoltaic inverter, energy storage converter, and charging converter all integrate harmonic current detection and compensation software modules, supporting real-time tracking and suppression of characteristic subharmonics; the APF control software has harmonic mitigation as its core function and possesses a complete harmonic mitigation algorithm library; the SVG supporting software supports combined reactive power and harmonic control and can enable auxiliary harmonic compensation mode. Based on the combined hardware and software assessment results, all connected devices meet the hardware support and software functional requirements for harmonic mitigation and passed this stage of evaluation; no devices were eliminated due to lack of basic capabilities.

[0063] S103, Verification of the Activation Capability of Harmonic Governance Functions and Determination of Adjustable Resource Sets under Grid-Connected Conditions: This step is the final judgment stage. Based on the hardware and software meeting the requirements, it further verifies whether the equipment can truly be put into harmonic governance under the current grid-connected state, eliminating unavailability conditions such as faults, lockouts, and constraints. Activation capability adopts a comprehensive judgment logic. The governance function can only be activated if three conditions are simultaneously met: no hardware faults, no locked software functions, and compliance with grid-connected control constraints. The judgment logic can be simplified as: Activation Capable = No Faults ∧ Unlocked ∧ Compliance with Constraints. Verification is performed item by item according to this logic: All equipment has no hardware faults, no module abnormalities, no protection actions, and is operating normally; harmonic governance-related functions are not locked by software, not restricted by permissions, and not manually disabled, and are in a usable state; the current grid-connected point voltage, frequency, and power flow are all within the normal range, and there are no grid dispatch constraints, grid-connected restrictions, or safety interlocks preventing the governance function from being put into operation. After item-by-item verification, all 9 devices meet the activation conditions, and the governance function can be put into use at any time. Finally, after the entire process of harmonic exceedance determination (S101), hardware and software condition determination (S102), and activatability verification (S103) was executed, the set of adjustable resources with harmonic mitigation capabilities for the grid-connected point with harmonic exceedance was determined to be: 2 photovoltaic inverters, 1 energy storage converter, 4 charging converters, 1 APF, and 1 SVG. This set provides clear, reliable, and directly controllable equipment for subsequent multi-device collaborative harmonic mitigation, hierarchical allocation of mitigation capacity, and rapid harmonic compliance at the grid-connected point, and also lays the foundation for the execution of the entire harmonic collaborative mitigation strategy.

[0064] Step 2: Calculation of Adjustable Resource Harmonic Governance Capacity Range: (in conjunction with appendix) Figure 4 Capacity calculation process and appendix Figure 5 The capacity characteristic curves are used to calculate the harmonic mitigation capacity range of the aforementioned adjustable resource set. The rated capacity and current operating status of each converter in the adjustable resource set are read, and the active and reactive power capacities required for each converter to complete dedicated tasks such as photovoltaic grid-connected power generation, energy storage charging and discharging, and load power supply are calculated. Based on the capacity requirements of these dedicated tasks, and combined with operating constraints such as converter power factor and apparent capacity, the upper limit of reactive power capacity for each converter participating in harmonic mitigation is calculated, clarifying the reactive power regulation margin that can be allocated to harmonic suppression. Hardware limiting parameters such as current tracking accuracy, switching frequency, and rated current of power devices of each converter are retrieved, and combined with the upper limit of reactive power capacity, the ideal capacity range for each converter participating in harmonic mitigation is determined. Considering the line impedance between the adjustable resources and the harmonic-exceeding grid connection point, the power loss during the harmonic mitigation process is calculated, and the ideal capacity range is corrected to finally obtain the actual output harmonic mitigation capacity range of each adjustable resource. The specific steps are as follows: S201, Read the rated capacity and current operating status of the equipment, and calculate the capacity required for dedicated tasks. This step collects the rated parameters and real-time operating data of all equipment through the monitoring platform to clarify the current active and reactive power occupancy of each device, forming a basic dataset for capacity calculation. Specifically: 2 photovoltaic inverters each have a rated capacity of 50kW, and their current active power output is 40kW; 1 energy storage converter has a rated apparent capacity of 120kVA and a matching battery of 100kWh, with a current charging / discharging active power of 30kW; 4 charging converters each have a rated capacity of 60kW, and their current charging active power is 25kW; the APF has a rated capacity of 50kVar and is currently operating under no-load conditions; the SVG has a rated capacity of 100kVar and its current reactive power output is 20kVar. The above data represents the actual capacity occupied by each device for dedicated tasks such as power generation, energy storage, charging, and reactive power support. This data is not included in harmonic mitigation and must be deducted from the available capacity.

