Design of Solar Heating Controller for Oil Tanks in Single Wells of Oilfields Based on ARM

The oil production system in the oil field is relatively sparsely distributed. The oil temperature needs to be heated during the storage and transportation of the oil tank to prevent the crude oil from solidifying and being unable to be transported to the intermediate station for processing. Since the distribution location of each wellhead is relatively far away, it is necessary to control the heating of each individual oil tank. The heating devices currently used are mostly water-jacketed furnaces that use associated gas as fuel or electric heaters that use electricity as energy [1]. Water-jacketed furnaces have the disadvantages of low thermal efficiency, high energy consumption, easy ablation damage to the furnace body, and high repair and maintenance costs. In addition, the exhaust gas emitted during the combustion of associated gas pollutes the environment. Electric heaters have the disadvantages of high power consumption, easy power outages, frequent pipe sweeping, and high cost. This paper proposes a heating system based on solar collectors, heat pump water heaters as auxiliary heat energy supply devices, and ARM as the main controller [2]. The system mode of connecting the heat pump with the solar thermal collection equipment and heat storage mechanism can not only effectively overcome the thinness and intermittency of solar energy itself, but also make full use of solar energy to solve the problem of all-weather heating for crude oil gathering, transportation, storage and transportation, and achieve the purpose of energy saving and reducing environmental pollution. It has great application potential [3].
1 System Function
The solar heating control system of the oil tank of a single well in the oil field mainly realizes the heating of the solar oil tank and the control of the actuator through the ARM controller, temperature acquisition card and touch screen. The solar heating controller system of the oil tank of a single well in the oil field mainly includes oil storage tanks, solar thermal collection fields, hot water tanks, water supply tanks, air source heat pumps, low heat pipes, electric heaters, solenoid valves, 10 temperature sensors and temperature control systems.
The main functions of the system are: when the light conditions are good, the oil tank is mainly heated by the solar thermal collection device; when the light conditions are insufficient, the heat pump is used to supplement the heating of the oil tank; when the heat pump fails, the oil tank is heated by electric heating. The intelligent control device improves the efficiency of solar collectors and the performance of heat pump systems, thereby solving the problem of all-weather heating for crude oil collection, transportation, storage and transport, and also greatly saves the use of electricity [4].
2 System overall design
The solar heating controller for oil tanks in a single well of an oil field is mainly composed of a temperature acquisition card, an ARM controller, a liquid level sensor, a touch screen and an actuator. The working process is that the temperature acquisition card collects 10 temperature signals in real time in a loop. The collected signals are converted into voltage signals through the signal processing circuit, and then the corresponding transmission channel is selected through the analog switch. The data is sent to the ARM processor through the AIN0 input port for A/D conversion. Then the ARM microprocessor makes corresponding judgments on the actuator according to the corresponding conditions, and displays the collected temperature values ​​on the touch screen in real time. The system's working start time, the temperature difference of the circulating pump and other parameters can also be set through the touch screen. The overall design structure of the system is shown in Figure 1.

2.1 Hardware circuit design of the system
The solar heating controller for oil tanks in a single well of an oil field mainly completes the functions of display, storage, control and communication. Considering that this system has high requirements for the microcontroller, especially the high computing speed of the processor, more storage space and external expansion interface are required during the processing, and the traditional single-chip microcomputer can no longer meet the requirements, this design uses Samsung's S3C2410ARM as the microcontroller. The hardware design includes: the design of module circuits such as the minimum system of ARM [5], temperature acquisition card circuit, touch screen circuit, etc. The principle block diagram of the system controller is shown in Figure 2.

2.2 Memory Interface Hardware Design
S3C2410A has independent SDRAM refresh control logic in the chip, which can be easily interfaced with SDRAM. The oil field tank heating controller terminal uses two HY57V561620 chips with 16-bit data width in parallel to build a 32-bit SDRAM memory system, with a total of 64 MB of SDRAM space. The S3C2410A processor supports booting from NAND Flash, which has the characteristics of large capacity and lower price than NOR Flash. The system uses a combination of NAND Flash and SDRAM to achieve a very high cost performance. The system uses a NAND Flash chip with a model of K9F1208UOM and a capacity of 64 MB. The bootloader code and the image file of the WINCE operating system are stored in NAND Flash. At the same time, OM[1:0]=00 is set, that is, the processor boots from NAND Flash. The interface block diagram of NAND Flash and processor is shown in Figure 3.

