Distributed current compensation method and system for distribution networks adapted to photovoltaic converter clusters

Abstract

This invention discloses a distributed current compensation method and system for distribution networks adapted to photovoltaic converter clusters, relating to the field of distributed distribution network current compensation technology. Addressing the issues of response lag and poor safety coordination caused by the computational complexity and neglect of converter capacity limitations in traditional distribution network imbalance compensation methods, this invention decouples the unbalanced components of the three-phase electrical quantities at the transformer outlet to accurately obtain the total unbalance compensation command, thereby locking in the unbalanced components at the source. Based on the capacity coefficients of each converter, margin calculations are performed to generate unbalance compensation coefficients, further quantifying the overall compensation potential of the cluster. The total unbalance compensation command is classified and simplified according to the cluster's collaborative compensation capability to obtain the rated compensation current limit. Finally, the two are adaptively weighted and fused to generate the target compensation current command for each converter. This achieves rapid and accurate compensation of distribution network unbalanced current while ensuring the safe operation of the converters.

Description

Technical Field

[0001] This invention relates to the field of distributed distribution network current compensation technology, specifically to a distributed distribution network current compensation method and system adapted to photovoltaic converter clusters. Background Technology

[0002] With the connection of numerous three-phase unbalanced and single-phase devices to low-voltage three-phase four-wire distribution substations, negative-sequence and zero-sequence currents are generated in the lines and transformers, causing three-phase current / voltage imbalance and severely affecting power quality. Existing technologies mostly compensate for unbalanced currents by implementing load transfer, using static var compensators (SVCs), or utilizing existing converter resources. Some solutions treat the control of multiple converters as an optimization problem, relying on bidirectional data interaction, making it difficult to quickly respond to rapid fluctuations in photovoltaic converter power. Other solutions, while ensuring control accuracy, have complex control algorithms, consume significant computational resources, and do not consider converter capacity limitations, easily leading to overcurrent risks. Furthermore, existing strategies only focus on the compensation effect of a single converter, failing to coordinate multiple devices in the substation area, or their complex communication architecture cannot adapt to the needs of photovoltaic scenarios, resulting in delayed compensation response and insufficient converter operational safety, making it difficult to fully utilize the remaining converter capacity for efficient compensation while ensuring equipment safety.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] This invention aims to address the problems of response lag and poor safety coordination caused by the complexity of existing distribution network imbalance compensation methods and their neglect of converter capacity limitations. It proposes a distributed current compensation method and system adapted to photovoltaic converter clusters. The method decouples the unbalanced components of the three-phase electrical quantities at the transformer outlet to accurately obtain the total unbalance compensation command, thus locking in the unbalanced components at the source. Based on the capacity coefficients of each converter, margin calculations are performed to generate unbalance compensation coefficients, further quantifying the overall compensation potential of the cluster. The total unbalance compensation command is classified and simplified according to the cluster's collaborative compensation capability to obtain the rated compensation current limit. Finally, the two are adaptively weighted and fused to generate the target compensation current command for each converter, thereby constructing a dynamically optimized command allocation system. Under the premise of ensuring the safe operation of the converters, this method achieves rapid and accurate compensation of distribution network unbalanced current, significantly improving the system's power quality and operational robustness.

[0005] In a first aspect, one technical solution provided in this embodiment of the invention is: a distributed current compensation method for distribution networks adapted to photovoltaic converter clusters, comprising the following steps:

[0006] Step S1: Decouple the unbalanced components of the three-phase electrical quantities obtained at the transformer outlet of the distribution substation to obtain the total unbalanced current compensation command.

[0007] Step S2: Based on the capacity coefficient of each three-phase photovoltaic converter participating in the compensation, the margin of the total unbalanced current compensation command is calculated to obtain the unbalanced compensation coefficient;

[0008] Step S3: Based on the rated current and remaining capacity of the three-phase photovoltaic converter cluster, the total unbalanced current compensation command is classified and simplified to obtain the rated compensation current limit.

[0009] Step S4: Perform adaptive weighted fusion processing on the unbalanced compensation coefficient and the rated compensation current limit to obtain the target compensation current command for each photovoltaic converter.

[0010] As a preferred technical solution, the step of decoupling the unbalanced components of the three-phase electrical quantities obtained at the transformer outlet of the distribution substation to obtain the total unbalanced current compensation command includes the following steps:

[0011] Step S11: Real-time acquisition of three-phase voltage and three-phase current signals at the transformer outlet of the distribution substation;

[0012] Step S12: The three-phase voltage signal and the three-phase current signal are decomposed into components using the symmetrical component method, and the negative sequence current component and the zero sequence current component are separated.

[0013] Step S13: Based on the negative sequence current component and the zero sequence current component combined with the preset unbalance threshold, decouple to generate the initial unbalance current compensation command.

[0014] Step S14: Perform vector superposition processing on the initial unbalanced current compensation command to obtain the total unbalanced current compensation command.

[0015] As a preferred technical solution, the step of using the symmetrical component method to decompose the three-phase voltage signal and three-phase current signal into components and separate the negative-sequence current component and the zero-sequence current component includes the following steps:

[0016] Step S121: Construct the transformation matrix of the symmetrical component method, and convert the collected three-phase voltage signal and three-phase current signal into positive sequence component, negative sequence component and zero sequence component through the transformation matrix;

[0017] Step S122: Extract the negative sequence current component corresponding to the negative sequence component and the zero sequence current component corresponding to the zero sequence component respectively.