[0065] S202, based on power factor constraints, calculates the upper limit of reactive power capacity for each device. Using a power factor cosφ = 0.95 as the constraint, and based on the relationship between apparent power, active power, and reactive power, calculates the upper limit of reactive power capacity available for harmonic mitigation for each converter. Simplified engineering calculation formulas are used. Q max = P Substituting ×0.3287 into the operating data for calculation: Single photovoltaic inverter: Q max =40×0.3287≈±14.8kVar; Energy storage converter: Q max =30×0.3287≈±36.9kVar; Single charging converter: Q max =25×0.3287≈±17.9kVar; APF is a dedicated reactive power control device under no-load conditions, and its upper limit of reactive power capacity is directly taken as the rated value ±50kVar; after deducting the current output, the upper limit of the remaining reactive power capacity of SVG is ±80kVar.

[0066] S203, taking into account hardware limitations, determines the ideal harmonic mitigation capacity range based on equipment hardware performance constraints, including current tracking accuracy, switching frequency, and additional parameters. Figure 5 The capacity characteristic curve converts the upper limit of reactive power capacity into the ideal harmonic mitigation capacity. The photovoltaic inverter, energy storage converter, and charging converter have a current tracking accuracy of 5% and a switching frequency of 10kHz; the APF has a current tracking accuracy of 2%, offering even higher mitigation precision. Combining the capacity characteristic curve matching relationship, the ideal mitigation capacity under lossless conditions is obtained as follows: single photovoltaic inverter: 12~14kW; energy storage converter: 30~35kW; single charging converter: 15~17kW; APF: 45~50kW; SVG: 35~40kW.

[0067] S204, taking into account line impedance and power loss, the actual harmonic mitigation capacity range is corrected. Considering the line impedance from the equipment to the grid connection point Z=0.12+j0.35Ω, and the 6% power loss during harmonic transmission, the ideal capacity is corrected. Correction formula: Actual Ideal Ideal After unit-by-unit correction calculation, the final actual harmonic mitigation capacity range of each device is obtained: Single photovoltaic inverter: 11.28~13.16kW; Energy storage converter: 28.2~32.9kW; Single charging converter: 14.1~15.98kW; APF: 42.3~47kW; SVG: 32.9~37.6kW.

[0068] Step 3: Optimized allocation of harmonic compensation capacity for multiple types of adjustable resources. (Combined with attached...) Figure 6 The optimized allocation architecture was constructed, and a multi-objective optimization allocation model was built and solved. The core objective was to reduce the harmonic distortion rate of the grid-connected point exceeding the harmonic standard to within the national standard range, while simultaneously maximizing the utilization rate and achieving the most balanced allocation of harmonic mitigation capacity for each adjustable resource. A multi-objective harmonic compensation capacity optimization allocation model was constructed. The harmonic mitigation capacity range of each adjustable resource, dedicated task capacity constraints, and grid-connected operation limitations were used as constraints for the optimization model, determining the variable boundaries and solution range. An improved multi-objective optimization algorithm was used to solve the model, obtaining the optimal allocation value of harmonic compensation capacity for each converter in the set of adjustable resources associated with the grid-connected point exceeding the harmonic standard. Based on the optimal allocation value, harmonic compensation capacity instructions for each adjustable resource converter were generated, specifying the specific parameters of the harmonic mitigation capacity that each converter needs to output. The specific steps are as follows: S301 uses the following objectives: reducing the harmonic distortion rate at the grid connection point to below 6%, maximizing the utilization rate of each adjustable resource capacity, and achieving the most balanced capacity allocation. A multi-objective optimization model is constructed around these three core objectives. The equipment involved in the allocation includes 2 photovoltaic inverters, 1 energy storage converter, 4 charging converters, 1 APF, and 1 SVG. The first objective is harmonic control, requiring that after compensation and mitigation, the total harmonic distortion rate at the grid connection point be reduced to 6% or below, meeting power quality control requirements. The second objective is capacity utilization, calculated by dividing the total harmonic compensation capacity actually allocated to all equipment by the maximum usable total mitigation capacity of all equipment. Maximizing this utilization rate is the optimization direction. The third objective is balanced allocation, first calculating the average harmonic compensation capacity of all equipment, then combining this with the allocated capacity of each equipment to calculate the data dispersion. Smaller dispersion indicates a more balanced capacity allocation, which serves as the optimization objective. Based on the above three requirements, a multi-objective optimization model is formed that takes into account harmonic compliance, efficient utilization, and balanced allocation.

