A branch dynamic pressure drop compensation regulation method and system

Abstract

The application relates to the technical field of power supply regulation, and discloses a branch line dynamic voltage drop compensation regulation method and system, which comprises the following steps: acquiring branch line topological parameters and current power adjustment ratios of each load node, collecting environmental temperature and cable surface temperature to dynamically correct cable resistance between adjacent nodes, and establishing a voltage recursive model from the head end to the tail end of the branch line; calculating the cumulative voltage drop at the tail end and determining the source end dynamic compensation voltage; collecting the actual operating voltage at the tail end and comparing it with the target voltage, and when the deviation meets the preset condition, the compensation coefficient is closed-loop self-adaptive corrected and limited in the preset range; the source end dynamic compensation voltage is updated according to the corrected compensation coefficient, and the source end output voltage is adjusted; when the load power changes are monitored, the changed nodes and downstream are locally recursively recalculated; through the cable resistance temperature dynamic correction and the closed-loop correction of the compensation coefficient, the application realizes accurate regulation of the voltage at the tail end of the branch line.

Description

Technical Field

[0001] This application relates to the field of power supply regulation technology, and more specifically to a branch line dynamic voltage drop compensation regulation method and system. Background Technology

[0002] In long-distance branch load systems, load nodes are typically distributed in series along the branch, with dozens of nodes distributed from the beginning to the end of the branch, and the total cable length can reach several kilometers. As the power supply distance increases, the cable resistance accumulates segment by segment, and the voltage of each load node gradually decreases from the beginning to the end, resulting in a common problem of lower actual operating voltage at the end nodes. Traditional solutions generally calculate a fixed compensation voltage based on the rated load and cable parameters during the design phase, and then increase the output voltage at the source end to compensate for the voltage drop at the end.

[0003] Existing technologies suffer from the following problems: fixed compensation schemes rely on parameter calculations during the design phase, but in actual operation, the power of the load deviates from the rated value due to changes in power adjustment strategies, and the cable resistance also changes with ambient temperature and cable self-heating; fixed compensation amounts cannot adapt to these dynamic changes. Source-end voltage regulation relies solely on offline calculated voltage drop values, without collecting actual voltage data at the end for feedback correction, thus failing to compensate for model calculation deviations and long-term operational parameter drift. When the power adjustment ratio of individual load nodes in a branch line changes, the current distribution of the entire branch line changes accordingly; existing schemes require recalculating the voltage drop of the entire line from the beginning, resulting in a large computational load and delayed response. To address at least one of the above problems, this application proposes a dynamic voltage drop compensation and control method and system for branch lines. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this application is to provide a dynamic voltage drop compensation and control method and system for branch lines, which can effectively solve the problems in the background technology. The specific technical solution of this application is as follows:

[0005] A method for dynamic voltage drop compensation and control of branch lines, comprising:

[0006] Obtain the branch topology parameters and the current power adjustment ratio of each load node, collect the ambient temperature and cable surface temperature along the branch, dynamically correct the cable resistance between adjacent nodes based on the cable resistance temperature coefficient, and establish a voltage recursive model from the beginning to the end of the branch for each load node.

[0007] Based on the voltage recursion model, the cumulative voltage drop at the end node of the branch line is calculated recursively according to the load current of each load node and the corrected cable resistance between adjacent nodes. The source end dynamic compensation voltage is determined according to the cumulative voltage drop and the preset end target voltage.

[0008] The actual operating voltage of the load node at the end of the branch line is collected and compared with the target voltage at the end. When the voltage deviation meets the preset correction conditions, the compensation coefficient is subjected to closed-loop adaptive correction, and the corrected compensation coefficient is limited to the preset upper and lower limits.

[0009] The source-end dynamic compensation voltage is updated according to the corrected compensation coefficient, and the source-end output voltage is adjusted to the updated source-end dynamic compensation voltage. When the load power of any load node in the branch is detected to change, the cumulative voltage drop of the changed node and its downstream nodes is locally recursively recalculated, starting from the changed node, and the source-end dynamic compensation voltage is updated.

[0010] Specifically, the dynamic correction of cable resistance between adjacent nodes includes:

[0011] Obtain the nominal value of the resistance per unit length of the cable at the reference temperature and the temperature coefficient of resistance of the cable;

[0012] Calculate the difference between the cable surface temperature and the ambient temperature, multiply the difference by the preset thermal resistance coefficient from the cable surface to the internal conductor to obtain the conductor temperature rise, and add the ambient temperature to the conductor temperature rise to obtain the estimated conductor temperature.

[0013] The thermal resistance coefficient is determined through offline calibration tests: under different combinations of ambient temperature and load current, thermocouples are used to simultaneously measure the surface temperature of the cable and the actual temperature of the internal conductor. The ratio between the difference between the actual conductor temperature and the surface temperature and the difference between the surface temperature and the ambient temperature is used as the thermal resistance coefficient of the measurement point. The average value of all measurement points is taken as the preset thermal resistance coefficient.

[0014] The temperature difference is obtained by subtracting the reference temperature from the estimated temperature of the conductor. The temperature difference is then multiplied by the temperature coefficient of resistance of the cable and then by one, and finally multiplied by the nominal value to obtain the corrected resistance per unit length of the cable.

[0015] Multiply the corrected resistance per unit length of the cable by the cable length between adjacent nodes to obtain the corrected cable resistance between adjacent nodes.

[0016] Specifically, the recursive calculation of the cumulative voltage drop at the end node of the branch includes:

[0017] The beginning of the branch line is designated as node zero, and the cumulative voltage drop at node zero is zero.

[0018] For node i, where i takes values ​​from one to N, and N is the total number of load nodes in the branch, the voltage drop of the cable segment between node i-1 and node i is the current flowing through the cable segment multiplied by the corrected resistance of the cable segment and then multiplied by two. The current flowing through the cable segment is the sum of the load currents of all load nodes from node i to the end of the branch. The cumulative voltage drop of node i is equal to the cumulative voltage drop of node i-1 plus the voltage drop of the cable segment.

[0019] The load current of each load node is obtained by dividing the load power of the node by the actual operating voltage of the node. The actual operating voltage is obtained by subtracting the cumulative voltage drop of the node from the source output voltage. When the cumulative voltage drop of the node has not yet been calculated, the preset initial value of the source output voltage is used as the actual operating voltage of the zeroth node for iterative approximation.

[0020] Starting from node zero, the cumulative voltage drop at the end node of the branch is obtained by iterating step by step from node one to node N.

[0021] Specifically, determining the source-end dynamic compensation voltage based on the accumulated voltage drop and the preset end target voltage includes:

[0022] The source-end dynamic compensation voltage is obtained by adding the product of the compensation coefficient and the cumulative voltage drop to the preset end target voltage, and the initial value of the compensation coefficient is one.

[0023] A preset voltage margin is superimposed on the dynamic compensation voltage at the source end. The voltage margin is determined by multiplying the total length of the branch line by the nominal value of the resistance per unit length of the cable at the reference temperature, then by two, and then by a preset proportional coefficient of the rated total current of the branch line.

[0024] Specifically, the closed-loop adaptive correction of the compensation coefficient includes:

[0025] The voltage deviation at the current sampling time is subtracted from the voltage deviation at the previous sampling time to obtain the deviation change. The deviation change is multiplied by a preset proportional coefficient to obtain a proportional correction term. The voltage deviation at the current sampling time is multiplied by a preset integral coefficient to obtain an integral correction term. The compensation coefficient after the previous correction is added to the proportional correction term and the integral correction term to obtain the compensation coefficient after the current correction.

[0026] When the absolute value of the voltage deviation exceeds the preset anti-saturation threshold, the accumulation of the integral correction term is paused, and only the proportional correction term is retained for correction.

[0027] The current corrected compensation coefficient is compared with the preset upper and lower limits of the compensation coefficient. If it exceeds the range, the corresponding boundary value is taken.

[0028] Specifically, the upper and lower limits of the compensation coefficient are determined as follows:

[0029] During the initial power-on commissioning phase of the branch line, the power supply is powered by the preset initial source voltage. The actual operating voltage and load current of each load node are measured. The actual voltage drop of each cable segment is inferred from the difference between the source output voltage and the actual operating voltage of each node. The maximum value of the ratio of the actual voltage drop of each segment to the voltage drop of the corresponding segment calculated by the voltage recursion model is used as the upper limit of the compensation coefficient, and the minimum value is used as the lower limit of the compensation coefficient.

[0030] After normal operation, when the compensation coefficient correction amount is less than the preset dead zone threshold for multiple consecutive sampling periods, the updated upper and lower limits of the compensation coefficient are obtained by expanding the current corrected compensation coefficient as the center according to the preset ratio.

