This paper introduces a three-phase power meter which controlled by the core processor ARM, its hardware and software was described in detail. The meter set power parameters monitoring measurement and display as a whole.Electricity parameters measured by a special chip-CS5463 which is designed for elec- tricity parameters measurement. The electric meter has high integration, low cost, low power consumption and strong anti-jamming capability. The electric meter can meet the energy requirements of the intelligent manage- ment. Meter can communicate with the main controller through the MAX485 chip and it can achieve remote data transmission function.It can easily achieve the function of real-time monitoring, data acquisition and it has a good prospect of application.
Key words：Three-phase power meter;LPC2148;CS5463;ARM
Content
2.Overall design idea of three-phase smart meter hardware
3.Circuit design of each functional module
3.1 Design of three-phase smart meter control system based on ARM
3.2Power detection and metering hardware circuit
At present, the application of electric energy meters at home and abroad is in the stage of popularization of smart meters. With microprocessors as the core, smart meters use digital sampling technology to perform digital calculations and processing on the measured voltage and current, and realize electric energy measurement and monitoring of power, current, voltage and other grid parameter information. With the promotion and construction of smart grids around the world, smart meters will present a huge market demand. The use of a large number of nonlinear loads, such as elevators, uncontrolled rectifiers, variable frequency speed regulators, etc., has caused increasingly serious harmonic pollution to the power grid. At present, electric energy meters and other electrical parameter measurement instruments are designed according to the power frequency. When the input signal contains harmonics, accurate measurement cannot be achieved. Therefore, in addition to accurately measuring electric energy and measuring parameters such as active power, reactive power, current, voltage, power factor, etc. in the power grid, smart energy meters should also have automatic meter reading and data remote transmission functions.
This paper uses ARM chip as the microprocessor to design a smart meter that can realize conditional data remote transmission and has automatic meter reading function. The meter has the advantages of low cost, accurate measurement, good real-time performance and convenient management.
2.Overall design idea of three-phase smart meter hardware
The three-phase smart meter uses the ARM chip-LPC2148 as the microprocessor and the dedicated metering chip CS5463 as the three-phase electric energy data information sampling and processing chip. On the basis of realizing the functions of the traditional three-phase meter, it communicates with the host computer through the RS485 communication interface to realize the remote transmission of data information.
The hardware circuit of the system mainly consists of four parts: (1) ARM core board system; (2) three-phase power sampling and data processing circuit; (3) MAX485 chip and host computer communication circuit; (4) other necessary external devices, such as buttons, displays, etc.
The meter design uses the LPC2148 ARM chip as the hardware structure of the three-phase power meter for the control processor; the power parameter information monitoring uses the power measurement dedicated chip CS5463; the 128×64 dot matrix is used to realize the LCD display function, integrating the power parameter measurement and display functions. The smart meter data remote communication is realized by using the RS485 communication chip MAX485.
3.Circuit design of each functional module
The hardware system circuit of the three-phase smart meter mainly includes the basic circuit of the microcontroller center, the power detection and data acquisition circuit, the power supply circuit, the display circuit and the RS485 communication interface circuit. The LPC2148 main controller reads the data of the three power acquisition modules with the CS5463 chip as the core through the built-in SPI interface, and realizes the data remote transmission function through the built-in communication serial port and the 485 communication protocol.
3.1 Design of three-phase smart meter control system based on ARM
The three-phase smart meter uses ARM chip-LPC2148 as microprocessor, and adopts three dedicated energy metering chips CS5463 to realize grid data information sampling and data processing, and exchanges data with MCU in time-sharing through SPI interface, so as to realize the data detection and sampling function of three-phase power; LPC2148 is connected with MAX485 chip through its own serial communication interface, so as to realize the data remote transmission function.
3.2 Power detection and metering hardware circuit
This circuit uses a dedicated single-phase power measurement chip CS5463 as the core. The circuit design uses three CS5463 chips to measure the power of a single line respectively, and then completes the detection and processing of the three-phase power information in the power grid through data combination. The specific implementation scheme is shown in Figure 2. In the hardware circuit for realizing power detection and metering, an electrical isolation design is adopted between the power line and CS5463. The electrical isolation is achieved through two transformers and a current transformer. Among the transformers, one is an ordinary transformer, which is used to provide the DC power required for the operation of CS5463; the other is a high-precision, low-impedance transformer with very small attenuation and phase delay under higher harmonics, which is used to measure voltage information. The current transformer is used to measure the current information of the power line. A resistor is connected across the secondary of the current transformer to generate the voltage signal required for current sensing for the current channel of CS5463.
The software design of the three-phase smart meter mainly consists of four parts:
(1) LPC2148 main control program; (2) CS5463 data acquisition and processing program; (3) MAX485 communication program; (4) driver auxiliary program for external devices such as keyboard and display.
This paper introduces in detail the hardware principle and software design of the three-phase smart meter based on the ARM chip-LPC2148. The designed three-phase smart meter integrates the electric energy parameter measurement and display functions, and has the advantages of high integration, strong functions, low cost, and strong anti-interference ability. The industrial standard 485 communication protocol is used to realize data transmission, which improves the real-time performance of data monitoring and well meets the requirements of intelligent power management. The experimental test results show that the active metering accuracy and reactive metering accuracy in the data information collected by the three-phase smart meter meet the system design requirements and have high application value.