Simulation-based optimisation of LCC-HVDC controller parameters using surrogate model solvers

This paper proposes the use of surrogate model optimisation methods to solve box constrained LCC-HVDC controller tuning problems. The tuning problem is the selection of the proportional-integral controller gains and voltage-dependant current order limiter parameters of an LCC-HVDC link subject to two operational scenarios and a set of large-signal disturbances. The solvers using recently proposed surrogate model methods performed either similarly to or significantly better than solvers using mature methods of the types found in PSCAD/EMTDC, thus confirming the suitability of these surrogate model solvers for simulation-based optimisation of LCC-HVDC controllers

Independent-phase current control of a three-phase VSC under unbalanced operating conditions

This study presents an independent phase-current-control architecture for a three-phase voltage source converter. It comprises three independent single-phase phase locked loops (PLLs), and a dual-loop scheme including an outer loop (responsible for active power and ac voltage control) and three similar inner current control loops. To obtain reliable phase-tracking, an enhanced second-order generalised integrator-based PLL is developed. The phase-tracking angle is strategically selected from the three PLLs to minimise the impact of imbalance-induced distortions. To validate the proposed control scheme, extensive simulations are conducted for a 101-level, 500-MW, 500-kV (dc) half-bridge modular multi-level converter in PSCAD/EMTDC. The simulation results prove that the proposed scheme enables the system to ride through unbalanced conditions effectively and reliably

Single-Switch Resonant Soft-Switching Ultra-High Gain DC-DC Converter with Continuous Input Current

An ultra-high gain DC-DC converter with single-switch structure is introduced in this paper. Full soft-witching is provided by simultaneous use of quasi-resonant performance of one resonant tank and leakage inductance of a three-winding coupled inductor (CI). Adopting the secondary and tertiary windings of the CI in separated voltage multiplier cells enables the converter to provide ultra-high voltage gain. The reverse recovery problem is resolved thanks to the quasi zero current switching performance of nearly all diodes, especially output diode because of the second resonant tank, so the total electromagnetic interference is significantly reduced. Continuous input current with low ripple expands the application of the proposed converter, especially in renewable energy applications. Steady-state performance and design considerations of the introduced converter are analyzed thoroughly and compared with recently introduced converters to establish its merits. Experimental results of a 200 W prototype are given to validate its analysis and performance.publishedVersionPeer reviewe