Design and development of aviation battery field charging and discharging vehicle

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Design and development of aviation battery field charging and discharging vehicle [Copy link]

Abstract: The design and development of the aviation battery field charging and discharging vehicle adopts electronic integrated modules and developed power supply technology, making the aviation battery field charging and discharging vehicle have high power, small size and high steady-state accuracy. Through its use in aviation units, it is proved that the mobile integrated charging and discharging equipment has important economic and military benefits.

Keywords: Electronic integration module switching power supply technology field charging and discharging vehicle

Aviation batteries are chemical power sources for ground starting, power-on inspection, and onboard backup of aircraft in aviation units and civil aviation airports. They play a very important role in the aviation field. In order to ensure field combat mobility and flight safety and extend the life of batteries, field charging vehicles must be used as a guarantee. At present, there are many types and models of aviation batteries, and most of the battery charging and discharging equipment is in a fixed form. With the rapid development of aviation equipment and switching power supply technology, higher requirements are put forward for the performance, charging efficiency, reliability and maintainability of charging and discharging equipment. Therefore, it is extremely important to develop a new type of charging vehicle. The aviation battery field charging and discharging vehicle is based on the requirements of the national military standard GJB3855-99 and the navigation mark HB6448. The NKR55GLFAJ type second-class chassis is strengthened and modified, and the 24GF AC industrial frequency generator set is used as the power supply. It integrates a charging system of 12 charging modules, a discharge system of 8 discharge modules, and a discharge resistor box as a mobile comprehensive charging and discharging equipment.

1 Design of the charging and discharging vehicle

1.1 Functions of charging and discharging vehicles

(1) Having good mobility and adaptability to field operations;

(2) It has the function of self-generating electricity;

(3) It can intelligently charge and discharge various acid and alkaline aviation batteries;

(4) The charging equipment has soft start and various protection functions.

1.2 Performance indicators

(1) The power supply of the generator set is a three-phase four-wire system, and the line voltage unbalance of 380 (1 ± 10%) V/50 Hz is not greater than 5%;

(2) Automatic charging of 4-way acid batteries that meet the requirements of 6-way alkaline batteries, 40V≤voltage≤60V, current≤20A;

(3) Meet the requirements of automatic charging of 6-way alkaline batteries and 4-way acid batteries, 20V≤voltage≤60V, current≤20A;

(4) It has protection functions such as short circuit, overcurrent, overvoltage, overcharge, overdischarge and reverse polarity.

1.3 Design of the solution

1.3.1 Selection of Class II Automobile Chassis

In order to make the vehicle have good modification performance, reliability, power and economy to meet the requirements of aviation units, the NKR55GLFAJ type II chassis is adopted. After calculation and verification, the quality of the vehicle meets the requirements of the original vehicle modification.

1.3.2 Selection of generator sets

The generator set is the power source of the discharge device. The unit is mainly composed of three parts: engine, generator and electrical control panel. In order to ensure that the power generation has a certain margin, the reliability index should reach or approach the requirements of similar international products, and at the same time, it should have good environmental adaptability. It was decided to use the 24GF AC power frequency generator set produced by Weifang Diesel Engine Co., Ltd. This unit has high reliability (MTBF≥1000h) and is widely used in civil aviation and military fields.

1.3.3 Design of Charging Module

The charging system of the outdoor charging vehicle is composed of 12 modules of chargers. The structural diagram of the charging system is shown in Figure 1. The charging module adopts high-frequency switching power conversion technology and modern control technology. The main circuit of the charging module is composed of a rectifier filter circuit, a high-frequency switching power conversion circuit and a filter circuit. There are many types of high-frequency switching power conversion topology circuits, mainly including half-bridge, push-pull, full-bridge and forward topology structures. The main circuit of this charging module uses a dual forward conversion topology circuit structure, with a working pulse frequency of 50Hz; the phase difference is 180°; the high-frequency transformer uses ferrite materials to reduce high-frequency losses; the ratio is designed to be 5:1; the two sets of rectifier output circuits adopt parallel output, which can increase the working frequency of the output square wave voltage to twice the working frequency of the switch tube, which is conducive to reducing the volume of the output smoothing inductor and the output current pulsation, and improving the current stabilization accuracy. Considering the characteristics of high rectifier output voltage, the main switch tube uses a 900V high-speed IGBT switch device, and the output smoothing inductor uses an iron powder core inductor.