[0069] S302 uses the actual harmonic mitigation capacity range of each adjustable resource, the active power output constraint of dedicated tasks, and the grid-connected power factor constraint as model constraints. It determines the variable boundaries by combining equipment operating characteristics and grid operating rules, defining the value range and operational limitations of capacity allocation, and clarifying the model solution boundaries. First, there is the equipment mitigation capacity range constraint: the final harmonic compensation capacity allocated to a single device must be within the actual mitigation capacity range calculated above and cannot exceed the upper or lower limits of the device's normal operating capacity. Specifically, the capacity range for a single photovoltaic inverter is 11.28~13.16kW, for an energy storage converter it is 28.2~32.9kW, for a single charging converter it is 14.1~15.98kW, for an APF it is 42.3~47kW, and for an SVG it is 32.9~37.6kW. Second, there is the dedicated task active power output constraint: all equipment must prioritize its original core operations such as power generation, energy storage, and charging; the harmonic compensation function must not change the current active power output of the equipment. Third, there is the grid-connected power factor constraint: after all equipment operates in tandem, the power factor of the entire grid connection point must not be lower than 0.95. These three conditions together constitute the model constraints, limiting the effective range of harmonic compensation capacity for each device.

[0070] S303 employs an improved NSGA-Ⅲ multi-objective optimization algorithm to solve the model, obtaining the optimal allocation values ​​for harmonic compensation capacity of each adjustable resource. The improved NSGA-Ⅲ multi-objective optimization algorithm is used to calculate and solve the completed model. First, the optimization objectives, constraints, and capacity value ranges are entered into the algorithm system. After population initialization, the results are gradually optimized through iterative calculations and comparisons until the calculation results tend to stabilize. Finally, the optimal allocation scheme that meets all objectives and constraints is selected. The specific allocation results are as follows: 2 photovoltaic inverters are each allocated 12kW of harmonic compensation capacity, totaling 24kW; the energy storage converter is allocated 30kW; 4 charging converters are each allocated 15kW, totaling 60kW; the APF is allocated 45kW; and the SVG is allocated 35kW. All allocation values ​​are within the allowable capacity range of the equipment and simultaneously meet all operational constraints.

[0071] S304: Based on the optimal allocation values, harmonic compensation capacity instructions are generated and issued to each adjustable resource converter. The required harmonic mitigation capacity parameters for each device are clearly defined. Based on the optimal capacity allocation results obtained in the previous step, standardized harmonic compensation control instructions are uniformly compiled. These instructions are remotely sent to each adjustable device via the power grid dispatch communication system and on-site monitoring and control devices. The instructions clearly indicate the required harmonic mitigation capacity parameters for each device. After receiving the instructions, the devices automatically complete parameter configuration and operational status adjustment, and perform harmonic compensation work according to the specified capacity. With multiple devices operating collaboratively, the harmonic distortion rate at the grid connection point can be controlled below 6%, successfully completing this harmonic mitigation task.

[0072] Step 4: Precise control and closed-loop feedback of harmonic compensation current for adjustable resource converters. (Combined with attached...) Figure 7 Control process and attachment Figure 8 The power loop control architecture achieves precise output of compensation current and closed-loop regulation of harmonic mitigation: Each adjustable resource converter receives the harmonic compensation capacity command, and through its internal harmonic detection module, it collects the harmonic current signal at the grid connection point in real time. Combined with the compensation capacity command, it calculates the harmonic mitigation reference current. The converter activates its internal power loop control architecture, using the harmonic mitigation reference current as a setpoint, and adjusts the converter output current in real time through composite control algorithms such as proportional-integral and repetitive control. Based on the power loop control results, it drives the switching of the converter's power devices, controlling each converter to precisely output the harmonic compensation current, achieving local harmonic suppression for each adjustable resource. It monitors the harmonic distortion rate at the grid connection point exceeding the harmonic standard in real time. If the mitigation indicators meet national standards, the current compensation capacity and control strategy are maintained; if not, it returns to the harmonic compensation capacity optimization allocation step, re-solves and reissues the compensation capacity command until the harmonic distortion rate at the grid connection point meets the standard. The specific steps are as follows: S401, Command Reception, Harmonic Signal Acquisition, and Harmonic Mitigation Reference Current Calculation: Each adjustable resource converter terminal receives the global harmonic compensation capacity command issued by the upper-level dispatch center in real time, clarifying the maximum available harmonic compensation capacity limit for a single device, providing capacity constraints for subsequent accurate calculations. Simultaneously, the converter's built-in high-precision harmonic detection module acquires real-time load current, grid fundamental current, and various harmonic current signals at a fixed sampling frequency at the grid connection point, performing signal filtering, noise reduction, and analog-to-digital conversion preprocessing to eliminate interference noise during the acquisition process and ensure the accuracy of the sampled data.

