A power distribution box control method and device and a power distribution box

Abstract

The application discloses a kind of distribution box control method, device and distribution box, it is related to distribution box control technical field, it aims at solving the problem of rapid voltage flicker and steady-state drop that appears when distributed photovoltaic power generation system and high-power nonlinear charging load are accessed distribution area, the application provides the distribution box control method of the present application, the deviation voltage of bus line voltage and reference voltage is determined, and is decomposed into high-frequency and low-frequency deviation voltage, then based on high-frequency deviation voltage control series voltage stabilizer action, realize fast dynamic voltage compensation;Based on the switching control of low-frequency deviation voltage to shunt capacitor group, realize the steady-state reactive power compensation of large capacity.It can be seen that the distribution box control method provided by the present application takes into account fast dynamic voltage compensation and steady-state reactive power compensation, effectively improves the power quality management ability of distribution area, and improves the power quality problem of distribution area under complex working conditions.

Description

Technical Field

[0001] This invention relates to the field of distribution box control technology, and in particular to a distribution box control method, device and distribution box. Background Technology

[0002] Distribution substations are a crucial link in low-voltage power distribution, and integrated distribution boxes (JP cabinets) are the core equipment in these substations, integrating functions such as power distribution, metering, protection, and reactive power compensation. In recent years, with the continuous advancement of new power system construction, power quality issues in distribution substations have become increasingly prominent, mainly due to the large-scale integration of distributed photovoltaic (PV) power generation systems and the stochastic increase in electric vehicle (EV) charging loads. Distributed PV power generation systems are highly intermittent and susceptible to environmental fluctuations; their large-scale integration into distribution substations easily leads to voltage exceeding limits and rapid voltage flicker. The stochastic increase in nonlinear, high-power charging loads such as EVs causes steady-state voltage drops during peak electricity consumption periods and exacerbates three-phase load imbalance. Solving these power quality problems in distribution substations is a technical challenge currently requiring expertise. Summary of the Invention

[0003] The purpose of this invention is to provide a distribution box control method, device, and distribution box, which aims to solve the problems of voltage over-limit and rapid voltage flicker caused when a distributed photovoltaic power generation system is connected to a distribution transformer area, as well as the problem of steady-state voltage drop caused when a high-power nonlinear charging load is connected to a distribution transformer area, and to cope with the increasingly complex voltage fluctuations and bidirectional voltage over-limit conditions in the distribution transformer area.

[0004] To solve the above-mentioned technical problems, the present invention provides a distribution box control method, wherein a capacitor bank is connected in parallel on the busbar of the distribution box and a voltage regulator is connected in series. The distribution box control method includes: Determine the deviation voltage of the busbar at the incoming end of the distribution box. The deviation voltage represents the deviation between the line voltage of the busbar and the preset reference voltage. Determine the high-frequency deviation voltage and the low-frequency deviation voltage based on the deviation voltage; The voltage regulator is controlled by high-frequency deviation voltage to provide rapid dynamic voltage compensation for the bus. The switching control of capacitors in the capacitor bank is based on low-frequency deviation voltage to perform steady-state reactive power compensation for the bus.

[0005] Optionally, the deviation voltage of the busbar at the incoming end of the distribution box is determined, including: Obtain the three-phase line voltage of the busbar; Determine the average value of the line voltage; The deviation voltage is determined based on the average value and the preset reference voltage.

[0006] Optionally, determining the high-frequency deviation voltage and the low-frequency deviation voltage based on the deviation voltage includes: The deviation voltage is low-pass filtered to obtain the low-frequency deviation voltage; The high-frequency deviation voltage is determined based on the deviation voltage and the low-frequency deviation voltage.

[0007] Optionally, the operation of the voltage regulator is controlled based on high-frequency deviation voltage to provide rapid dynamic voltage compensation for the bus, including: If the absolute value of the high-frequency deviation voltage is greater than the preset high-frequency disturbance threshold, the series compensation voltage is determined based on the high-frequency deviation voltage, and the voltage regulator is controlled to output the series compensation voltage. If the absolute value of the high-frequency deviation voltage is less than or equal to the preset high-frequency disturbance threshold, the voltage regulator will maintain its current output state.

[0008] Optionally, the series compensation voltage is determined based on the high-frequency deviation voltage, including: Based on the high-frequency deviation voltage, the corresponding proportional control component and integral control component are determined by proportional and integral operations, respectively. The series compensation voltage is determined based on the proportional and integral control components.

[0009] Optionally, the switching control of capacitors in the capacitor bank is performed based on the low-frequency deviation voltage to provide steady-state reactive power compensation for the bus, including: If the absolute value of the low-frequency deviation voltage is greater than the preset steady-state deviation threshold and the duration is greater than the first preset time threshold, then the capacitor bank is controlled to switch based on the low-frequency deviation voltage. If the absolute value of the low-frequency deviation voltage is not greater than the preset steady-state deviation threshold, or the duration is not greater than the first preset time threshold, then the control capacitor bank will maintain its current operating state.

[0010] Optionally, the switching action of the capacitor bank is controlled based on the low-frequency deviation voltage, including: The number of capacitors operating in the capacitor bank is determined based on the polarity and amplitude of the low-frequency deviation voltage, and the operation of the determined capacitors is controlled. Specifically, when the polarity of the low-frequency deviation voltage is positive, the action is to cut off; when the polarity of the low-frequency deviation voltage is negative, the action is to engage. When the number is greater than or equal to 2, the action interval between any two adjacent capacitors shall not be less than the second preset time threshold.

