Improved ba-p&o hybrid algorithm based MPPT power supply control method for satellite

Abstract

An improved BA-P&O hybrid algorithm based MPPT power supply control method for a satellite, comprising: a solar cell array regulates bus voltage by means of a DC-DC unit to supply power to a load; a storage battery is connected to a bus by means of a diode to supply power to the load; a bat algorithm iteration stage and a perturbation observation stage are used for tracking the maximum power of the solar cell array when the solar cell array and the storage battery supply power together; a bus voltage regulation stage is used for maintaining the bus voltage stable when the solar cell array supplies power independently, and determining the update direction of the current duty ratio on the basis of the current bus voltage sampling value; and the three stages jump to each other on the basis of set conditions. The present invention is used for MPPT power supply control.

Description

Satellite MPPT power supply control method based on improved BA-P&O hybrid algorithm Technical Field

[0001] The present invention relates to a satellite MPPT power supply control method based on an improved BA-P&O hybrid algorithm, belonging to the technical field of on-board power supply control. Background Art

[0002] Based on the energy transmission method, onboard power systems are mainly divided into direct energy transfer (DET) and peak power point tracking (MPPT). DET is a dissipative system, using a shunt regulator to adjust the voltage and current output by the solar array. A space power control system based on peak power point tracking (MPPT) is a non-dissipative system. The MPPT algorithm within the controller outputs a control signal to control the series switching regulator to adjust the voltage. The MPPT algorithm can track the maximum power output of the solar panels. MPPT has higher energy conversion efficiency and does not require redundant design of the solar panels.

[0003] When temperature or light levels fluctuate, the DET power controller's solar array output power will be affected. The MPPT power controller tracks the current maximum output power of the solar array, preventing power loss. Furthermore, MPPT technology allows for more timely battery charging, reducing the depth of discharge and ultimately extending the satellite's operating life.

[0004] Analysis of the basic structure and power supply working mode of the space power system: As shown in Figure 1, the MPPT algorithm logic is implemented through hardware circuits or chip software, and the sampling circuit is used to collect the voltage and current of the solar cell as input. The output PWM is controlled by the drive circuit to control the DC-DC unit to achieve regulation of the solar array.

[0005] For space power systems that do not have strict requirements on bus voltage, a semi-regulated bus topology can be used. The battery does not use a discharge controller. During the earth shadow period, the battery is directly connected to the bus through a diode to supply power to the load. The circuit block diagram is shown in Figure 2.

[0006] According to the relationship between the output power of the solar array, the battery charging and discharging power, and the load power, the space power system has the following four operating modes: 1) MPPT and battery charging: The maximum output power of the solar array is greater than the load power, which can charge the battery and supply power to the load.

[0007] 2) MPPT and battery discharge: The maximum output power of the solar array is less than the load power, and it supplies power to the load together with the battery.

[0008] 3) Constant current charging of batteries: The maximum output power of the solar cell array is greater than the constant current charging power of the batteries and the load power, and can provide power for constant current charging of batteries and loads.

[0009] 4) Battery power supply: The spacecraft is located in the Earth's shadow and relies solely on batteries to power its loads.

[0010] In summary, when a spacecraft is in orbit, the MPPT unit switches between maximum power point tracking (MPPT) and voltage regulation control modes. The switch between power tracking and voltage regulation control modes depends on the relationship between the solar cell output power, the battery charge and discharge power, and the load power, and is typically determined by logic from the lower computer.

[0011] MPPT algorithm analysis: As shown in Figures 3 and 4, the power-voltage curve of the solar array under uniform illumination and temperature conditions is a single-peak curve. The algorithm mainly adjusts the busbar according to the changes in the output voltage and current of the solar array.

[0012] Traditional MPPT algorithms include constant voltage, perturbation-and-observe, conductance increment, and staggered perturbation. During on-orbit spacecraft operation, the output characteristics of multiple solar array strings may exhibit multi-peak characteristics due to local shading, uneven temperature and illumination, or damage to some solar cells. Traditional MPPT algorithms based on a single-peak model have poor global performance and are prone to being trapped in local peaks.

[0013] Heuristic algorithms such as swarm intelligence iterative algorithms, neural networks, and evolutionary algorithms generally do not require additional spacecraft external sensors and can effectively achieve global tracking of space solar arrays. Swarm intelligence iterative algorithms applied to MPPT include the particle swarm optimization (PSO), the grey wolf optimization (GWO), and the bat algorithm (BA). The bat algorithm is widely considered one of the best swarm intelligence iterative algorithms in terms of convergence time and avoiding premature convergence.

[0014] The BA algorithm has a small number of parameters, strong robustness, and fast convergence, making it suitable for tracking peak power of solar arrays on orbiting spacecraft. However, the basic BA algorithm lacks an effective mutation mechanism, and individuals are easily attracted to local extremes, leading to premature convergence. Therefore, the basic BA algorithm must strike a trade-off between convergence speed and convergence accuracy. Once iterative stabilization occurs, it cannot track new peak powers caused by environmental changes.

[0015] The swarm intelligence iterative algorithm will provide a feasible solution for maximum power output after convergence. After the swarm intelligence iterative algorithm completes its calculations, refining the solution with a traditional algorithm can yield a more accurate maximum power output. Compared to the basic bat algorithm, the BA-P&O two-stage MPPT algorithm demonstrates superior performance in dynamic environmental conditions.

[0016] Drawbacks of existing technologies: 1) Traditional MPPT algorithms can become stuck in local peaks, causing power loss. The basic bat algorithm lacks an effective mutation mechanism, and individuals are easily attracted to local extremes, leading to premature convergence. Furthermore, the bat algorithm requires a trade-off between convergence speed and accuracy. After the iterations stabilize, it cannot track new peak power generated by environmental changes. Existing BA-P&O two-stage hybrid algorithms can still become stuck in local peaks during the bat iteration phase due to overly rapid convergence.

