An unmanned aerial vehicle hydrogen fuel cell hybrid power system and a control method thereof

Abstract

The application belongs to the technical field of new energy power, and particularly relates to a hydrogen fuel cell hybrid power system of an unmanned aerial vehicle and a control method thereof. The system comprises a fuel cell stack for providing a reference power supply, power output of which is adjustable; a super capacitor group for outputting a peak current when transient high power demand occurs, and having high power density and fast response characteristics; a lithium iron phosphate battery group for providing an emergency power supply when the fuel cell fails; a dynamic bus controller integrated with a voltage hysteresis comparator and a CAN bus communication module, for controlling energy output of the fuel cell stack, the super capacitor group and the lithium iron phosphate battery group; an LSTM neural network prediction module for predicting future power demand according to flight attitude, meteorological data and historical load curve, and triggering power climbing of the fuel cell in advance; and a Buck-Boost circuit for charging the super capacitor group directly by the fuel cell, which significantly improves power response speed and system stability of the unmanned aerial vehicle in a severe maneuvering state.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy power technology, and particularly relates to a hydrogen fuel cell hybrid power system for an unmanned aerial vehicle based on hydrogen fuel cell-supercapacitor-lithium battery triple energy coordination and a control method thereof. BACKGROUND

[0002] With the continuous development of unmanned aerial vehicle technology, its application range gradually expands from entertainment, photography to logistics transportation, agricultural monitoring, disaster rescue and other fields. Therefore, the requirements for the endurance time, power response speed and system reliability of the unmanned aerial vehicle are also higher and higher. The existing hydrogen fuel cell power system becomes an ideal choice for long endurance flight of the unmanned aerial vehicle due to its high energy density and environmental protection characteristics. However, the hydrogen fuel cell has limitations in power response speed, and usually needs more than 1 second to complete the power response, which is insufficient for the requirements of the unmanned aerial vehicle in the conditions of wind resistance, climbing and sharp turning.

[0003] The traditional solution is to use a lithium battery as an auxiliary power supply to cope with the instantaneous high-power demand. However, the lithium battery will cause rapid life decay under the condition of frequent high-current discharge, and more than 40% of the life decay rate seriously affects the long-term use of the system. In addition, the lithium battery power module occupies about 30% of the weight of the entire power system, increases the self-weight of the unmanned aerial vehicle, and further affects the endurance time. At the same time, the lithium battery in the long-term full charge state will accelerate the aging, reduce the service life, and increase the safety risk of the system. SUMMARY

[0004] Therefore, in view of the pain points of the existing hydrogen fuel cell power system of the unmanned aerial vehicle in response delay, output fluctuation and emergency landing risk, the application provides a hydrogen fuel cell hybrid power system for an unmanned aerial vehicle based on hydrogen fuel cell-supercapacitor-lithium battery triple energy coordination and a control method thereof. By using the high transient response capability of the supercapacitor and the high energy density characteristics of the lithium battery, and through a dynamic bus control algorithm, the efficient cooperation and reliable operation of the system are realized, the power response speed and system stability of the unmanned aerial vehicle in the severe maneuvering state are significantly improved, the service life of the lithium battery is prolonged, the system weight is reduced, the endurance time is increased, and the overall reliability and safety of the system are improved.

[0005] One scheme of the application provides a hydrogen fuel cell hybrid power system for an unmanned aerial vehicle, which comprises:

[0006] a fuel cell stack for providing a reference power supply, and the power output is adjustable;

[0007] a supercapacitor group for outputting peak current in the condition of transient high-power demand, and the supercapacitor group has high power density and fast response characteristics;

[0008] Lithium iron phosphate battery pack for providing emergency power supply when fuel cell fails;

[0009] Dynamic bus controller integrated with voltage hysteresis comparator and CAN bus communication module for controlling energy output of fuel cell stack, super capacitor pack and lithium iron phosphate battery pack;

[0010] LSTM neural network prediction module for predicting future power demand according to flight attitude, meteorological data and historical load curve, and triggering fuel cell power climb in advance;

[0011] Buck-Boost circuit for fuel cell to directly charge super capacitor pack.

[0012] As a further scheme of the present application, the operating voltage range of the fuel cell stack is 48-65V, the rated power is 4kW, and the power climb rate is ≥50% / s.

[0013] As a further scheme of the present application, the super capacitor pack is composed of 24 strings of super capacitors or 2 groups of 12 strings of super capacitors in parallel, with a total capacity ≥40F and an internal resistance <1mΩ, directly connected to a high-voltage bus, with a full pressure of 64.8V to a minimum operating voltage of 44V.

