DC microgrid system and power supply adaptive droop control method

Abstract

This application discloses a DC microgrid system and a power supply adaptive droop control method, applied in the field of DC microgrid technology, to solve the problems of poor operating condition adaptability and poor control timeliness in existing DC microgrid systems. Specifically, the energy management unit acquires current operating data and current environmental data; based on the current operating data, current environmental data, historical operating data, and historical environmental data, it performs grid state prediction to obtain current trend prediction data; the distributed power generation unit collects the current bus voltage of the DC bus, determines the current operating condition based on the current bus voltage, current operating data, and current trend prediction data; determines the current droop control coefficient based on the current operating condition; adjusts the current output power based on the current droop control coefficient; the droop control coefficient is adaptively adjusted according to the operating condition, resulting in high operating condition adaptability, and the adjustment is completed in advance based on the trend prediction data, resulting in high control timeliness.

Description

Technical Field

[0001] This application relates to the field of DC microgrid technology, and in particular to a DC microgrid system and a power supply adaptive droop control method. Background Technology

[0002] DC microgrids are small power supply systems that connect distributed power sources, energy storage devices, and DC loads through a DC bus. They are characterized by flexible power supply, fewer power conversion links, and high operational reliability, and are widely used in distributed small load scenarios such as zero-carbon parks, gatehouse camps, and maintenance stations.

[0003] Currently, DC microgrid systems typically employ a master-slave control architecture to achieve parallel operation of multiple distributed power sources. This architecture relies on a central controller to uniformly schedule each distributed power source and transmits control commands and status data via communication links. Under this architecture, rapid attenuation of sunlight or concentrated load startup can easily cause a sudden drop in bus voltage and power oscillations, resulting in poor control timeliness. Existing DC microgrid systems also widely adopt droop control strategies, adjusting the output power of each distributed power source unit through a preset droop control coefficient. However, the random connection of distributed power sources and frequent fluctuations in load power lead to complex and variable system operating conditions. Under the aforementioned control strategies, increased circulating current is prone to occur under light loads, while severe bus voltage drops are likely to occur under heavy loads, resulting in poor adaptability to operating conditions. Summary of the Invention

[0004] This application provides a DC microgrid system and a power supply adaptive droop control method to solve the problems of poor operating condition adaptability and poor control timeliness in existing DC microgrid systems.

[0005] The technical solutions provided in this application are as follows: On one hand, embodiments of this application provide a DC microgrid system, including: a DC bus, DC load units, energy storage units, an energy management unit, and multiple distributed power supply units; the energy management unit is connected to the DC load units, energy storage units, and multiple distributed power supply units respectively; the DC load units, energy storage units, and multiple distributed power supply units are respectively connected to the DC bus; The energy management unit is used to acquire current operating data and current environmental data; based on the current operating data, current environmental data, historical operating data, and historical environmental data, it performs grid state prediction to obtain current trend prediction data; and sends the current operating data and current trend prediction data to each distributed power generation unit and energy storage unit. The current operating data includes current load data, current energy storage data, and current power generation data; the current trend prediction data includes predicted bus voltage changes, predicted load power changes, and predicted state of charge changes. The distributed power supply unit is used to collect the current bus voltage of the DC bus and receive current operating data and current trend prediction data from the energy management unit; determine the current operating condition based on the current bus voltage, current operating data and current trend prediction data; determine the current droop control coefficient based on the current operating condition; and adjust the current output power based on the current droop control coefficient.

[0006] Optionally, the distributed power unit is specifically used for: Preliminary operating conditions are determined based on the current bus voltage and the predicted bus voltage change. The preliminary operating conditions are revised based on the current load data and the predicted load power change to obtain the revised operating conditions. The operating conditions are adjusted and corrected based on current energy storage data and predicted changes in state of charge to obtain the current operating conditions.

[0007] Optionally, the distributed power unit is specifically used for: The predicted bus voltage is determined based on the current bus voltage and the predicted change in bus voltage. The predicted bus voltage is compared with the bus voltage ranges of multiple preset operating conditions; among them, adjacent operating condition ranges form hysteresis sub-ranges at the boundary. When the predicted bus voltage is not in the hysteresis sub-interval, the operating condition corresponding to the operating condition interval where the predicted bus voltage is located is determined as the preliminary operating condition; when the predicted bus voltage is in the hysteresis sub-interval, the previous operating condition is determined as the preliminary operating condition.

[0008] Optionally, the distributed power unit is specifically used for: Determine the predicted load rate based on current load data and predicted load power changes; When the predicted load is higher than the load limit corresponding to the initial operating condition, the initial operating condition is revised to the operating condition corresponding to the higher load. When the predicted load is lower than the lower limit of the load corresponding to the initial operating condition, the initial operating condition is revised to the operating condition corresponding to the lower load. When the load is predicted to be within the load range corresponding to the preliminary operating condition, the preliminary operating condition is used as the corrected operating condition.

[0009] Optionally, the distributed power unit is specifically used for: The predicted energy storage capacity is determined based on current energy storage data and predicted changes in state of charge. When the predicted energy storage capacity is lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition will be adjusted to the high power direction to obtain the current operating condition; When it is predicted that the energy storage capacity will not be lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition will be used as the current operating condition.

[0010] Optionally, the distributed power unit is specifically used for: Obtain the system voltage deviation, the rated current of the distributed power supply unit, and the current adjustment factor corresponding to the current operating condition; The reference droop slope is determined based on the ratio of the system voltage deviation to the rated current of the distributed power supply unit. Multiply the baseline droop slope by the current adjustment factor to obtain the droop control coefficient.

[0011] Optionally, the energy storage unit is used for: The system collects the current bus voltage of the DC bus and receives current operating data and current trend prediction data from the energy management unit; based on the current bus voltage, current operating data, and current trend prediction data, it determines the current operating condition according to the same operating condition identification logic as the distributed power unit; and adjusts the current charging and discharging power based on the current operating condition and current energy storage data.

[0012] Optionally, the energy storage unit is specifically used for: When the current operating condition is light load voltage regulation or balanced operation, and the current energy storage data is lower than the preset charging limit, the energy storage unit is controlled to charge. When the current operating condition is a heavy load condition, the energy storage unit is controlled to discharge or stop charging and discharging based on the comparison result between the current energy storage data and the preset energy threshold. When the current operating condition is the low-power protection condition, the control energy storage unit stops discharging.

[0013] Optionally, the DC load unit includes: multiple loads of different levels and multiple load switches; Each load is connected to the DC bus via a corresponding load switch; the control terminal of each load switch is connected to the energy management unit. The energy management unit is also used to control the on / off state of each load switch according to the load level based on the current bus voltage and / or current energy storage data.

[0014] On the other hand, embodiments of this application provide a power supply adaptive droop control method, applied to the distributed power supply unit in the aforementioned DC microgrid system, the method comprising: The system collects the current bus voltage of the DC bus and receives current operating data and current trend prediction data from the energy management unit; wherein, the current operating data includes current load data, current energy storage data, and current power generation data; the current trend prediction data includes predicted changes in bus voltage, predicted changes in load power, and predicted changes in state of charge; The current operating conditions are determined based on the current bus voltage, current operating data, and current trend forecast data. Determine the current droop control coefficient based on the current operating conditions; Adjust the current output power based on the current droop control coefficient.

