A multi-mode control method and system for a light storage-charging-chip integrated charging pile

Abstract

The application discloses a kind of light storage fills integrated charging pile multi-mode control method and system, it is related to light storage fills integrated charging pile control technical field, to solve the technical problem that the battery life is accelerated attenuation caused by the frequent reverse charge-discharge state of energy storage battery in light storage fills integrated charging pile system, the method comprises: obtaining photovoltaic output power and total load power, according to the photovoltaic output power and total load power in the sliding time window of pre-set length, the instantaneous value of power difference, the average value of power difference in sliding time window, power difference change rate and power difference fluctuation amplitude are determined;According to power difference average value, power difference change rate, power difference fluctuation amplitude and the duration of instantaneous value sign of power difference reversal, determine the current power imbalance state.

Description

Technical Field

[0001] This application relates to the field of integrated photovoltaic, energy storage, charging and diesel charging stack control technology, and in particular to a multi-mode control method and system for integrated photovoltaic, energy storage, charging and diesel charging stack. Background Technology

[0002] In integrated photovoltaic-storage-charging-diesel charging stack systems, the grid-connected photovoltaic-storage coordinated power supply mode is commonly used to maintain DC bus voltage stability and system power balance. The system typically collects photovoltaic output power and total load power at a fixed sampling period and calculates the power difference. When the photovoltaic output power exceeds the total load power, the power difference is used to charge the energy storage; conversely, the insufficient portion is supplemented by energy storage discharge. Mode switching is often determined directly by comparing the instantaneous power difference at the current sampling moment with a preset power direction threshold. Once the sign of the instantaneous power difference changes beyond the threshold, the system issues a command to switch the charging and discharging mode of the energy storage converter.

[0003] This instantaneous power difference-based judgment mechanism can effectively achieve smooth complementary cooperation between photovoltaics and energy storage under stable illumination conditions. However, in actual operating conditions such as cloudy weather in spring and summer, the rapid movement of clouds in the sky can cause repeated and significant fluctuations in surface irradiance within a few seconds to ten seconds. Under such conditions of rapid fluctuation in photovoltaic output power, the instantaneous judgment logic of the system mode controller for power difference and the output of the charging and discharging mode switching command of the energy storage converter face severe challenges. When a large cloud suddenly blocks the photovoltaic array, causing a sharp drop in photovoltaic output power, the system mode controller detects the sign flip of the instantaneous power difference in the next sampling cycle and immediately determines that the system has entered the energy storage discharge support mode, issuing a full-power discharge command to the energy storage converter. However, a few seconds later, the cloud moves away, the photovoltaic output power quickly recovers, the power difference instantly returns to photovoltaic surplus, and the controller immediately issues a command to switch to charging mode.

[0004] Existing conventional methods, in pursuit of rapid response, rely too heavily on instantaneous power judgment for mode switching logic, making it difficult to effectively identify and filter such brief physical fluctuations. This results in the energy storage battery being repeatedly forced to reverse its charging and discharging state within a short period. This not only causes repeated lithium-ion insertion and extraction within the battery, accelerating battery aging and capacity decay, but also causes significant instantaneous drops or overshoots in the DC bus voltage due to the rapid reversal of charging and discharging modes, affecting the power supply quality of the charging terminal. Furthermore, it increases system energy loss due to switching and line losses during mode switching. Therefore, in grid-connected photovoltaic-energy storage co-generation power supply scenarios during cloudy weather, when photovoltaic output power experiences rapid, large fluctuations on a second-level scale while the load remains relatively stable, the system mode controller directly triggers the charging and discharging mode switching of the energy storage converter based solely on the sign change of the instantaneous power difference. This leads to frequent reversals of the energy storage battery's charging and discharging state, resulting in accelerated battery life decay, increased bus voltage fluctuations, and increased system energy loss. These technical problems urgently need to be addressed. Summary of the Invention

[0005] This application provides a multi-mode control method and system for an integrated photovoltaic-storage-charging-diesel charging stack, aiming to solve the technical problem that in an integrated photovoltaic-storage-charging-diesel charging stack system, when the photovoltaic output power fluctuates rapidly and significantly at the second level while the load is relatively stable, the system mode controller directly triggers the charging and discharging mode switching of the energy storage converter based solely on the sign change of the instantaneous power difference, resulting in frequent reversals of the charging and discharging states of the energy storage battery, leading to accelerated battery life degradation, increased bus voltage fluctuations, and increased system energy loss.

[0006] Firstly, to address the aforementioned technical problems, this invention provides a multi-mode control method for an integrated photovoltaic-storage-charging-diesel rechargeable stack, applied to an integrated photovoltaic-storage-charging-diesel rechargeable stack system. The integrated system includes a photovoltaic system and an energy storage converter. The method includes: acquiring the photovoltaic output power and the total load power; determining the instantaneous value of the power difference, the average power difference within the sliding time window, the rate of change of the power difference, and the amplitude of the power difference fluctuation based on the photovoltaic output power and the total load power at multiple consecutive sampling times within a preset sliding time window; the power difference is the difference between the photovoltaic output power and the total load power; and based on the average power difference, the rate of change of the power difference, and the amplitude of the power difference fluctuation. The power imbalance state is determined by the fluctuation amplitude of the power difference and the duration of the instantaneous sign reversal of the power difference. The current power imbalance state includes transient disturbance state, pending transition state, or stable imbalance state. When the current power imbalance state is determined to be transient disturbance state, the current charging and discharging mode command of the energy storage converter remains unchanged. When the current power imbalance state is determined to be pending transition state, the energy storage converter is prohibited from changing the charging and discharging mode direction, and the power command of the energy storage converter is adjusted to zero power according to a preset slope. When the current power imbalance state is determined to be stable imbalance state, the energy storage converter is controlled to perform a smooth switch from the current charging and discharging mode to the opposite charging and discharging mode.

[0007] Secondly, this application provides a multi-mode control system for an integrated photovoltaic-storage-charging-diesel stack, applied to an integrated photovoltaic-storage-charging-diesel stack system. The integrated photovoltaic-storage-charging-diesel stack system includes a photovoltaic system and an energy storage converter. The system includes: an acquisition unit, used to acquire the photovoltaic output power and the total load power; and, based on the photovoltaic output power and the total load power at multiple consecutive sampling times within a preset sliding time window, determining the instantaneous value of the power difference, the average power difference within the sliding time window, the rate of change of the power difference, and the amplitude of the power difference fluctuation; the power difference is the difference between the photovoltaic output power and the total load power; and a determination unit, used to determine the instantaneous value of the power difference, the average power difference within the sliding time window, the rate of change of the power difference, and the amplitude of the power difference fluctuation based on the average power difference, the rate of change of the power difference, and the amplitude of the power difference fluctuation. The fluctuation amplitude of the power difference and the duration of the instantaneous sign reversal of the power difference determine the current power imbalance state; the current power imbalance state includes transient disturbance state, pending transition state, or stable imbalance state; the control unit is used to maintain the current charging and discharging mode command of the energy storage converter unchanged when the current power imbalance state is determined to be a transient disturbance state; when the current power imbalance state is determined to be a pending transition state, the control unit prohibits the energy storage converter from changing the charging and discharging mode direction and adjusts the power command of the energy storage converter to zero power according to a preset slope; when the current power imbalance state is determined to be a stable imbalance state, the control unit controls the energy storage converter to perform a smooth switch from the current charging and discharging mode to the opposite charging and discharging mode.

[0008] This application has at least the following beneficial effects: It discloses a multi-mode control method for an integrated photovoltaic-storage-charging-diesel rechargeable stack. By acquiring the photovoltaic output power and the total load power, and based on power data from multiple consecutive sampling moments within a preset sliding time window, it comprehensively determines the instantaneous value, average value, rate of change, and fluctuation amplitude of the power difference. Based on this, and considering the duration of the sign reversal of the instantaneous power difference value, the power imbalance state is subdivided into transient disturbance state, pending transition state, and stable imbalance state. For different imbalance states, the system adopts differentiated control strategies: in the transient disturbance state, the current charging / discharging mode command of the energy storage converter remains unchanged to avoid over-responding to short-term fluctuations; in the pending transition state, the energy storage converter is prohibited from changing the charging / discharging mode direction, and the power command is smoothly adjusted to zero power to buy time for further judgment; in the stable imbalance state, the energy storage converter is controlled to smoothly switch from the current charging / discharging mode to the opposite charging / discharging mode.