[0011] Optional, also includes: Obtain the three-phase voltage imbalance of the busbar; When the three-phase voltage imbalance exceeds the preset imbalance threshold, the control regulator independently adjusts the voltage of each phase to reduce the voltage deviation between phases.

[0012] To address the above problems, the present invention also provides a distribution box control device, comprising: Memory, used to store computer programs; A processor is used to execute computer programs to implement the distribution box control method described above.

[0013] To address the aforementioned problems, the present invention also provides a distribution box, including a voltage stabilizer and at least one set of capacitor banks, and further including the distribution box control device as described above; wherein the voltage stabilizer is connected in series with the three-phase AC bus of the distribution box, and the capacitor banks are connected in parallel with the three-phase AC bus.

[0014] This invention provides a control method for a distribution box. It determines the voltage deviation between the bus voltage and a reference voltage, and then determines high-frequency and low-frequency deviation voltages based on this deviation. Based on this, it controls the operation of a series-connected voltage regulator based on the high-frequency deviation voltage to provide rapid dynamic voltage compensation to the distribution box bus, effectively suppressing voltage flicker and high-frequency disturbances caused by distributed photovoltaic systems. Simultaneously, it controls the switching of parallel capacitor banks based on the low-frequency deviation voltage to provide steady-state reactive power compensation to the bus, compensating for steady-state voltage drops and reactive power demands caused by the random connection of large-capacity charging loads. Therefore, the distribution box control method provided by this invention, by determining the high-frequency and low-frequency deviation voltages separately, and then coordinating the control of the voltage regulator and capacitor banks based on these voltage deviations respectively, balances rapid dynamic voltage compensation and steady-state reactive power compensation, effectively improving the power quality management capabilities of the distribution area and addressing power quality issues in complex operating conditions.

[0015] The present invention also provides a distribution box control device and a distribution box, both of which have the same beneficial effects as the above-mentioned distribution box control method. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart of a distribution box control method provided by the present invention; Figure 2 A flowchart of another distribution box control method provided by the present invention; Figure 3 A flowchart of another distribution box control method provided by the present invention; Figure 4A structural diagram of a voltage regulator provided by the present invention; Figure 5 A structural diagram of a capacitor bank provided by the present invention; Figure 6 A structural diagram of an AC / AC converter provided by the present invention; Figure 7 This invention provides a structural diagram of a power distribution box control device; Figure 8 A structural diagram of a distribution box provided by the present invention; Figure 9 This invention provides an internal layout diagram of a power distribution box. Detailed Implementation

[0018] The core of this invention is to provide a distribution box control method, device, and distribution box, which aims to achieve coordinated management of dynamic voltage disturbances and steady-state voltage deviations in the distribution area, and comprehensively improve the voltage stability and power supply quality of the distribution system.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a control method for a distribution box, such as... Figure 1 As shown, Figure 1 The flowchart illustrates a distribution box control method provided by this invention. A capacitor bank is connected in parallel to the busbar of the distribution box, and a voltage regulator is connected in series. The distribution box control method includes: S11. Determine the deviation voltage of the busbar at the incoming end of the distribution box. The deviation voltage represents the deviation between the line voltage of the busbar and the preset reference voltage. First, it should be noted that the distribution box involved in this embodiment is equipped with a voltage regulator and at least one set of capacitor banks. The capacitor banks are connected in parallel to the three-phase AC bus, and the voltage regulator is connected in series to the three-phase AC bus. The voltage regulator can preferably be a solid-state voltage regulator. In order to obtain accurate real-time voltage signals from the power grid side, the voltage sampling point is preferably set after the metering unit of the distribution box and before the voltage regulator and capacitor banks for feedforward sampling.

[0021] Before addressing voltage disturbances, it is essential to quantify the actual voltage operating state of the power grid, i.e., determine the degree to which the current grid voltage deviates from its rated voltage. The aforementioned sampling point location settings enable this method to acquire the true, original voltage fluctuations on the power grid side, avoiding interference from compensation actions on the sampling results.

[0022] Based on this, the distribution box control device acquires the three-phase line voltages Uab(t), Ubc(t), and Uca(t) after the metering unit in real time with a preset sampling period (e.g., 10kHz), and calculates the average value of the three-phase line voltages; then, it calculates the difference between the average value of the three-phase line voltages and the preset reference voltage (usually 380V) to obtain the deviation voltage characterizing the current voltage fluctuation.

[0023] The above steps can accurately and in real time quantify the voltage over-limit and fluctuation of the bus, providing a data foundation for further identification of voltage disturbance types and the implementation of hierarchical coordinated control of the voltage regulator and capacitor bank.

[0024] S12. Determine the high-frequency deviation voltage and low-frequency deviation voltage based on the deviation voltage; Considering that capacitor banks typically have a slow response and cannot cope with voltage flicker on the order of minutes or seconds caused by photovoltaic fluctuations, while separately configured voltage regulators are too expensive and cannot handle large-capacity steady-state reactive power compensation, in order to enable voltage regulators and capacitor banks to work together to solve the corresponding problems mentioned above, it is necessary to decompose the frequency domain characteristics of the deviation voltage.

