Hybrid energy storage collaborative control method, device and equipment of direct current micro-grid and storage medium

Abstract

The application discloses a hybrid energy storage collaborative control method, device and equipment of a direct-current microgrid and a storage medium, relates to the technical field of renewable energy microgrids, and comprises the following steps: calculating a total compensation current according to a direct-current bus voltage, a preset bus voltage reference value and a voltage proportional integral controller; the total compensation current is decomposed into high-frequency and low-frequency components through a high-pass filter, and the high-frequency and low-frequency components are used as reference currents of sodium ion batteries and flow batteries respectively; the reference currents are sent to respective converters to control charging and discharging currents, so that fast response and continuous power balance are realized; meanwhile, in combination with a battery state of charge, photovoltaic power, load power and loss power, control instructions containing start-stop states and power set values are sent to a hydrogen electrolysis tank and a hydrogen fuel cell, so that the hybrid energy storage collaborative control is completed. The application improves the voltage stability of a photovoltaic direct-current microgrid and prolongs the service life of an energy storage system.

Description

Technical Field

[0001] This application relates to the field of renewable energy microgrid technology, and in particular to a hybrid energy storage collaborative control method, device, equipment and storage medium for DC microgrids. Background Technology

[0002] As one of the most promising renewable energy sources, photovoltaic (PV) power is seeing its penetration rate continuously increase in microgrids. However, PV output power is significantly affected by factors such as light intensity and temperature, exhibiting strong intermittency (fluctuations on the order of seconds to hours) and diurnal periodicity (no output at night). This makes it difficult for a single PV power source to meet the continuous and stable demands of the load, necessitating the support of efficient energy storage systems and control strategies.

[0003] Traditional microgrid energy storage technologies have the following shortcomings: (1) Single energy storage technologies cannot meet both power and energy demands: Although lithium batteries have a fast response (ms level), their cycle life is short (<5000 times) and long-term operating costs are high; flow batteries have low energy density and long cycle life (>10000 times), but their power response is slow (hundredsms level), making it difficult to cope with high-frequency power fluctuations; hydrogen energy storage (electrolyzer + fuel cell) is suitable for long-term energy time shifts (across days / seasons), but its dynamic response is poor (minute level), and it cannot compensate for instantaneous power shortages. (2) Hybrid energy storage control strategies do not fully utilize technical characteristics: Existing methods mostly use a combination of "lithium battery + supercapacitor", but do not optimize power allocation according to energy storage response characteristics. For example, allocating high-frequency fluctuations to flow batteries (slow response) leads to frequent charging and discharging of flow batteries, shortening their lifespan; or allocating low-frequency fluctuations to lithium batteries (small capacity) limits the system's continuous power supply capability. (3) Insufficient coordinated dispatch of photovoltaic-hydrogen-energy storage: Excess photovoltaic power is not efficiently converted into hydrogen energy storage. At night or during periods of low light, the system relies on a single energy storage system for power supply, which is prone to deep discharge of the energy storage system, affecting system reliability. The problem of bus voltage fluctuation caused by the intermittency of photovoltaic power generation remains prominent. The system reliability and energy storage lifespan are difficult to meet the long-term off-grid operation requirements in remote areas. Therefore, how to improve the voltage stability of photovoltaic DC microgrids and extend the lifespan of energy storage systems has become an urgent problem to be solved.

[0004] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The purpose of this application is to provide a hybrid energy storage collaborative control method, device, equipment and storage medium for DC microgrids, aiming to solve the technical problem of how to improve the voltage stability of photovoltaic DC microgrids and extend the life of energy storage systems.

[0006] To achieve the above objectives, this application proposes a hybrid energy storage coordinated control method for DC microgrids, the method comprising:

[0007] The total compensation current is calculated based on the DC bus voltage, the preset bus voltage reference value, and the voltage proportional-integral controller.

[0008] The total compensation current is decomposed into high-frequency and low-frequency components using a high-pass filter, and the high-frequency component is used as the reference current for the sodium-ion battery, while the low-frequency component is used as the reference current for the flow battery.

[0009] The sodium-ion battery reference current is sent to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current. The flow battery reference current is also sent to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current.

[0010] Based on the state of charge values ​​of the sodium-ion battery and the flow battery, control commands including start / stop status and power setpoints are sent to the hydrogen electrolyzer and hydrogen fuel cell according to the photovoltaic power, load power and loss power, to complete the hybrid energy storage coordinated control.

[0011] In one embodiment, the step of sending control commands containing start / stop status and power setpoints to the hydrogen electrolyzer and hydrogen fuel cell based on the state of charge values ​​of the sodium-ion battery and the flow battery, according to the photovoltaic power, load power, and loss power, to complete the hybrid energy storage coordinated control includes:

[0012] Calculate the total power consumption based on the load power and power loss, and calculate the power difference between the photovoltaic power and the total power consumption.

[0013] When the power difference is greater than the preset power threshold, the power difference is set as the input power value, and a start command containing the input power value is sent to the hydrogen electrolyzer.

[0014] When the power difference is less than the preset power threshold, a stop command is sent to the hydrogen electrolyzer.

[0015] When the state of charge of the sodium-ion battery and / or the flow battery is lower than the preset state of charge threshold, the hydrogen energy replenishment power value is calculated based on the current compensation power of the sodium-ion battery and the flow battery.

[0016] The hydrogen energy replenishment power value is set as the output power value, and a start command containing the output power value is sent to the hydrogen fuel cell to complete the hybrid energy storage collaborative control.

[0017] In one embodiment, before the step of setting the hydrogen energy replenishment power value as the output power value and sending a start command containing the output power value to the hydrogen fuel cell to complete the hybrid energy storage coordinated control, the method further includes:

[0018] Obtain the rated voltage value of the hydrogen fuel cell;

[0019] Calculate the output current based on the hydrogen energy replenishment power value and the rated voltage value;

[0020] The output current is sent to a bidirectional DC-DC converter, which generates a duty cycle signal based on the output current and adjusts the output voltage of the hydrogen fuel cell to the bus voltage based on the duty cycle signal.

[0021] The hydrogen utilization rate of the hydrogen fuel cell is monitored by a hydrogen concentration sensor;

[0022] Adjust the opening of the hydrogen supply valve according to the hydrogen utilization rate.

[0023] In one embodiment, the step of decomposing the total compensation current into high-frequency and low-frequency components using a high-pass filter, and using the high-frequency component as the reference current for the sodium-ion battery and the low-frequency component as the reference current for the flow battery includes:

[0024] Set the cutoff frequency of the high-pass filter;

[0025] The high-pass filter extracts a signal higher than the cutoff frequency from the total compensation current as a high-frequency component.

[0026] The low-frequency component is obtained by subtracting the high-frequency component from the total compensation current;

[0027] The high-frequency component is used as the reference current for the sodium-ion battery.

[0028] The low-frequency component is used as the reference current for the flow battery.

[0029] In one embodiment, the step of calculating the total compensation current based on the DC bus voltage, a preset bus voltage reference value, and a voltage proportional-integral controller includes:

[0030] Collect DC bus voltage;

[0031] Calculate the deviation between the DC bus voltage and the preset bus voltage reference value;

[0032] The deviation is proportionally calculated using the proportional term coefficient of the voltage proportional-integral controller to obtain the proportional calculation result;

[0033] The deviation is integrated using the integral term coefficient of the voltage proportional-integral controller to obtain the integral result;

[0034] The total compensation current is generated by superimposing the proportional calculation result and the integral calculation result.

[0035] In one embodiment, the step of sending the sodium-ion battery reference current to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current includes:

[0036] Set the current loop bandwidth of the sodium-ion battery to a first preset ratio of the switching frequency.

[0037] Configure the first proportional-integral parameter to the first current loop controller of the sodium-ion battery converter;

[0038] The reference current of the sodium-ion battery is sent to the sodium-ion battery converter, so that the sodium-ion battery converter generates a first duty cycle control signal according to the first current loop controller, and adjusts the switching timing of the bidirectional DC-DC converter according to the first duty cycle control signal, thereby controlling the charging and discharging current of the sodium-ion battery.

