Inrush current suppression characteristics for HVDC converter

This paper presents novel control methods to suppress the inrush current in soft-start operation for HVDC converter. The HVDC (Higher Voltage Direct Current) system attracts attention to accomplish efficient energy management. However, the inrush current and overshoot of the output voltage which exceeds far larger than the rated values occur when the dc-dc converter in HVDC system starts its operation. For this reason, the soft-start operation is performed to prevent them. In the conventional soft-start operation, the dc-dc converter must start up very slowly to deal with the light load condition. In the proposed method, the fastest speed of the soft-start is obtained because the soft-start speed is determined dependent with load condition. The speed of it is controlled as a approximate function of output current which is obtained from the simulation results in advance. This proposed method to be applied the soft-start of two types. For soft-start operation two different types of function is adapted and compared. In the simulation result using 5W and 800W classes of the dc-dc converters, it is confirmed that the proposed method has a superior soft-start characteristic compared to the conventional soft-start.