CONTROLLER FOR SELF-EXCITED CONVERTER FOR DC TRANSMISSION

PROBLEM TO BE SOLVED: To suppress the generation of low-order higher harmonics, with a control circuit for a self-excited converter for a DC transmission system. SOLUTION: In a DC transmission system, control circuits 110 and 120 for two self-excited converters 41 and 42 for converting AC into DC or vice versa are constituted of vector control systems for converting three-phase AC into the two-phase DC components of active components and reactive components, and they are connected with each other via a DC circuit. The system is equipped with AC current detection means 111 and 112 which detect the AC of the self-excited converter separately for each phase, a higher harmonic control signal making means 117 which detects higher harmonic components that the user wants to reduce from the detected current separately for each phase and multiplies the detection signal by gain separately for each phase, and an addition means which adds a higher harmonic control signal to higher harmonic signals Va, Vb, and Vc separately for each phase to serve as the original form of the AC output voltage waveform of the self-excited converter separately for each phase. This makes pulses by a pulse generating circuit 119, based on the added signal, and controls the self-excited converter.