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2.3 Design of LCD screen interface circuit
S3C2410A comes with an LCD controller, which supports STN and TFT LCD screens with touch screens. This design uses a 3.5-inch TFT LCD screen. S3C2410A comes with a touch interface circuit, including 4 control signal lines (nYPON, YMON, nXPON, XMON) and analog input pins AIN[7] and AIN[5], which control the conversion of X coordinates and Y coordinates respectively.
2.4 Design of temperature acquisition card
The self-designed temperature acquisition card realizes the acquisition, preprocessing and transmission functions of multiple signals. The acquisition points of the system are 10 thermistors. The thermistors use negative resistance temperature sensors from RTC Company to realize the cyclic acquisition of 10 temperatures. In the structural design of the circuit, Huygens bridge is used to collect the sensor voltage signal. In order to improve the measurement accuracy, the chip that provides voltage for the bridge uses TI's precision voltage source chip REF102. Its output reference voltage is 10 V, and the voltage fluctuation is ±2.5 mV. The output accuracy is much greater than the commonly used 10 V linear voltage regulator module. The output current is 10 mA, which meets the output power requirements. The temperature drift coefficient is 2.5 ppm/℃, which effectively reduces the measurement error caused by ambient temperature changes. The temperature bridge circuit uses the instrument amplifier AD620 provided by ADI. The use of this amplifier, on the one hand, because of its high input impedance, realizes the impedance isolation of the acquisition circuit and the control circuit, and improves the measurement accuracy; on the other hand, its integrated characteristics also reduce the measurement error brought to the system by the use of too many peripheral devices, including the white noise effect of the resistor and the temperature drift effect of the device. After the operational amplifier, the output voltage range is 0 V to 3.3 V, which meets the input voltage requirements of the ARM AD module (0 V to 3.3 V), and the voltage size is also within the linear working range of AD620. Since there are 10 acquisition nodes (RT1-RT10), and ARM has 8 10-bit ADCs, of which AIN5 and AIN7 are used as the input of the touch screen, this system design uses the 16-channel analog switch MPC506 provided by TI for cyclic sampling. Its analog signal input voltage range is ±15 V, and the power dissipation is 7.5 mW, which meets the design requirements of the system. The circuit diagram of the acquisition card for one-channel signal acquisition is shown in Figure 4.

3 Software Design
3.1 Transplantation of the Operating System
The touch screen of the solar heating controller for oil field single well oil tanks uses a 3.5-inch TFT LCD screen. The WINCE operating system is transplanted to the ARM processor, and the user interface is developed based on WINCE to realize human-computer interactive control and display. The signal processing platform uses the S3C2410 processor with ARM9 core. Therefore, most of the OAL layer transplantation work can be completed by cloning the BSP of SMDK2410. In addition, the display driver, touch screen driver, GPIO driver and A/D acquisition driver need to be transplanted. In WINCE, the display driver and touch screen driver belong to layered drivers. When transplanting the code of the relevant sample driver, only the code of the PDD layer needs to be modified. The A/D acquisition driver and GPIO driver are implemented in the form of standard stream interface drivers, that is, the stream interface functions of ADC_Init, ADC_Deinit, ADC_Open, ADC_Close, ADC_Read, ADC_Write, ADC_Seek, ADC_IOControl, ADC_Power-
Up, and ADC_PowerDown are implemented.
3.2 Application Development
Under WinCE, application development is for drivers and kernels. Application development under WinCE can be roughly divided into three steps: (1) Install the appropriate SDK; (2) Write code and debug; (3) Release the application. This design chooses to use Visual Studio 2008 development tools, and the application uses the MFC programming interface and a dialog-based model for development.
Because the ARM-based oil field single-well oil tank solar heating controller needs to collect 10 thermistors in real time and in a loop, and also needs to set the system's working parameters through the touch screen, and display system failures, accident alarms, system operating status and other information; the ARM controller makes judgments on the actuator based on the collected temperature values ​​and the set working parameters. Therefore, multi-threading is used in the application to ensure the real-time and efficient operation of the program. Three sub-threads are established in the form main thread: ADC acquisition sub-thread, touch screen setting display sub-thread and system control sub-thread. The system control program flow is shown in Figure 5. [page]

4 System test experiment and results
4.1 Construction of the experimental platform
The test platform of the solar heating controller for oil tanks in a single well of an oil field is shown in Figure 6. The test platform consists of a temperature acquisition card, an ARM controller, a touch screen, and a test board. The test process is as follows: (1) Adjust the 10 analog resistor values ​​on the test board at regular intervals. After adjusting the resistor values, observe whether the display interface of the touch screen can correctly display the collected temperature values ​​in real time; (2) Change the state of the I/O input button of the test board to observe whether the system can alarm in time and display detailed alarm information on the touch screen; (3) Change the working parameters of the system through the touch screen to observe whether the ARM controller can make correct judgments on the actuators based on the system parameters set on the touch screen and the collected temperature values.

4.2 Test results
The test results show that the touch screen can display the collected temperature values ​​in real time. During the test, the resistance values ​​on the test board were adjusted to 65 kΩ, 7.5 kΩ, and 1.6 kΩ respectively. The test results show that the acquisition accuracy is guaranteed to be ±0.5 ℃; for external I/O input, the controller can also alarm in time and display detailed alarm information on the touch screen, such as overcurrent, overload, phase loss, water shortage, full water, etc.; by setting the working parameters of the system through the touch screen, the ARM controller can make correct action judgments on the actuator in a timely and accurate manner according to the parameters set by the system.
The design of the solar heating controller for oil field single well tank realizes the automatic control of solar heating oil storage tanks. The controller terminal uses ARM processor as the core operation and transplants the WINCE operating system to realize a good human-computer interactive interface, thereby completing the use of solar collector field to heat the oil tank under sufficient light conditions and using heat pump to heat the oil tank under insufficient light conditions. It solves the problem of all-weather heating for crude oil collection, transportation, storage and transportation, and greatly saves electricity. After testing, the monthly electricity saving of a single well is 3×104 kW·h. The whole system has good stability, reliable data transmission, no bit errors, and the crude oil temperature at the tank outlet is maintained at 55 ℃-60 ℃, with a measurement accuracy of ±0.5 ℃. The design of the automatic controller makes full use of solar energy, conforms to my country's energy conservation, emission reduction and environmental protection policies, and has high practical value [6].
References
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