Spacecraft power control circuit and method

Abstract

The application provides a spacecraft power supply control circuit and method, which are used for realizing MPPT control and shunt control functions of a spacecraft power supply. The control strategy in the application is based on a double-tube buck circuit, which is composed of an MPPT circuit, a PI regulator, a hysteresis comparator, a comparator, an amplitude switching circuit, a PWM circuit, an OR gate and a driver. The application realizes the combination of MPPT control and shunt control by using an analog circuit control mode, and realizes the autonomous control of power supply state switching by using a hardware circuit mode.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft power supply and relates to a spacecraft power supply control circuit and method. Background Technology

[0002] Spacecraft power supplies typically use either MPPT (Maximum Power Point Tracking) or shunt regulation. MPPT enables the energy generated by solar cells to be transferred at maximum power, while shunt regulation offers advantages such as high transfer efficiency, solar cell voltage clamping, and simple control.

[0003] Since spacecraft are mostly powered by solar cells, their output voltage increases when the spacecraft enters or exits the shadow period due to the characteristics of the solar cells. A control method combining MPPT (Multi-Level Pressure Test) and shunt regulation is often used to address this issue by modifying the circuit topology and combining it with lower-level software control. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a spacecraft power control circuit. This spacecraft power supply uses a dual-tube buck circuit as the power circuit. The input is connected to the solar cell array, and the output is connected to the battery through a diode. By using hardware control, the problem of the solar cell voltage rising when the satellite enters or exits the shadow period is solved.

[0005] The technical solution of this invention is: a spacecraft power control circuit, comprising: a power circuit, a driver S1, a driver S2, an OR gate, a PWM circuit, an MPPT circuit, a PI regulator, a small-scale circuit, a limiting switching circuit, a first hysteresis comparator, a second hysteresis comparator, a comparator, and an integrator; the MPPT circuit acquires the voltage VSA and current ISA of the solar cell SA1 and generates an MPPT control voltage signal Ref; the control voltage signal Ref output by the MPPT circuit is subtracted from the voltage VSA of the solar cell SA1 to generate an error signal E1; the error signal E1 is processed by the PI regulator to generate a control voltage signal V1, which is sent to the small-scale circuit; the first hysteresis comparator acquires the voltage signal VBat of the battery BAT and generates an output voltage signal V4 for the integrator; the integrator integrates the input voltage signal V4 and transmits the generated output voltage signal V5 to the integrator. The circuit uses a small circuit and a second hysteresis comparator. The second hysteresis comparator receives the output voltage signal V5 and generates the output voltage signal V7. The small circuit receives the control voltage signal V1 and the control voltage signal V5 and generates the output voltage signal V2. The comparator acquires the voltage signal VBat of the battery BAT, generates the output voltage signal V5, and transmits it to the limiting switching circuit. The limiting switching circuit receives the voltage signals V2 and V6 and generates the control voltage signal V3. The PWM circuit receives the input of the control voltage signal V3 and generates two PWM signals, namely PWM1 and PWM2. The PWM1 signal and the output voltage signal V7 are input together to an OR gate and generate the drive voltage signal PWMT1. The drive voltage signal PWMT1 is input to the drive S1 to generate the control voltage signal to control the circuit. The drive voltage signal PWM2 is input to the drive S2 to generate the control voltage signal, and the control circuit operates.

[0006] The power circuit includes: a solar cell array SA1, an input capacitor C1, a switching transistor T1, a shunt transistor T2, an inductor L1, an output diode D1, and a battery BAT. The solar cell array SA1 serves as the energy source for the spacecraft's power control circuit, providing input energy. The energy generated by the solar cell array SA1 is filtered by the input capacitor C1 and then reaches the switching transistor T1. Switches T1 and T2 alternately conduct, and inductor L1 stores energy. Together, these three components form a step-down circuit. The node connecting the switching transistor T1 and the input capacitor is the input of the step-down circuit, and the node connecting the inductor L1 and the output diode D1 is the output of the step-down circuit. This circuit converts the high voltage on the input capacitor C1 into a low voltage at the right-side port of inductor L1. The energy output from inductor L1 is transferred to the battery BAT via the output diode D1. The battery BAT serves as an energy storage device, storing the energy generated by the solar cell array SA1 and transformed through the input capacitor C1, switching transistor T1, shunt transistor T2, inductor L1, and output diode D1.

[0007] The power circuit includes: the MPPT circuit is the hardware logic circuit required to implement the MPPT perturbation algorithm.

