A portable intelligent grid-connected control method and device for improving voltage stability in power distribution networks.

Abstract

This invention discloses a portable intelligent grid-connected control method and device for improving the voltage stability of distribution networks. First, the current battery state is acquired. By judging the current battery state, executable action modes and pre-actions are determined. After determining the executable action modes, corresponding methods are implemented based on different grid voltage and battery conditions to improve power quality. This method can achieve intelligent charging and discharging under the comprehensive consideration of the grid-connected device state and the distribution network state, thereby improving the power quality of the grid. This invention also discloses a portable intelligent bidirectional charging and discharging grid-connected device. By applying the grid-connected device control method to the intelligent grid-connected device, it can be used to manage the power quality of rural power grids in complex areas such as rural areas, improving the operational stability of the distribution network.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a portable intelligent grid-connected control method and device for improving the voltage stability of power distribution networks. Background Technology

[0002] As the main power supply system in rural areas, the stability of the power distribution network directly affects the reliability of power supply in these areas.

[0003] Currently, there are two main methods to improve the stability of power distribution networks: directly setting up energy storage power stations and using portable power supplies. Directly setting up energy storage power stations involves installing them at fixed locations to transmit or store power to the grid. However, this method has drawbacks such as high capital investment, long implementation time, and construction obstacles. Using portable power supplies to maintain distribution network stability offers advantages such as lower cost, greater portability, and the ability to be installed in active transformer areas, making it more suitable for the current scenario of integrating new energy sources into the grid.

[0004] Current portable power supplies for improving the stability of power distribution networks have the following problems: rural areas are more complex, and portable power supplies cannot solve the power quality problems of rural power grids; traditional portable power supplies use mostly Buck or Boost circuits in their DC-DC modules, which have low transmission efficiency. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a portable intelligent grid-connected control method and device for improving the voltage stability of the distribution network. By intelligently selecting the power management scheme according to the grid voltage, the power quality is improved. Furthermore, the DC-DC module in the portable intelligent bidirectional charging and discharging grid-connected device uses a bidirectional LLC resonant circuit, which can effectively improve the transmission efficiency of the DC-DC module.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a portable intelligent grid-connected control method for improving the voltage stability of a distribution network, comprising:

[0007] Step 1: Collect the voltage and current of the battery in the intelligent bidirectional charging and discharging device, and use the collected data to predict the battery capacity data;

[0008] Step 2: Preprocess the collected battery voltage to obtain the battery conversion voltage required by the microprocessor. By comparing the battery conversion voltage with the threshold set in the microprocessor, the executable operation mode of the intelligent bidirectional charging and discharging grid-connected device can be obtained. Based on the battery capacity data, perform the pre-action to enter the executable operation mode.

[0009] Step 3: After determining the executable action mode, perform power management work according to the actions set in the corresponding mode; when in low voltage management mode, there are 3 actions to choose from for different grid voltages or battery conditions, and when in high voltage management mode, there are 3 actions to choose from for different grid voltages or battery conditions.

[0010] In a preferred embodiment, step 1 specifically includes:

[0011] Voltage, current and capacity experimental data were collected using batteries of the same type as those used in the intelligent bidirectional charging and discharging device. The voltage, current and time data were combined into three-dimensional data, and this three-dimensional data was fed into a neural network for model training.

[0012] A voltage sensor collects battery voltage data, and an inductive sensor collects battery current data. The voltage, current, and time data are combined into three-dimensional data, which is then fed into a trained neural network model to output the current battery capacity data. The predicted capacity formula is as follows:

[0013] Qpredict=f(u,i,t) (1)

[0014] Where Qpredict is the capacity data predicted by the model, f(·) is the equivalent prediction function of the model, u is the battery voltage data collected by the voltage sensor, i is the battery current data collected by the current sensor, and t is the time data corresponding to the voltage and current acquisition.

[0015] In a preferred embodiment, step 2 specifically includes:

[0016] The acquired battery voltage data is reduced in size before being fed into the microprocessor, and the calculation formula is as follows:

[0017]

[0018] Wherein, Uinput is the acquired battery voltage signal data; k is a reduction constant; and Uoutput is the battery voltage signal that is finally input into the microprocessor for comparison.

