A power management method for hybrid power systems considering high-altitude attenuation

Abstract

This invention discloses a power management method for a hybrid power system considering high-altitude attenuation, comprising: obtaining efficiency attenuation curves of different power sources at different altitudes; comparing the high-altitude performance retention capabilities of different power sources; determining the power sources participating in high-altitude power compensation; considering the quality penalty of the auxiliary power source energy storage system; proposing a segmented power management strategy; and performing simulation analysis on the segmented power management strategy. This invention identifies highly efficient power components by studying the attenuation characteristics of core components of the power system, and determines the switching altitude and power allocation scheme before and after switching by combining the influence of energy storage quality. This achieves a reasonable trade-off between high-altitude attenuation of the power source and energy storage quality compensation, thereby improving the overall high-altitude performance of the system.

Description

Technical Field

[0001] This invention belongs to the field of aviation propulsion engineering, and in particular relates to a power management method for hybrid power systems that takes into account high-altitude attenuation. Background Technology

[0002] As aircraft develop towards higher altitudes, the performance degradation of propulsion systems in high-altitude environments has become a pressing issue in system design. Compared to the warm, humid, and well-pressurized atmospheric conditions at sea level, the atmospheric conditions at high altitudes are characterized by low temperature, low pressure, and low humidity, which poses a significant challenge to all propulsion devices that require sufficient air as an oxidizer.

[0003] In aero-hydro hybrid power systems, the high-altitude power decay characteristics of different power sources vary. Taking piston engines, PEMFCs, and SOFCs with reformers as examples, piston engines experience significant power decay at high altitudes due to reduced intake air density; PEMFCs offer high efficiency and good high-altitude performance retention, but their hydrogen storage systems result in severe mass compensation; while SOFCs with reformers offer certain efficiency advantages, their system complexity and response characteristics affect their aerospace applications. Therefore, power management of hybrid power systems cannot be designed solely based on the rated efficiency of the power sources or a fixed power allocation strategy, but should comprehensively consider the decay characteristics of each power source at different altitudes, the impact of energy storage mass, and flight mission requirements. However, existing methods mostly focus on power coordination under normal operating conditions, rarely considering both high-altitude power decay and energy storage mass compensation simultaneously, making it difficult to achieve optimal overall performance in high-altitude missions.

[0004] Therefore, there is an urgent need for a segmented power management method for hybrid power systems that can identify power sources suitable for high-altitude operating conditions based on the high-altitude attenuation characteristics of different power sources, and determine the switching height and power distribution scheme before and after switching in combination with the influence of energy storage quality. This will achieve a reasonable trade-off between high-altitude attenuation of power sources and compensation by energy storage quality, thereby improving the overall high-altitude performance of the system. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the purpose of this invention is to provide a power management method for hybrid power systems that considers high-altitude attenuation. By studying the attenuation characteristics of the core components of the power system, efficient power components are identified. The switching height and the power distribution scheme before and after switching are determined in combination with the influence of energy storage quality. This achieves a reasonable trade-off between high-altitude attenuation of the power source and compensation by energy storage quality, thereby improving the overall high-altitude performance of the system.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A power management method for a hybrid power system considering high-altitude attenuation is characterized in that the aviation hybrid power system includes a first power source and a second power source, the efficiency of the first power source decreases with increasing flight altitude, and the high-altitude attenuation rate of the second power source is lower than that of the first power source and has energy storage mass compensation. Specifically, it includes the following steps:

[0008] Step 1: Obtain the efficiency decay curves of different power sources at different altitudes.

[0009] This study investigates the high-altitude degradation characteristics of the core components (engine and fuel cell) of a hybrid power system. Through simulation, the efficiency changes of each power source are measured, and the degradation rate is calculated to quantify the impact of the high-altitude environment on the performance of each component, providing data support for power management.

[0010] Step 2: Compare the high-altitude performance retention capabilities of different power sources.

[0011] Based on the efficiency changes and attenuation rates of each power source at different altitudes, their high-altitude adaptability is compared, and power sources with better performance retention in high-altitude environments are identified.

[0012] Step 3: Determine the power source involved in high-altitude power compensation.

[0013] Based on the analysis results of high-altitude attenuation characteristics, a power source with a smaller high-altitude attenuation rate was selected as an auxiliary power source to participate in power compensation at specific altitude stages.