[0018] As a preferred technical solution, the step of decoupling and generating the initial unbalanced current compensation command based on the negative-sequence current component and the zero-sequence current component combined with a preset unbalance threshold includes the following steps:

[0019] Step S131: Compare the amplitudes of the negative sequence current component and the zero sequence current component with the corresponding preset negative sequence current threshold and zero sequence current threshold respectively, and determine whether to start compensation control.

[0020] Step S132: When the amplitude of any sequence current component exceeds the corresponding current threshold, compensation control is initiated, and the required negative sequence compensation current command and zero sequence compensation current command are calculated based on the degree of over-limit.

[0021] Step S133: Based on the maximum compensation current constraint, the negative sequence compensation current command and the zero sequence compensation current command are respectively subjected to amplitude limiting processing to generate the initial unbalanced current compensation command.

[0022] As a preferred technical solution, the unbalanced compensation coefficient is obtained by calculating the margin of the total unbalanced current compensation command based on the capacity coefficient of each three-phase photovoltaic converter participating in the compensation, including the following steps:

[0023] Step S21: Calculate the maximum allowable current value per phase of each photovoltaic converter based on the rated power, rated voltage and preset capacity factor of each converter;

[0024] Step S22: Calculate the dynamic remaining capacity of each converter based on the maximum allowable current value and the current operating current value; calculate the total remaining compensation capacity of the converter cluster based on the dynamic remaining capacity;

[0025] Step S23: Compare the total remaining compensation capacity with the compensation capacity required by the total unbalanced current compensation command to calculate the total unbalanced compensation coefficient;

[0026] Step S24: Allocate the total imbalance compensation coefficient to each converter according to the proportion of the dynamic remaining capacity of each converter in the total remaining compensation capacity to obtain the imbalance compensation coefficient corresponding to each converter.

[0027] As a preferred technical solution, the step of classifying and simplifying the total unbalanced current compensation command based on the rated current and remaining capacity of the three-phase photovoltaic converter cluster to obtain the rated compensation current limit includes the following steps:

[0028] Step S31: Divide the converter cluster into high-capacity compensation units and conventional compensation units based on the rated current and real-time remaining capacity of each converter.

[0029] Step S32: Determine the first-level compensation current limit corresponding to the high-capacity compensation unit based on the maximum allowable current value and the current operating current value; determine the second-level compensation current limit corresponding to the conventional compensation unit based on the total remaining compensation capacity and the minimum operating voltage of the converter cluster;

[0030] Step S33: The first-level compensation current limit and the second-level compensation current limit are weighted and summed to obtain the rated compensation current limit.

[0031] As a preferred technical solution, the step of adaptively weighting and fusing the unbalanced compensation coefficient and the rated compensation current limit to obtain the target compensation current command for each photovoltaic converter includes the following steps:

[0032] Step S41: Calculate the basic compensation current command for each converter based on the unbalance compensation coefficient and rated compensation current limit of each converter;

[0033] Step S42: Set an adaptive weighting factor based on the real-time remaining capacity and operating status of each converter; the operating status includes converter temperature, aging degree, and response speed;

[0034] Step S43: Use the adaptive weighting factor to weight and correct the basic compensation current command to generate a preliminary target compensation current command;

[0035] Step S44: The initial target compensation current command is limited using an adaptive protection coefficient to generate the target compensation current command; wherein, the adaptive protection coefficient is a variable parameter integral adjustment coefficient based on power error.

[0036] Secondly, an embodiment of the present invention also provides a technical solution: a distributed current compensation system for a distribution network, applicable to the distributed current compensation method for a distribution network adapted to a photovoltaic converter cluster as described in the first aspect, comprising: a distributed controller, multiple three-phase photovoltaic converters, and a low-bandwidth communication network connecting the distributed controller and each three-phase photovoltaic converter.

[0037] The distributed controller is configured with:

[0038] The unbalanced instruction calculation module is used to decouple the unbalanced components of the three-phase electrical quantities at the transformer outlet of the distribution substation and generate a total unbalanced current compensation instruction.

[0039] The adaptive coordination module is used to calculate the imbalance compensation coefficient based on the capacity factor of each photovoltaic converter, and to calculate the rated compensation current limit based on the rated current and remaining capacity of the converter cluster.

[0040] The instruction allocation module is used to adaptively weight and fuse the unbalanced compensation coefficient and the rated compensation current limit to generate the target compensation current instruction;

[0041] Each of the aforementioned three-phase photovoltaic converters is equipped with:

[0042] The local control unit is used to implement unbalanced component decoupling control and execute the received target compensation current command;

[0043] A communication interface unit is used for data communication with the distributed controller;

[0044] The status monitoring unit is used to monitor the operating status of the converter in real time;

[0045] The low-bandwidth communication network adopts a master-slave unidirectional communication architecture.

[0046] Thirdly, one technical solution provided in this embodiment of the invention is: an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor, when calling the computer program in the memory, implements the steps of the distributed current compensation method for the distribution network adapted to the photovoltaic converter cluster as described in the first aspect.

[0047] Fourthly, one technical solution provided in this embodiment of the invention is: a storage medium storing computer-executable instructions, wherein when the computer-executable instructions are loaded and executed by a processor, the steps of the distributed current compensation method for the distribution network adapted to the photovoltaic converter cluster as described in the first aspect are implemented.