[0019] The signal Uoutput is compared with the set threshold Uindex. When the signal Uoutput is less than the set threshold Uindex, the battery performs one of two operations: charging the battery from the grid or stopping the battery, which is called entering the low voltage management mode. When the signal Uoutput is equal to the set threshold Uindex, the battery performs one of two operations: supplying power to the grid or stopping the battery, which is called the overvoltage management mode.

[0020] In a preferred embodiment, the battery SOC value is calculated using the current battery capacity data, using the following formula:

[0021]

[0022] Where SOC is the battery's state of charge, Qremain is the remaining capacity data of the battery during operation, i.e., the current capacity data of the battery, and Qn is the battery's rated capacity data.

[0023] After obtaining the battery's SOC data, it is compared with the set threshold. When the battery is in low-voltage management mode, it is determined whether the SOC exceeds the low-voltage management mode threshold. If the SOC is greater than the set threshold, the low-voltage management mode is directly activated. If the SOC is less than the set threshold and the grid voltage is above the lower termination line, the battery is charged until the grid voltage reaches the lower termination line. After that, the battery directly enters low-voltage management mode. If the SOC is less than the set threshold and the grid voltage is below the lower termination line, no action is taken. When the battery is in high-voltage management mode, it is determined whether the SOC exceeds the high-voltage management mode threshold. If the SOC is less than the set threshold, the high-voltage management mode is directly activated. If the SOC is greater than the set threshold and the grid voltage is below the upper termination line, the battery supplies power to the grid until the grid voltage reaches the upper termination line. After that, the battery directly enters high-voltage management mode. If the SOC is greater than the set threshold and the grid voltage is above the upper termination line, no action is taken.

[0024] In a preferred embodiment, step 3 specifically includes:

[0025] The battery management working mode is mainly divided into low voltage management mode and overvoltage management mode. The overall control logic has voltage lines such as up / down start line, up / down end line, fall-down line and rise line. The battery management working logic is controlled according to these lines.

[0026] For the low battery voltage management mode, there are three logical judgments and actions:

[0027] The first scenario is when the grid voltage is less than 0.9 times the target output voltage and the battery can perform power supply operation for the grid. The target output voltage of 0.9 times is the lower start line. The logical action to be taken in this case is: start the smart grid-connected device, continuously increase the discharge power of the smart grid-connected device until the grid voltage rises to the qualified lower limit, i.e. the lower termination line, and keep the discharge power of the smart grid-connected device unchanged after the grid voltage reaches the lower termination line.

[0028] The second scenario is when the battery is in a state where discharge is prohibited. When the battery is in this state, the smart grid-connected device will not discharge regardless of the state of the power grid, and will be in a state of stopped discharge.

[0029] The third scenario is when the grid voltage rises above the set upper limit voltage due to factors such as reduced load, i.e., the rising line. In this case, the logical action to be taken is to reduce the discharge power of the smart grid-connected device that has been started and is discharging until the grid voltage drops to the specified voltage, i.e., the lower termination line. After the grid voltage reaches the lower termination line, the discharge power of the smart grid-connected device remains unchanged.

[0030] In a preferred embodiment, for the battery overvoltage mitigation mode, there are three logical judgments and actions:

[0031] The first scenario is when the grid voltage exceeds 1.07 times the target output voltage and the battery can perform grid charging operations. The target output voltage of 1.07 times is the starting line. The logical action to be taken at this time is: start the smart grid-connected device, continuously increase the charging power until the grid voltage drops to the qualified upper limit, which is the termination line. After the grid voltage reaches the termination line, keep the charging power of the smart grid-connected device unchanged.

[0032] The second scenario is when the battery is in a state where charging is prohibited. When the battery is in this state, the smart grid-connected device will not charge the battery regardless of the state of the power grid, and it will be in a state of stopped charging.

[0033] The third scenario is when the grid voltage drops below the set voltage (i.e., the fallback line) due to reasons such as reduced photovoltaic output. In this case, the logical action to be taken is to reduce the charging power of the smart grid-connected device that has been started and is charging until the grid voltage rises to the specified voltage (i.e., the upper termination line). After the grid voltage reaches the upper termination line, the discharge power of the smart grid-connected device remains unchanged.

