Photovoltaic battery charge-discharge automatic regulation method

Abstract

The application relates to the field of photovoltaic energy storage and discloses a photovoltaic battery charge-discharge automatic regulation method, which comprises the following steps: obtaining a direct-current bus voltage measurement value, a photovoltaic converter input power and a load power demand value; generating a bus voltage regulation current reference value based on a voltage deviation; obtaining a battery temperature and a state of charge, determining a current swing rate limit value according to a charge acceptance capacity mapping table; completing clamping of a reference value change rate through asymmetric limiting logic, and determining a battery current control target value; calculating a deviation between the reference value and the target value to generate a photovoltaic power regulation instruction, and absorbing transient electric energy by using a bus capacitor; the application avoids the risk of concentration polarization of the battery, reduces the shedding of active substances on the plate, prolongs the cycle life of the energy storage unit, and improves the system operation robustness through the collaborative disturbance resistance of the energy source and the storage end.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic energy storage and distribution technology, and particularly relates to an automatic regulation method for charging and discharging photovoltaic batteries. Background Technology

[0002] Currently, stand-alone photovoltaic (PV) systems are widely used in remote areas and microgrid environments. In these systems, energy storage batteries are connected to the DC bus via a bidirectional DC-DC converter. A dual closed-loop control structure consisting of an outer loop for bus voltage and an inner loop for current is used to adjust the duty cycle of the bidirectional DC-DC converter and maintain the stability of the DC bus voltage. In actual operation, millisecond-level power surges are caused by moving cloud cover or instantaneous switching of nonlinear loads. Existing control strategies aim to maintain rigid stability of the bus voltage by driving the bidirectional DC-DC converter to inject the power difference into the battery. This approach ignores the physical constraint that the solid-phase diffusion rate of lithium ions penetrating the interface film inside the battery is much lower than the charge transfer rate of the circuit layer. The physical impedance mismatch across time scales causes high-frequency surge currents to cross the electrochemical interface before the diffusion gradient is established, leading to concentration polarization and shortening cycle life. Conventional methods such as increasing the bypass capacitor capacity or increasing the controller bandwidth are constrained by system cost and size. Simply increasing the control frequency exacerbates the accumulation of polarization potential, leading to the shedding of active materials.

[0003] The aforementioned improvements to hardware topology or passive buffer components not only increase system deployment costs but also make it difficult to effectively improve power density within limited space. Therefore, the focus of technological improvement has gradually shifted to in-depth optimization of control strategies. For example, Chinese invention patent application CN121643044A discloses an adaptive charge-discharge coordinated control method and system for energy storage batteries. This method dynamically corrects the absolute amplitude limit of the current by sensing the SOC state and combines cross-loop anti-saturation logic to suppress command overshoot caused by control loop saturation. However, this amplitude control logic based on static boundaries still fails to address the dynamic hysteresis characteristics of lithium-ion solid-phase diffusion at the electrochemical interface at its underlying mechanism. Even if the current amplitude is within safe limits, if its transient slew rate exceeds the physical upper limit of charge acceptance, the electrode surface will still experience concentration polarization due to the instantaneous imbalance of the ion migration gradient, further exacerbating the shedding of active materials. Because this solution lacks dynamic protection of the current change rate dimension, it is difficult to achieve essential protection of the battery's internal interface integrity when facing millisecond-level power fluctuations.

[0004] Therefore, the technical problem to be solved by this invention is how to match the power injection rate with the electrochemical acceptance rate, and construct an active channeling mechanism for transient power fluctuations while ensuring the energy balance of the system, so as to achieve dynamic protection of the physical boundary of battery charging and discharging. Summary of the Invention

[0005] This invention provides an automatic adjustment method for charging and discharging photovoltaic batteries, comprising: Step 101: Obtain the measured values ​​of the DC bus voltage, the input power of the photovoltaic converter, the output current of the photovoltaic array, and the load power requirement of the load converter; Step 102: Calculate the voltage deviation between the measured bus voltage value and the preset voltage reference value, and generate a reference value for bus voltage regulation current based on the voltage deviation through proportional-integral calculation; Step 103: Obtain the real-time temperature measurement value and the real-time state of charge value of the battery, and search for the value that matches the real-time temperature measurement value and the real-time state of charge value in the preset charge acceptance capacity mapping table to determine the current slew rate limit of the battery. Step 104: The rate of change of the bus voltage regulation current reference value is clamped by asymmetric limiting logic so that the dynamic change trajectory of the bus voltage regulation current reference value is within the numerical range defined by the current slew rate limit, thereby obtaining the target value of battery current control. Step 105: Calculate the current deviation between the reference value of the bus voltage regulation current and the target value of the battery current control, and generate a photovoltaic power regulation command to reduce the output power of the photovoltaic converter based on the current deviation. At the same time, absorb the transient electrical energy corresponding to the current deviation through the DC bus capacitor to regulate the charging and discharging ripple current of the battery.