[0015] The beneficial effects of the embodiments of this application are as follows: In the DC microgrid system provided in this application, the current droop control coefficient is determined based on the current operating condition, which reflects the real-time operating status of the system. The current droop control coefficient adaptively adjusts with changes in the system's operating status, adapting to the current actual operating conditions of the system, resulting in high adaptability. Simultaneously, the energy management unit predicts the grid state based on current operating data, current environmental data, historical operating data, and historical environmental data. The resulting current trend prediction data includes predicted changes in bus voltage, predicted changes in load power, and predicted changes in state of charge, reflecting the expected changes in bus voltage, load power, and energy storage capacity, respectively. The current operating condition is determined based on the current bus voltage, current operating data, and current trend prediction data. That is, based on the real-time operating status of the system and combined with the expected changes in the system's operating status, the current operating condition is determined before a significant shift in the bus voltage occurs. The current output power, adjusted based on the current droop control coefficient, is adjusted accordingly in advance, improving control timeliness.

[0016] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the first system framework of the DC microgrid system in the embodiments of this application; Figure 2 This is a schematic diagram of a second system framework for a DC microgrid system in an embodiment of this application; Figure 3 This is a schematic flowchart illustrating the power supply adaptive droop control method in the embodiments of this application. Figure 4 This is a schematic diagram illustrating the specific process of determining the current operating condition in the embodiments of this application; Figure 5 This is a schematic diagram illustrating the specific process of determining the current droop control coefficient in this embodiment of the application.

[0018] In the diagram: 100 - DC microgrid system; 110 - DC bus; 120 - DC load unit; 121 - load; 122 - load switch; 130 - energy storage unit; 140 - energy management unit; 150 - distributed power unit. Detailed Implementation

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

[0020] This application provides a DC microgrid system, see below. Figure 1 As shown, the DC microgrid system 100 includes at least: a DC bus 110, DC load units 120, energy storage units 130, energy management units 140, and multiple distributed power supply units 150; the energy management unit 140 is connected to the DC load units 120, the energy storage units 130, and the multiple distributed power supply units 150 respectively; the DC load units 120, the energy storage units 130, and the multiple distributed power supply units 150 are connected to the DC bus 110 respectively. The energy management unit 140 is used to acquire current operating data and current environmental data; based on the current operating data, current environmental data, historical operating data, and historical environmental data, it performs grid state prediction to obtain current trend prediction data; and sends the current operating data and current trend prediction data to each distributed power generation unit 150 and energy storage unit 130; wherein, the current operating data includes current load data, current energy storage data, and current power generation data; and the current trend prediction data includes predicted bus voltage changes, predicted load power changes, and predicted state of charge changes; The distributed power supply unit 150 is used to collect the current bus voltage of the DC bus 110 and receive the current operating data and current trend prediction data from the energy management unit 140; determine the current operating condition based on the current bus voltage, current operating data and current trend prediction data; determine the current droop control coefficient based on the current operating condition; and adjust the current output power based on the current droop control coefficient.

[0021] In practical applications, the DC bus 110 serves as the common channel for power transmission and energy distribution in the system. DC load units 120, energy storage units 130, and multiple distributed power supply units 150 are connected to the DC bus 110, forming the system's power backbone network. The energy management unit 140 is connected to the DC load units 120, energy storage units 130, and each distributed power supply unit 150, forming the system's information interaction network. The DC bus 110 is used to collect and distribute electrical energy. The DC load unit 120 refers to the collection of electrical devices connected to the DC bus 110, used to consume the electrical energy output by the system. The energy storage unit 130 refers to the energy storage device connected to the DC bus 110, used to smooth power fluctuations and release or absorb electrical energy when energy supply and demand are unbalanced. The distributed power supply unit 150 refers to a power supply device with local power generation or conversion capabilities connected to the DC bus 110, used to provide electrical energy to the system. Energy management unit 140 refers to a management device equipped with a data acquisition and communication interface, used to collect global system status information, perform grid status prediction and distribute it to each distributed power unit 150 and energy storage unit 130.

[0022] Current operating data refers to data characterizing the current operating status of the DC microgrid system, including current load data, current energy storage data, and current power generation data. Specifically, current load data characterizes the current load level of the system, specifically the real-time load rate; current energy storage data characterizes the current energy level of energy storage unit 130, specifically the battery state of charge of energy storage unit 130; and current power generation data characterizes the current power generation capacity of each distributed power source unit 150, specifically the real-time power generation of each distributed power source unit 150. Current environmental data characterizes the external environmental conditions of the system, specifically including photovoltaic irradiance information and ambient temperature information. Historical operating data refers to the time-series dataset of current operating data sampled at various historical sampling times, and historical environmental data refers to the time-series dataset of current environmental data sampled at various historical sampling times. Specifically, the energy management unit 140 collects the current bus current of the DC bus 110 in real time through a current sampling circuit set on the bus, and collects the current bus voltage of the DC bus 110 in real time through a voltage sampling circuit set on the bus. The current bus current and the current bus voltage are multiplied to obtain the current total load power of the system. The current total load power is then divided by the rated load capacity of the system to obtain the real-time load rate of the system, which is used as the current load data. The energy management unit 140 periodically reads the state of charge information reported by the battery management system in the energy storage unit 130 through the communication link, which is used as the current energy storage data. The energy management unit 140 periodically reads the real-time power generation reported by each distributed power unit 150 through the communication link, and summarizes it as the current power generation data. The energy management unit 140 collects photovoltaic irradiance information and ambient temperature information through locally configured irradiance sensors and temperature sensors, which is used as the current environmental data.

[0023] Current trend forecast data refers to data characterizing the expected changes in the system's operating status within a preset forecast period, including predicted changes in bus voltage, predicted changes in load power, and predicted changes in state of charge. Specifically, predicted changes in bus voltage refer to the expected changes in bus voltage within the preset forecast period, predicted changes in load power refer to the expected changes in system load power within the preset forecast period, and predicted changes in state of charge refer to the expected changes in the state of charge of energy storage unit 130 within the preset forecast period. The determination of current trend forecast data is divided into two levels: the first level is the determination of basic changes, where energy management unit 140 determines predicted changes in load power based on historical operating data and predicted changes in power generation based on current and historical environmental data; the second level is the determination of voltage and power changes, where energy management unit 140 determines predicted changes in bus voltage based on predicted changes in power generation and predicted changes in load power, and determines predicted changes in state of charge based on current load data, current power generation data, predicted changes in power generation, and predicted changes in load power. The predicted change in power generation represents the expected change in power generation of each distributed power unit 150 within a preset prediction period; in this embodiment, it specifically refers to the predicted change in photovoltaic output. In practice, at the arrival of each prediction cycle, the energy management unit 140 retrieves the load power records from the most recent preset number of operating days that are in the same time period as the current moment from historical operating data, and calculates the predicted change in load power according to the following formula: ΔP L =(1 / N)·Σ[P i (t0+T) P i (t0)] Among them, P i (t0) represents the load power at the corresponding time on the i-th operating day, P i (t0+T) represents the load power after a preset prediction duration T on the i-th operating day, N is the number of operating days retrieved, and ΔP L To predict changes in load power.