[0039] In one embodiment, the step of sending the flow battery reference current to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current includes:

[0040] Set the current loop bandwidth of the flow battery to a second preset ratio of the switching frequency;

[0041] Configure the second proportional-integral parameter to the second current loop controller of the flow battery converter;

[0042] The reference current of the flow battery is sent to the flow battery converter, so that the flow battery converter generates a second duty cycle control signal according to the second current loop controller, and adjusts the switching timing of the bidirectional DC-DC converter according to the second duty cycle control signal, thereby controlling the charging and discharging current of the flow battery.

[0043] Furthermore, to achieve the above objectives, this application also proposes a hybrid energy storage collaborative control device for a DC microgrid, the device comprising:

[0044] The calculation module is used to calculate the total compensation current based on the DC bus voltage, the preset bus voltage reference value, and the voltage proportional-integral controller.

[0045] The filtering module is used to decompose the total compensation current into high-frequency components and low-frequency components through a high-pass filter, and use the high-frequency components as the reference current for the sodium-ion battery and the low-frequency components as the reference current for the flow battery.

[0046] A hybrid energy storage module is used to send the sodium-ion battery reference current to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current, and to send the flow battery reference current to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current.

[0047] The hydrogen energy conversion module is used to send control commands, including start / stop status and power setpoints, to the hydrogen electrolyzer and hydrogen fuel cell based on the state of charge values ​​of the sodium-ion battery and the flow battery, according to the photovoltaic power, load power and loss power, to complete the coordinated control of hybrid energy storage.

[0048] Furthermore, to achieve the above objectives, this application also proposes a hybrid energy storage collaborative control device for a DC microgrid, the device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the hybrid energy storage collaborative control method for a DC microgrid as described above.

[0049] In addition, to achieve the above objectives, this application also proposes a storage medium, which is a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the steps of the hybrid energy storage coordinated control method for DC microgrids as described above.

[0050] In addition, to achieve the above objectives, this application also provides a computer program product, which includes a computer program that, when executed by a processor, implements the steps of the hybrid energy storage coordinated control method for DC microgrids as described above.

[0051] One or more technical solutions proposed in this application have at least the following technical effects:

[0052] First, the microgrid central management unit samples the DC bus voltage and compares it with a preset bus voltage reference value. A voltage proportional-integral controller generates a total compensation current, quantifies the voltage deviation in real time, and immediately generates a current command to cancel out any bus deviation. Then, a high-pass filter decomposes the total compensation current into high-frequency and low-frequency components. The high-frequency component is distributed to the sodium-ion battery, and the low-frequency component to the flow battery. This avoids the flow battery being subjected to high-frequency stress and the sodium-ion battery bearing long-term energy load, thus balancing the energy storage stress. Next, the high-frequency component is used as the reference current for the sodium-ion battery, and the low-frequency component as the reference current for the flow battery. The current is issued separately, and the sodium-ion battery converter quickly adjusts the duty cycle, making up for the instantaneous difference in milliseconds and the continuous difference in hundreds of milliseconds, which significantly suppresses the bus fluctuation. Finally, the battery state of charge value, photovoltaic power, load power and loss power are combined. If the photovoltaic is in surplus and the battery is not fully charged, the start / stop and power set value are issued to the hydrogen electrolyzer to produce hydrogen. If the photovoltaic is insufficient and the battery is below the preset state of charge value, the start / stop and power set value are issued to the hydrogen fuel cell to replenish the power. This realizes the three-level energy transfer of seconds, minutes and hours, which improves the voltage stability of the photovoltaic DC microgrid and extends the life of the energy storage system. Attached Figure Description

[0053] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0054] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a flowchart illustrating an embodiment of the hybrid energy storage coordinated control method for DC microgrids in this application.

[0056] Figure 2 A schematic diagram of the system architecture of a DC microgrid provided in Embodiment 1 of the hybrid energy storage collaborative control method for DC microgrids of this application;

[0057] Figure 3 This is a schematic diagram of the hybrid energy storage control process provided in Embodiment 1 of the hybrid energy storage collaborative control method for DC microgrids in this application;

[0058] Figure 4 This is a flowchart illustrating Embodiment 2 of the hybrid energy storage collaborative control method for DC microgrids in this application.

[0059] Figure 5 This is a schematic diagram of the energy management process provided in Embodiment 2 of the hybrid energy storage collaborative control method for DC microgrids in this application;

[0060] Figure 6 This is a schematic diagram of the module structure of the hybrid energy storage and collaborative control device for a DC microgrid according to an embodiment of this application;

[0061] Figure 7 This is a schematic diagram of the equipment structure of the hardware operating environment involved in the hybrid energy storage collaborative control method of DC microgrid in the embodiments of this application.

[0062] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0063] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0064] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0065] It should be noted that the executing entity of this application embodiment can be a computing service device with data processing, network communication, and program execution functions, such as a tablet computer, personal computer, or mobile phone, or an electronic device capable of realizing the above functions, such as a microgrid central management unit. The following uses a microgrid central management unit as an example to describe this embodiment and the following embodiments.

[0066] Based on this, embodiments of this application provide a hybrid energy storage collaborative control method for DC microgrids, referring to... Figure 1 , Figure 1 This is a flowchart illustrating the first embodiment of the hybrid energy storage collaborative control method for DC microgrids in this application.

[0067] In this embodiment, the hybrid energy storage coordinated control method for the DC microgrid includes steps S10 to S40:

[0068] Step S10: Calculate the total compensation current based on the DC bus voltage, the preset bus voltage reference value, and the voltage proportional-integral controller.

[0069] It should be noted that, please refer to Figure 2 , Figure 2This diagram illustrates the system architecture of a DC microgrid, as provided in Embodiment 1 of the hybrid energy storage collaborative control method for DC microgrids in this application. In the diagram, the photovoltaic array, as the core renewable energy source of the system, is connected to the DC load via a DC bus and simultaneously connected to the Central Management Unit (CMU). The CMU is responsible for real-time calculation of photovoltaic power, load demand, and energy storage SOC (State of Charge), generating start / stop commands for the electrolyzer / fuel cell and energy storage charging / discharging modes. The DC bus also connects to hydrogen fuel cells, electrolyzers, sodium-ion batteries (NIBs), vanadium redox flow batteries (VFBs), and sulfide-iron flow batteries (SFBs). These energy storage devices are connected in parallel to the DC bus via bidirectional DC-DC converters to achieve energy storage and release.

[0070] The hardware components of the DC microgrid are: (1) Photovoltaic array (PV): composed of 10 series and 8 parallel monocrystalline silicon modules with a rated power of 20kW (Standard Test Conditions, STC). , The photovoltaic array is connected to the 380V DC bus via a bidirectional DC-DC converter (switching frequency 10kHz). A P&O MPPT controller (disturbance step size 0.01, sampling period 10ms) is configured. The bidirectional DC-DC converter converts the low-voltage DC power generated by the photovoltaic array into a 380V voltage suitable for the DC bus. The P&O MPPT controller continuously adjusts the converter's duty cycle to ensure that the photovoltaic array always operates near the maximum power point, thereby improving the utilization efficiency of photovoltaic energy.

[0071] (2) Hydrogen Energy Conversion Module: ① Electrolyzer: A PEM (Proton Exchange Membrane) electrolyzer is used, with a rated power of 15kW and an input voltage of 380V. The proton exchange membrane electrolyzer has high electrolysis efficiency and stability, and its hydrogen generation rate formula is:

[0072]

[0073] in, =0.88, =120 electrolysis units In actual operation, It will change with the variation in excess photovoltaic power; when there is a significant excess photovoltaic power, Increase the hydrogen production rate by increasing the hydrogen production rate; conversely, decrease it by decreasing it. ② Fuel Cell (FC): Alkaline Fuel Cell (AFC), rated power 10kW, output voltage stabilized to 380V via a bidirectional DC-DC converter, hydrogen utilization rate... ≥92%, hydrogen storage tank capacity 20kg (pressure 30MPa).