[0006] Preferably, in step 103, determining the current slew rate limit of the battery includes the following steps: Step 1031: Obtain the rate of change of the battery's terminal voltage and the rate of change of the charging and discharging current, and calculate the ratio of the rate of change of the terminal voltage to the rate of change of the charging and discharging current to obtain the transient impedance characteristic quantity; Step 1032: Use the transient impedance characteristic quantity, the real-time temperature measurement value, and the real-time state of charge value as indexes to match and obtain the charge accepting capacity coefficient in a preset charge accepting capacity mapping table; Step 1033: Reduce the preset maximum current change rate by the charge accepting capacity coefficient to obtain the current slew rate limit.

[0007] Preferably, in step 104, the rate of change of the bus voltage regulating current reference value is clamped by asymmetric limiting logic, and processed according to the following rules: if the rate of change of the bus voltage regulating current reference value is within the current slew rate limit, the battery current control target value is set to be equal to the bus voltage regulating current reference value; if the rate of change of the bus voltage regulating current reference value exceeds the current slew rate limit, the bus voltage regulating current reference value is truncated according to the boundary value of the current slew rate limit, and the truncated value is set as the battery current control target value.

[0008] Preferably, the method further includes the following steps: Step 106: Real-time monitoring of the terminal voltage of the DC bus capacitor; Step 107: When the terminal voltage exceeds the preset safety threshold limit, outputting a power blocking command to the photovoltaic converter and outputting a power compensation command to the load-side converter.

[0009] Preferably, in the preset charge accepting capacity mapping table, the charge accepting capacity coefficient decreases monotonically as the real-time temperature measurement value decreases, and decreases monotonically as the real-time state of charge value increases.

[0010] Preferably, the target value of the battery current control is used as the control input of the bidirectional DC-DC converter, and the charging and discharging power of the battery is adjusted by adjusting the duty cycle of the switching transistor of the bidirectional DC-DC converter.

[0011] Preferably, the bus voltage regulation current reference value is calculated using a proportional-integral control law. The instantaneous current required to maintain the DC bus power balance is determined by calculating the sum of the proportional gain term and the integral accumulation term of the voltage deviation.

[0012] Preferably, the electrical energy corresponding to the current deviation is jointly absorbed through the charging and discharging process of the DC bus capacitor and the power derating process of the photovoltaic converter to compensate for the power gap caused by the current slew rate limit of the battery.

[0013] Preferably, the current slew rate limit includes a charging current slew rate limit and a discharging current slew rate limit, wherein the absolute value of the charging current slew rate limit is less than the absolute value of the discharging current slew rate limit.

[0014] Compared with existing technologies, the automatic charging and discharging regulation method for photovoltaic batteries of the present invention has the following advantages: 1. In the automatic regulation of photovoltaic battery charging and discharging, by establishing the correlation between the DC bus voltage change rate and the physical limit of battery charge acceptance, a physical balance between circuit energy throughput and electrochemical response lag on the time scale is achieved. This method breaks the design inertia of the battery absorbing all system power fluctuations in real time in traditional technology. It uses the DC bus side capacitor as a transient buffer path for high-frequency energy. When a drastic change in system power is detected and its slew rate exceeds the battery dynamic limit, the excess energy is actively guided to converge to the bus capacitor through the asymmetric clamping logic at the instruction level. This mechanism cuts off the conduction link of high-frequency ripple current to the battery without changing the existing circuit hardware topology, avoids the polarization overpotential generated by the battery plates forcibly passing through the high-frequency current, reduces the risk of active material shedding and thermal runaway, and extends the physical cycle life of the energy storage unit.