[0024] The predicted change in photovoltaic (PV) output characterizes the expected change in PV power generation within a preset prediction period. PV power generation is approximately proportional to PV irradiance; therefore, the predicted change in PV output can be indirectly obtained by predicting irradiance changes. The energy management unit 140 takes PV irradiance samples from the most recent sampling periods and performs linear fitting. The slope of the fitted line is used as the current rate of irradiance change. The preset prediction period is then extrapolated based on this current rate of change, and the expected PV irradiance at the end of the preset prediction period is calculated using the following formula: G T =G0 + r·T Where G0 is the current photovoltaic irradiance, r is the current rate of change of irradiance, T is the preset prediction duration, and G T This is the projected photovoltaic irradiance at the end of the preset forecast period.

[0025] The energy management unit 140 converts the expected photovoltaic irradiance into expected photovoltaic power generation based on the ratio between the current power generation and the current photovoltaic irradiance, and uses the difference between the expected power generation and the current power generation as the predicted change in photovoltaic output, calculated according to the following formula: ΔP PV =P0·(G T / G0) P0 Where P0 is the current power generation, G0 is the current photovoltaic irradiance, and G T ΔP is the projected photovoltaic irradiance at the end of the preset forecast period. PV To predict changes in photovoltaic power output.

[0026] The deviation of the bus voltage is determined by the system power deficit. The predicted change in power deficit is the difference between the change in source-side output and the change in load-side demand within a preset prediction period. The energy management unit 140 subtracts the predicted change in photovoltaic output from the predicted change in load power to obtain the predicted change in power deficit. A positive predicted change in power deficit indicates that the growth in photovoltaic output exceeds the growth in load power, and the system energy tends to be surplus; a negative predicted change in power deficit indicates that the system energy tends to be insufficient. Under droop control, the deviation of the bus voltage from the reference voltage has a linear mapping relationship with the power deficit. The energy management unit 140 multiplies the predicted change in power deficit by the voltage-power mapping coefficient to obtain the predicted change in bus voltage. The voltage-power mapping coefficient represents the bus voltage deviation caused by a unit power deficit, and its value is determined by the system droop external characteristics, specifically the ratio of the system's allowable voltage deviation to the system's rated power.

[0027] The throughput power of energy storage unit 130 originates from the system power deficit. When the power deficit is positive, energy storage unit 130 charges; when the power deficit is negative, energy storage unit 130 discharges. Therefore, the expected throughput of energy storage unit 130 within the preset forecast period is determined by both the current power deficit and the predicted change in power deficit. Energy management unit 140 calculates the current power deficit by subtracting the current generation data from the current total load power, and assumes that the power deficit changes linearly with the predicted change in power deficit within the preset forecast period. The average power deficit within the preset forecast period is the sum of the current power deficit and half of the predicted change in power deficit. The expected throughput is calculated using the following formula: E = (ΔP0 + ΔP / 2)·T Where ΔP0 is the current power deficit, ΔP is the predicted change in power deficit, T is the preset prediction duration, and E is the expected throughput.

[0028] The energy management unit 140 divides the expected throughput by the rated capacity of the energy storage unit 130 to obtain the expected change in state of charge within a preset prediction period, which is used as the predicted change in state of charge. The energy management unit 140 uses the predicted change in bus voltage, the predicted change in load power, and the predicted change in state of charge as current trend prediction data, and sends them together with the current operating data to each distributed power unit 150 and the energy storage unit 130.

[0029] Each distributed power unit 150 is configured to perform local voltage sensing and power regulation. Specifically, each distributed power unit 150 is equipped with an independent local controller. This local controller acquires the real-time voltage value of the DC bus 110 at high frequency through a voltage sampling circuit, and analyzes the current operating data and current trend prediction data from the energy management unit 140. Based on this, the local controller integrates the bus voltage reflecting the instantaneous energy balance with the received data reflecting the overall resource status and changing trends of the system, comprehensively judges the current operating condition, and then dynamically matches the corresponding droop control coefficient, adjusting its own power output accordingly. The droop control coefficient refers to the adjustment parameter used by the distributed power unit 150 in the droop control strategy to characterize the mapping relationship between voltage deviation and output current. Each distributed power unit 150 matches the corresponding droop control coefficient according to the current operating condition, making the output characteristics of this unit adapt to the actual energy state of the system, thereby realizing power distribution and voltage support under multi-unit parallel conditions.

[0030] In this way, the current droop control coefficient is determined based on the current operating conditions, which reflect the real-time operating status of the system. The current droop control coefficient adaptively adjusts with changes in the system's operating status, perfectly matching the current actual operating conditions of the system, resulting in high adaptability. Simultaneously, the energy management unit performs grid status prediction based on current operating data, current environmental data, historical operating data, and historical environmental data. The resulting current trend prediction data includes predicted changes in bus voltage, predicted changes in load power, and predicted changes in state of charge, reflecting the expected changes in bus voltage, load power, and energy storage capacity, respectively. The current operating conditions are determined based on the current bus voltage, current operating data, and current trend prediction data. That is, based on the real-time operating status of the system and combined with the expected changes in the system's operating status, the current operating conditions are determined before a significant deviation in bus voltage occurs. The current output power adjusted based on the current droop control coefficient is then adjusted accordingly in advance, improving control timeliness.

[0031] In practical implementation, the DC bus 110 adopts a DC 24V voltage level. The distributed power unit 150 is a plug-in photovoltaic-storage integrated pole, with each pole equipped with a 60W flexible photovoltaic module, a 24V / 20Ah built-in energy storage battery pack, and a bidirectional DC / DC converter. The output is directly connected to the DC bus 110, and the protection level is IP67. The energy storage unit 130 is a 24V / 50Ah distributed lithium iron phosphate battery pack, installed indoors on a wall, equipped with overcharge protection, over-discharge protection, overcurrent protection, short-circuit protection, and lightning protection to smooth power fluctuations and provide continuous power supply at night or in rainy weather. The DC load unit 120 includes a high-definition network camera, an access controller, one pipeline pressure sensor, one flow sensor, LED courtyard lights, and auxiliary electrical equipment; all loads are powered by DC 24V. Each distributed power unit 150 is internally equipped with the following functional modules: a real-time DC bus voltage sampling circuit, used to acquire the instantaneous voltage value of the DC bus 110 at a preset sampling period; a bidirectional DC / DC voltage regulation and current sharing control unit, used to adjust the direction and amplitude of power output; and a controller to execute an adaptive droop control method for power supply. The hardware structure and control hierarchy of each distributed power unit 150 are identical. The system supports hot-swappable access and automatic fault isolation. Each distributed power unit 150, energy storage unit 130, and DC load unit 120 is connected to the DC bus 110 via a standard waterproof quick-connect plug; the connection or disconnection of any device does not affect the operation of other devices. The system supports off-grid 24 / 7 operation and is suitable for distributed low-load scenarios such as zero-carbon park management areas, gatehouse camps, and maintenance stations.