[0034] This invention also provides a portable intelligent grid-connected device for improving the voltage stability of a distribution network, and operates a portable intelligent grid-connected control method for improving the voltage stability of a distribution network as described above, including:

[0035] Power supply battery and protection module: The main energy storage device of the portable intelligent bidirectional charging and discharging device, used to provide power to boost the grid voltage when the grid voltage is low; and to absorb excess power to lower the grid voltage when the grid voltage is high.

[0036] DC-DC module: A bidirectional channel for providing DC power. When the battery needs to supply power to the grid, the DC-DC module converts the battery's low DC voltage to a high DC voltage; when the grid needs to charge the battery, the DC-DC module converts the high DC voltage from the grid, which is converted by the DC-AC module, into the low DC voltage required for battery charging.

[0037] DC-AC module: Used to provide a bidirectional channel between high DC voltage and AC power from the grid. When the battery needs to supply power to the grid, the DC-AC module activates the inverter mode to convert the high DC voltage obtained from the DC-DC converter into AC power to supply power to the grid. When the grid needs to charge the battery, the DC-AC module starts the rectifier module to convert the AC voltage of the grid into high DC voltage, preparing for the subsequent DC-DC module to convert it into low DC voltage.

[0038] In a preferred embodiment, the power supply battery and protection module include

[0039] The power supply battery has built-in voltage and current sensors. The power supply battery is used to provide power to increase the grid voltage when the grid voltage is too low and to absorb power to decrease the grid voltage when the grid voltage is too high. The voltage and current sensors are used to measure the battery's operating voltage and operating current, thereby predicting the battery's SOC.

[0040] The temperature protection module, which is the temperature sensor built into the battery, is used to measure the temperature data when the battery is working. The current temperature data is put into the over-temperature judgment algorithm to determine whether the battery is in an over-temperature working state.

[0041] In a preferred embodiment, the DC-DC module includes:

[0042] DC low voltage side inverter rectifier unit: used to convert the low DC voltage of the battery into AC power to prepare for subsequent voltage boost; it can also be used to convert the AC power obtained by the transformer step-up and step-down unit into low DC voltage to charge the battery.

[0043] Transformer step-up / step-down unit: Used to step up the AC power obtained by the DC low-voltage side inverter rectifier unit to a higher voltage level, or to step down the AC power obtained by the DC high-voltage side inverter rectifier unit to a lower voltage level.

[0044] DC high voltage side inverter unit: used to convert the AC voltage of a higher voltage level obtained by the transformer step-up and step-down unit into DC high voltage, or to convert the DC high voltage obtained by the DC-AC module into AC voltage of a higher voltage level.

[0045] In a preferred embodiment, the DC-AC module includes:

[0046] Single-phase grid-connected inverter and rectifier unit: used to invert the high DC voltage obtained by the DC-DC module into AC power for power supply to the grid, or to rectify the AC power from the grid into high DC voltage to prepare for the subsequent operation of the DC-DC module;

[0047] Phase-locked loop (PLL) unit: used to track the phase of AC current when a single-phase grid-connected inverter converts DC high voltage into AC current, so that the phase of AC voltage is the same as the phase of AC current.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] This invention uses a neural network model to predict battery capacity and dynamically adjusts the power management scheme based on battery voltage, grid voltage, and battery capacity: when the grid voltage is low, the battery supplies power to the grid to increase the grid voltage; when the grid voltage is high, the grid charges the battery to reduce the grid voltage. This invention enables intelligent management of grid power quality, improving the power quality and operational stability of rural power grids.

[0050] The present invention also provides a portable intelligent bidirectional charging and discharging grid-connected device. In addition to the above-mentioned beneficial effects, a bidirectional LLC resonant circuit is selected in the DC-DC module to undertake the task, which effectively improves the conversion efficiency of the DC-DC module. Attached Figure Description

[0051] Figure 1 A flowchart illustrating a portable intelligent grid-connected control method for improving voltage stability in a power distribution network, provided as an embodiment of the present invention;

[0052] Figure 2 Flowchart for predicting current battery capacity data;

[0053] Figure 3 The flowchart shows the algorithm for obtaining executable decisions and preliminary actions based on the current battery state.

