An overvoltage protection device for an aviation power generation system

Abstract

This invention belongs to the technical field of aviation power generation systems and relates to an overvoltage protection device for an aviation power generation system. The device includes: a power supply monitoring circuit that monitors the DC power output from the power supply conversion circuit and outputs a power supply monitoring signal to a logic synthesis circuit; a discrete signal sampling circuit that takes as input a 28V / open discrete signal output from the generator controller and outputs a high / low level signal after signal sampling; an overvoltage delay protection circuit that outputs an overvoltage delay protection signal; an overvoltage limiting circuit that outputs an overvoltage limiting signal; and a logic synthesis circuit that takes as input the overvoltage delay protection signal, the overvoltage limiting signal, the power supply monitoring signal, and the operation test result signal, and outputs an excitation relay control signal and a main contactor coil control signal after logical AND gate operation; an excitation control circuit that controls the connection and disconnection of the excitation winding signal and the generator controller based on the excitation relay control signal; and a main contactor control circuit that controls whether the power generation system is connected to the grid based on the main contactor coil control signal.

Description

Technical Field

[0001] This invention belongs to the technical field of aviation power generation systems and relates to an overvoltage protection device for aviation power generation systems. Background Technology

[0002] The current architecture of aviation power generation systems mainly includes aviation generators, generator controllers, current sensors, and other devices. As the main protection device within the aviation power generation system, the generator controller can only perform overvoltage regulation or overvoltage protection and then disconnect the power generation system from the grid when overvoltage occurs under certain operating conditions.

[0003] When the generator controller malfunctions in voltage regulation, or when the generator system output is short-circuited and the GCU is over-excited, the generator controller will be unable to regulate the generator system output voltage to meet national military standards or protocol requirements within the specified time. In this case, the generator controller software will output a de-excitation signal and a main contactor drive control signal. If the generator controller software malfunctions or crashes, the excitation and main contactor will fail to disconnect, preventing the generator system from being properly disconnected from the grid. This can lead to a catastrophic failure of the generator system's overvoltage protection, severely damaging the onboard load. Summary of the Invention

[0004] The purpose of this invention is to provide an overvoltage protection device for an aviation power generation system, which works in conjunction with the generator controller to participate in the operation of the power generation system. This device adopts a purely hardware design, forming an independent and dissimilar design with the generator controller's software overvoltage protection design. It can serve as a backup protection for the output overvoltage of the aviation power generation system after the generator controller's overvoltage regulation and software protection functions are lost, ensuring the power safety of the power grid and onboard loads, and improving the safety and robustness of the aviation power generation system.

[0005] The technical solution of this invention is as follows:

[0006] An overvoltage protection device for an aviation power generation system includes: a power supply conversion circuit, a power supply monitoring circuit, a discrete signal sampling circuit, an overvoltage limiting circuit, an overvoltage delay protection circuit, a logic synthesis circuit, an excitation control circuit, and a main contactor control circuit.

[0007] The power conversion circuit takes three-phase AC power output from the aircraft generator as input and converts the three-phase AC power into 28V DC power and other DC power required for the operation of the circuit before outputting it.

[0008] The power supply monitoring circuit receives DC power from the power conversion circuit. The power supply monitoring circuit monitors the DC power output from the power conversion circuit to determine if the power conversion circuit is faulty, and outputs a power supply monitoring signal to the logic synthesis circuit.

[0009] The discrete signal sampling circuit takes a 28V / open discrete signal from the generator controller as input and outputs a high / low level signal after sampling.

[0010] The overvoltage delay protection circuit takes the voltage signal at the voltage regulation point of the power generation system as input, and outputs an overvoltage delay protection signal after peak sampling, tracking, integral delay, and reference comparison; the overvoltage delay protection signal is a high / low level signal;

[0011] The overvoltage limiting circuit takes the voltage signal from the voltage regulation point of the power generation system as input, and outputs an overvoltage limiting signal after rectification, voltage division filtering and voltage comparison; the overvoltage limiting signal is a high / low level signal.

