Parallelization of Medium Voltage generator-side converters for Multi-MW wind turbines: Comparison of two topological alternatives

With the increase in the power rating of offshore wind turbines power electronics solutions based on multiple power conversion lines operating in parallel are getting increasing attention. This paper focuses on the parallelization of Medium Voltage (MV) generator side converters for Permanent Magnet Synchronous Generators (PMSG) and on their differences from the Low Voltage (LV) counterparts, which are more commonly investigated. In particular, the paper considers two solutions for the parallel operation of such Voltage Source Converters (VSCs) which are based on isolated DC busses and have different topologies of the magnetic components, i.e. InterPhase Transformers (IPT) and independent inductors. Such alternatives are compared in terms of circulating current, ease of control, and system performance under different operating conditions. A specific controller is proposed that overcomes the main drawbacks of the IPT configuration, proving its overall superior performance compared to the one with independent inductors.