[0073] By combining the allocated compensation capacity of the equipment with the real-time collected harmonic current data at the grid connection point, a reference current for harmonic mitigation is calculated and used as the target value for subsequent closed-loop control. The specific calculation logic is as follows: the real-time measured harmonic current at the grid connection point is used as the base value, multiplied by a harmonic compensation correction coefficient adapted to the grid operating conditions, and then dynamically corrected by combining the ratio of the currently allocated compensation capacity of a single device to its maximum compensation capacity. The harmonic compensation correction coefficient ranges from 0.95 to 1.05, adapting to minor fluctuations in grid operating conditions. This calculation method can accurately match the on-site harmonic compensation requirements based on the capacity margin of each device, effectively avoiding overcompensation or undercompensation during harmonic mitigation and ensuring the accuracy of the initial compensation command.

[0074] S402, a real-time power loop control based on PI + repetitive composite control: Each converter activates its built-in dual-closed-loop power control architecture, with the outer power loop and inner current loop as the core. The harmonic mitigation reference current calculated by S401 is used as the input value for the current loop. A PI + repetitive composite control algorithm is employed to dynamically correct the converter output current, balancing system steady-state accuracy and dynamic response speed. Specifically, PI control is responsible for quickly responding to sudden changes in grid current and suppressing dynamic deviations, solving the problem of lag in dynamic response in traditional control. Repetitive control, based on the periodic characteristics of grid harmonics, accurately tracks periodic harmonic disturbances and eliminates steady-state harmonic errors. The combination of these two technologies achieves complementary advantages.

[0075] The output voltage of this composite control strategy is composed of the superposition of the output voltage components of the PI controller and the repetitive controller. The PI controller output voltage is achieved through the coordinated operation of proportional and integral regulation: the proportional loop quickly outputs a corresponding regulating voltage based on the real-time deviation between the reference current and the actual harmonic current output by the equipment, offsetting the instantaneous current deviation; the integral loop continuously accumulates the current deviation, gradually eliminating the system's static error and ensuring steady-state control accuracy. The repetitive controller output voltage is specifically used to offset the steady-state deviation caused by periodic harmonic disturbances in the power grid. Throughout the entire process, the system compares the difference between the target reference current and the actual output current of the equipment in real time, continuously correcting the modulation voltage command through the composite control strategy to ensure that the converter output current can accurately and rapidly follow changes in the reference current.

[0076] S403, multi-device collaborative drive and graded harmonic compensation current output: The converter, based on the modulated voltage command output from the power loop control in step S402, generates drive pulse signals for power devices using SPWM (Sinusoidal Pulse Width Modulation) technology. This precisely controls the on / off times of core power devices such as IGBTs, converting DC power into AC compensation current adapted to harmonic mitigation requirements, thus achieving precise harmonic current cancellation. Combining the capacity characteristics and response speeds of various types of adjustable equipment, differentiated compensation capacity output is executed to achieve local coordinated harmonic suppression across multiple devices. Specific device output configurations are as follows: Two photovoltaic inverters each output 12kW of corresponding harmonic compensation current, leveraging the fast response characteristics of the photovoltaic grid-connected converter to undertake the task of basic harmonic compensation; an energy storage converter outputs 30kW of corresponding compensation current, utilizing the strong adjustability and fluctuation-free advantages of energy storage equipment to stably compensate for basic harmonic disturbances; four charging converters each output 15kW of corresponding compensation current, fully utilizing the idle capacity of charging equipment and realizing the resource utilization of idle resources; an APF (Active Power Filter) specifically outputs 45kW of corresponding compensation current to specifically offset high-frequency and complex subharmonics; and an SVG (Static Var Generator) outputs 35kW of corresponding compensation current, balancing harmonic control and reactive power support to optimize power quality at the grid connection point. These multiple types of equipment work together in a complementary manner to offset harmonic components at the grid connection point from multiple dimensions, achieving on-site harmonic control and preventing long-distance transmission and diffusion of harmonics.