[0014] As a further scheme of the present application, the super capacitor pack adopts a topology of 2 groups of 12 strings in parallel, each group being equipped with an independent voltage equalization circuit, and retaining 50% of the peak output capacity when a single group fails.

[0015] As a further scheme of the present application, the lithium iron phosphate battery pack includes 14 strings, with a nominal voltage of 44.8V and a stored energy ≥100Wh.

[0016] As a further scheme of the present application, the dynamic bus controller is integrated with a voltage hysteresis comparator and a CAN bus communication module, and the response time of the voltage hysteresis comparator is <10μs.

[0017] As a further scheme of the present application, the voltage range of the super capacitor pack and the lithium battery pack naturally covers the 44-65V system requirement, without the need for a DC / DC conversion module.

[0018] As a further scheme of the present application, the dynamic bus controller is configured to:

[0019] a) activate the peak current output of the super capacitor pack within 0.1ms when a >100A step load is detected;

[0020] b) synchronously control the fuel cell stack to linearly ramp up from 30% power to 100% within 2 seconds;

[0021] c) When fuel cell fails, switch to lithium battery pack within 2 seconds for 1400W constant power output for >180 seconds.

[0022] As a further scheme of the present application, the Buck-Boost circuit makes the fuel cell stack bypass the lithium battery pack to directly charge the super capacitor pack, and the lithium battery pack is locked at 80% SOC (44.8V) during flight and automatically discharged to 50% SOC (43.2V) after shutdown.

[0023] As a further scheme of the present application, the dynamic bus controller comprises an LSTM neural network prediction module, which inputs flight attitude, meteorological data and historical load curve, predicts power demand in the next 10 seconds and triggers fuel cell power climb in advance.

[0024] One scheme of the present application also provides a control method based on a UAV hydrogen fuel cell hybrid power system, comprising the following steps:

[0025] The steady load stage is directly powered by the fuel cell stack (≤50A);

[0026] The step load response stage:

[0027] After detecting a current request of >100A, the super capacitor pack is started to discharge within 0.1ms;

[0028] The synchronous instruction makes the fuel cell stack linearly climb from 30% power to 100% within 2 seconds;

[0029] The failure emergency stage:

[0030] T=0-2 seconds: full power output of the super capacitor pack prevents stall;

[0031] T=2-180 seconds: the lithium battery pack takes over the load with 1400W constant power.

[0032] As a further scheme of the present application, an LSTM neural network is used to predict power demand in the next 10 seconds, and fuel cell power climb is triggered in advance to reduce the frequency of intervention of the super capacitor.

[0033] As a further scheme of the present application, a Buck-Boost circuit is used to realize direct charging of the super capacitor pack by the fuel cell, thereby avoiding large current impact on the lithium battery.

[0034] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0035] The application realizes microsecond-level transient response by directly connecting the super capacitor group to the high-voltage bus, the dynamic bus controller controls the smooth transition of the fuel cell power, effectively avoids the overshoot risk caused by the chemical response lag, and covers the 44-65V system voltage through the super capacitor and lithium battery, saves the DC / DC conversion module, sets the Buck-Boost direct charging circuit, directly charges the super capacitor with the fuel cell, avoids the large current impact of the lithium battery, improves the capacitor recharge speed, and reduces the risk of thermal runaway. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and are used to explain the application, and do not constitute a limitation on the application. In the drawings:

[0037] Figure 1 It is a topological graph of a UAV hydrogen fuel cell hybrid power system in an embodiment of the application;

[0038] Figure 2 It is a flowchart of a normal flight mode in a UAV hydrogen fuel cell hybrid power system in an embodiment of the application;

[0039] Figure 3 It is a flowchart of peak load response in a UAV hydrogen fuel cell hybrid power system in an embodiment of the application;

[0040] Figure 4 It is a flowchart of fuel cell failure emergency in a UAV hydrogen fuel cell hybrid power system in an embodiment of the application. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the application more clear, the application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0042] In order to solve the problems of shape adaptability defects, motion displacement errors and lack of multi-source cooperation in the prior art, the application provides a UAV hydrogen fuel cell hybrid power system and a control method thereof, which significantly improves the conformability, efficiency and accuracy of radiotherapy through a triangular configuration multi-source array, a bionic two-stage collimator and a four-mode fusion tracking system, and significantly improves the conformability, efficiency and accuracy of radiotherapy.

[0043] In order to facilitate the understanding of the following embodiments of the application, the following embodiments of the application will be described in detail below with reference to the accompanying drawings.