[0031] Specifically, the local recursive recalculation of the cumulative voltage drop of the changing node and its downstream nodes includes:

[0032] When a change in the load power of the kth load node is detected, the load current of the node with the change is updated. The current change of the cable from the 1st to the kth segment is calculated based on the updated load current, and the cumulative voltage drop of the 1st to the kth node is updated accordingly. Starting from the kth node, the cumulative voltage drop of the (k+1)th to the Nth node is updated recursively. When k equals 1, the recursion starts from the zeroth node and proceeds along the entire line.

[0033] If there are other nodes whose load power changes simultaneously between the k-th node and the end node, the load current of each node that changes will be updated synchronously, and the cumulative voltage drop of all nodes that change will be updated in one recalculation.

[0034] After the recalculation is completed, the cumulative voltage drop of the updated end node is compared with the cumulative voltage drop of the end node before the recalculation. If the absolute value of the difference between the two exceeds the preset recalculation threshold, the cumulative voltage drop of all nodes is recalculated using the full-line recursive method.

[0035] Specifically, the adjustment of the source output voltage includes:

[0036] The difference between the updated source-end dynamic compensation voltage and the current source-end output voltage is used as the total adjustment amount, and the total adjustment amount is divided into multiple adjustment steps according to the preset single maximum adjustment step size.

[0037] After each adjustment step, wait for a preset voltage stabilization time, collect the actual operating voltage of the load node at the end of the branch line, and if the absolute value of the deviation between the actual operating voltage and the target voltage at the end does not exceed the preset voltage deviation threshold, then terminate the subsequent adjustment steps.

[0038] If, during the execution of the adjustment step, the actual operating voltage of any intermediate load node is detected to exceed the preset overvoltage protection threshold, the adjustment is paused and reverted to the source output voltage of the previous adjustment step, and the node is marked.

[0039] Specifically, in the first operating cycle after the branch line is initially powered on or restarted from a power outage, the cumulative voltage drop of each node is calculated using a full-line recursive method to determine the initial source-end output voltage. Subsequently, in other operating cycles besides the first operating cycle, when the number of nodes with changed load power exceeds a preset node proportion threshold, the node closest to the beginning of the branch line is selected from the changed nodes and denoted as the k_min changed node. Starting from the zero node at the beginning of the branch line, the cumulative voltage drop of nodes 1 to k_min is updated level by level. Taking the updated cumulative voltage drop of node k_min as the starting point of the recursion, the cumulative voltage drop of nodes k_min+1 to N is updated only downstream according to the voltage recursion model.

[0040] A branch line dynamic voltage drop compensation and control system, used to implement the aforementioned branch line dynamic voltage drop compensation and control method, includes:

[0041] The parameter acquisition and correction module is used to acquire branch topology parameters and the current power adjustment ratio of each load node, collect the ambient temperature and cable surface temperature along the branch, and dynamically correct the cable resistance between adjacent nodes based on the thermal resistance coefficient and the cable resistance temperature coefficient.

[0042] The voltage recursion modeling module establishes a voltage recursion model from the beginning to the end of the branch node by load node based on the corrected cable resistance. It iteratively calculates the cumulative voltage drop at the end node of the branch based on the load current and actual operating voltage of each load node.

[0043] The compensation voltage calculation module is used to determine the source-end dynamic compensation voltage and add voltage margin based on the cumulative voltage drop and the preset end target voltage;

[0044] The terminal voltage feedback correction module is used to collect the actual operating voltage of the load node at the end of the branch line, compare it with the terminal target voltage, and perform closed-loop adaptive correction of the compensation coefficient when the voltage deviation meets the preset correction conditions. It also performs anti-saturation processing according to the magnitude of the deviation, and limits the corrected compensation coefficient to a dynamically updated preset range.

[0045] The source voltage regulation module is used to update the source dynamic compensation voltage according to the corrected compensation coefficient, adjust the source output voltage in a step-by-step manner, and perform backoff protection when overvoltage occurs. At the same time, it monitors the load power change and triggers full, partial or half line recursive recalculation.

[0046] The beneficial effects of this application are as follows: By collecting ambient temperature and cable surface temperature and dynamically correcting the cable resistance based on the offline calibrated thermal resistance coefficient, the conductor resistance drift caused by temperature changes is incorporated into the voltage recursion calculation in real time, solving the problem of increased calculation deviation in fixed parameter models when ambient temperature changes and cable self-heating occurs; by collecting the actual voltage at the end and performing incremental PI closed-loop correction on the compensation coefficient and introducing an anti-saturation mechanism, the upper and lower limits of the compensation coefficient are determined in the initial debugging stage and the correction range is gradually narrowed during operation, so that the compensation coefficient gradually converges to the stable range as the operating data accumulates, avoiding the limitations of simply relying on offline calculation or simply relying on feedback adjustment; by performing local recursion recalculation only on the changing node and downstream when the load power changes and setting a recalculation threshold for verification, the system automatically switches to full-line recursion when the local recalculation deviation is too large, and adopts a half-line recursion compromise scheme when batch load changes, thus balancing calculation efficiency and calculation accuracy. Attached Figure Description

[0047] Figure 1 This is a flowchart illustrating a branch line dynamic voltage drop compensation and control method in an embodiment of this application.

[0048] Figure 2 This is a schematic diagram illustrating the principle of dynamic temperature correction and voltage recursion modeling for cable resistance in the embodiments of this application;

[0049] Figure 3 This is a schematic diagram of the compensation coefficient closed-loop adaptive correction and local recursive recalculation process in the embodiments of this application;

[0050] Figure 4 This is a schematic diagram of the structure of a branch line dynamic voltage drop compensation and control system in an embodiment of this application. Detailed Implementation

[0051] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0052] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0053] Hereinafter, the terms "first," "second," and other generic terms 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0054] refer to Figure 1 The image shows a specific implementation of a branch line dynamic voltage drop compensation control method according to this application, including:

[0055] S101. Obtain the branch topology parameters and the current power adjustment ratio of each load node, collect the ambient temperature and cable surface temperature along the branch, dynamically correct the cable resistance between adjacent nodes based on the cable resistance temperature coefficient, and establish a voltage recursion model from the beginning to the end of the branch for each load node.

[0056] S102. Based on the voltage recursion model, calculate the cumulative voltage drop at the end node of the branch line according to the load current of each load node and the corrected cable resistance between adjacent nodes. Determine the source end dynamic compensation voltage according to the cumulative voltage drop and the preset end target voltage.

[0057] S103. Collect the actual operating voltage of the load node at the end of the branch line and compare it with the target voltage at the end. When the voltage deviation meets the preset correction conditions, perform closed-loop adaptive correction on the compensation coefficient and limit the corrected compensation coefficient to the preset upper and lower limits.

[0058] S104. Update the source-end dynamic compensation voltage according to the corrected compensation coefficient, and adjust the source-end output voltage.

[0059] S105. When a change in the load power of any load node in the branch is detected, starting from the changed node, the cumulative voltage drop of the changed node and its downstream nodes is recalculated locally to update the source-end dynamic compensation voltage.

[0060] The following uses a long-distance street light branch line as an example application scenario to illustrate the specific implementation of the method in this application. It is understood that the method of this application is also applicable to other load systems that are distributed in series along the branch line and have cable voltage drops.

[0061] In this embodiment, a typical long-distance street light branch line includes dozens of street lights, and the total cable length from the beginning to the end of the branch line may reach several kilometers. This embodiment uses a single-phase two-wire branch line as an example. For a three-phase four-wire branch line, it can be treated as an equivalent single-phase model, or the current of each phase, the neutral current, and the phase voltage can be calculated separately. The street lights are uniformly or non-uniformly distributed along the line, and each street light has an internal dimmable LED driver power supply with a power adjustment ratio that can be adjusted from 10% to 100%. An AC regulated power supply or DC power supply with adjustable output voltage is provided at the beginning of the branch line. The adjustment range and accuracy of the output voltage at the source end determine the voltage regulation capability of the entire branch line.

