A power following control method based on altitude adaptive change

Abstract

A power following control method based on altitude adaptive change, comprising the following steps: adaptive calculation of engine matching power with altitude change; adaptive calculation of generator equivalent output power with altitude change; power following matching control of the whole vehicle power system according to the engine matching power, the equivalent output power of the generator and the SOC value of the vehicle battery. The control method can realize smooth output and stable maintenance of vehicle energy in complex environment, to adapt to the power matching design requirements of energy system in dynamic environment.

Description

Technical Field

[0001] This invention relates to the field of vehicle energy and power system control technology, and in particular to a power following control method based on altitude adaptive variation. Background Technology

[0002] As altitude changes, the external environment also changes synchronously. The operating environment of the vehicle system differs significantly from that in plains areas, especially for the engine. Changes in temperature and air density at high altitudes cause changes in parameters such as fuel efficiency, output power, and required RPM under the same load in plains areas. Furthermore, the environment for sports cars in high-altitude areas is relatively harsher. In this situation, the powertrain system in plains areas needs to adaptively adjust to environmental changes; a single power performance matching method is no longer sufficient to meet the multi-level system power energy performance requirements under mixed operating conditions.

[0003] When driving in flat areas, vehicles only need to consider load changes, as temperature and air density have minimal impact on the powertrain. If the load changes, the powertrain can meet the demand by adjusting engine speed. However, as altitude increases, these factors cause a sharp drop in the vehicle's powertrain output power and energy efficiency. At this point, the power matching relationship between the engine and generator needs to be comprehensively considered. Furthermore, due to the hybrid system's components, the battery also plays a role in energy storage and charging during this process, requiring a comprehensive consideration of the relationship between all three elements during power matching.

[0004] As a power control method, power following control can achieve efficient engine operation while ensuring energy utilization, and avoid the impact of repeated engine start-stop cycles on its lifespan. For the generator, under the condition of matching the external power demand, it can maintain a stable output of vehicle energy and prevent driving jerks caused by energy interruptions. Summary of the Invention

[0005] This disclosure provides a power following control method based on altitude-adaptive variation, based on an integrated energy and power system of "engine-generator-battery," to adapt to the power matching design requirements of the energy system under dynamic environmental changes. This control method fully considers the impact of environmental factors on engine output power, the actual demand for equivalent generator power within the cycle range, and the design process of engine-generator-battery power collaborative matching strategy under comprehensive operating conditions, enabling stable energy output and maintenance of the vehicle in complex environments.

[0006] The power energy system architecture disclosed herein is as follows: Figure 1As shown, it mainly includes: an on-board engine and its control system, an on-board generator and its control system, an on-board battery pack and its control system, as well as corresponding mechanical and electrical components. The coordinated operation of these three components can meet the performance requirements of the entire vehicle load. This disclosure mainly focuses on the development and design of system power following control under varying altitude conditions.

[0007] The power following control method disclosed herein mainly consists of three parts: engine power adaptive calculation, generator power adaptive calculation, and power following matching of the power system. Among them:

[0008] The adaptive calculation process for engine power mainly considers the power loss caused by altitude changes and the energy loss from heating and preheating, based on the engine's rated output power. Therefore, a power loss coefficient λ is proposed. a The concept of preheating power coefficient γ, combined with the actual output power P. a and target power P g Finally, the effective matching power value P is obtained. m .

[0009] The adaptive calculation process for generator power mainly involves applying a power correction factor σ to the generator's rated power. g The actual output power P was calculated. ga At this point, considering the total work done by the generator within its effective operating time range over the period, and combining this with the optimal number of time nodes N, * The equivalent output power P is calculated. gaS .

[0010] Based on the obtained matching power P m Equivalent output power P gaS In addition to the battery SOC (State of charge) value, we conduct system energy matching and calculation under power difference conditions, and finally complete the design of the power system energy power following control strategy.