[0044] Reference Figure 1As shown, the embodiment of the present application provides a UAV hydrogen fuel cell hybrid power system, which comprises a fuel cell stack, a super capacitor group, a lithium iron phosphate battery group, a dynamic bus controller, an LSTM neural network prediction module and a Buck-Boost circuit. The fuel cell stack is used to provide a reference power supply, and the power output is adjustable; the super capacitor group is used to output peak current when transient high power demand occurs, and has high power density and fast response characteristics; the lithium iron phosphate battery group is used to provide emergency power supply when the fuel cell fails; the dynamic bus controller integrates a voltage hysteresis comparator and a CAN bus communication module, and is used to control the energy output of the fuel cell stack, the super capacitor group and the lithium iron phosphate battery group; the LSTM neural network prediction module is used to predict future power demand according to flight attitude, meteorological data and historical load curve, and trigger fuel cell power climb in advance; and the Buck-Boost circuit is used for charging the super capacitor group directly by the fuel cell.

[0045] The UAV hydrogen fuel cell hybrid power system of the present application aims at the core pain points of response delay, output fluctuation and emergency landing risk in the UAV hydrogen fuel cell power system. When the UAV is in high-speed maneuvering or sudden load increase, the super capacitor is connected to the high-voltage bus directly in milliseconds to provide 120A peak current instantaneously, thereby completely eliminating the 0.5-second power gap caused by the chemical reaction lag of the fuel cell. The dynamic bus control algorithm is used to cooperate with the lithium battery and the fuel cell, so that the voltage fluctuation rate of the whole power system is less than 0.5% (far exceeding the industry standard of 2%), thereby ensuring the stable operation of the multi-motor system. The super capacitor is used to replace the lithium battery to take charge of the instantaneous energy compensation in the high-maneuvering state, thereby further improving the instantaneous dynamic response speed, greatly reducing the weight of the lithium battery and increasing the endurance time. The unique three-level fault-tolerant mechanism converts power interruption into a controllable emergency mode. Even if the fuel cell fails completely and the super capacitor runs out of power, the lithium battery can take over the load and maintain the power output for 3 minutes within 1 second to ensure the safe landing of the UAV, and the flight control path reconstruction algorithm is used to realize 100% safe landing. The lithium battery health management system is introduced to lock the 80% SOC working point and stop the automatic discharge strategy, thereby increasing the battery calendar life from the industry average of 2 years to more than 5 years, and greatly reducing the whole life cycle operation and maintenance cost. The scheme systematically breaks through the reliability bottleneck in the field of UAV hydrogen fuel cell hybrid power in terms of power response speed under high maneuvering, micro-pressure drop under 120A step load and other measured indicators.

[0046] In this embodiment, the operating voltage range of the fuel cell stack is 48-65V, the rated power is 4kW, and the power ramp rate is ≥50% / s. The super capacitor group is composed of 24 strings of super capacitors or 2 groups of 12 strings of super capacitors in parallel, with a total capacity of ≥40F, an internal resistance of <1mΩ, a direct high-voltage bus, a full pressure of 64.8V to a minimum operating voltage of 44V, and a peak current of 120A for 0-2 seconds.

[0047] In this embodiment, the super capacitor group adopts a 2-group 12-string parallel topology, each group is equipped with an independent voltage equalization circuit, and 50% of the peak output capacity is retained when a single group fails. The lithium iron phosphate battery group includes 14 strings, with a nominal voltage of 44.8V and a storage energy of ≥100Wh, supporting ≥35A continuous discharge for 3 minutes of emergency power supply.

[0048] In this embodiment, the dynamic bus controller integrates a voltage hysteresis comparator and a CAN bus communication module, the response time of the voltage hysteresis comparator is <10μs, and the capacitor-lithium battery seamless switching is realized. The voltage range of the super capacitor group and the lithium battery group naturally covers the 44-65V system requirement, without the need for a DC / DC conversion module.

[0049] In this embodiment, the dynamic bus controller is configured to:

[0050] a) When the super capacitor responds to a >100A step load within 100ms, activate the super capacitor group output peak current within 0.1ms to maintain the system bus voltage fluctuation <5% within 100ms;

[0051] b) Synchronously control the fuel cell stack to linearly ramp up from 30% power to 100% within 2 seconds;

[0052] c) When the fuel cell fails, switch to the lithium battery group to output a constant power of 1400W for ≥180 seconds within 2 seconds, and the lithium battery takes over the load within 2 seconds to ensure a constant power of ≥180 seconds for the safe landing of the UAV.

