A Fault-Tolerant Control System for Spacecraft Power Converter

Abstract

The present invention proposes a fault-tolerant control system for a spacecraft power converter, which is suitable for a high-voltage, high-power, and high-reliability spacecraft power system, and includes: a three-level control unit, a fault mode flying capacitor voltage control unit, a two-level control unit, a fault-tolerant control unit, and a mode switching switch to drive a unit: the present invention designs three-level and two-level working modes according to the topological characteristics of a multi-level flying capacitor; under normal circumstances, the power converter operates in a three-level mode, which can reduce the voltage stress of the power device and the loss of the power supply, and realize high-voltage and high-efficiency operation of the converter; after a short-circuit fault occurs in the power device, the power converter operates in a two-level mode, and can still provide electrical energy to the load, thereby ensuring the reliability of the power converter.

Description

Technical Field

[0001] The invention relates to a fault-tolerant control system of a spacecraft power converter, and in particular to a high-voltage, high-power, high-reliability fault-tolerant control system of a spacecraft power converter. Background Art

[0002] High-power spacecraft power supply system is the future development direction, which can meet the power supply needs of high-power SAR and space scientific research stations. High voltage is a solution to achieve high power. Due to the influence of space radiation, the range of power devices for space power supply is small, and the current highest voltage level is low. In view of the future demand for bus voltage to reach kV level, it is necessary to adopt multi-level topology to reduce the voltage stress of power devices and increase the bus voltage level. In addition, the probability of satellite power failure is high. Statistical results show that the number of failures caused by the power system accounts for 30.3% of the total number of spacecraft failures, accounting for the largest proportion. Once the power supply fails, it will cause catastrophic consequences and paralyze the entire satellite. However, the multi-level power conversion topology uses more power devices. If the fault-tolerant control algorithm is not adopted, its reliability is usually low and cannot meet the reliability requirements of the spacecraft power supply system. Therefore, it is necessary to adopt a fault-tolerant control algorithm to improve the reliability of power converters in high-voltage and high-power occasions. Without adding additional hardware circuits, the fault-tolerant operation of the power converter is achieved by changing the control strategy.

[0003] The fault-tolerance scheme of the power converter is implemented through hardware redundancy, including device redundancy and unit module redundancy. The main problem with the device redundancy scheme is that the added series switch will increase the conduction loss in normal operation mode. The main problems with unit module redundancy are: 1) The number of components in the system increases significantly, the circuit complexity increases, and the circuit safety is affected. 2) Auxiliary components increase system losses, increase heat dissipation pressure, and reduce power density. Since the spacecraft power supply has high power density requirements, lightweight design requires the reuse of components as much as possible to reduce the number of redundant components. Summary of the invention

[0004] The present invention proposes a fault-tolerant control system for a spacecraft power converter, which solves the problem that the power levels of spacecraft such as large space stations and lunar research stations are constantly increasing, the voltage levels are constantly increasing, and the power supply reliability requirements are becoming increasingly higher, and the traditional power converters cannot meet the high voltage and high power requirements of space power systems. The present invention can achieve fault-tolerant operation of the power converter through software strategies without adding hardware circuits, and is suitable for high-voltage, high-power, and high-reliability spacecraft power systems.

[0005] The present invention is achieved through the following technical solutions.

[0006] A fault-tolerant control system for a spacecraft power converter comprises: a three-level control unit, a fault mode flying capacitor voltage control unit, a two-level control unit, a fault-tolerant control unit, a mode switching switch and a driving unit, wherein:

[0007] The three-level control unit is used to control the three-level mode of the converter when the power flying capacitor converter has no fault;

[0008] The fault mode flying capacitor voltage control unit is used to adjust the flying capacitor voltage to a set value when a short circuit is detected in the power tube of the converter, so that the converter switches from the three-level mode to the two-level mode;

[0009] The two-level control unit is used to control the two-level mode of the converter when the power flying capacitor converter device has a short circuit fault;

[0010] The fault-tolerant control unit is used to detect and locate the short-circuit fault of the converter power tube, control the mode switching switch state, and provide a voltage reference value of the flying capacitor voltage control unit during the process of switching from the three-level mode to the two-level mode;

[0011] The mode switching switch is controlled by the fault-tolerant control unit and is used to switch the input of the driving unit between the outputs of the three-level control unit, the fault mode flying capacitor voltage control unit, and the two-level control unit;

[0012] The driving unit is used to amplify the power of the driving signal to realize the control of the three-level flying capacitor converter.

[0013] Beneficial effects of the present invention:

[0014] 1. Spacecraft have high requirements for weight and efficiency. The present invention only uses software control algorithms without adding additional hardware circuits to achieve fault-tolerant operation of the power converter under short-circuit faults. While improving reliability, it does not reduce the power density of the power supply and does not increase heat consumption.