[0011] Compared with the prior art, the beneficial effects of this disclosure are: (1) By acquiring information such as altitude change, temperature change, and air density change in real time, the engine throttle opening, engine speed and battery SOC of the power energy system are dynamically and comprehensively controlled, which can meet the dynamic matching of generator power under the target load, target torque and target power requirements; (2) In high-altitude areas, the system state parameters are optimized in reverse by matching results, and the system performance is optimized in stages under the conditions of lowest energy consumption and highest utilization rate, and the overall optimization of the driver's target performance and power control unit requirements is completed, and finally the three-in-one energy system supply system is built; (3) The vehicle energy output and stable maintenance are achieved in complex environments; (4) The control method is simple and has good engineering practicality. Attached Figure Description

[0012] The above and other objects, features and advantages of this disclosure will become more apparent from the more detailed description of exemplary embodiments of this disclosure taken in conjunction with the accompanying drawings, in which the same reference numerals generally represent the same components.

[0013] Figure 1 This is a schematic diagram of the power energy system architecture involved in this disclosure;

[0014] Figure 2 This is a power follower control strategy based on altitude-adaptive changes. Detailed Implementation

[0015] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0016] This disclosure is based on the research of an integrated power unit composed of an engine, generator, battery pack and related components connected in series, and provides a power following adjustment and control method, which mainly involves the problem of vehicle power following matching and control under altitude changes.

[0017] In real-world operating conditions, vehicle power systems need to comprehensively assess changes in altitude, environment, temperature, and load. Under dynamic conditions, the power demand is matched to the specific states of the engine, generator, and battery to achieve energy coordination and vehicle power adjustment under time-varying conditions. The altitude-adaptive power-following control method involves calculating engine output power, generator output power, and a power matching mechanism between the two and the battery. Under different demand and energy reserve conditions, the vehicle power system is comprehensively regulated. This results in an intelligent power-following system that maintains system stability, lifespan, and safety, achieving overall optimal vehicle power performance during driving.

[0018] The following is in conjunction with the appendix Figure 2 The present disclosure is further explained based on a vehicle height dynamic adjustment control system with an air suspension.

[0019] like Figure 2 As shown, the power follower control method based on altitude adaptive variation includes the following steps:

[0020] Step 1: Adaptive Calculation of Engine Power under Altitude Changes

[0021] 1.1 Calculation of Actual Engine Output Power

[0022] Temperatures are low at high altitudes, so the engine needs to be preheated. The preheating power is P. t Meanwhile, since repeated starting and stopping of the electric motor will significantly affect its performance and lifespan, the power output at idle speed is set to P at an altitude of H meters. i The engine's specific operating range is determined by the vehicle's power requirements. Under normal altitude conditions, the engine's normal operating temperature range is set to [T]. d ,T u The corresponding normal operating power range is [P]. d ,P u As altitude changes, variations in temperature and air density simultaneously affect the engine's output power. At this point, assuming the actual engine speed n... a The corresponding working power of the lower engine is P w Considering the additional loss value P al Then its actual output power P a for:

[0023]

[0024] In the formula, λ a The power loss coefficient is altitude-dependent, relating to the current altitude H, while γ is the preheating power coefficient, which is related to the temperature T at the corresponding altitude. H Related.

[0025] Assuming the temperature on the ground is T, the ambient temperature at each altitude increase of H meters is T. H =T-0.006H. At this point, to ensure simultaneous engine start-up time and service life, the preheating time range is set to [1 / 6h, 12h]. Within this range, the corresponding preheating power coefficient γ of the engine is:

[0026]

[0027] Considering the differences in oxygen concentration at different altitudes, the actual output power P a The corresponding power loss coefficient λ a for:

[0028]

[0029] 1.2 Calculation of Actual Engine Matching Power

[0030] At the same time, because the oxygen density in the air is lower at high altitudes, the engine needs to increase its actual speed n. aTo match the actual power requirements, set the torque T g The corresponding target power is P g Then its corresponding matching torque T m Matching power P m for:

[0031]