[0048] The present invention has at least the following substantial beneficial effects:

[0049] (1) In view of the problem that existing compensation schemes are inefficient and prone to overcurrent risks due to the failure to accurately lock the unbalance components and the neglect of converter capacity limitations, this application constructs a transformation matrix by using the symmetrical component method to deeply decouple the three-phase electrical quantities at the transformer outlet, accurately separates the negative sequence and zero sequence current components and generates a total unbalance current compensation command in combination with the unbalance threshold. At the same time, the dynamic remaining capacity is calculated based on the rated power, voltage and capacity coefficient of each converter, and the unbalance compensation coefficient is allocated according to the proportion of remaining capacity. This achieves accurate coordination between the compensation command and the converter carrying capacity, which not only ensures the pertinence of the compensation from the source, but also eliminates the overcurrent risk in principle, and maximizes the remaining compensation potential of the converter cluster.

[0050] (2) In view of the problem that the existing scheme has complex calculation logic and is not adapted to the rapid fluctuation characteristics of photovoltaic power, resulting in delayed compensation response, this application classifies the converter cluster into high-capacity compensation units and conventional compensation units by classifying the rated current and real-time remaining capacity of the converter cluster. The first-level and second-level compensation current limits are calculated and weighted to obtain the rated compensation current limit. This simplifies the calculation complexity of multi-converter collaborative compensation and avoids the cumbersome solution process of traditional optimization algorithms. This significantly improves the efficiency of compensation command generation, adapts to the response requirements of second-level power fluctuation of photovoltaic converters, and realizes rapid compensation of unbalanced current.

[0051] (3) In view of the problems of lack of dynamic adaptability of compensation instructions and insufficient system operation robustness of existing schemes, this application sets an adaptive weight factor by integrating the real-time remaining capacity of the converter with the operating status such as temperature, aging degree, and response speed, and performs dual optimization of the basic compensation instructions by combining the variable parameter integral adaptive protection coefficient based on power error. When the error is small, the adjustment rate is accelerated to reduce steady-state error, and when the error is large, the adjustment rhythm is stabilized to avoid overshoot. A dynamic closed-loop instruction optimization system is constructed, which realizes the real-time adaptation of compensation instructions to the unbalanced state of the power grid and the operating state of the converter, and significantly improves the accuracy of distribution network current compensation and system operation robustness.

[0052] The above description of the invention is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0053] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0054] Figure 1 This is a flowchart of a distributed current compensation method for distribution networks adapted to photovoltaic converter clusters, as described in an embodiment of the present invention.

[0055] Figure 2 This is a structural diagram of a distributed current compensation system for a power distribution network according to an embodiment of the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations (or steps) can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but it may also have additional steps not included in the figures; the process may correspond to a method, function, procedure, subroutine, subroutine, etc.

[0058] Before describing the specific implementation methods of this application, it is necessary to review the key technical barriers in the prior art that restrict the improvement of the distribution network imbalance compensation effect. Existing solutions generally face three dilemmas: First, relying on high-bandwidth, bidirectional real-time communication between converters and controllers not only creates a heavy communication burden and cost, but also leads to system coordination failure when communication is delayed or interrupted; second, either treating multi-converter coordination as a complex optimization problem, the solution time is difficult to match the second-level fluctuations in photovoltaic power, or using precise algorithms to pursue single-point compensation accuracy, but the high computational resource requirements make large-scale deployment difficult; third, most methods do not embed the real-time operating capacity of the converter as a core constraint into the control command allocation process, lacking an effective overload prevention mechanism, resulting in an inherent contradiction between compensation capability and equipment safety. These interrelated technical bottlenecks collectively lead to the deficiencies of existing compensation schemes in response speed, engineering applicability, and operational reliability.

[0059] Based on this, the first embodiment provided in this application aims to overcome the aforementioned barriers, such as... Figure 1 As shown, the distributed current compensation method for distribution networks adapted to photovoltaic converter clusters includes the following steps:

[0060] Step S1: Decouple the unbalanced components of the three-phase electrical quantities obtained from the transformer outlet of the distribution substation to obtain the total unbalanced current compensation command.

[0061] It should be noted that existing distribution network unbalanced current compensation schemes often use simplified models to process the three-phase electrical quantities at the transformer outlet, which cannot accurately separate core unbalanced components such as negative-sequence and zero-sequence currents. This leads to a misalignment between the compensation command and the actual unbalanced source, easily resulting in ineffective compensation or overcompensation. This application further proposes an optional implementation method, specifically: decoupling the unbalanced components of the three-phase electrical quantities obtained at the transformer outlet of the distribution substation to obtain the total unbalanced current compensation command, and implementing the following steps:

[0062] Step S11: Real-time acquisition of three-phase voltage and three-phase current signals at the transformer outlet of the distribution substation;

[0063] Understandably, high-precision sampling modules (such as 16-bit ADC sampling chips with a sampling period of Ts=10KHz) can be used to collect the three-phase voltage and three-phase current signals at the transformer outlet of the distribution substation in real time, ensuring the real-time performance and high fidelity of the original electrical data.

[0064] Step S12: The three-phase voltage signal and the three-phase current signal are decomposed into components using the symmetrical component method, and the negative sequence current component and the zero sequence current component are separated.

[0065] It is understandable that the negative sequence current component The zero-sequence current component is obtained by extracting the transformed negative-sequence channel data. Through the zero-sequence channel formula It enables precise separation of the core components of unbalanced current, solving the problem that traditional solutions cannot distinguish sequence components.