[0012] The logic synthesis circuit takes overvoltage delay protection signal, overvoltage limit signal, power supply monitoring signal and operation test result signal as inputs, and outputs excitation relay control signal and main contactor coil control signal after being processed by a logic AND gate.

[0013] The excitation control circuit receives an excitation relay control signal as input. The excitation control circuit controls the on / off state of the relay based on the excitation relay control signal, thereby controlling the on / off state of the excitation winding signal and the generator controller.

[0014] The main contactor control circuit receives the main contactor coil control signal and controls the on / off state of the main contactor based on the main contactor coil control signal, thereby controlling whether the power generation system is connected to the grid.

[0015] Furthermore, the system also includes: a test circuit;

[0016] The discrete signal sampling circuit receives three 28V / open discrete signals. After passing through the discrete signal sampling circuit, which consists of resistors, capacitors, Zener diodes, diodes, and a non-inverting buffer, it outputs three high and low level signals. Two of these high and low level signals are transmitted to the operation test circuit, and the other high and low level signal is transmitted to the logic synthesis circuit.

[0017] Furthermore, the operation test circuit outputs two high / open discrete signals after the two input high and low level signals are filtered by capacitors and regulated by Zener diodes. These signals are used as test signals for the overvoltage delay protection circuit and the overvoltage limiting circuit, respectively.

[0018] Furthermore, the overvoltage delay protection circuit compares the input signal with the reference voltage after peak sampling, following, and integral delay, and outputs an overvoltage delay protection signal to the logic synthesis circuit. The overvoltage delay protection signal is a high / low level signal. When the input signal exceeds the reference voltage and reaches the inverse delay time, the overvoltage delay protection signal is low level.

[0019] Furthermore, the overvoltage limiting circuit compares the input signal with the overvoltage limiting threshold value and outputs an overvoltage limiting signal to the logic synthesis circuit. The overvoltage limiting signal is a high-low level signal. When the input signal voltage exceeds the overvoltage limiting threshold value, the overvoltage limiting signal becomes low level.

[0020] Furthermore, the input terminal of the excitation control circuit is an excitation relay control signal. The excitation relay control signal is connected to the gate of the field-effect transistor after passing through a resistor voltage divider and a Zener diode, so as to control the on and off of the field-effect transistor.

[0021] The negative terminal of the excitation relay coil is connected to the drain of the field-effect transistor, and the source of the field-effect transistor is grounded.

[0022] When the excitation relay control signal is high, the field-effect transistor is turned on, the negative terminal of the relay coil is grounded, the relay is turned on, and the generator excitation negative signal is output to the generator controller.

[0023] When the excitation relay control signal is low, the MOSFET is not conducting, the relay is disconnected, the generator excitation negative signal cannot be output to the generator controller, and the excitation winding of the exciter is open-circuited.

[0024] Furthermore, the input terminal of the main contactor control circuit is the main contactor coil control signal, which is connected to the P-channel MOSFET after passing through a resistor, a Zener diode, and a transistor.

[0025] When the main contactor coil control signal is high, the P-channel MOSFET is turned on, and the main contactor control signal sent by the generator controller is output to the main contactor coil, turning on the main contactor.

[0026] When the main contactor coil control signal is low, the P-channel MOSFET is not turned on, and the main contactor control signal sent by the generator controller cannot be output to the main contactor coil. The main contactor is disconnected, thus realizing the power generation system's grid disconnection protection.

[0027] Furthermore, the system also includes: a fault monitoring circuit for the main contactor and the excitation control circuit;

[0028] The input signals of the fault monitoring circuit for the main contactor and excitation control circuit include: a set of auxiliary contact status signals of the excitation relay in the excitation control circuit, the excitation relay control signal generated by the logic synthesis circuit, the main contactor control signal sent by the generator controller in the main contactor control circuit, and the main contactor coil control signal generated by the logic synthesis circuit.

[0029] The excitation relay auxiliary contact status signal and the excitation relay control signal are sequentially passed through an XOR gate and a NOT gate to generate an excitation control circuit fault detection signal.

[0030] The main contactor control signal and the main contactor coil control signal are passed through an XOR gate to generate a fault detection signal for the main contactor control circuit.