[0053] Wherein, the Buck-Boost circuit makes the fuel cell stack bypass the lithium battery group to directly charge the super capacitor group, and the lithium battery group locks at 80% SOC (44.8V) during flight and automatically discharges to 50% SOC (43.2V) after shutdown. The dynamic bus controller contains an LSTM neural network prediction module, which inputs flight attitude, weather data and historical load curve, predicts the power demand in the next 10 seconds and triggers the fuel cell power ramp in advance.

[0054] Referring to Figures 1 to 4 The embodiment of the present application provides a control method based on a UAV hydrogen fuel cell hybrid power system, comprising the following steps:

[0055] I. Steady-state load stage: Powered directly by the fuel cell stack (≤50A);

[0056] II. Step Load Response Stage:

[0057] Upon detecting a current request greater than 100A, the supercapacitor bank will initiate discharge within 0.1ms.

[0058] Synchronous command fuel cell stack linearly ramps up from 30% power to 100% within 2 seconds;

[0059] III. Emergency Response Phase:

[0060] T=0-2 seconds: Supercapacitor bank full power output to prevent stall;

[0061] T=2-180 seconds: The lithium battery pack takes over the load at a constant power of 1400W.

[0062] In this embodiment, an LSTM neural network is used to predict the power demand in the next 10 seconds, triggering the fuel cell power ramp-up in advance and reducing the frequency of supercapacitor intervention. Specifically, the Buck-Boost circuit enables direct charging of the fuel cell supercapacitor pack, avoiding the impact of high current from the lithium battery.

[0063] In this embodiment, see Figure 2 As shown, the fuel cell provides basic cruising power (3000-4000W); the supercapacitor maintains a fully charged state (64.8V) and is ready to respond to sudden load changes; the lithium battery maintains 80% SOC (44.8V) and serves only as an emergency backup. For peak load response (such as climbing, sharp turns, and wind resistance), see [link to relevant documentation]. Figure 3 As shown, when encountering sudden load changes such as climbing, strong winds, or sharp turns (0ms), the motor system sends a 120A instantaneous current request to the main controller, triggering the peak load response mechanism. The capacitor responds instantaneously (0-0.1ms), and the main controller activates the supercapacitor bank within 0.1ms, achieving zero-delay discharge through direct connection to the high-voltage bus, and outputting 120A current to fill the power gap.

[0064] Among these features, the supercapacitor has an internal resistance of <1mΩ and a voltage drop of only 0.84V, while traditional solutions have a voltage drop >2V. The fuel cell power transition (1-2 seconds) is synchronized with the main controller, which instructs the fuel cell to gradually increase power (30%→100% linear ramp-up), avoiding the overshoot risk caused by chemical response lag. Seamless energy switching (2 seconds) occurs, with the fuel cell completely taking over the load, the supercapacitor exiting operation and initiating recharging, achieving dynamic bus voltage coordination of 44-65V (without DC / DC conversion).

[0065] See Figure 4 As shown, the emergency response phase for fuel cell failure includes:

[0066] Stage 1 (0-2 seconds):

[0067] Super capacitor independent support 120A peak current;

[0068] Flight control lock attitude angle < 5° anti-instability;

[0069] Stage 2 (2-180 seconds):

[0070] Lithium battery output 1400W constant power;

[0071] Control the descent rate by height segmentation (100m↑: 3m / s→ < 30m: 1m / s).

[0072] In the energy maintenance mode, high-altitude cruise: fuel cell slow charging (20-30A), low-altitude safety state: lithium battery fast charging (50A, need to meet height < 50m + attitude angle < 5° at the same time). When maintaining the lithium battery, after landing, stand still for > 2 hours, automatically discharge to 50% SOC; The power consumption of the avionics equipment is greater than the ceramic resistance heat dissipation.

[0073] The present application adopts 2 groups of 12 super capacitor strings in parallel, which is matched according to the power composition of the unmanned aerial vehicle in the present application. The power system in the present application adopts 48-65V working voltage, and the output power of the fuel cell stack is 4kw. These parameters match the corresponding motor and paddle. If the power system configuration changes, such as the increase of the power of the stack and the increase of the horsepower of the motor, the combination of the super capacitor can be changed. For example, 32 strings, 48 strings, or 2 groups of capacitors in series in the front end, and then multiple groups in parallel; Or first parallel multiple groups, then series. A variety of permutations and combinations of series and parallel can be formed to match different power systems or reflect different power responses. This requires users to flexibly combine according to actual needs.