[0077] S404, Harmonic Distortion Rate Closed-Loop Monitoring and Adaptive Strategy Correction: The system continuously collects the total harmonic distortion (THD) of the grid connection point in real time through the power quality monitoring unit, and continuously verifies the power quality indicators after treatment. The judgment is based on the national standard GB / T14549-1993 Power Quality Harmonics of Public Power Grid, which stipulates that the limit of the total harmonic distortion of voltage at the grid connection point of the public power grid is 8%.

[0078] Actual measurements show that the harmonic distortion rate at the grid connection point after treatment using this method is stable at 5.3%, which is less than the national standard limit of 8%, fully meeting the harmonic control standards for public power grids. The system determines that the current compensation capacity allocation scheme and the PI+ repetitive composite control strategy are adapted to the current power grid operating conditions, requiring no parameter adjustments. It continuously maintains the existing compensation capacity, control parameters, and output strategy, thus stably maintaining the harmonic control effect.

[0079] If the harmonic distortion rate at the grid connection point is found to be greater than 8% during real-time monitoring, failing to meet the national standard requirements, the system will immediately trigger a closed-loop correction mechanism. It will determine that there is a deviation in the current capacity allocation or control parameters, automatically return to step S401, and re-optimize the compensation capacity allocation of each device based on real-time grid harmonic data. It will fine-tune the proportional and integral parameters and repetitive control accuracy of the PI+repetitive composite control algorithm, re-drive each converter to output compensation current, iteratively optimize the treatment effect, and repeat the cycle until the harmonic distortion rate index at the grid connection point meets the national standard, thus achieving full closed-loop adaptive control of harmonic treatment.

[0080] Example 3 This embodiment uses the IEEE 33-bus distribution network system as an application scenario. This system includes three grid-connected points with harmonic distortion exceeding the standard (nodes 8, 15, and 26), with harmonic distortion rates of 7.8%, 8.5%, and 7.5%, respectively, all exceeding the national standard requirement of 6%. Each grid-connected point exceeding the standard is connected to different adjustable resources on the source, grid, and load sides according to the principle of zoning and on-site treatment. Node 8 (grid connection point 1): connects 1 80kW photovoltaic inverter, 2 60kW charging converters, and 1 60kVarAPF, with an equivalent line impedance of 0.10+j0.30Ω; Node 15 (grid connection point 2): connects 2 50kW photovoltaic inverters, 1 150kWh energy storage converter, 3 60kW charging converters, and 1 100kVarSVG, with an equivalent line impedance of 0.15+j0.40Ω. Node 26 (grid connection point 3): Connects one 100kW photovoltaic inverter, two 60kW charging converters, one 80kVarAPF, and one 80kVarSVG, with an equivalent line impedance of 0.13+j0.38Ω.

[0081] All devices are subject to grid-connected power factor constraints ranging from 0.95 leading to 0.95 lagging, with hardware limitations and power loss parameters consistent with Example 2.

[0082] The working process and principle of this embodiment are basically the same as those of embodiment 2. The core difference lies in the fact that resource assessment, capacity calculation, optimized allocation and precise control are performed on multiple grid connection points according to the principle of on-site governance by zone: For the three grid-connected points with excessive harmonics, the adjustable resource management function was determined. Based on the hardware, software and operating conditions of the connected equipment at each grid-connected point, the set of adjustable resources with harmonic management function for each zone was determined. For each zone's resource set, the actual harmonic mitigation capacity range is calculated separately. Taking into account the differences in line impedance at different grid connection points, the power loss coefficient is corrected (5% for node 8, 7% for node 15, and 6% for node 26). A multi-objective optimization allocation model is constructed for each partition, and the improved NSGA-Ⅲ algorithm is used to solve it to obtain the optimal allocation value of harmonic compensation capacity of adjustable resources in each partition, so as to avoid the increase in line loss and control delay caused by cross-partition resource allocation. Adjustable resources within each zone are controlled by the power loop in Example 2 to accurately output harmonic compensation current, thereby achieving local coordinated harmonic suppression across multiple grid connection points. Harmonic distortion rates at the three grid connection points were monitored synchronously in a closed loop. After treatment, the harmonic distortion rates at nodes 8, 15, and 26 were reduced to 5.1%, 5.4%, and 4.9%, respectively, all meeting national standards and maintaining the current control strategy for each zone.

[0083] This embodiment further verifies that the local coordinated harmonic suppression method for multiple types of adjustable resources in the distribution network of the present invention is not only applicable to harmonic management at a single grid connection point, but can also be flexibly adapted to the scenario of local coordinated management of multiple grid connection points in the distribution network, and has good scalability and engineering applicability.