[0015] 2. A dynamic threshold correction mechanism based on a multi-dimensional mapping of ambient temperature and state of charge is adopted to improve the system's robustness under extreme and complex operating conditions. This method uses a pre-stored dynamic mapping matrix to extract the charge acceptance coefficient of the battery in the current physical state in real time, transforming the static current protection limit into a hard boundary that dynamically migrates with the physical environment. This processing method enables the control unit to sense the nonlinear shift of the battery's internal electrochemical characteristics with decay and temperature changes, ensuring that the charging and discharging commands are always locked within the battery's physical safety envelope. When the ambient temperature or remaining charge approaches the physical limit, the system achieves precise adaptation between the control strategy and the battery's actual physical acceptance capacity by proportionally shrinking the limiting threshold.

[0016] 3. Construct a system-level collaborative anti-disturbance mechanism from the energy source to the storage end to eliminate the hidden danger of energy accumulation during high power fluctuations. By performing current slew rate clamping on the battery side and simultaneously coordinating the impedance reconstruction action on the photovoltaic array side, the system has the energy conduction capability of source-load-storage integration. When the energy storage side enters the duty cycle blocking state due to the protection mechanism and the bus voltage faces the risk of continuous overvoltage, the control command guides the photovoltaic converter to exit the maximum power point tracking state and artificially reduces the input power by injecting voltage bias. This cross-module collaborative logic closed loop not only ensures the electrical stability of the DC bus, but also establishes an energy balance guarantee system at the system level that does not rely on additional consumption components. Attached Figure Description

[0017] Figure 1 This is a flowchart of the automatic adjustment and cooperative anti-disturbance control of photovoltaic battery charging and discharging according to the present invention; Figure 2 This is a logic diagram for offline calibration and real-time limit determination of the charge acceptance capability mapping table of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0019] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood in conjunction with the specific circumstances.

[0021] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0022] An automatic regulation method for charging and discharging photovoltaic batteries, comprising: Step 101: Obtain the measured values ​​of the DC bus voltage, the input power of the photovoltaic converter, the output current of the photovoltaic array, and the load power requirement of the load converter; Step 102: Calculate the voltage deviation between the measured bus voltage value and the preset voltage reference value, and generate a reference value for bus voltage regulation current based on the voltage deviation through proportional-integral calculation; Step 103: Obtain the real-time temperature measurement value and the real-time state of charge value of the battery, and search for the value that matches the real-time temperature measurement value and the real-time state of charge value in the preset charge acceptance capacity mapping table to determine the current slew rate limit of the battery. Step 104: The rate of change of the bus voltage regulation current reference value is clamped by asymmetric limiting logic so that the dynamic change trajectory of the bus voltage regulation current reference value is within the numerical range defined by the current slew rate limit, thereby obtaining the target value of battery current control. Step 105: Calculate the current deviation between the reference value of the bus voltage regulation current and the target value of the battery current control, and generate a photovoltaic power regulation command to reduce the output power of the photovoltaic converter based on the current deviation. At the same time, absorb the transient electrical energy corresponding to the current deviation through the DC bus capacitor to regulate the charging and discharging ripple current of the battery.

[0023] Preferably, in step 103, determining the current slew rate limit of the battery includes the following steps: Step 1031: Obtain the rate of change of the battery's terminal voltage and the rate of change of the charging and discharging current, and calculate the ratio of the rate of change of the terminal voltage to the rate of change of the charging and discharging current to obtain the transient impedance characteristic quantity; Step 1032: Use the transient impedance characteristic quantity, the real-time temperature measurement value, and the real-time state of charge value as indexes to match and obtain the charge accepting capacity coefficient in a preset charge accepting capacity mapping table; Step 1033: Reduce the preset maximum current change rate by the charge accepting capacity coefficient to obtain the current slew rate limit.

[0024] Preferably, in step 104, the rate of change of the bus voltage regulating current reference value is clamped by asymmetric limiting logic, and processed according to the following rules: if the rate of change of the bus voltage regulating current reference value is within the current slew rate limit, the battery current control target value is set to be equal to the bus voltage regulating current reference value; if the rate of change of the bus voltage regulating current reference value exceeds the current slew rate limit, the bus voltage regulating current reference value is truncated according to the boundary value of the current slew rate limit, and the truncated value is set as the battery current control target value.

[0025] Preferably, the method further includes the following steps: Step 106: Real-time monitoring of the terminal voltage of the DC bus capacitor; Step 107: When the terminal voltage exceeds the preset safety threshold limit, outputting a power blocking command to the photovoltaic converter and outputting a power compensation command to the load-side converter.