[0066] Step S13: Based on the negative sequence current component and the zero sequence current component combined with the preset unbalance threshold, decouple to generate the initial unbalance current compensation command.

[0067] Understandably, to generate a precise target lock for the compensation command, based on the separated... and Based on preset imbalance thresholds (e.g., negative sequence current threshold of 5A, zero sequence current threshold of 2A), determine whether to activate compensation (if...). and If none of the limits are exceeded, then the process will not be started for the time being; if at any time... If the current exceeds the remaining compensation capacity, compensation will be triggered. At the same time, based on the maximum compensation current constraint of the converter (such as the maximum allowable current of PV-1 photovoltaic converter is 42A, and if the initial command exceeds its remaining compensation capacity, it will be limited), the initial unbalanced current compensation command is generated. This avoids system waste when no compensation is needed and prevents the converter from overcurrent due to command exceeding the limit, thus ensuring the safety of compensation.

[0068] Step S14: Perform vector superposition processing on the initial unbalanced current compensation command to obtain the total unbalanced current compensation command.

[0069] Understandably, the initial unbalanced compensation command is vector-superimposed according to the three-phase phase relationship to obtain the total unbalanced current compensation command covering the negative sequence and zero sequence components. This ensures that the total command fully matches the unbalanced state of the transformer area, providing accurate and complete command basis for subsequent allocation of compensation tasks to the converter.

[0070] It should be noted that this embodiment provides an optional implementation method: using the symmetrical component method to decompose the three-phase voltage signal and the three-phase current signal into components and separate the negative sequence current component and the zero sequence current component. The specific implementation steps are as follows:

[0071] Step S121: Construct the transformation matrix of the symmetrical component method, and convert the collected three-phase voltage signal and three-phase current signal into positive sequence component, negative sequence component and zero sequence component through the transformation matrix;

[0072] Step S122: Extract the negative sequence current component corresponding to the negative sequence component and the zero sequence current component corresponding to the zero sequence component respectively.

[0073] It is understandable that the transformation matrix of the symmetric component method is: Complex operators ;in, , , These are the positive-sequence, negative-sequence, and zero-sequence current components, respectively. , , The actual operating current of the three phases A, B, and C at the transformer outlet of the distribution area.

[0074] It is understood that this embodiment introduces a multi-dimensional decoupling analysis technique based on the symmetric component method to construct a standardized transformation matrix for orthogonal decomposition of three-phase electrical quantities. Specifically, the voltage and current signals in the three-phase coordinate system are decoupled into mutually independent positive-sequence, negative-sequence, and zero-sequence components through the Park-Clarke composite transformation. On this basis, a selective extraction mechanism is designed to dynamically separate the negative-sequence current component, which represents phase asymmetry, and the zero-sequence current component, which reflects the neutral point potential, from the decoupled component set.

[0075] It should be noted that after separating the negative-sequence and zero-sequence current components, directly generating compensation commands can easily lead to problems such as ineffective system operation when no compensation is needed and overcurrent in the converter caused by excessive compensation. This embodiment provides an optional implementation method: generating initial unbalanced current compensation commands based on the negative-sequence current components and the zero-sequence current components combined with a preset unbalance threshold, including the following steps:

[0076] Step S131: Compare the amplitudes of the negative sequence current component and the zero sequence current component with the corresponding preset negative sequence current threshold and zero sequence current threshold, respectively, and determine whether to start compensation control.

[0077] It is understandable that the amplitude of the negative sequence current component obtained by separating the steps is... Zero-sequence current component amplitude The current is compared with preset negative sequence current thresholds (e.g., 5A for a transformer capacity of 1000kVA) and zero sequence current thresholds (e.g., 2A). Only when... and Compensation is initiated when all limits are exceeded, avoiding ineffective operation during minor imbalances and reducing system energy consumption.

[0078] Step S132: When the amplitude of any sequence current component exceeds the corresponding current threshold, compensation control is initiated, and the required negative sequence compensation current command and zero sequence compensation current command are calculated based on the degree of over-limit.

[0079] Understandably, the required compensation instruction (the difference between the amplitude of the flow component and the corresponding threshold) is calculated based on the quantification principle that the compensation amount is positively correlated with the degree of over-limit, ensuring that the compensation amount accurately matches the severity of the imbalance and avoiding insufficient or excessive compensation.

[0080] Step S133: Based on the maximum compensation current constraint, the negative sequence compensation current command and the zero sequence compensation current command are respectively subjected to amplitude limiting processing to generate the initial unbalanced current compensation command.

[0081] Understandably, based on the rated parameters of the converter (e.g., the rated current of a photovoltaic converter is 42A) and the real-time operating power, the dynamic remaining capacity is calculated (e.g., the remaining compensation capacity is 3A under a certain operating condition). The compensation command is limited by the constraint formula to eliminate the risk of converter overcurrent. The maximum compensation current constraint condition means that the target compensation current command amplitude of each three-phase photovoltaic converter must not exceed the difference between its rated current and real-time operating current (i.e., the remaining available compensation capacity), so as to avoid the risk of converter overcurrent and equipment damage caused by the compensation current exceeding the limit.

[0082] Step S2: Based on the capacity coefficient of each three-phase photovoltaic converter participating in the compensation, the margin of the total unbalanced current compensation command is calculated to obtain the unbalanced compensation coefficient.

