Electric energy autonomous distribution method for direct-drive electric propulsion power supply system of spacecraft

Abstract

The invention discloses an electric energy autonomous distribution method for a direct-drive electric propulsion power supply system of a spacecraft, and belongs to the technical field of spacecraft power supplies. In the spacecraft electric energy distribution process, the power of a solar cell array, the power of a low-voltage load and the current and voltage of a storage battery pack are collected, the SOC of the storage battery pack is predicted, reasoning is carried out by utilizing a fuzzy rule, and the working gear and the working power of the electric propulsion load are obtained through adjustment on the basis of the reference power of the electric propulsion load. And meanwhile, a model prediction control method is utilized, the state space of the storage battery pack model is discretized, an objective function and constraint conditions capable of tracking the battery current of the storage battery pack with high precision are designed, the SOC is controlled within a safe range, and the service life of the SOC is prolonged.

Description

Technical Field

[0001] The invention relates to an autonomous electric energy distribution method for a spacecraft direct-drive electric propulsion power supply system, and belongs to the technical field of spacecraft power supplies. Background Art

[0002] Environmental conditions such as light, temperature and angle of incidence vary greatly, and spacecraft missions have the characteristics of long on-orbit time and strong autonomous planning, which requires the spacecraft power supply system based on "solar array + battery pack" to have strong environmental adaptability, wide operating points, intelligent control and other functions. Therefore, taking into account the high power and adjustable gear operation requirements of electric propulsion, as well as the working safety and extended service life of the battery pack, is an important research direction for the power supply energy management of the spacecraft direct-drive electric propulsion power supply system.

[0003] When the output power of the solar array decreases, the power margin is tight and it is difficult to support high-level, high-power electric propulsion loads. The battery pack needs to be discharged to replenish energy. When the output power of the solar array returns to a higher level, the battery pack is charged again. However, frequent charging and discharging can easily cause problems such as accelerated capacity attenuation, accelerated electrolyte consumption, increased internal resistance, increased internal temperature, and reduced effective electrode area, shortening the battery pack damage. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide a method for autonomous distribution of electric energy for a spacecraft direct-drive electric propulsion power supply system, thereby realizing autonomous distribution of electric energy, adjusting the working gear of the electric propulsion load, and controlling the SOC of the battery pack within a safe range, thereby extending the service life.

[0005] The technical solution of the present invention is: a method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system, comprising:

[0006] Initialize and set the electric spacecraft propulsion load, which is divided into several levels from low to high according to the power consumption;

[0007] Collect spacecraft solar array power, battery current and voltage, and low-voltage load power;

[0008] Calculate the reference power allocated to the electric propulsion load according to the solar cell array power and the low-voltage load power, and determine the reference gear position of the electric propulsion according to the reference power;

[0009] Predict the SOC of the spacecraft battery pack based on the battery pack current and voltage;

[0010] The regulating power of the electric propulsion load is obtained according to the power of the solar cell array and the SOC of the battery group, and the reference gear of the electric propulsion is superimposed to obtain the working power of the electric propulsion load and the corresponding working gear;

[0011] Calculate the target current of the battery pack using the power of the solar array, the power of the low-voltage load, and the operating power of the electric propulsion load, and achieve the tracking of the battery pack current.

[0012] Further, the maximum power of the electric propulsion load is P promax = P pv - P lowload ; where P promax represents the maximum power that can be allocated to the electric propulsion load, P pv represents the power of the solar array, and P lowload represents the power of the low-voltage load.

[0013] Further, the electric spacecraft propulsion load has N gears in ascending order of power consumption, and the corresponding powers are P pro [1], …, P pro [j], ……, P pro [N], 1 < j < N and j is an integer;

[0014] The determination of the reference gear of the electric propulsion includes:

[0015] When P pro [j - 1] < P promax ≤ P pro [j], the reference gear of the electric propulsion load is j, and the reference power P pro0 = P pro [j];

[0016] When P promax ≤ P pro [1], the reference gear of the electric propulsion load is 1, and the reference power P pro0 = P pro [1];

[0017] When P promax > P pro [N], the reference gear of the electric propulsion load is N, and the reference power P pro0 = P pro [N]; P promax is the maximum power of the electric propulsion load.