[0062] In this embodiment, the branch topology parameters are measured and entered manually during the system installation and debugging phase, and are considered fixed parameters that do not change after installation. The branch topology parameters specifically include the following: the total number of load nodes in the branch, denoted as N; the cable length between adjacent nodes, denoted as N; and the length of the cable between adjacent nodes. Node and the The cable length between nodes is denoted as The unit is meters; total length of the branch line ,satisfy The nominal resistance per unit length of the cable at a reference temperature is denoted as . The unit is The temperature of copper core cables at 20℃ is determined by the cable model and specifications. Approximately Aluminum core cable is approximately The temperature coefficient of resistance of the cable needs to be obtained from the manufacturer's datasheet or electrician's manual based on the actual cable model used; this is denoted as... The unit is copper Approximately Aluminum Approximately The rated power of each load node, where the rated power of the i-th load node is denoted as . The unit is W, given on the lamp nameplate; the rated total current of the branch line is denoted as... The unit is A. The current power adjustment ratio of each load node is denoted as... , The current load power of the i-th load node is read in real time from the street light controller via power line carrier, RS-485 bus, or wireless communication. The adjustment ratio is determined by the node's rated power and current power:

[0063] ;

[0064] In this embodiment, S101 obtains branch topology parameters and power adjustment ratios to provide basic input data for the voltage recursion model; S102 calculates the cumulative voltage drop at the end based on the dynamically corrected cable resistance to determine the source-end dynamic compensation voltage; S103 collects the actual voltage at the end for feedback, performs incremental PI closed-loop adaptive correction and limiting on the compensation coefficient; S104 updates the source-end dynamic compensation voltage according to the corrected compensation coefficient, adjusts the source-end output voltage in a step-by-step manner, and performs overvoltage protection; S105 performs local recursive recalculation only on the changing node and downstream when the load power changes, reducing the computational workload of recalculating the entire line. The specific implementation methods of each step are described in detail below.

[0065] Furthermore, the specific implementation method for dynamically correcting the cable resistance between adjacent nodes is as follows. The cable resistance changes with the conductor temperature, which is affected by both ambient temperature and the cable's own heat generation. Ambient temperature is denoted as... Temperature data is obtained through temperature sensors installed at representative locations along the branch line, with one sensor at each of the beginning, middle, and end of the branch line. The average of the three sensor readings is taken as the current ambient temperature. The surface temperature of the cable segment is denoted as By attaching to the Temperature is measured by a sensor located at the middle of the outer surface of the cable insulation layer. The sensor is fixed with cable ties, and the measurement point is selected at the middle of each cable segment because the middle position best represents the average temperature of the entire cable segment. One surface temperature sensor is installed on each cable segment, and the data is aggregated to the controller through a multi-channel temperature acquisition module.

[0066] A temperature gradient exists between the cable surface temperature and the actual temperature of the internal conductor, separated by a polyvinyl chloride or cross-linked polyethylene insulation layer. The actual conductor temperature is always higher than the surface temperature, and the extent of this difference depends on the current magnitude, the insulation material, and the thickness of the insulation layer. This application utilizes a preset thermal resistance coefficient between the cable surface and the internal conductor. This relationship is characterized by the thermal resistivity, which is defined as the difference between the actual temperature of the conductor and its surface temperature divided by the difference between the surface temperature and the ambient temperature. The following offline calibration test was conducted to determine the appropriate parameters: a 5-meter section of cable of the same model and specifications as the actual branch line was selected and tested in a laboratory environment; five temperature points were set in the constant temperature chamber, respectively... , , , and At each temperature point, the cable is respectively supplied with , and a DC current of 15A;

[0067] The point is only used as a reference for measuring the ambient temperature under no-load conditions and is not involved in the calculation of the thermal resistance coefficient. For each combination of ambient temperature and load current, the diameter is used as the reference. A type K thermocouple is inserted into the conductor from the cable end to measure the actual temperature of the conductor. At the same time, another thermocouple of the same type was attached to the surface of the cable to measure the surface temperature. For each set of measurement data, calculate the thermal resistance coefficient value at that measurement point using the following formula:

[0068] ;

[0069] in, This refers to the actual temperature of the conductor during this measurement. The cable surface temperature during this measurement. The ambient temperature at the time of this measurement. Less than the preset minimum temperature difference threshold (e.g.) When the measurement point is not cleared, it is discarded to avoid division by zero or numerical instability. The remaining measurement data is used to calculate the result. The average value is used as the preset thermal resistance coefficient. Before taking the average, remove outlier data points that significantly deviate from the overall trend: calculate the standard deviation of the remaining measurements and remove those exceeding the standard deviation. After identifying outliers, the average value of the remaining data is recalculated as the final thermal resistance coefficient. If the number of outliers exceeds the total number of measurement points... This indicates a potential systemic problem during the calibration process. Calibration should be stopped, and a prompt to check the measuring device should be displayed. The calibration results should be... Stored in the controller's non-volatile memory.

[0070] In actual operation, the ambient temperature is obtained by averaging the readings of three ambient temperature sensors in each sampling cycle. Then, the surface temperature of each cable segment is obtained by collecting readings from the surface temperature sensors of each cable segment. For the first For each section of cable, calculate the temperature difference between the cable surface and the ambient temperature, and multiply this difference by the thermal resistivity. Obtain the conductor temperature rise Then adjust the ambient temperature With conductor temperature rise Adding them together gives the estimated temperature of the conductor. :

[0071] ;

[0072] ;

[0073] in, For the first Temperature rise of the conductor in a cable segment, expressed in °C; For the first Estimated conductor temperature of a cable segment, in °C.

[0074] Obtain the nominal value of the resistance per unit length of the cable at a reference temperature. and the temperature coefficient of cable resistance .

[0075] Estimate the temperature of the conductor Subtract the reference temperature (reference temperature) Take 20℃ (the reference temperature for the nominal resistance value of the cable) to obtain the temperature difference, and multiply this temperature difference by the temperature coefficient of the cable resistance. Add one more, and multiply by the nominal value. The corrected resistance per unit length of the cable was obtained. :

[0076] ;

[0077] in, For the revised first Resistance per unit length of cable, in units of ; This is the nominal resistance per unit length of the cable at a reference temperature, in units of... ; Temperature coefficient of cable resistance, unit: ; As the reference temperature, .

[0078] The corrected resistance per unit length of the cable Multiply by the cable length between adjacent nodes The corrected cable resistance between adjacent nodes is obtained. :

[0079] ;

[0080] in, For the revised first Section cable (number) Node and the The cable resistance between nodes, in Ω; For the first Node and the The cable length between nodes, in meters.

[0081] Taking copper core cables as an example, in summer, with an ambient temperature of 38℃, a cable surface temperature of 52℃, and a thermal resistance coefficient of... Under the given conditions, the estimated conductor temperature is approximately 38 + (52 - 38) × 0.35 = 42.9℃, with a temperature difference of 22.9℃. The correction factor is 1 + 0.00393 × 22.9 ≈ 1.09, and the cable resistance increases by approximately 9% compared to the nominal value. In winter, with an ambient temperature of -5℃, a cable surface temperature of 2℃, and a thermal resistance coefficient of 0.35, the estimated conductor temperature is approximately -5 + (2 - (-5)) × 0.35 = -2.55℃, with a temperature difference of -22.55℃. The correction factor is 1 + 0.00393 × (-22.55) ≈ 0.91, and the cable resistance decreases by approximately 9% compared to the nominal value. If no temperature correction is applied to the cable resistance, the cumulative voltage drop calculated by the voltage recursion model will be too small in summer and too large in winter, leading to a systematic deviation between the source-end compensation voltage and the actual requirement.

[0082] Furthermore, the specific implementation method for recursively calculating the cumulative voltage drop at the end node of the branch based on the voltage recursion model is as follows.

[0083] The voltage recursion model treats the cable between two adjacent streetlight nodes in a branch line as a resistor. Current flows from one end to the other, and a voltage drop occurs each time the cable passes through a segment. In a single-phase two-wire system, the streetlight is connected in parallel between the live wire and the neutral wire. Current flows from the live wire through the streetlight and back through the neutral wire. Both the outgoing and returning cable segments incur voltage drops, so the voltage drop for each segment equals the current flowing through that segment multiplied by the corrected resistance of that segment, multiplied by two. For a three-phase four-wire system, if the three phases are balanced and the neutral current is ignored, the phase voltage drops are not multiplied by two and must be calculated using the three-phase model. If the three phases are unbalanced, the neutral current and its resulting voltage drop must also be calculated.

[0084] The first end (source end) of the branch line is designated as node zero. The cumulative voltage drop at node zero is zero, i.e. The total number of load nodes in the branch is N. For the th... Nodes, among which Values ​​are taken sequentially from 1 to N, flowing through the [number]th [stage]. Node and the Current in cable segments between nodes For the first The sum of the load currents of all load nodes from the node to the end of the branch:

[0085] ;

[0086] in, For the flow through the first The current in a cable segment, measured in amperes (A). Let be the load current of the j-th load node, in amperes (A).

[0087] No. Node and the Voltage drop of cable segments between nodes Multiply the current of that segment by the corrected resistance of that segment of cable. Multiply by 2 again:

[0088] ;

[0089] in, For the first Voltage drop across a cable segment, measured in volts (V). For the revised first The resistance of a cable segment, in units of .