[0025] Specifically, the distribution box control device can filter the obtained deviation voltage. For example, it can use a first-order low-pass filter to filter the deviation voltage, extract the low-frequency deviation voltage, and subtract this low-frequency deviation voltage from the original deviation voltage to calculate the high-frequency deviation voltage. The high-frequency deviation voltage typically corresponds to voltage fluctuations on the order of seconds to minutes, such as voltage flicker caused by fluctuations in distributed photovoltaic power generation. The low-frequency deviation voltage typically corresponds to sustained voltage deviations, such as voltage drops caused by significant changes in the load of the distribution area. Through these steps, the deviation voltage, which is a mixture of different types of fluctuations, can be successfully separated into the high-frequency deviation voltage corresponding to rapid flicker and the low-frequency deviation voltage corresponding to steady-state drops. This provides a data foundation for the subsequent rational allocation of compensation requirements to hardware with different response characteristics.

[0026] S13. Based on the high-frequency deviation voltage control regulator operation, the busbar is rapidly and dynamically compensated. Considering that high-frequency disturbances often have the characteristics of rapid amplitude changes and short duration, high-frequency voltage compensation is undertaken by voltage regulators with fast response speed.

[0027] Specifically, the system determines whether the absolute value of the high-frequency deviation voltage exceeds a preset high-frequency disturbance threshold (e.g., 3% of the rated line voltage of 380V, i.e., 11.4V). If it does, the distribution box control device drives the voltage regulator to operate, outputting the corresponding series compensation voltage to provide rapid dynamic voltage compensation to the bus. These steps fully utilize the voltage regulator's rapid response characteristics, enabling the distribution box to quickly address high-frequency voltage flicker issues.

[0028] S14. Based on the low-frequency deviation voltage, the capacitors in the capacitor bank are switched on and off to perform steady-state reactive power compensation for the bus.

[0029] Considering that steady-state voltage deviations typically last for a long time and require a large compensation capacity, voltage compensation using parallel capacitor banks can effectively control the overall cost of the distribution box renovation while ensuring the effectiveness of steady-state control.

[0030] Specifically, it is determined whether the absolute value of the low-frequency deviation voltage exceeds a preset steady-state deviation threshold (e.g., 7% of the rated line voltage of 380V, i.e., 26.6V) and whether the duration exceeds a preset time threshold (e.g., 20 seconds). If the switching condition is met, a corresponding switching command (i.e., positive bias cut off, negative bias on) is issued to the capacitor bank containing multiple capacitor banks and corresponding switching switches according to the sign of the low-frequency deviation voltage, controlling the connection or disconnection of the capacitors, thereby providing steady-state reactive power compensation to the busbar of the distribution box. Through the above steps, long-term and large-capacity steady-state deviations can be mitigated. Furthermore, since high-frequency disturbances have been isolated, unnecessary frequent switching of capacitor banks following high-frequency flicker is avoided, effectively extending the hardware lifespan of the capacitor banks.

[0031] As can be seen, the distribution box control method provided in this embodiment, through frequency domain decomposition of voltage fluctuations, effectively reduces the number of capacitor bank switching operations while meeting the requirements for rapid response to high-frequency disturbances. This achieves complementary functional advantages between the voltage regulator and the capacitor bank, resulting in a comprehensive improvement in the overall power quality of the distribution area. Verification has shown that the coordinated operation of the voltage regulator and the capacitor bank can continuously stabilize the bus voltage of the distribution area within ±3% of the rated voltage, ensuring both response speed and cost-effectiveness.

[0032] Based on the above embodiments: As an optional embodiment, determining the deviation voltage of the busbar at the incoming end of the distribution box includes: Obtain the three-phase line voltage of the busbar; Determine the average value of the line voltage; The deviation voltage is determined based on the average value and the preset reference voltage.

[0033] In the actual operation of the distribution box, it is necessary to accurately quantify the real voltage state on the grid side to assess the voltage deviation from the rated voltage in order to further implement precise voltage compensation control.

[0034] Based on this, the distribution box control device acquires the three-phase line voltages Uab(t), Ubc(t), and Uca(t) of the bus in real time with a preset sampling period (e.g., a sampling rate of 10kHz); then it calculates the average value Uavg(t) of these three line voltages; subsequently, it calculates the deviation voltage ΔU(t) using the formula ΔU(t) = Uavg(t) - Uref, where Uavg(t) is the average value of the three line voltages, and Uref is a preset reference voltage (e.g., a rated line voltage of 380V). The deviation voltage obtained through the above process can accurately quantify the degree of voltage exceedance and fluctuation of the bus, providing a data basis for subsequent frequency domain decomposition and coordinated control.

[0035] It should be noted that, in order to obtain accurate real-time voltage signals from the power grid, the aforementioned voltage sampling points are specifically set after the metering unit of the distribution box and before the voltage regulator and capacitor bank. This allows the distribution box control device to obtain the true original voltage situation on the power grid side, avoiding interference from the subsequent compensation actions of the voltage regulator and capacitor bank on the front-end sampling results.

[0036] As can be seen, the deviation voltage determination method provided in this embodiment effectively eliminates the interference of single-phase local voltage fluctuations by reasonably setting sampling points and using the calculation method of the average value of three-phase line voltages. It can objectively reflect the true voltage state of the busbar of the distribution box, and provide a reliable data basis for subsequent frequency domain decomposition and coordinated control.

[0037] As an optional embodiment, determining the high-frequency deviation voltage and the low-frequency deviation voltage based on the deviation voltage includes: The deviation voltage is low-pass filtered to obtain the low-frequency deviation voltage; The high-frequency deviation voltage is determined based on the deviation voltage and the low-frequency deviation voltage.

[0038] Considering that voltage fluctuations in the power grid are usually caused by the superposition of different factors, such as distributed photovoltaic fluctuations or load surges that can cause high-frequency voltage disturbances, while the continuous connection of large-capacity loads can lead to low-frequency voltage drops.