[0015] 2. The present invention designs three-level and two-level working modes according to the topological characteristics of multi-level flying capacitors. Under normal circumstances, the power converter works in the three-level mode, which can reduce the voltage stress of the power device and the loss of the power supply, and realize the high-voltage and high-efficiency operation of the converter.

[0016] 3. After a short circuit occurs in the power device of the present invention, the power converter works in a two-level mode and can still provide power to the load, thereby ensuring the reliability of the power converter;

[0017] 4. The fault-tolerant control unit of the present invention can realize rapid diagnosis of short-circuit faults, and dynamically adjust the reference value of the flying capacitor voltage according to different short-circuit fault types, significantly reduce the voltage and current stress during the switching process, and realize seamless switching of working modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a block diagram of a fault-tolerant control system for a spacecraft power converter of the present invention;

[0019] Figure 2 A circuit diagram of a three-level flying capacitor converter in a specific implementation manner;

[0020] Figure 3 It is a circuit diagram of working modes of a three-level mode control unit at different stages in a specific implementation manner;

[0021] Figure 4 It is a circuit diagram of the working mode of the two-level control unit under different faults in a specific implementation mode;

[0022] Figure 5 : is a diagram for analyzing the short-circuit fault stage of the S3 tube in a specific implementation method, wherein (a) is a waveform diagram of the short-circuit condition of the S3 tube; (b) is a circuit diagram of the working mode of the short-circuit switching process of the S3 tube;

[0023] Figure 6 : is a diagram for analyzing the short-circuit fault stage of the S4 tube in a specific implementation method, wherein (a) is a waveform diagram of the short-circuit condition of the S4 tube; (b) is a circuit diagram of the working mode of the short-circuit switching process of the S4 tube;

[0024] Figure 7 It is a working flow chart of the fault-tolerant control unit in a specific implementation manner. DETAILED DESCRIPTION

[0025] The exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are only exemplary and are intended to illustrate the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0026] like Figure 1 As shown, a fault-tolerant control system of a spacecraft power converter of the present invention specifically includes: a three-level control unit, a fault mode flying capacitor voltage control unit, a two-level control unit, a fault-tolerant control unit, a mode switching switch and a driving unit, wherein:

[0027] The three-level control unit is used to control the three-level mode of the converter when the power flying capacitor converter has no fault;

[0028] like Figure 2 As shown, the three-level mode control unit includes an output voltage control loop and a flying capacitor voltage control loop;

[0029] The output voltage reference value V in the output voltage control loop bus_ref Subtract the output voltage sampling value V H_s The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiter unit. The output result is used as the reference value of the inductor current inner loop. The reference value is subtracted from the inductor current sampling value. The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiter unit. The output result is D o ;

[0030] The flying capacitor reference value V in the flying capacitor voltage control loop fly_ref (V fly_ref =0.5V bus_ref ) minus the flying capacitor voltage sampling value V fly_s The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiter unit. The output result is D fly ;

[0031] The D o Subtract the D fly The difference is input into the pulse width modulation unit PWM1, and the PWM1 generates two complementary drive signals g2 and g3 as the drive of the power tubes S2 and S3 respectively, D o With D fly The sum is input into the pulse width modulation unit PWM2, and PWM2 generates two complementary drive signals g1 and g4 as the drive of power tubes S1 and S4 respectively. Figure 3 shown.

[0032] The fault mode flying capacitor voltage control unit is used to adjust the flying capacitor voltage to a set value when a short circuit is detected in the power tube of the converter, so that the converter switches from the three-level mode to the two-level mode;

[0033] like Figure 5 , 6 As shown, the flying capacitor voltage reference value in the failure mode flying capacitor voltage control unit is controlled by the fault diagnosis signal of the fault-tolerant control unit. When the fault diagnosis signal indicates that the power tubes S2 and S3 are faulty, the flying capacitor voltage reference value V fly_ref2 is 0; when the fault diagnosis signal is that the power tube S1, S4 is faulty, the reference value V of the flying capacitor voltage fly_ref2 The output rated voltage V bus_ref ; Flying capacitor reference value V fly_ref2 Subtract the flying capacitor voltage sampling value V fly_sThe difference is calculated by the proportional integral unit, the calculation result is calculated by the limiting unit, and the calculation result is input into the pulse width modulation unit PWM3. PWM3 generates four driving signals g1~g4 as the driving signals of the power tubes S1~S4 respectively.