[0009] Through the above technical solution, this application effectively solves the problems in the prior art where judging solely based on instantaneous power difference leads to frequent reversals of charge / discharge states in energy storage batteries, accelerated battery lifespan degradation, increased bus voltage fluctuations, and increased system energy loss. This application, by introducing multi-dimensional power characteristic quantities and graded imbalance state judgment, can accurately identify and filter short-term, large-amplitude fluctuations in photovoltaic output power, preventing energy storage batteries from being repeatedly forced to reverse their charge and discharge states within a short period. This refined control strategy significantly extends the lifespan of energy storage batteries, reduces system energy loss, and effectively suppresses instantaneous drops or overshoots in DC bus voltage, thereby improving the power supply quality of the charging terminal and the operational stability and reliability of the entire photovoltaic-storage-charging-diesel integrated charging stack system. Attached Figure Description

[0010] Figure 1 This is a flowchart illustrating a multi-mode control method for an integrated photovoltaic-storage-charging-diesel stack provided in this application. Figure 2 This is a flowchart illustrating another multi-mode control method for an integrated photovoltaic-storage-charging-diesel stack provided in this application; Figure 3 This is a schematic diagram of the structure of a multi-mode control system for an integrated photovoltaic, energy storage, and diesel charging stack provided in this application. Detailed Implementation

[0011] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0012] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0013] In integrated photovoltaic-storage-charging-diesel charging stack systems, the traditional grid-connected photovoltaic-storage coordinated power supply mode typically relies on the direct judgment of instantaneous power differences to maintain DC bus voltage stability and system power balance. This mechanism performs well under stable illumination conditions, but in actual operating conditions such as cloudy weather with rapid fluctuations in photovoltaic output power, the system mode controller directly triggers the charging and discharging mode switching of the energy storage converter based solely on the sign change of the instantaneous power difference. This leads to frequent reversals of the charging and discharging states of the energy storage batteries, resulting in accelerated battery life degradation, increased bus voltage fluctuations, and increased system energy losses.

[0014] In view of the above problems, this application provides a multi-mode control method for an integrated photovoltaic-storage-charging-diesel charging stack. By introducing multi-dimensional power difference analysis within a sliding time window and combining it with the duration of the sign reversal of the instantaneous power difference value, this application can more accurately identify the true state of power imbalance in the system, thereby avoiding frequent switching of charging and discharging modes of the energy storage converter under transient disturbances, effectively extending battery life, improving bus voltage stability, and reducing system energy loss.

[0015] The multi-mode control method for the integrated photovoltaic-storage-charging-diesel stack provided in this application will be described in detail and explained through the following specific embodiments.

[0016] Reference Figure 1 This application provides a multi-mode control method for an integrated photovoltaic-storage-charging-diesel stack, which may include the following steps: S101. Obtain the photovoltaic output power and the total load power. Based on the photovoltaic output power and the total load power at multiple consecutive sampling times within a preset sliding time window, determine the instantaneous value of the power difference, the average value of the power difference within the sliding time window, the rate of change of the power difference, and the fluctuation amplitude of the power difference.

[0017] The power difference is the difference between the photovoltaic output power and the total load power.

[0018] S102. Determine the current power imbalance state based on the average power difference, the rate of change of the power difference, the fluctuation amplitude of the power difference, and the duration of the sign reversal of the instantaneous power difference.

[0019] The current power imbalance state includes transient disturbance state, unconfirmed transition state, or stable imbalance state.

[0020] S103. When the current power imbalance state is determined to be a transient disturbance state, the current charging and discharging mode command of the energy storage converter remains unchanged; when the current power imbalance state is determined to be a transitional state to be confirmed, the energy storage converter is prohibited from changing the charging and discharging mode direction, and the power command of the energy storage converter is adjusted to zero power according to a preset slope; when the current power imbalance state is determined to be a stable imbalance state, the energy storage converter is controlled to perform a smooth switch from the current charging and discharging mode to the charging and discharging mode in the opposite direction.

[0021] To better understand the technical solution proposed in this application, some key terms are explained first. A photovoltaic-storage-charging-diesel integrated charging pile system refers to a comprehensive energy system that integrates photovoltaic power generation, energy storage systems, charging piles, and diesel generator sets, aiming to provide a stable, reliable, and economical power supply for electric vehicle charging. Photovoltaic output power refers to the electrical power generated by the photovoltaic array at the current moment. Total load power refers to the total electrical power consumed by all charging terminals and auxiliary equipment in the charging pile system. Power difference refers to the difference between photovoltaic output power and total load power; its positive or negative sign indicates power surplus or deficiency. The energy storage converter is a key device connecting the energy storage battery and the DC bus, responsible for controlling the charging and discharging process of the energy storage battery to achieve bidirectional energy flow. A sliding time window refers to a preset time period during which data from multiple sampling moments are continuously collected for dynamic analysis. Power imbalance state is the current system power balance status determined by the system based on multi-dimensional power difference analysis results, including transient disturbance state, unconfirmed transition state, and stable imbalance state. Accurate identification of these states is the foundation for intelligent control in this application.

[0022] The core of the method proposed in this application lies in the accurate identification and intelligent response to system power imbalance. Specifically, the method first requires obtaining the photovoltaic output power and the total load power. This can be achieved by installing voltage and current sensors at the output and input terminals of the photovoltaic DC-DC converter. The sensors synchronously collect instantaneous voltage and current at a preset sampling period, and after filtering, perform power calculations to obtain the photovoltaic output power and the total load power. For example, a Hall effect sensor or shunt can be used to measure the current, and a voltage transformer or resistive voltage divider can be used to measure the voltage. The collected analog signals are converted into digital signals by an analog-to-digital converter (ADC), and then filtered and calculated by a microcontroller or digital signal processor (DSP).

[0023] After obtaining the photovoltaic output power and total load power, it is necessary to determine the instantaneous power difference, the average power difference within the sliding time window, the rate of change of the power difference, and the fluctuation amplitude of the power difference based on data from multiple consecutive sampling moments within a preset sliding time window. The instantaneous power difference can be obtained by subtracting the total load power from the photovoltaic output power at the current sampling moment. For example, if the current photovoltaic output power is 100kW and the total load power is 80kW, then the instantaneous power difference is 20kW. The average power difference within the sliding time window can be obtained by taking the arithmetic mean of multiple historical instantaneous power difference values ​​stored within the sliding time window. For example, in a sliding window containing 10 sampling points, the instantaneous power difference values ​​of these 10 sampling points are added together and then divided by 10. The rate of change of the power difference can be calculated by dividing the difference between the instantaneous power difference value at the current sampling moment and the instantaneous power difference value at the previous sampling moment by the sampling period. For example, if the power difference at the current moment is 20kW and the previous moment was 15kW, and the sampling period is 1 second, then the rate of change is 5kW / s. The power difference fluctuation amplitude can be defined as the difference between the instantaneous maximum power difference and the instantaneous minimum power difference within the sliding time window. For example, within the sliding window, if the maximum power difference is 30kW and the minimum power difference is -10kW, then the fluctuation amplitude is 40kW.

[0024] After determining the aforementioned multi-dimensional power difference parameters, the system will determine the current power imbalance state based on these parameters and the duration of the sign reversal of the instantaneous power difference value. The duration of the sign reversal of the instantaneous power difference value refers to the length of time it takes for the power difference to change from positive to negative or from negative to positive and remain so. For example, if the power difference changes from a positive value to a negative value and remains negative for the next 5 sampling periods, the sign reversal duration is 5 sampling periods.

[0025] Based on the determined current power imbalance state, the system will adopt different control strategies. When the current power imbalance state is determined to be a transient disturbance, the system will maintain the current charging and discharging mode command of the energy storage converter unchanged. This means that even if the instantaneous value of the power difference fluctuates, as long as it is determined to be a transient disturbance, the energy storage converter will not change its operating mode, thereby avoiding unnecessary mode switching. For example, if the energy storage converter is currently in charging mode, even if the photovoltaic output power briefly decreases, causing the power difference to become negative, the energy storage converter will still maintain charging mode if it is determined to be a transient disturbance.

[0026] When the current power imbalance is determined to be a transitional state awaiting confirmation, the system will prohibit the energy storage converter from changing its charging / discharging mode direction and adjust the power command of the energy storage converter to zero power at a preset slope. This means that when the system is in an uncertain state, the energy storage converter will gradually stop its current charging / discharging behavior, but will not immediately reverse the mode, providing a buffer period for the system to further confirm the nature of the power imbalance. For example, if the energy storage converter is currently in discharging mode, when it enters the transitional state awaiting confirmation, its discharge power command will gradually decrease at a preset slope until it reaches zero power, but will not immediately switch to charging mode.