[0031] The fault detection signal of the excitation control circuit and the fault detection signal of the main contactor control circuit are then passed through an AND gate to generate the fault monitoring result signal of the main contactor and the excitation control circuit.

[0032] The fault monitoring result signal of the main contactor and excitation control circuit is a high-low level signal. A low level indicates that the main contactor and excitation control circuit have a fault.

[0033] Furthermore, the input signal of the overvoltage delay protection circuit also includes: a high / low level signal output by the discrete signal sampling circuit;

[0034] When the protection device is in operation test state, the input signal is selected as a high / low level signal; when the protection device is in normal power generation state, the input is the voltage signal of the power generation system voltage regulation point.

[0035] The input signal of the overvoltage limiting circuit also includes: a high / low level signal output by the discrete signal sampling circuit;

[0036] When the protection device is in operation test state, the input signal is selected as a high / low level signal; when the protection device is in normal power generation state, the input is the voltage signal of the power generation system voltage regulation point.

[0037] Furthermore, when the system is powered on, the protection device operates in the running test state. The power supply monitoring circuit detects the power supply conversion circuit and outputs the detection result to the logic synthesis circuit. The generator controller sends two 28V / open discrete signals, which are tested by the delay protection circuit and the overvoltage limiting circuit after passing through the discrete signal sampling circuit and the running test circuit, respectively, and then sent to the logic synthesis circuit. The generator controller then sends a third 28V / open discrete signal, which is sent to the logic synthesis circuit after passing through the discrete signal sampling circuit. The logic synthesis circuit performs AND gate processing on the above four signals to generate the excitation relay control signal and the main contactor coil control signal. When all four signals are high level, the output excitation relay control signal and the main contactor coil control signal are high level, the main contactor and the excitation relay are closed, and the aviation power generation system completes voltage establishment and grid connection.

[0038] After the voltage is built up and connected to the grid, the protection device operates in the test state. The input signals of the overvoltage limiting circuit and the overvoltage delay protection circuit are switched to the voltage signal of the voltage regulation point of the power generation system. The logic synthesis circuit still performs AND gate processing on the above four signals to generate the excitation relay control signal and the main contactor coil control signal. When all four signals are at a high level, the aviation power generation system operates normally.

[0039] When any of the above four signals goes low, the excitation relay control signal and the main contactor coil control signal go low, the main contactor and the excitation relay disconnect, the aviation power generation system is disconnected from the grid, and overvoltage protection is achieved.

[0040] The beneficial effects of this invention are:

[0041] This invention provides an overvoltage protection device for an aviation power generation system. As a backup protection device when the built-in software overvoltage protection of the generator controller fails, it can prevent catastrophic overvoltage events and improve the safety of the existing aviation power generation system. Simultaneously, it can modify the configuration architecture of the existing aviation power generation system, adding new economic growth points. Attached Figure Description

[0042] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings will be described below.

[0043] Figure 1 This is a diagram showing the interconnections of an aviation power generation system.

[0044] Figure 2 This is a functional architecture diagram of an overvoltage protection device.

[0045] Figure 3 This is a schematic diagram of an overvoltage delay protection circuit.

[0046] Figure 4 This is a block diagram of the excitation control function architecture. To achieve backup protection for generator excitation control, an overvoltage protection device's excitation control circuit is integrated into the original generator controller's excitation control circuit in the aviation power generation system. The series operation of these two excitation control circuits achieves excitation control protection. During normal generator operation, the relays in the excitation circuit are all closed, not affecting normal generator operation. When an overvoltage occurs and the inverse delay time is reached, or when a power supply failure occurs, the overvoltage protection device executes its overvoltage protection function, quickly cutting off the excitation. By reducing the excitation current, it regulates and limits the generator's output voltage, thus achieving backup protection for generator excitation control.

[0047] Figure 5 This is the schematic diagram of the excitation control circuit.

[0048] Figure 6 This is a block diagram of the main contactor control function. To achieve backup protection for the main contactor, an overvoltage protection device's main contactor control circuit is connected in series with the existing generator controller's main contactor control circuit in the aviation power generation system. When an overvoltage occurs in the generator and the inverse delay time is reached, or when a power supply failure occurs, the overvoltage protection device performs the overvoltage protection function to ensure reliable operation of the generator contactor. This realizes the protection and disconnection function of the main contactor in the aviation power generation system, protecting downstream electrical equipment.