[0083] It should be noted that the existing compensation task allocation scheme does not consider the capacity differences of each converter and the real-time remaining compensation capacity, which can easily lead to overcurrent in some converters or waste of remaining capacity. Therefore, it is necessary to construct a precise allocation logic based on capacity coefficient and dynamic remaining capacity. In this embodiment, the unbalanced compensation coefficient is obtained by calculating the margin of the total unbalanced current compensation command based on the capacity coefficient of each three-phase photovoltaic converter participating in the compensation, including the following steps:

[0084] Step S21: Calculate the maximum allowable current value per phase of each photovoltaic converter based on the rated power, rated voltage and preset capacity factor of each converter.

[0085] Understandably, this is based on the rated power of each photovoltaic converter. (PV-1 photovoltaic converter rated power 50kW), rated voltage (e.g., 380V) and a preset capacity factor k (e.g., 0.8), maximum allowable current value Calculate the maximum allowable current value for each phase to lock the upper limit of the converter's safety compensation at the hardware level.

[0086] Step S22: Calculate the dynamic remaining capacity of each converter based on the maximum allowable current value and the current operating current value of each converter; calculate the total remaining compensation capacity of the converter cluster based on the dynamic remaining capacity.

[0087] Understandably, the dynamic remaining capacity is calculated based on the difference between the maximum allowable current value of each converter and the current operating current value (e.g., the photovoltaic converter PV-1 is currently operating at 40A), and the total remaining compensation capacity of the converter cluster is obtained by summing the dynamic remaining capacity of all participating converters, thus realizing the global quantification of the cluster's compensation potential.

[0088] Step S23: Compare the total remaining compensation capacity with the compensation capacity required by the total unbalanced current compensation command to calculate the total unbalanced compensation coefficient.

[0089] Understandably, the total remaining compensation capacity is compared with the compensation capacity required by the total unbalanced current compensation command to calculate the total unbalanced compensation coefficient (specifically, the ratio of the compensation capacity required by the total unbalanced current compensation command to the total remaining compensation capacity of the converter cluster) to ensure that the compensation task does not exceed the cluster's remaining capacity.

[0090] Step S24: Allocate the total imbalance compensation coefficient to each converter according to the proportion of the dynamic remaining capacity of each converter in the total remaining compensation capacity to obtain the imbalance compensation coefficient corresponding to each converter.

[0091] Understandably, based on the proportion of each converter's dynamic remaining capacity in the total remaining compensation capacity of the converter cluster, the total imbalance compensation coefficient is allocated to each converter to obtain the corresponding imbalance compensation coefficient. This achieves precise coordination between the compensation task and the remaining capacity of each converter, ultimately eliminating the risk of converter overcurrent and maximizing the utilization of the cluster's remaining compensation potential.

[0092] Step S3: Based on the rated current and remaining capacity of the three-phase photovoltaic converter cluster, the total unbalanced current compensation command is classified and simplified to obtain the rated compensation current limit.

[0093] It should be noted that existing solutions do not classify the different compensation capabilities of each device within the converter cluster, resulting in redundant calculation logic, instruction generation delays, and an inability to adapt to the second-level fluctuation characteristics of photovoltaic power. This embodiment simplifies the total unbalanced current compensation instruction by classifying it according to the rated current and remaining capacity of the three-phase photovoltaic converter cluster to obtain the rated compensation current limit; including the following steps:

[0094] Step S31: Based on the rated current and real-time remaining capacity of each converter, divide the converter cluster into high-capacity compensation units and conventional compensation units.

[0095] Understandably, based on the rated current and real-time remaining capacity of each converter (e.g., PV-1 has a remaining capacity of 12A and PV-2 has a remaining capacity of 6A), a classification threshold is set (e.g., rated current ≥ 40A and remaining capacity ≥ 10A are high-capacity compensation units, and vice versa). PV-1 is classified as a high-capacity compensation unit and PV-2 is classified as a regular compensation unit, thereby achieving precise stratification of compensation capabilities within the cluster and simplifying the subsequent limit calculation logic.

[0096] Step S32: Determine the first-level compensation current limit corresponding to the high-capacity compensation unit based on the maximum allowable current value and the current operating current value; determine the second-level compensation current limit corresponding to the conventional compensation unit based on the total remaining compensation capacity and the minimum operating voltage of the converter cluster.

[0097] Understandably, for high-capacity compensation units, the first-level compensation current limit is determined by the difference between the maximum allowable current and the real-time current to ensure full utilization of their redundant capacity. Furthermore, for conventional compensation units, the second-level compensation current limit is calculated based on the ratio of the total remaining compensation capacity to the lowest operating voltage of the converter cluster (e.g., 370V) to adapt to their limited compensation capabilities.

[0098] Step S33: The first-level compensation current limit and the second-level compensation current limit are weighted and summed to obtain the rated compensation current limit.

[0099] Understandably, by setting weighting coefficients based on the proportion of the number or capacity of the two types of units (e.g., 0.5 for high-capacity units and 0.5 for conventional units), and obtaining the rated compensation current limit through weighted summation, the technical effect of achieving a rated compensation current limit that fits the cluster differences and adapts to the dynamic characteristics of photovoltaics is ultimately realized.

[0100] Step S4: Perform adaptive weighted fusion processing on the unbalanced compensation coefficient and the rated compensation current limit to obtain the target compensation current command for each photovoltaic converter.