[0026] Preferably, in the preset charge accepting capacity mapping table, the charge accepting capacity coefficient decreases monotonically as the real-time temperature measurement value decreases, and decreases monotonically as the real-time state of charge value increases.

[0027] Preferably, the target value of the battery current control is used as the control input of the bidirectional DC-DC converter, and the charging and discharging power of the battery is adjusted by adjusting the duty cycle of the switching transistor of the bidirectional DC-DC converter.

[0028] Preferably, the bus voltage regulation current reference value is calculated using a proportional-integral control law. The instantaneous current required to maintain the DC bus power balance is determined by calculating the sum of the proportional gain term and the integral accumulation term of the voltage deviation.

[0029] Preferably, the electrical energy corresponding to the current deviation is jointly absorbed through the charging and discharging process of the DC bus capacitor and the power derating process of the photovoltaic converter to compensate for the power gap caused by the current slew rate limit of the battery.

[0030] Preferably, the current slew rate limit includes a charging current slew rate limit and a discharging current slew rate limit, wherein the absolute value of the charging current slew rate limit is less than the absolute value of the discharging current slew rate limit.

[0031] Example 1: In a high-altitude independent photovoltaic energy storage microgrid system, the light intensity is abruptly blocked by rapidly moving clouds, causing a transient power difference between the input power measurement of the photovoltaic converter and the load power demand of the load converter. Conventional control architectures, in order to maintain a constant DC bus voltage, generate a bus voltage regulation current reference value based on the conventional voltage deviation, which is not constrained by the rate of current change. This causes the battery to absorb all high-frequency power fluctuations, resulting in a physical impedance mismatch between the microsecond-level charge transfer rate of the circuit system and the hundreds of millisecond-level solid-phase ion diffusion rate inside the battery. High-frequency inrush currents penetrate the electrode interface, inducing concentration polarization and accelerating the shedding of active materials. This issue needs to be addressed in this system. In the lead-acid battery assembly specifically selected in the embodiment, the mismatch between the charge transfer rate of the microsecond-level circuit and the internal physical diffusion rate is specifically manifested in the fact that the liquid-phase migration and solid-phase precipitation reaction of sulfate ions inside the porous electrode lags behind the high-frequency charge exchange on the electrode surface. When subjected to a millisecond-level transient high current impact, the consumption rate of active ions in the micropores of the electrode far exceeds the rate of diffusion and replenishment of the deep bulk electrolyte to the micro-region, inducing local concentration polarization. This generalized diffusion channel congestion mechanism based on porous electrodes completely follows the physical nature of the slow solid-phase ion transport in the overall dynamic response, thereby enabling the energy buffer regulation control architecture to play a role across the differences in specific battery chemical systems.

