Based on single chip car super capacitor test system design and implementation
With advances in technology, electric vehicle technology is rapid development. Compared to internal combustion engine cars, electric cars have zero emissions, high energy efficiency, low noise, low heat radiation, easy to manipulate and easy to maintain, etc., will be the future direction of automotive development, but also ongoing research hot spots.
Electric vehicle power batteries have the following three categories: fuel cells, batteries and super capacitors. Fuel cells, batteries and super capacitor energy density and power density are complementary . Single-use batteries, fuel cell or super capacitor, it is difficult as a power source for electric vehicles. Hybrid battery is an ideal solution. Use of hybrid battery systems, in particular the use of super-fast charging and discharging capacitor to achieve brake energy recovery, as well as super-energy density to support fuel cell vehicles sustained drive, making the fuel cell / ultracapacitor hybrid drive system consisting of electric vehicles driven into the most good program .
For the vehicle power supply, in order to reach a higher power and energy, super-capacitors are often used in series in the form of multi-block monomer. With the upgrading cascade capacitor, the battery voltage increase as a whole; for the car battery, super capacitor voltage often as high as several hundred volts, but such a peak voltage fluctuation will bring a strong electromagnetic interference, for the capacitance components cause great difficulties in detection. At the same time series super capacitor is often used because of high-current charge and discharge (usually between the 50A ~ 150A), voltage, current changes very rapidly. Medium-sized passenger cars such as the super capacitor to 150A discharge current, the terminal voltage will be within 1 minute from the 300V reduced 70V, and 200V constant-voltage electrical impulse will be in a few minutes when the current is increased from 50A to 150A or so, so quickly and so The charge-discharge rate and magnitude of the noise impact is huge.
Super-capacitor for special working conditions, this paper gives a super-capacitor battery detection system. Through the components of the super capacitor charge-discharge cycle test collect its voltage and current parameters, and compared with the standard parameters, which proved that this system can detect changes in the strong current and voltage for rapid realization of a higher detection accuracy.
A detection system theory and the module for
1.1 Object detection test used on the super capacitor Haiao Wei Technology development Co., Ltd. to provide two sets of tandem asymmetric double-layer ultracapacitor electrode component.
1.2 System Principle describes ultracapacitor management system can achieve the super-capacitor operating current and voltage of the real-time acquisition. Super Capacitor management system as a whole block diagram shown in Figure 1. The system comprises three main modules: Field voltage, current, acquisition and conditioning module (ie, acquisition module), the signal isolation and mcu Signal Processing Module (ie, central processing module), power management module. Acquisition module, the Hall voltage, Hall current sensors, respectively super-capacitor voltage and current on-site collection, collecting the signal through the instrument used to enlarge, and then converted to 4mA ~ 20mA current signal sent to the central processing module. A central processing module, the acquisition module to send 4mA ~ 20mA current signal through the current and voltage transformation, isolation and then zoom, AD converted and sent to the MCU; MCU data processed through the CAN interface sent to the host computer; when the data is detected abnormal MCU output fault signal so that staff can take immediate steps. Power management module for the function modules to provide a stable voltage isolation. Increase the RS232 serial port communications in order to burn MCU program.
1.3 The main modules of the test system were used to achieve the four circuit boards, in order to achieve the three major functional modules - acquisition module, a central processing module and power management module. Acquisition and the beginning of the voltage conditioning board, the central processing board and power board. Below focuses on voltage, current acquisition module and the central processing module implementation.
1.3.1 Acquisition Module in acquisition modules include the collection of bus current, bus voltage, the acquisition of two parts, namely, current collection Figure 2 schematic. Hall current sensor using the measured isolation systems, than traditional sampling-based resistor current divider circuit with high precision, security, performance, anti-interference ability. This selection of Honywell's compensation based on the principle of magnetic Hall closed-loop current sensor CSNK591, measuring range ± 1200A, the linear accuracy of 0.1%, the overall accuracy of 0.5%, the response rate of less than 1μs, fully meet the system requirements. After collecting the signal into a voltage signal-precision resistors, and then amplified by the instrument used for the ± 5V bipolar voltage signal. AD620BR instrumentation system used to enlarge chip, the chip gain is low, with a large common-mode rejection ratio (G = 10, the minimum common-mode rejection ratio 100dB), can inhibit a strong temperature, electromagnetic noise and other factors due to common mode interference. Amplify the signal through the OP27GS chip uplift to 0 ~ 10V unipolar signals sent through the emitter follower transmitter XTR110KU, to 4mA ~ 20mA current signal sent to the central processing module. The reason why the signal would be collected into a 4mA ~ 20mA current signal, taking into account the harmonization of standards and industry interface, and using current conveyor strong anti-interference ability.