[0017] 2) In space applications, the output capacity of spacecraft solar arrays will be affected by space radiation, which will cause a certain degree of attenuation and shift the position of the maximum power point. The initial position of the Bat Optimization Algorithm is randomly generated. Some improved Bat Algorithms used for photovoltaic MPPT use the global maximum power prediction point of the solar array as the initial position, without considering the lifetime of the solar array in orbit. The iterative search range is large, resulting in certain power losses.

[0018] 3) The duty cycle of swarm intelligent iterative algorithms such as the bat algorithm output to the DC-DC unit may suddenly change during the iteration process, causing certain oscillations in the bus voltage of the space power system.

[0019] 4) Improper restart conditions after the existing BA-P&O hybrid algorithm stabilizes may cause the algorithm to restart frequently or be trapped in a local peak for a long time, resulting in power loss.

[0020] 5) The algorithm lacks mode transition conditions. The transition between power tracking mode and voltage regulation mode depends on the relationship between the solar cell output power, the battery charge and discharge power, and the load power. This is often determined by the logic of the lower computer. This logic becomes complex when there are many loads and complex power relationships. Summary of the Invention

[0021] In order to solve the problem that the existing MPPT power supply control method based on BA-P&O may lead to premature convergence due to local extreme value attraction and poor bus voltage stability, the present invention provides a satellite MPPT power supply control method based on an improved BA-P&O hybrid algorithm.

[0022] The present invention discloses a satellite MPPT power supply control method based on an improved BA-P&O hybrid algorithm. A solar array regulates bus voltage to power a load through a DC-DC unit. A battery connects to the bus via a diode to power the load. Power supply control includes three phases: Bat algorithm iteration, disturbance observation, and bus voltage regulation. The Bat algorithm iteration and disturbance observation phases are used for maximum power tracking of the solar array when both the solar array and the battery are used for powering the load. In the iterative stage of the bat algorithm, the initial positions of a selected number of bat individuals are determined according to the voltage prediction values ​​at the maximum power points of the solar array at the beginning and end of its life and the working conditions of the spacecraft, as the initial duty cycle of the DC-DC unit, and the DC-DC unit is controlled by the driving circuit; if the bus voltage corresponding to the initial duty cycle is greater than the mode conversion voltage threshold, the bus voltage regulation stage is entered; otherwise, the greedy strategy is adopted to select the initial positions of half of the bat individuals that make the current power of the solar array larger under different working conditions, and the original positions are iteratively updated after random walk, and then the six updated duty cycles of the DC-DC unit are obtained by combining the reverse bat individual positions of the bat individual positions after the iterative update of the original positions, and the DC-DC unit is controlled by the driving circuit; if the bus voltage corresponding to the updated optimal duty cycle is greater than the mode conversion voltage threshold, the bus voltage regulation stage is entered; otherwise, three new iterative bat individuals are determined to continue the next position iterative update until the maximum number of iterations is reached; and the disturbance observation stage is entered; In the disturbance observation phase, the current actual power of the solar array is calculated based on the duty cycle position corresponding to the currently determined iterative bat individual, and the disturbance direction is determined according to the change in the current actual power and the actual power at the adjacent previous moment to perform duty cycle disturbance. After each use of the duty cycle after disturbance to control the DC-DC unit, if the bus voltage corresponding to the duty cycle after disturbance is greater than the mode conversion voltage threshold, the bus voltage regulation phase is entered. Otherwise, it is determined whether the restart condition is met based on the current actual power of the solar array and the current working time. If so, the bat algorithm iteration phase is entered. Otherwise, the current predicted power of the solar array is calculated based on the current duty cycle after disturbance and compared with the actual power to determine the disturbance direction and continue the duty cycle disturbance. The bus voltage regulation phase is used to maintain the bus voltage stability when the solar array is powered alone. The update direction of the current duty cycle is determined according to the current bus voltage sampling value. If the bus voltage corresponding to the updated duty cycle is still greater than the mode conversion voltage threshold, the bus voltage regulation is continued, otherwise the bat algorithm iteration phase is entered.

[0023] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, the parameters of the bat algorithm are first initialized in the bat algorithm iteration stage, and the maximum number of iterations is set to 1; the duty cycle range d in the bat algorithm iteration stage is: Where V bus is the bus voltage, V ocis the open-circuit voltage of the solar array; for individuals that exceed the duty cycle range d during iteration, the duty cycle is taken as the corresponding boundary value; six bat individuals are selected, and the method for determining the initial positions of the six bat individuals is: Where d1 to d6 are the initial positions of the six bats, V 初 is the predicted voltage value of the solar cell array at the maximum power point at the beginning of its life, V 末 is the predicted voltage value of the solar array at the maximum power point at the end of its life, is the search range proportional adjustment factor under high temperature conditions of the spacecraft, T H is the predicted average temperature of the solar array under high temperature conditions of the spacecraft, T L is the predicted average temperature of the solar array under low-temperature conditions of the spacecraft, is the search range proportional adjustment factor under low temperature conditions of the spacecraft, T ave It is the predicted average temperature of the solar array when the spacecraft is in orbit for a long time.

