Design of Control System for All Fiber Optic Current Transformer

Abstract The fiber optical current transformer (FOCT) features strong anti-interference capability and excellent electrical isolation. To enhance the measurement accuracy of existing FOCT, a control system for the FOCT has been designed. Using Field Programmable Gate Array (FPGA) as the core of the control system, the sampling circuit, signal conditioning circuit and signal conversion circuit are designed. A secondary closed-loop algorithm has been proposed to address reset errors caused by the closed-loop feedback algorithm in the system, correcting the reset height at 2π times. A testing platform was constructed to obtain the ratio error between the actual input current and the measured value of the control system. The results demonstrate efficient data processing within the control system, significantly improving the measurement accuracy of the FOCT. The system exhibits a ratio error of less than 0.1% at a rated current of 600A, meeting the 0.2 class current transformer accuracy requirements specified in International Electrotechnical Commission (IEC) 60044-8 and validating the feasibility of this approach.