[0101] It should be noted that compensation commands generated solely based on the imbalance compensation coefficient and the rated compensation current limit do not dynamically adapt to the real-time operating status of the converter (such as temperature and aging degree), which can easily lead to a disconnect between the command and the actual load-bearing capacity of the equipment and the grid demand. This embodiment uses adaptive weighted fusion processing of the imbalance compensation coefficient and the rated compensation current limit to obtain the target compensation current command for each photovoltaic converter; including the following steps:

[0102] Step S41: Calculate the basic compensation current command for each converter based on the unbalance compensation coefficient and rated compensation current limit of each converter.

[0103] The basic compensation current command is obtained by multiplying the unbalance compensation coefficient k of each converter and the rated compensation current limit, which provides a reference command for subsequent optimization.

[0104] Step S42: Set an adaptive weighting factor based on the real-time remaining capacity and operating status of each converter; the operating status includes converter temperature, aging degree and response speed.

[0105] Understandably, based on the real-time remaining capacity and operating status (temperature, aging degree converted to health coefficient using years of operation, and response speed) of each converter, corresponding weight coefficients are set (e.g., [0.3, 0.4, 0.3] respectively). The adaptive weight factor is calculated by weighted summation to achieve a precise correlation between command correction and equipment status. For example, since there is a direct positive correlation between remaining capacity and temperature, the temperature coefficient is used as a weight to influence the safety compensation capability in the calculation. Therefore, the adaptive weight factor = 0.3 × (real-time remaining capacity / maximum real-time remaining capacity) + 0.4 × health coefficient + 0.3 × response speed, thus achieving a precise correlation between command correction and equipment status.

[0106] Step S43: Use the adaptive weighting factor to weight and correct the basic compensation current command to generate a preliminary target compensation current command.

[0107] It is understood that the adaptive weighting factor weights and modifies the basic compensation current command to generate a preliminary target compensation current command, thereby adapting the command to the real-time operating capability of the device.

[0108] Step S44: The initial target compensation current command is limited using an adaptive protection coefficient to generate the target compensation current command; wherein, the adaptive protection coefficient is a variable parameter integral adjustment coefficient based on power error.

[0109] It is understandable that, due to capacity limitations, the remaining capacity of the photovoltaic converter may not be sufficient to fully compensate for the unbalanced current. Therefore, when actually issuing compensation power commands to the photovoltaic converter, overcurrent of the converter should be avoided, so as to avoid the reduction of system stability due to integral action and prevent large overshoot. The specific principle is: when the power error is small, the protection coefficient is increased to reduce the steady-state error of the system.

[0110] In the initial control phase, the system introduces the maximum actual compensation power, and the deviations in remaining capacity and harmonic imbalance power are significant. At this time, the current compensation speed of each converter is relatively fast, and there may be significant differences in the compensation speed between converters. Based on the parameter design of fuzzy control, in the control of current compensation of each converter, a relatively stable rate of change is limited to ensure that the system current distribution does not change drastically in a short period of time. The design idea is as follows:

[0111] When the power error |e(t)| is large, the variable parameter integral adjustment coefficient is (k stand ×e thresold ) / |e(t)|,e thresold The power error threshold is used to ensure that the virtual impedance changes at a consistent rate. By limiting the initial target compensation current command through this coefficient, the command adjustment rate can be reduced, avoiding overcurrent caused by rapid changes in compensation power in the converter. At the same time, it ensures that the compensation speed of each device in the converter cluster tends to be consistent, preventing drastic fluctuations in system current distribution.

[0112] When the power error |e(t)| is small, the variable parameter integral adjustment coefficient is k. stand To speed up the adjustment process. stand The constant is denoted as , where the power error is the absolute value of the difference between the set compensation power corresponding to the initial target compensation current command and the actual compensation power fed back by the converter in real time. At this time, there is no need to limit the adjustment rate, which can speed up the command response speed, reduce the steady-state error of the system, and ensure the accuracy of unbalanced current compensation.

[0113] Existing distribution network compensation systems mostly adopt centralized control or high-bandwidth bidirectional communication architectures, which suffer from large communication delays and poor coordination between converters and controllers. They cannot adapt to the second-level power fluctuation characteristics of photovoltaic converter clusters and lack real-time sensing and dynamic command adjustment mechanisms for converter operating status, resulting in delayed compensation response and high equipment safety risks. The second embodiment of this invention provides a distributed current compensation system for distribution networks, applicable to the distributed current compensation method for photovoltaic converter clusters as described in the first embodiment. Figure 2 As shown, it includes: a distributed controller 1, multiple three-phase photovoltaic converters 2, and a low-bandwidth communication network 3 connecting the distributed controller and each three-phase photovoltaic converter;

[0114] The distributed controller is configured with:

[0115] The unbalanced instruction calculation module 101 is used to decouple the unbalanced components of the three-phase electrical quantities at the output of the transformer in the distribution area and generate a total unbalanced current compensation instruction.

[0116] The adaptive coordination module 102 is used to calculate the unbalance compensation coefficient based on the capacity coefficient of each photovoltaic converter, and to calculate the rated compensation current limit based on the rated current and remaining capacity of the converter cluster.

