The Startup and Shutdown Strategies Design and Verification for Hybrid DC Grid with Renewable Power Generation

With the rapid growth of renewable energy power generation, hybrid DC grid that combines line commutated converter (LCC) and voltage source converter(VSC) has a promising future for engineering utilization. However, the existing startup strategy of point-to-point DC system cannot be applied to hybrid DC power systems, due to the different characteristic brought by multi-branch, multi-converter, multisource and multi-node. This paper proposes the startup and shutdown strategies for hybrid DC grid which interconnect LCC-HVDC and VSC-HVDC via a DC-DC converter, which comprehensively considered the system topology, area and converter capacity. A series of operational and control scenarios of the DC grid are verified with the hardware platform, including the startup and fault shutdown. The results show that the DC grid can be started safely and stably, and also proved the effectiveness of this method which can prevent over-voltage and over-current phenomenon during the transient progress.