The bus voltage is selected based on the collection of the same closed-loop magnetic compensation principle of Hall voltage sensor VSM025A, to achieve the same principles and current collection.
1.3.2 Central processing module to achieve a central processing module is the core of the test system, including the MCU and the AD unit, the second analog signal conditioning unit, fault output unit and CAN interface unit and so on, as shown in Figure 3.
Acquisition module input 4mA ~ 20mA current signal first passes through the second analog signal conditioning unit, for signal transmission, isolation, filtering and amplification. Analog signal isolation many ways, the commonly used method for isolation amplifier, linear optocoupler and voltage frequency conversion, in which a linear optocoupler isolation amplifier and an isolation voltage of a high anti-interference ability, high linearity, but the linear optocoupler isolation circuit complex and require more parameters to adjust, and when the input voltage, poor linearity. Therefore, this choice of BB's completion of high-precision op-amp input ISO124U isolated analog signal of the isolation, after the signal had five first-order Butterworth low-pass filter circuit MAX280 high-frequency interference filter, followed by an emitter follower sent.
Conditioning the collection after the second signal, through the 12-bit high-speed AD7891 sent to MCU. MCU for data processing and data transmission via CAN interface to the host computer. STC selected 8-bit microcontroller family high-speed microcontroller STC89C58RD +. The microcontroller has a strong anti-interference, 4kV fast pulse interference (EFT) and high anti-static (ESD), static electricity can be 6000V, good to meet a super-capacitor high-voltage high-current work environment. The microcontroller can be realized 6 clock mode, the system uses 24M crystal case, the microcontroller operating frequency can reach 4MIPS, equivalent to average rate of 51 series microcontroller runs 4 times.
In addition, the test system set up three-channel fault diagnosis output, can show undervoltage, overvoltage, overcurrent and other states. Test system and the host computer using anti-interference ability, good stability CAN means of communication to ensure the test system into the host computer data reliability.
The actual system have an analog ± 15V, digital ± 5V, analog ± 12V power demand, power management module in the provision of the necessary parts of the system voltage at the same time, simulation, digital circuit isolation, thus avoiding the two types of voltage on the operator. Various parts of the power imports have increased TVS protection against surge voltage to the system damage. At the same time in many power at the entrance to set the corresponding filter circuit, such as the AD at the entrance to an increase of π-shaped power supply filter circuit, a better signal to eliminate the power supply by way of interference.
In addition, the external connections are shielded lines, transmission lines can be stronger to shield the electromagnetic interference. The use of aluminum profiles of all current board packaging, with standard air-line connection with the outside world, so that the protection of the circuit board together with isolation of external magnetic field.
2 Test System Comparison and analysis of experimental results
2.1 The test content test will decide whether to 70A and 150A of the two groups of two modes of super capacitor components in series charge-discharge testing. First of all, constant current charging of the capacitor, when the bus voltage 300V, the converted constant voltage charging, when the bus when the current is reduced to 10A for 70A constant current discharge, such a loop test 5 cycles.
2.2 Experimental results and analysis of Figure 4, Figure 5, Figure 6 shows the two kinds of cases, the test curves. Among them, Figure 4 indicated that 70A and 150A two kinds of standard test cases, the current curve. Figure 5, Figure 6 that the two cases, the voltage curve characteristic. The matching degree between the two can be seen very well. Voltage testing accuracy higher than the current test accuracy, this is because on the one hand the system itself voltage charge and discharge current control accuracy is higher than the other, current sensor placed in the capacitor cabinets and close to the single capacitor, capacitor charging and discharging the noise generated when more serious disturbance. Meanwhile, the Hall current sensor aperture large, through the current bus, still have some gaps, to a certain extent, affect the accuracy of the test. Contrast current curves of each group can be seen as the current increases, the relative error of test results decrease, but the absolute error is consistent, no more than 3A.
This paper presents a vehicle super capacitor test system, the system of compensation based on principles of magnetic Hall closed-loop current, voltage sensor capture bus signals to anti-high-voltage pulse interference STC51 high-speed microcontroller for signal processing, and use of instrument with amplification, current transmission, analog signal isolation, 5-order low-pass filtering and other measures to minimize the signal transmission noise. Through the components of the super capacitor charge-discharge test shows that this system has strong anti-interference ability to detect high precision can be well positioned to meet car super-capacitor high-voltage high-current environment test requirements.
1 Lin Tao, Chen whole world. Fuel cell bus power system structure analysis [J]. Highway Traffic Science and Technology, 2003; 20 (5): 2
2 Xiongqi, Don Han. Supercapacitors in hybrid electric vehicle research [J]. Journal of Zhongshan University (Natural Science Edition), 2003; 42 (suppl) (2)
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