[0117] The instruction allocation module 103 is used to perform adaptive weighted fusion processing on the unbalanced compensation coefficient and the rated compensation current limit to generate a target compensation current instruction;

[0118] Each of the aforementioned three-phase photovoltaic converters is equipped with:

[0119] The local control unit 201 is used to implement unbalanced component decoupling control and execute the received target compensation current command;

[0120] Communication interface unit 202 is used for data communication with the distributed controller;

[0121] The status monitoring unit 203 is used to monitor the operating status of the converter in real time;

[0122] The low-bandwidth communication network adopts a master-slave unidirectional communication architecture.

[0123] In this embodiment, the distributed controller integrates an imbalance command calculation module, an adaptive coordination module, and a command allocation module to achieve global command generation and coordination. Multiple three-phase photovoltaic converters are equipped with local control units, communication interface units, and status monitoring units to achieve local execution and status feedback. A low-bandwidth communication network ensures efficient transmission of commands and status data. Specifically, the imbalance command calculation module of the distributed controller uses a symmetrical component method to decouple the three-phase electrical quantities at the transformer outlet of the distribution substation, accurately separating the negative-sequence and zero-sequence current components and combining them with the imbalance threshold to generate a total imbalance current compensation command, locking in the compensation target from the source. The adaptive coordination module calculates the maximum allowable current and dynamic remaining capacity based on the rated parameters (rated power, voltage, capacity coefficient) of each converter, thereby obtaining the total remaining compensation capacity and total imbalance compensation coefficient of the cluster (allocated to each converter according to the remaining capacity ratio), while also dividing high-voltage... The capacity / conventional compensation unit calculates the graded compensation current limit and weights it to obtain the rated compensation current limit. The command allocation module integrates the unbalanced compensation coefficient with the rated compensation current limit and generates the target compensation current command based on the real-time operating status of the converter. The status monitoring unit of the three-phase photovoltaic converter collects data such as temperature and aging degree in real time and uploads it through the communication interface unit. After receiving the command, the local control unit executes the unbalanced component decoupling and compensation action. The low-bandwidth communication network uses the distributed controller as the master node and the converter as the slave node, and adopts unidirectional communication to significantly reduce bandwidth occupation and latency. Finally, it realizes the full-process collaboration of global generation of compensation command - status feedback - local execution, which not only avoids the traditional communication latency problem and adapts to the second-level fluctuation of photovoltaic power, but also eliminates the risk of overcurrent through status perception and dynamic command optimization, ensuring equipment safety while significantly improving the accuracy of unbalanced current compensation in the distribution network and the robustness of system operation.

[0124] The third embodiment provided in this invention is: an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor, when calling the computer program in the memory, implements the steps of the distribution network distributed current compensation method adapted to photovoltaic converter clusters as described in the first embodiment.

[0125] The fourth embodiment provided in the invention is: a storage medium storing computer-executable instructions, which, when loaded and executed by a processor, implement the steps of the distributed current compensation method for the distribution network adapted to the photovoltaic converter cluster as described in the first embodiment.

[0126] Through the above description of the embodiments, those skilled in the art will understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the specific device can be divided into different functional modules to complete all or part of the functions described above.

[0127] In the embodiments provided in this application, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another structure, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between structures or units, and may be electrical, mechanical, or other forms.

[0128] The units described as separate components may or may not be physically separate. A component shown as a unit can be one or more physical units; that is, it can be located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0129] Furthermore, in the embodiments of this application, the functional units can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0130] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0131] The specific embodiments described above are preferred embodiments of the distributed current compensation method and system for photovoltaic converter clusters in power distribution networks according to the present invention, and are not intended to limit the specific scope of the present invention. The scope of the present invention includes but is not limited to the specific embodiments described above. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A method for distribution network distributed current compensation for adapting a cluster of photovoltaic inverters, characterized in that: The method comprises the following steps: Step S1: decoupling the three-phase electrical quantities obtained at the outlet of the distribution area transformer to obtain total unbalanced current compensation instructions; Step S2: calculating the total unbalanced current compensation instructions based on the capacity coefficients of the three-phase photovoltaic converters participating in compensation to obtain unbalanced compensation coefficients; Step S3: classifying and simplifying the total unbalanced current compensation instructions based on the rated current and residual capacity of the three-phase photovoltaic converter cluster to obtain rated compensation current limits; Step S4: adaptively weighting and fusing the unbalanced compensation coefficients and the rated compensation current limits to obtain target compensation current instructions for each photovoltaic converter; The adaptively weighting and fusing the unbalanced compensation coefficients and the rated compensation current limits to obtain target compensation current instructions for each photovoltaic converter comprises the following steps: Step S41: calculating the basic compensation current instructions of each converter based on the unbalanced compensation coefficients and the rated compensation current limits of each converter; Step S42: setting adaptive weight factors according to the real-time residual capacity and operating state of each converter; The operating state includes converter temperature, aging degree and response speed; Step S43: weighting and correcting the basic compensation current instructions using the adaptive weight factors to generate preliminary target compensation current instructions; Step S44: limiting the amplitude of the preliminary target compensation current instructions using an adaptive protection coefficient to generate the target compensation current instructions; wherein the adaptive protection coefficient is a variable parameter integral adjustment coefficient based on power error.

