A recently emerging digital control, namely division-summation (D-Σ) digital control, has been successfully applied to grid-connected inverters and has been extended to UPS applications. The D-Σ digital control can cover the variation effects of wide filter inductance, dc-link voltage and switching period, while without need of abc to dq frame transformation (Clarke or Park transformation), reducing core size and improving stability significantly. Unlike a predictive control, it needs not to define a cost function and it possesses only a tracking trajectory, and unlike a dead-beat control either, it can take care of all the variations. To identify its unique control features, we name it D-Σ digital control which is based primarily on the division-summation process of the control-law derivation. This is just like the fuzzy control which was also named based on the process of fuzzification, inference and de-fuzzification to yield control signals. Conventionally, an inverter was controlled to be a modulated voltage source when adopting an abc to dq frame transformation approach; while, an inverter with the D-Σ digital control is controlled to be a current source, which will result in high stability margin when connected to a weak grid. This talk will present the operational principle, control-law derivation, D-Σ transformation matrix and unique features of the D-Σ digital control. Moreover, comparison between the D-Σ digital control and conventional abc to dq approach will be addressed.

Prof. Tsai-Fu Wu received the B.S. degree in electronic engineering from the National Chiao-Tung University in 1983, the M.S. degree in electrical and computer engineering from Ohio University, in 1988, and the Ph.D. degree in electrical engineering and computer science from the University of Illinois, Chicago, in 1992.

From 1993 to 2012, he was with the Department of Electrical Engineering, National Chung Cheng University as the Department Head, Chair Professor and Vice-president from 2008 to 2011. Prof. Wu also served as the General Manager of E-TON Power Tech. Corporation from 2007 to 2008.

Currently, he is a Professor in the Department of Electrical Engineering, National Tsing-Hua University. His research interests include development and modeling of power converters, design and development of smart DC micro-grid systems, and design and development of D-Σ digital controlled inverters which can achieve grid-connection, rectification, APF, STATCOM and UPS functions. In 2006, he was awarded as an Outstanding Researcher by the National Science Council, Taiwan.