[0032] In the formula, ξ a For high-altitude areas, the actual rotational speed n a The speed compensation coefficient is related to the power saturation η and the change in system power difference (P). g -P a (Related to)

[0033] The engine's maximum power speed is n wm This rotational speed depends on the engine's inherent characteristics at the time of manufacture and is an inherent value. Within a fixed period Δt, the change in system power difference (P) is defined. g -P a If the corresponding power saturation is η, then:

[0034]

[0035] Considering the maximum power speed n wm and the change in system power difference (P) g -P a From this, we can obtain the compensation coefficient ξ. a The calculation method is as follows:

[0036]

[0037] At this point, in high-altitude areas, it is necessary to increase the actual engine speed n. a To meet the matching power P m .

[0038] Step 2: Adaptive Calculation of Generator Power Based on Altitude Changes

[0039] 2.1 Calculation of Equivalent Output Power of Generator

[0040] Considering that the air becomes thinner with increasing altitude, the air intake of the cooling system is limited. Therefore, to prevent the generator from overheating and limit its actual output power, let's assume the actual output power of the generator is P. g Then its corresponding actual output power P ga Then it is:

[0041] P ga =σ g P g

[0042] In the formula, σ g This is a power correction factor, which is related to altitude. In the calculation process of this patent, areas below 2500 meters are defined as medium-altitude areas, and areas above 2500 meters are defined as high-altitude areas. Therefore, σ can be obtained. g The corresponding calculation formula is:

[0043]

[0044] Meanwhile, since the generator's operating time is also limited in high-altitude areas, we assume that the actual operating time of the generator during the time interval 0-S is S. e And satisfy S e ≤S. At this point, the actual working time S... e Dividing the time into N equal time nodes, the actual output power of the generator at the Mth node (M∈[0,N]) is P. ga|M So, the work W done by the system in the 0-S time interval is... S and its equivalent output power P gaS The details are as follows:

[0045]

[0046] In the formula, N * This represents the optimal number of time nodes.

[0047] 2.2 Calculation of the optimal number of time nodes within the period

[0048] Optimal number of time nodes N * The choice of the maximum value P of the difference between the actual output power of the generator at two adjacent times. ga|M_max and minimum value P ga|M_min The correlation (M∈[0,N]) is calculated as follows:

[0049]

[0050] During the calculation process, N and N * All values ​​are positive integers, and a preset value for N is used before calculation. To prevent large errors in the power calculation results due to differences in the value of N, the value of N is adjusted to ensure the maximum power difference P. ga|M_max and minimum difference P ga|M_min The difference remains within a certain range. Then, the suboptimal value N is... * The formula for determining the value of is as follows:

[0051]

[0052] In the formula, ε is a very small positive integer to prevent the calculation results from becoming unstable.

[0053] Since the calculated sub-optimal value N * is not necessarily a positive integer, the optimal number of time nodes N needs to be obtained through rounding operation * , and its corresponding value is:

[0054] N * =[N *s

[0055] In the formula, [a] represents the rounding operation on the number a

[0056] Step 3: Power following matching calculation of the power system

[0057] According to the engine matching power P m , the equivalent output power P gaS of the generator, and the SOC value of the vehicle-mounted battery, the power following matching calculation of the vehicle's power unit can be carried out

[0058] Since too low SOC will cause the output power to drop rapidly and its power supply to be unstable, its threshold value is set to u (10% ≤ u ≤ 30%). On this premise, there is:

[0059] 3.1 If (P m -P gaS )≥0 and SOC≥u, then at this time the engine needs to gradually reduce its rotational speed value n L within the time S a until P m =P gaS . At this time, the change rate of the rotational speed value n a and the optimal rotational speed at this time are:

[0060]

[0061] 3.2 If (P m -P gaS )≥0 and SOC<u, then at this time the power margin of the engine matching (P m -P gaS ) will charge the battery until SOC≥3u, and at this time the engine power operates stably at a power that satisfies the condition P m =P gaS

[0062] 3.3 If (P m -P gaS )<0 and SOC≥u, then on the premise of ensuring SOC≥u, at this time the engine and the battery jointly supply power to the generator until P m +P SOC =P gaS , and the matching power of the engine at this time is P​​m = P gaS , the battery stops working. If during the process of the engine and the battery jointly powering the generator, SOC = u, then at this time the battery stops working, and at the same time, it is considered to increase the throttle opening to match the actual power demand.