[0008] The drive S1 and drive S2 convert the PWM control signal into a drive signal and control the switching on and off of the switching transistors T1 and T2.

[0009] The power circuit includes: the error signal E1 is processed by a PI regulator, specifically: the error signal E1 is subjected to proportional-integral operation.

[0010] The limiting switching circuit includes a Zener diode 1, a Zener diode 2, and a switch 1. When the switch 1 is open, the Zener diode 1 operates; when the switch 1 is closed, the Zener diode 2 operates.

[0011] The function of the first hysteresis comparator, the second hysteresis comparator, and the comparator is to reverse the output state when the input voltage exceeds a fixed threshold.

[0012] A spacecraft power control circuit control method, comprising:

[0013] (1) When the satellite is operating during the sunshine period:

[0014] When operating in MPPT mode, the battery voltage VBat > comparator voltage threshold Vref1, and switch 1 in the comparator control limiting switching circuit is open.

[0015] When the battery voltage VBat < the first hysteresis comparator voltage threshold Vref3, voltage signals V4 and V5 are both high, while the output of the second hysteresis comparator is low. At this time, the output voltage signal V2 = V1 of the small circuit is taken, and the MPPT loop works; while PWMT1 = PWM1, the switching transistor T1 and the shunt transistor T2 work in the PWM complementary state.

[0016] As the battery continues to charge, its voltage rises. When the battery voltage VBat > the first hysteresis comparator's voltage threshold Vref3, the first hysteresis comparator outputs a low level, the integrator's output voltage signal V5 begins to decrease, and the output voltage signal of the small circuit switches from V1 to V5, eventually dropping to 0. At this time, the second hysteresis comparator remains unchanged, the PWM circuit's input voltage signal V3 decreases, the PWM1 duty cycle gradually decreases to 0, and the PWM2 duty cycle increases to 100%. Switch T1 is completely turned off, and shunt T2 is turned on.

[0017] When the voltage signal V5 drops to its lowest point, the output voltage signal V7 of the second hysteresis comparator is reversed and outputs a high level. At this time, the switching transistor T1 is fully turned on, the solar cell array SA1 is directly connected to ground, and the circuit enters the shunt state.

[0018] (2) When the satellite is in shadow:

[0019] As the satellite enters its shadow period, the battery begins to discharge, and the battery voltage VBat continuously decreases.

[0020] When the battery voltage drops to VBat < the first hysteresis comparator voltage threshold Vref2, the first hysteresis comparator output is high, and the small circuit output voltage signal V2 = V1 is taken. The circuit starts to work in MPPT state, while the second hysteresis comparator output becomes low.

[0021] When the battery voltage drops to VBat < comparator voltage threshold Vref1, switch 1 of the limiting switching circuit closes, and the voltage signal V3 limit value increases; the PI output is at its maximum value, the duty cycle of the PWM circuit output reaches 100%, the switching transistor T1 is in the conducting state, and the shunt transistor T2 is in the off state; since the solar array voltage VSA is 0 at this time, diode D1 is reverse cut off.

[0022] (3) When the satellite transitions from shadow period to light period:

[0023] When the solar array voltage VSA increases and the solar cell voltage VSA > the battery voltage VBat, D1 conducts. When the solar cell array voltage VSA = the battery voltage VBat, the MPPT circuit output voltage signal Ref rises slowly, and the circuit still operates in the shoot-through state.

[0024] As the MPPT circuit output Ref increases, the circuit begins to operate in MPPT regulation mode;

[0025] When the battery voltage VBat > comparator voltage Vref1, the limiting switching circuit works, the voltage signal V3 limiting value decreases, and the circuit completes one working cycle.

[0026] When a satellite is working in space, it completes one working cycle from (1) to (3) every time it orbits the Earth.

[0027] The advantages of this invention compared to existing technologies are as follows: Existing technologies typically add multiple power diodes or power MOSFETs to the original topology to enable the circuit to achieve MPPT and shunt functions, thereby enabling the solar cell to shunt to ground. In contrast, this invention is based on a dual-tube buck circuit and only connects one power diode in series at the output, which greatly simplifies the power circuit.

[0028] In order to achieve the switching of MPPT and current shunting functions simultaneously, existing technologies usually require external control signals to achieve the function switching. However, the present invention does not rely on external lower-level machines and software algorithms for control. The hardware circuit itself can achieve the switching of MPPT and current shunting functions, realizing the autonomous control of the circuit itself and improving the reliability of the circuit operation.