[0018] Further, the SOC of the battery pack is where SOC0 can be determined according to the open-circuit voltage U ocv , I bat represents the current of the battery pack, and Q0 represents the nominal capacity of the battery pack.

[0019] Further, the open-circuit voltage U ocv and current I batsatisfy Among them, U bat Indicates that according to the voltage of the battery pack, U o Indicates the polarization voltage of the battery pack, R i Represents the ohmic internal resistance of the battery pack, R o represents the polarization resistance of the battery pack, and C represents the polarization capacitance of the battery pack.

[0020] Furthermore, the regulating power of the electric propulsion load is obtained by fuzzy rules according to the solar array power and the battery group SOC.

[0021] Furthermore, the target current of the battery pack is I * bat Indicates the target current of the battery pack, P pv Represents the solar array power, P lowload Indicates low voltage load power, P pro represents the maximum power that can be allocated to the electric propulsion load, U bat Indicates the voltage of the battery pack.

[0022] Furthermore, the method for tracking the battery pack current is a model predictive control method.

[0023] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for autonomously distributing electric energy for a spacecraft direct-drive electric propulsion power supply system.

[0024] An autonomous electric energy distribution device for a spacecraft direct-drive electric propulsion power supply system comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and is characterized in that when the processor executes the computer program, steps of a method for autonomous electric energy distribution for a spacecraft direct-drive electric propulsion power supply system are implemented.

[0025] The advantages of the present invention compared with the prior art are:

[0026] In the process of spacecraft power distribution, the present invention collects the power of the solar array, the power of the low-voltage load, the current and voltage of the battery group, predicts the SOC of the battery group, and uses fuzzy rules for reasoning to adjust the working gear and working power of the electric propulsion load based on the reference power of the electric propulsion load. At the same time, the model predictive control method is used to discretize the state space of the battery group model, and the objective function and constraint conditions that can achieve high-precision tracking of the battery current of the battery group are designed to control the SOC within a safe range and extend its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0028] Figure 1 This is the structural diagram of the direct-drive electric propulsion power supply system for spacecraft provided by the present invention.

[0029] Figure 2 This is the flowchart of the method for autonomous power distribution of the direct-drive electric propulsion power supply system for spacecraft provided by the present invention. Detailed implementation manners

[0030] To better understand the above technical solutions, the technical solutions of the present invention will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present invention and the embodiments are detailed descriptions of the technical solutions of the present invention, rather than limitations on the technical solutions of the present invention. Without conflict, the technical features in the embodiments of the present invention and the embodiments can be combined with each other.

[0031] The following further details the method for autonomous power distribution of a direct-drive electric propulsion power supply system for spacecraft provided by an embodiment of the present invention with reference to the accompanying drawings of the specification. The specific implementation manners may include: the method is used to formulate a power distribution strategy for the power supply system; the direct-drive electric propulsion power supply system for spacecraft includes a solar array, a battery pack, a battery charge and discharge module, a low-voltage load, and an electric propulsion load; the solar array supplies power to the low-voltage load and the electric propulsion load; the battery pack supplies power to the low-voltage load and the electric propulsion load through the battery charge and discharge module; when the power provided by the solar array is greater than the power of the low-voltage load and the electric propulsion load, the battery pack can also absorb the excess power through the battery charge and discharge module; the electric propulsion load is a power discrete load with multiple grades; the autonomous power distribution module implements the method for autonomous power distribution of the direct-drive electric propulsion power supply system for spacecraft.

[0032] The method includes:

[0033] Initialize and set the electric propulsion load, with a total of N grades from low to high in terms of power consumption, and the corresponding powers are P pro [1], …, P pro [j], ……, P pro [N], 1 < j < N and j is an integer.

[0034] Collect the power of the solar array, the current and voltage of the battery pack, and the power of the low-voltage load;

[0035] Calculate the reference power allocated to the electric propulsion load according to the solar cell array power and the low-voltage load power, and determine the reference gear position of the electric propulsion according to the power;

[0036] Predicting the SOC of the battery pack according to the current and voltage of the battery pack; the SOC of the battery pack is the state of charge, i.e., State of Charge;

[0037] Input the solar array power and battery group SOC into the fuzzy rule table to obtain the regulated power of the electric propulsion load, and superimpose the reference power of the electric propulsion to obtain the working power of the electric propulsion load and the corresponding working gear;

[0038] The target current of the battery pack is calculated using the power of the solar array, the power of the low-voltage load and the working power of the electric propulsion, and the MPC method is used to achieve high-precision tracking of the battery pack current; the MPC method is Model Predict Control.

