| 摘要 |
PROBLEM TO BE SOLVED: To enable filtering of a DC system, without requiring an additional circuit by a method wherein a common capacitor star point is connected to a voltage intermediate circuit via an RC element. SOLUTION: A common capacitor star point 26 is connected to a positive. terminal 12 of a voltage intermediate circuit 11 via an RC element 38 consisting of a capacitor 36 and a resistor 37 for loop back. Although the sudden change of a DC component is not completely eliminated by the loop back, the change can be restricted within an allowable rate, for instance 500 V/μs. In a 1 MVA/4 kV converter which, for instance, operates at a switching frequency of 50 Hz, if the RC element consists of the capacitor 36 with a capacitance of 82.9 nF and the resistor 37 with a resistance of 603 Ω, the loss of a converter is 341 W and the gradient dV/dt of a DC system is 495 μs. Therefore, the capacitor 36 of the RC element eliminates a steady-state current flowing through the resistor 37 of the RC element, and vibrations is attenuated by the braking action of the resistor 37. |