[0032] In one possible implementation, after each sampling, the energy management unit first filters out abnormal data from the current operating data and current environmental data, and then stores the filtered data in the historical record to ensure the validity of the historical operating data and historical environmental data used in power grid state prediction. Specifically, abnormal data filtering involves comparing the sampled value with a corresponding preset valid range, and comparing the deviation of the sampled value from its preceding and following adjacent sampled values ​​with a preset deviation threshold. When a sampled value exceeds the preset valid range, or the deviation from its preceding and following adjacent sampled values ​​exceeds the preset deviation threshold, the sampled value is determined to be abnormal data and discarded. The sampled value is then replaced with the average of the two valid sampled values ​​preceding and following it. Abnormal data is typically caused by sensor malfunctions, communication interference, or instantaneous shocks. If not filtered out, it will directly contaminate the calculation basis of trend prediction after entering the historical record, leading to abrupt changes in the prediction results. Through the above filtering mechanism, all sampled values ​​used in power grid state prediction are within a reasonable range and change continuously, thereby ensuring the accuracy of the predicted changes in bus voltage, load power, and state of charge.

[0033] Specifically, the sampling period of the energy management unit can be set to 5 seconds, that is, the current operating data and the current environmental data are collected and updated every 5 seconds; historical operating data and historical environmental data can retain the sampling records of the most recent 72 hours.

[0034] In one possible implementation, the distributed power unit is specifically used for: Preliminary operating conditions are determined based on the current bus voltage and the predicted bus voltage change. The preliminary operating conditions are revised based on the current load data and the predicted load power change to obtain the revised operating conditions. The operating conditions are adjusted and corrected based on current energy storage data and predicted changes in state of charge to obtain the current operating conditions.

[0035] The system pre-sets multiple bus voltage ranges, each corresponding to a specific operating condition. For example, there's a light-load voltage regulation condition for excess energy, a balanced operating condition for energy equilibrium, a heavy-load condition for insufficient energy, and a low-power protection condition for severe energy shortage. Bus voltage is a direct indicator of the system's energy supply and demand balance: bus voltage rises when the energy supply exceeds the load demand, and falls when the supply is insufficient. Therefore, bus voltage is used as the primary criterion for determining the operating condition. The distributed power unit determines the preliminary operating condition based on the current bus voltage and the predicted bus voltage change. Specifically, it uses the operating condition corresponding to the voltage range the predicted voltage trend falls into as the preliminary operating condition, ensuring that the operating condition is determined before the actual voltage shift. Since bus voltage only reflects instantaneous energy balance and may be affected by transient disturbances or line voltage drops, it introduces current load data and predicted load power changes as a secondary criterion. The preliminary operating condition is then corrected based on the actual load demand and its direction of change, resulting in a corrected operating condition. This avoids misjudgments caused by voltage illusions and allows for early response to sudden load changes. The state of charge (SBC) of the energy storage unit is the safety boundary for the system's continuous power supply capability. Therefore, current energy storage data and predicted SBC changes are introduced as the third-level criterion. The corrected operating condition is finally adjusted and locked based on the stored energy quantity and its direction of change to obtain the current operating condition, ensuring that the system prioritizes entering high-power support or protection mode when the stored energy quantity is insufficient. The three-level judgment converges progressively in the order of initial voltage judgment, load correction, and energy storage locking. The criteria for each level are formed by fusing the corresponding current state quantity and predicted changes, balancing accuracy and foresight. When the trend prediction data is not updated or all predicted changes are zero, the criteria at each level degenerate into the corresponding current state quantity, and the system automatically reverts to the operating condition judgment based on the real-time state.

[0036] In one possible implementation, the distributed power unit is specifically used for: The predicted bus voltage is determined based on the current bus voltage and the predicted change in bus voltage. The predicted bus voltage is compared with the bus voltage ranges of multiple preset operating conditions; among them, adjacent operating condition ranges form hysteresis sub-ranges at the boundary. When the predicted bus voltage is not in the hysteresis sub-interval, the operating condition corresponding to the operating condition interval where the predicted bus voltage is located is determined as the preliminary operating condition; when the predicted bus voltage is in the hysteresis sub-interval, the previous operating condition is determined as the preliminary operating condition.

[0037] In practical applications, the predicted bus voltage is the sum of the current bus voltage and the predicted bus voltage change, representing the expected level of the bus voltage after a preset prediction period. Specifically, the system presets four voltage ranges: 27.0V to 28.8V for light load stabilization, 24.5V to 27.0V for balanced operation, 22.0V to 24.5V for heavy load, and below 22.0V for low-power protection. A boundary threshold exists between adjacent operating ranges, which is the dividing point between the two operating ranges on the bus voltage axis. The boundary threshold is configured with a hysteresis offset. Based on the hysteresis offset, two switching trigger thresholds in different directions are formed at the boundary of adjacent operating ranges: an upward switching threshold and a downward switching threshold. The rising switching threshold is the trigger threshold when switching from a low to a high operating condition, and is the sum of the boundary threshold and the hysteresis offset. The falling switching threshold is the trigger threshold when switching from a high to a low operating condition, and is the difference between the boundary threshold and the hysteresis offset. The voltage range between the rising and falling switching thresholds is the hysteresis sub-interval at the boundary of adjacent operating condition intervals. When the predicted bus voltage falls into a hysteresis sub-interval, the system does not reselect the operating condition based on the predicted bus voltage, but directly uses the previous operating condition as the preliminary operating condition. When the predicted bus voltage does not fall into any hysteresis sub-interval, the operating condition corresponding to its operating condition interval is directly determined as the preliminary operating condition. Fluctuations in the predicted bus voltage within the hysteresis sub-interval do not trigger operating condition switching. Operating condition switching is only performed when the predicted bus voltage continuously changes in a certain direction and crosses the switching threshold of the corresponding direction, thereby suppressing misjudgments of operating conditions caused by voltage transient jitter due to load switching, power output fluctuations, or sampling noise. Meanwhile, since the operating condition determination is based on the predicted bus voltage, when the predicted change in bus voltage indicates that the voltage is about to cross the switching threshold, the system can complete the operating condition switch in advance before the actual voltage shift, thus achieving proactive control.

[0038] It should be noted that when the predicted bus voltage is below 22.0V and the system enters low-power protection mode, the bus voltage has already dropped significantly. The target output current calculated according to the droop control coefficient exceeds the rated current of the distributed power supply unit. The target output current is limited to within the rated current by the limiting circuit, and each distributed power supply unit outputs a constant rated current. The energy storage unit stops discharging, and the energy management unit controls the load switches corresponding to non-core loads to disconnect, retaining power supply only to the core load. The available power of the system is concentrated on supplying the core load to maximize the power supply time of the core load. The system exits low-power protection mode only when the predicted bus voltage rises and crosses the rising switching threshold corresponding to 22.0V. In one possible implementation, the distributed power supply unit is specifically used for: Determine the predicted load rate based on current load data and predicted load power changes; When the predicted load rate is higher than the load limit corresponding to the initial operating condition, the initial operating condition will be revised to the operating condition corresponding to the higher load. When the predicted load rate is lower than the lower limit of the load corresponding to the initial operating condition, the initial operating condition will be revised to the operating condition corresponding to the lower load. When the predicted load rate is within the load range corresponding to the preliminary operating condition, the preliminary operating condition will be used as the corrected operating condition.