[0054] Figure 4 A diagram illustrating the actions corresponding to different battery management operating modes;

[0055] Figure 5 The circuit diagram of a portable intelligent grid-connected device for improving the voltage stability of a power distribution network is provided in an embodiment of the present invention. Detailed Implementation

[0056] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0057] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0058] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0059] Existing methods for connecting portable power supplies to the grid typically involve decisions made by a dispatch center. The dispatch center obtains the current grid operating status and connects a fully charged portable power supply to the grid when the grid voltage is low. When the grid voltage is high, a depleted portable power supply is connected to the grid to absorb excess power and lower the grid voltage. However, this method is lengthy and cumbersome. Portable power supplies lack the ability to autonomously determine the grid operating status and perform intelligent power management, meaning they cannot address the power quality issues in rural power grids. Furthermore, most portable power supplies use Buck or Boost circuits in their DC-DC modules, resulting in low power conversion efficiency.

[0060] Therefore, this invention provides a portable intelligent grid-connected control method to improve the voltage stability of distribution networks. It uses a neural network model to predict battery capacity and dynamically adjusts the power management scheme based on battery voltage, grid voltage, and battery capacity: when the grid voltage is low, the battery supplies power to the grid to increase it; when the grid voltage is high, the grid charges the battery to lower it. This achieves intelligent management of grid power quality, improving the power quality and operational stability of rural power grids.

[0061] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 1 A flowchart illustrating a portable intelligent grid-connected control method for improving voltage stability in a power distribution network, provided as an embodiment of the present invention; Figure 2 Flowchart for predicting current battery capacity data; Figure 3 The flowchart shows the algorithm for obtaining executable decisions and preliminary actions based on the current battery state. Figure 4 Diagram showing the corresponding actions for different battery management operating modes.

[0062] In this embodiment, the method may include:

[0063] S101 collects physical quantities such as voltage and current of the battery in the intelligent bidirectional charging and discharging device, and uses the collected data to predict battery capacity data.

[0064] This step mainly involves collecting the current voltage and current data of the battery from the sensor, and then feeding the current voltage, current, and time data into a neural network model to obtain the current battery capacity, thus preparing for the subsequent pre-processing of the governance model.

[0065] S102, preprocess the collected battery voltage to obtain the battery conversion voltage required by the microprocessor, and obtain the executable operation mode of the intelligent bidirectional charging and discharging grid-connected device by comparing the battery conversion voltage with the threshold set in the microprocessor. Perform the pre-action before entering the executable operation mode according to the battery capacity data.

[0066] Building upon the previous step, this step aims to obtain the executable operation modes and pre-actions of the intelligent bidirectional charging and discharging grid-connected device through the battery voltage value. Then, based on the obtained executable operation modes, the actions set within the mode can be executed according to different situations to manage power quality.

[0067] S103: After determining the executable action mode, perform power management work according to the actions set for the corresponding mode. When in low voltage management mode, there are a total of 3 actions to choose from for different grid voltages or battery conditions. When in high voltage management mode, there are also 3 actions to choose from for different grid voltages or battery conditions.

[0068] Building on the previous step, this step aims to select appropriate actions from the predefined patterns and execute those actions to improve grid power quality by increasing voltage when it is too low and decreasing voltage when it is too high.

[0069] In summary, this embodiment uses voltage and current sensors to collect the battery's operating voltage and current. The operating voltage, current, and corresponding time are combined to form three-dimensional data, which is then fed into a trained neural network to obtain predicted battery capacity data. The collected voltage data is preprocessed and sent to a microprocessor for comparison with a threshold to determine the executable action mode of the intelligent bidirectional charging and discharging device. Based on the predicted battery capacity data, the pre-action of the mode is obtained. Finally, the corresponding action is executed based on the mode and the current grid state. This method fully considers both the battery and the grid, enabling autonomous judgment of the grid state for comprehensive power quality management, thus improving the power quality and operational stability of rural power grids.

[0070] The following describes a portable intelligent bidirectional charging and discharging grid-connected device provided by an embodiment of the present invention. The portable intelligent bidirectional charging and discharging grid-connected device described below corresponds to the portable intelligent grid-connected control method for improving the voltage stability of the distribution network described above.

