Aircraft power supply system plays an important role in aircraft system. Generator controller (GCU) for monitoring power supply system is an important device to ensure the safe operation of power supply system.
In order to ensure the normal operation of generators and the safe flight of aircraft, it is necessary to regularly test and maintain the fault monitoring ability of generator controller. 。 Based on this, this paper develops an automatic test system according to the component maintenance manual (CMM) of a certain type of aircraft for ground test of generator controller. The purpose is to provide reference for peers. Aircraft power supply system plays an important role in aircraft system. Generator controller of monitoring power supply system is an important device to ensure the safe operation of power supply system. In order to ensure the normal operation of generator and the safe flight of aircraft, it is necessary to test and maintain the fault monitoring ability of generator controller regularly.
Therefore, this paper analyses an automatic test system for the ground test of generator controller. The performance of the test system is not only reliable, intelligent, but also extensible and maintainable. It is important to ensure the maintenance quality and improve the maintenance efficiency of the aircraft generator controller. Aircraft power supply system plays an important role in modern aircraft. With the rapid development of modern aviation industry, the number of Airborne Intelligent Electronic and electrical equipment is increasing, and the requirements for aircraft power supply system, especially for power supply system, are becoming higher and higher. Aircraft power supply system is an important part of airborne electrical equipment. Its function is to supply power to all electrical equipment on the aircraft. Power supply system is a general term for the generation, conversion, transmission and distribution of electric energy and the detection, control and protection of electric energy on aircraft. It includes all the parts from power supply to input of electric equipment.
It is usually divided into two parts: power supply system and transmission and distribution system. The power supply system is the part between the power supply and the power supply bus, and the transmission and distribution system is the part from the power supply bus to the input of the power equipment. Aircraft power supply system consists of main power supply, auxiliary power supply, emergency power supply, secondary power supply and ground power supply, electrical outlet, etc. The main power supply of modern aircraft is a power generation system driven directly or indirectly by an aeroengine. Once the main power supply fails in flight, it is supplied by emergency power supply. Commonly used emergency power sources are aviation batteries and ram air turbogenerators. Because the capacities of emergency batteries and ramjet air turbogenerators are small, they can only supply power to the important electrical equipment on the aircraft to ensure the emergency return to the base or emergency landing of the aircraft. The main power supply of aircraft is provided by the main power generator, which has two kinds: DC generator and AC generator.
It is mainly used to supply power to the main power supply network and electrical/electronic systems of aircraft, as well as to the standby or special AC and DC power supply devices.
With the development of science and technology and aviation industry, the performance and automation of aircraft are increasing day by day. The types and quantities of electrical equipment are greatly increased, so the power consumption is greatly increased. In modern large and medium-sized aircraft, the main power supply system of aircraft consists of high voltage DC system, AC system and hybrid power supply system. AC on aircraft is directly generated by alternator, so as the main power supply equipment on aircraft, alternator plays a very important role in the normal work of aircraft [1]. Aircraft generator control system is a device that provides control and protection for the power supply system of aircraft. Its main function is to make the generator generate electricity normally according to the signal from the automatic control device under manual control. When the power quality meets the requirements, it supplies power to the load. When a part of the power supply system fails, it removes the fault part and ensures that the fault part is removed. Normal power supply for important equipment.
With the development of aircraft power supply system from low-voltage DC power supply system in the early stage to high-power AC/DC power supply system in modern aircraft, its generator control system has also experienced from simple mechanical manual control to microprocessor-based automatic control, which can be summarized as the following stages: piston aircraft generator control system, piston aircraft generator control system and microprocessor-based automatic control system. Turbopropeller aircraft generator control system and jet aircraft generator control system. During the operation of Aircraft Generator system, various kinds of faults may occur. For example, the faults of system components such as generators, voltage regulators, etc. and the faults of power supply lines such as breakdown lines, confluence bars, power balancing links, etc. Faults are also manifested in various forms, such as over-voltage, under-voltage, short circuit, open circuit, over-frequency, under-frequency and voltage instability. Failure to take timely measures will lead to abnormal power supply and even serious accidents.
Because there are many faults in the generator system, the generator controller (GCU) must take corresponding protective measures for different faults. For example, some faults should disconnect the bus bar to connect the circuit breaker BTB; some faults should disconnect the generator excitation control relay GCR and generator circuit breaker GCB; some faults should act immediately; some faults should delay action, etc. It can be seen that for different fault phenomena, corresponding fault measures should be taken. The protective device should be able to correctly judge the fault type, automatically synthesize fault information, selectively disconnect the corresponding switch device, so that the fault part and the power supply part can be isolated from each other, so as to prevent further expansion of the fault and ensure the power supply of important power equipment. The fault location should be correctly judged and isolated from the whole power grid.