[0084] Example 4 This embodiment uses the 10kV grid connection point with excessive harmonics in Embodiment 2 as the object to verify the harmonic suppression effect of adjustable resources under different reactive power control modes. The photovoltaic inverter adopts constant power factor mode (0.95), constant reactive power mode, and voltage support priority mode, respectively. The energy storage converter adopts constant current control mode and constant power factor control mode. The charging converter maintains constant power factor mode (0.95). The remaining equipment parameters, line impedance, and power loss are the same as in Embodiment 2. (See attached...) Figure 8 Experiments were conducted using schematic diagrams of different reactive power control modes.

[0085] The working process and principle of this embodiment are the same as those of embodiment 2. The core difference is that the upper limit of reactive power capacity and the actual harmonic mitigation capacity range are calculated for each adjustable resource according to different reactive power control modes. In constant reactive power mode, the photovoltaic inverter has a fixed reactive power output of 10kVar, and the remaining adjustable capacity is allocated to harmonic mitigation, increasing the actual harmonic mitigation capacity range to 13~14.5kW; in voltage support priority mode, 20% of the reactive power capacity is reserved for voltage regulation, and the actual harmonic mitigation capacity range is adjusted to 9~11kW. In constant current control mode, the current regulation margin of the energy storage converter is increased, and the actual harmonic mitigation capacity range is increased to 30~34kW; in constant power factor control mode (0.95), the actual harmonic mitigation capacity range is the same as that in Example 2, which is 28.2~32.9kW. For the capacity range under different control modes, a multi-objective optimization allocation model is reconstructed and solved, and corresponding compensation capacity commands are issued. The output compensation current is precisely controlled through the power loop. The harmonic distortion rate at the grid connection point was monitored in a closed loop. Under different control modes, the harmonic distortion rate after treatment was controlled between 4.8% and 5.6%, which met the national standard requirements.

[0086] This embodiment verifies that the method of the present invention can be adapted to various reactive power control modes of adjustable resources such as photovoltaics and energy storage. It can flexibly calculate and optimize the range of harmonic mitigation capacity according to different control modes, and achieve effective harmonic suppression while ensuring the main functions of the resources (voltage support, constant power / constant current control), further demonstrating the flexibility and adaptability of the method.

[0087] In summary, the above embodiments, from three dimensions—single grid connection point, multiple grid connection point zoning, and different reactive power control modes—verify the effectiveness, scalability, and practicality of the local coordinated harmonic suppression method for multiple types of adjustable resources in the distribution network of this invention. All of them can achieve efficient harmonic suppression at grid connection points with excessive harmonics in the distribution network, and do not require additional dedicated control equipment, thus significantly reducing harmonic control costs and fully tapping the harmonic control potential of multiple types of adjustable resources on the source, grid, and load sides.

[0088] Figure 9 A schematic diagram illustrating the application effect of local coordinated harmonic suppression of multiple types of adjustable resources in the distribution network.

[0089] The local coordinated harmonic suppression method for multiple types of adjustable resources in the distribution network according to the present invention achieves efficient local coordinated suppression of harmonics at the grid connection point by determining the governance function of adjustable resources associated with the grid connection point where harmonics exceed the standard, calculating the suppression capacity range, optimizing the allocation of compensation capacity, and controlling the current. It fully taps the harmonic governance potential of adjustable resources on the source, grid, and load sides, and solves the problems of high governance cost and low utilization rate of traditional special equipment.

[0090] To achieve the above method, the present invention also proposes a local coordinated harmonic suppression system 10 for multiple types of adjustable resources in a distribution network, such as... Figure 10 As shown, it includes: The function determination module 100 is used to determine the governance function of each adjustable resource associated with the harmonic exceeding the grid connection point, and to determine the set of adjustable resources with harmonic governance function. The capacity calculation module 200 is used to calculate the actual capacity range of each adjustable resource participating in harmonic mitigation based on the rated capacity, current operating status and hardware limitation parameters of each adjustable resource in the adjustable resource set. The optimization allocation module 300 is used to optimize the allocation of harmonic compensation capacity based on the actual capacity range and operational constraints of each adjustable resource, with the goal of achieving the harmonic distortion rate at the grid connection point. It generates harmonic compensation capacity instructions for each adjustable resource. The power control module 400 is used to output harmonic compensation current through the internal power loop control architecture according to the harmonic compensation capacity instruction of each adjustable resource, and to monitor the harmonic distortion rate at the grid connection point in real time. If the standard is not met, the module will return to reallocate the compensation capacity until the standard is met.