[0032] The system acquires the measured values ​​of the DC bus voltage, the input power of the photovoltaic converter, the output current of the photovoltaic array, and the load power demand of the load converter. It calculates the voltage deviation between the measured bus voltage and a preset voltage reference value. Based on this voltage deviation, it generates a reference value for the bus voltage regulation current through proportional-integral calculations. The system also acquires the real-time temperature and state-of-charge (SOC) values ​​of the battery. It retrieves values ​​matching these values ​​from a preset charge-acceptance capacity mapping table to determine the battery's current slew rate limit. The asymmetric limiting logic adjusts the bus voltage based on this current slew rate limit. The rate of change of the current reference value is clamped. Based on the recursive differential principle of digital discrete sampling control, the load converter control sampling period is set. The reference value of the bus voltage regulation current in the current k-th control cycle and the target value of the output battery current control in the previous sampling cycle are extracted. The difference between the two is calculated to obtain the unconstrained differential increment. The transient rate of change is determined according to the differential inequality: if the ratio of the absolute value of the unconstrained differential increment to the control sampling period is less than or equal to the current slew rate limit, the target value of the battery current control in this cycle is equal to the current reference value of the bus voltage regulation current; if the ratio is greater than the current slew rate limit, the discrete truncation formula is called. Force update the target value, where, and These respectively represent the execution amount of the battery current control target in the current control cycle and the previous control cycle. Characterizing the unconstrained differential increment of the current period, Characterization and retrieval yielded the current slew rate limit. Characterizes the fixed-set control sampling period time. To extract dimensionless sign functions with positive and negative attributes, the value range is limited to -1, 0, and 1. This discrete truncation procedure serves as a hard instruction constraint, filtering out high-frequency fluctuation components exceeding the electrochemical response limit. The target value for battery current control is output, and the current deviation between the bus voltage regulation current reference value and the battery current control target value is calculated. Based on this current deviation, the system generates a photovoltaic power regulation command to reduce the output power of the photovoltaic converter. Based on Kirchhoff's nodal current law and the capacitor voltage integration mechanism, the high-frequency deviation current blocked by the amplitude-limited command is forcibly injected into the DC bus capacitor along the path of lowest transient impedance. A hardware voltage feedforward comparison loop is constructed inside the photovoltaic converter to acquire the analog signal of the DC bus capacitor terminal voltage in real time. When the transient rise slope of the terminal voltage reaches the preset hardware overvoltage protection safety boundary, the conventional maximum power point tracking algorithm is bypassed through the gate-level hardware interrupt channel, based on the overvoltage deviation amplitude... A negative compensation duty cycle is injected into the pulse width modulation drive side of the photovoltaic converter to reduce the single-cycle conduction time of the switching transistor. The hardware voltage feedforward comparison loop specifically uses a high-speed operational amplifier to build a subtraction analog circuit. The analog signal of the DC bus capacitor voltage is compared with the hardware-set safety reference level. When a positive over-limit deviation occurs, the output analog difference voltage is calculated by the proportional scaling multiplication of a high-precision resistor voltage divider network and linearly converted into the corresponding reverse bias control voltage. This bias voltage is directly hard-wired to the error amplifier feedback pin of the photovoltaic converter's pulse width modulation chip, thereby establishing an instantaneous and linear mathematical and geometric mapping relationship between the overvoltage deviation analog quantity and the negative duty cycle reduction coefficient. The source-side derating power blocking execution response cycle is compressed to within the bus capacitor withstand voltage limit breakdown time constant, and the transient electrical energy corresponding to the current deviation is absorbed by the DC bus capacitor.

[0033] When the rate of change of the bus voltage regulation current reference value exceeds the current slew rate limit due to light fluctuations, the system cuts off the bus voltage regulation current reference value according to the current slew rate limit to prevent high-frequency ripple current from being injected into the battery. The corresponding electrical energy is absorbed by the DC bus capacitor through the terminal voltage rise. The photovoltaic converter deviates from the maximum power point according to the photovoltaic power regulation command to reduce the energy source input. The reduction in the output power of the photovoltaic converter and the energy storage of the DC bus capacitor together absorb the power gap caused by the limited battery current, eliminate the physical impact of high-frequency large current on the electrochemical interface of the plates, and reduce the active material shedding rate. The power supply circuit device uses the charging and discharging command generation timing and multi-path energy flow distribution logic to match the transient electromagnetic energy slew rate of the system and the physical inertia of battery charge acceptance, ensuring the physical cycle life of the energy storage unit while maintaining the DC bus power balance.

[0034] Example 2: In a high-altitude independent photovoltaic energy storage microgrid system, an automatic battery charging and discharging regulation method under transient light disturbance conditions was tested. A physical verification environment was constructed using a hardware-in-the-loop real-time simulation test platform. The platform included a programmable DC power supply with a measurement bandwidth greater than 10kHz connected to a lead-acid battery pack with a rated voltage of 48V and a rated capacity of 200Ah. A bidirectional DC-DC converter with a switching frequency of 20kHz and a DC bus capacitor with a capacitance of 4700μF were used. The test conditions simulated typical industrial electromagnetic environments. The disturbance is introduced by superimposing Gaussian white noise with a signal-to-noise ratio of 20dB and power frequency interference harmonics with a frequency of 50Hz into the basic light intensity test sequence. The light intensity input is set to drop from 1000W / m² to 200W / m² within 50ms to generate a power drop at the source end. The system sampling period is set to take into account both the real-time performance of data acquisition and the system's computational load. When the light intensity drop slope is greater than 10kW / (m²·s), the system sets the sampling period to 100μs according to the Nyquist sampling theorem to meet the aliasing-free acquisition requirements of high-frequency transient current changes.