[0039] Therefore, to avoid mutual interference between voltage regulators and capacitor banks with different response speeds within the distribution box, the distribution box control device uses a digital low-pass filter to filter the calculated deviation voltage, extracting the slowly changing low-frequency component as the low-frequency deviation voltage. Subsequently, the distribution box control device subtracts this low-frequency deviation voltage from the overall deviation voltage to calculate the rapidly changing high-frequency component as the high-frequency deviation voltage. This frequency domain decomposition process effectively separates the deviation voltage, which contains a mixture of different types of fluctuations, providing a data basis for the subsequent rational allocation of compensation requirements to voltage regulators and capacitor banks with corresponding physical characteristics.

[0040] It should be noted that the filtering process in this embodiment can be implemented using a first-order digital low-pass filter. The cutoff frequency of this filter can be set between 5 Hz and 20 Hz, preferably 10 Hz. Specifically, it can be calculated using the following formula: ; Where ΔU_L[k] is the low-frequency deviation voltage of the current cycle; α is the filter coefficient, and for a first-order digital low-pass filter with a sampling rate of 10kHz, α is 0.00628; ΔU_L[k-1] is the low-frequency deviation voltage of the previous cycle.

[0041] Those skilled in the art can pre-select a suitable filter based on the power quality characteristics of the actual distribution area and adaptively adjust the above-mentioned filter coefficients; this embodiment does not impose any limitations on this.

[0042] As can be seen, the frequency domain decomposition method provided in this embodiment effectively extracts the voltage fluctuation characteristics of different frequency bands through a low-pass filtering algorithm, providing an accurate data foundation for the hybrid compensation and coordinated control of the distribution box.

[0043] As an optional embodiment, the deviation voltage is low-pass filtered to obtain a low-frequency deviation voltage, including: Determine the frequency of occurrences where the absolute value of the high-frequency deviation voltage exceeds the preset high-frequency disturbance threshold within a preset time period; When the frequency of occurrence exceeds the preset frequency threshold, the cutoff frequency of the low-pass filter is increased, and the deviation voltage is low-pass filtered based on the adjusted cutoff frequency.

[0044] Considering the differences in load characteristics and external environment among different distribution substations, such as the tendency for dense second-level fluctuations to occur in distribution substations with a large number of photovoltaic connections, while distribution substations with pure industrial loads are mainly characterized by large-capacity load drops, if a filter with a fixed cutoff frequency is used for frequency domain decomposition, misjudgment may occur, thereby triggering meaningless switching of mechanical capacitor banks.

[0045] Based on this, the distribution box control device can use a sliding time window (e.g., the past hour) as a preset time period to count the frequency of high-frequency disturbances occurring on the bus within that period in real time. When this frequency exceeds a preset frequency threshold, it is determined that the current distribution area is under severe fluctuation conditions. This frequency threshold characterizes the intensity of severe voltage fluctuations experienced by the distribution area within the current time window, and is used to determine whether the system is under complex and severe grid disturbance conditions. The control device then adjusts the cutoff frequency of the digital low-pass filter in the program (e.g., dynamically increasing it from the basic 10Hz to 15Hz) and updates the corresponding filter coefficients simultaneously. By increasing the cutoff frequency, more voltage fluctuations in the mid-to-high frequency range can be classified as high-frequency deviation voltages.

[0046] It should be noted that by classifying more voltage fluctuations as high-frequency components, the action will be performed by a voltage regulator with millisecond-level response and no mechanical wear, thereby preventing the capacitor bank from being erroneously activated.

[0047] As can be seen, the frequency domain decomposition method provided in this embodiment effectively improves the adaptability of this method to complex power grid environments and extends the service life of capacitor banks by adaptively adjusting the high and low frequency boundaries based on the fluctuation density in the actual operating conditions of the power grid.

[0048] As an optional embodiment, such as Figure 2 As shown, Figure 2 A flowchart of another distribution box control method provided by the present invention. Based on high-frequency deviation voltage control, the voltage regulator is activated to perform rapid dynamic voltage compensation on the busbar, including: S24. If the absolute value of the high-frequency deviation voltage is greater than the preset high-frequency disturbance threshold, the series compensation voltage is determined based on the high-frequency deviation voltage, and the voltage regulator is controlled to output the series compensation voltage. S25. If the absolute value of the high-frequency deviation voltage is less than or equal to the preset high-frequency disturbance threshold, the voltage regulator is controlled to maintain the current output state.

[0049] Considering that high-frequency voltage disturbances often exhibit rapid amplitude changes and short durations, such as minute- or second-level voltage flicker caused by rapid photovoltaic fluctuations or load surges, voltage regulators, with their fast-response physical characteristics, are suitable for dynamic compensation against voltage flicker. Figure 4 As shown, Figure 4 A structural diagram of a voltage regulator provided by the present invention.