[0039] Optionally, it is characterized in that the maximum power allocated to the electric propulsion load is:

[0040] P promax =P pv -P lowload

[0041] Where P promax represents the maximum power that can be allocated to the electric propulsion load, P pv Represents the solar array power, P lowload Indicates low voltage load power.

[0042] When the judgment conditions are met, P pro [j-1] <P promax ≤P pro [j], the reference gear of the electric propulsion load is j, and the reference power of the electric propulsion load is P pro0 =P pro [j]; When the judgment conditions are met, P promax ≤P pro [1], the reference gear of the electric propulsion load is 1, and the reference power of the electric propulsion load is P pro0 =P pro [1]; When the judgment condition P is met promax >P pro [N], the reference gear of the electric propulsion load is N, and the reference power of the electric propulsion load is P pro0 =P pro [N].

[0043] Optionally, the formula for predicting the battery pack SOC is:

[0044]

[0045] SOC0 can be calculated based on the open circuit voltage U ocv , from the OCV-SOC curve, I bat represents the current of the battery pack, and Q0 represents the nominal capacity of the battery pack.

[0046] Open circuit voltage U of the battery pack ocv and current I bat The relationship between them is:

[0047]

[0048] Among them U bat Indicates that according to the voltage of the battery pack, U o Indicates the polarization voltage of the battery pack, R i Represents the ohmic internal resistance of the battery pack, R o represents the polarization resistance of the battery pack, and C represents the polarization capacitance of the battery pack.

[0049] Optionally, the regulated power ΔP of the electric propulsion load pro It can be obtained by fuzzy rules based on the solar array power and battery group SOC. The fuzzy rules are:

[0050]

[0051] Regulated power ΔP of electric propulsion load pro Superimposed reference power P pro0 , and the working power P of the electric propulsion load is obtained pro And the corresponding working position j pro .

[0052] Optionally, the target current of the battery pack is:

[0053]

[0054] Among them I * bat Indicates the target current of the battery pack.

[0055] Optionally, the process of implementing the MPC method for high-precision tracking of battery pack current includes:

[0056] The battery pack model is discretized, and the state space expression at time k is:

[0057]

[0058] in A a , B a , Ca is the coefficient matrix of the model, C a =

[11] , T ss is the sampling interval.

[0059] Set the prediction time domain to N p and control time domain is N c , the expression of the actual current Y(k) of the battery pack is:

[0060]

[0061] In the formula,

[0062]

[0063] C b =

[011]

[0064] Design objective function and constraints. The function of objective function J(k) is to track the battery current of the battery pack with high precision. The form is:

[0065]

[0066] Among them, Q represents the tracking weight, R represents the control weight, and Y ref Indicates the target current value I of the battery pack * bat , ε represents the relaxation factor, ρ represents the relaxation factor weight coefficient, and the state parameters and control variables are subject to the following constraints:

[0067]

[0068] Among them, U o,min and U o,max Respectively represent the minimum and maximum values ​​of polarization voltage; ΔSOC min and ΔSOC max Respectively represent the minimum and maximum value of SOC increment; I bat,min and I bat,max Respectively represent the minimum and maximum value of the battery pack current; U k o , ΔSOC k and I k bat They represent the polarization voltage, SOC increment and battery pack current at time k respectively.

[0069] In the solution provided by the embodiments of the present invention, a method and device for autonomous power distribution of a direct-drive electric propulsion power supply system for a spacecraft aim to achieve autonomous power distribution for the spacecraft, which can not only adjust the working gear of the electric propulsion load but also control the SOC of the battery pack within a safe range and extend its service life.

