An energy management system for a drone fuel cell hybrid power system

Abstract

The application discloses an energy management system of a UAV fuel cell hybrid power system, comprising a fuel cell group, a lithium battery group and a bidirectional DC-DC power supply controller; the fuel cell group is connected to a DC bus at a load end through the bidirectional DC-DC power supply controller, the lithium battery group is connected in parallel to the DC bus, the bidirectional DC-DC power supply controller collects bus voltage, fuel cell group output voltage and current, initial SOE, minimum SOE, thermodynamic theory output voltage and load power, solves real-time SOE of the fuel cell, and completes multi-working-condition energy management and control through multi-parameter threshold comparison. The application can directly manage and control fuel cell output power and SOE by relying on the bidirectional DC-DC power supply controller, without an additional energy management controller; the lithium battery works adaptively with the bus voltage, BMS control is saved, and the problems of cooperation obstacles and data delay caused by non-uniform interfaces and protocols of BMS and FCS are avoided.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) energy system technology, specifically to an energy management system for a UAV fuel cell hybrid power system. Background Technology

[0002] With the booming development of the low-altitude economy, drones are increasingly used in fields such as power line inspection, agricultural plant protection, environmental monitoring, and emergency rescue. However, endurance and payload remain the core bottlenecks restricting their large-scale application. Traditional single power sources have obvious drawbacks: lithium batteries have limited energy density, resulting in short endurance; fuel cell systems have slow dynamic response and low power density, failing to meet instantaneous high power demands. Therefore, hydrogen-lithium hybrid energy systems, through the synergy of dual power sources, achieve complementary advantages and have become a key technological path to solve the above bottlenecks.

[0003] Currently, proton exchange membrane fuel cells (PEMFCs) are the mainstream fuel cells for drones, offering advantages such as high energy density, high conversion efficiency, rapid refueling, and environmental friendliness. Lithium-ion batteries are technologically mature, cost-controllable, and have stable performance. The core approach combines ternary lithium (high energy density) and lithium iron phosphate (high safety and long lifespan), making them the mainstream choice for small drone power systems. However, due to the significant differences in the output dynamic characteristics of fuel cells and lithium batteries, corresponding energy management controllers and strategies are needed to address the various complex operating conditions during actual drone flight. This allows for the full utilization of the different characteristics of each power source, achieving optimal overall system performance in terms of energy efficiency, component lifespan, and overall cost.

[0004] Current relevant energy management technologies include Figure 1 As shown, sensors collect data such as voltage, current, and hydrogen consumption at the load-side bus, which are then transmitted to the energy management controller. After calculation and decision-making, the controller controls the DC-DC power converters connected to the fuel cell stack and lithium battery stack ports via signal buses to achieve energy management and regulation of the hybrid energy system. However, in practical applications, an additional energy management controller is required in addition to the fuel cell stack, lithium battery stack, and DC-DC power converter. Only through the energy management controller can the battery management system (BMS) and fuel cell control system (FCS) be controlled. However, there are barriers such as inconsistent communication protocols and data interaction delays between the battery management system (BMS) and fuel cell control system (FCS), which prevent key parameters such as battery SOE, stack output power, and hydrogen consumption from being shared in real time, making it difficult to accurately manage and regulate the hybrid energy system. Summary of the Invention

[0005] The purpose of this invention is to provide an energy management system for a fuel cell hybrid power system for unmanned aerial vehicles (UAVs) to solve the technical problems mentioned in the background art.

[0006] The technical solution of this invention is: An energy management system for an unmanned aerial vehicle (UAV) fuel cell hybrid power system includes a fuel cell stack, a lithium battery pack, and a bidirectional DC-DC power controller. The fuel cell stack is connected to the DC bus of the load end via the bidirectional DC-DC power controller. The lithium battery pack is connected in parallel to the DC bus of the load end. The bidirectional DC-DC power controller is used to acquire the bus voltage value, the output voltage value of the fuel cell stack, the output current value of the fuel cell stack, the initial SOE value of the fuel cell stack before flight, the minimum SOE value of the fuel cell stack, the thermodynamic theoretical output voltage value of the fuel cell stack, and the load power of the fuel cell, and to determine the real-time SOE value of the fuel cell stack. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack and the bus voltage value is greater than that of the bidirectional DC-DC power controller... When the output voltage is at the regulated value, the fuel cell stack is controlled not to output, and the lithium battery stack supplies power to the load side. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack, the bus voltage value is less than or equal to the regulated output voltage value of the bidirectional DC-DC power controller, and the load power is less than the optimal output power of the fuel cell stack, the fuel cell stack is controlled to supply power to the load while simultaneously charging the lithium battery stack through the bus. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack, the bus voltage value is less than or equal to the regulated output voltage value of the bidirectional DC-DC power controller, and the load power is greater than or equal to the optimal output power of the fuel cell stack, the output power of the fuel cell stack is controlled to be stabilized at a constant value, and the fuel cell stack supplies power to the load according to the optimal power value output, while the lithium battery stack is in a discharging state and simultaneously supplies power to the load.