[0014] Step 4: Consider the quality penalty of the auxiliary power source energy storage system.

[0015] To address the quality compensation impact of the energy storage system required for auxiliary power sources, an energy storage quality penalty coefficient is introduced to measure the impact of quality compensation on system performance.

[0016] Step 5: Propose a segmented power management strategy.

[0017] Weighing the efficiency gains from auxiliary power sources against the energy storage quality penalties, a strategy of "different power allocations at different altitudes" is proposed.

[0018] Set the height switch Auxiliary power source output power before switching and the output power of the auxiliary power source after switching When the flight altitude When the altitude is below the switching altitude, the auxiliary power source outputs power at the first power level; when the flight altitude is below the switching altitude... When the height is not lower than the switching height, the auxiliary power source outputs power according to the second power output, i.e.:

[0019]

[0020] The output power of the main power source is the difference between the power required for flight and the output power of the auxiliary power source.

[0021]

[0022] And satisfy:

[0023]

[0024]

[0025]

[0026]

[0027] in, Power required for flight at the current altitude. The maximum available power of the main power source at the current altitude. To ensure the maximum available power of the auxiliary power source at the current altitude, For fuel quality, For the quality of the storage tank, This represents the maximum energy storage mass.

[0028] Step 6: Perform simulation analysis on the segmented power management strategy.

[0029] Several combinations of switching altitude, pre-switching power, and post-switching power were set up to simulate the segmented power management strategy and compare it with a constant power output scheme for the auxiliary power source. Based on system flight time variations, the effectiveness of the segmented power management strategy in improving the overall performance of the hybrid power system in high-altitude environments was verified. To quantitatively evaluate the combined effect of the segmented power management strategy on architecture efficiency and energy storage quality compensation, an energy storage quality-corrected architecture efficiency index was further introduced. Let the architecture efficiency under a certain power allocation scheme be denoted as... The hydrogen storage quality penalty coefficient is ,in A larger value indicates a smaller hydrogen storage mass compensation, so the energy storage mass correction architecture efficiency is defined as:

[0030]

[0031] To compare the PEMFC constant power output scheme and the PEMFC segmented power output scheme, the segmented power comprehensive benefit coefficient is defined as:

[0032]

[0033] in To improve the energy storage quality correction architecture efficiency for segmented power output schemes. The energy storage quality correction architecture efficiency for constant power output schemes.

[0034] when This indicates that the improved hydrogen storage quality resulting from the segmented power strategy can compensate for the reduced architecture efficiency, thus enhancing the overall system performance. This indicator avoids judging the merits of a power allocation scheme solely based on architecture efficiency, allowing the evaluation results to simultaneously reflect both the efficiency characteristics of the power system and the impact of the energy storage system's quality.

[0035] The beneficial effects of the invention are:

[0036] 1. By comparing the efficiency and attenuation rate of different power sources in high-altitude environments, it is possible to identify power sources suitable for high-altitude compensation, providing a basis for power management of hybrid power systems.

[0037] 2. While considering the ability of PEMFC and other fuel cells to maintain high-altitude performance, the factors affecting hydrogen storage quality should be introduced to avoid judging the rationality of fuel cell power distribution solely from the perspective of efficiency.

[0038] 3. A segmented power management strategy based on switching altitude and power before and after switching is proposed, which can adjust the output power of the auxiliary power source according to the change of flight altitude, thereby mitigating the impact of high-altitude attenuation of the main power source on system performance.

[0039] 4. It can be applied to piston engine-PEMFC parallel mechanical propulsion architecture, and can also provide power management reference for other aviation hybrid power systems with high-altitude attenuation differences and energy storage quality compensation characteristics. Attached Figure Description

[0040] Figure 1 This is a flowchart of the invention.

[0041] Figure 2 This is a comparison chart of the efficiency of three devices: a piston engine, two types of fuel cells (PEMFC and SOFC + reforming).

[0042] Figure 3 This is a comparison chart of the attenuation rates of the three devices.

[0043] Figure 4 This is a schematic diagram of a piston engine-PEMFC parallel mechanical propulsion architecture.