[0035] The test process included the collection and comparison of data from a control group and an experimental group. The control group employed a dual closed-loop control mechanism with an outer voltage loop and an inner current loop, without current slew rate constraints. Measurement data indicated that at the moment of light drop, the reference value of the bus voltage regulation current generated by the control group increased sharply at a rate of 1500 A / s. The peak value of the measured transient current during battery charging and discharging reached 85 A. The injection of the original input current, including high-frequency noise, into the battery plates caused an increase in polarization resistance. The experimental group system acquired the measured values ​​of the DC bus voltage, the input power of the photovoltaic converter, the output current of the photovoltaic array, and the load power demand of the load converter. The measured values ​​of the bus voltage were then compared with the preset voltage reference value. Voltage deviation is calculated using proportional-integral operations to generate a reference value for bus voltage regulation current. Simultaneously, the real-time temperature measurement of the battery (25℃) and the real-time state of charge (60%) are acquired. Matching values ​​are retrieved from a preset charge acceptance capacity mapping table to set the battery current slew rate limit to 120A / s. Asymmetric limiting logic determines that the transient rate of change of the bus voltage regulation current reference value exceeds the limit and clamps the rate of change to 120A / s, outputting the target value for battery current control. Measurement results show that the measured peak transient current of the test group battery is maintained at 45A, and 20dB of Gaussian white noise and 50Hz power frequency disturbance are limited by the clamping logic and do not enter the battery.

[0036] The system calculates the current deviation between the reference value of the bus voltage regulation current and the target value of the battery current control, and finds that the maximum transient current deviation is 40A. Based on the current deviation, the system generates a photovoltaic power regulation command to drive the photovoltaic converter away from the maximum power point to reduce the power output at the source. Simultaneously, the DC bus capacitor is mobilized to absorb the transient energy corresponding to the current deviation. The measured rise of the DC bus terminal voltage is 12V, which is within the safe allowable margin of 15V. Multiple out-of-range control groups are set for the current slew rate limit to test the parameter boundaries and gradient test. Data shows that when the set current slew rate limit increases from 120A / s to 250A / s, the increase in polarization resistance on the electrode surface is linear. When the set current slew rate limit crosses the 300A / s inflection point, the measured value of polarization resistance jumps exponentially and is accompanied by a local increase in electrolyte temperature, breaking through the physical limit of solid-phase ion diffusion rate. The test confirms that the 120A / s current slew rate limit obtained by retrieving the real-time temperature measurement value and the real-time state of charge value suppresses the impact of high-frequency power fluctuations on the electrode interface and ensures the physical cycle life of the energy storage unit.

[0037] Example 3: In the commissioning preparation stage of the photovoltaic energy storage dispatching system, in order to eliminate the dynamic uncertainty of the battery charge and discharge boundary under real-time operating conditions, the system executes an offline calibration program to construct a preset charge acceptance capacity mapping table. The test system selects lead-acid batteries with physical specifications that are completely consistent with the actual operating energy storage units as calibration samples, and establishes a parameter traversal matrix covering high-altitude application environments. The temperature dimension of the parameter traversal matrix spans the range of -20℃ to 50℃ and is set with a step size of 5℃. The state of charge dimension spans the range of 10% to 100% and is set with a step size of 10%. The test system relies on a constant temperature chamber and a charge and discharge tester to adjust the calibration sample to a specific target intersection point in the parameter traversal matrix, maintaining the internal thermodynamic state of the calibration sample to achieve physical equilibrium.

[0038] The testing system injects a test current step signal of a predetermined waveform into the calibration sample, simultaneously acquiring the rate of change of the terminal voltage and the rate of change of the charging and discharging current of the calibration sample. The transient impedance characteristic is calculated by dividing these rates by the rate of change of the charging and discharging current. The test current step signal of the predetermined waveform contains a transient excitation with an extremely short rise time. By introducing a time-domain separation measurement mechanism, the system deliberately extracts the long-tail response stage data after the initial millisecond-level time window following the step occurrence. During this lag period, both the pure ohmic polarization response and the charge-discharge effect of the double-layer electrode at the plate interface have been fully established and reached their maximum values. In steady state, the ratio of the rate of change of the terminal voltage to the rate of change of the charging and discharging current, measured by dynamic sampling, is physically precisely separated, thus uniquely corresponding to the concentration polarization impedance dominated by surface ion diffusion inside the electrode. Through this time-domain truncation and separation extraction step, the overall external characteristic circuit parameters are successfully and uniquely mapped to the surface characteristic parameters of solid-phase ion diffusion. The test system successively increases the rate of change of the test current step signal in increments of 5 A / s, continuously monitoring the transient impedance characteristic values ​​at each increment step. When the transient impedance characteristic value is detected... When the value of the previous test step changes by more than 15%, the solid-phase ion diffusion channels at the interface of the electrode plate inside the calibration sample encounter the congestion limit. The concentration polarization effect undergoes a physical surge at this rate of change. This threshold for judging a sudden change of more than 15% is based on the physical failure lower limit boundary established by a large number of electrochemical destructive calorimetric experiments on a group of lead-acid batteries of the same specification. Experimental data verify that when the transient impedance increase instantaneously exceeds this 15% critical region, the accompanying gas evolution side reaction and the local temperature surge of the electrode plate trigger an irreversible active material reaction. The system softens and detaches the battery. Simultaneously, through the factory first-cycle calibration test, the system pre-extracts the steady-state impedance value in the impedance stable response region under the initial healthy state of the battery. After taking its reciprocal and normalizing the value, it generates the preset voltage change rate reciprocal constant used in Example 4. This establishes an accurate engineering comparison zero-point basis for the subsequent calculation of the aging degradation ratio. The test system extracts the current change rate value corresponding to the previous test step that induces the jump, and establishes the current change rate value as the reference current slew rate limit value under specific temperature and specific charging state.