[0050] Based on this, the distribution box control device first determines whether the absolute value of the calculated high-frequency deviation voltage is greater than a preset high-frequency disturbance threshold. This high-frequency disturbance threshold represents the voltage boundary between normal grid fluctuations and voltage flicker requiring voltage regulator intervention, and can preferably be set to 3% of the rated voltage (for example, for a rated voltage of 380V, it can preferably be 11.4V). If the absolute value of the high-frequency deviation voltage is greater than this high-frequency disturbance threshold, the distribution box control device can drive the voltage regulator to operate within milliseconds. Based on the high-frequency deviation voltage, the corresponding series compensation voltage is determined using the series compensation voltage calculation formula, and the voltage regulator is controlled to output this series compensation voltage to perform rapid dynamic voltage compensation on the bus. If the absolute value of the high-frequency deviation voltage is less than or equal to the high-frequency disturbance threshold, it indicates that the current high-frequency fluctuation is within the allowable range. At this time, the distribution box control device controls the voltage regulator to maintain the current output state without performing additional voltage intervention. Through the above process, the advantage of the voltage regulator's millisecond-level response can be fully utilized, and voltage flicker can be quickly suppressed while avoiding invalid hardware actions.

[0051] It should be noted that, in order to prevent the voltage regulator from frequently operating near the critical voltage point, the control device of the distribution box can be equipped with anti-oscillation redundancy logic. That is, there is a difference between the start and stop conditions of the control action. For example, when the absolute value of the high-frequency deviation voltage is greater than 11.4V, the compensation action is activated, and the action is stopped when the absolute value drops to less than 8V.

[0052] As can be seen, the control method provided in this embodiment achieves precise and rapid management of high-frequency disturbances such as voltage flicker by reasonably setting the high-frequency action boundary, while effectively avoiding the regulation oscillation problem of the voltage regulator.

[0053] As an optional embodiment, determining the series compensation voltage based on the high-frequency deviation voltage includes: Based on the high-frequency deviation voltage, the corresponding proportional control component and integral control component are determined by proportional and integral operations, respectively. The series compensation voltage is determined based on the proportional and integral control components.

[0054] When dealing with high-frequency voltage disturbances in distribution transformer areas, voltage regulators need to output voltage quickly and accurately to offset transient voltage drops or surges on the bus. If only proportional regulation is used, although the response is rapid, steady-state errors often remain in the actual physical circuit. If only integral regulation is used, although static errors can be gradually eliminated, there is a significant time lag in the response, which cannot meet the urgent need for millisecond-level dynamic compensation.

[0055] Based on this, the distribution box control device uses a proportional-integral control algorithm to determine the specific series compensation voltage. It should be noted that the voltage regulator in this embodiment is specifically a direct AC / AC converter, which internally includes three AC / AC sub-modules corresponding to the three phases. Each AC / AC sub-module is connected in series to its corresponding phase, enabling independent boost or buck regulation of the voltage of its respective phase. The specific formula for calculating the series compensation voltage is as follows: ; Wherein, V_comp is the series compensation voltage; Kp is the proportional coefficient, which can preferably be 0.85, to accelerate the dynamic response speed to high-frequency disturbances of the bus voltage and suppress voltage overshoot; ΔU_H is the high-frequency deviation voltage; Ki is the integral coefficient, which can preferably be 120, to reduce steady-state error and prevent oscillation caused by integral saturation; and dt is the time derivative.

[0056] Through this combined operation process, the voltage regulator can achieve error-free regulation while ensuring a millisecond-level response speed, ensuring that the bus voltage recovers quickly and stabilizes within the acceptable range.

[0057] It should be noted that the proportional and integral coefficients in the control program are pre-calibrated by those skilled in the art based on the actual hardware selection. Furthermore, due to the limited hardware tolerance of the voltage regulator itself, the distribution box control device, after calculating the theoretical series compensation voltage, will also perform a limiting process to restrict the final output compensation command within a reasonable range of the rated voltage. For example, the maximum compensation voltage of the voltage regulator is limited to ±15% of the rated voltage (i.e., a limit of ±57V), thereby protecting the hardware from overvoltage damage while maintaining dynamic compensation capabilities.

[0058] As can be seen, the control method provided in this embodiment utilizes the complementary characteristics of proportional and integral operations to achieve rapid and accurate dynamic compensation for transient voltage disturbances, and improves the operational safety of the distribution box through amplitude limiting operations. In actual operation verification, for sudden high-frequency voltage dips, the wear-free voltage regulator can respond quickly within 3ms, restoring the dip voltage to above 0.97pu.

[0059] As an optional embodiment, such as Figure 3 As shown, Figure 3 A flowchart of another distribution box control method provided by the present invention. Based on low-frequency deviation voltage, the switching control of capacitors in the capacitor bank is performed to achieve steady-state reactive power compensation of the bus, including: S34. If the absolute value of the low-frequency deviation voltage is greater than the preset steady-state deviation threshold and the duration is greater than the first preset time threshold, then the capacitor bank is controlled to switch based on the low-frequency deviation voltage. S35. If the absolute value of the low-frequency deviation voltage is not greater than the preset steady-state deviation threshold, or the duration is not greater than the first preset time threshold, then control the capacitor bank to maintain the current working state.

[0060] Considering that the connection or prolonged disconnection of large-capacity loads can cause steady-state voltage shifts in distribution transformer substations, capacitor banks, with their large compensation capacity and low cost, are suitable for handling such large-capacity steady-state reactive power compensation needs. However, if... Figure 5 As shown, Figure 5 The present invention provides a structural diagram of a capacitor bank. Capacitor banks typically use mechanical switches for segmented switching, which results in a slow response speed and frequent physical actions that severely shorten the lifespan of the capacitors.