However, in order to ensure the vitality of the power supply system, the resection location should be reduced as much as possible. For example, the reactive power unbalance fault in parallel system may be caused by either the power balance loop fault or the voltage regulator fault. Therefore, the BTB should be disconnected first to make the generator withdraw from parallel connection. If the power balance line fails, the fault will disappear after the withdrawal of parallel connection, and the generator will be converted to a separate power supply; otherwise, if the voltage regulator fails, the single generator will be overvoltage or undervoltage fault, and then the generator excitation control relay GCR and generator circuit breaker GCB will be disconnected. Actions should be accurate and timely. They should neither be mistaken nor refused. The main function of generator controller (GCU) is to deal with the faults occurring in the operation of power supply system, disconnect or turn on the circuit breaker or switch used to solve the faults. GCU controls the turn-on or turn-off of relay GCR, generator main contactor GCB, bus connection contactor BTB by controlling excitation circuit. By adjusting the excitation current of the generator, the voltage of the regulating point can be stabilized at 115/200V, thus realizing its voltage regulation function. GCU protects the generator, thermostatic element controller, line and other faults, and chooses different delay time according to different protection items and requirements. The protection functions include over/under voltage protection, over/under frequency protection, output over current protection, differential protection, phase sequence protection, etc. GCU has a perfect BITE system to detect and isolate the faults of single-channel power supply system, locate the faults of components to LRU, and locate the faults of controller to board level, and save the fault information at the same time. In NVM, it provides the basis for ground maintenance and fault analysis; GCU communicates with BPCU through data bus, transfers the status of single channel power supply system for BPCU to judge the status, and transmits it to display on the display. According to the structure and execution principle of generator controller (GCU), to test its fault, the first step is to simulate all the normal operation signals and fault signals that may occur during the operation of power supply system, input these precise signals into GCU according to the input signal standard of GCU, and then detect that the output signal of GCU is Whether it is the corresponding fault response signal, and its analysis, judgment, fault identification and diagnosis, etc. [3]. Generator Controller (GCU) test bench is an automatic test system for ground test of generator controller. It is mainly divided into fault simulation part and detection and analysis part. Like general automatic test equipment, a large number of faults are simulated by computer program and corresponding hardware circuit, and input into the tested equipment, namely generator controller (GCU). Then, the excitation generated by these faults and the corresponding fault codes are introduced into the computer for analysis and processing, and the fault location, fault detection rate and fault isolation rate of the generator controller are obtained. In the process of fault simulation, all key fault modes that need to be monitored by generator controller must be included. The overall design of the system consists of two parts, one is the upper computer part with the computer as the core. Its main functions are to provide man-machine interface, unit test project management, test report generation and control of two programmable power supplies. The control of the programmable power supply is the premise of the test. In over-voltage/under-voltage, overload, differential protection and phase sequence test items, 115V and 400Hz VVVVVF signal source with independent three-phase regulation should be used, while in over-frequency/under-frequency test items, 95V and 1200Hz VVVVVF signal source should be used to provide corresponding generator fault analog signals, which can be realized through COM1 port and COM2 port of computer. Simultaneous or time-sharing control of two programmable signal sources. The second part is the lower computer part, which is based on MCU. It mainly realizes the control of the starting and controlling points of the test items, simulates the generation of the adjustable function generator for under-speed test, measures the delay, and transmits and processes the detection signals such as voltage, frequency and current. The control of start-up point and the generation of delay are the key points of testing. Through the input of fault analog signal, the fault response port of GCU can be detected to generate delay, which is the test flow needed by many testing projects. GCU Intelligent Testing Platform has many test items, and many test items GCU need different test circuits, test equipment and power supply, so the I/O port of 51 MCU can not meet the test needs. 8255 is needed to extend the I/O port of the system. The variety of system testing projects results in a relatively large amount of programming. At the same time, in order to facilitate the expansion of the functions of the future intelligent test bench, the system is connected with 64K external memory, which is time-sharing chip selection through chip selector and 8255. PA port is used to obtain digital signals such as voltage and current transmitted from AD0809. It is used to detect the output of GCU state and feedback of test points. This provides a basis for understanding the fault and working conditions of GCU. The control signal sent by the single chip computer is used to control the starting point of the test item, and the fault response signal of GCU is used as the end point of the test. Two 74HC154 decoders form the encoding of 32 control ports, so that the entire control port has a unique address code. PC port is used for chip selection, triggering and other control of AD0809 and 74HC154. In summary, this paper analyses and studies a ground test method for aircraft generator controller (GCU); the whole system achieves automatic test for 17 items of GCU, such as overvoltage/undervoltage, overfrequency/underfrequency, differential protection, etc. through 51 series of single-chip microcontrollers; the single-chip microcontroller controls the start-point of several test items, and also checks voltage, frequency, delay and so on. The test signal is transmitted and processed; the test control signal is sent to the single chip computer and the test result data uploaded by the single chip computer is received, and the test report is saved; The practice proves that the GCU intelligent test system designed by this scheme meets the requirements of the maintenance manual for GCU components (CMM), and this test method is feasible.