[0074] (3) Hybrid energy storage module: ① Sodium-ion battery (NIB): rated capacity 50Ah, nominal voltage 72V (12 series), connected to the bus through a bidirectional DC-DC converter (switching frequency 10kHz), energy density 120Wh / kg, response time <10ms, responsible for high-frequency power buffer (>10Hz); ② Vanadium redox flow battery: rated power 8kW, capacity 200Ah (electrolyte volume 500L), efficiency 89%, response time <100ms, responsible for low-frequency power buffer (≤10Hz); ③ Sulfur-iron redox flow battery: rated power 7kW, capacity 180Ah, efficiency 91%, operated in parallel with VFB to enhance low-frequency power processing capability.

[0075] (4) DC bus: Capacitor 2200 Voltage 380V (with allowable fluctuations ±5%), connects to adjustable DC load (power range 5-25kW).

[0076] The control layer architecture of DC microgrid: (1) Local controller: Each module is independently controlled (PV MPPT, energy storage converter current loop, electrolyzer / fuel cell start-up and shutdown), and coordinated by bus voltage signal (380V±1V). (2) Central management unit: Real-time calculation of PV power, load demand and energy storage SOC, generating electrolyzer / fuel cell start-up and shutdown commands and energy storage charging and discharging modes.

[0077] The DC bus voltage refers to the actual instantaneous voltage value of the DC bus sampled at the current moment, reflecting the real-time status of the bus voltage. The preset bus voltage reference value is the target DC bus voltage value set to maintain stable system operation; the controller uses this as a reference for adjustment. The voltage proportional-integral controller (PIC) is a closed-loop control loop that uses the bus voltage deviation as input and generates a continuously adjusting signal through proportional and integral operations to achieve zero steady-state error voltage tracking. The total compensation current refers to the time-varying current command signal output by the PIC, representing the instantaneous current that needs to be injected or absorbed by the energy storage system to offset power differences and suppress bus voltage fluctuations.

[0078] As an example, the step of calculating the total compensation current based on the DC bus voltage, a preset bus voltage reference value, and a voltage proportional-integral controller includes: acquiring the DC bus voltage; calculating the deviation between the DC bus voltage and the preset bus voltage reference value; performing a proportional operation on the deviation using the proportional term coefficient of the voltage proportional-integral controller to obtain a proportional operation result; performing an integral operation on the deviation using the integral term coefficient of the voltage proportional-integral controller to obtain an integral operation result; and superimposing the proportional operation result and the integral operation result to generate the total compensation current.

[0079] The proportional gain coefficient (PGF) is the gain coefficient used to amplify the deviation in a voltage proportional-integral (PI) controller. A larger PGF value results in a faster response to instantaneous deviations. The proportional result is the immediate adjustment component obtained by multiplying the PGF by the DC bus voltage deviation, used to quickly suppress voltage fluctuations. The integral gain coefficient (IGF) is the gain coefficient used to accumulate the deviation in a voltage proportional-integral (PI) controller. Its value determines the system's ability and speed to eliminate steady-state errors. The integral result is the continuous adjustment component obtained by multiplying the integral gain coefficient by the accumulated DC bus voltage deviation over time, used to eliminate long-term steady-state errors and maintain zero steady-state error in the bus voltage.

[0080] First, the microgrid central management unit synchronously samples the DC bus voltage at a fixed frequency of 10 kHz (10 kilohertz). The switching glitches are removed using an 8th-order moving average filter to obtain the current instantaneous voltage value; then, this value is compared with the preset bus voltage reference value (380V reference value). The difference is calculated to obtain the voltage deviation (real-time voltage error). ),like A positive value indicates undervoltage at the busbar, while a negative value indicates overvoltage. Next, the PI controller... Simultaneously, two parallel processing channels are input: in the proportional channel, a preset... =0.42 (proportional coefficient) directly multiplied by Instantly output a value similar to Current components that are proportional in magnitude Used to immediately cancel voltage spikes; in the integration channel, using (Integral term coefficient) for Perform trapezoidal integral and multiply by The current component accumulated over time is obtained. This is used to gradually eliminate steady-state errors. Finally, and Algebraic addition forms the total compensation current. The complete calculation formula is as follows:

[0081]

[0082] Step S20: The total compensation current is decomposed into high-frequency and low-frequency components using a high-pass filter, and the high-frequency component is used as the reference current for the sodium-ion battery, while the low-frequency component is used as the reference current for the flow battery.

[0083] It should be noted that the high-pass filter refers to the first-order transfer function element used in this application, which has the following form:

[0084]

[0085] in, This refers to the input signal (i.e., the total compensation current). The high-pass filter, with a cutoff frequency of 10Hz, allows signal components above 10Hz to pass through with almost no attenuation, while components below 10Hz gradually attenuate as the frequency decreases, thus separating the fast-changing (high-frequency) and slow-changing (low-frequency) components in the total compensation current. The high-frequency component refers to the current signal with a frequency above 10Hz obtained after passing through the high-pass filter, corresponding to the rapid power compensation required for second-level photovoltaic surges or instantaneous load impacts. The low-frequency component refers to the slowly changing current signal below 10Hz remaining after subtracting the high-frequency component from the total compensation current, corresponding to minute-level continuous power deficits or surpluses. The sodium-ion battery reference current refers to using the high-frequency component directly as the instantaneous target value of the current loop of the sodium-ion battery bidirectional DC-DC converter. The converter tracks this value in real time, allowing the sodium-ion battery to immediately output or absorb the corresponding high-frequency power. The flow battery reference current refers to using the low-frequency component directly as the instantaneous target value of the current loop of the flow battery bidirectional DC-DC converter. The converter tracks this value in real time, allowing the flow battery to slowly release or store the corresponding low-frequency energy. A bidirectional DC-DC converter is a full-bridge synchronous buck-boost circuit connected between a 72V sodium-ion battery stack and a 380V DC bus. Through phase control of the same set of inductors and power switches, energy can be either stepped down from the bus to charge the battery or stepped up from the battery to discharge to the bus, achieving bidirectional adjustment of the current magnitude and direction.

[0086] As an example, the step of decomposing the total compensation current into high-frequency and low-frequency components using a high-pass filter, and using the high-frequency component as a reference current for the sodium-ion battery and the low-frequency component as a reference current for the flow battery includes: setting the cutoff frequency of the high-pass filter; extracting a signal higher than the cutoff frequency from the total compensation current using the high-pass filter as the high-frequency component; subtracting the high-frequency component from the total compensation current to obtain the low-frequency component; using the high-frequency component as the reference current for the sodium-ion battery; and using the low-frequency component as the reference current for the flow battery.

[0087] The cutoff frequency refers to the boundary value at which the gain of the high-pass filter drops to -3dB (approximately 0.707 times). Signals above this frequency pass through with almost no attenuation, while signals below this frequency are gradually attenuated. In this embodiment, this value is set to 10Hz to divide the total compensation current into two parts: the rapid fluctuations handled by the sodium-ion battery and the slow changes handled by the flow battery.

[0088] First, the microgrid central management unit adjusts the time constant of the first-order high-pass filter. Set the time to 0.0159s to ensure the cutoff frequency accurately falls within 10Hz; then, adjust the real-time total compensation current. When the signal is fed into this filter, a fast conversion component with a frequency greater than 10Hz is obtained at the output. Then use minus The slow-motion component ≤10Hz can be directly calculated. Finally, Immediately write to the sodium-ion battery's bidirectional DC-DC current loop reference register, allowing the battery to track discharge or charge within milliseconds, while simultaneously... The current loop reference register of the parallel branch of vanadium liquid flow and sulfur-iron liquid flow is synchronously written to enable the flow battery to respond smoothly on the scale of hundreds of milliseconds to hours, and to complete the fast and slow frequency division and power division.

[0089] Step S30: The sodium-ion battery reference current is sent to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current. The flow battery reference current is also sent to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current.