[0024] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, the method for iteratively updating the original position in the bat algorithm iteration phase is as follows: for the initial positions d1 to d6 of the six bat individuals, a greedy strategy is used to select them according to the current power of the corresponding solar arrays, and the initial positions of the three bat individuals with the largest current power under the same calculation rules are retained. Used in iterative processes; Where i represents the number of iterations, i = 1, 2, 3, ... I; is the speed of the three bat individuals in the i-th iteration, ω is the inertia weight, d best The optimal position for individual bats. is the pulse frequency of the three bat individuals in the i-th iteration, f min is the minimum pulse frequency of the bat, f max The maximum pulse frequency of the bat, β is a random number between (0, 1); The bat's random walk causes position changes, and the random walk formula is: In the formula is the new position of the three bat individuals in the i-th iteration who randomly walk based on their original positions, ε is the direction coefficient of the random walk, which is a random number between [-1, 1]. is the proportional adjustment coefficient of loudness, is the loudness of the three bat individuals in the i-th iteration; The condition for the random walk of the bat individual is: In the formula, rand1 represents a random number generated randomly between 0 and 1. represents the pulse emission rate of the k-th bat individual in the i-1th iteration, k = 1, 2, 3; for the bat individual that randomly walks, the new position of the random walk is The final individual bat position obtained in the current iteration process Complete the iterative update of the original position.

[0025] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, the method for obtaining the updated duty cycle of the iteratively updated DC-DC unit by combining the reverse bat individual position of the bat individual position after the iterative update of the original position is as follows: In the iterative update of i≤I / 2, the reverse learning mechanism is introduced to increase the search range, and the three bat individual positions after the i-th iterative update are The corresponding reverse bat individual position is for The conditions for updating the position of the corresponding bat individual are: and In the formula is the power of the solar array corresponding to the k-th bat individual in the i-th iteration, rand2 is a random number generated randomly between 0 and 1; is the loudness of the k-th bat individual in the i-1th iteration; If the position update condition is met, the bat individual in the retained position is updated to the new position, and the parameter update formula is: Where α is the loudness attenuation parameter, is the initial pulse emission rate of the three bat individuals, γ is the pulse emission rate enhancement parameter; is the pulse emission rate of the three bats in the i-th iteration; the individual bat positions obtained after the position update Individual positions of bats in reverse As the six updated duty cycles of the DC-DC unit in the current iteration process, the optimal duty cycle is determined.

[0026] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, in the bat algorithm iteration stage, the six updated duty cycles of the DC-DC unit are updated, and a greedy strategy is adopted to select the three bat individual positions corresponding to the larger solar array power for the next iterative update.

[0027] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, after each duty cycle is updated, the bus voltage V bus The relationship between the mode conversion voltage threshold and the mode conversion voltage threshold is as follows: V a =V bat +2, where Va is the mode switching voltage threshold, V bat is the maximum discharge voltage of the battery.

[0028] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, in the bat algorithm iteration stage, the six updated duty cycles of the DC-DC unit are updated in order from small to large when the previous duty cycle is updated, and are updated in order from large to small when the next duty cycle is updated.

[0029] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, in the disturbance observation phase, the calculation method of the current predicted power is: Where P F (t-1) is the predicted power at time t obtained when the duty cycle remains unchanged from time t-1, for The actual power at the moment, P(t-1) is the actual power at the moment t-1; In the disturbance observation phase, the optimal duty cycle finally determined in the iterative phase of the bat algorithm is used as the initial duty cycle of the DC-DC unit at the moment t-1, and the disturbance direction is determined according to the changes in the actual power P(t-1) at the moment t-1 and the actual power P(t-2) at the moment t-2; At the same time, the actual power P(t-1) at the moment t-1 and Actual power at the moment Predict the predicted power P at time t F (t-1); the duty cycle corresponding to the previous disturbance direction is used as the duty cycle of the DC-DC unit at time t, and then the actual power P(t) at time t and the predicted power P at time t are used to calculate the duty cycle of the DC-DC unit at time t. F (t-1) Determine the next disturbance direction and continue to perform duty cycle disturbance until the end.

[0030] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, the restart condition in the disturbance observation phase is set to meet one of the following conditions: 1) abs(P best -P(t))>Limit and T'>T a , where P best is the historical maximum power of the bat population in the iteration phase of the algorithm, Limit is the minimum power change for restarting the algorithm, T is the current working time in the disturbance observation phase, T a is the maximum stable duration of the disturbance observation phase; 2) T>T b , where T b is the maximum working time of the disturbance observation phase.

[0031] According to the satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm of the present invention, the DC-DC unit is implemented using a BUCK type step-down circuit.

[0032] The present invention has the following beneficial effects: The improved MPPT algorithm proposed by the present invention can meet the global requirements of power tracking, improve convergence accuracy, adapt to environmental changes caused by satellite operation, and enhance bus voltage stability. In practical applications, the present method can integrate power tracking and voltage regulation mode conversion logic into the same algorithm to adapt to space power systems with semi-regulated buses. The design of an independent MPPT electrical interface unit can meet the requirements of direct control by integrated electronic computers in micro-spacecraft.

[0033] The improved BA-P&O algorithm of this invention uses multiple individual bats to determine a globally stable and feasible solution during the BA phase. In the P&O phase, local dynamic updates are performed based on the feasible solution output from the BA phase. When the solar array power is sufficient, the algorithm can exit the BA or P&O phase and enter the bus voltage regulation phase, disabling battery power supply when the bus voltage exceeds a threshold. This invention combines the advantages of both the BA and P&O algorithms.

[0034] The MPPT algorithm improved by the method of the present invention meets the globality of maximum power point tracking, has good dynamic performance in adapting to environmental changes, and improves the stability of bus voltage. The bus regulation unit of the MPPT can be directly sampled and controlled by an integrated electronic computer, thereby improving the software integration of the integrated electronic computer.

