Series connected PWM GTO current/source convertor with symmetrical phase angle control

A series connected pulse width modulated current-source convertor (CSC) with symmetrical phase angle control, employing gate turnoff thyristors, is investigated for high voltage applications, where the sinusoidally modulated pulse width is kept sufficiently large to suppress the harmonics by employing a constant modulation index. It should be appreciated that in this system the power flow can be easily controlled, with a high power factor and nearly sinusoidal supply currents. Furthermore, to demonstrate the usefulness of the system, its transient behaviour with a digital PI controller is examined experimentally by looking at its step responses. They are verified by an approximate prediction method without a complete simulation. In addition, the active and reactive powers are examined to investigate their distribution in the system