[0029] Existing technologies using MPPT and shunt circuits typically have two independent control loops. The control loops are switched via software-controlled logic gates to achieve function switching. In contrast, this invention uses only one control loop and employs hardware logic gates to achieve flexible switching of circuit functions, eliminating stability issues caused by sudden changes in circuit state when switching control loops. Attached Figure Description

[0030] Figure 1 This is a power circuit structure diagram for implementing the present invention.

[0031] Figure 2 This is a block diagram of the strategy control for implementing the present invention.

[0032] Figure 3 This is a schematic diagram of the limiting switching circuit in the strategy control block diagram for implementing the present invention.

[0033] Figure 4 This is a schematic diagram of the voltage point settings of the comparator and the first hysteresis comparator in the strategy control block diagram for implementing the present invention.

[0034] Figure 5 This is the voltage logic diagram of the first hysteresis comparator in the strategy control block diagram for implementing the present invention.

[0035] Figure 6 This is a schematic diagram of the logic of the second hysteresis comparator in the strategy control block diagram for implementing the present invention. Detailed Implementation

[0036] This invention proposes a spacecraft power control circuit and method, the power circuit structure of which is as follows: Figure 1 As shown. It includes: a solar cell array SA1, an input capacitor C1, a switching transistor T1, a shunt transistor T2, an inductor L1, an output diode D1, and a battery BAT. The solar cell array SA1 converts solar energy into electrical energy; it is an energy generating device. The generated energy charges the battery BAT through a power circuit.

[0037] Its structure is as follows Figure 2 As shown, it includes: Figure 1 The entire medium-power circuit includes: driver S1, driver S2, OR gate, PWM circuit, MPPT circuit, PI regulator, small-scale circuit, limiting switching circuit, first hysteresis comparator, second hysteresis comparator, comparator, and integrator.

[0038] Figure 2In this context, ISA represents the current of the solar cell array SA1, VSA represents the voltage across the solar cell array SA1, and VBat represents the voltage across the battery BAT. The current ISA of the solar cell array SA1 can be acquired in various ways, including but not limited to current mirror source, Hall sensor, current transformer, etc. The voltages VSA and VBat can be acquired in various ways, including but not limited to direct voltage division sampling with resistors, differential sampling, etc.

[0039] Figure 2 The drive S1 and drive S2 in the middle convert the control signal into a power control signal that can drive the switch T1 and the shunt T2. The drive S1 and drive S2 can be implemented in a variety of ways, including but not limited to bootstrap drive circuit, magnetic isolation drive circuit, optocoupler isolation drive circuit and other drive circuit forms.

[0040] Figure 2 The MPPT circuit in the diagram is used to implement MPPT power point tracking. The inputs to the MPPT circuit are the solar array current ISA and the solar array voltage VSA, and the output is a reference signal Ref. The MPPT circuit determines the output power of the solar array SA1 based on the inputs ISA and VSA, and uses an appropriate method to determine whether the solar array output power is at its maximum. It then outputs the voltage signal Ref to adjust the solar array voltage VSA, thereby achieving the MPPT function. The MPPT circuit can use various methods to determine the solar array output power, including but not limited to the perturbation observation method and the incremental conductance method.

[0041] The MPPT circuit has limitations on the maximum and minimum amplitude of its output voltage signal Ref. When VSA = 0, the output has the minimum amplitude, which is less than 0, and the maximum amplitude is less than the maximum theoretical output voltage of the solar array. As VSA increases from 0, the output voltage signal Ref will slowly increase to 0 at a certain slope before PI modulation is performed.

[0042] The PI regulator is a proportional-integral controller. The reference signal Ref generated by the MPPT circuit is subtracted from the solar cell array voltage SA1 to generate an error signal E1. The input of the PI regulator is the error signal E1, which is then adjusted by proportional-integral control to generate the output voltage signal V1.

[0043] The input of the small circuit is voltage signal V1 and voltage signal V5, and the output voltage signal V2 is the minimum of the two. That is, when voltage signal V1 < voltage signal V5, the output voltage signal V2 = voltage signal V1, and when voltage signal V5 < voltage signal V1, the output voltage signal V2 = voltage signal V5.