[0035] The proposed method is a hybrid MPPT algorithm based on BA and P&O, adapting to multi-peak global power tracking. It improves convergence accuracy, enhances bus stability, and adapts to varying light levels during satellite operation. Its bus voltage-based operating mode conversion logic is reliable and simple to implement, reducing the number of independent electrical interfaces between the MPPT unit and the control computer. The MPPT independent electrical interface design accommodates direct control by the integrated power computer, allowing the MPPT algorithm to run on the satellite's integrated electronic computer, improving satellite software integration. A bypass design enhances power supply reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a typical circuit block diagram of a space power supply system based on MPPT; in the figure, PV_I is the output current sampling signal of the solar cell array, and PV_V is the output voltage sampling signal of the solar cell array; Figure 2 is a circuit block diagram of an MPPT space power supply system with a semi-regulated bus; Figure 3 is a single peak curve of a solar cell array under uniform illumination and temperature conditions; Figure 4 is a power-voltage curve of a solar cell array under uniform illumination and temperature conditions; Figure 5 is a flow chart of the iterative phase of the bat algorithm; Figure 6 is a flow chart of the disturbance observation phase; Figure 7 is a flow chart of the bus voltage regulation phase; Figure 8 is a circuit structure diagram of the control system of the method of the present invention; Figure 9 is a diagram of an MPPT unit and a bypass circuit; Figure 10 is a diagram of a bypass drive circuit; Figure 11 is a diagram of the output power curve of a solar cell array with multiple peak powers; Figure 12 is a diagram of the output power tracking curve of a solar cell array based on the improved BA-P&O algorithm, in which 83.32 represents the output power value. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0040] Specific embodiment 1, with reference to Figures 2, 5 to 7, the present invention proposes a satellite MPPT power supply control method based on an improved BA-P&O hybrid algorithm. The solar array regulates the bus voltage to supply power to the load through a DC-DC unit; the battery is connected to the bus through a diode to supply power to the load. The power supply control includes three stages: Bat algorithm iteration, disturbance observation, and bus voltage regulation. The Bat algorithm iteration stage and disturbance observation stage are used for maximum power tracking of the solar array when the solar array and the battery are jointly powered. In the iterative stage of the bat algorithm, the initial positions of a selected number of bat individuals are determined according to the voltage prediction values ​​at the maximum power points of the solar array at the beginning and end of its life and the working conditions of the spacecraft, as the initial duty cycle of the DC-DC unit, and the DC-DC unit is controlled by the driving circuit; if the bus voltage corresponding to the initial duty cycle is greater than the mode conversion voltage threshold, the bus voltage regulation stage is entered; otherwise, the greedy strategy is adopted to select half of the bat individuals that make the current power of the solar array larger under different working conditions, that is, the initial positions of three bat individuals, and the original positions are iteratively updated after random walk, and then the six updated duty cycles of the DC-DC unit are obtained by combining the reverse bat individual positions of the bat individual positions after the iterative update of the original positions, and the DC-DC unit is controlled by the driving circuit; if the bus voltage corresponding to the updated optimal duty cycle is greater than the mode conversion voltage threshold, the bus voltage regulation stage is entered; otherwise, three new iterative bat individuals are determined to continue the next position iterative update until the maximum number of iterations is reached; and the disturbance observation stage is entered; In the disturbance observation phase, the current actual power of the solar array is calculated based on the duty cycle position corresponding to the currently determined iterative bat individual, and the disturbance direction is determined according to the change in the current actual power and the actual power at the adjacent previous moment to perform duty cycle disturbance. After each use of the duty cycle after disturbance to control the DC-DC unit, if the bus voltage corresponding to the duty cycle after disturbance is greater than the mode conversion voltage threshold, the bus voltage regulation phase is entered. Otherwise, it is determined whether the restart condition is met based on the current actual power of the solar array and the current working time. If so, the bat algorithm iteration phase is entered. Otherwise, the current predicted power of the solar array is calculated based on the current duty cycle after disturbance and compared with the actual power to determine the disturbance direction and continue the duty cycle disturbance. The bus voltage regulation phase is used to maintain the bus voltage stability when the solar array is powered alone. The update direction of the current duty cycle is determined according to the current bus voltage sampling value. If the bus voltage corresponding to the updated duty cycle is still greater than the mode conversion voltage threshold, the bus voltage regulation is continued, otherwise the bat algorithm iteration phase is entered.

[0041] In this embodiment, the DC-DC unit (MPPT voltage regulation unit) has two main functions: one is to maintain bus voltage stability when the solar array power is large enough to provide power alone; the other is to track the maximum power of the solar array when the solar array power is not large enough and the battery and solar array need to be jointly powered.

[0042] Furthermore, in the iteration stage of the bat algorithm, the parameters of the bat algorithm are first initialized, and the maximum number of iterations is set to I; the loudness is A, the frequency is r, etc.

[0043] After parameter initialization, the bat swarm is initialized, and the duty cycle of the BUCK circuit corresponding to the number of bats and their initial positions is determined. For a semi-regulated bus-based spatial power system, batteries are directly connected to the bus via diodes to power the load. To minimize power loss during the iterations of the bat swarm algorithm, the duty cycle range of the iterations is determined based on the bus voltage. For individuals that exceed the duty cycle range during the iteration, the duty cycle is set to the boundary value.

