Precise estimation method for soc of photovoltaic water supply battery in pastoral area based on ampere-hour integration method

Abstract

The application discloses a SOC precise estimation method for a photovoltaic water supply battery in a pastoral area based on an ampere-hour integration method, and comprises the following steps: obtaining a battery current, a battery terminal voltage and an ambient temperature of an energy storage battery; identifying a charging condition, a discharging condition and a static condition according to the battery current and the battery terminal voltage; obtaining an SOC integral estimation value by integrating the battery current based on the ampere-hour integration method in the charging or discharging condition, and performing temperature compensation on a battery capacity according to the ambient temperature, and setting charging efficiency and discharging efficiency respectively according to the charging and discharging states; suspending the ampere-hour integration in the static condition, obtaining an SOC correction value according to a stabilized open-circuit voltage, and correcting the integral estimation value; and outputting the corrected SOC. The application eliminates cumulative errors through multi-condition identification and static open-circuit voltage closed-loop correction, and realizes the precise estimation of the SOC of the photovoltaic water supply battery in the pastoral area by combining temperature compensation, charging and discharging efficiency separation and capacity attenuation correction, so that overcharging and overdischarging of the battery are prevented.

Description

Technical Field

[0001] This invention relates to the field of battery state of charge estimation technology, and in particular to a method for accurate estimation of the SOC of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integral method. Background Technology

[0002] High-altitude pastoral areas are vast and sparsely populated, with insufficient power grid coverage and a lack of conventional energy sources. Photovoltaic water pumping technology utilizes solar energy to convert light energy into electrical energy, which is stored in batteries. These batteries then drive water pumps at night or during cloudy or rainy weather, providing a reliable guarantee for drinking water for people and livestock in these areas. A typical photovoltaic water pumping system consists of a photovoltaic array, a solar charge / discharge controller, a battery bank, a water pump controller, and a water pump. The battery acts as an energy buffer; its State of Charge (SOC) reflects the ratio of the battery's current remaining charge to its full capacity, serving as the core basis for charge / discharge control and protection. Accurately estimating the battery's SOC can effectively prevent overcharging and over-discharging, extend battery life, and ensure the continuous and stable operation of the water supply system, which is of great significance for drinking water safety in high-altitude pastoral areas.

[0003] Existing battery SOC estimation methods mainly include the open-circuit voltage method, the ampere-hour integration method, the model estimation method, and the data-driven method. Among them, the ampere-hour integration method is widely used in battery SOC estimation in photovoltaic water supply systems due to its advantages such as simple principle, good real-time performance, low computational load, and ease of implementation in embedded controllers. The ampere-hour integration method accumulates the charge and discharge capacity by integrating the battery charging and discharging current over time, and then calculates the battery SOC by combining it with the battery capacity. To improve the numerical accuracy of the ampere-hour integration, existing technologies have proposed an improved algorithm based on multi-step numerical integration. This algorithm establishes and solves the ampere-hour integration mathematical model, performs a Taylor expansion on the solution, and uses a linear weighted combination of the slopes at multiple time points within the sampling interval to estimate the average slope, thereby reducing integration error. By identifying the charging, discharging, and resting conditions of the energy storage battery, performing ampere-hour integration under charging and discharging conditions, and using open-circuit voltage for closed-loop correction of SOC under resting conditions, the accumulated error of ampere-hour integration over long-term operation can be eliminated, improving the accuracy of SOC estimation.

[0004] However, existing ampere-hour integration methods and their numerical improvements still have the following shortcomings. Ampere-hour integration is essentially an open-loop integration, and its estimation accuracy is highly dependent on the accuracy of the initial state of charge (SOC) and the measurement accuracy of the current sensor. The initial SOC error, current sensor zero drift, and measurement noise will accumulate over time, and the SOC estimation error will increase significantly after long-term operation. Existing numerical improvement algorithms only reduce the integration discretization error and cannot eliminate the inherent cumulative error of open-loop integration. In view of this, this application is proposed. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a precise SOC estimation method for photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A precise method for estimating the State of Charge (SOC) of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integral method includes the following steps: The real-time operating parameters of the energy storage battery in the photovoltaic water supply system are obtained, including battery current, battery terminal voltage and ambient temperature. The current operating condition of the energy storage battery is identified based on the battery current and the battery terminal voltage. The operating conditions include charging, discharging, and resting conditions. When the energy storage battery is in charging or discharging condition, the battery current is integrally calculated based on the ampere-hour integration method to obtain the integral estimate of the battery SOC. The battery capacity is temperature compensated according to the ambient temperature, and the charging efficiency and discharging efficiency are set according to the charging and discharging state of the energy storage battery. When the energy storage battery is in a static state, the ampere-hour integration of the battery current is paused, the open-circuit voltage after the battery terminal voltage stabilizes is detected, the correction value of the battery SOC is obtained according to the mapping relationship between the open-circuit voltage and the battery SOC, and the integral estimate of the battery SOC is corrected using the correction value. Output the integral estimate of the corrected battery SOC.