[0044] Figure 5 PEMFC power management is in A schematic diagram showing the results at that time. Detailed Implementation

[0045] The invention will be further described below with reference to the accompanying drawings and design scenarios for high-altitude long-endurance UAVs. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0046] A power management method for a hybrid power system considering high-altitude attenuation is presented in this embodiment, using a high-altitude long-endurance unmanned aerial vehicle (UAV) as an example. The method employs a piston engine-PEMFC parallel mechanical propulsion architecture for verification. In this architecture, the piston engine serves as the primary power source, and the PEMFC as the auxiliary power source, both working together to meet the propulsion power requirements of the aircraft at different altitudes. Details are as follows:

[0047] Step 1: Obtain the efficiency decay curves of different power sources at different altitudes.

[0048] Simulink was used to build power source models for a piston engine, PEMFC, and SOFC+reformer, respectively, with the study altitude range set to 0-7000m. Simulations were conducted to obtain the efficiency and attenuation rate variations of each power source at different altitudes, in order to quantify the impact of the high-altitude environment on the performance of different power sources.

[0049] Based on the simulation results, the trend of efficiency of each power source changing with altitude can be obtained, such as... Figure 2 As shown; the trend of attenuation rate of each power source with altitude, as follows. Figure 3 As shown.

[0050] Step 2: Compare the high-altitude performance retention capabilities of different power sources.

[0051] according to Figure 2 and Figure 3 The comparison results show that piston engines are significantly affected by high-altitude low pressure and reduced air density, with their efficiency decreasing markedly with increasing altitude, and the rate of efficiency decline increasing with altitude. PEMFCs exhibit better efficiency retention at high altitudes and a relatively smaller decline rate, making them suitable as auxiliary power sources for high-altitude operations. SOFCs with reformers show efficiency decline at high altitudes between the two. The decline variation shows that at altitudes greater than 3000m, the decline rate of PEMFCs changes faster than that of SOFCs with reformers. Within certain altitude ranges, SOFCs with reformers can serve as alternative auxiliary power sources. Considering efficiency decline characteristics, system complexity, and aerospace applicability, this embodiment selects PEMFCs as the auxiliary power source.

[0052] Step 3: Determine the power source involved in high-altitude power compensation.

[0053] Based on the analysis of high-altitude attenuation characteristics, a piston engine with severe high-altitude attenuation was selected as the primary power source, and a PEMFC with the lowest high-altitude attenuation rate was selected as the auxiliary power source. A piston engine-PEMFC parallel architecture was constructed, as shown in the diagram below. Figure 4 Used for power compensation at specific altitudes. Within certain altitude ranges, the SOFC+ reformer can be seen as an alternative auxiliary power source.

[0054] Step 4: Consider the impact of hydrogen storage quality.

[0055] Since PEMFCs need to carry hydrogen fuel and a hydrogen storage system, but given a fixed maximum takeoff mass and payload of the aircraft, increasing the hydrogen storage mass would reduce the mass of fuel or mission payload. Therefore, this embodiment introduces a hydrogen storage mass penalty coefficient. This study aims to evaluate the impact of PEMFC hydrogen fuel consumption and the quality of its hydrogen storage system on the overall system performance. The larger the value, the smaller the hydrogen storage mass compensation, and the more favorable the mass conditions under which the system can be used for fuel oil or payload.

[0056]

[0057] in The flow rate of hydrogen fuel consumed. The maximum hydrogen mass fraction is set to 0.2, representing the fuel flow rate.

[0058]

[0059] in Total portable fuel mass For fuel flow rate, Total flight time.

[0060] By introducing parameters This avoids judging the rationality of PEMFC power allocation solely from an efficiency perspective, allowing the segmented power management strategy to simultaneously reflect the impact of efficiency changes and quality compensation.

[0061] Step 5: Propose a segmented power management strategy.

[0062] Balancing the high-altitude degradation of components with the mass compensation brought by hydrogen storage, a strategy of "different power allocation at different altitudes" is proposed. A switching altitude is set. Auxiliary power source output power before switching and the output power of the auxiliary power source after switching When the flight altitude is below the switching altitude, the auxiliary power source outputs power at the first power level; when the flight altitude is not below the switching altitude, the auxiliary power source outputs power at the second power level, i.e.:

[0063]

[0064] The output power of the main power source is the difference between the power required for flight and the output power of the auxiliary power source.

