A 21‐level (line‐to‐line) BTB system based on series connection of 16 converter cells. Experimental verification by a 200‐V, 20‐kW laboratory system

A 21‐level (line‐to‐line) self‐commutated BTB (Back‐To‐Back) system based on series connection of 16 converter cells has attractive features as follows: (i) Both active and reactive powers can be controlled independently even in transient states. (ii) The BTB system produces almost sinusoidal voltage at the AC side without performing PWM (Pulse‐Width‐Modulation) control, so that no harmonic filter is required. (iii) The BTB system provides an active power reason as high as 3 ms. This paper presents experimental verifications of the self‐commutated BTB system intended for achieving power flow control in transmission systems. Experimental results obtained by a 200‐V, 20‐kW laboratory prototype confirm effectiveness and validity of both the system configuration and the developed control strategy. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 61– 70, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20324