[0049] Figure 7 Schematic diagram of the main contactor control circuit;

[0050] Figure 8 This is a schematic diagram of the fault monitoring circuit for the main contactor and excitation control loop. Detailed Implementation

[0051] This section describes embodiments of the present invention, used to explain and illustrate the technical solutions of the present invention.

[0052] This invention primarily employs a pure hardware design. The main function of the hardware is to act as a backup overvoltage protection device when the generator controller software overvoltage protection (i.e., the main protection) fails within the aviation power generation system. This device also serves as the final level of protection for the power generation system, disconnecting the overvoltage-affected power generation system, thus improving the system's safety and preventing damage to related load equipment.

[0053] An overvoltage protection device for an aviation power generation system, the device serving as a hardware backup for the overvoltage protection of the generator controller software, the device comprising:

[0054] Power supply conversion circuit: The input is the three-phase output of the permanent magnet generator of the aircraft generator. After passing through the three-phase bridge uncontrolled rectifier circuit and DC / DC converter, the output is the internal 28V and other types of DC power required for the operation of the hardware circuit.

[0055] Power supply monitoring circuit: The input is the DC power output from the power supply conversion circuit. After processing by voltage divider, filter, sampling, and comparison circuits, the output power supply monitoring result signal is sent as the fourth control input signal to the logic synthesis circuit and simultaneously to the status information conversion circuit. The power supply monitoring result signal is a high / low level signal; a low level indicates a power supply fault.

[0056] Discrete signal sampling circuit: The input consists of three 28V / open discrete signals sent by the generator controller to the overvoltage protection device. After passing through the discrete signal sampling circuit composed of resistors, capacitors, Zener diodes, diodes, and non-inverting buffers, the output is a high / low level signal. The first two signals are sent to the operation test circuit, and the third signal is sent to the logic synthesis circuit as the operation test result signal (high level indicates that the operation test has passed) as the first control input signal of the logic synthesis circuit.

[0057] The test circuit operates as follows: The input consists of the first two high / low level signals from the discrete signal sampling circuit. After capacitor filtering and Zener diode voltage regulation, two high / open discrete signals are output, which serve as the overvoltage delay protection test excitation signal (high level indicates that the test excitation signal is valid, and open circuit indicates that no test is performed) and the overvoltage limit test excitation signal (high level indicates that the test excitation signal is valid, and open circuit indicates that no test is performed), respectively. These signals are then fed into the overvoltage delay protection circuit and the overvoltage limit circuit.

[0058] Overvoltage delay protection circuit: When the device is in the operation test state, the input of this circuit is the overvoltage delay protection test excitation signal output by the operation test circuit. This excitation signal is then processed by... Figure 3 The peak sampling circuit 1, follower circuit 2, integral delay circuit 3, and control protection signal output circuit 4 shown in the diagram output an overvoltage delay protection signal, which is sent to the logic synthesis circuit as the second control input signal. The overvoltage delay protection signal is a high / low level signal; a low level indicates that an overvoltage has occurred and the inverse delay time has been reached.

[0059] When the device completes its operational testing and enters the power generation state, the circuit input is the voltage signal at the power generation system's voltage regulation point (at this time, the overvoltage delay protection test excitation signal is open). The overvoltage delay protection circuit consists of... Figure 3 The circuit shown comprises a peak sampling circuit 1, a follower circuit 2, an integral delay circuit 3, and a control protection signal output circuit 4. The peak sampling circuit 1 mainly consists of a peak-sensitive circuit composed of resistors, diodes, and capacitors, and a resistor voltage divider and capacitor filter circuit. It is mainly used to sample and sense the voltage regulation voltage of the power generation system. The follower circuit 2 mainly consists of a circuit with an operational amplifier as the core and resistors and capacitors as peripheral components. It can improve the output load capacity and anti-interference capability. The integral delay circuit 3 consists of an operational amplifier, resistors, and capacitors. By matching the resistor and capacitor parameters, it adjusts the inverse delay time of the hardware overvoltage protection. The control protection signal output circuit 4 consists of an operational amplifier, resistors, capacitors, and a reference voltage. It compares the output of the integral circuit with the reference voltage. When the voltage regulation point signal of the power generation system exceeds the overvoltage threshold and reaches the inverse delay time, it outputs an overvoltage delay protection signal, which is sent to the logic synthesis circuit as the second control input signal.