[0007] The above further includes: Furthermore, identifying the current operating condition of the energy storage battery based on the battery current and the battery terminal voltage includes: When the battery current is greater than the first current threshold and the battery terminal voltage shows an upward trend, it is determined that the energy storage battery is in charging condition. When the battery current is less than the second current threshold and the battery terminal voltage shows a downward trend, it is determined that the energy storage battery is in a discharge state. When the absolute value of the battery current is less than the static current threshold and the duration reaches the preset static time, the energy storage battery is determined to be in static condition.

[0008] Furthermore, temperature compensation for battery capacity based on the ambient temperature includes: Based on the preset mapping relationship between ambient temperature and temperature correction coefficient, determine the temperature correction coefficient corresponding to the current ambient temperature; Multiply the rated capacity of the energy storage battery by the temperature correction factor to obtain the corrected capacity at the current ambient temperature. The ampere-hour integral is calculated based on the corrected capacity.

[0009] Furthermore, the battery current is calculated by integration based on the ampere-hour integration method, including: The battery current is collected according to a preset sampling period; The current integral increment within each sampling period is calculated using a multi-step numerical integration method, which is based on a weighted combination of current sampling values ​​at the current sampling time and its neighboring sampling times.

[0010] Furthermore, a multi-step numerical integration method is used to calculate the current integral increment within each sampling period, including: Obtain the first slope corresponding to the current sample value at the current sampling moment; Obtain the second and third slopes corresponding to the current sample values ​​at least two intermediate moments within the current sampling period; The average slope is obtained by weighting the first slope, the second slope, and the third slope according to a preset linear coefficient. The current integral increment is calculated based on the average slope and the preset sampling period.

[0011] Furthermore, the integral estimate of the battery SOC is corrected using the correction value, including: Calculate the difference between the correction value and the integral estimate; When the difference is greater than the preset correction threshold, the battery SOC is updated to the correction value; When the difference is less than or equal to the preset correction threshold, the correction value and the integral estimate are weighted and fused according to the preset weight to obtain the corrected battery SOC.

[0012] An electronic device includes a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the steps of the method.

[0013] A readable non-transitory storage medium storing a program or instructions that, when executed by a processor, implement the steps of the method.

[0014] The present invention has the following beneficial effects: In this invention, by identifying the charging, discharging, and resting conditions of the energy storage battery, ampere-hour integration is performed under the charging and discharging conditions, and closed-loop correction of the State of Charge (SOC) is performed using the open-circuit voltage under the resting condition. This can eliminate the error accumulated by the ampere-hour integration over a long period of time and improve the accuracy of SOC estimation. Attached Figure Description

[0015] Figure 1This diagram illustrates the steps of the proposed method for accurate SOC estimation of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method. Detailed Implementation

[0016] 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, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1 As shown, this invention is a method for accurately estimating the State of Charge (SOC) of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method, comprising the following steps: The real-time operating parameters of the energy storage battery in the photovoltaic water supply system are obtained, including battery current, battery terminal voltage and ambient temperature. The current operating condition of the energy storage battery is identified based on the battery current and the battery terminal voltage. The operating conditions include charging, discharging, and resting conditions. When the energy storage battery is in charging or discharging condition, the battery current is integrally calculated based on the ampere-hour integration method to obtain the integral estimate of the battery SOC. The battery capacity is temperature compensated according to the ambient temperature, and the charging efficiency and discharging efficiency are set according to the charging and discharging state of the energy storage battery. More specifically, the output power of the photovoltaic array is obtained, and the charging state of the energy storage battery is predicted based on the output power of the photovoltaic array. When the predicted output power of the photovoltaic array is greater than a preset power threshold, it is determined that the energy storage battery is about to enter the charging state, and the sampling frequency of the ampere-hour integral is increased. When the energy storage battery is in charging mode and the battery current is less than the trickle current threshold, it is determined that the energy storage battery has entered a fully charged state, and the battery SOC is set to the preset full charge value. When the energy storage battery is in discharge mode and the battery terminal voltage reaches the discharge cutoff voltage, it is determined that the energy storage battery has entered the full discharge state, and the battery SOC is set to the preset full discharge value. When the energy storage battery is in a static state, the ampere-hour integration of the battery current is paused, the open-circuit voltage after the battery terminal voltage stabilizes is detected, the correction value of the battery SOC is obtained according to the mapping relationship between the open-circuit voltage and the battery SOC, and the integral estimate of the battery SOC is corrected using the correction value. The mapping relationship between the open-circuit voltage and the battery SOC is periodically updated according to the operating cycle of the energy storage battery. The update includes temperature correction of the mapping relationship between the open-circuit voltage and the battery SOC based on the ambient temperature. Output the integral estimate of the corrected battery SOC; When the integral estimated value of the battery SOC reaches the preset charging protection threshold, the charging circuit is controlled to stop charging or reduce the charging power. When the integral estimated value of the battery SOC is lower than the preset discharge protection threshold, the discharge circuit is controlled to stop discharging or reduce the discharge power.