[0071] Please refer to Figure 5 , Figure 5 A circuit diagram of a portable intelligent bidirectional charging and discharging grid-connected device provided in an embodiment of the present invention.

[0072] In this embodiment, the device may include:

[0073] Power supply battery and protection module 100: The main energy storage device of the portable intelligent bidirectional charging and discharging device, mainly used to provide power to boost the grid voltage when the grid voltage is low; and to absorb excess power to lower the grid voltage when the grid voltage is high.

[0074] DC-DC Module 200: This module provides a bidirectional channel for DC power. When the battery needs to supply power to the grid, the DC-DC module converts the battery's low DC voltage into a high DC voltage. When the grid needs to charge the battery, the DC-DC module converts the high DC voltage from the grid, which is converted by the DC-AC module, into the low DC voltage required for battery charging.

[0075] DC-AC Module 300: This module provides a bidirectional channel between high-voltage DC and AC power from the grid. When the battery needs to supply power to the grid, the DC-AC module activates the inverter mode to convert the high-voltage DC obtained from the DC-DC converter into AC power to supply power to the grid. When the grid needs to charge the battery, the DC-AC module activates the rectifier module to convert the AC voltage of the grid into high-voltage DC, preparing for the subsequent DC-DC module to convert it into low-voltage DC.

[0076] Optionally, the power supply battery and protection module 100 may include:

[0077] The power supply battery has built-in voltage and current sensors. The power supply battery is used to provide power to increase the grid voltage when the grid voltage is too low and to absorb power to decrease the grid voltage when the grid voltage is too high. The voltage and current sensors are used to measure the battery's operating voltage and operating current, thereby predicting the battery's SOC.

[0078] The temperature protection module, which is the temperature sensor built into the battery, is used to measure the temperature data when the battery is working. The current temperature data is put into the over-temperature judgment algorithm to determine whether the battery is in an over-temperature working state.

[0079] Optionally, the DC-DC module 200 may include:

[0080] DC low voltage side inverter rectifier unit: used to convert the low DC voltage of the battery into AC power to prepare for subsequent voltage boost; it can also be used to convert the AC power obtained by the transformer step-up and step-down unit into low DC voltage to charge the battery.

[0081] Transformer step-up / step-down unit: Used to step up the AC power obtained by the DC low-voltage side inverter rectifier unit to a higher voltage level, or to step down the AC power obtained by the DC high-voltage side inverter rectifier unit to a lower voltage level.

[0082] DC high-voltage side inverter unit: Used to convert the higher-voltage AC voltage obtained from the transformer step-up / step-down unit into a higher-voltage DC voltage, or to convert the higher-voltage DC voltage obtained from the DC-AC module into a higher-voltage AC voltage.

[0083] Optionally, the DC-AC module 300 may include:

[0084] Single-phase grid-connected inverter and rectifier unit: Used to invert the high-voltage DC obtained from the DC-DC module into AC power for supplying power to the grid, or to rectify the AC power from the grid into high-voltage DC power to prepare for the subsequent operation of the DC-DC module.

[0085] Phase-locked loop (PLL) unit: used to track the phase of AC current when a single-phase grid-connected inverter converts DC high voltage into AC current, so that the phase of AC voltage is the same as the phase of AC current.