[0065]

[0066] in, This represents the power requirement of the aircraft at its current altitude (calculated from mission requirements and model data). For the output power of the piston engine, and satisfying:

[0067]

[0068]

[0069]

[0070]

[0071] in, The maximum available power of the main power source at the current altitude. To ensure the maximum available power of the auxiliary power source at the current altitude, For hydrogen fuel quality, For the quality of the hydrogen storage tank, This represents the maximum energy storage mass.

[0072] It should be noted that the power output of the PEMFC after switching is not necessarily greater than that before switching. Its specific value can be set based on the engine's high-altitude attenuation, the PEMFC's efficiency maintenance capability, the impact of hydrogen storage mass, and flight mission requirements. Under certain operating conditions, engine attenuation can be compensated for by increasing the PEMFC output power; under other operating conditions, hydrogen storage mass compensation can be reduced by decreasing the PEMFC output power.

[0073] Step 6: Perform simulation analysis on the segmented power management strategy.

[0074] exist When six height values ​​of 4750, 5000, 5500, 6000, 6500 and 6750m were obtained respectively, the impact of different power segmentation on the overall architecture performance of PEMFC was studied.

[0075] Studies have found that different power management strategies at altitudes of 6000m and 6500m can both improve flight time. Data (such as) Figure 5 Taking this as an example, the architecture efficiency and hydrogen storage quality penalty coefficient under different power segment settings are shown in Table 1:

[0076] Table 1 Comparison of PEMFC power results with and without power segmentation

[0077]

[0078] As shown in Table 1, in When a power segmentation strategy is adopted, the system efficiency will decrease to some extent, but the hydrogen storage quality penalty coefficient can be increased. To quantitatively evaluate the combined effect of the segmented power management strategy on architectural efficiency and energy storage quality compensation, an energy storage quality-corrected architectural efficiency index is introduced. Let the architectural efficiency under a certain power allocation scheme be denoted as... The hydrogen storage quality penalty coefficient is ,in A larger value indicates a smaller hydrogen storage mass compensation, so the energy storage mass correction architecture efficiency is defined as:

[0079]

[0080] To compare the PEMFC constant power output scheme and the PEMFC segmented power output scheme, the segmented power comprehensive benefit coefficient is defined as:

[0081]

[0082] in To improve the energy storage quality correction architecture efficiency for segmented power output schemes. The energy storage quality correction architecture efficiency for constant power output schemes.

[0083] get The energy storage quality correction architecture efficiency and segmented power comprehensive benefit coefficients of each scheme are shown in Table 2:

[0084] Table 2 Comparison of PEMFC results with the same power and power segmentation and Comparison

[0085]

[0086] In this embodiment, when the switching altitude is 6500m and the PEMFC adopts power segmentation scheme D, that is, the PEMFC power is 20kW before switching and 10kW after switching. Figure 5 Simulation results show that the segmented power scheme can effectively improve flight time by 1.4% compared to the PEMFC constant power scheme. Furthermore, other power segmentation schemes at this altitude also contribute to flight time improvements, demonstrating the feasibility of the segmented power management strategy described in this invention. Although scheme D has the lowest architectural efficiency, it has the highest hydrogen storage quality penalty coefficient. The architectural efficiency reaches its highest value after energy storage quality correction, indicating that under this scheme, the contribution of hydrogen storage quality compensation improvement to the overall system performance outweighs the adverse effects of efficiency reduction. Combined with flight time simulation results, scheme D exhibits the greatest flight time improvement, verifying the effectiveness of the segmented power management strategy in high-altitude long-endurance missions.