[0060] Overvoltage limiting circuit: When the device is in operation test mode, the input of this circuit is the overvoltage limiting test excitation signal output by the operation test circuit. This excitation signal is compared with the overvoltage limiting threshold value by a voltage comparator, and then outputs an overvoltage limiting signal, which is sent to the logic synthesis circuit as the third control input signal. The overvoltage limiting signal is a high / low level signal; a low level indicates that the voltage has reached the overvoltage limit point and the overvoltage limiting function has been activated.

[0061] When the device completes its operational testing and enters the power generation state, the circuit input is the voltage signal at the voltage regulation point of the power generation system (at this time, the overvoltage limit test excitation signal is open-circuited). After passing through a three-phase half-wave uncontrolled rectification, RC voltage divider filtering, and a voltage comparator, it is compared with the overvoltage limit threshold value, and an overvoltage limit signal is output. This overvoltage limit signal is sent to the logic synthesis circuit as the third control input signal. The overvoltage limit signal is a high / low level signal; a low level indicates that the voltage has reached the overvoltage limit point and the overvoltage limit function has been activated. When the overvoltage limit function is activated, it can quickly cut off the excitation, thereby reducing the excitation current to regulate and limit the generator output voltage, thus reducing the generator output voltage and controlling the adverse effects caused by excessively high three-phase voltage at the voltage regulation point.

[0062] The logic synthesis circuit takes into account the following inputs: the operation test result signal, the overvoltage delay protection signal, the overvoltage limit signal, and the power supply monitoring result signal. These four signals are processed by AND gate logic, and the outputs are the excitation relay control signal and the main contactor coil control signal. These two control signals are two control signals with the same level generated by the logic synthesis circuit, which realize the overvoltage protection function of the main contactor and the excitation relay closing when power-on is completed, there is no power supply fault, the operation test is passed, and there is no overvoltage fault, and the power generation system is in operation.

[0063] Excitation control circuit: Implements backup protection for excitation control; see functional architecture block diagram. Figure 4 For details on the excitation control circuit, please refer to [link / reference]. Figure 5 This circuit mainly consists of resistors, Zener diodes, MOSFETs, relays, and diodes. The input is the excitation negative signal from the generator's excitation relay, generated by the logic synthesis circuit. This control signal, after being processed by a resistor divider and Zener diode, controls the on / off state of the MOSFET. The negative terminal of the relay coil is connected to the drain of the MOSFET. When the control signal is high, the MOSFET conducts and grounds, and the negative terminal of the relay coil is grounded, causing the relay to conduct and output the generator excitation negative signal to the generator controller. When the control signal is low, the MOSFET does not conduct, the relay is off, the generator excitation negative signal cannot be output to the generator controller, and the exciter winding is in an open-circuit state. Simultaneously, a set of auxiliary contacts of the relay in this circuit is sent to the contactor and excitation control circuit fault monitoring circuit for monitoring the circuit.

[0064] Main contactor control circuit: Implements backup protection for the main contactor control; see functional architecture block diagram. Figure 6 For details on the main contactor control circuit, please refer to [link / reference]. Figure 7This circuit mainly consists of resistors, capacitors, Zener diodes, transistors, P-channel MOSFETs, diodes, and transient voltage suppression diodes. The input is the main contactor control signal sent by the generator controller. When the main contactor coil control signal generated by the logic synthesis circuit is high, the P-channel MOSFET conducts, sending the main contactor control signal from the generator controller to the main contactor coil, thus turning on the main contactor. When the control signal is low, the P-channel MOSFET does not conduct, the main contactor control signal from the generator controller cannot be output, the main contactor coil control signal is open, and the main contactor disconnects, achieving grid disconnection protection for the power generation system. Simultaneously, the main contactor control signal sent by the generator controller in this circuit is connected to the contactor and excitation control circuit fault monitoring circuit for monitoring this circuit.