[0063] Assume that the current throttle opening of the vehicle is d (0% ≤ d < 100%), then a stepped power matching strategy is selected to perform online adjustment of the engine matching power. At this time, the new value d * of the throttle opening has the following increment strategy:

[0064]

[0065] In the stepped power matching strategy, the engine needs to run continuously for a period of time at the current throttle opening to ensure stable power output at this throttle opening. The corresponding continuous working time length S at this throttle opening c needs to consider the power difference (P m - P gaS ) and the SOC difference (SOC - u) for optimization calculation. Then there is the following calculation equation:

[0066]

[0067] In the formula, k p and k i are the difference proportional coefficient and the difference differential coefficient respectively.

[0068] If the throttle opening is 100% at this time and the continuous working time length S c is reached, then at this time the engine needs to increase the speed n a to meet the actual power demand. In the current state, the optimal matching speed of the engine is:

[0069]

[0070] Adjust according to the optimal speed value. If the power matching cannot be satisfied after three consecutive speed increases, that is: P m = P gaS , then the engine runs stably at the speed value after three increases, and the system no longer adjusts at this time.

[0071] 3.4 If (P m - P gaS ) < 0 and SOC < u, then the battery does not participate in power supply. At this time, the system needs to automatically adjust the throttle opening to 100%, and at the same time the engine automatically adjusts the speed value n aAt this point, the speed is adjusted based on the power difference and the SOC difference to obtain the optimal matching speed for the current state. for:

[0072]

[0073] Adjustments are made based on the optimal speed value. If three consecutive speed increases fail to meet power matching requirements, i.e., P... m =P gaS Then the engine will run at a stable speed after three increases, and the system will no longer make adjustments.

[0074] The above technical solutions are merely exemplary embodiments of the present invention. For those skilled in the art, based on the application methods and principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the methods described in the specific embodiments of the present invention. Therefore, the methods described above are merely preferred and not restrictive.

Claims

1. A power follower control method based on altitude adaptive variation, comprising the following steps: S1, adaptive calculation of engine power varying with altitude, includes: Establish a calculation relationship between engine speed and actual output power in relation to altitude; Based on the calculated relationship between the target torque and engine output power, calculate the engine matching power corresponding to the target torque that is altitude-dependent. S2, adaptive calculation of the generator's equivalent output power as altitude varies; S3, based on the engine matching power, generator equivalent output power, and vehicle battery SOC value, perform power following and matching control of the vehicle power system; In step S1, the calculation relationship between engine speed and actual output power is as follows: in, P a This refers to the actual output power; P d , P u This refers to the normal operating power range of the engine. λ a In order to match the current altitude H The relevant power loss factor; P w Rotational speed n a The engine's operating power; P i Altitude H The power of the engine at idle speed; P al Additional loss value; γ This is the preheating power coefficient, which is related to the temperature at the corresponding altitude. T H Related; in: H represents the current altitude, in meters. Under the condition that the preheating time range is [1 / 6h, 12h], the corresponding preheating power coefficient of the engine γ for: ； T H = T -0.006 H ； T This refers to the ground temperature.