[0061] Based on this, the distribution box control device monitors the low-frequency deviation voltage obtained after filtering and decomposition in real time. First, it determines whether the absolute value of the low-frequency deviation voltage is greater than a preset steady-state deviation threshold. This steady-state deviation threshold represents the maximum steady-state voltage deviation that the distribution area can withstand, i.e., whether a large-capacity reactive power compensation boundary condition needs to be activated. This steady-state deviation threshold can preferably be 7% of the rated voltage (e.g., for a rated voltage of 380V, a steady-state deviation threshold of 26.6V is preferred). Simultaneously, it determines whether the duration of this voltage exceedance state is greater than a first preset time threshold. This first preset time threshold represents the continuous stability characteristics of the voltage drop or overvoltage state, used to filter short-term transient voltage disturbances and prevent the capacitor bank from malfunctioning due to transient fluctuations. It can preferably be set between 15 and 30 seconds (e.g., 20 seconds). If both conditions are met, it indicates that a steady-state voltage drop or overvoltage has indeed occurred on the bus. The distribution box control device then issues a switching command to the capacitor bank based on the sign of the low-frequency deviation voltage to perform steady-state reactive power compensation. If the absolute value of the low-frequency deviation voltage is not greater than the steady-state deviation threshold, or if the absolute value exceeds the limit but the duration does not exceed the first preset time threshold, it indicates that this may be a short-term disturbance. The distribution box control device controls the capacitor bank to maintain its current switching state. Through the above dual judgment process of time and amplitude, it can be ensured that the capacitor bank only starts to operate when large-capacity steady-state compensation is required.

[0062] As can be seen, the switching control method provided in this embodiment accurately allocates the steady-state large-capacity compensation task to the capacitor bank by combining the determination of low-frequency amplitude and duration, which can effectively solve the problem of steady-state voltage exceeding the limit in the distribution area and significantly extend the service life of the capacitor bank.

[0063] As an optional embodiment, it also includes: Obtain the real-time operating temperature of the voltage regulator; If the real-time operating temperature is greater than the preset temperature threshold, the maximum voltage limit when the voltage regulator outputs the series compensation voltage is reduced, and the steady-state deviation threshold and the first preset time threshold for controlling the operation of the capacitor bank are reduced.

[0064] Considering that when the distribution area encounters continuous and severe voltage fluctuations, the power devices inside the voltage regulator need to frequently perform high-frequency voltage regulation, which will generate a lot of heat. If the voltage regulator continues to operate at full load, there may be a safety risk of device damage.

[0065] Based on this, this embodiment acquires temperature sensor data from the voltage regulator in real time through the distribution box control device. When the real-time operating temperature exceeds a preset temperature threshold (e.g., 75°C), which represents the safe operating limit of the voltage regulator under continuous high-frequency operation, derating control is actively initiated: the output voltage limit of the voltage regulator is forcibly reduced from ±15% of the rated voltage to a preset safe limit value (e.g., ±8%), thereby reducing the heat generated by the hardware. At the same time, in order to compensate for the compensation gap caused by the voltage regulator derating, the control device simultaneously lowers the steady-state deviation threshold of the capacitor bank (e.g., from 7% of the rated voltage to 4%) and shortens the first preset time threshold (e.g., from 20 seconds to 10 seconds), so that the capacitor bank can participate in voltage compensation in advance.

[0066] It should be noted that when the real-time operating temperature of the voltage regulator gradually drops as it is derated and falls below the preset safe recovery temperature (e.g., 60°C), the distribution box control device will restore the limits and thresholds of each device to their initial settings.

[0067] As can be seen, the distribution box control method provided in this embodiment can dynamically transfer the compensation pressure to the capacitor bank when the voltage regulator faces the risk of overheating, which not only avoids physical damage to the core power devices, but also ensures the power quality management capability of the distribution box under extreme operating conditions.

[0068] As an optional embodiment, the switching operation of the capacitor bank is controlled based on the low-frequency deviation voltage, including: The number of capacitors operating in the capacitor bank is determined based on the polarity and amplitude of the low-frequency deviation voltage, and the operation of the determined capacitors is controlled. Specifically, when the polarity of the low-frequency deviation voltage is positive, the action is to cut off; when the polarity of the low-frequency deviation voltage is negative, the action is to engage. When the number is greater than or equal to 2, the action interval between any two adjacent capacitors shall not be less than the second preset time threshold.

[0069] Considering that the severity of steady-state deviations in the distribution transformer area bus voltage can vary, switching on or off a large-capacity capacitor bank at once can easily cause drastic changes in grid voltage, or even reverse fluctuations resulting in overcompensation or undercompensation.

[0070] Based on this, the distribution box control device can extract the sign and specific value of the low-frequency deviation voltage. When the sign of the low-frequency deviation voltage is positive, it indicates that there is an overvoltage phenomenon on the current bus. The distribution box control device calculates the number of capacitors that need to be disconnected and controls them to be physically disconnected in sequence. When the sign of the low-frequency deviation voltage is negative, it indicates that there is an undervoltage drop on the current bus. The distribution box control device calculates the number of capacitors that need to be replenished and controls them to be physically closed in sequence. In the specific execution process, if the calculated number of capacitors that need to be operated is greater than or equal to 2, it is preferable to switch only one capacitor with the smallest capacity at a time, and perform the switching action step by step. The time interval between each two adjacent switching actions is not less than a second preset time threshold. This second preset time threshold represents the minimum buffer recovery time (preferably 5 seconds) required for the transient impact of the power grid to dissipate and the voltage to return to steady state after the capacitor is switched, gradually approaching the target voltage value. Through the above-mentioned step-by-step delay action process, the instantaneous current impact on the bus caused by the capacitor bank being connected to or disconnected from the grid can be effectively buffered, maintaining the stability of power quality.

