Design Of Three-phase Smart Meter Based On Shunt Current Sensor

With the development of intelligent power grid, the technical requirements for smart watt-hour meter is more and more high, the electromagnetic current transducer of small size is commonly used to transform the current signals in three-phase smart watt-hour meter at present, this kind of current sensor has some issues such as high cost, easily DC saturated, small measurement range and vulnerable to external electromagnetic interference and so on, but the shunt current sensor has great advantages in the cost, size of the installation, resistance to DC saturated and anti-electromagnetism interference ability in comparison with the electromagnetic current transducer, this paper have been aimed at the technical bottleneck that the shunt current sensor applies to three-phase smart watt-hour meter, put forward a solution with strong commonality and high reliability, designed a new smart three-phase watt-hours product according with all technology standard requirement of national grid so as to promote the shunt current sensor in the application of three-phase smart watt-hour meter,especially in the application of preventing electric larceny with strong magnetic.This paper firstly introduced the research background of the subject, expounded the working principle and application situation of several current sensors commonly used in watt-hour meter, and analyzed the technical bottleneck that the shunt current sensor applied to three-phase watt-hour meter,and then summarized and analyzed the advantages and disadvantages of three typical solutions proposed based on the technical bottleneck in the current market, and put forward a more feasible solution based on these solutions.In the design of system hardware circuit, designed the independent power of measurement modules and the power of function modules according to the solution of electrical isolation requirement; summarized the anti-disturbance measures in AC signal acquisition, and improved the structure of traditional shunt; analyzed the operating principle and performance characteristics of SOC measurement chip MSP430FE425; designed the data communication interface module dedicated borrowing ideas from RS485 bus; designed strong magnetic inspection module that could detect external constant magnetic field and alternating magnetic field outside the watt-hour meter so as to meet the demand of preventing electric larceny; designed the corresponding real-time power pulse output circuit according to the definition of quadrant electricity; at last, this paper introduced the circuit design of the GPRS module and carrier module which have been commonly used to realize remote meter reading.In the design of system software, the software system was divided into measuring software, data communication interface software, function management software three parts using modular design thought.emphatically introduced measurement algorithm theory of ESP430CE1 module as well as measurement data software processing methods; formulated the data communication protocol between the master control MCU and three SOC measurement chip ,and meanwhile,illustrate the design process of data communication interface software.Finally, the accuracy experimental and EMC performance experiment was done with the product prototype, and carried on the experimental analysis. test result of three kinds of influence error experiment which were AC current circuit with DC and accidentally harmonic influence experiment , alternating magnetic field influence experiment and constant magnetic field influence experiment showed that the three-phase watt-hour meter designed in the subject had great breakthrough in the performance of resistance to DC saturated and preventing electric larceny with strong magnetic ,had achieved the expected design goal.