[0070] Embodiment 1

[0071] The method for autonomous power distribution of the direct-drive electric propulsion power supply system for a spacecraft in this embodiment is used to formulate a power distribution strategy for the power supply system of the spacecraft. As Figure 1 shown, the direct-drive electric propulsion power supply system for a spacecraft includes a solar array, a battery pack, a battery charge and discharge module, a low-voltage load, and an electric propulsion load; the solar array provides power for the low-voltage load and the electric propulsion load; the battery pack provides power for the low-voltage load and the electric propulsion load through the battery charge and discharge module; when the power provided by the solar array is greater than the power of the low-voltage load and the electric propulsion load, the battery pack can also absorb the excess power through the battery charge and discharge module; the electric propulsion load is a power discrete load with multiple gears; the autonomous power distribution module realizes the method for autonomous power distribution of the direct-drive electric propulsion power supply system for a spacecraft.

[0072] As Figure 2 shown, the method for autonomous power distribution of the direct-drive electric propulsion power supply system for a spacecraft in the embodiments of the present invention includes the following steps.

[0073] Step 1: Initialize and set the electric propulsion load, with a total of N gears from low to high in terms of power consumption, and the corresponding powers are P pro [1], …, P pro [j], ……, P pro [N], where 1 < j < N and j is an integer.

[0074] Step 2: Collect the power of the solar array, the current and voltage of the battery pack, and the power of the low-voltage load; calculate the reference power allocated to the electric propulsion load based on the power of the solar array and the low-voltage load, and determine the reference gear of the electric propulsion according to this power. The maximum power allocated to the electric propulsion load is:

[0075] P promax = P pv - P lowload

[0076] where P promax represents the maximum power that can be allocated to the electric propulsion load, P pv represents the power of the solar array, and P lowload represents the power of the low-voltage load. When the judgment condition is met, P pro [j - 1] < P promax ≤ P pro[j], the reference gear of the electric propulsion load is j, and the reference power of the electric propulsion load is P pro0 =P pro [j]; When the judgment conditions are met, P promax ≤P pro [1], the reference gear of the electric propulsion load is 1, and the reference power of the electric propulsion load is P pro0 =P pro [1]; When the judgment condition P is met promax >P pro [N], the reference gear of the electric propulsion load is N, and the reference power of the electric propulsion load is P pro0 =P pro [N].

[0077] Step 3: Based on the battery pack current and voltage, predict the SOC of the battery pack; the SOC of the battery pack is the state of charge, i.e., State of Charge. The formula for predicting the SOC of the battery pack is:

[0078]

[0079] SOC0 can be calculated based on the open circuit voltage U ocv , from the OCV-SOC curve, I bat represents the current of the battery pack, and Q0 represents the nominal capacity of the battery pack.

[0080] Open circuit voltage U of the battery pack ocv and current I bat The relationship between them is:

[0081]

[0082] Among them U bat Indicates that according to the voltage of the battery pack, U o Indicates the polarization voltage of the battery pack, R i Represents the ohmic internal resistance of the battery pack, R o represents the polarization resistance of the battery pack, and C represents the polarization capacitance of the battery pack.

[0083] Step 4: Set the solar array power P pv , battery pack SOC, input into the fuzzy rule table to obtain the regulation power ΔP of the electric propulsion load pro , the fuzzy rule table is

[0084]

[0085] Regulated power ΔP of electric propulsion load pro Superimposed reference power P pro0 , and the working power P of the electric propulsion load is obtainedpro And the corresponding working position j pro .

[0086] Step 5: Calculate the target current of the battery pack using the solar array power, low-voltage load power, and electric propulsion working power, and use the MPC method to achieve high-precision tracking of the battery pack current; the MPC method is model predictive control, whose English name is Model Predict Control.

[0087] Target current of the battery pack I * bat for:

[0088]

[0089] The process of implementing the MPC method for high-precision battery current tracking includes:

[0090] The battery pack model is discretized, and the state space expression at time k is:

[0091]

[0092] in A a , B a , C a is the coefficient matrix of the model, C a =

[11] , T ss is the sampling interval.

