Control of Dynamic Capacitor

Industrial plants are faced with stringent requirements by the utility to maintain a near unity power factor. These plants have traditionally utilized switched capacitor banks as a cost-effective means for power factor correction (PFC). However, if there is a significant level of harmonics present in the current that is disturbing the neighboring loads, then a separate unit for harmonic filtering is required as well. By the time a realistic system is configured, significant cost and complexity are encountered. The concept of a dynamic capacitor (D-CAP) was previously introduced as a means by which to achieve dynamic VAR injection as well as active harmonic filtering in one single integrated unit. The topology consists of taking an existing asset like a PFC capacitor, adding a pair of ac switches and small LC components per phase, and thereby realizing an asset with augmented functionalities. Although the power stage is simple, the underlying control is very challenging. This paper discusses the intricacies of controlling such an architecture and provides keen insights into how one would go about designing a controller.

[1]  Subhashish Bhattacharya,et al.  Active filter system implementation , 1998 .

[2]  Deepak Divan,et al.  Dynamic Var/Harmonic Compensation with Inverter-Less Active Filters , 2008, 2008 IEEE Industry Applications Society Annual Meeting.

[3]  D. Divan,et al.  Voltage Synthesis Using Dual Virtual Quadrature Sources - A New Concept in AC Power Conversion , 2008, 2007 IEEE Power Electronics Specialists Conference.

[4]  Donald F. Miller.  Application Guide for Shunt Capacitors on Industrial Distribution Systems at Medium Voltage Levels , 1976, IEEE Transactions on Industry Applications.

[5]  S.M. Silva,et al.  Performance evaluation of PLL algorithms for single-phase grid-connected systems , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..

[6]  Laszlo Gyugyi,et al.  Power electronics in electric utilities: static VAR compensators , 1988, Proc. IEEE.

[7]  C.W. Taylor,et al.  Benefits of SVC and STATCOM for electric utility application , 2003, 2003 IEEE PES Transmission and Distribution Conference and Exposition (IEEE Cat. No.03CH37495).

[8]  Hirofumi Akagi,et al.  Active Harmonic Filters , 2005, Proceedings of the IEEE.

[9]  Leonardo A. B. Tôrres,et al.  Comparison of Three Single-Phase PLL Algorithms for UPS Applications , 2008, IEEE Transactions on Industrial Electronics.

[10]  Bogdan M. Wilamowski,et al.  Active Filter Implementation , 2011, Fundamentals of Industrial Electronics.

[11]  D. Divan,et al.  Thin AC converters — A new approach for making existing grid assets smart and controllable , 2008, 2008 IEEE Power Electronics Specialists Conference.