A 21-Level (Line-to-Line) BTB System Based on Series Connection of Sixteen Converter Cells

—Experimental Verifications by a 200-V, 20-kW Laboratory System—

Abstract

A 21-level (line-to-line) self-commutated BTB (Back-To-Back) system based on series connection of sixteen 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 (Pulth-Width-Modulation) control, so that no harmonic filter is required. iii) The BTB system provides an active power response as high as 3ms. 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.