CONTROLLING LING SYSTEM FOR CONSTANT MARGINAL ANGLE OF MULTISTAGED CASCADE-CONNECTED THYRISTOR CONVERTER

摘要

PURPOSE:To improve the regeneration rate of the titled thyristor converter irrespective of operational conditions by a method wherein the amount of variation of the DC output voltage generated by changing the minimum controllable angle of lead is estimated and computed, and the amount of variation of voltage is compensated by the controlling angle of lead on vernia stage. CONSTITUTION:A DC current is detected through the intermediary of an A/D converter 9 and the value of marginal angle is detected from the voltage waveform of the main converter using a marginal angle detector 8, and they are inputted to an arithmetic section 7 through an A/D converter 10. The arithmetic section 7 performs two functions, one is a current controlling function for the command value of the DC current and the other is a controlling function wherein the marginal angle is brought nearer to the set value. Digital phase shifters 11 and 12 convert the digital amount of the controlling angle outputted by the arithmetic section 7 into the phase signal for thyristor, and these outputs are distributed to each thyristor gate using a minimum controllable lead angle circuit 13. When the minimum controllable lead angle is going to be changed, the arithmetic section 7 forcedly changes the controlling angle of lead for a unit converter, with which phase is being controlled, in accordance with the change of said lead angle.