A Comparative Study on Power Quality Standards and Interaction Analysis for LVDC Systems

Abstract

The high penetration of distributed renewable energy resources (DERs) and various fast increasing direct current (DC) loads significantly facilitate the development of low voltage DC (LVDC) systems. Novel power electronic devices further provide opportunities for the flexible interconnection of alternating current (AC) and DC networks. However, there is still a lack of international standards concerning DC power quality. In addition, it is not clear whether the relevant power quality research applies to the LVDC systems. In this paper, a definition of the DC power quality issues is given based on the existing IEC and IEEE standards and codes and the detailed reasons for the typical DC power quality events. Then, the correlation between DC power quality phenomena, which plays an essential role in the formulation of DC power quality standards, is illustrated and quantified. Moreover, the influence on DC ripple, DC unbalance and oscillation with AC/DC interconnection is analyzed. The resulting comparative study in this paper provides a reference for formulating the definitions and constraints of LVDC power quality issues, which could strongly support the future DC power quality standard enaction.