[0093] Set the prediction time domain to N p and control time domain is N c , the expression of the actual current Y(k) of the battery pack is:

[0094]

[0095] In the formula,

[0096]

[0097] C b =

[011]

[0098] Design objective function and constraints. The function of objective function J(k) is to track the battery current of the battery pack with high precision. The form is:

[0099]

[0100] Among them, Q represents the tracking weight, R represents the control weight, and Y ref Indicates the target current value I of the battery pack *bat , ε represents the relaxation factor, ρ represents the relaxation factor weight coefficient, and the state parameters and control variables are subject to the following constraints:

[0101]

[0102] Among them, U o,min and U o,max Respectively represent the minimum and maximum values ​​of polarization voltage; ΔSOC min and ΔSOC max Respectively represent the minimum and maximum value of SOC increment; I bat,min and I bat,max Respectively represent the minimum and maximum value of the battery pack current; U k o , ΔSOC k and I k bat They represent the polarization voltage, SOC increment and battery pack current at time k respectively.

[0103] The present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and when the computer instructions are executed on a computer, the computer executes Figure 2 The method described.

[0104] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0105] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0106] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0107] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0108] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0109] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for autonomously distributing electric energy for a spacecraft direct-drive electric propulsion power supply system, characterized in that: include: Initialize and set the electric spacecraft propulsion load, which is divided into several levels from low to high according to the power consumption; Collect spacecraft solar array power, battery current and voltage, and low-voltage load power; Calculate the reference power allocated to the electric propulsion load according to the solar cell array power and the low-voltage load power, and determine the reference gear position of the electric propulsion according to the reference power; Predict the SOC of the spacecraft battery pack based on the battery pack current and voltage; The regulating power of the electric propulsion load is obtained according to the power of the solar cell array and the SOC of the battery group, and the reference gear of the electric propulsion is superimposed to obtain the working power of the electric propulsion load and the corresponding working gear; The target current of the battery pack is calculated using the power of the solar cell array, the power of the low-voltage load and the working power of the electric propulsion load, and the current tracking of the battery pack is achieved.

2. The method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system according to claim 1, characterized in that: The maximum power of the electric propulsion load is P promax =P pv -P lowload ; Among them, P promax represents the maximum power that can be allocated to the electric propulsion load, P pv Represents the solar array power, P lowload Indicates low voltage load power.

3. The method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system according to claim 1, characterized in that: The electric spacecraft propulsion load has a total of N gears according to the increasing order of power consumption, and the corresponding powers are P pro [1], …, P pro [j], ……, P pro [N], where 1 < j < N and j is an integer; Determining the reference gear position of electric propulsion includes: When P pro [j-1] <P promax ≤P pro [j], the reference gear of the electric propulsion load is j, and the reference power of the electric propulsion load is P pro0 =P pro [j]; When P promax ≤P pro [1], the reference gear of the electric propulsion load is 1, and the reference power of the electric propulsion load is P pro0 =P pro [1]; When P promax >P pro [N], the reference gear of the electric propulsion load is N, and the reference power of the electric propulsion load is P pro0 =P pro [N]; P promax is the maximum power of the electric propulsion load.

4. The method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system according to claim 1, characterized in that: The battery pack SOC is Among them, SOC0 can be calculated based on the open circuit voltage U ocv , I bat represents the current of the battery pack, and Q0 represents the nominal capacity of the battery pack.

5. The method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system according to claim 4, characterized in that: The open circuit voltage U of the battery pack ocv and current I bat satisfy Among them, U bat Indicates that according to the voltage of the battery pack, U o Indicates the polarization voltage of the battery pack, R i Represents the ohmic internal resistance of the battery pack, R o represents the polarization resistance of the battery pack, and C represents the polarization capacitance of the battery pack.

6. The method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system according to claim 1, characterized in that: The regulating power of the electric propulsion load is obtained by fuzzy rules according to the solar array power and the battery group SOC.

7. The method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system according to claim 1, characterized in that: The target current of the battery pack is I * bat Indicates the target current of the battery pack, P pv Represents the solar array power, P lowload Indicates low voltage load power, P pro represents the maximum power that can be allocated to the electric propulsion load, U bat Indicates the voltage of the battery pack.

8. The method for autonomously distributing electric energy of a spacecraft direct-drive electric propulsion power supply system according to claim 1, characterized in that: The method for tracking the battery pack current is a model predictive control method.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

10. An autonomous electric energy distribution device for a spacecraft direct-drive electric propulsion power supply system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

Images