Synchronized current sensing techniques and implementation on dSPACE-FPGA-board using delta-sigma-modulator

This paper shows a current measurement technique, which combines approaches for synchronized inverter current measurement with an advanced system of digital transmission and filtering of current measurement values. The measurement technique gives a significant increase in performance, accuracy and robustness compared to classical measuring with sampled A/D conversion or not synchronized techniques. This advantage is achieved by using a Delta-Sigma-Modulator for A/D conversion and realization of signal evaluation with a sinc³-filter that is implemented in an FPGA. Additionally, the benefits in the precision and robustness of a new synchronized current sampling mode in combination with the digital processing and filtering of measured values are shown. The evaluation of the signals and the control of the inverter system are realized by using an FPGA that is part of the used dSPACE rapid control prototyping system. Digital signal processing and filtering are realized with a new, for the use with the synchronized measurement technique, customized sine³-filter structure that gives best performance and efficiency in combination with the FPGA. A detailed implementation of the technique is shown and the whole system is verified with a laboratory setup of a common 2-level inverter system.