[0039] In practical applications, the distributed generation unit (DPG) divides the predicted load power change by the system's rated carrying capacity to obtain the load rate change within a preset prediction period. Then, it adds the current load rate from the current load data to this load rate change to obtain the predicted load rate. The DPG internally stores the load threshold ranges corresponding to each preliminary operating condition, including upper and lower load limits. When the predicted load rate is higher than the upper load limit corresponding to the preliminary operating condition, it indicates that the actual or impending power demand has exceeded the design carrying capacity of the preliminary operating condition. For example, when the system is in a light-load voltage regulation condition, if high-power equipment is about to start up, causing the predicted load rate to exceed the upper load limit of the light-load range, the bus voltage may not have yet fallen out of the light-load voltage range. If the system continues to maintain a small droop control coefficient under the light-load condition, it will not be able to respond promptly to the increased power gap, resulting in a significant subsequent drop in bus voltage. By revising the preliminary operating condition upwards to a balanced operating condition or a heavy-load condition, the DPG can increase its power output capacity in advance, offsetting the impact of sudden load changes before the voltage deviates significantly. When the predicted load rate is lower than the lower limit of the load corresponding to the initial operating condition, it indicates that the actual power demand is lower than the expected range of the initial operating condition. This situation usually occurs during dynamic processes such as rapid load shedding or a sharp increase in power generation. If the system continues to operate according to the high-power output strategy under high load conditions, the excess energy will cause the bus voltage to spike rapidly, leading to overvoltage risks. By correcting the initial operating condition downwards, the distributed power unit can reduce its output power in a timely manner, effectively suppressing voltage overshoot. When the predicted load rate is within the load range corresponding to the initial operating condition, it indicates that the voltage judgment result matches the actual load demand, and the system is in a relatively stable energy balance state. The initial operating condition can be directly used as the correction condition to avoid unnecessary control jitter caused by frequent corrections. It should be noted that higher load conditions and lower load conditions are relative concepts relative to the current initial operating condition, and their specific references depend on the system's preset operating condition classification sequence. In addition, the upper and lower load limits can be fixed percentage thresholds or adaptive thresholds that are dynamically adjusted based on ambient temperature, battery health status, or historical operating data. Specifically, the system presets the load rate threshold range for each operating condition: the load rate for light load stabilization is below 30%, the load rate for balanced operation is between 30% and 70%, and the load rate for heavy load is above 70%.

[0040] In one possible implementation, the distributed power unit is specifically used for: The predicted energy storage capacity is determined based on current energy storage data and predicted changes in state of charge. When the predicted energy storage capacity is lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition will be adjusted to the high power direction to obtain the current operating condition; When it is predicted that the energy storage capacity will not be lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition will be used as the current operating condition.

[0041] In practical applications, the predicted energy storage capacity is the sum of the current state of charge (SOC) and the predicted change in SOC, both expressed as percentages, representing the expected level of the energy storage unit's SOC after a preset prediction period. While the current bus voltage reflects the instantaneous power balance, it cannot directly characterize the system's continuous power supply capacity. Even after initial voltage assessment and load correction to determine the corrected operating condition, if the energy storage capacity is insufficient to support the power output or absorption requirements under that condition, the system still faces the risk of collapse. Therefore, this embodiment uses an energy storage capacity threshold as a mandatory constraint.

[0042] When the predicted energy storage capacity is lower than the energy storage capacity threshold corresponding to the corrected operating condition, the distributed power unit (DPMU) will forcibly adjust the corrected operating condition towards high power, regardless of the current voltage and load status, to obtain the current operating condition. For example, if the corrected operating condition is a light-load voltage regulation condition and the predicted energy storage capacity is lower than its corresponding energy storage capacity threshold, the corrected operating condition will be adjusted towards high power, becoming a balanced operating condition or a heavy-load operating condition. This allows the DPMU to increase power output in advance, slowing down the rate of energy storage capacity decline and preventing battery over-discharge. When the predicted energy storage capacity is not lower than the energy storage capacity threshold corresponding to the corrected operating condition, it indicates that the energy storage capacity can support the operating requirements of the corrected operating condition, and the corrected operating condition will be directly adopted as the current operating condition. This control logic, which prioritizes safety over efficiency, constitutes the last line of defense in the operating condition identification mechanism. By making judgments based on the predicted energy storage capacity, the system can enter a high-power support state before the energy storage capacity actually falls below the safety threshold, slowing down the rate of energy storage capacity decline and further reducing the risk of battery over-discharge and voltage collapse. Furthermore, when the corrected operating condition is already in the direction of highest power, the corrected operating condition will be used as the current operating condition. Specifically, the system presets a safe threshold for the state of charge (SOC) for each operating condition: both the light load voltage regulation condition and the balanced operating condition require the SOC to be higher than 30%. When the SOC is not higher than 30%, regardless of the voltage and load status indications, the corrected operating condition will be adjusted towards the high power direction.

[0043] In one possible implementation, the distributed power unit is specifically used for: Obtain the system voltage deviation, the rated current of the distributed power supply unit, and the current adjustment factor corresponding to the current operating condition; The reference droop slope is determined based on the ratio of the rated current of the distributed power unit to the voltage deviation of the system. Multiply the baseline droop slope by the current adjustment factor to obtain the droop control coefficient.

[0044] In practical applications, system voltage deviation refers to the maximum allowable voltage drop range or steady-state voltage regulation rate determined during the design phase of a DC microgrid, reflecting the system's rigid constraints on power quality. The rated current of a distributed power unit (DPMU) is an inherent capacity attribute of the device itself, referring to the output current that enables the unit to operate continuously and safely over a long period. The baseline droop slope calculated based on these two physical quantities essentially characterizes the fundamental external characteristics of the DPMU under the premise of meeting system voltage quality requirements, i.e., the current regulation per unit voltage deviation. Regardless of the system's operating conditions, this baseline droop slope remains constant, ensuring that the device will not experience voltage collapse or device damage due to overload under any circumstances, providing a solid safety foundation for the control strategy. The current regulation factor is a dimensionless coefficient that dynamically changes with the current operating conditions, representing the system's control intent and strategy orientation under specific operating conditions. For example, under light-load voltage regulation conditions, to suppress circulating current between parallel units, the current adjustment factor can be set to a value less than 1, making the actual droop control coefficient less than the reference droop slope, thereby reducing the current response of the units to voltage deviations and enhancing current sharing stability. Under balanced operating conditions, the current adjustment factor can be set to a value of 1 or close to 1, allowing the system to return to standard external characteristics to achieve precise current sharing proportional to capacity. Under heavy-load conditions, to enhance the support capability for bus voltage, the current adjustment factor can be set to a value greater than 1, making the actual droop control coefficient greater than the reference droop slope, thereby improving the unit's response gain to voltage dips and the upper limit of power output. Through this multiplicative coupling relationship, the system effectively decouples the reference parameters reflecting hardware physical constraints from the adjustment parameters reflecting software control strategies.

[0045] This separate design allows the same hardware platform to flexibly adapt to various complex operating conditions through software-level factor adjustments, without needing to readjust underlying electrical parameters or replace hardware components for each condition, greatly improving the system's versatility and scalability. Furthermore, transforming abstract control strategies into quantifiable and traceable parameter mapping relationships avoids the blind reliance on trial-and-error or empirical formulas to set droop coefficients in traditional methods. It should be understood that although this embodiment describes a multiplicative linear adjustment model, in other implementations, nonlinear methods such as piecewise functions, polynomial fitting, or neural network mapping can also be used to establish the relationship between the baseline droop slope and the current adjustment factor. Moreover, the specific value of the current adjustment factor can be either a preset discrete constant or a dynamic variable that continuously changes based on load factor, energy storage state of charge, or ambient temperature, to adapt to more refined energy management needs.

