Optimal power transmission in multi-terminal HVDC systems for large offshore wind farms: a matheuristic approach

Nowadays power transmission losses in multi-terminal high-voltage DC (MT-HVDC) systems of large offshore wind farms are the main concerns to wind farm operators. Maintaining the DC voltages and currents within pre-specified limits and simultaneously optimising DC power flows of MT-HVDC systems using optimum droop control settings becomes a complex optimisation problem. This droop control scheme was less explored with power loss minimisation applications due to the difficulties in the optimisation of these droop gain settings. This study presents a new mathematical programming plus meta-heuristic-based optimisation approach to solve this optimisation problem. This hybrid optimisation methodology is also termed as 'matheuristic approach'. The proposed matheuristic method optimises the droop control settings for different operating conditions of offshore wind farms and simultaneously minimises the DC power losses in the MT-HVDC system. The proposed optimisation method has been tested upon a six-terminal HVDC system connected with large offshore wind farms. The superiority of the proposed optimisation method is demonstrated using the steady state as well as dynamic simulation studies. The simulation results show that DC power losses could be reduced significantly by adopting the proposed method to facilitate optimal power flows in the MT-HVDC system of large offshore wind farms.