[0007] Preferably, as a further improvement of the present invention, the optimal output power of the fuel cell stack is set based on the rated power of the fuel cell, and the optimal output power of the fuel cell stack is 0.4 to 0.6 times the rated power of the fuel cell.

[0008] Preferably, as a further improvement of the present invention, the optimal output power of the fuel cell stack is 0.5 times the rated power of the fuel cell.

[0009] Preferably, as a further improvement of the present invention, the step of determining the real-time SOE value of the fuel cell stack is as follows: First, determine the instantaneous output power of the fuel cell stack according to the following formula; P.FC.out(t)=Uin(t)*Iin(t); In the formula, P.FC.out(t) is the instantaneous output power of the fuel cell stack, Uin(t) is the output voltage of the fuel cell stack, and Iin(t) is the output current of the fuel cell stack. Then, the output loss value of the fuel cell stack is determined based on the following formula: P.FC.loss(t)=Iin(t)∗(Uo.FC−Uin(t)); In the formula, P.FC.loss(t) is the output loss value of the fuel cell stack, Iin(t) is the output current value of the fuel cell stack, Uo.FC is the thermodynamic theoretical output voltage value of the fuel cell stack, and Uin(t) is the output voltage value of the fuel cell stack. Finally, the real-time SOE value of the fuel cell stack is determined by the following formula; ; In the formula, This represents the real-time SOE value of the fuel cell stack. E.FC.total represents the initial SOE value of the fuel cell stack, P.FC.out(t) represents the instantaneous output power of the fuel cell stack, and P.FC.loss(t) represents the output loss value of the fuel cell stack.

[0010] Preferably, as a further improvement of the present invention, when the bidirectional DC-DC power controller is in constant power mode, the bus voltage value changes with the change of the terminal voltage during the discharge of the lithium battery pack, and the lithium battery pack is in the difference between the discharge supplement load power and the optimal output power of the fuel cell pack.

[0011] Compared with the prior art, the beneficial effects of the present invention are: By integrating a sampling and calculation module within the bidirectional DC-DC power controller, real-time control of the fuel cell stack's output power and SOE value can be achieved directly without relying on an additional energy management controller. Furthermore, the lithium battery stack, acting as a passive response, adjusts its operating state in accordance with changes in the bus voltage, eliminating the need for a BMS to control the lithium battery stack. This avoids the coordination barriers and data delays caused by the inconsistency in interfaces and communication protocols between the BMS and FCS, effectively preventing issues such as poor multi-source coordination and low stability. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of an existing energy management technology solution.

[0013] Figure 2 This is a schematic diagram of the energy management system of the UAV fuel cell hybrid power system of the present invention.

[0014] Figure 3 This is a control flowchart of the bidirectional DC-DC power controller of the present invention.

[0015] Figure 4 This is a schematic diagram of the system state and curves under the fitted load power of the present invention.

[0016] Figure 5 This is a schematic diagram of the load power curve of the present invention.

[0017] Figure 6 This is a schematic diagram of the output power curve of the fuel cell stack of the present invention.

[0018] Figure 7 This is a schematic diagram of the output power curve of the lithium battery pack of the present invention. Detailed Implementation

[0019] The following is combined with Figures 2-7 The specific embodiments of the present invention will be described in detail below. In the description of the invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0020] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of the invention, unless otherwise stated, "a plurality of" means two or more.

[0021] Example 1 like Figure 2 As shown, this embodiment of the invention provides an energy management system for a UAV fuel cell hybrid power system, including a fuel cell stack, a bidirectional DC-DC power controller, a lithium battery pack, and a DC bus; the fuel cell stack is connected to the DC bus at the load end through the bidirectional DC-DC power controller.