[0065] Fault monitoring circuit for main contactor and excitation control circuit: see circuit details. Figure 8 The inputs are the relay auxiliary contact status signal in the excitation control circuit, the excitation relay control signal generated by the logic synthesis circuit, the main contactor control signal sent by the generator controller in the main contactor control circuit, and the main contactor coil control signal generated by the logic synthesis circuit. This circuit, on the one hand, samples the relay auxiliary contact status and performs XOR-NOT-NOT gate processing with the excitation relay control signal generated by the logic synthesis circuit to achieve excitation control circuit fault monitoring. On the other hand, the circuit samples the main contactor control signal and performs XOR-NOT gate processing with the main contactor coil control signal generated by the logic synthesis circuit to achieve main contactor control circuit fault monitoring. Finally, the excitation control circuit fault monitoring result signal and the main contactor control circuit fault monitoring result signal are ANDed to achieve the main contactor and excitation control circuit fault monitoring functions. The output is a main contactor and excitation control circuit fault monitoring result signal, which is a high / low level signal. A low level indicates a fault in the main contactor and excitation control circuit, and this signal is sent to the status information conversion circuit.

[0066] Status information conversion circuit: The inputs are the power supply monitoring result signal, overvoltage delay protection signal, and main contactor and excitation control circuit fault monitoring result signal generated by the overvoltage protection device. These signals are high / low level signals. After passing through the isolation circuit with the optical MOS relay as the core and resistors, capacitors and diodes as peripheral devices, the reliability and anti-interference of signal transmission are improved. The output is the status signal of power supply monitoring result, overvoltage delay protection, and main contactor and excitation control circuit fault monitoring result sent to the generator controller. These three signals are 28V / open circuit. 28V indicates a fault, and open circuit indicates no fault.

[0067] When the aviation power generation system is in an off-power condition, the fault monitoring circuit of the main contactor and excitation control circuit in the overvoltage protection device outputs a high level, the power supply monitoring circuit outputs a high level, and the overvoltage delay protection circuit outputs a high level. The three signals output by the status information conversion circuit are all in an open circuit state. The logic synthesis circuit outputs two low levels. The relay in the excitation control circuit is in an open state. The generator excitation negative signal cannot be output to the generator controller. The exciter excitation winding is in an open circuit state. The entire system is in an un-energized and un-voltaged state. The main contactor control signal in the main contactor control circuit is in an open circuit state. The main contactor is in an open state. The entire aviation power generation system is not connected to the grid. There is no voltage on the busbar. The load equipment has no power supply.

[0068] When the permanent magnet generator in the power generation system starts to rotate and reaches a certain speed, the power conversion circuit in the overvoltage protection device starts to work, converting the output voltage of the permanent magnet generator into internal 28V and other types of DC power required for the operation of the hardware circuit. When the permanent magnet generator and the power conversion circuit are fault-free, the power supply monitoring circuit outputs a high level, which is sent to the logic synthesis circuit on one hand, and to the generator controller on the other hand via the status information conversion circuit. After power-on, the generator controller sends two 28V / open discrete signals to the overvoltage protection device. The overvoltage protection device then begins sampling and testing these discrete signals, specifically testing the overvoltage delay protection circuit and the overvoltage limiting circuit. The test results are sent to the logic synthesis circuit. The generator controller then sends a third 28V / open discrete signal—the operation test result signal—which, after discrete signal sampling, is sent to the logic synthesis circuit. The logic synthesis circuit performs AND gate logic processing on the four signals. When all four signals are high, the logic synthesis circuit outputs both the excitation relay control signal and the main contactor coil control signal as high. This ensures that the main contactor and excitation relay close when the overvoltage protection device is powered on, there is no power supply fault, the operation test is passed, and there is no overvoltage fault. This allows the generator system to work with the aircraft power generation system to build up voltage and connect to the grid, and the busbar begins supplying power to the load equipment. When any signal is low, the main contactor and excitation relay open, providing overvoltage protection during generator system operation and ensuring the safety of the power supply to the equipment. During the operation of the power generation system, the power supply monitoring result signal, overvoltage delay protection signal, and fault monitoring result signal of the main contactor and excitation control circuit generated in the overvoltage protection device are sent to the generator controller through the status information conversion circuit.