[0027] When the current power imbalance is determined to be a stable imbalance, the system will control the energy storage converter to smoothly switch from the current charging / discharging mode to the opposite charging / discharging mode. This means that the system has confirmed that the power imbalance is continuous and stable, requiring the energy storage converter to change its operating mode to rebalance the system power. For example, if the system transitions from a photovoltaic surplus state to a stable imbalance state with insufficient power, the energy storage converter will smoothly switch from charging mode to discharging mode to compensate for the power deficit.

[0028] In summary, this application significantly improves the operational stability, battery life, and power quality of the integrated photovoltaic-storage-charging-diesel stack system under complex operating conditions by introducing multi-dimensional power difference analysis and a refined power imbalance state determination mechanism, combined with an intelligent energy storage converter control strategy. This innovative control method effectively solves the technical problems of frequent reverse charging and discharging states of energy storage batteries, aggravated bus voltage fluctuations, and increased system energy losses in existing technologies, demonstrating significant progress and practical value.

[0029] For details, please refer to Figure 2 The determination of the instantaneous value of the power difference, the average value of the power difference within the sliding time window, the rate of change of the power difference, and the fluctuation amplitude of the power difference based on the photovoltaic output power and the total load power at multiple consecutive sampling moments within a preset sliding time window can be achieved in the following manner.

[0030] S201. By using voltage and current sensors installed at the output and load input terminals of the photovoltaic DC converter, instantaneous voltage and instantaneous current are synchronously collected at a preset sampling period. After filtering and power calculation, the photovoltaic output power and total load power are obtained.

[0031] S202. Subtract the total load power from the photovoltaic output power at the current sampling moment to obtain the instantaneous value of the power difference.

[0032] S203. Calculate the arithmetic mean of the multiple instantaneous values ​​of historical power difference stored within the sliding time window to obtain the average power difference.

[0033] S204. Divide the difference between the instantaneous power difference value at the current sampling time and the instantaneous power difference value at the previous sampling time by the sampling period to obtain the rate of change of power difference.

[0034] S205. The difference between the instantaneous value of the maximum power difference and the instantaneous value of the minimum power difference within the sliding time window shall be taken as the power difference fluctuation amplitude.

[0035] Specifically, to accurately obtain the photovoltaic output power and total load power, voltage and current sensors can be installed at both the output and input terminals of the photovoltaic DC-DC converter. These sensors are configured to synchronously acquire instantaneous voltage and current data at a preset sampling period. The acquired raw data is filtered to eliminate noise and transient interference, and then power calculations are performed to obtain accurate photovoltaic output power and total load power. The preset sampling period is typically set based on the system's dynamic response requirements and sensor performance to ensure the real-time nature and accuracy of data acquisition.

[0036] After obtaining the photovoltaic output power and the total load power, the instantaneous power difference at the current sampling moment can be directly calculated by subtracting the total load power from the photovoltaic output power at the current sampling moment. This instantaneous value reflects the power surplus or deficit of the system at a specific moment.

[0037] To smooth out instantaneous fluctuations and reflect power trends over a period of time, an average power difference is introduced. This average is calculated by averaging multiple historical instantaneous power difference values ​​stored within a preset sliding time window. The length of the sliding time window can be adjusted according to system characteristics and response speed requirements; a longer window helps suppress high-frequency noise but may sacrifice response speed.

[0038] The rate of change of power difference is used to characterize the dynamic evolution trend of power imbalance. It is calculated by dividing the difference between the instantaneous power difference at the current sampling moment and the instantaneous power difference at the previous sampling moment by the sampling period. This rate indicates whether the power imbalance is worsening, slowing down, or stabilizing.

[0039] Furthermore, the power difference fluctuation amplitude is used to measure the severity of power imbalance. This fluctuation amplitude is determined by calculating the difference between the instantaneous maximum and minimum power difference values ​​within a sliding time window. A larger fluctuation amplitude usually indicates significant uncertainty in the system power or that it has been subjected to severe disturbances.

[0040] The above technical solution enables refined perception and quantification of power imbalance in an integrated photovoltaic-storage-charging-diesel stack system. By introducing voltage and current sensors for synchronous acquisition and filtering, the accuracy and reliability of the raw power data are ensured. Furthermore, by calculating the instantaneous value, average value, rate of change, and fluctuation amplitude of the power difference, this application can comprehensively characterize the static features, dynamic trends, and disturbance intensity of the power imbalance. This multi-dimensional power imbalance characteristic quantification method significantly improves the system's ability to identify various power fluctuations, providing more accurate input for subsequent energy storage converter control strategies, thereby enhancing the stability and response speed of the entire system.

[0041] In some embodiments described above in this application, although the current power imbalance state is determined based on the average power difference, the rate of change of the power difference, the amplitude of the power difference fluctuation, and the duration of the sign reversal of the instantaneous power difference value, in practice, without clear judgment criteria and refined threshold settings, the system may have difficulty accurately distinguishing between transient disturbances, persistent imbalances, or transitional states that are about to stabilize. This may cause the energy storage converter to overreact to short-term power fluctuations or fail to respond promptly to persistent imbalances, thereby affecting the stability and operating efficiency of the system.

[0042] In this regard, this application further proposes the following steps for determining the current power imbalance state based on the average power difference, the rate of change of the power difference, the amplitude of the power difference fluctuation, and the duration of the sign reversal of the instantaneous power difference value: If the average power difference is less than the preset power balance dead zone threshold, it is determined to be in a power balance state. If the average power difference is greater than or equal to the preset power balance dead zone threshold, and the sign of the instantaneous power difference value flips, the current power imbalance state is determined based on the duration of the sign flip, the rate of change of the power difference, and the amplitude of the power difference fluctuation. When the duration of the symbol flip is less than a preset first time threshold, and the rate of change of the power difference is greater than a preset drastic change rate threshold and the amplitude of the power difference fluctuation is greater than a preset drastic fluctuation amplitude threshold, it is determined to be the transient disturbance state; the drastic change rate threshold and the drastic fluctuation amplitude threshold together constitute the preset drastic fluctuation threshold. When the duration of the symbol flipping reaches the first time threshold but not the preset second time threshold, or when the duration of the symbol flipping reaches the second time threshold but the rate of change of the power difference is still greater than the preset convergence threshold, it is determined to be the transition state to be confirmed. When the duration of the symbol flipping reaches the second time threshold and the rate of change of the power difference is less than or equal to the preset convergence threshold, it is determined to be the stable imbalance state; the second time threshold is greater than the first time threshold.

[0043] Specifically, the power balance dead zone threshold refers to a pre-defined, small range that allows for the existence of power differences. When the average power difference falls within this range, the system can be considered to be in a state of basic power balance, requiring no mode switching. Its purpose is to avoid unnecessary responses to minor fluctuations, thereby improving the overall stability of the system. The first and second time thresholds are two key time points used to measure the duration of the instantaneous sign reversal of the power difference. The first time threshold aims to distinguish between transient disturbances and longer-term imbalances, while the second time threshold distinguishes between a transitional state awaiting confirmation and a stable imbalance state. These time thresholds are set to provide the system with sufficient observation time to avoid overreacting to short-lived, non-persistent power fluctuations. The drastic change rate threshold and the drastic fluctuation amplitude threshold together constitute the preset drastic fluctuation threshold, used to quantify the dynamic characteristics of the power difference. When both the rate of change and the fluctuation amplitude of the power difference exceed these thresholds, it indicates that the system is experiencing a severe transient disturbance. The convergence threshold is used to determine whether the rate of change of the power difference has stabilized. When the rate of change of power imbalance is less than or equal to the convergence threshold, it indicates that the power imbalance is stabilizing or has already stabilized. In practical applications, these thresholds can be pre-set and optimized based on the specific scale, response characteristics, load type, and system stability requirements of the integrated photovoltaic-storage-charging-diesel stack system, through simulation analysis, historical data statistics, or expert experience. For example, for systems with high response speed requirements, the first and second time thresholds can be set relatively short; for photovoltaic power generation with large fluctuations, the threshold for severe fluctuations can be appropriately relaxed.

[0044] Through the above technical solution, this application enables accurate identification and classification of power imbalance states in integrated photovoltaic-storage-charging-diesel stack systems. Compared to methods that rely on only a few parameters for rough judgment, the power balance dead zone threshold, multi-level time threshold, and drastic fluctuation and convergence thresholds introduced in this application allow the system to effectively distinguish between transient disturbances, unconfirmed transition states, and stable imbalance states. This avoids overreaction to short-term, non-sustained power fluctuations, reduces unnecessary operation and energy loss of the energy storage converter, and extends equipment life. Simultaneously, for persistent power imbalances, this solution can promptly and accurately identify and trigger corresponding control strategies, ensuring stable system operation under various operating conditions and improving system reliability and economy.