[0090] It should be noted that the sodium-ion battery converter refers to a bidirectional DC-DC power module with a rated switching frequency of 10kHz. Its input side is connected to a 72V sodium-ion battery stack, and its output side is connected to a 380V DC bus. It is responsible for quickly converting the current reference value issued by the central management unit into the actual charging and discharging current at the battery terminal. A sodium-ion battery (NIB) refers to a 72V / 3.6kWh battery stack consisting of 12 series of 50Ah sodium-ion cells, with a response time of <10ms, used for high-frequency power buffering. The flow battery converter refers to a bidirectional DC-DC power module connected in parallel to the 380V bus. In this embodiment, it corresponds to two branches: an 8kW vanadium redox flow and a 7kW ferrous sulfate flow. It has a switching frequency of 10kHz and a current loop bandwidth of 1kHz, and is used to convert the received low-frequency current reference value into the flow battery stack current. Flow batteries refer to vanadium redox flow batteries and sulfur-iron redox flow battery systems, which consist of an electrolyte storage tank, a stack, and a circulation pump. They have rated capacities of 200Ah and 180Ah, respectively, and a cycle life of >10,000 cycles, and are responsible for providing continuous energy support from minutes to hours.

[0091] As an example, the step of sending the sodium-ion battery reference current to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current includes: setting the current loop bandwidth of the sodium-ion battery to a first preset ratio of the switching frequency; configuring a first proportional-integral parameter to the first current loop controller of the sodium-ion battery converter; sending the sodium-ion battery reference current to the sodium-ion battery converter so that the sodium-ion battery converter generates a first duty cycle control signal according to the first current loop controller, and adjusts the switching timing of the bidirectional DC-DC converter according to the first duty cycle control signal, thereby controlling the charging and discharging current of the sodium-ion battery.

[0092] The current loop bandwidth refers to the small-signal -3dB cutoff frequency of the sodium-ion battery converter's current closed loop. A higher value results in a faster dynamic response; in this embodiment, it is set to 1.67kHz. The switching frequency refers to the periodic on / off frequency of the power semiconductor device, fixed here at 10kHz, providing a time base for the current loop and PWM (Pulse Width Modulation). The first preset ratio sets the current loop bandwidth to 1 / 6 of the switching frequency, ensuring the controller reliably tracks the reference current within 1.67kHz while avoiding switching noise amplification. The first proportional-integral parameter refers to the coefficient of the current loop PI controller. , This is used to determine the gain of the proportional and integral channels to achieve fast, zero steady-state error tracking. The first current loop controller refers to... , The core, discrete PI algorithm module running within a DSP (Digital Signal Processor), is responsible for converting current errors into duty cycle instructions. The first duty cycle control signal refers to the controller's control signal every 100 seconds. A set of values ​​between 0 and 1 (10kHz) output is used to set the conduction time ratio of the upper and lower transistors in the same bridge arm. The switching timing refers to the precise gate pulse sequence in each cycle, which turns on Q1 and Q4 first, and then Q2 and Q3 complementarily, according to the first duty cycle signal, so as to apply the reference current to the sodium-ion battery terminal in real time.

[0093] First, the microgrid central management unit sets the current loop bandwidth to one-sixth of the switching frequency and calculates the corresponding PI coefficient, which is then written into the current loop controller of the sodium-ion battery converter. This ensures the controller is fast without amplifying switching noise. Then, the sodium-ion battery reference current is transmitted via the CAN bus. The data is sent to the converter, and the DSP sends it every 100... Sample the actual current of the battery once ,and The error is obtained by subtracting the values, and after PI calculation, the duty cycle d (e.g., 0.35) is output. This value directly determines the inductor charging and discharging time ratio in the next cycle. Finally, a four-transistor complementary PWM is generated based on d, and Q1-Q4 switch according to the d:(1-d) timing sequence, so that the inductor current is exactly equal to the value in the next cycle. It achieves millisecond-level fast charging and discharging, which suppresses bus voltage fluctuations and avoids overcurrent in sodium-ion batteries.

[0094] As an example, the step of sending the reference current of the flow battery to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the reference current includes: setting the current loop bandwidth of the flow battery to a second preset ratio of the switching frequency; configuring a second proportional-integral parameter to the second current loop controller of the flow battery converter; sending the reference current of the flow battery to the flow battery converter so that the flow battery converter generates a second duty cycle control signal according to the second current loop controller, and adjusts the switching timing of the bidirectional DC-DC converter according to the second duty cycle control signal, thereby controlling the charging and discharging current of the flow battery.

[0095] The second preset ratio refers to fixing the current loop bandwidth to 1 / 10 of the switching frequency (i.e., 1kHz), enabling the flow battery to accurately track current commands and suppress switching noise even under slower dynamic conditions. The second proportional-integral parameter refers to the PI coefficient calculated corresponding to the 1kHz bandwidth. , The first current loop controller is used to set the proportional and integral gain of the current loop to achieve smooth, zero steady-state error control. The second current loop controller refers to the discrete PI algorithm module running within the flow battery converter's DSP. It takes the error between the flow battery's reference current and the actual current as input and outputs a duty cycle command. The second duty cycle control signal refers to the controller's duty cycle command every 100 seconds. The 0–1 values ​​are updated once to determine the on-time ratio of the four transistors in the bidirectional DC-DC converter, thereby accurately converting the reference current into the actual charging and discharging current of the flow battery.

[0096] First, the microgrid central management unit sets the current loop bandwidth of the flow battery to one-tenth of the switching frequency and calculates the corresponding PI coefficient, which is then written into the DSP of the flow battery converter. Subsequently, the reference current of the flow battery is transmitted via the CAN bus. Distribute, DSP every 100 Sample the actual current of the fuel cell stack ,and The error is obtained by subtraction, and after PI calculation, the duty cycle d is output (e.g., 0.45). Finally, a four-transistor complementary PWM is generated using d, and Q1-Q4 switch according to the d:(1-d) timing sequence, so that the stack current is exactly equal to the error in the next cycle. It achieves stable charging and discharging in milliseconds, satisfying continuous power balance while avoiding overcurrent in flow batteries.

[0097] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the hybrid energy storage control process provided in Embodiment 1 of the hybrid energy storage collaborative control method for DC microgrids according to this application. First, the central management unit of the microgrid acquires the current voltage value through bus voltage acquisition and then compares it with a preset voltage reference value to obtain the voltage deviation. The proportional-integral controller generates a total compensation current based on the voltage deviation. Then, a high-pass filter (with a cutoff frequency of 10Hz) decomposes the total compensation current into high-frequency and low-frequency components. The high-frequency component is used as the reference current for the sodium-ion battery, while the low-frequency component is used as the reference current for the flow battery. The sodium-ion battery current loop generates a duty cycle signal based on the reference current to control the sodium-ion battery bidirectional converter and adjust the charging and discharging current of the sodium-ion battery. Similarly, the flow battery current loop also generates a duty cycle signal to control the flow battery bidirectional converter and adjust the charging and discharging current of the flow battery. Finally, these currents work collaboratively through the DC bus to maintain the stable operation of the system.

[0098] Step S40: Based on the state of charge values ​​of the sodium-ion battery and the flow battery, and according to the photovoltaic power, load power, and loss power, control commands including start / stop status and power setpoints are sent to the hydrogen electrolyzer and the hydrogen fuel cell to complete the hybrid energy storage coordinated control.

[0099] It should be noted that the state of charge (SOC) value refers to the percentage of remaining charge in sodium-ion and flow batteries relative to their total capacity, used to determine whether the energy storage can continue to be charged and discharged. Photovoltaic power ( This refers to the real-time power output of the photovoltaic array under MPPT. MPPT uses the perturbation and observation (P&O) method, perturbing the converter duty cycle every 10ms. Adjust by comparing power changes before and after the disturbance Tracking maximum power point (MPP), photovoltaic output voltage under MPP conditions. Current ( ).