[0039] The test system iterates through all intersections of the parameter traversal matrix and repeatedly executes high-frequency step detection and impedance jump discrimination logic to obtain a set of reference current slew rate limits covering the entire operating range. The system writes the real-time temperature measurement, real-time state of charge, transient impedance characteristics, and calibrated reference current slew rate limits corresponding to each intersection point into non-volatile memory, generating a preset charge accepting capacity mapping table with a multi-dimensional data structure. Before generating this multi-dimensional data structure, the system internally executes a data conversion algorithm to divide the calibrated reference current slew rate limits obtained at all intersections by the theoretical value of the absolute physical limit current change rate measured at a standard reference room temperature of 25°C and under 100% charge for this type of battery. After this normalized division operation, a series of dimensionless scaling factors between 0 and 1 are obtained. These factors are recorded as the charge accepting capacity coefficients mentioned earlier. The coefficient is embedded in the mapping table. When the system is called during operation, it multiplies the coefficient with the preset maximum value of the system current change rate to reversely deduce and restore the accurate current slew rate limit that meets the current safety envelope requirements. In the offline calibration process of constructing the preset charge acceptance capacity mapping table, the extreme value of the physical change of transient impedance characteristic quantity is used as the benchmark for determining the solid phase ion diffusion congestion limit. When a jump occurs, the corresponding benchmark current slew rate limit is confirmed and the data dimension is reduced. It is then used as the quantitative current limiting threshold and embedded in the mapping table. During real-time operation, the power supply circuit device reads the real-time physical state of the DC bus and energy storage nodes, searches the preset charge acceptance capacity mapping table through numerical interpolation algorithm, and outputs the current slew rate limit that matches the current electrochemical state. The offline calibration and online retrieval collaborative mechanism eliminates the blind spots of fixed current limiting empirical parameters and anchors the battery charging and discharging current constraint logic to the real physicochemical response boundary.

[0040] Example 4: When the system faces the pre-deployment and commissioning conditions of a photovoltaic energy storage microgrid, the system drives the bidirectional DC-DC converter to inject a test current pulse with an amplitude of 10A and a pulse width of 5ms into the DC bus, simultaneously acquiring the peak value of the bus voltage ripple generated by the DC bus and the current rise delay time of the battery response pulse; the system divides the peak value of the bus voltage ripple by the current rise delay time to calculate the voltage change slope; based on this, the system multiplies the voltage change slope by a preset reciprocal constant of the voltage change rate to calculate the field impedance compensation coefficient. ,in It is a dimensionless scalar; therefore, the system will Multiply by all reference current slew rate limits covered by the preset charge acceptance capability mapping table in the memory to generate a field-specific mapping table.

[0041] During continuous operation, the system accumulates and records the battery's charge throughput using an ampere-hour integration module. When the charge throughput reaches a cycle node of 5000 Ah, the system injects a test current pulse into the DC bus again during the photovoltaic converter's sleep window, and simultaneously recalculates the field impedance compensation coefficient. Based on this, the system uses the recalculated... The field-specific mapping table in the memory is updated; thus, the system clamps the bus voltage and adjusts the rate of change of the current reference value according to the updated current slew rate limit, so that the trajectory of the transient power command is within the solid-phase ion diffusion physical boundary that the battery drifts with the increase of cycles.