[0044] One form of the limiting switching circuit is as follows: Figure 3 As shown. Figure 3The amplitude limiting switching circuit therein includes a first voltage stabilizing diode, a second voltage stabilizing diode and a first switch. The cathode of the first voltage stabilizing diode is connected to the signal line where the voltage signals V2 and V3 are located, and the anode is connected to the ground of the circuit; the cathode of the second voltage stabilizing diode is connected to the first switch, and the anode is connected to the ground of the circuit. One end of the first switch is connected to the cathode of the second voltage stabilizing diode, and the other end is connected to the signal line where the voltage signals V2 and V3 are located. The opening and closing of the first switch are controlled by the voltage signal V6.

[0045] Figure 3 In it, the reverse conduction voltages of the first voltage stabilizing diode and the second voltage stabilizing diode are different, and the reverse conduction voltage of the second voltage stabilizing diode is higher than that of the first voltage stabilizing diode.

[0046] Figure 2 The comparator in it collects the battery voltage VBat. When the VBat voltage is less than Figure 4 the voltage threshold Vref1 of the comparator in it, the voltage V6 generated by the comparator will control Figure 3 the first switch in it to open. At this time, the maximum limiting value on the signal line is the reverse conduction voltage of the first voltage stabilizing diode; when the VBat voltage is greater than Figure 4 Vref1 in it, the voltage signal V6 generated by the comparator will control Figure 3 the first switch in it to close. At this time, the maximum limiting value on the signal line is the reverse conduction voltage of the second voltage stabilizing diode.

[0047] It should be noted that Figure 3 the amplitude limiting switching circuit in it is a hardware implementation method that is easy to describe. The amplitude limiting switching circuit mentioned in the present invention can be implemented in various software or hardware ways, and other forms of amplitude limiting switching methods should also be included in the claims of the present invention

[0048] Figure 2 The voltage logic diagram of the first hysteresis comparator in it is as shown in Figure 5 shown. The gate line voltages Vref2 and Vref3 of the first hysteresis comparator are set as shown in Figure 4 shown. Among them, Vref2 is not necessarily greater than Vref1, and there is no need for a clear size relationship between the two reference values. When the battery voltage rises to VBat > Vref3, the output voltage signal V4 of the first hysteresis comparator is at a low level. When the battery voltage drops to VBat < Vref2, the output voltage signal V4 of the first hysteresis comparator is at a high level.

[0049] Figure 2 The function of the integrator in it is: when the voltage signal V4 is at a high level, the output voltage signal V5 is slowly decreased, and when the voltage signal V4 is at a low level, the output voltage signal V5 is slowly increased.

[0050] Figure 2 The voltage logic diagram of the second hysteresis comparator in Figure 6 is shown as follows. The second hysteresis comparator controls the output voltage signal V7 according to the integrator voltage signal V5, and its control logic is the same as that of the first hysteresis comparator.

[0051] Figure 2 The input of the PWM circuit in is the voltage signal V3, and the outputs are PWM1 and PWM2. The voltage signal V3 is used to control the duty cycle of the output PWM. When the voltage signal V3 increases, the duty cycle of PWM1 rises; when the voltage signal V3 decreases, the duty cycle of PWM1 drops. PWM1 and PWM2 are a pair of complementary PWM (Pulse Width Modulation) signals with dead zones, and the duty cycle ranges of both PWM1 and PWM2 are 0 to 100%.

[0052] Figure 2 The inputs of the OR gate circuit in are PWM1 generated by the PWM circuit and the voltage signal V7 generated by the second hysteresis comparator. When any one of the two input signals is at a high level, the output is at a high level.

[0053] The control method of the present invention is further described below.

[0054] (1) When the satellite is operating in the illumination period, the circuit operates in the MPPT mode. At this time, the battery voltage VBat > Vref1. At this time, the comparator controls the first switch in the amplitude limiting switching circuit to disconnect. At this time, the amplitude limit value of the voltage signal V3 is relatively low. Since the voltage signal V3 is the duty cycle signal of PWM, the duty cycle of PWM cannot reach 100% at this time. When VBat < Vref3, both the voltage signals V4 and V5 are at a high level, while the output of the second hysteresis comparator is at a low level. At this time, the output voltage signal V2 of the minimum selection circuit is V1, and the MPPT loop operates.

[0055] And PWMT1 = PWM1, and the switching tube T1 and the shunt tube T2 operate in a PWM complementary state. <​​(3) When the voltage signal V5 drops to the lowest level, the output voltage signal V7 of the second hysteresis comparator reverses and outputs a high level. At this time, the switching transistor T1 is fully turned on, and the solar array SA1 is directly connected to the ground. The circuit enters the shunt state.