[0022] The bidirectional DC-DC power controller is the core intelligent unit of this system. Unlike traditional energy management systems, the bidirectional DC-DC power controller of this invention highly integrates a sampling unit, a communication unit, a processing unit, and a decision control unit. The sampling unit includes voltage and current sampling components, and the decision control unit includes a comparison module and a control module. This enables the controller to possess the following capabilities:

[0023] Real-time data acquisition: The voltage and current sampling components in the sampling unit can acquire the voltage (i.e., fuel cell stack terminal voltage) and current (i.e., fuel cell stack charging and discharging current) on the input side, as well as the voltage (i.e., load DC bus voltage) on the output side in real time. The communication unit adopts a preset communication protocol (such as CAN, UART, Bluetooth, SPI) to achieve bidirectional data interaction; on the one hand, it receives control signals from external devices (such as output voltage setting and power limiting); on the other hand, it reads the initial SOE value of the fuel cell stack before flight, the minimum SOE value of the fuel cell stack, the thermodynamic theoretical output voltage value of the fuel cell stack, and the load power of the fuel cell from the flight control module of the UAV through remote communication. Online state calculation: The processing unit processes the acquired initial SOE value, output voltage value, output current value, and thermodynamic theoretical output voltage value of the fuel cell stack to obtain the real-time SOE value of the fuel cell stack.

[0024] Autonomous Decision-Making and Control: The comparison and control modules built into the control unit autonomously decide which operating mode the bidirectional DC-DC power controller should enter based on the preset control strategy and the real-time calculated system state. By adjusting the voltage and power on its output side, it achieves precise management of the output power of the fuel cell stack and the lithium battery stack. When making a decision, it compares the real-time SOE value of the fuel cell stack with the minimum SOE value of the fuel cell stack, and the real-time bus voltage value with the voltage regulation value of the bidirectional DC-DC power controller. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack and the bus voltage value is greater than the output voltage regulation value of the bidirectional DC-DC power controller, the fuel cell stack is controlled to not output, and the lithium battery pack supplies power to the load side. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack, the bus voltage value is less than or equal to the output voltage regulation value of the bidirectional DC-DC power controller, and the load power is less than the optimal output power of the fuel cell stack, the fuel cell stack is controlled to supply power to the load while charging the lithium battery stack through the bus. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack, the bus voltage value is less than or equal to the output voltage regulation value of the bidirectional DC-DC power controller, and the load power is greater than or equal to the optimal output power of the fuel cell stack, the output power of the fuel cell stack is controlled to be stabilized at a constant value, and the fuel cell stack supplies power to the load according to the optimal power value output. The lithium battery stack is in a discharging state and supplies power to the load at the same time.

[0025] In this embodiment, the fuel cell stack is used as the main power source to provide steady-state energy during the flight of the UAV, while the lithium battery stack is used as an auxiliary power source to supplement the power of the fuel cell stack and ensure the maneuverability of the UAV during flight.

[0026] In the hybrid power system, the overall strategy of "fuel cell stack base load + lithium battery stack peak shaving" is adopted. During long-duration flight conditions such as cruise, with gradual changes in flight attitude, the total energy consumption is high but the instantaneous load is low. In this case, the fuel cell stack dominates the power supply to fully utilize its high energy density. Conversely, during short-duration flight conditions such as takeoff, landing, and maneuvering, with high instantaneous load but low total energy consumption, the system switches to lithium battery stack power supply, leveraging its high power density to ensure the UAV's maneuverability and flight reliability. Simultaneously, during low-power conditions such as cruise, the fuel cell stack can charge the lithium battery stack, promptly compensating for the energy consumption of the lithium battery stack in the previous condition, ensuring that the UAV still has sufficient power response and operational reliability under high-power conditions.

[0027] During operation, the output power of the fuel cell stack and lithium battery stack is adjusted by controlling the voltage level of the bidirectional DC-DC power controller. Since the lithium battery stack is directly connected in parallel to the DC bus, it passively responds to changes in the output voltage. Therefore, it is not necessary to use a BMS to control the lithium battery stack, thus avoiding the coordination barriers and data delays caused by the inconsistency of interfaces and communication protocols between the BMS and FCS. This effectively avoids the problems of poor multi-source coordination and low stability.

