Research On New Electronic Transformers And Merging Units

The sampling frequency of the electronic transformers and merging units on the market is low,and its technical research and equipment development have been focused on meeting the needs of relay protection and substation integrated automation,resulting in the output signals cannot be directly used for power quality monitoring and analysis,this research has designed a new type of electronic transformer and merging unit with high sampling frequency.It solves the problem that the current sampling frequency of the electronic transformer is low and not 2 to the power of N,so that the sampling frequency reaches 512 points/cycle,the sampling module cut-off frequency is at least 2.5KHz,and the 50 th harmonic can be accurately restored,and the sampling precision is achieved.The0.2-level accuracy requirement meets the needs of power quality analysis.Therefore,for this new type of electronic transformer and merging units,this paper has completed the following work:Fully researched the current research status and development prospects of electronic transformers and merging units.Based on this,the sensing principle of "Rogowski coil +LPCT" combined current transformer and coaxial capacitor voltage transformer with high sampling frequency is introduced.Finally,its advantages are briefly introduced.Research on new electronic transformers that meet the needs of power quality analysis.First,the module design of the collector part of the electronic transformer is included,including signal conditioning circuit design,A/D chip selection,CPU chip selection and power module design.Secondly,based on the signal conditioning circuit,Matlab modeling and simulation analysis is performed on two new types of electronic transformers,including the new electronic transformer sensor head equivalent circuit,integration circuit,filter circuit and phase shifting circuit.In the integration circuit,Matlab simulation and comparative study are carried out on analog integral and digital integral respectively,and an improved composite integrator is designed to improve its accuracy.Finally,a new second-order low-pass filter circuit is proposed and designed to meet the cut-off frequency requirements.The simulation results show that the designed voltage-current combined electronic transformer meets the requirements of high sampling frequency.According to the technical requirements of the merging unit,a hardware architecture scheme based on FPGA+ARM is proposed.The data restoration module based on FPGA,the data processing module based on ARM and the Ethernet output module based onIEC61850-9 standard are studied.It mainly researches and designs its data restoration module,including decoding and verification module,data synchronization module and FIFO data sorting module.According to the data synchronization module,a new synchronous sampling algorithm is proposed,and each module is implemented by Modelsim software.Simulations verify the correctness of the design method.Secondly,the data processing module's digital filtering,rms value and phase calculation,phase compensation and other related algorithms are studied and analyzed.Finally,the selection of Ethernet controller and the hardware connection between CS8900 and ARM are introduced.To verify the correctness of the electronic transformer and the merging unit system,perform sampling accuracy test and temperature test on the voltage-current combined electronic transformer,and perform sampling integrity test and sampling accuracy test on the merging unit.The test results show that the performance indicators of the electronic transformer and the combined unit system of this design meet the design requirements and meet the requirements of power quality analysis.Finally,the full text is summarized and a further research plan is proposed.