| 摘要 |
PURPOSE: To keep a margin angle with which the commutation failure can be avoided by a method wherein the result which is obtained by adding the average level of a ripple component included in a DC current to the ripple component is used as a phase control angle signal. CONSTITUTION: A ripple component Im1 is amplified by an amplifier 23 and used as a control angle modulation signal Δα1 . When an absolute value output circuit 41 receives the control angle modulation signal Δα1 , the circuit 41 outputs the absolute value |Δα1 |. A primary delay circuit 42 outputs the average level αε1 of the absolute value |Δα1 |. An adder 43 adds the control angle α1 of a constant margin angle controller 20 to the average level αε1 and outputs the result to a minimum value selecting circuit 21. With this constitution, if the ripple component Im1 is superposed upon a DC current Id1, the control angle (average level αε1 ) corresponding to the ripple component Im1 is added to the control angle α1 generated by the constant margin angle controller 20. As a result, if the phase of an AC/DC converter is controlled in accordance with the control angle α1 , the margin angle γ1 of the AC/DC converter is reduced and the commutation failure can be avoided. |