[0045] In some preferred embodiments, it is assumed that during operation of the integrated photovoltaic-storage-charging-diesel stack system, the photovoltaic output power and total load power are collected by sensors. The system first calculates the instantaneous value, average value, rate of change, and fluctuation amplitude of the power difference. Specifically, if the calculated average power difference is within a preset power balance dead zone threshold of -5kW to 5kW, the system will determine that it is currently in a power balance state, and the energy storage converter will maintain its current mode. If the average power difference exceeds this dead zone, and the sign of the instantaneous power difference flips, the system will conduct further analysis. For example, at a certain moment, the photovoltaic output suddenly drops sharply, causing the power difference to change from positive to negative. If the duration of the sign flip is less than 0.5 seconds (a preset first time threshold), and the rate of change of the power difference is greater than 10kW / s (a preset drastic change rate threshold), while the fluctuation amplitude of the power difference is greater than 20kW (a preset drastic fluctuation amplitude threshold), the system determines it to be a transient disturbance state. In this case, the energy storage converter will maintain its current charging and discharging mode command to avoid overreacting to brief disturbances. If the duration of the sign flip reaches 0.5 seconds but less than 2 seconds (a preset second time threshold), or if the duration reaches 2 seconds but the power difference change rate is still greater than 2 kW / s (a preset convergence threshold), the system determines it to be in a transitional state awaiting confirmation. At this time, the energy storage converter will be prohibited from changing its charging / discharging mode direction and its power command will be adjusted to zero power according to a preset slope, preparing for possible subsequent mode switching. Finally, if the duration of the sign flip reaches 2 seconds and the power difference change rate is less than or equal to 2 kW / s, it indicates that the power imbalance has stabilized, and the system will determine it to be in a stable imbalance state. At this time, the energy storage converter will be triggered to perform a smooth switch from the current charging / discharging mode to the opposite charging / discharging mode to effectively cope with persistent power imbalance.

[0046] In some embodiments described above in this application, when the system is in a transitional state awaiting confirmation, the power command of the energy storage converter is adjusted to zero power at a preset slope, and it is prohibited from changing the direction of the charging and discharging mode. However, in practical applications, simply adjusting the power according to the preset slope may not fully consider the current charging and discharging mode of the energy storage converter and the dynamic changes in the power difference, which may result in an insufficiently smooth power adjustment process, or even cause unnecessary system oscillations or instability in some cases.

[0047] In response, this application further proposes that when the current power imbalance state is determined to be the transition state to be confirmed, the energy storage converter should be prohibited from changing the charging and discharging mode direction, and the power command of the energy storage converter should be adjusted to zero power according to a preset slope, specifically including: If the energy storage converter is currently in charging mode, a restricted power adjustment slope is calculated based on the power difference change rate, and the charging power command is controlled to decrease to zero along the restricted power adjustment slope. During the decrease, the energy storage converter is prohibited from crossing the zero power point to enter the discharge mode. If the energy storage converter is currently in discharge mode, the control discharge power command decreases to zero at a limited slope and prohibits entering charging mode.

[0048] Specifically, when the energy storage converter is in charging mode, its charging power command adjustment does not simply use a fixed preset slope, but rather dynamically calculates a constrained power adjustment slope based on the real-time monitored rate of change of the power difference. This constrained power adjustment slope aims to ensure that the charging power command can smoothly and orderly decrease to zero, avoiding system shocks caused by excessively fast or slow power adjustment. During this decrease, the energy storage converter is strictly prohibited from crossing the zero power point to enter discharge mode, to prevent unnecessary mode reversals before the power imbalance is clearly defined. The rate of change of the power difference can be understood as the instantaneous rate of change of the difference between the photovoltaic output power and the total load power; its magnitude and direction reflect the dynamic trend of system power imbalance. The calculation of the constrained power adjustment slope can be based on a linear or nonlinear mapping of this rate of change to achieve adaptive power adjustment.

[0049] Similarly, when the energy storage converter is in discharge mode, its discharge power command also decreases to zero according to a limited slope. This limited slope can also be dynamically adjusted according to the rate of change of power difference to ensure a smooth exit of the discharge power. During this process, the energy storage converter is also prohibited from entering charging mode, thereby maintaining its current mode direction until the power imbalance is further confirmed.

[0050] Through the above technical solution, this application ensures a smoother and more controllable power adjustment process for the energy storage converter when the integrated photovoltaic-storage-charging-diesel stack system is in a pending transition state. This dynamic slope adjustment based on the current charging / discharging mode and the rate of change of power difference avoids the incompatibility that may arise from a fixed slope, effectively reducing transient impacts during power adjustment. Furthermore, explicitly prohibiting changes in the charging / discharging mode direction during the process of adjusting the power command to zero significantly enhances the system's stability under uncertain conditions, preventing system oscillations caused by misjudgment or premature mode switching, thereby improving the operational reliability and safety of the entire stack system.

[0051] In some preferred embodiments, it is assumed that during operation of the integrated photovoltaic-storage-charging-diesel stack system, rapid changes in photovoltaic output power or total load power cause the system to enter a pending transition state. At this time, if the energy storage converter is currently charging at 50kW, and the system detects a power deficit rate of -10kW / s (indicating a rapidly decreasing power deficit), the control system calculates a restricted power adjustment slope based on this rate of change, for example, set to -5kW / s. The charging power command of the energy storage converter will gradually decrease from 50kW to 0kW at a slope of -5kW / s. During this decrease, even if the power command approaches zero, the system strictly prohibits the energy storage converter from switching from charging mode to discharging mode. Similarly, if the energy storage converter is currently discharging at 30kW and the power deficit rate is 5kW / s (indicating a rapidly increasing power deficit), the system will calculate a limiting slope, for example, set to -3kW / s, and control the discharge power command to decrease from 30kW to 0kW at this slope, while prohibiting it from entering charging mode during this process. This fine-grained control ensures that the energy storage converter can safely and smoothly exit its current power output when the power imbalance is unclear, preparing for subsequent handling of stable imbalance states.

[0052] In some embodiments described above in this application, when the system is in a pending transition state, the power command of the energy storage converter is adjusted to zero power, and it is prohibited from changing the direction of charging and discharging modes, in order to wait for further clarification of the system state. However, in practical applications, if the system power imbalance deteriorates sharply during this waiting period, causing the DC bus voltage to drop rapidly, relying solely on a preset fixed waiting time may not be sufficient to respond in time, potentially delaying necessary mode switching or even jeopardizing the stable operation of the system.

[0053] In this regard, this application further proposes that after the aforementioned pending confirmation transition state and the power command of the energy storage converter has been adjusted to zero power, the method further includes: After the energy storage converter is in the pending transition state and the power command of the energy storage converter has been adjusted to zero power, the DC bus voltage is collected in real time and the bus voltage drop rate is calculated. When the bus voltage drop rate exceeds a preset critical drop rate threshold, a time threshold reduction coefficient is calculated based on the proportion by which the drop rate exceeds the critical drop rate threshold, and the second time threshold is shortened using the time threshold reduction coefficient to obtain a dynamic second time threshold; if the waiting time counted since entering the pending confirmation transition state reaches the dynamic second time threshold, the early exit from the pending confirmation transition state is triggered, and the state is switched to the stable imbalance state. When the DC bus voltage drops below the preset voltage safety warning threshold, the remaining waiting time is immediately cleared and the early exit is triggered, transitioning to the stable imbalance state; the remaining waiting time is the difference between the dynamic second time threshold and the waiting time.

