Research And Implementation Of Harmonic And Fast Current Controller Based On MOSFET Control

As the core instrument of electric energy measurement,the accuracy of the electric energy meter can ensure the interests of the entire power grid users.While there are higher requirements for the performance of electric energy meters,the test conditions and requirements in the verification process also need to be improved accordingly.Therefore,combined with IEC standards and R46 international recommendations,GB/T 17215.211-2020 puts forward higher requirements for the test conditions and measuring equipment of electric energy meters.A new load current rapid change test is added to the standard,and technical standards are also proposed for the test conditions of odd harmonics,inter harmonics,and DC and even harmonics tests.Therefore,this article is mainly to design a new type of harmonic and fast current controller,through which the test waveforms required for the above tests are generated to meet the test requirements of these types of tests in the new standard.This article first studies the three types of harmonic test waveforms and their generation methods,points out the defects of the waveform output function of the verification device in the traditional method,and makes improvements on this basis in accordance with the test requirements of the new standard.The use of fully-controlled power electronic device MOSFET as the main switching device in the harmonic and fast current controller solves the limitation of use caused by the uncontrollable devices in the original test device,and also solves the odd problem of directly using the power standard source output in the traditional method.Waveform distortion of harmonics and inter harmonics;at the same time,using the linear characteristics of MOSFETs,it can be used as an electronic load to replace traditional balancing resistors to meet the impedance matching requirements in DC and even harmonic tests.Then,the PWM signal of the electronic switch is precisely controlled by FPGA to realize the time onoff waveform that meets the rapid change of the load current test.Analyze the working principle of the improved harmonic and fast current controller,and complete the design of the overall hardware circuit with the STM32 main control chip as the core,including the main control board,sampling matching module,load matching drive module,power supply module and communication interface circuit,Combined with the software design to realize the waveform switching and load matching functions of the controller,and the application of interface programming technology to realize the automatic control of the upper computer to the test process of the electric energy meter.Finally,a multimeter and a standard power meter were used to perform functional tests on the prototype to verify the accuracy and stability of the load matching function of the controller;the oscilloscope was used to verify the accuracy of the controller’s output waveform;combined with the error data analysis of the meter in actual use,it proves that the controller meets the requirements of harmonic test waveform and load current rapid change test specified in GB/T 17215.