[0044] The duty cycle range d in the iterative stage of the bat algorithm is: Where V bus is the bus voltage, V oc is the open-circuit voltage of the solar array. For individuals that exceed the duty cycle range d during iteration, the duty cycle is set to the corresponding boundary value. To accelerate convergence and avoid local peaks, the initial positions of some bat individuals should be as close as possible to the maximum power point. For space power systems, the power output characteristics of the solar array will vary significantly due to the impact of space radiation on the lifespan, and the maximum power point will change between the early and late lifespans. Therefore, considering the performance of the solar cells and the operating temperature, six bat individuals were selected. The initial positions of the six bat individuals were determined as follows: Where d1 to d6 are the initial positions of the six bats, V 初 is the predicted voltage value of the solar cell array at the maximum power point at the beginning of its life, V 末 is the predicted voltage value of the solar array at the maximum power point at the end of its life, is the search range proportional adjustment factor under high temperature conditions of the spacecraft, T H is the predicted average temperature of the solar array under high temperature conditions of the spacecraft, T L is the predicted average temperature of the solar array under low-temperature conditions of the spacecraft, is the search range proportional adjustment factor under low temperature conditions of the spacecraft, T ave It is the predicted average temperature of the solar array when the spacecraft is in orbit for a long time.

[0045] In this embodiment, the method for iteratively updating the original position in the iteration phase of the bat algorithm is as follows: The duty cycle of the initial position of the bat is brought into the DC-DC unit, and the power corresponding to each initial bat is recorded. The individual bats at the initial and final stages at the same temperature are selected using a greedy strategy, that is, the initial positions d1 to d6 of the six individual bats are selected using a greedy strategy according to the current power of the corresponding solar arrays, and the initial positions of the three bat individuals with the largest current power under the same calculation rules are retained. Used in iterative processes; Where i represents the number of iterations, i = 1, 2, 3, ... I; is the speed of the three bat individuals in the i-th iteration, ω is the inertia weight, d best The optimal position for individual bats. is the pulse frequency of the three bat individuals in the i-th iteration, between [0, 1], f min is the minimum pulse frequency of the bat, f max The maximum pulse frequency of the bat, the pulse frequency should gradually increase during the iteration; β is a random number between (0, 1); The bat's random walk causes position changes, and the random walk formula is: In the formula is the new position of the three bat individuals in the i-th iteration who randomly walk based on their original positions, ε is the direction coefficient of the random walk, which is a random number between [-1, 1]. is the proportional adjustment coefficient of loudness, which can control the random walk step size; is the loudness of the three bat individuals in the i-th iteration; The condition for the random walk of the bat individual is: In the formula, rand1 represents a random number generated randomly between 0 and 1. represents the pulse emission rate of the k-th bat individual in the i-1th iteration, k = 1, 2, 3; for the bat individual that randomly walks, the new position of the random walk is The final individual bat position obtained in the current iteration process Complete the iterative update of the original position.

[0046] Furthermore, the method of obtaining the updated duty cycle of the iteratively updated DC-DC unit by combining the reverse bat individual position of the bat individual position after the iterative update of the original position is as follows: In the early iteration process, in order to avoid falling into the local peak, the reverse learning mechanism is introduced to increase the search range. In the iterative update of i≤I / 2, the three bat individual positions after the i-th iteration update are The corresponding reverse bat individual position is Record and The corresponding maximum power and the optimal duty cycle are determined; The conditions for updating the position of the corresponding bat individual are: and In the formula is the power of the solar array corresponding to the k-th bat individual in the i-th iteration, rand2 is a random number generated randomly between 0 and 1; is the loudness of the k-th bat individual in the i-1th iteration; If the position update condition is met, the bat individual in the retained position is updated to the new position, and the parameter update formula is: Where α is the loudness attenuation parameter, is the initial pulse emission rate of the three bat individuals, γ is the pulse emission rate enhancement parameter; is the pulse emission rate of the three bats in the i-th iteration; the individual bat positions obtained after the position update Individual positions of bats in reverse As the six updated duty cycles of the DC-DC unit in the current iteration process, the optimal duty cycle is determined according to the corresponding maximum power.

[0047] The loudness A tends to decrease, while the pulse emission rate r increases. A larger loudness A improves the global search capability of the iteration, while a larger r improves the local optimization capability of the iteration. The values ​​γ = 0.9 and α = 0.9 are suitable.

[0048] During the iteration phase of the bat algorithm, a greedy strategy is used to select the positions of the three bat individuals with the highest solar array power for the next iteration of the six updated duty cycles of the DC-DC units. A greedy strategy is used to select the positions of the original bat individuals and their corresponding reversed individuals, retaining the optimal individual positions for the next iteration. Therefore, the number of bat individuals retained in each iteration is always three.

[0049] The DC-DC unit of the MPPT of the semi-regulated bus space power system has the function of regulating the bus voltage. Therefore, after updating the duty cycle to the DC-DC unit each time, the bus voltage V bus The relationship between the mode conversion voltage threshold and the mode conversion voltage threshold is as follows: V a =V bat +2, where V a is the mode switching voltage threshold, V bat is the maximum discharge voltage of the battery.

[0050] If the bus voltage V bus Greater than the mode switching voltage threshold V a , then enter the bus voltage regulation mode. To reduce battery discharge during the voltage regulation process, the mode conversion voltage threshold should be slightly higher than the maximum discharge voltage of the battery.

[0051] If the bus voltage V bus Less than the mode switching voltage threshold V a , then continue the bat group iteration process.

[0052] In the iteration phase of the bat algorithm, the six updated duty cycles of the DC-DC unit are updated in the order from small to large when the previous duty cycle is updated, and are updated in the order from large to small when the next duty cycle is updated.

[0053] Because some loads are directly connected to the bus, bus voltage fluctuations should be minimized. To reduce the impact of sudden duty cycle changes on the bus voltage, the bat positions are individually sorted during the iteration process before outputting the duty cycle. Without affecting the algorithm's intelligent iteration capabilities, the duty cycle can be output in ascending order for odd-numbered position updates and in descending order for even-numbered updates.