Claims

1. An overvoltage protection device for an aviation power generation system, characterized in that: The device includes: a power supply conversion circuit, a power supply monitoring circuit, a discrete signal sampling circuit, an overvoltage limiting circuit, an overvoltage delay protection circuit, a logic synthesis circuit, an excitation control circuit, a main contactor control circuit, and an operation test circuit. The power conversion circuit takes three-phase AC power output from the aircraft generator as input, and converts the three-phase AC power into 28V DC power and DC power required for the operation of other circuits before outputting it. The power supply monitoring circuit receives DC power from the power conversion circuit. The power supply monitoring circuit monitors the DC power output from the power conversion circuit to determine if the power conversion circuit is faulty, and outputs a power supply monitoring signal to the logic synthesis circuit. The discrete signal sampling circuit takes a 28V / open discrete signal from the generator controller as input and outputs a high / low level signal after sampling. The overvoltage delay protection circuit takes the voltage signal at the voltage regulation point of the power generation system as input, and outputs an overvoltage delay protection signal after peak sampling, tracking, integral delay, and reference comparison; the overvoltage delay protection signal is a high / low level signal; The overvoltage limiting circuit takes the voltage signal from the voltage regulation point of the power generation system as input, and outputs an overvoltage limiting signal after rectification, voltage division filtering and voltage comparison; the overvoltage limiting signal is a high / low level signal. The logic synthesis circuit takes overvoltage delay protection signal, overvoltage limit signal, power supply monitoring signal and operation test result signal as inputs, and outputs excitation relay control signal and main contactor coil control signal after being processed by a logic AND gate. The excitation control circuit receives an excitation relay control signal as input. The excitation control circuit controls the on / off state of the relay based on the excitation relay control signal, thereby controlling the on / off state of the excitation winding signal and the generator controller. The main contactor control circuit receives the main contactor coil control signal and controls the on / off state of the main contactor according to the main contactor coil control signal, thereby controlling whether the power generation system is connected to the grid. The discrete signal sampling circuit receives three 28V / open discrete signals. After passing through the discrete signal sampling circuit, which consists of resistors, capacitors, Zener diodes, diodes, and a non-inverting buffer, it outputs three high and low level signals. Two of these high and low level signals are transmitted to the operation test circuit, and the other high and low level signal is transmitted to the logic synthesis circuit. When the system is powered on, the protection device operates in the test state. The power supply monitoring circuit detects the power supply conversion circuit and outputs the detection result to the logic synthesis circuit. The generator controller sends two 28V / open discrete signals, which are tested by the delay protection circuit and the overvoltage limiting circuit after passing through the discrete signal sampling circuit and the test circuit, respectively, and then sent to the logic synthesis circuit. The generator controller then sends a third 28V / open discrete signal, which is sent to the logic synthesis circuit after passing through the discrete signal sampling circuit. The logic synthesis circuit performs AND gate processing on the above four signals to generate the excitation relay control signal and the main contactor coil control signal. When all four signals are high level, the output excitation relay control signal and the main contactor coil control signal are high level, the main contactor and the excitation relay are closed, and the aviation power generation system completes voltage establishment and grid connection. After the voltage is built up and connected to the grid, the protection device operates in the test state. The input signals of the overvoltage limiting circuit and the overvoltage delay protection circuit are switched to the voltage signal of the voltage regulation point of the power generation system. The logic synthesis circuit still performs AND gate processing on the above four signals to generate the excitation relay control signal and the main contactor coil control signal. When all four signals are at a high level, the aviation power generation system operates normally. When any of the above four signals goes low, the excitation relay control signal and the main contactor coil control signal go low, the main contactor and the excitation relay disconnect, the aviation power generation system is disconnected from the grid, and overvoltage protection is achieved.