[0100] Load power ( Power loss refers to the total electrical power consumed by all electrical equipment on the DC bus at the same time. The term "electrical energy" refers to the electrical energy consumed by auxiliary equipment such as converters, lines, and pumps during energy conversion and transmission, typically estimated as a fixed percentage of the bus power. A hydrogen electrolyzer is a PEM electrolysis device that converts excess electrical energy from a 380V DC bus into hydrogen, with the hydrogen production rate determined by a given current. A hydrogen fuel cell is an alkaline fuel cell module that uses hydrogen from a storage tank to generate electricity and boosts the voltage to 380V via DC-DC converter when the bus power is insufficient. Control commands containing start / stop status and power setpoints are 16-bit data frames sent by the central management unit via the CAN bus. The high 8 bits represent the "start / stop flag" (0x01 for start, 0x00 for stop), and the low 8 bits represent the power percentage (0–100% corresponds to 0–rated power). Upon receiving this command, the electrolyzer or fuel cell immediately starts or stops operation according to this value.

[0101] Understandably, firstly, the central management unit reads the SOC (e.g., NIB=58%, VFB=22%) of the sodium-ion battery and flow battery every 100ms via CAN (Controller Area Network), and simultaneously collects data from the photovoltaic-side DC-DC (Direct-to-Direct-to-DC converter). (Photovoltaic voltage) (Photovoltaic current) multiplied together (For example: 315V × 63.5A = 20kW), then multiply the bus voltage sensor and the load Hall sensor to get... (For example: 380V × 52.6A = 20kW), while converting converter, pump, and line losses to 2% of the bus power. (For example: 0.4kW), thus calculating the real-time difference. Secondly, if If the SOC is greater than 0 and less than 90%, immediately send a start flag (e.g., 0x01) and power setting value to the PEM electrolyzer. (For example: 7.5kW), after receiving the electrolytic cell, it will be charged according to P= Adjust the input current by ×100% / 15kW (e.g., 19.7A) to convert excess electrical energy into hydrogen for storage. If the SOC is less than 0 and the SOC is less than 20%, then a start flag (e.g., 0x01) and a power setting value are sent to the alkaline fuel cell. (For example: 10kW), fuel cells are calculated using P= Adjust the hydrogen valve and fan by ×100% / 10kW to instantly fill the output current gap (e.g., 26.3A). Simultaneously, set the reference currents for NIB and VFB to high-frequency and low-frequency components respectively, allowing the battery to handle only instantaneous fluctuations and avoiding deep charging and discharging. Finally, the central unit continuously monitors the SOC and... Once SOC recovers to 30% or When the value approaches zero, i.e., a shutdown flag (e.g., 0x00) and a power setting of 0kW are issued, the electrolyzer or fuel cell immediately shuts down, and the battery takes over all the difference, thus completing the hybrid energy storage coordinated control of "battery fast response + hydrogen energy long-term support".

[0102] In one embodiment (a scenario with excess photovoltaic power, irradiance of 1000W / m², and a load of 12kW):

[0103] (1) System parameters: Photovoltaic output (STC condition), load System losses Electrolyzer efficiency Faraday constant The hydrogen tank has an initial capacity of 10 kg (with a remaining capacity of 10 kg).

[0104] (2) Power allocation calculation: excess power Electrolytic cell input current Hydrogen generation rate:

[0105]

[0106] (83g of hydrogen can be produced in 24 hours, and the remaining capacity of the hydrogen tank is 10kg - 0.083kg = 9.917kg, which is not fully filled); Energy storage and charging: Because the hydrogen tank is not full, hybrid energy storage will not be charged. ).

[0107] In one embodiment (a scenario with insufficient photovoltaic power, irradiance of 200W / m², and load of 20kW):

[0108] (1) System parameters: Photovoltaic output (Light intensity reduction of 80%), load System losses Power deficit NIB SOC=60% (usable capacity 30Ah), VFB SOC=70% (usable capacity 140Ah), SFB SOC=75% (usable capacity 135Ah).

[0109] (2) Power compensation steps:

[0110] ① High-frequency deficit compensation (>10Hz): Assuming the high-frequency component accounts for 30% (4.95kW) of the deficit, it is discharged by NIB: (≤1C=50A, permissible); NIB discharge power Duration (To meet immediate needs).

[0111] ② Low-frequency deficit compensation (≤10Hz): The low-frequency component accounts for 70% (11.55kW), discharged by VFB / SFB (VFB: 6kW, SFB: 5.55kW): (≤0.5C=100A) (≤0.5C=90A); VFB discharge time (VFB nominal voltage 380V, ); SFB discharge time (To meet long-term needs).

[0112] ③ Fuel cell startup: Because the energy storage SOC is greater than 20%, the fuel cell will not start temporarily; if the energy storage SOC drops to 20%, the fuel cell will start generating electricity. (Adjustments will be made proportionally if necessary to supplement the existing supplies). This refers to the output power of a hydrogen fuel cell.

[0113] This embodiment provides a hybrid energy storage collaborative control method for a DC microgrid. First, the microgrid's central management unit samples the DC bus voltage and compares it with a preset bus voltage reference value. A voltage proportional-integral controller generates a total compensation current, quantifies the voltage deviation in real time, and immediately generates a current command, ensuring that the bus deviation is canceled out as soon as it occurs. Then, a high-pass filter decomposes the total compensation current into high-frequency and low-frequency components. The high-frequency component is distributed to the sodium-ion battery, and the low-frequency component to the flow battery. This avoids the flow battery being subjected to high-frequency stress and the sodium-ion battery bearing long-term energy load, thus balancing the stress on each energy storage component. Finally, the high-frequency component is used as a reference voltage for the sodium-ion battery. The current and low-frequency components are sent as reference currents for the flow battery, and the sodium-ion battery converter quickly adjusts the duty cycle, making up for the instantaneous difference in milliseconds and the continuous difference in hundreds of milliseconds, which significantly suppresses the bus fluctuation. Finally, the battery state of charge value, photovoltaic power, load power and loss power are combined. If the photovoltaic is in excess and the battery is not fully charged, the start / stop and power set value are sent to the hydrogen electrolyzer to produce hydrogen. If the photovoltaic is insufficient and the battery is below the preset state of charge value, the start / stop and power set value are sent to the hydrogen fuel cell to replenish the power. This realizes the three-level energy transfer of seconds, minutes and hours, which improves the voltage stability of the photovoltaic DC microgrid and extends the life of the energy storage system.

[0114] Based on the first embodiment of this application, in the second embodiment of this application, the content that is the same as or similar to that in Embodiment 1 above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 4 , Figure 4 This is a flowchart illustrating the second embodiment of the hybrid energy storage coordinated control method for DC microgrids according to this application. Step S40 of the hybrid energy storage coordinated control method for DC microgrids includes steps S41 to S45:

[0115] Step S41: Calculate the total power consumption based on the load power and power loss, and calculate the power difference between the photovoltaic power and the total power consumption.

[0116] It should be noted that total power consumption refers to the sum of all load power on the DC bus and system loss power. It reflects the total amount of electrical energy actually consumed by the entire microgrid at a certain moment, including the electrical energy supplied to the loads and the electrical energy of various losses within the system (such as converter, line and other losses).

[0117] Understandably, the central management unit reads the bus voltage and total load current in real time, multiplies the two to get the load power, adds it to the power loss to get the total power consumption, and then subtracts the total power consumption from the photovoltaic power to get the power difference. If the result is positive, it means there is excess power; if it is negative, it means there is a shortage. This provides a basis for decision-making for subsequent hydrogen production or fuel cell power replenishment.

[0118] Step S42: When the power difference is greater than the preset power threshold, the power difference is set as the input power value, and a start command containing the input power value is sent to the hydrogen electrolyzer.

[0119] It should be noted that the preset power threshold refers to the boundary value for determining the surplus power of the bus. In this embodiment, it is set to 0W. As long as the power difference is greater than this value, it is considered that there is surplus electrical energy that can be used immediately. The input power value refers to the power command directly assigned to the hydrogen electrolyzer. Its value is equal to the power difference and is used to tell the electrolyzer how many kilowatts of surplus electrical energy to be put into hydrogen production.