[0058] (4) When the satellite enters the shadow period from the illumination period, the solar array SA1 is always short-circuited at this time.

[0059] (5) When the satellite enters the shadow period, the storage battery discharges continuously, and the voltage VBat decreases continuously. When the storage battery voltage drops to VBat < Vref2, the output of the first hysteresis comparator is at a high level at this time, and the output voltage signal V2 of the minimum-selection circuit is V1. The circuit starts to operate in the MPPT state, and the output of the second hysteresis comparator becomes a low level.

[0060] (6) When the storage battery voltage drops to VBat < Vref1, the first switch of the amplitude-limiting switching circuit closes, and the amplitude limit value of the voltage signal V3 increases. Since the Ref output by the MPPT at this time is the minimum value and less than 0, and VSA is 0, the PI output will be the maximum value. At this time, the duty cycle output by the PWM circuit reaches 100%, the switching transistor T1 is in the on state, and the shunt transistor T2 is in the off state. Since the solar array voltage VSA is 0 at this time, the diode D1 is reversely cut off.

[0061] (7) When the satellite enters the illumination period from the shadow period, the solar array voltage VSA increases. When VSA > VBat, D1 conducts, and the solar array voltage VSA will be clamped to VBat. Since the output voltage signal Ref of the MPPT circuit rises slowly at this time and is still less than 0, the circuit still operates in the direct-through state.

[0062] (8) After the satellite enters the illumination period, when the output voltage signal Ref of the MPPT circuit is greater than VSA, the PI output decreases at this time, and the circuit starts to operate in the MPPT regulation state.

[0063] (9) When VBat > Vref1, the amplitude-limiting switching circuit operates, and the first switch disconnects, making the PWM duty cycle less than 100%. The circuit still operates in the MPPT state at this time.

[0064] (10) Thereafter, the circuit will repeat operating in the working modes of (1) to (9).

[0065] Based on the present invention, protection measures taken to suppress current surges or appropriate modifications are all within the scope of the claims of the present invention.

[0066] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A spacecraft power control circuit, characterized in that, include: The circuit includes a power circuit, drive S1, drive S2, an OR gate, a PWM circuit, an MPPT circuit, a PI regulator, a small-scale circuit, a limiting switching circuit, a first hysteresis comparator, a second hysteresis comparator, a comparator, and an integrator. The MPPT circuit acquires the voltage VSA and current ISA of the solar cell SA1 and generates the MPPT control voltage signal Ref. The control voltage signal Ref output by the MPPT circuit is subtracted from the voltage VSA of the solar cell SA1 to generate an error signal E1. The error signal E1 is processed by the PI regulator to generate a control voltage signal V1, which is then sent to the small-scale circuit. The first hysteresis comparator acquires the voltage signal VBat of the battery BAT and generates an output voltage signal V4, which is sent to the integrator. The integrator integrates the input voltage signal V4 and then transmits the resulting output voltage signal V5 to the small-scale circuit and the second hysteresis comparator. The second hysteresis comparator receives the output voltage signal V5 and generates the output voltage signal V7; the small circuit receives the control voltage signal V1 and the control voltage signal V5 and generates the output voltage signal V2; the comparator acquires the voltage signal VBat of the battery BAT, generates the output voltage signal V6, and transmits it to the limiting switching circuit; the limiting switching circuit receives the voltage signal V2 and the voltage signal V6 and generates the control voltage signal V3; the PWM circuit receives the input of the control voltage signal V3 and generates two PWM signals, namely PWM1 and PWM2; the PWM1 signal and the output voltage signal V7 are input together to the OR gate and generate the drive voltage signal PWMT1; the drive voltage signal PWMT1 is input to the drive S1 to generate the control voltage signal to control the circuit to work; the drive voltage signal PWM2 is input to the drive S2 to generate the control voltage signal, and the control circuit to work.

2. The spacecraft power control circuit according to claim 1, characterized in that, The power circuit includes: a solar cell array SA1, an input capacitor C1, a switching transistor T1, a shunt transistor T2, an inductor L1, an output diode D1, and a battery BAT. The solar cell array SA1 serves as the energy source for the spacecraft's power control circuit, providing input energy. The energy generated by the solar cell array SA1 is filtered by the input capacitor C1 and then reaches the switching transistor T1. Switches T1 and T2 alternately conduct, and inductor L1 stores energy. Together, these three components form a step-down circuit. The node connecting the switching transistor T1 and the input capacitor is the input of the step-down circuit, and the node connecting the inductor L1 and the output diode D1 is the output of the step-down circuit. This circuit converts the high voltage on the input capacitor C1 into a low voltage at the right-side port of inductor L1. The energy output from inductor L1 is transferred to the battery BAT via the output diode D1. The battery BAT serves as an energy storage device, storing the energy generated by the solar cell array SA1 and transformed through the input capacitor C1, switching transistor T1, shunt transistor T2, inductor L1, and output diode D1.