2. The apparatus according to claim 1, characterized in that: The test circuit outputs two discrete high / open signals after the two input high and low level signals are filtered by capacitors and regulated by Zener diodes. These signals are used as test signals for the overvoltage delay protection circuit and the overvoltage limiting circuit, respectively.

3. The apparatus according to claim 2, characterized in that: The overvoltage delay protection circuit compares the input signal with the reference voltage after peak sampling, following, and integral delay, and outputs an overvoltage delay protection signal to the logic synthesis circuit. The overvoltage delay protection signal is a high / low level signal. When the input signal exceeds the reference voltage and reaches the inverse delay time, the overvoltage delay protection signal is low level.

4. The apparatus according to claim 3, characterized in that: The overvoltage limiting circuit compares the input signal with the overvoltage limiting threshold and outputs an overvoltage limiting signal to the logic synthesis circuit. The overvoltage limiting signal is a high-low level signal. When the input signal voltage exceeds the overvoltage limiting threshold, the overvoltage limiting signal is low level.

5. The apparatus according to claim 4, characterized in that: The input terminal of the excitation control circuit is the excitation relay control signal. The excitation relay control signal is connected to the gate of the field-effect transistor after passing through a resistor voltage divider and a Zener diode, so as to control the on and off of the field-effect transistor. The negative terminal of the excitation relay coil is connected to the drain of the field-effect transistor, and the source of the field-effect transistor is grounded. When the excitation relay control signal is high, the field-effect transistor is turned on, the negative terminal of the relay coil is grounded, the relay is turned on, and the generator excitation negative signal is output to the generator controller. When the excitation relay control signal is low, the MOSFET is not conducting, the relay is disconnected, the generator excitation negative signal cannot be output to the generator controller, and the excitation winding of the exciter is open-circuited.

6. The apparatus according to claim 5, characterized in that: The input terminal of the main contactor control circuit is the main contactor coil control signal, which is connected to the P-channel MOSFET after passing through a resistor, a Zener diode, and a transistor. When the main contactor coil control signal is high, the P-channel MOSFET is turned on, and the main contactor control signal sent by the generator controller is output to the main contactor coil, turning on the main contactor. When the main contactor coil control signal is low, the P-channel MOSFET is not turned on, and the main contactor control signal sent by the generator controller cannot be output to the main contactor coil. The main contactor is disconnected, thus realizing the power generation system's grid disconnection protection.

7. The apparatus according to claim 6, characterized in that: The system also includes: a fault monitoring circuit for the main contactor and excitation control circuit; The input signals of the fault monitoring circuit for the main contactor and excitation control circuit include: a set of auxiliary contact status signals of the excitation relay in the excitation control circuit, the excitation relay control signal generated by the logic synthesis circuit, the main contactor control signal sent by the generator controller in the main contactor control circuit, and the main contactor coil control signal generated by the logic synthesis circuit. The excitation relay auxiliary contact status signal and the excitation relay control signal are sequentially passed through an XOR gate and a NOT gate to generate an excitation control circuit fault detection signal. The main contactor control signal and the main contactor coil control signal are passed through an XOR gate to generate a fault detection signal for the main contactor control circuit. The fault detection signal of the excitation control circuit and the fault detection signal of the main contactor control circuit are then passed through an AND gate to generate the fault monitoring result signal of the main contactor and the excitation control circuit. The fault monitoring result signal of the main contactor and excitation control circuit is a high-low level signal. A low level indicates that the main contactor and excitation control circuit have a fault.

8. The apparatus according to claim 7, characterized in that: The input signal of the overvoltage delay protection circuit also includes: a high / low level signal output by the discrete signal sampling circuit; When the protection device is in operation test state, the input signal is selected as a high / low level signal; when the protection device is in normal power generation state, the input is the voltage signal of the power generation system voltage regulation point. The input signal of the overvoltage limiting circuit also includes: a high / low level signal output by the discrete signal sampling circuit; When the protection device is in operation test state, the input signal is selected as a high / low level signal; when the protection device is in normal power generation state, the input is the voltage signal of the power generation system voltage regulation point.

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