[0090] No. cumulative voltage drop at the node equal to the cumulative voltage drop at the node In addition to the voltage drop of this cable segment :

[0091] ;

[0092] in, For the first The cumulative voltage drop at the node, in volts (V). .

[0093] Looking from the beginning to the end, the closer to the beginning of the cable segment, the higher the current flowing through it. The larger the current, the greater the voltage drop; the closer to the end of the cable segment, the smaller the current flowing through it, and the smaller the voltage drop. Load current at each load node. The load power of this node Divide by the actual operating voltage of the node get:

[0094] ;

[0095] in, For the first The load power of each load node, in watts (W). ; For the first The actual operating voltage of each load node, in volts (V).

[0096] No. The actual operating voltage of each load node Output voltage from source terminal Subtract the cumulative voltage drop at that node get:

[0097] ;

[0098] in, This is the output voltage at the source, in volts (V).

[0099] It is important to note the load current. Cumulative voltage drop and actual operating voltage There is a coupling relationship among the three. During the initial calculation, the actual operating voltage of each node is first used with the initial value of the source output voltage. Replacement, i.e., setting Calculate a set of load currents and cumulative voltage drops, then use... Subtracting the calculated cumulative voltage drop yields the actual operating voltage of each node. These actual operating voltages are then used to update the load current, and the cumulative voltage drop is recalculated, forming an iterative process. After each iteration, the difference between the current cumulative voltage drop of the terminal node and the previous cumulative voltage drop is compared. If the absolute value of this difference is less than a preset convergence threshold... Stop iteration when:

[0100] ;

[0101] in, This represents the cumulative voltage drop at the end node calculated in the kth iteration, in V. This represents the cumulative voltage drop at the end node calculated in the (k-1)th iteration, in V. The preset convergence threshold is taken in this embodiment. V. Because when the iterative change in the cumulative voltage drop at the end is less than 0.1V, the impact of continued iteration on the dynamic compensation voltage at the source is less than the minimum adjustment step size of the source power supply (1V). Further iteration has no practical engineering significance, and the calculation result can be considered to have converged. Therefore, ε is taken as 0.1V. For scenarios requiring higher accuracy, the convergence threshold is... The voltage drop can be appropriately reduced according to project requirements. Typically, after three to five iterations, the cumulative voltage drop value converges to an acceptable accuracy range for the project. Streetlight driver power supplies in practical engineering are mostly constant power or quasi-constant power types. When iteratively calculating the load current, a constant power model can be used as an approximation, that is, assuming the load power of each node... It equals the rated power multiplied by the current power adjustment ratio and does not change with the operating voltage. If the constant power characteristic of the drive power supply is poor, for example, the output power fluctuates significantly when the input voltage varies greatly, an adjustable AC power supply can be used to power the street light drive power supply during the offline phase. The actual input power can be measured under different input voltages to establish a correspondence table between input voltage and input power. During operation, the load power can be corrected iteratively by looking up the table. .

[0102] Starting from node zero and proceeding step by step through node one to node N, after iterative convergence, the cumulative voltage drop at the end node of the branch (node ​​N) is obtained. .

[0103] Furthermore, the specific implementation method for determining the source-end dynamic compensation voltage based on the cumulative voltage drop and the preset end target voltage is as follows: the preset end target voltage... Add compensation coefficient With the cumulative voltage drop at the end The product of these two values ​​yields the source-side dynamic compensation voltage. The initial value of the compensation coefficient is 1.

[0104] ;

[0105] in, This is the source-end dynamic compensation voltage, in V; The preset target voltage for the end is usually set between 95% and 100% of the rated operating voltage of the street light, in volts (V). The compensation coefficient (dimensionless), initial value ; This represents the cumulative voltage drop at the end node, expressed in volts (V).

[0106] Dynamic compensation voltage at the source end Superimposed preset voltage margin This is used to address uncertainties not considered in the model, such as contact resistance at cable connections, differences in the input voltage adaptability of the street light driver power supply, and deviations between the actual and designed cable lengths during construction. Voltage margin Based on the total length of the branch line Multiply by the nominal resistance per unit length of the cable at the reference temperature. Multiply by 2, then multiply by the rated total current of the branch line. preset ratio coefficient OK, the expression is as follows:

[0107] ;

[0108] in, This is the voltage margin, measured in volts (V). The total length of the branch line. The unit is meters (m). This is the nominal resistance per unit length of the cable at a reference temperature, in units of... ; This is the rated total current of the branch line, in amperes (A). This is a preset proportionality coefficient (dimensionless), which is usually taken from engineering experience. The final source-side dynamic compensation voltage is and sum.

[0109] refer to Figure 2 As shown, the principle of dynamic temperature correction and voltage recursive modeling for cable resistance begins with the acquisition of ambient temperature and cable surface temperature. The estimated conductor temperature is obtained through thermal resistance coefficient conversion, and then the dynamic resistance value of each cable segment is obtained through temperature coefficient correction. The power adjustment ratio and rated power of each street light node determine the current load power of each street light. The load power divided by the actual operating voltage yields the load current. All load currents and cable resistances are fed into the recursive model, calculating the cumulative voltage drop of each node step by step from the beginning, and finally outputting the cumulative voltage drop of the end node.

[0110] Furthermore, the specific implementation method for closed-loop adaptive correction of the compensation coefficient is as follows.

[0111] The actual operating voltage of the terminal street light node (the Nth node) is collected and denoted as . The voltage is typically provided by a voltage sensor installed at the streetlight location or by the voltage monitoring function built into the streetlight driver. The streetlight driver usually integrates an input voltage detection circuit, which can read the effective value of the input AC voltage or the DC voltage value, and upload the voltage data to the central controller via a communication link.

[0112] Calculate the actual operating voltage at the terminal With the target voltage at the end The difference is used to obtain the voltage deviation e(t):

[0113] ;

[0114] in, The current sampling time The voltage deviation, in V; The terminal target voltage is expressed in volts (V). This represents the actual operating voltage at the terminal measured at the current sampling time t, in V.

[0115] The preset correction condition is: when the absolute value of the voltage deviation... Exceeding the preset voltage deviation threshold Furthermore, this deviation continues for more than a preset duration threshold. When this occurs, closed-loop adaptive correction of the compensation coefficients is triggered. That is, the correction trigger condition is:

[0116] ;

[0117] in, To preset the voltage deviation threshold, it is usually taken as 2% to 5% of the target voltage at the end, in units of V; The preset duration threshold is typically set between 30 and 120 seconds, measured in seconds (s). For deviations that continue to exceed The cumulative time is expressed in seconds (s). Setting a duration threshold is to avoid frequent triggering of corrections due to instantaneous voltage fluctuations, such as voltage dips caused by the instantaneous current surge when a street light starts up, or short-term voltage spikes caused by lightning induction. These instantaneous phenomena do not require modification of the compensation coefficient to respond.

[0118] When the correction trigger condition is met, the closed-loop correction adopts an incremental method. Adjustment method is used. Calculate the change in deviation. That is, the voltage deviation at the current sampling time. Subtract the voltage deviation at the previous sampling time :

[0119] ;

[0120] in, This is the amount of deviation change, expressed in voltage (V). This represents the voltage deviation at the previous sampling time, in V.

[0121] Change in deviation Multiply by the preset scaling factor Obtain the proportional correction term; calculate the voltage deviation at the current sampling time. Multiply by the preset integral coefficient The integral correction term is obtained. The compensation coefficients from the previous correction are then... By adding the proportional and integral correction terms, we obtain the current corrected compensation coefficient. :

[0122] ;

[0123] in, The current sampling time Corrected compensation coefficient (dimensionless). The compensation coefficient (dimensionless) is the corrected value from the previous sampling time. This is a preset proportionality coefficient (dimensionless). This is a preset integral coefficient (dimensionless). The proportional term's function is to quickly respond to changes in the deviation trend; when the voltage deviation is increasing, the proportional term accelerates the adjustment of the compensation coefficient, and when the voltage deviation is decreasing, the proportional term slows down the adjustment speed. The integral term's function is to eliminate steady-state deviation; as long as the deviation exists, the integral term will continue to accumulate until the deviation reaches zero. Proportional coefficient. and integral coefficient The value needs to be adjusted based on the actual response characteristics of the system. An excessively large value can easily cause fluctuations in the compensation coefficient. Too large an amount can easily cause overshoot.