[0086] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0087] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0088] The above provides a detailed description of a portable intelligent grid-connected control method and a portable intelligent bidirectional charging and discharging grid-connected device for improving the voltage stability of a power distribution network, as provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A portable intelligent grid-connected control method for improving voltage stability in distribution networks, characterized in that, include: Step 1: Collect the voltage and current of the battery in the intelligent bidirectional charging and discharging device, and use the collected data to predict the battery capacity data; Step 2: Preprocess the collected battery voltage to obtain the battery conversion voltage required by the microprocessor. By comparing the battery conversion voltage with the threshold set in the microprocessor, the executable operation mode of the intelligent bidirectional charging and discharging grid-connected device can be obtained. Based on the battery capacity data, perform the pre-action to enter the executable operation mode. Step 3: After determining the executable action mode, perform power management work according to the actions set in the corresponding mode; when in low voltage management mode, there are 3 actions to choose from for different grid voltages or battery conditions; when in high voltage management mode, there are 3 actions to choose from for different grid voltages or battery conditions. Step 2 specifically includes: The acquired battery voltage data is reduced in size before being fed into the microprocessor, and the calculation formula is as follows: = ,in, The collected battery voltage signal data; For the reduction constant, The battery voltage signal is ultimately input into the microprocessor for comparison. Signal With the set threshold Compare, when the signal Less than the set threshold When the battery is in low voltage management mode, it can either charge the battery from the grid or stop charging the battery. equal to the set threshold At this time, the battery can perform two operations: supplying power to the grid or stopping the battery, which is the overvoltage management mode; Step 3 specifically includes: The battery management working mode is mainly divided into low voltage management mode and overvoltage management mode. The overall control logic has voltage lines such as up / down start line, up / down end line, fall-down line and rise line. The battery management working logic is controlled based on these lines. For the low battery voltage management mode, there are three logical judgments and actions: The first scenario is when the grid voltage is less than 0.9 times the target output voltage and the battery can perform power supply operation for the grid. The target output voltage of 0.9 times is the lower start line. The logical action to be taken in this case is: start the smart grid-connected device, continuously increase the discharge power of the smart grid-connected device until the grid voltage rises to the qualified lower limit, i.e. the lower termination line, and keep the discharge power of the smart grid-connected device unchanged after the grid voltage reaches the lower termination line. The second scenario is when the battery is in a state where discharge is prohibited. When the battery is in this state, the smart grid-connected device will not discharge regardless of the state of the power grid, and will be in a state of stopped discharge. The third scenario is when the grid voltage rises above the set upper limit voltage due to a decrease in load, i.e., the rising line. In this case, the logical action to be taken is to reduce the discharge power of the smart grid-connected device that has been started and is discharging until the grid voltage drops to the specified voltage, i.e., the lower termination line. After the grid voltage reaches the lower termination line, the discharge power of the smart grid-connected device remains unchanged.

2. The portable intelligent grid-connected control method for improving voltage stability in a distribution network according to claim 1, characterized in that, Step 1 specifically includes: Voltage, current and capacity experimental data were collected using batteries of the same type as those used in the intelligent bidirectional charging and discharging device. The voltage, current and time data were combined into three-dimensional data, and this three-dimensional data was fed into a neural network for model training. A voltage sensor collects battery voltage data, and an inductive sensor collects battery current data. The voltage, current, and time data are combined into three-dimensional data, which is then fed into a trained neural network model to output the current battery capacity data. The predicted capacity formula is as follows: = ,in, Here, f(·) represents the capacity data predicted by the model, u represents the battery voltage data collected using a voltage sensor, i represents the battery current data collected using a current sensor, and t represents the time data corresponding to the voltage and current acquisition.

3. The portable intelligent grid-connected control method for improving voltage stability in a distribution network according to claim 1, characterized in that, The battery's State of Charge (SOC) value is calculated using the battery's current capacity data, using the following formula: = ,in This represents the battery's state of charge. This refers to the remaining capacity data of the battery during operation, i.e., the current battery capacity data. This refers to the rated capacity data of the battery; After obtaining the battery's SOC data, it is compared with the set threshold. When the battery is in low-voltage management mode, it is determined whether the SOC exceeds the low-voltage management mode threshold. If the SOC is greater than the set threshold, the low-voltage management mode is directly activated. If the SOC is less than the set threshold and the grid voltage is above the lower termination line, the battery is charged until the grid voltage reaches the lower termination line. After that, the battery directly enters low-voltage management mode. If the SOC is less than the set threshold and the grid voltage is below the lower termination line, no action is taken. When the battery is in high-voltage management mode, it is determined whether the SOC exceeds the high-voltage management mode threshold. If the SOC is less than the set threshold, the high-voltage management mode is directly activated. If the SOC is greater than the set threshold and the grid voltage is below the upper termination line, the battery supplies power to the grid until the grid voltage reaches the upper termination line. After that, the battery directly enters high-voltage management mode. If the SOC is greater than the set threshold and the grid voltage is above the upper termination line, no action is taken.