[0071] It should be noted that in the actual control program logic, if the busbar is positively biased but there are no capacitors already in operation in the current capacitor bank, no disconnection action will be performed because it exceeds the hardware physical boundary conditions. Similarly, if all capacitors are in operation and there is still a negative bias, the distribution box control device will also stop issuing operation commands. Those skilled in the art can preset appropriate time thresholds based on the total capacity and grouping of the capacitor banks actually installed in the distribution box.

[0072] As can be seen, the switching control method provided in this embodiment achieves smooth steady-state reactive power compensation of the bus voltage, avoids grid impact caused by centralized switching, and improves the overall reliability of the distribution box operation. Furthermore, since high-frequency disturbances have been eliminated, the capacitor bank is automatically switched on and off according to the delay rule only during steady-state over-limit periods. Verification shows that the number of switching operations of the capacitor bank is reduced by about 72% compared with the traditional solution, which greatly extends the physical service life of mechanical switches and capacitors.

[0073] As an optional embodiment, it also includes: Obtain the three-phase voltage imbalance of the busbar; When the three-phase voltage imbalance exceeds the preset imbalance threshold, the control regulator independently adjusts the voltage of each phase to reduce the voltage deviation between phases.

[0074] Considering that if there is a three-phase voltage imbalance on the busbar, it will not only increase the power loss of the transformer and the line, but may also cause the three-phase electrical equipment to overheat or even be damaged.

[0075] Based on this, the distribution box control device acquires the three-phase voltage data of the bus in real time and calculates the current three-phase voltage imbalance. The specific calculation method for the three-phase voltage imbalance is as follows: subtract the rated phase voltage of 220V from the maximum or minimum phase voltage of the three phases, and then divide by the rated phase voltage of 220V. The distribution box control device then determines whether the absolute value of the three-phase voltage imbalance exceeds a preset imbalance threshold. This preset imbalance threshold represents the allowable limit of phase-to-phase voltage asymmetry caused by uneven load distribution in the three-phase AC system, and can be preferably set to 2%. When the calculated absolute value of the three-phase voltage imbalance exceeds the preset imbalance threshold, the distribution box control device sends a control command to the voltage regulator, controlling the voltage regulator to independently adjust the voltage of each phase, that is, to independently perform voltage boosting or bucking operations for each phase, thereby reducing the phase-to-phase voltage deviation. In practical applications, those skilled in the art can set the above-mentioned imbalance threshold according to the specific load conditions of the distribution area.

[0076] It should be noted that the overall control logic of the distribution box follows a priority order: first addressing overall voltage fluctuations, then resolving three-phase imbalance. Specifically, before determining whether to execute independent three-phase amplitude regulation, the coordinated mitigation of high-frequency voltage flicker and low-frequency steady-state sag is prioritized through the voltage regulator and capacitor bank. Furthermore, the voltage regulator's phase circuits are independent of each other, enabling independent phase control and ensuring that the regulation processes of each phase do not interfere with each other.

[0077] As can be seen, the control method provided in this embodiment achieves precise management of phase-to-phase voltage deviation through real-time monitoring of three-phase voltage imbalance and independent phase-by-phase adjustment of the voltage regulator, thereby further improving the overall power quality and power safety of the distribution substation.

[0078] As an optional embodiment, the voltage regulator includes three AC / AC sub-modules, which are respectively connected to different phases of the three-phase AC bus. The voltage regulator independently adjusts the amplitude of the voltage in each phase, including: The three AC / AC sub-modules are controlled to independently boost or buck the voltage of their respective phases.

[0079] Considering that traditional distribution substations typically use a unified adjustment method to manage three-phase voltage imbalance, adjusting the voltage of one phase can easily cause the voltage of other phases to fluctuate accordingly, making it difficult to achieve independent control of each phase.

[0080] Based on this, this embodiment defines the internal structure of the voltage regulator, setting up three independent AC / AC sub-modules corresponding to the three phases. These three sub-modules are connected in series to the corresponding phases of the three-phase AC bus, such as... Figure 6 As shown, Figure 6 This invention provides a structural diagram of an AC / AC converter. When the distribution box control device determines that it is necessary to reduce the phase-to-phase voltage deviation, it directly controls the three AC / AC sub-modules to independently perform voltage regulation only for their respective phases. Specifically, for the phase with low voltage, the corresponding AC / AC sub-module is controlled to boost the voltage; for the phase with high voltage, the corresponding AC / AC sub-module is controlled to step down the voltage.

[0081] It should be noted that the above-mentioned voltage regulator is preferably a solid-state voltage regulator using a direct AC / AC conversion circuit, which can ensure that the control circuits of each phase are isolated from each other, ensuring that the adjustment action of one phase will not interfere with other phases, so that the independent adjustment commands of each phase issued by the distribution box control device can be accurately executed.

[0082] As can be seen, the control method provided in this embodiment utilizes independent AC / AC sub-module circuits for each phase, avoiding the inter-phase interference problem caused by unified adjustment. This allows the distribution box to directly intervene from the power supply side, thereby achieving targeted adjustment of the inter-phase voltage deviation of the three phases. Simultaneously, this direct series compensation from the voltage source side is not limited by compensation capacity, improving the reliability of three-phase imbalance mitigation.

[0083] The present invention also provides a distribution box control device, such as Figure 7 As shown, Figure 7 This invention provides a structural diagram of a distribution box control device. The distribution box control device includes: Memory 71 is used to store computer programs; Processor 72 is used to execute computer programs to implement the distribution box control method described above.