[0124] When the absolute value of the voltage deviation Exceeding the preset anti-saturation threshold When this occurs, it indicates an abnormal voltage fluctuation, such as a street light short-circuiting and causing a sudden drop in local voltage, or a loose cable connector causing a sudden increase in contact resistance. In this case, the continuous accumulation of the integral term may cause the compensation coefficient to exceed the reasonable range. After integral saturation, even if the deviation is eliminated, the compensation coefficient cannot return to the normal level. Therefore, when When the integral correction term is paused, only the proportional correction term is retained for correction: when hour: ,when hour: ,in, This is a preset anti-saturation threshold, expressed in volts (V), and is set to 7% of the target voltage by default. For a system with a target voltage of 220V, Approximately 15V. When the voltage deviation exceeds... When the deviation exceeds the maximum deviation range that may be caused by normal load fluctuations and temperature drift, it indicates that there may be a faulty load change or cable abnormality in the branch. At this point, continued accumulation of the integral term may cause the compensation coefficient to drift to an unreasonable range; therefore, integral correction is paused. It should be noted that... At least for Three times the normal value to avoid accidentally triggering the anti-saturation protection during normal calibration.

[0125] The current corrected compensation coefficient With the preset upper limit of the compensation coefficient and the lower limit of the compensation coefficient When the comparison exceeds the range, the corresponding boundary value is used to prevent the compensation coefficient from drifting to unreasonable extreme values ​​due to abnormal operating conditions.

[0126] ;

[0127] in, This is the preset upper limit of the compensation coefficient (dimensionless). This is the preset lower limit of the compensation coefficient (dimensionless).

[0128] The determination of the upper limit K_{max} and lower limit K_{min} of the compensation coefficient is carried out in two stages. The first stage is the initial power-on commissioning stage of the branch line, using the preset initial source voltage. Power supply, measure the actual operating voltage of each load node. and load current Simultaneously, the theoretical voltage of each node is calculated using a voltage recursion model. and theoretical pressure drop The actual voltage drop of each cable segment is inferred from the difference between the source output voltage and the actual operating voltage of each node. :

[0129] ;

[0130] in, For the first The actual voltage drop of the cable segment, in volts (V). ; This represents the actual operating voltage of the i-th node, in V.

[0131] The voltage drop ratio is obtained by calculating the ratio of the actual voltage drop of each cable segment to the theoretical voltage drop calculated by the voltage recursion model. :

[0132] ;

[0133] in, For the first Voltage drop ratio of cable segment (dimensionless). The first voltage recursive model calculated The theoretical pressure drop is expressed in V.

[0134] Take all The maximum value in is used as the upper limit of the compensation coefficient. The minimum value is used as the lower limit of the compensation coefficient. :

[0135] ;

[0136] ;

[0137] Where N is the total number of load nodes. The upper and lower limits set in this way reflect the maximum possible deviation range between the model and reality, which includes both the influence of model parameter errors and the influence of various uncertainties in the actual line.

[0138] In the second stage, during normal operation, as the number of corrections increases, the compensation coefficient gradually stabilizes within a small fluctuation range. This is achieved when the compensation coefficient correction is less than the preset dead zone threshold for M=5 consecutive sampling periods. That is, for ,satisfy When this occurs, it indicates that the compensation coefficients have converged, and the current corrected compensation coefficients are used. Centered on the target, according to the preset proportion That is, expanding by 5% both upwards and downwards to obtain the updated upper limit of the compensation coefficient. and lower limit :

[0139] ;

[0140] ;

[0141] in, That is, it expands by 5% both vertically and horizontally.

[0142] As operational data accumulates, the correction range of the compensation coefficient becomes narrower, and the system's anti-interference capability becomes stronger. If the compensation coefficient after a correction exceeds the dynamically updated upper and lower limits, it indicates that the current operating condition has deviated significantly from the normal state, and the system can generate an early warning message to notify the maintenance personnel.

[0143] Furthermore, closed-loop compensation coefficient correction can also introduce a correction frequency limit. If the terminal voltage deviation frequently triggers the correction condition, it indicates that the system is in an unstable state. This may be due to large fluctuations in the output voltage of the source power supply or intermittent load changes in the branch. High-frequency correction will actually exacerbate system oscillations because each correction causes a change in the source output voltage, which in turn affects the terminal voltage, triggering the next correction and creating positive feedback oscillations. A minimum correction interval should be set. The time interval between two calibrations must not be less than this set value, typically 2 to 5 minutes. During the calibration interval, even if the calibration trigger condition is met, calibration will not be performed; only voltage deviation data will be recorded for subsequent statistical analysis. If the voltage deviation continues to increase within the calibration interval and exceeds a higher-level emergency threshold, calibration will be performed immediately, regardless of the calibration interval.

[0144] Furthermore, the specific implementation method for locally recursively recalculating the cumulative voltage drop of the changing node and its downstream nodes is as follows.

[0145] When the load power of a street light node in a branch line changes (the change may be due to the central controller adjusting the power adjustment ratio of that street light according to the time of day, traffic flow, or weather conditions, or it may be due to an abnormality in the driver power supply of that street light causing the actual power consumption to deviate from the set value), the cumulative voltage drop of each node needs to be recalculated. The load power change detection method is: read the power adjustment ratio of each street light controller in each sampling period. And collect the actual input current of each street light. and actual operating voltage Calculate the actual load power. If it is DC, then:

[0146] ;

[0147] If it is for communication, then:

[0148] ;

[0149] If the current sampling period is Compared with the previous sampling period The absolute value of the difference exceeds the preset power change threshold. (For example, 5% of the rated power), that is:

[0150] ;

[0151] If the node's load power changes, it is determined that the node's load power has changed. In the event of communication delays or packet loss, if no data is received from a node for several consecutive sampling periods, the previous effective load power value for that node remains unchanged, and a communication anomaly warning is generated. After communication is restored, it is recommended to trigger a full-line recalculation.

[0152] When the load power of the kth load node is monitored When changes occur, the load current of that node is updated first. Since changes in the load current at node k alter the current in cable segments 1 through k, the cumulative voltage drop across nodes 1 through k needs to be recalculated. Specifically, starting from node zero at the branch end, the cumulative voltage drop across nodes 1 through k is updated recursively using the following formula:

[0153] ;

[0154] ;

[0155] ;

[0156] in, For nodes k+1 to N, if there are no other nodes between the k-th node and the end node where the load power changes simultaneously, then the current in each downstream cable segment remains unchanged, i.e.:

[0157] ;

[0158] Therefore, the pressure drop remains constant in each segment: The change in cumulative voltage drop at node k The cumulative voltage drop from node k+1 to node N is: If there are other nodes whose load power changes simultaneously between the k-th node and the terminal node, then starting from the k-th node, the cumulative voltage drop from the (k+1)-th to the N-th nodes is updated downstream based on the updated load current of each node. When k=1, the update is performed across the entire line starting from the zero-th node. The calculation starts from i=1 and continues until i=N.

[0159] If there are other nodes whose load power changes simultaneously between the k-th node and the terminal node, the load current of each changing node is updated synchronously, and the cumulative voltage drop of all changing nodes is updated in one local recursive recalculation. After the local recursive recalculation is completed, the updated cumulative voltage drop of the terminal node is compared. Cumulative voltage drop at the end nodes before recalculation If the absolute value of the difference between the two exceeds the preset recalculation threshold... hour:

[0160] ;

[0161] This indicates that there may be a non-negligible deviation between the local recalculation result and the full-line recalculation result (the deviation may originate from the accumulation of rounding errors during the local recursion process, or from undetected minor changes in the load current of certain nodes between the two recalculations). In this case, the system automatically switches to the full-line recursion method, recalculating the cumulative voltage drop of all nodes starting from the first node at the beginning, prioritizing accuracy. The preset recalculation threshold, in units of V, is typically taken as... Half of the value. If the difference is within the recalculation threshold, it means that the accuracy of the local recalculation is sufficient, and the result of the local recalculation is directly used to update the cumulative voltage drop at the end.

[0162] Furthermore, the specific implementation method for adjusting the source-end output voltage is as follows: update the source-end dynamic compensation voltage according to the corrected compensation coefficient. Next, the updated source-side dynamic compensation voltage will be compared with the current source-side output voltage. The difference is used as the total adjustment. :

[0163] ;

[0164] in, Total adjustment, in V; The updated source-side dynamic compensation voltage, in volts (V); This is the current source output voltage, in volts (V).