[0054] Specifically, real-time acquisition of DC bus voltage refers to continuously acquiring the instantaneous value of the bus voltage at a preset sampling frequency using voltage sensors installed on the DC bus. Calculating the bus voltage sag rate can be understood as performing differential or slope calculations on the continuously acquired bus voltage values ​​to reflect how quickly the bus voltage changes over time. Its purpose is to monitor the health of the DC side of the system in real time, providing a basis for subsequent decision-making. The preset critical sag rate threshold is an empirical value or a safety boundary set according to system design requirements, used to determine whether the bus voltage sag has reached a level requiring attention. When the actually calculated bus voltage sag rate exceeds this threshold, it indicates that the system power imbalance may be worsening. The time threshold reduction factor is calculated based on the proportion of the sag rate exceeding the critical threshold, meaning that the faster and more severe the sag, the larger the reduction factor, thus shortening the dynamic second time threshold more. The introduction of the dynamic second time threshold aims to enable the system to flexibly adjust the waiting time in the pending confirmation transition state according to the actual voltage sag situation, avoiding unnecessary long waiting times. If the waiting time reaches this dynamic threshold, the system exits the pending confirmation transition state early and enters the stable imbalance state. This allows the energy storage converter to promptly perform mode switching and respond to system power demands. In practical applications, the preset voltage safety warning threshold is the lowest DC bus voltage the system can withstand. Below this value, system instability or even collapse may occur. When the DC bus voltage drops below this warning threshold, it indicates the system is on the verge of a very dangerous situation, requiring immediate emergency measures. Directly resetting the remaining waiting time to zero and immediately triggering early exit into the stable imbalance state aims to minimize response time, ensuring the energy storage converter can intervene as quickly as possible to stabilize the bus voltage and prevent further system deterioration. The remaining waiting time can be understood as how long the system needs to wait before triggering mode switching under the dynamic second time threshold.

[0055] Through the above technical solution, this application significantly improves the response speed and safety of the integrated photovoltaic-storage-charging-diesel rechargeable stack system during the power imbalance transition period. Compared with the traditional method that relies solely on a fixed time threshold, this application can sense the dynamic changes of the DC bus voltage in real time. Especially when the power imbalance deteriorates rapidly, it can dynamically adjust the waiting time according to the voltage drop rate, and even immediately trigger mode switching when the voltage drops below the safety warning threshold. This effectively avoids the risk of system instability or even collapse that may be caused by prolonged waiting, ensuring that the energy storage converter can intervene more promptly and accurately to maintain the stability of the DC bus voltage. Therefore, the solution of this application improves the robustness and adaptability of the system to sudden power imbalance events while ensuring system stability, thereby enhancing the operational reliability and safety of the entire rechargeable stack system.

[0056] In some preferred embodiments, it is assumed that during the operation of the integrated photovoltaic-storage-charging-diesel stack system, a sudden and significant drop in photovoltaic output power or a sharp increase in total load power causes the system to enter a pending confirmation transition state. At this time, the power command of the energy storage converter has been adjusted to zero power, and the system begins to wait. If, during this period, the DC bus voltage begins to drop rapidly, the system will collect the bus voltage in real time and calculate its drop rate. For example, if the preset critical drop rate threshold is 1V / ms, and the system detects a drop rate of 2V / ms, a time threshold reduction factor will be calculated based on the excess ratio (2 times), for example, 0.5. If the original second time threshold is 10 seconds, the dynamic second time threshold will be shortened to 5 seconds. If the waiting time has reached 5 seconds, the system will immediately trigger an early exit from the pending confirmation transition state and transition to a stable imbalance state, thereby enabling the energy storage converter to quickly start the reverse charging and discharging mode and stabilize the bus voltage. Furthermore, if the power imbalance becomes more severe, causing the DC bus voltage to drop rapidly and continuously, even falling below the preset voltage safety warning threshold (e.g., 700V), regardless of the current waiting time, the system will immediately reset the remaining waiting time to zero and forcibly trigger an early exit from the pending confirmation transition state, transitioning to a stable imbalance state. For example, even if the dynamic second time threshold is set to 5 seconds, if the bus voltage drops to 690V after waiting for 2 seconds, the system will immediately perform a mode switch to respond to the emergency as quickly as possible, preventing system failure due to low voltage. In this way, the system can make flexible and safe decisions based on the actual voltage conditions, ensuring stable system operation.

[0057] In some of the embodiments described above in this application, when the current power imbalance state is determined to be a stable imbalance state, although the energy storage converter is controlled to switch from the current charging and discharging mode to the opposite charging and discharging mode, if the switching process fails to fully consider the dynamic characteristics of power electronic devices, the zero-crossing characteristics of inductor current and the electrochemical response of energy storage battery, transient current surges and severe fluctuations in DC bus voltage may occur during the switching process, and may even affect system stability and equipment life.

[0058] In this regard, this application further proposes that the steps for controlling the energy storage converter to perform a smooth switching from the current charging / discharging mode to the opposite charging / discharging mode include: When the current power imbalance state is determined to be the stable imbalance state, the current power command of the energy storage converter is reduced to zero with a preset soft shutdown slope. After detecting that the inductor current of the energy storage converter has crossed to zero, a preset dead zone waiting time is inserted, and zero power output is maintained within the preset dead zone waiting time. After the preset dead zone waiting time ends, the current direction flag is changed, and the power command opposite to the current charging and discharging mode is gradually increased with a preset soft start slope until the output power corresponding to the power command in the opposite direction compensates for the power deficit between the photovoltaic output power and the total load power. During the increase of the power command in the opposite direction, the change of DC bus voltage is monitored in real time. If the bus voltage drop rate exceeds the preset drop rate threshold, the soft start slope is increased.

[0059] Specifically, when the system detects that the current power imbalance is a stable imbalance, the energy storage converter needs to switch from the current charging / discharging mode to the opposite mode. For example, if it is currently in charging mode and the system has a power deficit, it needs to switch to discharging mode. To ensure the smoothness of the switching process, the current power command of the energy storage converter is gradually reduced to zero according to a preset soft-shutdown slope. This soft-shutdown slope is designed to limit the rate of power reduction and avoid transient shocks caused by sudden power drops.

[0060] After the power command is reduced to zero, it is necessary to check whether the inductor current inside the energy storage converter has crossed zero. Zero-crossing of the inductor current is crucial for ensuring the safe shutdown of power semiconductor devices and avoiding reverse recovery issues. After detecting zero-crossing of the inductor current, the system inserts a preset dead-time. During this dead-time, the energy storage converter maintains zero power output. This is to provide sufficient shutdown time for the power semiconductor devices and allow a certain degree of relaxation of the electrochemical polarization state inside the energy storage battery, preparing for subsequent reverse charging and discharging.

[0061] In practical applications, after the preset dead-zone waiting time expires, the system changes the current direction flag, instructing the energy storage converter to prepare to enter the opposite charging and discharging mode. Subsequently, the energy storage converter gradually increases the power command in the opposite direction to the current charging and discharging mode at a preset soft-start slope. The soft-start slope is set to avoid large current surges caused by sudden increases in power command, thereby protecting the stability of power electronic devices and the DC bus. The increase in power command continues until the corresponding output power can compensate for the power deficit between the photovoltaic output power and the total load power, allowing the system to reach a new power balance.

[0062] Furthermore, during the increase of the power command in the opposite direction, the system monitors the changes in the DC bus voltage in real time. If the detected rate of voltage drop exceeds a preset rate of drop threshold, this usually indicates a significant power deficit or load surge in the system, requiring the energy storage converter to respond more quickly. In this case, the system dynamically increases the soft-start slope to accelerate the increase of the power command, thereby providing the required compensation power more quickly, effectively suppressing further voltage drops in the bus, and ensuring system voltage stability.

[0063] Through the above technical solution, this application enables smooth and safe switching of the energy storage converter's charging and discharging modes, significantly reducing transient current surges and DC bus voltage fluctuations that may occur during the switching process. This solution effectively protects power electronic devices and extends equipment lifespan through refined soft-shutdown, dead-zone waiting, and soft-start control. Furthermore, the ability to dynamically adjust the soft-start slope allows the system to respond flexibly and quickly to power deficits based on actual bus voltage drops, further enhancing the system's stability and robustness under complex operating conditions and improving the overall operational reliability of the integrated photovoltaic-storage-charging-diesel stack system.

[0064] In some preferred embodiments, suppose that at a certain moment, the photovoltaic output power of the integrated photovoltaic-storage-charging-diesel charging stack system suddenly drops sharply due to cloud cover, while the charging pile load demand remains at a high level, resulting in a continuous power deficit in the system, which is determined to be a stable imbalance state. At this time, the energy storage converter may be in charging mode and needs to quickly switch to discharging mode to make up for the power deficit.

[0065] Specifically, the control system first instructs the energy storage converter to smoothly reduce its current charging power command from a positive value to zero, based on a preset soft-shutdown slope. For example, if the current charging power is 50kW and the soft-shutdown slope is 10kW / s, the power command will linearly decrease to zero within 5 seconds. After the power command reaches zero, the system continuously monitors the inductor current inside the energy storage converter. Once the inductor current is detected to have crossed zero (i.e., the current has completely disappeared), the system initiates a preset dead-time, such as 50 milliseconds. During these 50 milliseconds, the energy storage converter maintains zero power output, ensuring that the power semiconductor devices are completely turned off and allowing the electrochemical reactions inside the energy storage battery to reach a relatively stable state.