[0028] The specific working principle and steps of this invention are as follows: S1, System Initialization This step is the system initialization phase. The bidirectional DC-DC power controller acquires the initial state parameters of the fuel cell stack and the system, and sets the optimal output power value and the regulated output voltage value of the bidirectional DC-DC power controller according to the power level of the system and the fuel cell stack.

[0029] Specifically, the initial SOE value, minimum SOE value, thermodynamic output voltage value, and load power of the fuel cell stack are read from the flight control module of the UAV through the communication unit. The bus voltage value and output voltage value of the fuel cell stack are obtained in real time through the sampling unit. The output current value of the fuel cell stack is obtained in real time through the current sampling unit. The optimal output power of the fuel cell stack is set based on the rated power of the fuel cell. The output voltage regulation value of the bidirectional DC-DC power controller is preset based on the system setpoint. The optimal output power of the fuel cell stack is set as follows: the efficiency of the fuel cell stack = electrical energy output / hydrogen chemical energy. The optimal output power is the operating point that maximizes the overall efficiency, extends the lifespan, and minimizes the overall energy consumption of the fuel cell stack. It generally occurs between 0.4 and 0.6 times the rated power. This invention adopts a general engineering value, that is, 0.5 times the rated power of the fuel cell is set as the optimal output power value of the fuel cell stack.

[0030] S2, System Parameter Status Update The bidirectional DC-DC power controller collects the output voltage, output current and bus voltage values ​​of the fuel cell stack in real time through the sampling unit through the internal processing control unit, and calculates and processes the theoretical output voltage value of the fuel cell stack read by the communication unit for the generation of subsequent mode judgment conditions. S21. Calculation of fuel cell stack output power: Based on the voltage and current at the input and output terminals of the bidirectional DC-DC power controller, the power value at the input side of the bidirectional DC-DC power controller (i.e., the output power of the fuel cell stack) can be calculated using the following formula: , In the formula, P.FC.out(t) is the instantaneous output power of the fuel cell stack, Uin(t) is the output voltage of the fuel cell stack, corresponding to the input voltage of the bidirectional DC-DC power controller, and Iin(t) is the output current of the fuel cell stack, corresponding to the input current of the bidirectional DC-DC power controller.

[0031] S22. Calculation of fuel cell stack output loss: Under different current loads, due to unavoidable losses (activation loss, ohmic loss, concentration loss), the actual output voltage of the fuel cell stack decreases non-linearly with increasing load current, always falling below the thermodynamically theoretical output voltage. Therefore, the output power loss of the fuel cell stack can be calculated using the following formula: the product of the fuel cell output current and the voltage difference between the two. , In the formula, P.FC.loss(t) is the calculated value of the output loss of the fuel cell stack, Iin(t) is the output current value of the fuel cell stack, corresponding to the input current value of the bidirectional DC-DC power controller, Uin(t) is the output voltage value of the fuel cell stack, corresponding to the input voltage value of the bidirectional DC-DC power controller, and Uo.FC is the thermodynamic theoretical output voltage of the fuel cell stack, which is read from the flight control module using communication transmission.

[0032] S23. Calculation of SOE value for fuel cell stacks: The initial SOE value of the fuel cell stack, SOE.FC.int, is read from the flight control module using communication transmission. Subsequently, based on the change in output power, the real-time SOE value SOE.FC(t) under the working state of the fuel cell stack is calculated and updated in real time using the following formula; , In the formula, E.FC.total represents the initial SOE value of the fuel cell stack, P.FC.out(t) represents the instantaneous output power of the fuel cell stack, and P.FC.loss(t) represents the output loss value of the fuel cell stack.

[0033] S3, bidirectional DC-DC power controller operating mode switching: When the comparator detects that the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack, the control module in the bidirectional DC-DC power controller further switches to sleep mode, load power mode and constant power mode respectively to control the operation of the fuel cell stack based on the relationship between the real-time bus voltage change detected by the comparator and the voltage regulation value, as well as the relationship between the output power change of the fuel cell stack and the optimal output power. The lithium battery responds passively.