[0018] In the specific implementation process, the photovoltaic water supply system includes a photovoltaic array, a solar charge and discharge controller, a battery pack and a water pump. The battery pack can be a lead-acid battery, a lithium-ion battery or other energy storage battery.

[0019] When there is sufficient sunlight, the photovoltaic array converts light energy into electrical energy, which is then used to charge the battery pack via a solar charge and discharge controller. The battery pack then powers the water pump at night or during cloudy or rainy weather, driving the pump to lift water.

[0020] Taking the demonstration project in the high-altitude pastoral area as an example, the photovoltaic array has an installed capacity of about 800W, and the battery pack can be formed by connecting four 12V / 150Ah lead-acid batteries in series to form a 48V / 600Ah battery pack. The water pump has a rated power of 600W.

[0021] The real-time operating parameters can be acquired by current sensors, voltage sensors, and temperature sensors in the battery management system. The current sensors can be shunt resistor current sensors or Hall effect current sensors to acquire the charging and discharging current of the battery pack. The voltage sensors are used to acquire the terminal voltage of the battery pack. The temperature sensors can be set on the surface of the battery pack or on the control board of the battery management system to acquire the ambient temperature.

[0022] When identifying operating conditions based on battery current and battery terminal voltage, the charging condition refers to the state where the photovoltaic array charges the battery and battery current flows into the battery; the discharging condition refers to the state where the battery discharges to loads such as water pumps and battery current flows out of the battery; the resting condition refers to the state where the battery is neither charging nor discharging and the current is close to zero. Under charging or discharging conditions, the battery current is integrated using the ampere-hour integration method, and the integral estimate of the battery SOC can be expressed as: ,in, Let be the state of charge at time t. The initial state of charge, For battery capacity, This refers to the charging and discharging current of the battery.

[0023] Because of the difference between the charging and discharging efficiencies of batteries, not all the electricity charged during charging can be converted into usable chemical energy. Therefore, charging and discharging efficiencies are set separately. During charging integration, the current term is multiplied by the charging efficiency, and during discharging integration, the current term is multiplied by the discharging efficiency, thereby improving the accuracy of ampere-hour integration. Simultaneously, temperature compensation is applied to the battery capacity based on ambient temperature to avoid SOC estimation errors caused by capacity reduction at low temperatures. Under static conditions, no current flows into or out of the battery, and the battery terminal voltage stabilizes after a period of rest. This battery terminal voltage is the open-circuit voltage. A definite mapping relationship exists between the open-circuit voltage and the battery SOC. The correction value for the battery SOC can be obtained from a table using the open-circuit voltage, and this correction value is used to correct the integrated estimate obtained from ampere-hour integration, thereby eliminating accumulated errors.

[0024] In one embodiment, identifying the current operating condition of the energy storage battery based on the battery current and the battery terminal voltage includes: When the battery current is greater than the first current threshold and the battery terminal voltage shows an upward trend, it is determined that the energy storage battery is in charging condition. When the battery current is less than the second current threshold and the battery terminal voltage shows a downward trend, it is determined that the energy storage battery is in a discharge state. When the absolute value of the battery current is less than the static current threshold and the duration reaches the preset static time, the energy storage battery is determined to be in static condition. After determining that the energy storage battery is in a static operating condition: Determine whether the resting time of the energy storage battery has reached the preset stabilization time; When the settling time reaches the preset stabilization time, the battery terminal voltage is collected as the open circuit voltage; When the change in ambient temperature during the settling period exceeds a preset temperature change threshold, the preset stabilization time is restarted.

[0025] In one embodiment, temperature compensation for battery capacity based on the ambient temperature includes: Based on the preset mapping relationship between ambient temperature and temperature correction coefficient, determine the temperature correction coefficient corresponding to the current ambient temperature; Multiply the rated capacity of the energy storage battery by the temperature correction factor to obtain the corrected capacity at the current ambient temperature. The ampere-hour integral is calculated based on the corrected capacity.

[0026] In one embodiment, the battery current is calculated by integration based on the ampere-hour integration method, including: The battery current is collected according to a preset sampling period; The current integral increment within each sampling period is calculated using a multi-step numerical integration method, which is based on a weighted combination of current sampling values ​​at the current sampling time and its neighboring sampling times.