[0120] Understandably, if the power difference exceeds the preset power threshold, it indicates that the current photovoltaic power is higher than the total power consumption, and there is surplus electrical energy. Secondly, this power difference is immediately assigned as the input power value, and a start command containing this input power value is sent to the PEM electrolyzer via the CAN communication protocol. Upon receiving the command, the electrolyzer adjusts its input current according to the ratio of the input power value to its rated power, using all the surplus electrical energy for water electrolysis to produce hydrogen, thus preventing the bus voltage from rising due to excess power.

[0121] Step S43: When the power difference is less than the preset power threshold, a stop command is sent to the hydrogen electrolyzer.

[0122] Understandably, if the power difference drops below the preset power threshold or the hydrogen storage tank is close to full load, a shutdown command will be issued to stop the operation of the electrolyzer, preventing excessive hydrogen production and energy waste.

[0123] Step S44: When the state of charge (SOC) of the sodium-ion battery and / or the flow battery is lower than a preset SOC threshold, calculate the hydrogen energy replenishment power value based on the current compensation power of the sodium-ion battery and the flow battery.

[0124] It should be noted that the preset state of charge threshold refers to the lower limit of battery capacity set by the system (e.g., 20%). When the SOC of the sodium-ion battery and / or flow battery falls below this value, the hydrogen replenishment mechanism is triggered to prevent over-discharge of the battery. The current compensation power refers to the sum of the actual power output of the sodium-ion battery and the flow battery, used to measure the power shortfall currently being handled by the energy storage system. The hydrogen replenishment power value refers to the power that the hydrogen fuel cell needs to provide; its value is equal to the current compensation power, used to completely replace the battery output, allowing the battery to exit the discharge phase and enter the charging recovery phase.

[0125] Understandably, the central management unit calculates the overall SOC by weighting the SOC of the sodium-ion battery and the flow battery according to their capacities. When the overall value is lower than the preset state of charge threshold, the current output power of the two batteries is immediately added together to obtain the current compensation power. This value is then directly assigned as the hydrogen energy replenishment power value, which is used to start the fuel cell and set its output power, so that the battery can stop discharging and enter the recovery charging phase.

[0126] Step S45: Set the hydrogen energy replenishment power value as the output power value, and send a start command containing the output power value to the hydrogen fuel cell to complete the hybrid energy storage collaborative control.

[0127] It should be noted that the output power value refers to the value that is directly equal to the hydrogen energy replenishment power value and is written into the hydrogen fuel cell power setting register. This value is used to command the fuel cell to output electrical energy to the bus at this kilowatt level, thus replacing the battery to cover the power gap.

[0128] Understandably, firstly, the central management unit assigns the newly calculated hydrogen replenishment power value to the output power value (e.g., 10kW), and sends the start flag set to 1 along with this value as a 16-bit data frame to the alkaline fuel cell via CAN. Upon receiving the data, the fuel cell immediately adjusts the hydrogen valve and blower according to P = output power value × 100% / 10kW, causing the stack to output the corresponding current within 1 second, quickly filling the bus power gap. Secondly, after the fuel cell starts outputting power, the central unit simultaneously reduces the reference current of the sodium-ion battery and the flow battery to zero, stopping the batteries from discharging and entering a low-current standby mode to avoid further deep discharge. Finally, the bus voltage and battery SOC are continuously monitored. Once the overall SOC recovers to 30% or the power difference approaches zero, a shutdown flag (e.g., 0x00) and an output power value of 0kW are issued, the fuel cell shuts down, and the battery resumes control of fluctuations, completing the hybrid energy storage collaborative control.

[0129] As an example, before the step of setting the hydrogen energy replenishment power value as the output power value and sending a start command containing the output power value to the hydrogen fuel cell to complete the hybrid energy storage coordinated control, the method further includes: obtaining the rated voltage value of the hydrogen fuel cell; calculating the output current based on the hydrogen energy replenishment power value and the rated voltage value; sending the output current to a bidirectional DC-DC converter so that the bidirectional DC-DC converter generates a duty cycle signal based on the output current and adjusts the output voltage of the hydrogen fuel cell to the bus voltage based on the duty cycle signal; monitoring the hydrogen utilization rate of the hydrogen fuel cell through a hydrogen concentration sensor; and adjusting the opening degree of the hydrogen supply valve based on the hydrogen utilization rate.

[0130] Rated voltage refers to the nominal DC voltage output of the hydrogen fuel cell under rated operating conditions, used for subsequent current calculations and voltage boosting matching. Output current is the current value obtained by dividing the hydrogen replenishment power by the rated voltage; this value is sent to the bidirectional DC-DC converter as the current loop reference. Duty cycle signal is a 0–1 value generated by the bidirectional DC-DC converter based on the error between the output current and the actual current after PI calculation; it is used to control the on-time ratio of the power switch, achieving voltage boosting from the battery voltage to the bus voltage. Hydrogen utilization rate refers to the ratio of the amount of hydrogen actually participating in the reaction to the total amount of hydrogen supplied; it is monitored in real time by a hydrogen concentration sensor and used to assess fuel efficiency. Hydrogen supply valve opening refers to the percentage of opening of the electronically controlled needle valve; the central management unit dynamically adjusts this opening based on hydrogen utilization rate and power demand to ensure sufficient hydrogen flow and avoid waste.

[0131] First, the central management unit reads the rated voltage (e.g., 48V) from the hydrogen fuel cell's memory, divides the hydrogen replenishment power value by this voltage to obtain the output current (e.g., 10kW ÷ 48V ≈ 208A), and writes this current value into the current loop reference register of the bidirectional DC-DC converter via the CAN bus, so that the converter knows the amount of current to be drawn. Second, the converter samples the actual stack current at a 100µs cycle, compares it with the reference value, and then performs proportional-integral calculation to obtain the duty cycle signal. The Q1- is then controlled according to this duty cycle. The Q4 switching sequence boosts the 48V to 380V and adjusts the current in real time to ensure that the power difference is made up instantly, while avoiding current overshoot that could damage the fuel cell stack. Finally, the hydrogen concentration sensor sends back the exhaust hydrogen content every second, and the central unit calculates the hydrogen utilization rate based on this. If it is lower than the preset utilization rate threshold (e.g., 92%), the opening of the hydrogen supply valve is increased proportionally (e.g., +5%), and if it is higher than the preset utilization rate threshold, the opening is decreased (e.g., -3%). This ensures that the fuel cell stack is fully utilized without wasting hydrogen, thus completing the closed-loop coordination of voltage matching and fuel efficiency.

[0132] Please refer to Figure 5 , Figure 5 This is a schematic diagram of the energy management process provided in Embodiment 2 of the hybrid energy storage coordinated control method for DC microgrids according to this application. First, the central management unit of the microgrid performs real-time power calculations to determine if the photovoltaic power is greater than the sum of the load power and the power loss. If so, power is prioritized to the load, and the remaining power is used for hydrogen production in the hydrogen electrolyzer. If the hydrogen storage is not full, the remaining power is also used for charging the energy storage. When the state of charge (SOC) of the energy storage system exceeds 20%, the sodium-ion battery and flow battery will compensate for high-frequency and low-frequency power as needed to stabilize the DC bus voltage. If the photovoltaic power is less than the sum of the load power and the power loss, the central management unit of the microgrid will activate the hydrogen fuel cell and discharge the energy storage to supplement the power. The entire process ensures the stability of the DC bus voltage while optimizing energy use and storage, improving the reliability and economy of the system.