[0046] Specifically, the system voltage deviation can be set to 2V, the rated current of the first distributed power supply unit is 2A, and the rated current of the second distributed power supply unit is 1A. The reference voltage is set to 28.0V. The current adjustment factors corresponding to the four operating conditions are as follows: 0.6 for light load regulation, used to reduce unit output to suppress circulating current between parallel units; 1.0 for balanced operation, used to revert to standard out-of-specification characteristics to achieve accurate capacity-proportional current sharing; and 1.8 for heavy load, used to improve the unit's response gain to voltage dips and the upper limit of power output. The reference droop slope of the first distributed power supply unit is 2÷2=1A / V, and the reference droop slope of the second distributed power supply unit is 1÷2=0.5A / V. Under light load regulation, the droop control coefficient of the first distributed power supply unit is 1×0.6=0.6A / V, and the droop control coefficient of the second distributed power supply unit is 0.5×0.6=0.3A / V. Under balanced operating conditions, the droop control coefficient of the first distributed power supply unit is 1 × 1.0 = 1.0 A / V, and the droop control coefficient of the second distributed power supply unit is 0.5 × 1.0 = 0.5 A / V. Under heavy load conditions, the droop control coefficient of the first distributed power supply unit is 1 × 1.8 = 1.8 A / V, and the droop control coefficient of the second distributed power supply unit is 0.5 × 1.8 = 0.9 A / V.

[0047] In one possible implementation, the distributed power unit is specifically used for: Obtain the current reference voltage; The target output current is determined based on the voltage difference between the current reference voltage and the current bus voltage, as well as the droop control factor. Adjust the current output current to the target output current.

[0048] In practical applications, the current reference voltage is the reference voltage value of the DC microgrid system under ideal no-load conditions. It serves as the voltage anchor point followed by all distributed generation units (DPGs), defining the system's energy balance baseline. During actual operation, the DPGs collect the current bus voltage of the DC bus in real time and calculate the voltage difference between it and the current reference voltage. This voltage difference essentially reflects the system's current power deficit or surplus: when the bus voltage is lower than the reference voltage, the difference is positive, indicating that the system needs to inject power to support the voltage; conversely, it indicates that the system needs to absorb power or reduce its output. The DPGs use the current droop control coefficient to linearly map this voltage difference, thereby calculating the target current value that should be output at the current moment. This mapping relationship can be expressed by the following formula:

[0049] in, For the target output current, The current reference voltage, This is the current bus voltage. This is the current droop control coefficient. The target output current, after being limited by a limiting circuit to within the rated current of the distributed power unit, is used as the setpoint for the inner current loop. Through this formula, the system transforms the abstract voltage regulation requirement into a specific current quantization command. Subsequently, the local current control loop within the distributed power unit receives this target output current as the setpoint and drives the actual output current to quickly track the target value by adjusting the switching duty cycle of the power electronic converter. This dual-loop control structure, consisting of current commands generated by the outer droop characteristic and tracking commands by the inner current loop, ensures both accurate current sharing and voltage support in steady state and dynamic response speed and stability during transient processes.

[0050] Because all distributed power supply units connected in parallel to the DC bus share the same physical bus voltage signal Furthermore, each unit uses the same reference voltage. With consistent coefficient generation logic, therefore for any two distributed power units with different rated capacities, although their calculated current droop control coefficients are consistent... The numerical values ​​differ, but this coefficient is strictly proportional to its rated capacity. Substituting into the target current calculation formula above, we can see that the target output current of each unit is... The load is necessarily proportional to its rated capacity. This means that without any inter-unit communication handshakes, master-slave allocation commands, or central scheduling coordination, each distributed power unit can naturally share the system load according to its own capacity ratio simply by locally sensing and autonomously calculating the common bus voltage. This self-balancing mechanism, based on the inherent consistency of physical circuit topology and control algorithms, completely eliminates the dependence on communication links in traditional centralized or master-slave control, giving the system true plug-and-play capability and extremely high fault tolerance. Even if a unit in the system fails and exits or a new unit is hot-swapped in, the remaining units can still automatically redistribute power based on unchanging physical laws to maintain the stability of the bus voltage.

[0051] In one possible implementation, the energy storage unit is used for: The system collects the current bus voltage of the DC bus and receives current operating data and current trend prediction data from the energy management unit; based on the current bus voltage, current operating data, and current trend prediction data, it determines the current operating condition according to the same operating condition identification logic as the distributed power unit; and adjusts the current charging and discharging power based on the current operating condition and current energy storage data.

[0052] In practical applications, the energy storage unit is equipped with a local controller. Its method of acquiring bus voltage, the content of the received data, and the judgment logic for operating condition identification are exactly the same as those of the distributed power unit. Since the judgment input of the energy storage unit and each distributed power unit is exactly the same, and they use the same operating condition identification logic, the current operating condition determined by the two at the same time will necessarily be consistent. The energy storage unit can know the current energy state of the system without communicating and negotiating with any distributed power unit.

[0053] After determining the current operating conditions, the energy storage unit further determines its charging and discharging actions based on the current energy storage data. The current operating conditions characterize the energy supply and demand status of the system, while the current energy storage data characterizes the energy storage unit's own charge level. Together, they determine whether the energy storage unit should charge, discharge, or stop charging and discharging. Thus, the charging and discharging actions of the energy storage unit complement the output reduction of each distributed power unit. That is, when the system has surplus energy, the distributed power units reduce their output, and the energy storage unit charges to absorb the surplus energy; when the system has insufficient energy and the energy storage capacity allows, the distributed power units increase their output, and the energy storage unit discharges, jointly supporting the bus voltage.

[0054] In this way, the distributed power unit can autonomously output power according to its capacity ratio through the droop characteristic, and the energy storage unit can perform coordinated charging and discharging according to the operating conditions and energy storage status. The two can achieve coordinated operation based only on the common signal of bus voltage and the same status data, without the need for a centralized controller to allocate power, thus avoiding the conflict between energy storage charging and discharging decisions and power droop control strategies.

[0055] In one possible implementation, the energy storage unit is specifically used for: When the current operating condition is light load voltage regulation or balanced operation, and the current energy storage data is lower than the preset charging limit, the energy storage unit is controlled to charge. When the current operating condition is a heavy load condition, the energy storage unit is controlled to discharge or stop charging and discharging based on the comparison result between the current energy storage data and the preset energy threshold. When the current operating condition is the low-power protection condition, the control energy storage unit stops discharging.

[0056] In practical applications, when the system is under light-load voltage regulation or balanced operation, the bus voltage is at a relatively high level, indicating that the bus energy supply exceeds the load demand and there is surplus photovoltaic output. At this time, if the state of charge (SBC) of the energy storage unit is below the preset charging limit, the energy storage unit will charge to store the surplus energy on the bus, preventing further increases in bus voltage and storing energy for nighttime or rainy periods. When the SBC reaches the preset charging limit, the energy storage unit will stop charging to prevent overcharging.

