Reduction of low-order-even-harmonics in grid connected inverters for renewable energy systems using delta-sigma based A/D conversion

Measurement of current and voltage is an important part of an overall converter system. Especially the input signals for the control systems have to be measured with best accuracy to get a proper control result. This paper compares low order even harmonics in the case of a sample-and-hold based analog-to-digital conversion to harmonics with delta-sigma-modulation based analog-to-digital conversion. It is shown that delta-sigma-based analog-to-digital conversion results in a reduction of low order harmonics driven by the measured current and voltage signal with aliasing effects. The resulting harmonics not depending on the switching frequency of the system and are lower than the limits given by IEEE1547.