[0066] After the dead-zone waiting period ends, the control system changes the current direction flag, switching the energy storage converter from charging mode to a ready state for discharging mode. Subsequently, the system gradually increases the discharge power command at a preset soft-start slope, such as 20kW / s. For example, in discharge mode, the power command starts from zero and increases at a rate of 20kW / s. During this process, the system monitors the DC bus voltage in real time. If the bus voltage sag rate exceeds a preset critical sag rate threshold, such as 5V / ms, indicating a significant power deficit and a risk of rapid voltage drop, the system immediately increases the soft-start slope, for example, to 30kW / s, to accelerate the discharge power and quickly stabilize the bus voltage. This process continues until the discharge power of the energy storage converter effectively compensates for the power deficit between the photovoltaic output power and the total load power, allowing the system to regain power balance. Through this phased, dynamically adjusted, and smooth switching mechanism, the system avoids severe electrical shocks during mode switching, ensuring the stable and efficient operation of the charging pile system.

[0067] Specifically, the setting methods for the preset dead zone waiting time, preset soft shutdown slope, and preset soft start slope are as follows.

[0068] The preset dead zone waiting time is a preset time based on the duration of the turn-off tail current of the power semiconductor devices inside the energy storage converter and the electrochemical polarization relaxation time required when the energy storage battery reverses its charge / discharge state. The preset soft turn-off slope and the preset soft start slope are preset based on the maximum allowable current change rate of the energy storage converter, the voltage ripple tolerance of the DC bus capacitor, and the system's requirements for the transient fluctuation range of the bus voltage.

[0069] The preset dead-zone waiting time can be understood as a period of zero-power output time set during the switching of charging and discharging modes of the energy storage converter to ensure system stability and the safety of power semiconductor devices. Specifically, its setting needs to comprehensively consider the duration of the turn-off tail current of the power semiconductor devices inside the energy storage converter, to avoid transient shocks or malfunctions caused by incomplete device turn-off near the current zero-crossing point; simultaneously, it also needs to consider the electrochemical polarization relaxation time required when the energy storage battery reverses its charging / discharging state, allowing sufficient time for the internal electrochemical reactions of the battery to adjust and stabilize, avoiding adverse effects on battery life and performance caused by rapid reverse charging and discharging. Its purpose is to ensure the smoothness of mode switching and protect the power semiconductor devices and energy storage battery.

[0070] In practical applications, the preset soft-shutdown slope and preset soft-start slope refer to the rate limit of power change during the power command adjustment process of the energy storage converter. Specifically, the preset soft-shutdown slope is used to control the rate at which the power command smoothly decreases from its current value to zero, while the preset soft-start slope is used to control the rate at which the power command gradually increases from zero to the target value. The setting of these slopes needs to be considered based on the maximum allowable current change rate of the energy storage converter to prevent excessive stress on the power semiconductor devices caused by rapid current changes. Simultaneously, the voltage ripple withstand capability of the DC bus capacitor must be considered to ensure that the DC bus voltage fluctuation is within an acceptable range during power changes. Furthermore, the system's requirements for the transient fluctuation range of the bus voltage are also important considerations to maintain the voltage stability of the entire system. The aim is to achieve a smooth power transition by limiting the rate of power change, avoiding impact on the system.

[0071] Through the above technical solution, this application ensures that the energy storage converter achieves a smooth power transition during charging and discharging mode switching. More importantly, by finely setting key parameters, it effectively avoids the risks of power semiconductor device damage and energy storage battery performance degradation that may occur during traditional switching processes. Compared to simple soft shutdown and soft start, this application fully considers the turn-off tail current of power semiconductor devices and the electrochemical polarization relaxation time of energy storage batteries, making the dead zone waiting time more precise. This ensures system response speed while maximizing the protection of core components. In addition, the setting of the soft shutdown and soft start slope comprehensively considers the maximum current change rate of the energy storage converter, the voltage ripple tolerance of the DC bus capacitor, and the system's requirements for the transient fluctuation range of the bus voltage. This makes the power adjustment process more in line with the actual operating needs of the system, significantly improving the stability and reliability of system operation and extending the service life of the equipment.

[0072] In some embodiments described above, a smooth switching of the energy storage converter from the current charging / discharging mode to the opposite charging / discharging mode is proposed. However, during implementation, if the power difference fluctuates frequently near the switching point after the mode switch, the energy storage converter may repeatedly switch charging / discharging modes, causing system oscillations and affecting system stability and equipment lifespan. Furthermore, if the bus voltage becomes abnormal after the mode switch, timely intervention is required to ensure system safety. Therefore, this application further proposes an anti-jitter mechanism and safety protection measures to improve system stability and safety after the energy storage converter smoothly switches from the current charging / discharging mode to the opposite charging / discharging mode.

[0073] After controlling the energy storage converter to perform a smooth switch from the current charge / discharge mode to the opposite charge / discharge mode, the method further includes: Start the anti-shake timer and dynamically widen the power difference determination threshold used to determine the sign flip of the power difference from the initial determination threshold to the preset hysteresis threshold to form an asymmetric hysteresis comparison interval; During the operation of the anti-shake timer, if the instantaneous value of the power difference retracts and crosses the initial judgment threshold in the reverse direction but does not exceed the preset hysteresis threshold, or if the anti-shake timer has not expired, then the reverse charging and discharging mode switching will not be triggered again. If the bus voltage exceeds the safe range after a smooth switch, hardware-level protection will be triggered, consuming surplus energy or limiting load power.

[0074] Specifically, activating the anti-jitter timer means that immediately after the energy storage converter completes a smooth switch between charging and discharging modes, a timer is started. This timer is used to suppress requests for mode switching for a period of time. Simultaneously, the power difference judgment threshold, used to determine the sign reversal of the power difference, has an initial value of a small amount to accurately determine the power balance state. After a mode switch, this judgment threshold is dynamically widened to a preset hysteresis threshold, thus forming an asymmetric hysteresis comparison range. The purpose of this hysteresis comparison range is to prevent a new mode switching command from being immediately triggered when the instantaneous power difference value fluctuates slightly near the switching point, thereby avoiding frequent system oscillations.

[0075] Specifically, during the operation of the anti-shake timer, if the instantaneous power difference value regresses and crosses the initial judgment threshold in the reverse direction, but has not yet exceeded the preset hysteresis threshold, or if the anti-shake timer has not yet reached its preset timeout period, the system will refuse to trigger the reverse charge / discharge mode switch again. This means that even if the instantaneous power difference value briefly returns to its pre-switch state, as long as its fluctuation range is within the hysteresis interval and the anti-shake time has not expired, the system will maintain the current charge / discharge mode to enhance stability.

[0076] Furthermore, if the system detects in real time that the DC bus voltage exceeds the preset safety range after a smooth switch, such as being too high or too low, it will immediately trigger hardware-level protection. This protection action is designed to respond quickly to abnormal situations, such as by consuming surplus energy (e.g., through a bleed resistor) or limiting load power (e.g., reducing the output power of the charging pile) to restore the bus voltage to the safe range, thereby ensuring the safe operation of the entire photovoltaic-storage-charging-diesel integrated charging stack system.

[0077] Through the above technical solution, this application effectively avoids repeated system switching and oscillations caused by frequent fluctuations in power difference near the switching point after a smooth switching of the energy storage converter's charging and discharging modes, significantly improving the system's operational stability and equipment lifespan. Simultaneously, by introducing real-time monitoring of the bus voltage and a hardware-level protection mechanism, this application can promptly detect and handle voltage anomalies in the system, effectively preventing potential safety risks and ensuring the safe and reliable operation of the integrated photovoltaic-storage-charging-diesel stack system under various operating conditions, thereby improving the robustness and reliability of the entire system.

[0078] In some preferred embodiments, it is assumed that the integrated photovoltaic-storage-charging-diesel stack system smoothly switches from energy storage charging mode to discharging mode at a certain moment. After the switch is completed, the system immediately starts an anti-jitter timer, for example, set to 5 seconds. Simultaneously, the initial threshold for determining the sign reversal of the power difference is dynamically widened, for example, from ±1kW to a hysteresis threshold of ±5kW. During this 5-second anti-jitter timer operation, if the instantaneous power difference between the photovoltaic output power and the total load power fluctuates between -5kW and +5kW, even if it briefly retracts and reverses past the initial ±1kW threshold, the system will not trigger a reverse switch between charging and discharging modes again. Only when the power difference continuously exceeds +5kW (e.g., photovoltaic power is much greater than load power, requiring charging) or continuously falls below -5kW (e.g., load power is much greater than photovoltaic power, requiring discharging), and the anti-jitter timer expires, will the system consider switching modes again.