[0034] In specific implementation, the pulse width modulation unit PWM3 is controlled by the fault diagnosis signal at the same time. When S1 fails, the values ​​of g1, g3, and g4 are 0, and g2 is in PWM mode; when S2 fails, the values ​​of g2, g3, and g4 are 0, and g1 is in PWM mode; when S3 fails, the values ​​of g1, g2, and g3 are 0, and g4 is in PWM mode; when S4 fails, the values ​​of g1, g2, and g4 are 0, and g3 is in PWM mode. The stage analysis of the specific switching process is as follows: Figure 5 (b) Figure 6 (b).

[0035] The two-level control unit is used to control the two-level mode of the converter when the power flying capacitor converter device has a short circuit fault;

[0036] like Figure 4 As shown, the two-level control unit includes an output voltage control loop and an inductor current control loop; the output voltage reference value V bus_ref Subtract the output voltage sampling value V H_s The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiting unit. The output result is used as the reference value of the inductor current control loop. The reference value is subtracted from the inductor current sampling value, and the difference is calculated by the proportional integral unit. The calculation result is calculated by the limiting unit, and the calculation result is input to PWM4.

[0037] In a specific implementation, the PWM4 is controlled by a fault diagnosis signal. When S1 fails, the value of g4 is 1, the value of g1 is 0, and g2 and g3 complement each other in the PWM mode; when S2 fails, the value of g3 is 1, the value of g2 is 0, and g1 and g4 complement each other in the PWM mode; when S3 fails, the value of g2 is 1, the value of g3 is 0, and g1 and g4 complement each other in the PWM mode; when S4 fails, the value of g1 is 1, the value of g4 is 0, and g2 and g3 complement each other in the PWM mode.

[0038] The fault-tolerant control unit is used to detect and locate the short-circuit fault of the converter power tube, control the mode switching switch state, and provide a voltage reference value of the flying capacitor voltage control unit during the process of switching from the three-level mode to the two-level mode;

[0039] like Figure 7 As shown, the fault-tolerant control unit detects the short-circuit fault state of the power tube, and the specific process is as follows:

[0040] When S1 is short-circuited, the short-circuit protection of S4 is triggered and S4 is turned off, and the short-circuit of S1 is located according to the protection status of S4; similarly, the short-circuit of S2 is located according to the status of S3, the short-circuit of S4 is located according to the status of S1, and the short-circuit of S3 is located according to the status of S2;

[0041] After the short-circuit fault position is located, the fault diagnosis signal is sent to the fault mode flying capacitor voltage control unit and the two-level control unit respectively, and the switching signal is sent to the mode switching switch at the same time; when any power tube fault is detected, the input of the mode switching switch is switched from the three-level control unit to the fault mode flying capacitor voltage control unit;

[0042] When the flying capacitor voltage is controlled to a reference value, the input of the mode switching switch is switched from the failure mode flying capacitor voltage control unit to the two-level control unit.

[0043] Analysis of the S3 tube short circuit stage is as follows Figure 4 As shown, the analysis of the S4 tube short circuit stage is as follows Figure 5 As shown, the S1 fault is analyzed similarly to the S4 fault, and the S2 fault is analyzed similarly to the S3 fault, which will not be repeated here.

[0044] In this embodiment, only the analysis when the low-voltage side input voltage VL is less than half of the high-voltage side voltage VH is given. When the low-voltage side input voltage VL is greater than half of the high-voltage side voltage VH, a similar analysis can be performed.

[0045] The mode switching switch is controlled by the fault-tolerant control unit, the input end is respectively connected to the outputs of the three-level control unit, the fault mode flying capacitor voltage control unit, and the two-level control unit, and the output end is connected to the input of the driving unit, so as to switch the input of the driving unit between the outputs of the three-level control unit, the fault mode flying capacitor voltage control unit, and the two-level control unit;

[0046] The driving unit is used to amplify the power of the driving signal, so as to realize the control of the three-level flying capacitor converter by the fault-tolerant control system.