[0084] For a description of the distribution box control device provided by the present invention, please refer to the embodiments of the distribution box control method described above, which will not be repeated here.

[0085] The present invention also provides a distribution box, such as Figure 8 As shown, Figure 8 This invention provides a structural diagram of a distribution box. The distribution box includes a voltage stabilizer 81 and at least one set of capacitor banks 82, and also includes a distribution box control device as described above; wherein, the voltage stabilizer 81 is connected in series with the three-phase AC bus of the distribution box, and the capacitor banks 82 are connected in parallel with the three-phase AC bus.

[0086] The distribution box provided by this invention can preferably be an intelligent JP cabinet, such as... Figure 9 As shown, Figure 9 This invention provides an internal layout diagram of a distribution box. It includes an external cabinet. Inside the cabinet, in addition to the aforementioned voltage regulator 81, capacitor bank 82, and distribution box control device, there are also an inlet terminal, a metering unit, an outlet terminal, and a protection unit. The inlet terminal, metering unit, and outlet terminal are sequentially connected to a three-phase AC busbar to form a basic power distribution and metering circuit. The protection unit is located between the metering unit and the outlet terminal and is used to cut off the circuit in case of abnormal operating conditions such as overcurrent, short circuit, or lightning overvoltage, ensuring the safety of the electrical equipment and internal components of the distribution box.

[0087] For a description of the distribution box provided by this invention, please refer to the embodiments of the distribution box control method described above, which will not be repeated here.

[0088] It should be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0089] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a distribution box, characterized in that, A capacitor bank is connected in parallel to the busbar of the distribution box, and a voltage regulator is connected in series. The control method of the distribution box includes: Determine the deviation voltage of the busbar at the incoming end of the distribution box, wherein the deviation voltage characterizes the deviation between the line voltage of the busbar and a preset reference voltage; The high-frequency deviation voltage and the low-frequency deviation voltage are determined based on the deviation voltage. The voltage regulator is controlled based on the high-frequency deviation voltage to perform rapid dynamic voltage compensation on the bus. The switching of capacitors in the capacitor bank is controlled based on the low-frequency deviation voltage to provide steady-state reactive power compensation for the bus.

2. The distribution box control method as described in claim 1, characterized in that, Determine the deviation voltage of the busbar at the incoming end of the distribution box, including: Obtain the three-phase line voltages of the busbar; Determine the average value of the line voltage; The deviation voltage is determined based on the average value and the preset reference voltage.

3. The distribution box control method as described in claim 1, characterized in that, Determining the high-frequency deviation voltage and the low-frequency deviation voltage based on the deviation voltage includes: The deviation voltage is low-pass filtered to obtain the low-frequency deviation voltage; The high-frequency deviation voltage is determined based on the deviation voltage and the low-frequency deviation voltage.

4. The distribution box control method as described in claim 1, characterized in that, The voltage regulator is controlled based on the high-frequency deviation voltage to perform rapid dynamic voltage compensation on the bus, including: If the absolute value of the high-frequency deviation voltage is greater than the preset high-frequency disturbance threshold, then the series compensation voltage is determined based on the high-frequency deviation voltage, and the regulator is controlled to output the series compensation voltage. If the absolute value of the high-frequency deviation voltage is less than or equal to the preset high-frequency disturbance threshold, the voltage regulator is controlled to maintain the current output state.

5. The distribution box control method as described in claim 4, characterized in that, Determining the series compensation voltage based on the high-frequency deviation voltage includes: Based on the high-frequency deviation voltage, the corresponding proportional adjustment component and integral adjustment component are determined by proportional calculation and integral calculation, respectively. The series compensation voltage is determined based on the proportional adjustment component and the integral adjustment component.

6. The distribution box control method as described in claim 1, characterized in that, Based on the low-frequency deviation voltage, the capacitors in the capacitor bank are switched on and off to perform steady-state reactive power compensation on the bus, including: If the absolute value of the low-frequency deviation voltage is greater than a preset steady-state deviation threshold and the duration is greater than a first preset time threshold, then the capacitor bank is controlled to perform switching operations based on the low-frequency deviation voltage. If the absolute value of the low-frequency deviation voltage is not greater than a preset steady-state deviation threshold, or the duration is not greater than a first preset time threshold, then the capacitor bank is controlled to maintain its current operating state.

7. The distribution box control method as described in claim 6, characterized in that, Controlling the switching action of the capacitor bank based on the low-frequency deviation voltage includes: The number of capacitors operating in the capacitor bank is determined based on the polarity and amplitude of the low-frequency deviation voltage, and the operation of the determined capacitors is controlled. Specifically, when the polarity of the low-frequency deviation voltage is positive, the action is to cut off; when the polarity of the low-frequency deviation voltage is negative, the action is to engage. When the number is greater than or equal to 2, the interval between the operation of each two adjacent capacitors is not less than the second preset time threshold.

8. The distribution box control method according to any one of claims 1 to 7, characterized in that, Also includes: Obtain the three-phase voltage imbalance of the busbar; When the three-phase voltage imbalance exceeds a preset imbalance threshold, the voltage regulator is controlled to independently adjust the voltage of each phase to reduce the voltage deviation between phases.

9. A control device for a distribution box, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the distribution box control method as described in any one of claims 1 to 8.

10. A distribution box, characterized in that, It includes a voltage regulator and at least one set of capacitor banks, and further includes the distribution box control device as described in claim 9; wherein the voltage regulator is connected in series with the three-phase AC bus of the distribution box, and the capacitor banks are connected in parallel with the three-phase AC bus.

Images