3. The spacecraft power control circuit according to claim 1, characterized in that, The power circuit includes: the MPPT circuit is the hardware logic circuit required to implement the MPPT perturbation algorithm.

4. A spacecraft power control circuit according to claim 1, characterized in that, The drive S1 and drive S2 convert the PWM control signal into a drive signal and control the switching on and off of the switching transistors T1 and T2.

5. A spacecraft power control circuit according to claim 1, characterized in that, The power circuit includes: the error signal E1 is processed by a PI regulator, specifically: the error signal E1 is subjected to proportional-integral operation.

6. A spacecraft power control circuit according to claim 1, characterized in that, The limiting switching circuit includes a first Zener diode, a second Zener diode, and a first switch. When the first switch is open, the first Zener diode operates; when the first switch is closed, the second Zener diode operates.

7. A spacecraft power control circuit according to claim 1, characterized in that, The function of the first hysteresis comparator, the second hysteresis comparator, and the comparator is to reverse the output state when the input voltage exceeds a fixed threshold.

8. A control method for the spacecraft power control circuit of claim 2, characterized in that, include: (1) When the satellite is operating during the sunshine period: When operating in MPPT mode, the battery voltage VBat > comparator voltage threshold Vref1, and the first switch in the comparator control limiting switching circuit is open. When the battery voltage VBat < the first hysteresis comparator voltage threshold Vref3, voltage signals V4 and V5 are both high, while the output of the second hysteresis comparator is low. At this time, the output voltage signal V2 = V1 of the small circuit is taken, and the MPPT loop works; while PWMT1 = PWM1, the switching transistor T1 and the shunt transistor T2 work in the PWM complementary state. As the battery continues to charge, its voltage rises. When the battery voltage VBat > the first hysteresis comparator's voltage threshold Vref3, the first hysteresis comparator outputs a low level, the integrator's output voltage signal V5 begins to decrease, and the output voltage signal of the small circuit switches from V1 to V5, eventually dropping to 0. At this time, the state of the second hysteresis comparator remains unchanged, the PWM circuit's input voltage signal V3 decreases, the PWM1 duty cycle gradually decreases to 0, and the PWM2 duty cycle increases to 100%. Switch T1 is completely turned off, and shunt T2 is turned on. When the voltage signal V5 drops to its lowest point, the output voltage signal V7 of the second hysteresis comparator is reversed and outputs a high level. At this time, the switching transistor T1 is fully turned on, the solar cell array SA1 is directly connected to ground, and the circuit enters the shunt state. (2) When the satellite is operating in shadow: As the satellite enters its shadow period, the battery begins to discharge, and the battery voltage VBat continuously decreases. When the battery voltage drops to VBat < the first hysteresis comparator voltage threshold Vref2, the first hysteresis comparator output is high, and the small circuit output voltage signal V2 = V1 is taken. The circuit starts to work in MPPT state, while the second hysteresis comparator output becomes low. When the battery voltage drops to VBat < comparator voltage threshold Vref1, the first switch of the limiting switching circuit closes, and the voltage signal V3 limit value increases; the PI output is at its maximum value, the duty cycle of the PWM circuit output reaches 100%, the switching transistor T1 is in the conducting state, and the shunt transistor T2 is in the off state; since the solar array voltage VSA is 0 at this time, the diode D1 is reverse cut off. (3) When the satellite transitions from shadow period to light period: When the solar array voltage VSA increases and the solar cell voltage VSA > the battery voltage VBat, D1 conducts. When the solar cell array voltage VSA = the battery voltage VBat, the MPPT circuit output voltage signal Ref rises slowly, and the circuit still operates in the shoot-through state. As the MPPT circuit output Ref increases, the circuit begins to operate in MPPT regulation mode; When the battery voltage VBat > comparator voltage Vref1, the limiting switching circuit works, the voltage signal V3 limiting value decreases, and the circuit completes one working cycle. When a satellite is working in space, it completes one working cycle from (1) to (3) every time it orbits the Earth.

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