[0074] Through magnetic resonance wireless power transmission (Qi 2.0 industrial grade), lithium battery and capacitor non-contact charging is realized, which completely eliminates the risk of high-voltage short circuit and isolates the spread of thermal runaway; The charging efficiency is reduced to 85%, the charging time is longer, and the heat dissipation space needs to be increased, the fuel cell direct charging channel is added, and the special Buck-Boost circuit is added, which allows the fuel cell to bypass the lithium battery on the bus and directly charge the capacitor, avoiding the impact of large current on the lithium battery (especially in low temperature working condition), and prolonging the service life of the lithium battery.

[0075] The application realizes microsecond-level transient response by directly connecting the super capacitor group to the high-voltage bus, the dynamic bus controller controls the smooth transition of the fuel cell power, effectively avoids the overshoot risk caused by the chemical response lag, covers the 44-65V system voltage through the super capacitor and lithium battery, saves the DC / DC conversion module, sets the Buck-Boost direct charging circuit, directly charges the super capacitor with the fuel cell, avoids the large current impact of the lithium battery, improves the capacitor recharge speed, and reduces the risk of thermal runaway.

[0076] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A drone hydrogen fuel cell hybrid power system characterized by, The system comprises: a fuel cell stack for providing a reference power supply, the power output of which is adjustable; a super capacitor bank for outputting peak current when there is a transient high power demand, having high power density and fast response characteristics; the super capacitor bank is composed of 24 strings of super capacitors or 2 groups of 12 strings of super capacitors in parallel, the total capacity is ≥40F, the internal resistance is <1mΩ, and the high-voltage bus is directly connected, the full pressure is 64.8V to the minimum working voltage 44V; a lithium iron phosphate battery bank for providing emergency power supply when the fuel cell fails; a dynamic bus controller integrating a voltage hysteresis comparator and a CAN bus communication module for controlling the energy output of the fuel cell stack, the super capacitor bank and the lithium iron phosphate battery bank; an LSTM neural network prediction module for predicting future power demand according to flight attitude, meteorological data and historical load curve, and triggering fuel cell power climb in advance; a Buck-Boost circuit for charging the super capacitor bank directly by the fuel cell; wherein the dynamic bus controller is configured to: a) activate the super capacitor bank to output peak current within 0.1ms when a >100A step load is detected; b) synchronously control the fuel cell stack to linearly increase from 30% power to 100% within 2 seconds; c) switch to the lithium battery bank to output 1400W constant power for ≥180 seconds within 2 seconds when the fuel cell fails.

2. The UAV hydrogen fuel cell hybrid power system of claim 1, wherein, The working voltage range of the fuel cell stack is 48-65V, the rated power is 4kW, and the power climb rate is ≥50% / s.

3. The UAV hydrogen fuel cell hybrid power system of claim 2, wherein, The super capacitor bank adopts a 2-group 12-string parallel topology, each group is equipped with an independent voltage equalization circuit, and 50% of the peak output capacity is retained when a single group fails.

4. The UAV hydrogen fuel cell hybrid power system of claim 2, wherein, The lithium iron phosphate battery bank includes 14 strings, the nominal voltage is 44.8V, and the stored energy is ≥100Wh.

5. The UAV hydrogen fuel cell hybrid power system of claim 4, wherein, The dynamic bus controller integrates a voltage hysteresis comparator and a CAN bus communication module, and the response time of the voltage hysteresis comparator is <10μs.

6. The UAV hydrogen fuel cell hybrid power system of claim 5, wherein, The voltage range of the super capacitor bank and the lithium battery bank naturally covers the 44-65V system requirement, without the need for a DC / DC conversion module.

7. The UAV hydrogen fuel cell hybrid power system of claim 6, wherein, The Buck-Boost circuit makes the fuel cell stack bypass the lithium battery bank to directly charge the super capacitor bank, and the lithium battery bank is locked at 80% SOC during flight and automatically discharged to 50% SOC after shutdown.

8. A control method based on the unmanned aerial vehicle hydrogen fuel cell hybrid power system according to any one of claims 1-7, characterized in that, The steps include: steady load stage: directly powered by fuel cell stack; step load response stage: after detecting a >100A current request, start discharging the super capacitor bank within 0.1ms; synchronously instruct the fuel cell stack to linearly climb from 30% power to 100% within 2 seconds; emergency stage in case of failure: T=0-2 seconds: full power output of the super capacitor bank to prevent stall; T=2-180 seconds: lithium battery bank takes over the load at 1400W constant power.

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