Accurate voltage-to-frequency sensor with galvanic isolation and bandwidth of 375kHz

Abstract

High-bandwidth low-cost MV voltage sensors with appropriate isolation are required in MV power electronic converters for utility and industrial applications. It is especially critical in low-inertia converters (reduced passives) due to the existence of fast dynamics with reduced storage elements (dc-link, filters etc.). In this paper, a MV sensor for sensing a 2kV 16kHz voltage is presented. The sensor is supposed to provide > 160kHz bandwidth which is 10 times the frequency to be sensed, 2% accuracy and >10kV isolation. It is based on voltage-to-frequency (V2F) conversion and optical isolation principles. Compared to existing solutions, the proposed sensor is fast and scalable to MV thanks to the feature of converting analog voltage into digital high-speed square wave through optical enabled MV isolation. The components chosen to build the sensor and the design trade-offs are explained in detail. The sensor delay, accuracy, bandwidth characteristics are shown both at the v2f-sensor output and after frequency to voltage conversion implemented in a FPGA.