[0165] Total adjustment Adjust according to the preset maximum single step size Break it down into multiple adjustment steps, number of adjustment steps for:

[0166] ;

[0167] in, The total number of adjustment steps to be performed. Indicates rounding up; The preset maximum adjustment step size is typically 1% to 2% of the rated output voltage, expressed in volts (V). If the total adjustment amount cannot be divided by the maximum adjustment step size, the remaining adjustment amount is used for the last adjustment step; that is, the step size for the last adjustment step is:

[0168] ;

[0169] The maximum adjustment step size is determined by considering both the output response speed of the regulated power supply and the transient withstand capability of the street light driver power supply. A default value of 1.5% of the rated output voltage is used (e.g., approximately 3.3V for a rated output voltage of 220V). This step size setting prevents excessive voltage changes in a single step from triggering the driver power supply protection, while also ensuring high efficiency in adjustment. When the final voltage deviation is 7.5% of the target voltage, approximately five adjustment steps are required to achieve convergence. For longer branch lines with a total length exceeding 5 kilometers or more than 50 streetlights, the maximum adjustment step size is correspondingly reduced to within 1% of the rated output voltage to mitigate the risk of voltage overshoot caused by distributed capacitance and inductance in long-distance lines.

[0170] After each adjustment step, wait for the preset voltage stabilization time. (The voltage stabilization time should take into account the charging and discharging time of the distributed capacitance and inductance in the branch line, as well as the charging time of the input capacitor of the street light driver power supply, and is usually taken as 5 to 15 seconds.) Collect the actual operating voltage of the load node at the end of the branch line. Calculate voltage deviation This indicates that the compensation has been paid and the subsequent adjustment steps are terminated.

[0171] If, during the adjustment process, the actual operating voltage of any intermediate load node exceeds the preset overvoltage protection threshold, ( Typically, the voltage is taken as 105% to 110% of the rated voltage. The closer the node is to the beginning, the higher the operating voltage. During the process of raising the source output voltage, the beginning node is most likely to reach the overvoltage threshold first. In this case, the adjustment is paused and the voltage is returned to the source output voltage of the previous adjustment step. At the same time, this node is marked as an overvoltage node, and the node number, overvoltage occurrence time, and overvoltage voltage value are recorded. If the voltage at the end of the branch line still fails to reach the target voltage, the adjustment is paused and the voltage is returned to the source output voltage of the previous adjustment step. The voltage at the first end is already close to the overvoltage protection threshold. This indicates that the cable voltage drop is too large, and simply increasing the source voltage is no longer sufficient to meet the power supply requirements at the end. The system generates a dimming suggestion command, suggesting that the power adjustment ratio of some streetlights near the head end be appropriately reduced to reduce the total load current of the entire branch line, thereby reducing the cable voltage drop and indirectly improving the voltage at the end.

[0172] Furthermore, the specific implementation methods of the full-line recursive and half-line recursive recalculation strategies are as follows: In the first operating cycle after the branch line is initially powered on or restarted from a power outage, the cumulative voltage drop at each node is calculated using the full-line recursive method to determine the initial source-end output voltage, i.e., from... to Calculate all nodes by step-by-step recursion. Although the full-line recursion involves a large amount of computation, the data cache table is empty in the initial stage, and the local recursion lacks the cumulative voltage drop data of the upstream nodes as a starting point, so it can only start the full recursion from the beginning.

[0173] Subsequently, in all operating cycles except the first, the number of nodes that detected changes in load power is recorded as follows: The preset node ratio threshold is ( Typically, 30% of the total number of branch nodes N is taken. When this occurs, it indicates a large-scale dimming operation has taken place. Select the node with the smallest number from the changed nodes (i.e., the one closest to the beginning of the branch line), and record its number as [number missing]. Due to the first The load change of each node will alter the 1st to the 2nd node. The current in the cable segment is therefore updated recursively from node 0 at the beginning of the branch line to node 1 through 1. The cumulative voltage drop at the node is used to obtain the updated value. Then, with the first Node update cumulative voltage drop As the starting point of the recursion, the voltage recursion model only updates the voltage level downstream. Cumulative voltage drop to node N:

[0174] ;

[0175] Among them, the The current to the Nth cable segment is recalculated based on the updated load current at each node.

[0176] The semi-circuit recursive recalculation strikes a compromise between full-circuit recursion and partial recursion. When a large number of nodes change simultaneously, partial recursion degenerates into a computational burden close to that of full-circuit recursion. However, semi-circuit recursion can utilize the accumulated voltage drop data already calculated upstream of the recalculation starting point, avoiding recalculation from the beginning.

[0177] Node ratio threshold The value of 30% is determined as follows: when the number of changed nodes is less than 30%, the computational advantage of local recursion recalculation is obvious; when the number of changed nodes exceeds 30%, local recursion has covered most of the branch line area, and there are few remaining unchanged nodes. At this time, the additional computational cost of switching to half-line recursion is limited, but it can avoid the need for subsequent full-line verification due to the cumulative error of local recursion. During system initialization, the total length of the branches is used as a reference. The calculation capability of the controller is taken into account. For short branches with N < 15 nodes, Reduced to 25%.

[0178] refer to Figure 3 As shown, the process of closed-loop adaptive correction and local recursive recalculation of the compensation coefficient starts from the actual operating voltage at the acquisition end, calculates the deviation from the target voltage, and determines whether the correction trigger condition is met. If the condition is met, the proportional correction term and integral correction term are calculated, the anti-saturation condition is checked, the compensation coefficient is updated, and it is limited to the upper and lower limits. At the same time, the load power change is monitored. When the load change is detected, the location and number of the changed nodes are determined, and local recursive recalculation or full-line recursive recalculation is performed to update the cumulative voltage drop at the end and the dynamic compensation voltage at the source end.

[0179] refer to Figure 4 As shown, a branch line dynamic voltage drop compensation control system is used to implement the branch line dynamic voltage drop compensation control method of this application, comprising:

[0180] The parameter acquisition and correction module is used to acquire branch topology parameters and the current power adjustment ratio of each load node, collect the ambient temperature and cable surface temperature along the branch, and dynamically correct the cable resistance between adjacent nodes based on the thermal resistance coefficient and the cable resistance temperature coefficient.

[0181] The voltage recursion modeling module establishes a voltage recursion model from the beginning to the end of the branch node by load node based on the corrected cable resistance. It iteratively calculates the cumulative voltage drop at the end node of the branch based on the load current and actual operating voltage of each load node.

[0182] The compensation voltage calculation module is used to determine the source-end dynamic compensation voltage and add voltage margin based on the cumulative voltage drop and the preset end target voltage.

[0183] The terminal voltage feedback correction module is used to collect the actual operating voltage of the load node at the end of the branch line, compare it with the terminal target voltage, and perform closed-loop adaptive correction of the compensation coefficient when the voltage deviation meets the preset correction conditions. It also performs anti-saturation processing according to the magnitude of the deviation, and limits the corrected compensation coefficient to a dynamically updated preset range.

[0184] The source voltage regulation module is used to update the source dynamic compensation voltage according to the corrected compensation coefficient, adjust the source output voltage in a step-by-step manner, and perform backoff protection when overvoltage occurs. At the same time, it monitors the load power change and triggers full, partial or half line recursive recalculation.

[0185] The five modules mentioned above exchange information via a data bus: the parameter acquisition and correction module transmits the dynamically corrected cable resistance and the acquired power adjustment ratio to the voltage recursive modeling module; the voltage recursive modeling module transmits the cumulative voltage drop at the end to the compensation voltage calculation module; the end voltage feedback correction module feeds back the corrected compensation coefficient to the compensation voltage calculation module; the compensation voltage calculation module transmits the updated source-end dynamic compensation voltage to the source-end voltage regulation module; and the source-end voltage regulation module feeds back the load power change information to the voltage recursive modeling module to trigger local recalculation. The entire system operates cyclically with a preset sampling period. The selection of the sampling period needs to consider both the response speed to temperature changes and the processing capacity of the controller, and is typically between 10 and 60 seconds.

[0186] To facilitate understanding, the operation of the method described in this application will be illustrated below using a specific road lighting engineering scenario. This scenario is merely an example and does not constitute a limitation on the scope of protection of this application.

[0187] This embodiment illustrates the operation of the method described in this application using a specific road lighting project scenario. For example, a branch line of a streetlight on a city's outer ring expressway is approximately 3 kilometers long and contains 30 LED streetlights (N=30), each with a rated power of... Wattage, rated operating voltage 220V AC. Branch lines use copper core cable, cable specification 10 square millimeters, resistance per unit length at 20℃. Approximately Temperature coefficient of cable resistance The branch line originates from the distribution cabinet at the beginning of the line. Inside the cabinet is a three-phase regulated power supply with adjustable output voltage, ranging from 200V to 240V with an adjustment accuracy of 1V. Each streetlight integrates a dimming controller, which communicates with a centralized controller via power line carrier. The centralized controller, installed in the distribution cabinet, is responsible for issuing dimming commands and collecting operational data from each streetlight.