[0042] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A method for automatic adjustment of charging and discharging of a photovoltaic battery, characterized in that, include: Step 101: Obtain the measured values ​​of the DC bus voltage, the input power of the photovoltaic converter, the output current of the photovoltaic array, and the load power requirement of the load converter; Step 102: Calculate the voltage deviation between the measured bus voltage value and the preset voltage reference value, and generate a reference value for bus voltage regulation current based on the voltage deviation through proportional-integral calculation; Step 103: Obtain the real-time temperature measurement value and the real-time state of charge value of the battery, and search for the value that matches the real-time temperature measurement value and the real-time state of charge value in the preset charge acceptance capacity mapping table to determine the current slew rate limit of the battery. Step 104: The rate of change of the bus voltage regulation current reference value is clamped by asymmetric limiting logic so that the dynamic change trajectory of the bus voltage regulation current reference value is within the numerical range defined by the current slew rate limit, thereby obtaining the target value of battery current control. Step 105: Calculate the current deviation between the reference value of the bus voltage regulation current and the target value of the battery current control, and generate a photovoltaic power regulation command to reduce the output power of the photovoltaic converter based on the current deviation. At the same time, absorb the transient electrical energy corresponding to the current deviation through the DC bus capacitor to regulate the charging and discharging ripple current of the battery. In step 103, determining the current slew rate limit of the battery includes the following steps: Step 1031: Obtain the rate of change of the battery's terminal voltage and the rate of change of the charging and discharging current, and calculate the ratio of the rate of change of the terminal voltage to the rate of change of the charging and discharging current to obtain the transient impedance characteristic quantity; Step 1032: Use the transient impedance characteristic quantity, real-time temperature measurement value, and real-time state of charge value as indexes to match and obtain the charge acceptance capacity coefficient in a preset charge acceptance capacity mapping table; Step 1033: Reduce the preset maximum current change rate by the charge acceptance capacity coefficient to obtain the current slew rate limit. The current slew rate limit includes the charging current slew rate limit and the discharging current slew rate limit. The absolute value of the charging current slew rate limit is less than the absolute value of the discharging current slew rate limit.

2. The automatic charging and discharging adjustment method for a photovoltaic battery according to claim 1, characterized in that, In step 104, the rate of change of the bus voltage regulating current reference value is clamped by asymmetric limiting logic, and processed according to the following rules: if the rate of change of the bus voltage regulating current reference value is within the current slew rate limit, the battery current control target value is set to be equal to the bus voltage regulating current reference value; if the rate of change of the bus voltage regulating current reference value exceeds the current slew rate limit, the bus voltage regulating current reference value is truncated according to the boundary value of the current slew rate limit, and the truncated value is set as the battery current control target value.

3. The automatic charging and discharging adjustment method for a photovoltaic battery according to claim 1, characterized in that, The method also includes the following steps: Step 106: Real-time monitoring of the terminal voltage of the DC bus capacitor; Step 107: When the terminal voltage exceeds the preset safety threshold limit, output a power blocking command to the photovoltaic converter and output a power compensation command to the load converter.

4. The automatic charging and discharging adjustment method for a photovoltaic battery according to claim 1, characterized in that, In the preset charge accepting capacity mapping table, the charge accepting capacity coefficient decreases monotonically as the real-time temperature measurement value decreases, and decreases monotonically as the real-time state of charge value increases.

5. The automatic charging and discharging adjustment method for a photovoltaic battery according to claim 1, characterized in that, The target value for battery current control serves as the control input for the bidirectional DC-DC converter. By adjusting the duty cycle of the switching transistors in the bidirectional DC-DC converter, the charging and discharging power of the battery can be regulated.

6. The automatic charging and discharging adjustment method for a photovoltaic battery according to claim 1, characterized in that, The bus voltage regulation current reference value is calculated using a proportional-integral control law. By calculating the sum of the proportional gain term and the integral accumulation term of the voltage deviation, the instantaneous current required to maintain the DC bus power balance is determined.

7. The automatic charging and discharging adjustment method for a photovoltaic battery according to claim 1, characterized in that, The electrical energy corresponding to the current deviation is jointly absorbed through the charging and discharging process of the DC bus capacitor and the power derating process of the photovoltaic converter to compensate for the power gap caused by the current slew rate limit of the battery.

Images