[0057] When the system is under heavy load, the bus voltage drops significantly, indicating insufficient energy supply and requiring energy storage units to provide power support. However, whether the energy storage unit can discharge depends on its own charge level. At this time, the energy storage unit compares its current energy storage data with a preset charge threshold: if the state of charge is higher than the preset charge threshold, it means there is surplus energy, and the energy storage unit discharges to jointly supply power with the distributed power units to support the bus voltage; if the state of charge is not higher than the preset charge threshold, it means the energy storage charge is too low, and the energy storage unit stops charging and discharging and enters a static state. This avoids the battery from being over-discharged, causing the energy storage to permanently shut down, and also prevents the energy storage unit from drawing power from the DC bus to charge when the system's energy supply is insufficient, which would further exacerbate the power deficit.

[0058] When the system enters the low-power protection mode, the bus voltage is lower than the protection voltage threshold and the energy storage capacity is insufficient. Neither the photovoltaic output nor the energy storage capacity can support the entire load. The energy storage unit stops discharging, and the system only retains power supply to the core load to maximize the survival time of critical services.

[0059] Specifically, the preset battery threshold can be set to 30%, and the preset charging limit can be set to 90%.

[0060] It should be understood that the charging and discharging power amplitude of the energy storage unit under various operating conditions can be dynamically adjusted according to its rated capacity and current state of charge. For example, the closer the state of charge is to the preset energy threshold, the smaller the discharge power, so as to smoothly transition the stored energy to the state of stopping discharge. In addition, the preset energy threshold and the preset charging upper limit can be fixed values ​​or dynamically adjusted according to factors such as battery health status and ambient temperature.

[0061] In one possible implementation, see [reference] Figure 2 As shown, the DC load unit 120 includes: multiple loads 121 of different levels and multiple load switches 122; Each load 121 is connected to the DC bus 110 through a corresponding load switch 122; the control terminal of each load switch 122 is connected to the energy management unit 140. The energy management unit 140 is also used to control the on / off state of each load switch 122 according to the load level of the load 121 based on the current bus voltage and / or current energy storage data.

[0062] In practical applications, multiple loads 121 of different levels are typically categorized based on their importance to system operation. For example, the first-level loads 121 may include core equipment ensuring basic security and data acquisition for the park, such as security monitoring cameras, access control controllers, and key sensors; the second-level loads 121 may include improvement facilities such as LED courtyard lights and information display screens; and the third-level loads 121 may include comfort-oriented electrical equipment such as USB charging ports, decorative lighting, or non-essential auxiliary heating devices. Each level of load 121 is equipped with an independent load switch 122, which can be a relay, a MOSFET solid-state switch, or a smart circuit breaker. Its on / off state is directly controlled by digital commands issued by the energy management unit 140. This physical branch control design enables the system to have refined power trimming capabilities, rather than a crude operation that can only perform full shutdown or full supply.

[0063] At the control strategy level, the energy management unit 140 monitors the current bus voltage and current energy storage data in real time and compares them with preset multi-level unloading thresholds to generate corresponding load 121 switching commands. When the system is in normal operating range, all load switches 122 remain closed to ensure full power supply. When the current bus voltage is detected to be continuously lower than the first-level unloading threshold, or the current energy storage data is lower than the first-level unloading capacity threshold, the energy management unit 140 determines that the system has entered a mild energy shortage state. At this time, the load switch 122 corresponding to the third-level load 121 is disconnected first to release power margin. If the bus voltage still cannot recover and remains below the second-level unloading threshold after taking the above measures, or the energy storage capacity continues to decrease and falls below the second-level unloading capacity threshold, the load switch 122 corresponding to the second-level load 121 is further disconnected, leaving only the most critical first-level load 121 running. When energy shortage intensifies, the bus voltage drops below the preset protection voltage threshold, and the current energy storage data is lower than the preset protection capacity threshold, the energy management unit 140 controls the load switches 122 corresponding to all non-core loads 121 to disconnect, retaining power only for core loads 121 such as security monitoring cameras, access controllers, and critical sensors. Specifically, the preset protection voltage threshold can be set to 22.0V, and the preset protection capacity threshold can be set to 30%.

[0064] It should be understood that although this embodiment describes a sequential unloading logic based on a fixed priority sequence, in other embodiments, the classification and control strategies for load 121 levels can be more flexible and diverse. For example, load 121 levels can be dynamically redefined according to time periods, increasing the priority of monitoring load 121 during nighttime security periods and increasing the priority of office auxiliary load 121 during daytime working periods. Furthermore, the unloading triggering conditions are not limited to a single voltage or power threshold; multi-parameter fusion criteria such as voltage change rate, energy storage discharge power, or current trend prediction data can also be used to achieve more proactive energy management. Simultaneously, in addition to centralized control, the control method for load switches 122 can also employ distributed intelligent node control, where each load switch 122 has a built-in local logic chip that directly senses the bus voltage and autonomously executes a preset unloading program, thereby reducing dependence on the communication link of the energy management unit 140 and further improving the system's fault tolerance.

[0065] This application provides a power supply adaptive droop control method, see below. Figure 3 As shown, the general flow of the power supply adaptive droop control method provided in this application embodiment is as follows: Step 301: Collect the current bus voltage of the DC bus and receive the current operating data and current trend prediction data from the energy management unit; wherein, the current operating data includes the current load data, current energy storage data and current power generation data; the current trend prediction data includes the predicted bus voltage change, the predicted load power change and the predicted state of charge change.

[0066] Step 302: Determine the current operating conditions based on the current bus voltage, current operating data, and current trend forecast data.

[0067] Step 303: Determine the current droop control coefficient based on the current operating conditions.

[0068] Step 304: Adjust the current output power based on the current droop control coefficient.

[0069] In one possible implementation, see [reference] Figure 4 As shown, the current operating conditions are determined based on the current bus voltage, current operating data, and current trend forecast data, including: Step 401: Determine the preliminary operating conditions based on the current bus voltage and the predicted bus voltage change.

[0070] Step 402: Correct the preliminary operating conditions based on the current load data and the predicted load power change to obtain the corrected operating conditions.

[0071] Step 403: Adjust and correct the operating conditions based on the current energy storage data and the predicted change in state of charge to obtain the current operating conditions.

[0072] In one possible implementation, determining the preliminary operating conditions based on the current bus voltage and the predicted bus voltage change includes: First, the predicted bus voltage is determined based on the current bus voltage and the predicted change in bus voltage.

[0073] Then, the predicted bus voltage is compared with the bus voltage ranges of multiple preset operating conditions; among them, adjacent operating condition ranges form hysteresis sub-ranges at the boundary.

[0074] Finally, when the predicted bus voltage is not in the hysteresis sub-interval, the operating condition corresponding to the operating condition interval where the predicted bus voltage is located is determined as the preliminary operating condition; when the predicted bus voltage is in the hysteresis sub-interval, the previous operating condition is determined as the preliminary operating condition.

