Optimal power flow in MTDC networks for large offshore wind power plants: Validation of the distributed voltage control strategy

Optimal power flow control remains one of the main challenges to be solved before large multi-terminal dc (MTdc) networks can be successfully developed. This article employs a novel strategy to achieve optimal power flow (OPF) control in MTdc networks for large offshore wind power plants (OWPP). The strategy, called Distributed Voltage Control (DVC), is validated on an experimental low-voltage laboratory setup. The low-voltage dc network is designed to reproduce the behaviour of a high-voltage one. The experimental setup consists of three voltage-source converters connected in a parallel-radial topology with a symmetric monopolar configuration, which is a suitable choice for the initial development of MTdc networks. A large OWPP is emulated using an OPAL-RT real-time simulator. The results obtained showed that the complete system has a very good dynamic response with fast transients lasting less than 100 ms. Furthermore, the DVC strategy controlled the power flow inside the MTdc network with very high precision, as the median deviation was only 0.03 pu. In conclusion, the DVC strategy is well suited to optimally control MTdc networks.