[0091] The local coordinated harmonic suppression system for multiple types of adjustable resources in the distribution network of this invention achieves efficient local coordinated suppression of harmonics at the grid connection point by determining the governance function of adjustable resources associated with the grid connection point where harmonics exceed the standard, calculating the suppression capacity range, optimizing the allocation of compensation capacity, and controlling the current. It fully taps the harmonic governance potential of adjustable resources on the source, grid, and load sides, and solves the problems of high governance cost and low utilization rate of traditional dedicated equipment.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0093] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present 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.

[0094] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A method for local coordinated harmonic suppression of multiple types of adjustable resources in a distribution network, characterized in that, include: S1, determine the governance function of each adjustable resource associated with the harmonic exceeding the grid connection point, and identify the set of adjustable resources with harmonic governance function; S2, based on the rated capacity, current operating status and hardware limitation parameters of each adjustable resource in the adjustable resource set, calculate the actual capacity range of each adjustable resource participating in harmonic governance; S3 aims to achieve the target harmonic distortion rate at the grid connection point. It optimizes the allocation of harmonic compensation capacity based on the actual capacity range and operational constraints of each adjustable resource and generates harmonic compensation capacity instructions for each adjustable resource. S4, each adjustable resource outputs harmonic compensation current through the internal power loop control architecture according to the harmonic compensation capacity instruction, and monitors the harmonic distortion rate at the grid connection point in real time. If the standard is not met, the process returns to step S3 to reallocate the compensation capacity until the standard is met.

2. The method as described in claim 1, characterized in that, The determination of the harmonic mitigation function of each adjustable resource associated with the grid connection point exceeding the harmonic limit, and the identification of the set of adjustable resources with harmonic mitigation function, includes: Real-time monitoring of harmonic distortion rate indicators at each grid connection point in the distribution network, comparison with national power quality standards, screening out grid connection points with excessive harmonics, and simultaneously acquiring basic information on all adjustable resources on the source, grid, and load sides, such as photovoltaic inverters, energy storage converters, and load-side converters connected to the grid connection point. Retrieve the factory parameters, hardware topology, and software control function modules of each adjustable resource to determine whether it has the hardware support conditions and software implementation capabilities for harmonic current detection and compensation. Based on the actual operating conditions of the distribution network, the activation of the harmonic mitigation function of each adjustable resource under the current grid connection state is verified. Resources that cannot participate in harmonic suppression due to factors such as hardware failure, software lockout, and grid connection constraints are eliminated, and finally the set of adjustable resources with harmonic mitigation function at the grid connection point with excessive harmonics is determined.

3. The method as described in claim 2, characterized in that, The verification of the activation capability of harmonic mitigation functions of each adjustable resource under the current grid connection state includes: The comprehensive judgment logic is adopted, and the judgment and governance function can be activated only when the three conditions are met simultaneously: the equipment has no hardware failure, the software function is not locked, and the grid connection regulation constraint is met.

4. The method as described in claim 1, characterized in that, The calculation of the actual capacity range of each adjustable resource participating in harmonic mitigation, based on the rated capacity, current operating status, and hardware limitation parameters of each adjustable resource in the adjustable resource set, includes: Read the rated capacity and current operating status of each converter in the adjustable resource set, and calculate the active and reactive capacity required by each converter to complete special tasks such as photovoltaic grid-connected power generation, energy storage charging and discharging, and load power supply. Based on the dedicated task capacity requirements, combined with the converter power factor, apparent capacity and other operating constraints, the upper limit of reactive power capacity of each converter participating in harmonic control is calculated, and the reactive power regulation margin that can be allocated to harmonic suppression is clarified. By retrieving the hardware limiting parameters such as current tracking accuracy, switching frequency, and rated current of power devices of each converter, and combining them with the upper limit of reactive power capacity, the ideal capacity range for each converter to participate in harmonic mitigation is determined. Considering the line impedance between adjustable resources and the grid connection point where harmonics exceed the standard, the power loss during the harmonic mitigation process is calculated, the ideal capacity range is corrected, and finally the actual output harmonic mitigation capacity range of each adjustable resource is obtained.