[0034] The specific judgment conditions for each mode are as follows: Sleep Mode: When the bus voltage Ubus(t) > the regulated output voltage U.st of the bidirectional DC-DC power controller, this occurs when the load is low and the lithium battery is nearly fully charged. At this time, the overall system voltage demand is low, and the high open-circuit voltage of the lithium battery forces the bus voltage to remain high. The bidirectional DC-DC power controller reverse-cuts off, blocking the forward output path and locking the reverse cutoff. The fuel cell stops outputting power, and the bidirectional DC-DC power controller enters sleep mode, achieving power isolation from the bus. All loads are drawn from the load devices on the bus. Since the fuel cell no longer provides energy, the entire load power consumption is borne by the energy storage on the bus side, causing the bus voltage to drop. When the bus voltage drops below the current open-circuit voltage of the lithium battery, a natural voltage difference is formed in the parallel circuit. Based on the current sharing characteristics of the parallel power supply, the lithium battery passively establishes a discharge circuit without additional control commands, automatically outputting current to compensate for the load power consumption.

[0035] Load power mode: When the bus voltage Ubus(t) ≤ the regulated output voltage U.st of the bidirectional DC-DC power controller and the load power P.load(t) < the optimal output power P.FC.opt of the fuel cell stack, it indicates that the bus voltage is lower than the set value, and the system needs energy injection. The load demand is small, far below the fuel cell's most efficient operating range. The bidirectional DC-DC power controller is forward-biased, outputting constant voltage, and operating in load power mode, stabilizing the output voltage at the set regulated value. Simultaneously, it commands the fuel cell to output only the power just sufficient to meet the load requirements. At this time, since the fuel cell's output power has a surplus in addition to supplying the load, this excess energy will raise the bus voltage. Once the bus voltage exceeds the current terminal voltage of the lithium battery, the lithium battery passively begins charging, absorbing this excess energy.

[0036] Constant Power Mode: When the bus voltage Ubus(t) ≤ the regulated output voltage U.st of the bidirectional DC-DC power controller, and the load power P.load(t) ≥ the optimal output power P.FC.opt of the fuel cell stack, it means that the load demand is extremely high. The bidirectional DC-DC power controller is forward-biased, but it no longer operates in constant voltage mode, but in constant power mode. At this time, the output power P.FC.out(t) of the fuel cell stack is stabilized at a constant value P.FC.opt, outputting at the optimal output power of the fuel cell stack. The output voltage Uout(t) of the bidirectional DC-DC power controller (i.e., the bus voltage Ubus(t)) changes with the terminal voltage of the lithium battery stack during discharge. Since the output power of the fuel cell is less than the power required by the load, this deficit will pull down the bus voltage. Once the bus voltage is lower than the terminal voltage of the lithium battery, the lithium battery stack is in a discharge state, making up the difference between the load power P.load and the optimal output power P.FC.opt of the fuel cell stack. To avoid fluctuations in output power causing a jump in the system's operating state, an output power judgment threshold P.Δ is set. When the load power P.load(t) < P.FC.opt - P.Δ, the fuel cell stack exits the constant power mode.

[0037] In summary, the bidirectional DC-DC power controller in this invention enters different operating modes based on the varying bus voltage Ubus(t) and fuel cell stack SOE.FC(t), as well as different load power levels, corresponding to different operating states of the lithium battery pack and fuel cell stack. According to the designed control strategy, under the fitted load power curve, the changes in the states of the lithium battery pack, fuel cell stack, and bus voltage, and the curves are as follows: Figure 4As shown in the figure, U.Li.max is the voltage value of the lithium battery pack at full charge, U.Li.min is the voltage value of the lithium battery pack at its minimum charge state, and U.st is the regulated output voltage value of the bidirectional DC-DC power controller. Since the lithium battery pack is directly connected in parallel to the DC bus, the lithium battery pack voltage curve is the same as the bus voltage curve. SOE.FC.int is the initial state of energy value of the fuel cell pack, and SOE.FC.min is the minimum state of energy value of the fuel cell pack. As can be seen from the figure, due to the effect of the energy management system and control method, the bus voltage changes smoothly overall. There are no problems such as rapid drops or fluctuations during load changes and state switching, ensuring the stable operation of the ESC and flight control systems. Figure 5 The figure shows the fitted output power fluctuation curve of the UAV within one flight cycle, including multiple operating conditions such as climb, cruise, hover, maneuver, and descent. According to the described energy management system and control method, the bidirectional DC-DC power controller operates in different modes, enabling the fuel cell stack to output at its optimal power (P.FC.opt), ensuring the fuel cell stack operates within its highest efficiency range, improving energy utilization. Simultaneously, the overall output is stable and smooth, avoiding the problems of frequent start-stop cycles and long-term load fluctuations in the fuel cell stack. Figure 6 As shown. Figure 7 To assess the working status and output power curves of the lithium battery pack under different operating modes, the energy management system and control method are used to compensate for the power difference of the fuel cell pack when the system output power fluctuates. When the load power is relatively light, the fuel cell pack enters the charging state to replenish energy.