[0047] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A fault-tolerant control system for a spacecraft power converter, characterized in that: include: A three-level control unit, a fault mode flying capacitor voltage control unit, a two-level control unit, a fault-tolerant control unit, a mode switching switch and a driving unit, wherein: The three-level control unit is used to control the three-level mode of the converter when the power flying capacitor converter has no fault; The fault mode flying capacitor voltage control unit is used to adjust the flying capacitor voltage to a set value when a short circuit is detected in the power tube of the converter, so that the converter switches from the three-level mode to the two-level mode; The two-level control unit is used to control the two-level mode of the converter when the power flying capacitor converter device has a short circuit fault; The fault-tolerant control unit is used to detect and locate the short-circuit fault of the converter power tube, control the mode switching switch state, and provide a voltage reference value of the flying capacitor voltage control unit during the process of switching from the three-level mode to the two-level mode; The mode switching switch is controlled by the fault-tolerant control unit and is used to switch the input of the driving unit between the outputs of the three-level control unit, the fault mode flying capacitor voltage control unit, and the two-level control unit; The driving unit is used to amplify the power of the driving signal to realize the control of the three-level flying capacitor converter; The three-level control unit includes an output voltage control loop and a flying capacitor voltage control loop; The output voltage reference value V in the output voltage control loop bus_ref Subtract the output voltage sampling value V H_s The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiter unit. The output result is used as the reference value of the inductor current inner loop. The reference value is subtracted from the inductor current sampling value. The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiter unit. The output result is D o ; The flying capacitor reference value V in the flying capacitor voltage control loop fly_ref Subtract the flying capacitor voltage sampling value V fly_s The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiter unit. The output result is D fly ; The D o Subtract the D fly The difference is input into the pulse width modulation unit PWM1, and the PWM1 generates two complementary drive signals g2 and g3 as the drive of the power tubes S2 and S3 respectively, D o With D fly The sum is input into the pulse width modulation unit PWM2, and PWM2 generates two complementary drive signals g1 and g4 as the drive of power tubes S1 and S4 respectively; The flying capacitor voltage reference value in the failure mode flying capacitor voltage control unit is controlled by the fault diagnosis signal of the fault-tolerant control unit. When the fault diagnosis signal indicates that the power tubes S2 and S3 are faulty, the flying capacitor voltage reference value V fly_ref2 is 0; when the fault diagnosis signal is that the power tube S1, S4 is faulty, the reference value V of the flying capacitor voltage fly_ref2 The output rated voltage V bus_ref ; Flying capacitor reference value V fly_ref2 Subtract the flying capacitor voltage sampling value V fly_s The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiter unit. The calculation result is input into the pulse width modulation unit PWM3, and PWM3 generates four driving signals g1~g4 as the driving signals of the power tubes S1~S4 respectively; The specific process of the fault-tolerant control unit detecting the short-circuit fault state of the power tube is as follows: When S1 is short-circuited, the short-circuit protection of S4 is triggered and S4 is turned off, and the short-circuit of S1 is located according to the protection status of S4; similarly, the short-circuit of S2 is located according to the status of S3, the short-circuit of S4 is located according to the status of S1, and the short-circuit of S3 is located according to the status of S2; After the short-circuit fault position is located, the fault diagnosis signal is sent to the fault mode flying capacitor voltage control unit and the two-level control unit respectively, and the switching signal is sent to the mode switching switch at the same time; when any power tube fault is detected, the input of the mode switching switch is switched from the three-level control unit to the fault mode flying capacitor voltage control unit; When the flying capacitor voltage is controlled to a reference value, the input of the mode switching switch is switched from the failure mode flying capacitor voltage control unit to the two-level control unit.

2. A spacecraft power converter fault-tolerant control system as claimed in claim 1, characterized in that: The pulse width modulation unit PWM3 is also controlled by the fault diagnosis signal. When S1 fails, the values ​​of g1, g3, and g4 are 0, and g2 is in PWM mode; when S2 fails, the values ​​of g2, g3, and g4 are 0, and g1 is in PWM mode; when S3 fails, the values ​​of g1, g2, and g3 are 0, and g4 is in PWM mode; when S4 fails, the values ​​of g1, g2, and g4 are 0, and g3 is in PWM mode.

3. A spacecraft power converter fault-tolerant control system as claimed in claim 1 or 2, characterized in that: The two-level control unit includes an output voltage control loop and an inductor current control loop; the output voltage reference value V bus_ref Subtract the output voltage sampling value V H_s The difference is calculated by the proportional integral unit, and the calculation result is calculated by the limiting unit. The output result is used as the reference value of the inductor current control loop. The reference value is subtracted from the inductor current sampling value, and the difference is calculated by the proportional integral unit. The calculation result is calculated by the limiting unit, and the calculation result is input to PWM4.

4. A spacecraft power converter fault-tolerant control system as claimed in claim 3, characterized in that: The PWM4 is controlled by the fault diagnosis signal. When S1 fails, the value of g4 is 1, the value of g1 is 0, and g2 and g3 complement each other in the PWM mode; when S2 fails, the value of g3 is 1, the value of g2 is 0, and g1 and g4 complement each other in the PWM mode; when S3 fails, the value of g2 is 1, the value of g3 is 0, and g1 and g4 complement each other in the PWM mode; when S4 fails, the value of g1 is 1, the value of g4 is 0, and g2 and g3 complement each other in the PWM mode.

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