Hybrid AC/DC Network With Parallel LCC-VSC Interlinking Converters

This paper presents a unified control strategy for parallel LCC-VSCs interlinking converters (IC)s in hybrid AC/DC grids. The parallel LCC-VSCs configuration takes advantage of the low cost of the LCC system as well as the bidirectional power flow capability of VSCs and offers an excellent option for lowering system costs with high performance. Moreover, drawbacks of the LCCs such as low power quality, reactive power consumption, and commutation failure can be addressed by using the parallel LCC-VSCs configuration with proper control and coordination. The proposed unified control system is developed by modifying the LCC's V-I graph to create a droop equivalent along with droop-based control of the VSCs. As a result, it provides voltage/frequency support for the AC and voltage support for the DC sub-grids in various operating conditions. In this paper, the performance of the proposed control strategy under different operation conditions is investigated. Case study results, with a realtime simulator, are provided to verify the effectiveness of the proposed control strategy.