2. The distribution network distributed current compensation method for adapting a photovoltaic converter cluster according to claim 1, characterized in that: The decoupling of the three-phase electrical quantities obtained at the outlet of the distribution area transformer to obtain total unbalanced current compensation instructions comprises the following steps: Step S11: real-time acquisition of three-phase voltage signals and three-phase current signals at the outlet of the distribution area transformer; Step S12: component decomposition of the three-phase voltage signals and three-phase current signals using the symmetrical component method to separate out negative sequence current components and zero sequence current components; Step S13: decoupling based on the negative sequence current components and the zero sequence current components in combination with a preset unbalance degree threshold to generate initial unbalanced current compensation instructions; Step S14: vector superposition processing of the initial unbalanced current compensation instructions to obtain the total unbalanced current compensation instructions.

3. The method of claim 2, wherein the method is characterized by: The component decomposition of the three-phase voltage signals and three-phase current signals using the symmetrical component method to separate out negative sequence current components and zero sequence current components comprises the following steps: Step S121: constructing a transformation matrix of the symmetrical component method to convert the acquired three-phase voltage signals and three-phase current signals into positive sequence components, negative sequence components and zero sequence components; Step S122: extracting negative sequence current components corresponding to negative sequence components and zero sequence current components corresponding to zero sequence components, respectively.

4. The distribution network distributed current compensation method for adapting a photovoltaic converter cluster according to claim 2, characterized in that: The initial unbalanced current compensation instruction is generated by decoupling based on the negative sequence current component and the zero sequence current component in combination with a preset unbalance degree threshold, and includes the following steps: Step S131: comparing the amplitudes of the negative sequence current component and the zero sequence current component with corresponding preset negative sequence current threshold and zero sequence current threshold respectively, and determining whether to start compensation control; Step S132: starting compensation control when the amplitude of any sequence current component exceeds the corresponding current threshold, and calculating the required negative sequence compensation current instruction and zero sequence compensation current instruction based on the over-limit degree; Step S133: limiting the amplitudes of the negative sequence compensation current instruction and the zero sequence compensation current instruction respectively based on the maximum compensation current constraint condition to generate the initial unbalanced current compensation instruction.

5. The power distribution network distributed current compensation method for adapting to a photovoltaic converter cluster according to claim 2, characterized in that: The unbalanced compensation coefficient is calculated by margin calculation on the total unbalanced current compensation instruction based on the capacity coefficient of each three-phase photovoltaic converter participating in compensation, and includes the following steps: Step S21: calculating the maximum allowable current value of each phase of each photovoltaic converter according to the rated power, rated voltage and preset capacity coefficient of each photovoltaic converter; Step S22: calculating the dynamic residual capacity of each converter based on the maximum allowable current value and the current operating current value of each converter; calculating the total residual compensation capacity of the converter cluster according to the dynamic residual capacity; Step S23: comparing the total residual compensation capacity with the required compensation capacity of the total unbalanced current compensation instruction to calculate the total unbalanced compensation coefficient; Step S24: distributing the total unbalanced compensation coefficient to each converter according to the proportion of the dynamic residual capacity of each converter in the total residual compensation capacity to obtain the corresponding unbalanced compensation coefficient of each converter.

6. The power distribution network distributed current compensation method for adapting to a photovoltaic converter cluster according to claim 5, characterized in that: The rated compensation current limit value is obtained by classifying and simplifying the total unbalanced current compensation instruction according to the rated current and residual capacity of the three-phase photovoltaic converter cluster; including the following steps: Step S31: dividing the converter cluster into a high-capacity compensation unit and a conventional compensation unit based on the rated current and real-time residual capacity of each converter; Step S32: determining the first-level compensation current limit value corresponding to the high-capacity compensation unit based on the maximum allowable current value and the current operating current value; determining the second-level compensation current limit value corresponding to the conventional compensation unit based on the total residual compensation capacity and the lowest operating voltage of the converter cluster; Step S33: performing weighted summation on the first-level compensation current limit value and the second-level compensation current limit value to obtain the rated compensation current limit value.

7. A power distribution network distributed current compensation system, adapted to the power distribution network distributed current compensation method of adapting a photovoltaic inverter cluster as claimed in any one of claims 1 to 6, characterized in that: It includes: a distributed controller, a plurality of three-phase photovoltaic converters, and a low-bandwidth communication network connecting the distributed controller and each three-phase photovoltaic converter; The distributed controller is configured with: an unbalanced instruction calculation module for decoupling unbalanced components of three-phase electrical quantities at the outlet of a power distribution substation transformer to generate a total unbalanced current compensation instruction; An adaptive coordination module is configured to calculate an unbalance compensation coefficient based on a capacity coefficient of each photovoltaic converter, and to calculate a rated compensation current limit value according to a rated current and a residual capacity of the converter cluster; An instruction distribution module is configured to perform adaptive weighted fusion processing on the unbalance compensation coefficient and the rated compensation current limit value to generate a target compensation current instruction; Each of the plurality of three-phase photovoltaic converters is configured with: A local control unit is configured to implement unbalance component decoupling control and execute the received target compensation current instruction; A communication interface unit is configured to perform data communication with the distributed controller; A state monitoring unit is configured to monitor the operating state of the converter in real time. The low-bandwidth communication network adopts a master-slave one-way communication architecture.

8. An electronic device, comprising: The memory stores a computer program, and the processor invokes the computer program in the memory to implement the steps of the power distribution network distributed current compensation method for an adaptive photovoltaic converter cluster according to any one of claims 1-6.

9. A storage medium characterized by: The storage medium stores computer executable instructions, and the processor loads and executes the computer executable instructions to implement the steps of the power distribution network distributed current compensation method for an adaptive photovoltaic converter cluster according to any one of claims 1-6.

Images