1.3.4 Design of discharge module

The discharge system consists of 8 discharge modules and a discharge resistor box. The structure of the discharge system is shown in Figure 2. The power distribution system and the discharge module provide single-phase control power. Each module can discharge a group of batteries. The current is 0 to 20A and the output of all discharge modules is connected to the discharge resistor box.

2. Solutions to key technologies

2.1 Dual-loop control method of the control unit in the charging module

The control unit is the core of the charger, and its design scheme directly affects the performance of the whole machine. In order to improve the control accuracy and dynamic response speed and further improve the reliability of the system, the control unit adopts a dual closed-loop control method with pulse-by-pulse comparison control. Its control structure diagram is shown in Figure 3. In the dual closed-loop control system, the current controller of the outer loop adopts the PID control method to ensure the zero-static error regulation of the output current. The pulse comparison controller of the inner loop completes the conversion of the output DC signal of the current controller into a pulse width signal and sends the pulse signal to the pulse distribution circuit. The pulse distribution circuit converts the single pulse signal sent by the pulse comparison controller into 4 pulse drive signals corresponding to the 4 main switch tubes, which are isolated and amplified by the drive circuit to drive the main switch tube. While forming the 4-way pulse drive signal, the pulse distribution circuit limits the maximum pulse duty cycle. Since the forward conversion is adopted, according to the transformer volt-second characteristic requirements, the maximum duty cycle Dmax should be greater than 50%. In this design, Dmax=45%.

2.2 Implementation of automatic shutdown circuit

In the later stage of battery discharge, that is, when the battery reaches the rated capacity, the charger can automatically shut down to prevent the battery from overcharging. The shutdown control circuit is composed of a system clock, a frequency division timer, an A/D converter, a dv/dt judgment circuit, a shutdown control circuit, a reference circuit and a shutdown execution circuit. The circuit has two shutdown judgment bases, one is to detect the dv/dt change in the battery terminal voltage, and the other is timed shutdown. The detection of the dv/dt change in the battery terminal voltage is obtained by comparing the data collected by the A/D twice within a fixed time. If the deviation is less than the constant value, it is determined that the dv/dt change in the battery terminal voltage no longer changes. Its purpose is to detect the battery charging voltage value and the voltage change rate value, determine the best shutdown time and implement the shutdown.

2.3 System anti-interference measures

In order to improve the anti-interference ability of the system, the following measures are adopted:

(1) The wiring length between the drive circuit and the IGBT gate emitter is less than 1m, and twisted pair cables are used to improve anti-interference capability. The IGBT drive circuit is shown in Figure 4.

(2) To prevent gate control signal oscillation and reduce IGBT collector voltage pulses, increase the resistance of the IGBT gate series resistor RG.

(3) The two external 47 μF capacitors are used to absorb power supply fluctuations caused by changes in power supply wiring impedance.

(4) To suppress electromagnetic interference from external space, the IGBT module and interface circuit are equipped with a shielding layer grounding technology such as a metal cover, which has a strong suppressive effect on common mode interference, electromagnetic or electrostatic interference.

The switching power supply technology and modern control technology are applied to the field charging and discharging equipment of aviation batteries. The experimental results show that the charging and discharging module has good robustness, can adapt to changes in external conditions, and has a certain anti-interference ability. The power supply technology used in this equipment is advanced, the mobile support capability is strong, and it has high military and economic benefits.