5. The method as described in claim 1, characterized in that, The process of optimizing the allocation of harmonic compensation capacity based on the target of achieving the required harmonic distortion rate at the grid connection point, combined with the actual capacity range and operational constraints of each adjustable resource, and generating harmonic compensation capacity instructions for each adjustable resource includes: With the core objective of reducing the harmonic distortion rate of grid connection points exceeding harmonic standards to within the national standard range, while also taking into account the highest utilization rate and most balanced allocation of harmonic governance capacity of each adjustable resource, a multi-objective harmonic compensation capacity optimization allocation model is constructed. The harmonic control capacity range of each adjustable resource, the capacity constraint of dedicated tasks, and the grid-connected operation limit are used as constraints of the optimization model to determine the variable boundaries and solution range of the model. An improved multi-objective optimization algorithm was used to solve the model, and the optimal allocation value of harmonic compensation capacity of each converter in the set of adjustable resources associated with the harmonic exceedance grid connection point was obtained. Based on the optimal allocation value, generate harmonic compensation capacity instructions for each adjustable resource converter, and specify the specific parameters of the harmonic mitigation capacity that each converter needs to output.

6. The method as described in claim 5, characterized in that, The method of solving the model using an improved multi-objective optimization algorithm includes: An improved NSGA-Ⅲ multi-objective optimization algorithm is adopted. The optimization objectives, constraints and capacity ranges are entered into the algorithm system. After the population is initialized, the results are gradually optimized through iterative calculations and screening comparisons until the calculation results tend to be stable. Finally, the optimal allocation scheme that meets all objectives and constraints is selected.

7. The method as described in claim 1, characterized in that, Each adjustable resource outputs harmonic compensation current through its internal power loop control architecture according to the harmonic compensation capacity command, including: Each adjustable resource converter receives a harmonic compensation capacity command and, through its internal harmonic detection module, collects the harmonic current signal at the grid connection point in real time. Combined with the compensation capacity command, it calculates the harmonic mitigation reference current. The calculated harmonic mitigation reference current includes: using the real-time measured harmonic current at the grid connection point as the base value, multiplying it by a harmonic compensation correction coefficient adapted to the grid operating conditions, and then dynamically correcting it by combining the ratio of the current allocated compensation capacity of a single device to the maximum compensation capacity of the device. The converter starts its internal power loop control architecture, takes the harmonic mitigation reference current as a given value, and uses composite control algorithms such as proportional-integral and repetitive control to adjust the converter output current in real time. Based on the power loop control results, the power devices of the drive converter are switched on and off, and each converter is controlled to accurately output harmonic compensation current, thereby achieving local harmonic suppression of each adjustable resource.

8. The method as described in claim 7, characterized in that, The real-time adjustment of the converter output current using a composite control algorithm including proportional-integral and repetitive control includes: A PI plus repetitive composite control algorithm is adopted. The PI control is responsible for quickly responding to sudden changes in grid current and suppressing dynamic deviations, while the repetitive control accurately tracks periodic harmonic disturbances based on the periodic characteristics of grid harmonics and eliminates steady-state harmonic errors. The output regulation voltage of the composite control strategy is composed of the superposition of the output voltage components of the PI controller and the output voltage components of the repetitive controller.

9. The method as described in claim 1, characterized in that, The real-time monitoring of the harmonic distortion rate at the grid connection point, if it does not meet the standard, returns to step S3 to reallocate the compensation capacity until the standard is met, including: The total harmonic distortion rate at the grid connection point is collected in real time and continuously by the power quality monitoring unit. Based on the national standard, if the indicator meets the national standard after treatment, the current compensation capacity and control strategy are maintained; if it does not meet the standard, the closed-loop correction mechanism is triggered, returning to the harmonic compensation capacity optimization and allocation step, resolving and issuing compensation capacity instructions until the harmonic distortion rate at the grid connection point meets the standard.

10. A local coordinated harmonic suppression system for multiple types of adjustable resources in a power distribution network, characterized in that, include: The function determination module is used to determine the governance function of each adjustable resource associated with the harmonic exceeding the grid connection point, and to determine the set of adjustable resources with harmonic governance function. The capacity calculation module is used to calculate the actual capacity range of each adjustable resource participating in harmonic mitigation based on the rated capacity, current operating status and hardware limitation parameters of each adjustable resource in the adjustable resource set. The optimization allocation module is used to optimize the allocation of harmonic compensation capacity based on the actual capacity range and operational constraints of each adjustable resource, with the goal of achieving the harmonic distortion rate at the grid connection point. It generates harmonic compensation capacity instructions for each adjustable resource. The power control module is used by each adjustable resource to output harmonic compensation current through the internal power loop control architecture according to the harmonic compensation capacity command, and to monitor the harmonic distortion rate at the grid connection point in real time. If the standard is not met, the module will return to reallocate the compensation capacity until the standard is met.

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