Investigation of a New Voltage Balancing Circuit for Parallel-connected Offshore PMSG-based Wind Turbines

Parallel connection of wind turbines (WTs) is beneficial in high-power applications. For successful operation of parallel WT-based energy conversion systems, a well-regulated voltage is needed at the collection point. Due to wind speed variation, the generated voltage from each WT may differ from one to another. Conventional solutions use regulating converters with full power rating. In this paper, a new concept is presented which depends on using fully-rated uncontrolled rectifier bridges for AC-DC conversion, and partially-rated fully-controlled bridge rectifiers which are used as voltage tuners to guarantee the flow of desired maximum power point DC currents through the parallel connected branches. The proposed system is simple, cost effective, reliable and efficient. The main drawback of the proposed system is the critical need for filters and VAR compensators on the AC side to ensure acceptable performance of the WT generator. Also, smoothing reactors are needed on the DC side for filtering of the transmitted DC current. A simulation model has been built to validate the proposed concept, and the simulation results show the effectiveness of the approach.