Claims

1. A method of power management for a hybrid system taking into account high altitude attenuation, characterized in that, The hybrid power system includes a first power source and a second power source. The efficiency of the first power source decreases with increasing flight altitude, while the efficiency of the second power source decreases at higher altitudes than that of the first power source and has energy storage mass compensation. Specifically, it includes the following steps: Step 1: Obtain the efficiency decay curves of different power sources at different altitudes; The high-altitude attenuation characteristics of the core components of the hybrid power system are studied. Through simulation, the efficiency changes of each power source are measured and the attenuation rate is calculated to quantify the impact of the high-altitude environment on the performance of each component and provide data support for power management. Step 2: Compare the high-altitude performance retention capabilities of different power sources; Based on the efficiency changes and attenuation rates of each power source at different altitudes, their high-altitude adaptability is compared, and power sources with better performance retention in high-altitude environments are identified. Step 3: Determine the power source involved in high-altitude power compensation; Based on the analysis results of high-altitude attenuation characteristics, a power source with a smaller high-altitude attenuation rate is selected as an auxiliary power source to participate in power compensation at a specific altitude. Step 4: Consider the quality penalty of the auxiliary power source energy storage system; To address the quality compensation impact of the energy storage system required for auxiliary power sources, an energy storage quality penalty coefficient is introduced to measure the impact of quality compensation on system performance. Step 5: Propose a segmented power management strategy; Weighing the efficiency gains from the auxiliary power source against the energy storage quality penalty, we adopted a strategy of "different power allocation at different altitudes"; Step 6: Perform simulation analysis on the segmented power management strategy; Several sets of switching altitude, power before switching, and power after switching were set up to simulate the segmented power management strategy and compare it with the constant power output scheme of the auxiliary power source. Based on the system flight time changes, it was verified whether the segmented power management strategy can improve the overall performance of the hybrid power system in high-altitude environment.

2. The power management method for a hybrid power system considering high-altitude attenuation according to claim 1, characterized in that, Step 5 is detailed below: Set the height switch Auxiliary power source output power before switching and the output power of the auxiliary power source after switching When the flight altitude When the altitude is below the switching altitude, the auxiliary power source outputs power at the first power level; when the flight altitude is below the switching altitude... When the height is not lower than the switching height, the auxiliary power source outputs power according to the second power output, i.e.: ； The output power of the main power source is the difference between the power required for flight and the output power of the auxiliary power source. ； And satisfy: ； ； ； ； in, Power required for flight at the current altitude. The maximum available power of the main power source at the current altitude. To ensure the maximum available power of the auxiliary power source at the current altitude, For fuel quality, For the quality of the storage tank, This represents the maximum energy storage mass.

3. The power management method for a hybrid power system considering high-altitude attenuation according to claim 1, characterized in that, In step 6, to quantitatively evaluate the comprehensive effect of the segmented power management strategy on the relationship between architecture efficiency and energy storage quality compensation, an energy storage quality-corrected architecture efficiency index is introduced; let the architecture efficiency under a certain power allocation scheme be... The hydrogen storage quality penalty coefficient is ,in A larger value indicates a smaller hydrogen storage mass compensation, so the energy storage mass correction architecture efficiency is defined as: ； To compare the PEMFC constant power output scheme and the PEMFC segmented power output scheme, the segmented power comprehensive benefit coefficient is defined as: ； in To improve the energy storage quality correction architecture efficiency for segmented power output schemes. To improve the energy storage quality correction architecture efficiency for constant power output solutions; when This indicates that the improved hydrogen storage quality brought about by the segmented power strategy can compensate for the reduction in architecture efficiency, thereby improving the overall system performance. This indicator avoids judging the merits of the power allocation scheme solely based on architecture efficiency, allowing the evaluation results to simultaneously reflect the efficiency characteristics of the power system and the impact of the energy storage system quality.

4. The power management method for a hybrid power system considering high-altitude attenuation according to claim 1, characterized in that, In step 1, the core components of the hybrid power system include the engine and the fuel cell. Simulink is used to build power source models of the piston engine, PEMFC and SOFC+reformer respectively, with the altitude range set to 0-7000m. The efficiency changes and attenuation rate changes of each power source at different altitudes are obtained through simulation to quantify the impact of the high-altitude environment on the performance of different power sources.

5. The power management method for a hybrid power system considering high-altitude attenuation according to claim 1, characterized in that, In step 4, a hydrogen storage mass penalty coefficient is introduced. This study aims to evaluate the impact of PEMFC hydrogen fuel consumption and the quality of its hydrogen storage system on the overall system performance. The larger the value, the smaller the hydrogen storage mass compensation, and the more favorable the mass conditions under which the system can be used for fuel oil or payload. ； in The flow rate of hydrogen fuel consumed. For fuel flow rate, the maximum hydrogen storage mass fraction is set to 0.2; ； in Total portable fuel mass For fuel flow rate, Total flight time; by introducing parameters This avoids judging the rationality of PEMFC power allocation solely from an efficiency perspective, and ensures that the segmented power management strategy simultaneously reflects the impact of efficiency changes and quality compensation.

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