[0079] Meanwhile, the system continuously monitors the DC bus voltage. If, after switching is complete, the bus voltage suddenly drops below the preset voltage safety warning threshold, for example, from 750V to 650V, the system will immediately trigger hardware-level protection actions. For example, a bleeder resistor can be activated to dissipate excess energy on the bus, or the maximum output power of the fast-charging terminal connected to the DC bus can be limited to prevent the bus voltage from dropping further, thereby protecting the system equipment from damage.

[0080] Traditional multi-mode control methods for integrated photovoltaic-storage-charging-diesel rechargeable stacks primarily rely on the photovoltaic and energy storage systems to manage power balance. However, in actual operation, the energy storage batteries may become unable to continue providing charging and discharging power due to excessively low state of charge or excessively high temperature, and may even need to shut down, leading to an inability to maintain a stable power balance and affecting the normal operation of the rechargeable stack. If these problems are not addressed, the integrated photovoltaic-storage-charging-diesel rechargeable stack system will face the risk of power outages or inability to meet load demands when the energy storage system is constrained. To address this, this application proposes a control strategy that introduces a diesel generator set to take over the system's power supply and power balance when the energy storage system is constrained, ensuring stable system operation under extreme conditions.

[0081] In some embodiments of this application, the integrated photovoltaic-storage-charging-diesel stack system further includes a diesel generator set; when the current power imbalance state is determined to be the stable imbalance state, and the state of charge of the energy storage battery is lower than a preset lower limit or the temperature of the energy storage battery is higher than a preset safety threshold, the above method further includes: Start the diesel generator set and limit the maximum output power of the DC fast charging terminal during the preheating period of the diesel generator set; Once the diesel generator set reaches its rated state, the diesel engine rectifier is controlled to connect to the DC bus and take over the bus voltage via droop control. At the same time, the energy storage converter is controlled to reduce the discharge power at a preset slope, so that the energy storage battery exits the discharge state. When the photovoltaic output power continuously exceeds the total load power and the energy storage battery reaches its upper limit of state of charge, the charging power of the DC fast charging terminal is increased and the maximum power of the photovoltaic DC converter is reduced.

[0082] Specifically, the "diesel generator set" refers to an independent power generation device, typically driven by a diesel engine to generate electricity. Its purpose is to provide backup power to the system when the main power source (such as photovoltaics or energy storage) is limited or fails. The "preset lower limit" and "preset safety threshold" are parameters preset based on the chemical characteristics, lifespan requirements, and safe operation specifications of the energy storage battery, used to determine whether the energy storage battery is in a limited state. For example, the preset lower limit could be the minimum allowable value for the energy storage battery's state of charge, and the preset safety threshold could be the maximum allowable temperature of the energy storage battery. When the system detects that the energy storage battery's state of charge is below the preset lower limit or the energy storage battery temperature is above the preset safety threshold, it indicates that the energy storage system can no longer effectively participate in power balancing, and the diesel generator set needs to be started. The "preheating period" refers to the time required for the diesel generator set to reach a stable operating state from startup. During this period, its output power may be unstable or not reach the rated value. To avoid causing additional disturbances or overloads to the system during the diesel generator set's preheating period, it is necessary to "limit the maximum output power of the DC fast charging terminal" to ensure the system's stability during the transition phase.

[0083] Once the diesel generator set has preheated and reached its rated state, its output power is stable and reliable. At this point, "the diesel engine rectifier is controlled to connect to the DC bus via droop control and take over the bus voltage," meaning the diesel generator set will become the main source of DC bus voltage, coordinating with other power sources through droop control. Simultaneously, "the energy storage converter is controlled to reduce its discharge power at a preset slope, causing the energy storage battery to exit the discharge state," aiming to protect the energy storage battery from further deep discharge or overheating under limited conditions, thereby extending battery life and ensuring safety. After the diesel generator set takes over the system, if "the photovoltaic output power continuously exceeds the total load power and the energy storage battery's state of charge reaches its upper limit," it indicates that the system has excess energy and the energy storage battery is fully charged. At this point, "increasing the charging power of the DC fast charging terminal" can fully utilize the excess photovoltaic energy to provide fast charging services for loads such as electric vehicles, improving the system's economic efficiency. Simultaneously, "reducing the maximum power of the photovoltaic DC converter" can prevent system overload or excessively high DC bus voltage, ensuring safe and stable system operation.

[0084] Through the above technical solution, this application effectively solves the problems of power imbalance and power outage that may occur in integrated photovoltaic-storage-charging-diesel charging stack systems when the energy storage battery cannot function normally due to excessively low state of charge or excessively high temperature. This solution significantly improves the system's operational reliability and adaptability to extreme operating conditions by introducing a diesel generator set as a reliable backup power source and designing sophisticated start-up, grid connection, and power coordination control strategies. Especially in emergency situations where the energy storage system is constrained, it can ensure the charging stack's continuous power supply capability, avoiding system downtime or service interruptions caused by energy storage battery limitations, thereby guaranteeing user experience and operational efficiency. Furthermore, this solution also considers the optimized energy utilization after the diesel generator set is connected to the grid, further improving the overall economy and flexibility of the system.

[0085] In some embodiments, reference is made to Figure 3This application proposes a multi-mode control system for an integrated photovoltaic-storage-charging-diesel rechargeable stack, applied to an integrated photovoltaic-storage-charging-diesel rechargeable stack system. The integrated photovoltaic-storage-charging-diesel rechargeable stack system includes a photovoltaic system and an energy storage converter. The system includes: an acquisition unit 301, used to acquire the photovoltaic output power and the total load power; and, based on the photovoltaic output power and total load power at multiple consecutive sampling times within a preset sliding time window, determining the instantaneous value of the power difference, the average power difference within the sliding time window, the rate of change of the power difference, and the amplitude of the power difference fluctuation; the power difference is the difference between the photovoltaic output power and the total load power; and a determination unit 302, used to determine the instantaneous value of the power difference, the average power difference within the sliding time window, the rate of change of the power difference, and the amplitude of the power difference fluctuation based on the average power difference, the rate of change of the power difference, and the amplitude of the power difference fluctuation. The current power imbalance state is determined by measuring the fluctuation amplitude and the duration of the instantaneous sign reversal of the power difference. The current power imbalance state includes a transient disturbance state, a transitional state awaiting confirmation, or a stable imbalance state. The control unit 303 is used to maintain the current charging and discharging mode command of the energy storage converter unchanged when the current power imbalance state is determined to be a transient disturbance state; when the current power imbalance state is determined to be a transitional state awaiting confirmation, the control unit 303 prohibits the energy storage converter from changing the charging and discharging mode direction and adjusts the power command of the energy storage converter to zero power according to a preset slope; when the current power imbalance state is determined to be a stable imbalance state, the control unit 303 controls the energy storage converter to perform a smooth switch from the current charging and discharging mode to the opposite charging and discharging mode.

[0086] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A multi-mode control method for an integrated photovoltaic-storage-charging-diesel stack, characterized in that, The method, applied to an integrated photovoltaic-storage-diesel charging stack system, wherein the integrated photovoltaic-storage-diesel charging stack system includes photovoltaics and an energy storage converter, comprises: The photovoltaic output power and the total load power are obtained. Based on the photovoltaic output power and the total load power at multiple consecutive sampling times within a preset sliding time window, the instantaneous value of the power difference, the average value of the power difference within the sliding time window, the rate of change of the power difference, and the fluctuation amplitude of the power difference are determined. The power difference is the difference between the photovoltaic output power and the total load power. The current power imbalance state is determined based on the average power difference, the rate of change of the power difference, the fluctuation amplitude of the power difference, and the duration of the sign reversal of the instantaneous power difference value; the current power imbalance state includes a transient disturbance state, a transitional state to be confirmed, or a stable imbalance state. When the current power imbalance state is determined to be the transient disturbance state, the current charging and discharging mode command of the energy storage converter remains unchanged; when the current power imbalance state is determined to be the pending transition state, the energy storage converter is prohibited from changing the charging and discharging mode direction, and the power command of the energy storage converter is adjusted to zero power according to a preset slope; when the current power imbalance state is determined to be the stable imbalance state, the energy storage converter is controlled to perform a smooth switch from the current charging and discharging mode to the opposite charging and discharging mode.