[0038] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. An energy management system for a fuel cell hybrid power system for unmanned aerial vehicles (UAVs), comprising a fuel cell stack and a lithium battery stack, characterized in that, It also includes a bidirectional DC-DC power controller, through which the fuel cell stack is connected to the DC bus of the load end, and the lithium battery pack is connected in parallel to the DC bus of the load end; The bidirectional DC-DC power controller is used to acquire the bus voltage value, the output voltage value of the fuel cell stack, the output current value of the fuel cell stack, the initial SOE value of the fuel cell stack before flight, the minimum SOE value of the fuel cell stack, the thermodynamic theoretical output voltage value of the fuel cell stack, and the load power of the fuel cell. Based on the initial SOE value, the output voltage value, the output current value, and the thermodynamic theoretical output voltage value of the fuel cell stack, the real-time SOE value of the fuel cell stack is determined. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack and the bus voltage value is greater than the output voltage regulation value of the bidirectional DC-DC power controller, the bidirectional DC-DC power controller controls the fuel cell stack to not output, and the lithium battery pack supplies power to the load side. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack, the bus voltage value is less than or equal to the output voltage regulation value of the bidirectional DC-DC power controller, and the load power is less than the optimal output power of the fuel cell stack, the bidirectional DC-DC power controller controls the fuel cell stack to supply power to the load while charging the lithium battery stack through the bus. When the real-time SOE value of the fuel cell stack is greater than or equal to the minimum SOE value of the fuel cell stack, the bus voltage value is less than or equal to the output voltage regulation value of the bidirectional DC-DC power controller, and the load power is greater than or equal to the optimal output power of the fuel cell stack, the bidirectional DC-DC power controller controls the output power of the fuel cell stack to be stable at a constant value, and supplies power to the load according to the optimal power value output by the fuel cell stack, while the lithium battery stack is in a discharging state and simultaneously supplies power to the load.

2. The energy management system for the UAV fuel cell hybrid power system according to claim 1, characterized in that, The optimal output power of the fuel cell stack is set based on the rated power of the fuel cell, and the optimal output power of the fuel cell stack is 0.4 to 0.6 times the rated power of the fuel cell.

3. The energy management system for the UAV fuel cell hybrid power system according to claim 2, characterized in that, The optimal output power of the fuel cell stack is 0.5 times the rated power of the fuel cell.

4. The energy management system for the UAV fuel cell hybrid power system according to claim 1, characterized in that, The steps to determine the real-time SOE value of a fuel cell stack are as follows: First, determine the instantaneous output power of the fuel cell stack according to the following formula; P.FC.out(t)=Uin(t)*Iin(t); In the formula, P.FC.out(t) is the instantaneous output power of the fuel cell stack, Uin(t) is the output voltage of the fuel cell stack, and Iin(t) is the output current of the fuel cell stack. Then, the output loss value of the fuel cell stack is determined based on the following formula: P.FC.loss(t)=Iin(t)∗(Uo.FC−Uin(t)); In the formula, P.FC.loss(t) is the output loss value of the fuel cell stack, Iin(t) is the output current value of the fuel cell stack, Uo.FC is the thermodynamic theoretical output voltage value of the fuel cell stack, and Uin(t) is the output voltage value of the fuel cell stack. Finally, the real-time SOE value of the fuel cell stack is determined by the following formula; ； In the formula, This represents the real-time SOE value of the fuel cell stack. E.FC.total represents the initial SOE value of the fuel cell stack, P.FC.out(t) represents the instantaneous output power of the fuel cell stack, and P.FC.loss(t) represents the output loss value of the fuel cell stack.

5. The energy management system for the UAV fuel cell hybrid power system according to claim 1, characterized in that, When the bidirectional DC-DC power controller is in constant power mode, the bus voltage value changes with the terminal voltage during the discharge of the lithium battery pack, and the lithium battery pack is in the difference between the discharge supplement load power and the optimal output power of the fuel cell pack.

Images