Optimum voltage control for loss minimization in HVDC multi-terminal transmission systems for large offshore wind farms

An optimal power flow based control scheme is proposed in order to minimize the losses in multi-terminal HVDC systems for large offshore wind power plants. The scheme optimizes system power flows while delivering the generated wind power to the terrestrial AC grid (or grids). The proposed scheme is compared to droop control schemes in two case studies in order to illustrate the power loss reduction achieved. Dynamic simulations have been provided in order to show the dynamic behavior of both the controller and the robust operation for wind speed changes and when a communication fault occurs.

► We design an algorithm based on an OPF approach ensuring loss minimzation in HVDC multi-terminal transmission systems. ► We compare the control scheme based on this algorithm with voltage droop control. ► Voltage droop control does not lead to optimal efficiency for all the range powers generated by wind farms. With droop control, it is only possible to maximize efficiency for a single operating point which is the nominal wind farms power. For lower generation power, efficiency is not maximized. ► The proposed control scheme reduces significantly losses without a large investment, assuming that communication systems are already available as they are needed for the protections.