The development of a battery capacity check system for electric locomotives controlled by a single-chip computer (1. The national electric power electronics specialty of Zhejiang University, the discharge current of the battery is a series of pulses, even if the average value is guaranteed to be constant, it is not conducive to the service life of the battery. We set up an LC filter circuit between the battery bank and the BUCK circuit. As shown in the figure, we can use a very simple BUCK circuit and ensure that the discharge current of the battery is constant to prevent the resistance R. Inductance-induced switching over-voltage, anti-parallel in both ends of the resistance of a freewheeling diode.The tube should use fast recovery diode BLCK type main circuit structure pre-filter BLCK circuit 3 charger, discharge machine control circuit charger, discharge machine Control circuit schematic diagram see this part of the circuit by closed-loop regulation and PWM signal generation circuit, IGBT drive and protection circuit, etc. Closed-loop adjustment circuit consists of TL494 integrated error amplifier and R3R4R5R6R8C4 and other components, f is the charging or discharging current detection value, Igd is the charge (or discharge) current setpoint, HS0.1HS.1 from 80C196KBCPU is high Speed ​​output port, where the D/A output is programmed, the PWM signal generation circuit is composed of TL494 and C3R2R7. The product of C3 and R2 determines the frequency of the PWM signal, ie, the switching frequency of the main switch IGBT. We choose 20kHz IGBT drive and protection of electric touch 80C196KB type single-chip microcomputer monitoring system The current helium flow switch circuit charger discharge machine control circuit schematic circuit is mainly composed of Fujitsu's IGBT dedicated drive circuit EXB841 and other components when the main switch IGBT overcurrent When the EXB841 pin 5 outputs a low level, the EXB841's 15 pins are clamped to block the PWM signal and protect the IGBT. In addition, the constant current mode of operation itself has overcurrent protection, therefore, the system reliability is particularly high 4 SCM monitoring system hardware and software design 4.1 hardware design Monitoring system hardware is mainly composed of CPU unit circuit and battery inspection circuit CPU The unit is mainly composed of 80C196KB CPU program memory 2764 address latch 74HCT373 address decoder 74LS138 power-on reset circuit, 12MHz crystal oscillator and display circuit, etc. The main functions of the monitoring system include: battery charging process control function to detect the battery terminal voltage, when each section When the battery terminal voltage is lower than 24V, the charging current value is set to 46.2A. When the voltage of each battery terminal is higher than 2.4V, the charging current value is set as the adjustment of the given value of 23.1A, that is, the D/A output, Through the high-speed output port to achieve programming, from the HSQ1 output PWM signal, filtered as a charging voltage or charging current given value, if take the PWM signal cycle is 4096 machine cycles, the resolution up to 12 in the charging process, The computer detects the temperature of the battery electrolyte, when the temperature exceeds 40*C, the charging current should be halved, and when the temperature exceeds 45C Should stop charging.
Battery constant current discharge process control. The battery group discharges current with a constant current of 46. 2A for 10h, or although the discharge time is not enough for 10h, but the average value of the voltage of each battery terminal has been less than 1. 8V, the single-cell battery voltage cycle detection function can be stopped for discharging. The number of battery sections is 40. The relay contacts are used to switch because only one of the 40 relays can be selected at a time, so a total of 6 signal lines are required. We have 74LS373 to expand an 8-bit output port and use the 6-bit data of this port. , After 3 74LS15 decoder, transistor power amplifier, drive one of the 40 relays, the voltage of each section of the battery is sent to the A/D input port for CPU time-sharing detection. The MCU periodically detects the terminal voltage of each battery, and determines whether the limit exceeds the limit, displays the number and voltage value of the over-limit battery, and the relay used to issue the audible and visual alarm signal has two sets of changeover contacts. Each time the switch is made, the positive and negative two-pole keyboard input functions of the battery are simultaneously switched to four keys including a charge key discharge key and a pause key alarm shield key, and are used to accept artificial operation commands, and the charge current, the battery pack are displayed through the high display function. Total voltage, discharge current, number of the currently tested battery, and terminal voltage.
4.2 system software design software using PL / M language design, there are two parts of the main program and interrupt program. The main program implements analog (charging current, charging voltage, battery total voltage discharge current battery cell voltage, electrolyte temperature, etc.) detection, reading keyboard and executing keyboard commands, numerical display failure judgment and alarm output, etc. Function interruption program is used to control HSO.1, to achieve D / A output, the program immediately sets HSO.1Ton after the interruption of the reset HSO.1 and cycle T after the interrupt set HSO.1 and other three high-speed output port events composed of the main program block diagram see 5 conclusions This article describes the MCU-controlled battery capacity check system for electric locomotives. IGBT is the main switching device. It adopts a BUCK circuit structure and uses a pulse width modulation circuit TL494 as the main control chip, and a high-performance 16-bit single-chip microprocessor 80C196. The monitoring center has high switching frequency, no static audible noise, high current stability and accuracy, simple circuit, small size, light weight, low cost, high reliability, high power factor of the charger, little pollution to the power grid, and battery packs The single-cell voltage circuit has a significant advantage in automatic detection, and it is of practical value. The system was put into operation in March 1998 and it has been running since then. Good condition, popular with users
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