[0075] In one possible implementation, the preliminary operating condition is corrected based on the current load data and the predicted load power change to obtain the corrected operating condition, including: Determine the predicted load rate based on current load data and predicted load power changes; When the predicted load is higher than the load limit corresponding to the initial operating condition, the initial operating condition is revised to the operating condition corresponding to the higher load. When the predicted load is lower than the lower limit of the load corresponding to the initial operating condition, the initial operating condition is revised to the operating condition corresponding to the lower load. When the load is predicted to be within the load range corresponding to the preliminary operating condition, the preliminary operating condition is used as the corrected operating condition.

[0076] In one possible implementation, the current operating condition is obtained by adjusting the corrected operating condition based on current energy storage data and predicted changes in state of charge, including: The predicted energy storage capacity is determined based on current energy storage data and predicted changes in state of charge. When the predicted energy storage capacity is lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition will be adjusted to the high power direction to obtain the current operating condition; When it is predicted that the energy storage capacity will not be lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition will be used as the current operating condition.

[0077] In one possible implementation, see [reference] Figure 5 As shown, the current droop control coefficient is determined based on the current operating conditions, including: Step 501: Obtain the system voltage deviation, the rated current of the distributed power supply unit, and the current adjustment factor corresponding to the current operating condition.

[0078] Step 502: Determine the reference droop slope based on the ratio of the system voltage deviation to the rated current of the distributed power supply unit.

[0079] Step 503: Multiply the baseline droop slope by the current adjustment factor to obtain the droop control coefficient.

[0080] It should be noted that although several units or sub-units of the device have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of this application, the features and functions of two or more units described above can be embodied in one unit. Conversely, the features and functions of one unit described above can be further divided and embodied by multiple units.

[0081] Furthermore, although the operations of the method of this application are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0082] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0083] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the spirit and scope of the embodiments of this application. Therefore, if these modifications and variations to the embodiments of this application fall within the scope of the claims of this application and their equivalents, this application also intends to include these modifications and variations.

Claims

1. A DC microgrid system, characterized in that, include: The system includes a DC bus, a DC load unit, an energy storage unit, an energy management unit, and multiple distributed power supply units; the energy management unit is connected to the DC load unit, the energy storage unit, and the multiple distributed power supply units respectively; the DC load unit, the energy storage unit, and the multiple distributed power supply units are each connected to the DC bus. The energy management unit is used to acquire current operating data and current environmental data; based on the current operating data, current environmental data, historical operating data, and historical environmental data, it performs grid state prediction to obtain current trend prediction data; and sends the current operating data and the current trend prediction data to each of the distributed power generation units and the energy storage units; wherein, the current operating data includes current load data, current energy storage data, and current power generation data; and the current trend prediction data includes predicted bus voltage changes, predicted load power changes, and predicted state of charge changes. The distributed power supply unit is used to collect the current bus voltage of the DC bus and receive the current operating data and the current trend prediction data from the energy management unit; determine the current operating condition based on the current bus voltage, the current operating data and the current trend prediction data; determine the current droop control coefficient based on the current operating condition; and adjust the current output power based on the current droop control coefficient.

2. The DC microgrid system as described in claim 1, characterized in that, The distributed power supply unit is specifically used for: The preliminary operating conditions are determined based on the current bus voltage and the predicted bus voltage change. The preliminary operating condition is corrected based on the current load data and the predicted load power change to obtain the corrected operating condition; The corrected operating condition is adjusted based on the current energy storage data and the predicted change in state of charge to obtain the current operating condition.

3. The DC microgrid system as described in claim 2, characterized in that, The distributed power supply unit is specifically used for: The predicted bus voltage is determined based on the current bus voltage and the predicted bus voltage change. The predicted bus voltage is compared with the bus voltage range of multiple preset operating conditions; wherein, adjacent operating condition ranges form hysteresis sub-ranges at the boundary. When the predicted bus voltage is not in the hysteresis sub-interval, the operating condition corresponding to the operating condition interval where the predicted bus voltage is located is determined as the preliminary operating condition; when the predicted bus voltage is in the hysteresis sub-interval, the previous operating condition is determined as the preliminary operating condition.

4. The DC microgrid system as described in claim 2, characterized in that, The distributed power supply unit is specifically used for: The predicted load rate is determined based on the current load data and the predicted load power change. When the predicted load is higher than the upper limit of the load corresponding to the preliminary operating condition, the preliminary operating condition is revised to the operating condition corresponding to the higher load. When the predicted load is lower than the lower limit of the load corresponding to the preliminary operating condition, the preliminary operating condition is corrected to the operating condition corresponding to the lower load. When the predicted load is within the load range corresponding to the preliminary operating condition, the preliminary operating condition is used as the corrected operating condition.

5. The DC microgrid system as described in claim 2, characterized in that, The distributed power supply unit is specifically used for: The predicted energy storage capacity is determined based on the current energy storage data and the predicted change in state of charge. When the predicted energy storage capacity is lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition is adjusted to the high power direction to obtain the current operating condition; When the predicted energy storage capacity is not lower than the energy storage capacity threshold corresponding to the corrected operating condition, the corrected operating condition is taken as the current operating condition.

6. The DC microgrid system as described in claim 1, characterized in that, The distributed power supply unit is specifically used for: Obtain the system voltage deviation, the rated current of the distributed power supply unit, and the current adjustment factor corresponding to the current operating condition; The reference droop slope is determined based on the ratio of the rated current of the distributed power unit to the voltage deviation of the system. The droop control coefficient is obtained by multiplying the baseline droop slope by the current adjustment factor.

7. The DC microgrid system according to any one of claims 1-6, characterized in that, The energy storage unit is used for: The system collects the current bus voltage of the DC bus and receives the current operating data and the current trend prediction data from the energy management unit; based on the current bus voltage, the current operating data, and the current trend prediction data, it determines the current operating condition according to the same operating condition identification logic as the distributed power unit. Adjust the current charging and discharging power based on the current operating conditions and the current energy storage data.

8. The DC microgrid system as described in claim 7, characterized in that, The energy storage unit is specifically used for: When the current operating condition is a light-load voltage stabilization condition or a balanced operating condition, and the current energy storage data is lower than the preset charging upper limit, the energy storage unit is controlled to charge. When the current operating condition is a heavy load condition, the energy storage unit is controlled to discharge or stop charging and discharging based on the comparison result between the current energy storage data and the preset power threshold. When the current operating condition is a low-power protection condition, the energy storage unit is controlled to stop discharging.

9. The DC microgrid system as described in claim 1, characterized in that, The DC load unit includes: multiple loads of different levels and multiple load switches; Each load is connected to the DC bus via a corresponding load switch; the control terminal of each load switch is connected to the energy management unit. The energy management unit is also used to control the on / off state of each load switch according to the load level based on the current bus voltage and / or the current energy storage data.

10. A power supply adaptive droop control method, characterized in that, The method, applied to a distributed power supply unit in a DC microgrid system as described in any one of claims 1-9, comprises: The system collects the current bus voltage of the DC bus and receives current operating data and current trend prediction data from the energy management unit; wherein, the current operating data includes current load data, current energy storage data, and current power generation data; the current trend prediction data includes predicted changes in bus voltage, predicted changes in load power, and predicted changes in state of charge; The current operating condition is determined based on the current bus voltage, the current operating data, and the current trend prediction data. Determine the current droop control coefficient based on the current operating conditions; Adjust the current output power based on the current droop control coefficient.

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