2. The method according to claim 1, characterized in that, The step of determining the instantaneous value of the power difference, the average value of the power difference within the sliding time window, the rate of change of the power difference, and the amplitude of the power difference fluctuation based on the photovoltaic output power and the total load power at multiple consecutive sampling times within a preset sliding time window includes: By installing voltage and current sensors at the output and load input terminals of the photovoltaic DC converter, instantaneous voltage and instantaneous current are synchronously collected at a preset sampling period. After filtering and power calculation, the photovoltaic output power and the total load power are obtained. The instantaneous value of the power difference is obtained by subtracting the total load power from the photovoltaic output power at the current sampling moment. The average power difference is obtained by taking the arithmetic mean of the multiple instantaneous historical power difference values ​​stored within the sliding time window. The power difference rate is obtained by dividing the difference between the instantaneous power difference at the current sampling time and the instantaneous power difference at the previous sampling time by the preset sampling period. The difference between the instantaneous value of the maximum power difference and the instantaneous value of the minimum power difference within the sliding time window is taken as the power difference fluctuation amplitude.

3. The method according to claim 1, characterized in that, The step of determining the current power imbalance state based on the average power difference, the rate of change of the power difference, the fluctuation amplitude of the power difference, and the duration of the instantaneous sign reversal of the power difference includes: If the average power difference is less than the preset power balance dead zone threshold, it is determined to be a power balance state; If the average power difference is greater than or equal to the preset power balance dead zone threshold, and the sign of the instantaneous power difference value flips, the current power imbalance state is determined based on the duration of the sign flip, the rate of change of the power difference, and the amplitude of the power difference fluctuation. When the duration of the symbol flip is less than a preset first time threshold, and the rate of change of the power difference is greater than a preset drastic change rate threshold and the amplitude of the power difference fluctuation is greater than a preset drastic fluctuation amplitude threshold, it is determined to be the transient disturbance state; the drastic change rate threshold and the drastic fluctuation amplitude threshold together constitute the preset drastic fluctuation threshold. When the duration of the symbol flipping reaches the first time threshold but not the preset second time threshold, or when the duration of the symbol flipping reaches the second time threshold but the rate of change of the power difference is still greater than the preset convergence threshold, it is determined to be the transition state to be confirmed. When the duration of the symbol flipping reaches the second time threshold and the rate of change of the power difference is less than or equal to the preset convergence threshold, it is determined to be the stable imbalance state; the second time threshold is greater than the first time threshold.

4. The method according to claim 1, characterized in that, When the current power imbalance state is determined to be the transitional state to be confirmed, the energy storage converter is prohibited from changing the charging and discharging mode direction, and the power command of the energy storage converter is adjusted to zero power according to a preset slope, including: If the energy storage converter is currently in charging mode, a restricted power adjustment slope is calculated based on the power difference change rate, and the charging power command is controlled to decrease to zero along the restricted power adjustment slope. During the decrease, the energy storage converter is prohibited from crossing the zero power point to enter the discharge mode. If the energy storage converter is currently in discharge mode, the control discharge power command decreases to zero at a limited slope and prohibits entering charging mode.

5. The method according to claim 1 or 4, characterized in that, When the current power imbalance state is determined to be the transitional state to be confirmed, the method further includes: After the energy storage converter is in the pending transition state and the power command of the energy storage converter has been adjusted to zero power, the DC bus voltage is collected in real time and the bus voltage drop rate is calculated. When the bus voltage drop rate exceeds a preset critical drop rate threshold, a time threshold reduction coefficient is calculated based on the proportion by which the bus voltage drop rate exceeds the critical drop rate threshold, and the second time threshold is shortened using the time threshold reduction coefficient to obtain a dynamic second time threshold; if the waiting time counted since entering the pending confirmation transition state reaches the dynamic second time threshold, the early exit from the pending confirmation transition state is triggered, and the state is switched to the stable imbalance state. When the DC bus voltage drops below the preset voltage safety warning threshold, the remaining waiting time is immediately cleared and the early exit is triggered, transitioning to the stable imbalance state; the remaining waiting time is the difference between the dynamic second time threshold and the waiting time.

6. The method according to claim 1, characterized in that, When the current power imbalance state is determined to be the stable imbalance state, the energy storage converter is controlled to perform a smooth switch from the current charging / discharging mode to the opposite charging / discharging mode, including: When the current power imbalance state is determined to be the stable imbalance state, the current power command of the energy storage converter is reduced to zero with a preset soft shutdown slope. After detecting that the inductor current of the energy storage converter has crossed to zero, a preset dead zone waiting time is inserted, and zero power output is maintained within the preset dead zone waiting time. After the preset dead zone waiting time ends, the current direction flag is changed, and the power command opposite to the current charging and discharging mode is gradually increased with a preset soft start slope until the output power corresponding to the power command in the opposite direction compensates for the power deficit between the photovoltaic output power and the total load power. During the increase of the power command in the opposite direction, the change of DC bus voltage is monitored in real time. If the bus voltage drop rate exceeds the preset drop rate threshold, the preset soft-start slope is increased.

7. The method according to claim 6, characterized in that, The preset dead zone waiting time is a preset time based on the duration of the turn-off tail current of the power semiconductor device inside the energy storage converter and the electrochemical polarization relaxation time requirement of the energy storage battery when the charging and discharging states reverse. The preset soft-shutdown slope and the preset soft-start slope are respectively preset based on the maximum allowable current change rate of the energy storage converter, the voltage ripple tolerance capability of the DC bus capacitor, and the system's requirements for the transient fluctuation range of the bus voltage.

8. The method according to claim 1, characterized in that, After controlling the energy storage converter to perform a smooth switch from the current charge / discharge mode to the opposite charge / discharge mode, the method further includes: Start the anti-shake timer and dynamically widen the power difference determination threshold used to determine the sign flip of the power difference from the initial determination threshold to the preset hysteresis threshold to form an asymmetric hysteresis comparison interval; During the operation of the anti-shake timer, if the instantaneous value of the power difference retracts and crosses the initial judgment threshold in the reverse direction but does not exceed the preset hysteresis threshold, or if the anti-shake timer has not yet expired, then the reverse charging and discharging mode switching will not be triggered again. If the bus voltage exceeds the safe range after a smooth switch, hardware-level protection will be triggered, consuming surplus energy or limiting load power.

9. The method according to claim 1, characterized in that, The integrated photovoltaic-storage-charging-diesel stack system also includes a diesel generator set; when the current power imbalance state is determined to be the stable imbalance state, and the state of charge of the energy storage battery is lower than a preset lower limit or the temperature of the energy storage battery is higher than a preset safety threshold, the method further includes: Start the diesel generator set and limit the maximum output power of the DC fast charging terminal during the preheating period of the diesel generator set; Once the diesel generator set reaches its rated state, the diesel engine rectifier is controlled to connect to the DC bus and take over the bus voltage via droop control. At the same time, the energy storage converter is controlled to reduce the discharge power at a preset slope, so that the energy storage battery exits the discharge state. When the photovoltaic output power continuously exceeds the total load power and the energy storage battery reaches its upper limit of state of charge, the charging power of the DC fast charging terminal is increased and the maximum power of the photovoltaic DC converter is reduced.

10. A multi-mode control system for an integrated photovoltaic-storage-charging-diesel stack, characterized in that, Applied to an integrated photovoltaic-storage-charging-diesel stack system, the integrated photovoltaic-storage-charging-diesel stack system includes photovoltaics and energy storage converters, including: The acquisition unit is used to acquire the photovoltaic output power and the total load power, and to determine the instantaneous value of the power difference, the average value of the power difference within the sliding time window, the rate of change of the power difference, and the fluctuation amplitude of the power difference based on the photovoltaic output power and the total load power at multiple consecutive sampling times within a preset sliding time window; the power difference is the difference between the photovoltaic output power and the total load power. The determining unit is configured to determine the current power imbalance state based on the average power difference, the rate of change of the power difference, the fluctuation amplitude of the power difference, and the duration of the instantaneous sign reversal of the power difference; the current power imbalance state includes a transient disturbance state, a transitional state to be confirmed, or a stable imbalance state. The control unit is configured to maintain the current charging / discharging mode command of the energy storage converter unchanged when the current power imbalance state is determined to be the transient disturbance state; when the current power imbalance state is determined to be the pending transition state, prohibit the energy storage converter from changing the charging / discharging mode direction and adjust the power command of the energy storage converter to zero power according to a preset slope; and when the current power imbalance state is determined to be the stable imbalance state, control the energy storage converter to perform a smooth switch from the current charging / discharging mode to the opposite charging / discharging mode.

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