[0054] When the number of iterations reaches the set maximum number of iterations I, the iterative process is exited and the disturbance observation phase is entered.

[0055] Furthermore, during the perturbation observation phase, after the perturbation observation phase is initiated, the initialization time parameter determines the perturbation observation duration. The perturbation observation phase perturbs the solar array voltage by increasing or decreasing the duty cycle. The perturbation direction is determined based on the power change. If the post-perturbation power is greater than the pre-perturbation power, the perturbation direction is maintained; otherwise, the perturbation direction is reversed.

[0056] Since the traditional perturbation observation method may make misjudgments when the lighting environment changes, this embodiment adopts the perturbation observation method of power prediction. The power judgment of the perturbation observation method of power prediction is calculated by adding one sampling to the predicted power value P. F The difference between (t-1) and the current actual power value P(t) eliminates the influence of environmental changes.

[0057] The current predicted power is calculated as: Where P F (t-1) is the power predicted when the duty cycle remains unchanged from time t-1. for The actual power at the moment, P(t-1) is the actual power at the moment t-1; In the disturbance observation phase, the optimal duty cycle finally determined in the iterative phase of the bat algorithm is used as the initial duty cycle of the DC-DC unit at the moment t-1, and the disturbance direction is determined according to the changes in the actual power P(t-1) at the moment t-1 and the actual power P(t-2) at the moment t-2; At the same time, the actual power P(t-1) at the moment t-1 and Actual power at the moment Predict the predicted power P at time t F (t-1); the duty cycle corresponding to the previous disturbance direction is used as the duty cycle of the DC-DC unit at time t, and then the actual power P(t) at time t and the predicted power P at time t are used to calculate the duty cycle of the DC-DC unit at time t. F(t-1) Determine the next disturbance direction and continue to perform duty cycle disturbance until the end.

[0058] The duty cycle of the disturbance observation link is brought into the BUCK voltage regulation unit to determine the relationship between the bus voltage and the mode conversion voltage threshold. The mode conversion voltage threshold should be at least greater than the maximum discharge voltage of the battery. If the bus voltage is greater than the threshold voltage V a , then enter the bus voltage regulation mode. If the bus voltage is less than the threshold voltage, continue to perturb.

[0059] In this embodiment, the restart condition in the disturbance observation phase is set to satisfy one of the following conditions: 1) abs(P best -P(t))>Limit and T>T a , where P best is the historical maximum power of the bat population in the iteration phase of the algorithm, Limit is the minimum power change for restarting the algorithm, T is the current working time in the disturbance observation phase, T a The maximum stable duration of the disturbance observation phase; after the disturbance observation phase is stable, it has a certain tracking ability for illumination changes. If the power changes significantly, the algorithm will be restarted.

[0060] 2) To prevent the algorithm from being stuck in a local peak for a long time, a periodic restart of the algorithm is added to judge the time of the disturbance link to determine whether the bat swarm algorithm needs to be restarted. The judgment condition is: T>T b , where T b is the maximum working time of the disturbance observation phase.

[0061] In the bus voltage regulation stage, the duty cycle adjustment depends only on the bus voltage. When the bus voltage is higher than V a When the duty cycle is reduced, it is lower than V a When the bus voltage is lower than V bat When the bat swarm algorithm is restarted, it enters the power tracking mode.

[0062] As an example, the DC-DC unit is implemented using a BUCK type step-down circuit.

[0063] The control circuit design of the present invention's method involves a semi-regulated bus-based space power system, in which the MPPT unit samples bus voltage. The sampled bus voltage is input into the satellite's integrated electronic computer, and an electrical interface is designed to enable direct control of the MPPT unit by the integrated computer. The MPPT algorithm can then be run directly on the integrated computer.

[0064] As shown in Figure 8, the corresponding electrical interface provides three sampling signals: the solar array output voltage, the solar array output current, and the bus voltage; two complementary PWM waveforms; and a bypass switch control signal. The integrated electronic computer can control the MPPT unit via a separate electrical interface. For small satellites such as CubeSats, the integrated electronic computer and MPPT unit can be directly connected via a connector, supporting high-frequency PWM control.

[0065] As shown in Figure 9, the busbar regulation DC-DC unit uses a synchronous rectification buck circuit with an added bypass design adapted for integrated electronic computer control. S1 and S2 in the buck circuit are two NMOS transistors driven by a half-bridge driver chip. S3 is a PMOS transistor. If the MPPT circuit or integrated power computer fails, it automatically switches to bypass mode, connecting the solar array output directly to the busbar to ensure power supply for the entire satellite.

[0066] As shown in Figure 10, the bypass switch is directly controlled by the satellite's integrated electronic computer. To ensure power to the entire satellite in the event of an unexpected shutdown of the integrated electronic computer, a pull-down resistor is connected to the chip pin corresponding to the bypass switch signal. The bypass switch circuit is designed so that when the signal is high, the bypass switch is closed, and when the signal is low, the bypass switch is open. The bypass switch drive signal is directly supplied by the solar array output voltage via a resistor divider, improving reliability.

[0067] The integrated electronic computer controls the bypass switch via high and low voltage levels. When using the MPPT function, the bypass switch's corresponding pin always outputs a high voltage level. If the integrated electronic computer unexpectedly shuts down, the corresponding pin outputs a low voltage level, turning on the bypass switch. The solar array will be directly connected to the busbar for power supply, improving power supply reliability.