[0027] In one embodiment, a multi-step numerical integration method is used to calculate the current integral increment within each sampling period, including: Obtain the first slope corresponding to the current sample value at the current sampling moment; Obtain the second and third slopes corresponding to the current sample values ​​at least two intermediate moments within the current sampling period; The average slope is obtained by weighting the first slope, the second slope, and the third slope according to a preset linear coefficient. The current integral increment is calculated based on the average slope and the preset sampling period.

[0028] In one embodiment, correcting the integral estimate of the battery SOC using the correction value includes: Calculate the difference between the correction value and the integral estimate; When the difference is greater than the preset correction threshold, the battery SOC is updated to the correction value; When the difference is less than or equal to the preset correction threshold, the correction value and the integral estimate are weighted and fused according to the preset weight to obtain the corrected battery SOC.

[0029] An electronic device includes a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the steps of the method.

[0030] A readable non-transitory storage medium storing a program or instructions that, when executed by a processor, implement the steps of the method.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for accurately estimating the State of Charge (SOC) of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integral method, characterized in that... Includes the following steps: The real-time operating parameters of the energy storage battery in the photovoltaic water supply system are obtained, including battery current, battery terminal voltage and ambient temperature. The current operating condition of the energy storage battery is identified based on the battery current and the battery terminal voltage. The operating conditions include charging, discharging, and resting conditions. When the energy storage battery is in charging or discharging condition, the battery current is integrally calculated based on the ampere-hour integration method to obtain the integral estimate of the battery SOC. The battery capacity is temperature compensated according to the ambient temperature, and the charging efficiency and discharging efficiency are set according to the charging and discharging state of the energy storage battery. When the energy storage battery is in a static state, the ampere-hour integration of the battery current is paused, the open-circuit voltage after the battery terminal voltage stabilizes is detected, the correction value of the battery SOC is obtained according to the mapping relationship between the open-circuit voltage and the battery SOC, and the integral estimate of the battery SOC is corrected using the correction value. Output the integral estimate of the corrected battery SOC.

2. The method for accurate estimation of SOC of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method according to claim 1, characterized in that, Identifying the current operating condition of the energy storage battery based on the battery current and the battery terminal voltage includes: When the battery current is greater than the first current threshold and the battery terminal voltage shows an upward trend, it is determined that the energy storage battery is in charging condition. When the battery current is less than the second current threshold and the battery terminal voltage shows a downward trend, it is determined that the energy storage battery is in a discharge state. When the absolute value of the battery current is less than the static current threshold and the duration reaches the preset static time, the energy storage battery is determined to be in static condition.

3. The method for accurate estimation of SOC of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method according to claim 1, characterized in that, Temperature compensation for battery capacity based on the ambient temperature includes: Based on the preset mapping relationship between ambient temperature and temperature correction coefficient, determine the temperature correction coefficient corresponding to the current ambient temperature; Multiply the rated capacity of the energy storage battery by the temperature correction factor to obtain the corrected capacity at the current ambient temperature. The ampere-hour integral is calculated based on the corrected capacity.

4. The method for accurate estimation of SOC of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method according to claim 1, characterized in that, The battery current is calculated by integrating using the ampere-hour integration method, including: The battery current is collected according to a preset sampling period; The current integral increment within each sampling period is calculated using a multi-step numerical integration method, which is based on a weighted combination of current sampling values ​​at the current sampling time and its neighboring sampling times.

5. The method for accurate estimation of SOC of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method according to claim 1, characterized in that, The multi-step numerical integration method is used to calculate the integral increment of the current in each sampling period, including: Obtain the first slope corresponding to the current sample value at the current sampling moment; Obtain the second and third slopes corresponding to the current sample values ​​at least two intermediate moments within the current sampling period; The average slope is obtained by weighting the first slope, the second slope, and the third slope according to a preset linear coefficient. The current integral increment is calculated based on the average slope and the preset sampling period.

6. The method for accurate estimation of SOC of photovoltaic water supply batteries in pastoral areas based on the ampere-hour integration method according to claim 1, characterized in that, The integral estimate of the battery's SOC is corrected using the correction value, including: Calculate the difference between the correction value and the integral estimate; When the difference is greater than the preset correction threshold, the battery SOC is updated to the correction value; When the difference is less than or equal to the preset correction threshold, the correction value and the integral estimate are weighted and fused according to the preset weight to obtain the corrected battery SOC.

7. An electronic device, characterized in that, It includes a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the steps of the method as described in claim 1.

8. A readable non-transitory storage medium, characterized in that, The storage medium stores a program or instructions that, when executed by a processor, implement the steps of the method as described in claim 1.

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