[0133] This embodiment first calculates the sum of load power and loss power to obtain the total power consumption. Then, it calculates the power difference between the photovoltaic power and the total power consumption. When the power difference is greater than a preset power threshold, it indicates that the photovoltaic power is excessive. In this case, the power difference is set as the input power value, and a start command containing this input power value is sent to the hydrogen electrolyzer. This allows the electrolyzer to utilize the excess photovoltaic power to produce hydrogen, preventing the bus voltage from rising due to excess power and improving energy utilization. When the power difference is less than the preset power threshold, it indicates that the photovoltaic power is insufficient. In this case, a stop command is sent to the hydrogen electrolyzer to stop hydrogen production, saving hydrogen resources and reducing unnecessary energy consumption. When the state of charge (SOC) value of the sodium-ion battery and / or flow battery is lower than the preset SOC threshold, it indicates that the energy storage battery has insufficient power. In this case, the hydrogen energy replenishment power value is calculated based on the current compensation power of the sodium-ion battery and flow battery, and this value is set as the output power value. A start command containing the output power value is sent to the hydrogen fuel cell, allowing the hydrogen fuel cell to output power to supplement the bus power gap, preventing over-discharge of the battery, extending battery life, and ensuring stable bus voltage, thus completing the hybrid energy storage coordinated control.

[0134] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the hybrid energy storage coordinated control method of DC microgrids in this application. Any simple modifications based on this technical concept are within the protection scope of this application.

[0135] This application also provides a hybrid energy storage coordinated control device for a DC microgrid; please refer to [reference needed]. Figure 6 The hybrid energy storage collaborative control device for the DC microgrid includes:

[0136] Calculation module 10 is used to calculate the total compensation current based on the DC bus voltage, the preset bus voltage reference value, and the voltage proportional-integral controller.

[0137] The filtering module 20 is used to decompose the total compensation current into high-frequency components and low-frequency components through a high-pass filter, and use the high-frequency components as the reference current for the sodium-ion battery and the low-frequency components as the reference current for the flow battery.

[0138] The hybrid energy storage module 30 is used to send the sodium-ion battery reference current to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current, and to send the flow battery reference current to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current.

[0139] The hydrogen energy conversion module 40 is used to send control commands, including start / stop status and power setpoints, to the hydrogen electrolyzer and hydrogen fuel cell based on the state of charge values ​​of the sodium-ion battery and the flow battery, according to the photovoltaic power, load power and loss power, to complete the hybrid energy storage coordinated control.

[0140] The hybrid energy storage collaborative control device for DC microgrids provided in this application, employing the hybrid energy storage collaborative control method for DC microgrids in the above embodiments, can solve the technical problem of how to improve the voltage stability of photovoltaic DC microgrids and extend the lifespan of energy storage systems. Compared with the prior art, the beneficial effects of the hybrid energy storage collaborative control device for DC microgrids provided in this application are the same as those of the hybrid energy storage collaborative control method for DC microgrids provided in the above embodiments, and other technical features in the hybrid energy storage collaborative control device for DC microgrids are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0141] This application provides a hybrid energy storage collaborative control device for a DC microgrid. The hybrid energy storage collaborative control device for a DC microgrid includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the hybrid energy storage collaborative control method for a DC microgrid in the above embodiment 1.

[0142] The following is for reference. Figure 7 This document illustrates a structural schematic diagram of a hybrid energy storage and collaborative control device suitable for implementing the embodiments of this application's DC microgrid. The hybrid energy storage and collaborative control device for the DC microgrid in the embodiments of this application may include, but is not limited to, mobile terminals such as mobile phones, laptops, digital radio receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Description), PMPs (Portable Media Players), vehicle terminals (e.g., vehicle navigation terminals), and fixed terminals such as digital TVs and desktop computers. Figure 7 The hybrid energy storage and collaborative control device for DC microgrids shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments in this application.

[0143] like Figure 7As shown, the hybrid energy storage collaborative control device for a DC microgrid may include a processing unit 1001 (e.g., a central processing unit, a graphics processor, etc.), which can perform various appropriate actions and processes according to programs stored in ROM (Read Only Memory) 1002 or programs loaded from storage device 1003 into RAM (Random Access Memory) 1004. RAM 1004 also stores various programs and data required for the operation of the hybrid energy storage collaborative control device for the DC microgrid. The processing unit 1001, ROM 1002, and RAM 1004 are interconnected via bus 1005. Input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to I / O interface 1006: input devices 1007 including, for example, touchscreens, touchpads, keyboards, mice, image sensors, microphones, accelerometers, gyroscopes, etc.; output devices 1008 including, for example, LCDs (Liquid Crystal Displays), speakers, vibrators, etc.; storage devices 1003 including, for example, magnetic tapes, hard disks, etc.; and communication devices 1009. Communication device 1009 allows the hybrid energy storage co-control device of the DC microgrid to communicate wirelessly or wiredly with other devices to exchange data. Although a hybrid energy storage co-control device of a DC microgrid with various systems is shown in the figure, it should be understood that it is not required to implement or possess all the systems shown. More or fewer systems can be implemented alternatively.

[0144] Specifically, according to the embodiments disclosed in this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device, or installed from storage device 1003, or installed from ROM 1002. When the computer program is executed by processing device 1001, it performs the functions defined in the methods of the embodiments disclosed in this application.

[0145] The hybrid energy storage collaborative control device for DC microgrids provided in this application, employing the hybrid energy storage collaborative control method for DC microgrids in the above embodiments, can solve the technical problem of how to improve the voltage stability of photovoltaic DC microgrids and extend the lifespan of energy storage systems. Compared with the prior art, the beneficial effects of the hybrid energy storage collaborative control device for DC microgrids provided in this application are the same as the beneficial effects of the hybrid energy storage collaborative control method for DC microgrids provided in the above embodiments, and other technical features in this hybrid energy storage collaborative control device for DC microgrids are the same as those disclosed in the previous embodiment method, and will not be repeated here.

[0146] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0147] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0148] This application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon, which are used to execute the hybrid energy storage coordinated control method for DC microgrids in the above embodiments.

[0149] The computer-readable storage medium provided in this application may be, for example, a USB flash drive, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, RAM (Random Access Memory), ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory or Flash Memory), optical fibers, CD-ROM (CD-Read Only Memory), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable storage medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0150] The aforementioned computer-readable storage medium may be included in the hybrid energy storage and collaborative control device of the DC microgrid; or it may exist independently and not be installed in the hybrid energy storage and collaborative control device of the DC microgrid.

[0151] The aforementioned computer-readable storage medium carries one or more programs. When these programs are executed by the hybrid energy storage collaborative control device of the DC microgrid, the hybrid energy storage collaborative control device of the DC microgrid performs the following actions: calculates the total compensation current based on the DC bus voltage, a preset bus voltage reference value, and a voltage proportional-integral controller; decomposes the total compensation current into high-frequency and low-frequency components using a high-pass filter, using the high-frequency component as the reference current for the sodium-ion battery and the low-frequency component as the reference current for the flow battery; sends the sodium-ion battery reference current to the sodium-ion battery converter, so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current, and sends the flow battery reference current to the flow battery converter, so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current; based on the state of charge values ​​of the sodium-ion battery and the flow battery, and according to the photovoltaic power, load power, and loss power, sends control commands containing start / stop status and power setpoints to the hydrogen electrolyzer and hydrogen fuel cell, thereby completing the hybrid energy storage collaborative control.

[0152] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, as well as conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including LAN (Local Area Network) or WAN (Wide Area Network)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0153] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0154] The modules described in the embodiments of this application can be implemented in software or hardware. The names of the modules do not necessarily limit the functionality of the unit itself.

[0155] The readable storage medium provided in this application is a computer-readable storage medium that stores computer-readable program instructions (i.e., a computer program) for executing the hybrid energy storage coordinated control method for the DC microgrid described above. This method can solve the technical problem of how to improve the voltage stability of the photovoltaic DC microgrid and extend the lifespan of the energy storage system. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in this application are the same as those of the hybrid energy storage coordinated control method for the DC microgrid provided in the above embodiments, and will not be repeated here.

[0156] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the hybrid energy storage coordinated control method for DC microgrids as described above.

[0157] The computer program product provided in this application can solve the technical problem of how to improve the voltage stability of photovoltaic DC microgrids and extend the life of energy storage systems. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as the beneficial effects of the hybrid energy storage coordinated control method for DC microgrids provided in the above embodiments, and will not be repeated here.