4. The portable intelligent grid-connected control method for improving voltage stability in a distribution network according to claim 1, characterized in that, For battery overvoltage mitigation, there are three logical judgments and actions: The first scenario is when the grid voltage exceeds 1.07 times the target output voltage and the battery can perform grid charging operations. The target output voltage of 1.07 times is the starting line. The logical action to be taken at this time is: start the smart grid-connected device, continuously increase the charging power until the grid voltage drops to the qualified upper limit, which is the termination line. After the grid voltage reaches the termination line, keep the charging power of the smart grid-connected device unchanged. The second scenario is when the battery is in a state where charging is prohibited. When the battery is in this state, the smart grid-connected device will not charge the battery regardless of the state of the power grid, and it will be in a state of stopped charging. The third scenario is that the grid voltage drops below the set voltage (i.e., the fallback line) due to reduced photovoltaic output. In this case, the logical action to be taken is to reduce the charging power of the smart grid-connected device that has been started and is charging until the grid voltage rises to the specified voltage (i.e., the upper termination line). After the grid voltage reaches the upper termination line, the discharge power of the smart grid-connected device remains unchanged.

5. A portable intelligent grid-connected device for improving the voltage stability of a power distribution network, characterized in that, Running a portable intelligent grid-connected control method for improving the voltage stability of a distribution network as described in any one of claims 1-4, comprising: Power supply battery and protection module: The main energy storage device of the portable intelligent bidirectional charging and discharging device, used to provide power to boost the grid voltage when the grid voltage is low; and to absorb excess power to lower the grid voltage when the grid voltage is high. DC-DC module: A bidirectional channel for providing DC power. When the battery needs to supply power to the grid, the DC-DC module converts the battery's low DC voltage to a high DC voltage; when the grid needs to charge the battery, the DC-DC module converts the high DC voltage from the grid, which is converted by the DC-AC module, into the low DC voltage required for battery charging. DC-AC module: Used to provide a bidirectional channel between high DC voltage and AC power from the grid. When the battery needs to supply power to the grid, the DC-AC module activates the inverter mode to convert the high DC voltage obtained from the DC-DC converter into AC power to supply power to the grid. When the grid needs to charge the battery, the DC-AC module starts the rectifier module to convert the AC voltage of the grid into high DC voltage, preparing for the subsequent DC-DC module to convert it into low DC voltage.

6. A portable intelligent grid-connected device for improving voltage stability in a distribution network according to claim 5, characterized in that, The power supply battery and protection module include The power supply battery has built-in voltage and current sensors. The power supply battery is used to provide power to increase the grid voltage when the grid voltage is too low and to absorb power to decrease the grid voltage when the grid voltage is too high. The voltage and current sensors are used to measure the battery's operating voltage and operating current, thereby predicting the battery's SOC. The temperature protection module, which is the temperature sensor built into the battery, is used to measure the temperature data when the battery is working. The current temperature data is put into the over-temperature judgment algorithm to determine whether the battery is in an over-temperature working state.

7. A portable intelligent grid-connected device for improving voltage stability in a distribution network according to claim 5, characterized in that, The DC-DC module includes: DC low voltage side inverter rectifier unit: used to convert the low DC voltage of the battery into AC power to prepare for subsequent voltage boost; it can also be used to convert the AC power obtained by the transformer step-up and step-down unit into low DC voltage to charge the battery. Transformer step-up / step-down unit: Used to step up the AC power obtained by the DC low-voltage side inverter rectifier unit to a higher voltage level, or to step down the AC power obtained by the DC high-voltage side inverter rectifier unit to a lower voltage level. DC high voltage side inverter unit: used to convert the AC voltage of a higher voltage level obtained by the transformer step-up and step-down unit into DC high voltage, or to convert the DC high voltage obtained by the DC-AC module into AC voltage of a higher voltage level.

8. A portable intelligent grid-connected device for improving voltage stability in a distribution network according to claim 5, characterized in that, The DC-AC module includes: Single-phase grid-connected inverter and rectifier unit: used to invert the high DC voltage obtained by the DC-DC module into AC power for power supply to the grid, or to rectify the AC power from the grid into high DC voltage to prepare for the subsequent operation of the DC-DC module; Phase-locked loop (PLL) unit: used to track the phase of AC current when a single-phase grid-connected inverter converts DC high voltage into AC current, so that the phase of AC voltage is the same as the phase of AC current.

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