[0068] Simulation Verification: Simulations based on SIMULINK were performed to verify the performance of the improved BA-P&O hybrid algorithm. The modeling and output characteristics of a multi-peak power solar array are shown in Figure 11. The simulated solar array output power curve is shown in Figure 12.

[0069] This shows that the improved BA-P&O algorithm of the present invention can avoid falling into local peaks, reduce voltage oscillations, reduce the impact of duty cycle mutations on bus voltage, and has a faster convergence time.

[0070] Application scenarios for the method of this invention: LEO satellites have short cycles and rapidly alternating light and shadow zones. Battery charging time is short during in-orbit operation. Increasing the output power of the solar array can shorten charging time. An MPPT-based space power control system can better meet mission requirements. Deep space probes experience wide variations in solar array output power between the early and late stages of their in-orbit lifespan, and many of these probes employ MPPT technology.

[0071] The present invention is applicable to a semi-regulated bus power supply system of a micro-sized spacecraft.

[0072] In the improved BA phase, the present method selects the initial positions of individual bats based on the on-orbit operating life of the solar cells. Backward learning is introduced to improve convergence and the ability to escape local peaks. The iteration order of the bat swarm is improved, and individuals are sorted after each round of iteration, minimizing the impact of sudden duty cycle changes on the bus voltage.

[0073] Improved Perturbation Observation Phase: Introduces power prediction to improve power tracking accuracy. Two restart conditions, time and power, are set. The MPPT algorithm can be restarted when there are significant changes in light and temperature. To prevent the MPPT from being stuck in a local peak for extended periods, resulting in prolonged power loss, the algorithm is restarted after a period of time in the Perturbation Observation Phase.

[0074] Algorithm design based on bus voltage: Initial bat individual selection is set based on bus voltage. The MPPT algorithm adds mode transition judgment based on bus voltage. The mode transition logic is simple and easy to implement. The algorithm independently implements bus voltage regulation and power tracking functions.

[0075] MPPT independent electrical interface and bypass design: Six independent electrical interfaces are designed to accommodate MPPT units directly controlled by the on-orbit integrated electronic computer. Given the compact size of micro-spacecraft, the integrated electronic computer independently controls the MPPT units by outputting high-frequency PWM waves via connectors or short-distance cables. The MPPT algorithm can run on the integrated electronic computer, improving software integration. A bypass design is also designed to accommodate on-orbit integrated electrical disconnects or MPPT failures, enhancing power supply reliability.

[0076] This method considers the variations in solar cell lifetime during orbital operation when selecting individual bat positions in the BA algorithm. Backward learning and individual ranking during the BA phase improve algorithm convergence and bus stability. Power prediction and timed restart conditions are introduced to improve the disturbance observation phase. Mode switching is based on bus voltage. This simplifies the mode switching logic and adapts to semi-regulated bus power systems. MPPT independent electrical interface and bypass designs are also supported.

[0077] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A satellite MPPT power supply control method based on an improved BA-P&O hybrid algorithm, characterized in that: The solar cell array regulates the bus voltage through the DC-DC unit to supply power to the load; the battery is connected to the bus through a diode to supply power to the load; Power supply control includes three stages: bat algorithm iteration, disturbance observation, and bus voltage regulation; The bat algorithm iteration phase and disturbance observation phase are used for maximum power tracking of solar arrays when solar arrays and batteries are jointly powered; The bat algorithm iteration phase determines the initial positions of a selected number of bats based on the voltage prediction values ​​at the maximum power points of the solar array at the beginning and end of its life and the spacecraft operating conditions. This is used as the initial duty cycle of the DC-DC unit, which is then controlled via the drive circuit. If the bus voltage corresponding to the initial duty cycle is greater than the mode conversion voltage threshold, the bus voltage regulation stage is entered; otherwise, a greedy strategy is used to select the initial positions of half of the bat individuals that make the current power of the solar array larger under different working conditions and perform random walks and then iteratively update the original positions. Then, the six updated duty cycles of the DC-DC unit are obtained by combining the reverse bat individual positions of the bat individual positions after the iterative update of the original positions, and the DC-DC unit is controlled by the driving circuit; if the bus voltage corresponding to the updated optimal duty cycle is greater than the mode conversion voltage threshold, the bus voltage regulation stage is entered; otherwise, three new iterative bat individuals are determined to continue the next position iterative update until the maximum number of iterations is reached; then the disturbance observation stage is entered; In the disturbance observation phase, the current actual power of the solar array is calculated based on the duty cycle position corresponding to the currently determined iterative bat individual, and the disturbance direction is determined according to the change between the current actual power and the actual power at the previous moment to perform duty cycle disturbance. Each time the DC-DC unit is controlled using the duty cycle after the disturbance, if the bus voltage corresponding to the duty cycle after the disturbance is greater than the mode conversion voltage threshold, the bus voltage regulation phase is entered; otherwise, the restart condition is determined based on the current actual power of the solar array and the current working time. If so, the bat algorithm iteration phase is entered; otherwise, the current predicted power of the solar array is calculated based on the current duty cycle after the disturbance and compared with the actual power to determine the disturbance direction and continue the duty cycle disturbance; The bus voltage regulation stage is used to maintain the bus voltage stability when the solar array is powered alone. The update direction of the current duty cycle is determined according to the current bus voltage sampling value. If the corresponding bus voltage after the duty cycle is updated is still greater than the mode conversion voltage threshold, the bus voltage regulation continues, otherwise it enters the bat algorithm iteration stage.

2. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 1 is characterized in that: In the iterative phase of the bat algorithm, the parameters of the bat algorithm are first initialized, and the maximum number of iterations is set to 1; The duty cycle range d in the iterative stage of the bat algorithm is: Where V bus is the bus voltage, V oc is the open circuit voltage of the solar cell array; For individuals that exceed the duty cycle range d during iteration, the duty cycle is taken as the corresponding boundary value; Six bat individuals are selected, and the method for determining the initial positions of the six bat individuals is: Where d1 to d6 are the initial positions of the six bats, V 初 is the predicted voltage value of the solar cell array at the maximum power point at the beginning of its life, V 末 is the predicted voltage value of the solar array at the maximum power point at the end of its life, is the search range proportional adjustment factor under high temperature conditions of the spacecraft, T H is the predicted average temperature of the solar array under high temperature conditions of the spacecraft, T L is the predicted average temperature of the solar array under low-temperature conditions of the spacecraft, is the search range proportional adjustment factor under low temperature conditions of the spacecraft, T ave It is the predicted average temperature of the solar array when the spacecraft is in orbit for a long time.

3. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 2 is characterized in that: The method for iteratively updating the original position in the iterative phase of the bat algorithm is: The initial positions d1 to d6 of the six bat individuals are selected using a greedy strategy based on the current power of the corresponding solar arrays, and the initial positions of the three bat individuals with the largest current power under the same calculation rules are retained. Used in iterative processes; Where i represents the number of iterations, i = 1, 2, 3, ... I; is the speed of the three bat individuals in the i-th iteration, ω is the inertia weight, d best The optimal position for individual bats. is the pulse frequency of the three bat individuals in the i-th iteration, f min is the minimum pulse frequency of the bat, f max The maximum pulse frequency of the bat, β is a random number between (0, 1); The random walk of bats causes position changes. The random walk formula is: In the formula is the new position of the three bat individuals in the i-th iteration who randomly walk based on their original positions, ε is the direction coefficient of the random walk, which is a random number between [-1, 1]. is the proportional adjustment coefficient of loudness, is the loudness of the three bat individuals in the i-th iteration; The conditions for individual bats to walk randomly are: In the formula, rand1 represents a random number generated randomly between 0 and 1. represents the pulse emission rate of the k-th bat individual in the i-1th iteration, k = 1, 2, 3; for the bat individual that randomly walks, the new position of the random walk is The final individual bat position obtained in the current iteration process Complete the iterative update of the original position.

4. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 3 is characterized in that: The method of obtaining the updated duty cycle of the iteratively updated DC-DC unit by combining the reverse bat individual position of the bat individual position after iterative update of the original position is: In the iterative update of i≤I / 2, the reverse learning mechanism is introduced to increase the search range. The positions of the three bat individuals after the i-th iterative update are The corresponding reverse bat individual position is for The conditions for updating the position of the corresponding bat individual are: and In the formula is the power of the solar array corresponding to the k-th bat individual in the i-th iteration, rand2 is a random number generated randomly between 0 and 1; is the loudness of the k-th bat individual at the i-1th iteration; If the position update condition is met, the bat individual at the reserved position will be updated to the new position. The parameter update formula is: Where α is the loudness attenuation parameter, is the initial pulse emission rate of the three bat individuals, γ is the pulse emission rate enhancement parameter; is the pulse emission rate of the three bats in the i-th iteration; The individual bat position obtained after the position update Individual positions of bats in reverse The six updated duty cycles of the DC-DC unit in the current iteration process are used to determine the optimal duty cycle.

5. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 44, characterized in that: In the iterative stage of the bat algorithm, the six updated duty cycles of the DC-DC unit are updated, and a greedy strategy is used to select the three individual bat positions corresponding to the larger solar array power for the next iterative update.

6. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 5 is characterized in that: After each duty cycle update, the bus voltage V bus The relationship between the mode conversion voltage threshold and the mode conversion voltage threshold is as follows: V a =V bat +2, Where V a is the mode switching voltage threshold, V bat is the maximum discharge voltage of the battery.

7. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 6 is characterized in that: In the iteration phase of the bat algorithm, the six updated duty cycles of the DC-DC unit are updated in the order from small to large when the previous duty cycle is updated, and are updated in the order from large to small when the next duty cycle is updated.

8. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 7 is characterized in that: During the disturbance observation phase, the current predicted power is calculated as: Where P F (t-1) is the predicted power at time t obtained when the duty cycle remains unchanged from time t-1, for The actual power at the moment, P(t-1) is the actual power at the moment t-1; In the disturbance observation phase, the optimal duty cycle finally determined in the iterative phase of the bat algorithm is used as the initial duty cycle of the DC-DC unit at time t-1. The disturbance direction is determined according to the changes in the actual power P(t-1) at time t-1 and the actual power P(t-2) at time t-2. At the same time, the actual power P(t-1) at time t-1 and Actual power at the moment Predict the predicted power P at time t F (t-1); the duty cycle corresponding to the previous disturbance direction is used as the duty cycle of the DC-DC unit at time t, and then the actual power P(t) at time t and the predicted power P at time t are used to calculate the duty cycle of the DC-DC unit at time t. F (t-1) Determine the next disturbance direction and continue to perform duty cycle disturbance until the end.

9. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 8, characterized in that: The restart condition in the disturbance observation phase is set to meet one of the following conditions: 1)abs(P best -P(t))>Limit and T>T a , Where P best is the maximum power of the bat population in the iteration phase, Limit is the minimum power change for restarting the algorithm, T is the current working time in the disturbance observation phase, T a is the maximum stable duration of the disturbance observation phase; 2)T>T b , Where T b is the maximum working time of the disturbance observation phase.

10. The satellite MPPT power supply control method based on the improved BA-P&O hybrid algorithm according to claim 9 is characterized in that: The DC-DC unit is implemented using a BUCK type step-down circuit.

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