[0158] The above description is only a part of the embodiments of this application and does not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A hybrid energy storage coordinated control method for a DC microgrid, characterized in that, The method includes: The total compensation current is calculated based on the DC bus voltage, the preset bus voltage reference value, and the voltage proportional-integral controller. The total compensation current is decomposed into high-frequency and low-frequency components using a high-pass filter, and the high-frequency component is used as the reference current for the sodium-ion battery, while the low-frequency component is used as the reference current for the flow battery. The sodium-ion battery reference current is sent to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current. The flow battery reference current is also sent to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current. Based on the state of charge (SOC) values ​​of the sodium-ion battery and the flow battery, and according to the photovoltaic power, load power, and power loss, control commands including start / stop status and power setpoints are sent to the hydrogen electrolyzer and the hydrogen fuel cell to complete the hybrid energy storage coordinated control. The steps of sending control commands including start / stop status and power setpoints to the hydrogen electrolyzer and the hydrogen fuel cell based on the SOC values ​​of the sodium-ion battery and the flow battery, and according to the photovoltaic power, load power, and power loss, to complete the hybrid energy storage coordinated control include: Calculate the total power consumption based on the load power and power loss, and calculate the power difference between the photovoltaic power and the total power consumption. When the power difference is greater than the preset power threshold, the power difference is set as the input power value, and a start command containing the input power value is sent to the hydrogen electrolyzer. When the power difference is less than the preset power threshold, a stop command is sent to the hydrogen electrolyzer. When the state of charge of the sodium-ion battery and / or the flow battery is lower than the preset state of charge threshold, the hydrogen energy replenishment power value is calculated based on the current compensation power of the sodium-ion battery and the flow battery. The hydrogen energy replenishment power value is set as the output power value, and a start command containing the output power value is sent to the hydrogen fuel cell to complete the hybrid energy storage collaborative control. Before the step of setting the hydrogen energy replenishment power value as the output power value and sending a start command containing the output power value to the hydrogen fuel cell to complete the hybrid energy storage coordinated control, the method further includes: Obtain the rated voltage value of the hydrogen fuel cell; Calculate the output current based on the hydrogen energy replenishment power value and the rated voltage value; The output current is sent to a bidirectional DC-DC converter, which generates a duty cycle signal based on the output current and adjusts the output voltage of the hydrogen fuel cell to the bus voltage based on the duty cycle signal. The hydrogen utilization rate of the hydrogen fuel cell is monitored by a hydrogen concentration sensor; Adjust the opening of the hydrogen supply valve according to the hydrogen utilization rate.

2. The method as described in claim 1, characterized in that, The step of decomposing the total compensation current into high-frequency and low-frequency components using a high-pass filter, and using the high-frequency component as the reference current for the sodium-ion battery and the low-frequency component as the reference current for the flow battery includes: Set the cutoff frequency of the high-pass filter; The high-pass filter extracts a signal higher than the cutoff frequency from the total compensation current as a high-frequency component. The low-frequency component is obtained by subtracting the high-frequency component from the total compensation current; The high-frequency component is used as the reference current for the sodium-ion battery. The low-frequency component is used as the reference current for the flow battery.

3. The method as described in claim 1, characterized in that, The step of calculating the total compensation current based on the DC bus voltage, the preset bus voltage reference value, and the voltage proportional-integral controller includes: Collect DC bus voltage; Calculate the deviation between the DC bus voltage and the preset bus voltage reference value; The deviation is proportionally calculated using the proportional term coefficient of the voltage proportional-integral controller to obtain the proportional calculation result; The deviation is integrated using the integral term coefficient of the voltage proportional-integral controller to obtain the integral result; The total compensation current is generated by superimposing the proportional calculation result and the integral calculation result.

4. The method as described in claim 1, characterized in that, The step of sending the sodium-ion battery reference current to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current includes: Set the current loop bandwidth of the sodium-ion battery to a first preset ratio of the switching frequency. Configure the first proportional-integral parameter to the first current loop controller of the sodium-ion battery converter; The reference current of the sodium-ion battery is sent to the sodium-ion battery converter, so that the sodium-ion battery converter generates a first duty cycle control signal according to the first current loop controller, and adjusts the switching timing of the bidirectional DC-DC converter according to the first duty cycle control signal, thereby controlling the charging and discharging current of the sodium-ion battery.

5. The method as described in claim 1, characterized in that, The step of sending the reference current of the flow battery to the flow battery converter, so that the flow battery converter controls the charging and discharging current of the flow battery according to the reference current of the flow battery, includes: Set the current loop bandwidth of the flow battery to a second preset ratio of the switching frequency; Configure the second proportional-integral parameter to the second current loop controller of the flow battery converter; The reference current of the flow battery is sent to the flow battery converter, so that the flow battery converter generates a second duty cycle control signal according to the second current loop controller, and adjusts the switching timing of the bidirectional DC-DC converter according to the second duty cycle control signal, thereby controlling the charging and discharging current of the flow battery.

6. A hybrid energy storage collaborative control device for a DC microgrid, characterized in that, The device includes: The calculation module is used to calculate the total compensation current based on the DC bus voltage, the preset bus voltage reference value, and the voltage proportional-integral controller. The filtering module is used to decompose the total compensation current into high-frequency components and low-frequency components through a high-pass filter, and use the high-frequency components as the reference current for the sodium-ion battery and the low-frequency components as the reference current for the flow battery. A hybrid energy storage module is used to send the sodium-ion battery reference current to the sodium-ion battery converter so that the sodium-ion battery converter controls the charging and discharging current of the sodium-ion battery according to the sodium-ion battery reference current, and to send the flow battery reference current to the flow battery converter so that the flow battery converter controls the charging and discharging current of the flow battery according to the flow battery reference current. A hydrogen energy conversion module is used to send control commands containing start / stop status and power setpoints to a hydrogen electrolyzer and a hydrogen fuel cell based on the state of charge (SOC) values ​​of the sodium-ion battery and the flow battery, according to photovoltaic power, load power, and power loss, to complete the hybrid energy storage coordinated control. The steps of sending control commands containing start / stop status and power setpoints to the hydrogen electrolyzer and hydrogen fuel cell based on the SOC values ​​of the sodium-ion battery and the flow battery, according to photovoltaic power, load power, and power loss, to complete the hybrid energy storage coordinated control include: calculating the total power consumption based on the load power and power loss, and calculating the power difference between the photovoltaic power and the total power consumption; when the power difference is greater than a preset power threshold, setting the power difference as the input power value, and sending a start command containing the input power value to the hydrogen electrolyzer; when the power difference is less than the preset power threshold, sending a stop command to the hydrogen electrolyzer; and when the sodium-ion battery and / or the flow battery... When the state of charge (SOC) value of the fuel cell is lower than a preset SOC threshold, the hydrogen energy replenishment power value is calculated based on the current compensation power of the sodium-ion battery and the flow battery; the hydrogen energy replenishment power value is set as the output power value, and a start command containing the output power value is sent to the hydrogen fuel cell to complete the hybrid energy storage coordinated control; before the step of setting the hydrogen energy replenishment power value as the output power value and sending a start command containing the output power value to the hydrogen fuel cell to complete the hybrid energy storage coordinated control, the method further includes: obtaining the rated voltage value of the hydrogen fuel cell; calculating the output current based on the hydrogen energy replenishment power value and the rated voltage value; sending the output current to a bidirectional DC-DC converter so that the bidirectional DC-DC converter generates a duty cycle signal based on the output current, and adjusts the output voltage of the hydrogen fuel cell to the bus voltage based on the duty cycle signal; monitoring the hydrogen utilization rate of the hydrogen fuel cell through a hydrogen concentration sensor; and adjusting the opening of the hydrogen supply valve based on the hydrogen utilization rate.

7. A hybrid energy storage and collaborative control device for a DC microgrid, characterized in that, The device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the hybrid energy storage coordinated control method for a DC microgrid as described in any one of claims 1 to 5.

8. A storage medium, characterized in that, The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, it implements the steps of the hybrid energy storage coordinated control method for DC microgrids as described in any one of claims 1 to 5.

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