[0188] During the system installation and commissioning phase, the first step was to input the branch topology parameters and calibrate the cable temperature. The cable length from the distribution cabinet outlet to the first street light and between each adjacent street light was then manually measured using a measuring tape. The 30 lights consist of 30 cable segments, ranging in length from 30 meters to 150 meters. Meters. An ambient temperature sensor is installed next to the first-end distribution cabinet, on the 15th streetlight pole in the middle of the branch line, and on the 30th streetlight pole at the end. The sensors are protected with radiation shields to prevent direct sunlight from affecting measurement accuracy. A small section of the outer sheath is stripped at the midpoint of each cable segment, and the NTC temperature sensor is placed tightly against the inner insulation layer, secured with insulating tape, and then the outer sheath is replaced. The sensor cable is then led down the streetlight pole and connected to the temperature acquisition module inside the streetlight controller. The thermal resistance coefficient is measured in the laboratory. For calibration, a 10 square millimeter copper core cable of the same model was subjected to 20 sets of temperature and current combination tests in a constant temperature chamber, and the thermal resistance coefficient was obtained. .

[0189] During initial power-on testing, set the initial source output voltage. Volts, power adjustment ratio for all streetlights The system collects voltage and current data at each node. The measured voltage of the 30 streetlights gradually decreases from 218 volts at the beginning to 205 volts at the end, with the voltage at the end being 15 volts lower than the rated voltage. A voltage recursion model is used to calculate the theoretical voltage at each node and the voltage drop ratio at each segment. 30 The maximum value is 1.08 and the minimum value is 0.93, which are used as the upper limits of the compensation coefficient. and lower limit Initial value of compensation coefficient The value ranges of each control parameter and the exemplary values ​​in this embodiment are shown in Table 1 below:

[0190] Table 1 Example of Control Parameters

[0191]

[0192] The above value range is determined comprehensively based on the branch line length, the number of streetlights, load characteristics, and controller performance. Those skilled in the art can adjust it within the given range according to the actual situation.

[0193] For scenarios where the total length of branch lines exceeds 5 kilometers or the number of streetlights exceeds 50, the proportionality factor... The coefficient should be reduced accordingly to 0.3 to 0.4 to avoid oscillations in the compensation coefficient caused by long line delays; for short branch lines with a total length of less than 1 kilometer or fewer than 10 streetlights, the proportional coefficient should be adjusted accordingly. The proportionality coefficient can be appropriately increased to 0.6 to 0.8 to accelerate the response speed. and integral coefficient During the initial system debugging phase, further optimization can be achieved through online self-tuning. The tuning method is as follows: starting from the initial value, gradually increase the proportional coefficient until the terminal voltage exhibits constant-amplitude oscillations, record the oscillation period, and then calculate the final value according to the Ziegler-Nichols tuning rule. and .

[0194] Specifically, Ziegler-Nichols tuning starts from... , Begin. Gradually increase the increment by 0.1 each time. After each increase, wait for the branch to reach a stable state, and then observe the fluctuation of the terminal voltage. Increase to the critical proportionality coefficient At this point, the terminal voltage begins to exhibit constant-amplitude oscillations without decay; the oscillation period is the critical oscillation period. The measurements obtained in this embodiment , Seconds. According to the proportional-integral controller parameter calculation formula in the Ziegler-Nichols tuning rules, Pick 0.45 times (i.e.) ), = After adjustment =0.54 is compared with the empirical value of 0.5, and the smaller one, 0.5, is taken as the final value. ; after adjustment Comparing 0.014 with the empirical value of 0.1, we take 0.014, which has a weaker integral effect, as the final value. If the set value is... The corresponding integration time constant is much larger than ,but The above empirical values ​​are used as an upper limit to avoid the slow elimination of steady-state deviations due to excessively weak integral action.

[0195] After normal operation, at 10 PM one night, traffic flow decreased significantly. The central controller issued a dimming command according to the preset nighttime energy-saving strategy, adjusting the power ratio of the 10th to 20th streetlights on the branch line. From 100% to 70% (i.e.) =0.7, i=10,...,20), the remaining streetlights remain unchanged. =1.0 remains unchanged. The dimming command is sent lamp by lamp via power line carrier, and each lamp completes the dimming action within 1 second after receiving the command. After the dimming command is executed, the load power of the 10th lamp changes from 150 watts to 105 watts. The system detects the change in load power at node k=10 and triggers a local recursive recalculation. The cumulative voltage drop of the 9th lamp is used as the basis for this calculation. Starting from the 10th lamp, the recursive formula is used to recalculate downstream up to the 30th lamp, involving a total of 21 lamps from the 10th to the 30th. After recalculation, the cumulative voltage drop at the end is found to be... The voltage has been reduced by approximately 3V; the updated source-side dynamic compensation voltage has been adjusted. When the voltage drops from 235V to 232V, the total regulation is... , Step 1. The source output voltage starts at 235V and decreases in steps of 2V. After executing the first step, wait 10 seconds and detect the final voltage. , and target voltage deviation ,satisfy The subsequent adjustment steps are terminated, and the adjustment is completed in a total of only one step. From the issuance of the dimming command to the adjustment of the source voltage, the entire process takes about 12 seconds.

[0196] One day, the driver power supply of the 25th street light on the branch line malfunctioned, and the internal power factor correction circuit failed, causing the street light's actual power consumption to decrease. The power drifted from the rated 150W to approximately 180W. The terminal voltage feedback correction module detected the actual operating voltage at the terminal during multiple consecutive sampling cycles. Below target voltage Approximately 8V, that is ,Exceed and duration Seconds later, the compensation coefficient closed-loop correction is triggered. , , , , . Before calibration According to the formula Calculated After limiting comparison ,Pick After correction, the terminal voltage returned to near the target value. Simultaneously, the system compared the actual load current at each node. Compared to the expected load current, the 25th street light was found to be... The power is significantly too high, compared to the set power adjustment ratio. If there is a mismatch, the street light is marked as having an abnormal power status, and a maintenance reminder message is sent to the centralized management platform via power line carrier, including the street light number, the type of abnormality, and the time of the abnormality.

[0197] One evening at 7 PM, as sunset approached, the streetlights were turned on simultaneously according to a schedule, with all 30 streetlights going from a cold start of 0 power to full power at the same time. The branch line load current jumps instantaneously from 0 to approximately 20 amps at full load, and the cable voltage drop jumps from 0 to its maximum value of approximately 28V. During the first operating cycle, the system uses a recursive approach across the entire line to calculate the cumulative voltage drop at each node. Determine the initial source-end output voltage When the streetlights are first turned on, the LED chip temperature is low, the forward voltage is high, and the input power of the driver is slightly higher than the steady-state value. As the streetlights warm up and the chip temperature rises, the input power gradually drops back to the rated value. The system gradually adjusts the compensation coefficient through end-point feedback correction. After fine-tuning to the appropriate value, the source output voltage stabilized at 236V after three gradual adjustments, and the terminal voltage stabilized at 220V. Throughout the startup process, the terminal voltage adjusted from the initially low 210V to near the target value within about 2 minutes, without any obvious overshoot or oscillation, and the light output of the street light transitioned smoothly during the warm-up phase.

[0198] The above description is merely a preferred embodiment of this application. The scope of protection of this application is not limited to the above embodiments. All technical solutions falling within the scope of this application's concept are within the scope of protection of this application. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of this application should also be considered within the scope of protection of this application.

Claims

1. A method for dynamic voltage drop compensation and control of branch lines, characterized in that, include: Obtain the branch topology parameters and the current power adjustment ratio of each load node, collect the ambient temperature and cable surface temperature along the branch, dynamically correct the cable resistance between adjacent nodes based on the cable resistance temperature coefficient, and establish a voltage recursive model from the beginning to the end of the branch for each load node. Based on the voltage recursion model, the cumulative voltage drop at the end node of the branch line is calculated recursively according to the load current of each load node and the corrected cable resistance between adjacent nodes. The source end dynamic compensation voltage is determined according to the cumulative voltage drop and the preset end target voltage. The actual operating voltage of the load node at the end of the branch line is collected and compared with the target voltage at the end. When the voltage deviation meets the preset correction conditions, the compensation coefficient is subjected to closed-loop adaptive correction, and the corrected compensation coefficient is limited to the preset upper and lower limits. The source-end dynamic compensation voltage is updated according to the corrected compensation coefficient, and the source-end output voltage is adjusted to the updated source-end dynamic compensation voltage. When the load power of any load node in the branch is detected to change, the cumulative voltage drop of the changed node and its downstream nodes is locally recursively recalculated, starting from the changed node, and the source-end dynamic compensation voltage is updated.