2. The method according to claim 1, characterized in that, In step S1, the method for calculating the actual matching power of the engine includes: Target torque T g With engine target power P g The correspondence between them is as follows: , The target rotational speed; At high altitudes, the corresponding target torque T m ( T m = T g The actual matching power of the engine P m It should be: In the formula, For actual rotational speed in high-altitude areas n a The speed compensation coefficient, which is related to the power saturation. η and system power difference change ( P g - P a Related to; Assume the engine's maximum power speed is n wm In a fixed period t Within, the change in system power difference ( P g - P a The corresponding power saturation η for: Then the compensation coefficient ξ a The calculation method is as follows: 。 3. The method according to claim 2, characterized in that, Step S2 specifically includes: Assume the generator output power is P g Its corresponding actual output power P ga for: In the formula, σ g This is the power correction factor, which is related to altitude, and the calculation formula is: ； Let time 0- S The actual working time of the internal generator is S e ,and S e ≤ S ,Will S e Divide into equal parts N The first time point, the M indivual( M ∈[0, N The actual output power of the generator under node ]) is P ga|M ; Then 0- S The work done by the system within a time period W S and its equivalent output power P gaS Represented as: In the formula, N * This represents the optimal number of time nodes.

4. The method according to claim 3, characterized in that, The optimal number of time nodes N * The selection process includes the following steps: First, set one N Value, through adjustment N The value is used to ensure that the difference between the actual output power of the generator at two adjacent times is maximized. P ga|M_max and minimum value P ga|M_min The differences remain within a certain range of variation, thereby obtaining... N * suboptimal value The value can be represented as: In the formula, , ; ε It should be an extremely small positive integer to prevent the calculation results from becoming unstable; right N * Suboptimal value Perform a rounding operation to obtain the optimal number of time nodes. N * ,Right now: In the formula, [ a ] indicates a number a Perform the rounding operation.

5. The method according to claim 3 or 4, characterized in that, In step S3, the power following and matching control method for the vehicle powertrain system includes: Set SOC threshold u (10%≤) u ≤30%) if( P m - P gaS )≥0, and SOC≥ u Then the engine will be in time S L Gradually reduce its speed value n a To the optimal speed , making P m = P gaS ; if( P m - P gaS )≥0, and SOC< u Then, the matching power margin of the engine is utilized ( P m - P gaS Charge the battery until SOC ≥ 3 u Then the engine meets P m = P gaS Stable power operation; if( P m - P gaS )<0, and SOC≥ u Then, ensuring SOC ≥ u Under the premise that the engine and battery work together to power the generator, until... P m + P SOC = P gaS At this time, the engine's matching power is P m = P gaS The battery then stops working; if the engine and battery are both supplying power to the generator, SOC = u At this point, the battery stops working, and we consider increasing the throttle opening to match the actual power demand. if( P m - P gaS )<0, and SOC< u If the battery does not contribute to power supply, the system adjusts the throttle opening to 100%, and the engine adjusts the power output according to the power difference (i.e., ...). P m - P gaS Automatically adjust speed value n a To the optimal speed If the throttle opening is already 100% and has been operating for a certain period of time; S c In this case, the engine needs to increase its speed. n a To the optimal speed To meet actual power requirements; adjust according to the optimal speed value. If three consecutive speed increases fail to meet power matching, i.e. P m = P gaS Then the engine will run at a stable speed value after three increases, and the system will no longer make adjustments.

6. The method according to claim 5, characterized in that, In step S3, when ( P m - P gaS )≥0 and SOC≥ u The engine in time S L When the internal speed is gradually reduced, the speed value n a rate of change and optimal speed for: when( P m - P gaS )<0, and SOC< u At that time, the optimal rotational speed and They are respectively: ； 。 7. The method according to claim 5, characterized in that, In step S3, ( P m - P gaS )<0 and SOC< u When the system adjusts the throttle opening to 100%, the methods include: A stepped power matching strategy is adopted to adjust the engine power online, and the corresponding new throttle opening value is obtained. d * The incremental strategy is as follows: ； in d The current throttle opening of the vehicle, 0%≤ d <100%; In a stepped power matching strategy, the engine needs to run continuously for a period of time at the current throttle opening. S c To ensure stable power output under this throttle position, among which, S c Calculate using the following formula: In the formula, k p and k i These are the difference proportional coefficient and the difference differential coefficient, respectively.

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