2. The branch line dynamic voltage drop compensation and control method according to claim 1, characterized in that, The dynamic correction of cable resistance between adjacent nodes includes: Obtain the nominal value of the resistance per unit length of the cable at the reference temperature and the temperature coefficient of resistance of the cable; Calculate the difference between the cable surface temperature and the ambient temperature, multiply the difference by the preset thermal resistance coefficient from the cable surface to the internal conductor to obtain the conductor temperature rise, and add the ambient temperature to the conductor temperature rise to obtain the estimated conductor temperature. The thermal resistance coefficient is determined through offline calibration tests: under different combinations of ambient temperature and load current, thermocouples are used to simultaneously measure the surface temperature of the cable and the actual temperature of the internal conductor. The ratio between the difference between the actual conductor temperature and the surface temperature and the difference between the surface temperature and the ambient temperature is used as the thermal resistance coefficient of the measurement point. The average value of all measurement points is taken as the preset thermal resistance coefficient. The temperature difference is obtained by subtracting the reference temperature from the estimated temperature of the conductor. The temperature difference is then multiplied by the temperature coefficient of resistance of the cable and then by one, and finally multiplied by the nominal value to obtain the corrected resistance per unit length of the cable. Multiply the corrected resistance per unit length of the cable by the cable length between adjacent nodes to obtain the corrected cable resistance between adjacent nodes.

3. The branch line dynamic voltage drop compensation and control method according to claim 1, characterized in that, The recursive calculation of the cumulative voltage drop at the end node of the branch includes: The beginning of the branch line is designated as node zero, and the cumulative voltage drop at node zero is zero. For node i, where i takes values ​​from one to N, and N is the total number of load nodes in the branch, the voltage drop of the cable segment between node i-1 and node i is the current flowing through the cable segment multiplied by the corrected resistance of the cable segment and then multiplied by two. The current flowing through the cable segment is the sum of the load currents of all load nodes from node i to the end of the branch. The cumulative voltage drop of node i is equal to the cumulative voltage drop of node i-1 plus the voltage drop of the cable segment. The load current of each load node is obtained by dividing the load power of the node by the actual operating voltage of the node. The actual operating voltage is obtained by subtracting the cumulative voltage drop of the node from the source output voltage. When the cumulative voltage drop of the node has not yet been calculated, the preset initial value of the source output voltage is used as the actual operating voltage of the zeroth node for iterative approximation. Starting from node zero, the cumulative voltage drop at the end node of the branch is obtained by iterating step by step from node one to node N.

4. The branch line dynamic voltage drop compensation and control method according to claim 1, characterized in that, The step of determining the source-end dynamic compensation voltage based on the accumulated voltage drop and the preset end target voltage includes: The source-end dynamic compensation voltage is obtained by adding the product of the compensation coefficient and the cumulative voltage drop to the preset end target voltage, and the initial value of the compensation coefficient is one. A preset voltage margin is superimposed on the dynamic compensation voltage at the source end. The voltage margin is determined by multiplying the total length of the branch line by the nominal value of the resistance per unit length of the cable at the reference temperature, then by two, and then by a preset proportional coefficient of the rated total current of the branch line.

5. The branch line dynamic voltage drop compensation and control method according to claim 1, characterized in that, The closed-loop adaptive correction of the compensation coefficient includes: The voltage deviation at the current sampling time is subtracted from the voltage deviation at the previous sampling time to obtain the deviation change. The deviation change is multiplied by a preset proportional coefficient to obtain a proportional correction term. The voltage deviation at the current sampling time is multiplied by a preset integral coefficient to obtain an integral correction term. The compensation coefficient after the previous correction is added to the proportional correction term and the integral correction term to obtain the compensation coefficient after the current correction. When the absolute value of the voltage deviation exceeds the preset anti-saturation threshold, the accumulation of the integral correction term is paused, and only the proportional correction term is retained for correction. The current corrected compensation coefficient is compared with the preset upper and lower limits of the compensation coefficient. If it exceeds the range, the corresponding boundary value is taken.

6. The branch line dynamic voltage drop compensation and control method according to claim 5, characterized in that, The upper and lower limits of the compensation coefficient are determined as follows: During the initial power-on commissioning phase of the branch line, the power supply is powered by the preset initial source voltage. The actual operating voltage and load current of each load node are measured. The actual voltage drop of each cable segment is inferred from the difference between the source output voltage and the actual operating voltage of each node. The maximum value of the ratio of the actual voltage drop of each segment to the voltage drop of the corresponding segment calculated by the voltage recursion model is used as the upper limit of the compensation coefficient, and the minimum value is used as the lower limit of the compensation coefficient. After normal operation, when the compensation coefficient correction amount is less than the preset dead zone threshold for multiple consecutive sampling periods, the updated upper and lower limits of the compensation coefficient are obtained by expanding the current corrected compensation coefficient as the center according to the preset ratio.

7. The branch line dynamic voltage drop compensation and control method according to claim 1, characterized in that, The local recursive recalculation of the cumulative voltage drop at the changing node and its downstream nodes includes: When a change in the load power of the kth load node is detected, the load current of the node with the change is updated. The current change of the cable from the 1st to the kth segment is calculated based on the updated load current, and the cumulative voltage drop of the 1st to the kth node is updated accordingly. Starting from the kth node, the cumulative voltage drop of the (k+1)th to the Nth node is updated recursively. When k equals 1, the recursion starts from the zeroth node and proceeds along the entire line. If there are other nodes whose load power changes simultaneously between the k-th node and the end node, the load current of each node that changes will be updated synchronously, and the cumulative voltage drop of all nodes that change will be updated in one recalculation. After the recalculation is completed, the cumulative voltage drop of the updated end node is compared with the cumulative voltage drop of the end node before the recalculation. If the absolute value of the difference between the two exceeds the preset recalculation threshold, the cumulative voltage drop of all nodes is recalculated using the full-line recursive method.

8. The branch line dynamic voltage drop compensation and control method according to claim 1, characterized in that, Adjusting the source output voltage includes: The difference between the updated source-end dynamic compensation voltage and the current source-end output voltage is used as the total adjustment amount, and the total adjustment amount is divided into multiple adjustment steps according to the preset single maximum adjustment step size. After each adjustment step, wait for a preset voltage stabilization time, collect the actual operating voltage of the load node at the end of the branch line, and if the absolute value of the deviation between the actual operating voltage and the target voltage at the end does not exceed the preset voltage deviation threshold, then terminate the subsequent adjustment steps. If, during the execution of the adjustment step, the actual operating voltage of any intermediate load node is detected to exceed the preset overvoltage protection threshold, the adjustment is paused and reverted to the source output voltage of the previous adjustment step, and the node is marked.

9. The branch line dynamic voltage drop compensation and control method according to claim 1, characterized in that, In the first operating cycle after the branch line is first powered on or restarted, the cumulative voltage drop of each node is calculated and the initial source output voltage is determined by the full-line recursive method. In subsequent operating cycles other than the first operating cycle, when the number of nodes with load power changes exceeds the preset node proportion threshold, the node closest to the beginning of the branch line is selected from the changed nodes and recorded as the k_min changed node. The cumulative voltage drop of the nodes from the 1st to the k_minth nodes is updated step by step starting from the zeroth node at the beginning of the branch line. Starting from the updated cumulative voltage drop at node k_min, the voltage recursion model is used to update the cumulative voltage drop from node k_min+1 to node N downstream.

10. A branch line dynamic voltage drop compensation and control system, used to implement the branch line dynamic voltage drop compensation and control method as described in any one of claims 1 to 9, characterized in that, include: The parameter acquisition and correction module is used to acquire branch topology parameters and the current power adjustment ratio of each load node, collect the ambient temperature and cable surface temperature along the branch, and dynamically correct the cable resistance between adjacent nodes based on the thermal resistance coefficient and the cable resistance temperature coefficient. The voltage recursion modeling module establishes a voltage recursion model from the beginning to the end of the branch node by load node based on the corrected cable resistance. It iteratively calculates the cumulative voltage drop at the end node of the branch based on the load current and actual operating voltage of each load node. The compensation voltage calculation module is used to determine the source-end dynamic compensation voltage and add voltage margin based on the cumulative voltage drop and the preset end target voltage; The terminal voltage feedback correction module is used to collect the actual operating voltage of the load node at the end of the branch line, compare it with the terminal target voltage, and perform closed-loop adaptive correction of the compensation coefficient when the voltage deviation meets the preset correction conditions. It also performs anti-saturation processing according to the magnitude of the deviation, and limits the corrected compensation coefficient to a dynamically updated preset range. The source voltage regulation module is used to update the source dynamic compensation voltage according to the corrected compensation coefficient, adjust the source output voltage in a step-by-step manner, and perform backoff protection when overvoltage occurs. At the same time, it monitors the load power change and triggers full, partial or half line recursive recalculation.

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