Energy dissipation device based on half-bridge sub-modules

Abstract

When the onshore accurate current (AC) grid connected to the offshore wind power voltage source converter-based high voltage direct current (VSC-HVDC) transmission system fails,the surplus power continuously output by the wind farm causes DC overvoltage. The most effective way to solve the surplus power is to use the energy dissipation device to discharge the surplus power. A centralized DC energy dissipation device scheme based on half-bridge sub-modules is proposed to solve the problems of large switching power shock when power devices directly connected in series,difficulty in switching devices at the same time and high cost of distributed DC energy dissipation device. The parameter design method and control strategy of the proposed topology are studied. The solution can overcome the technical difficulties and risks of direct series connection of large-scale power devices,and can gradually reduce the resistance voltage change rate by switching sub-modules,thereby reducing the impact of power discharge on the DC system and the difficulty of manufacturing unloading resistors. Compared with the distributed DC energy dissipation device,the proposed scheme only uses the centralized resistance and omits the bleeder branch in the sub-modules,which greatly reduces the equipment cost. The fault ride-through simulation of the offshore wind power VSC-HVDC transmission system is carried out on the PSCAD platform. And the results show that the proposed centralized DC energy dissipation device topology and control scheme have good performance.

Keywords

• offshore wind power
• voltage source converter-based high voltage direct current (vsc-hvdc) transmission
• direct current (dc) energy dissipation device
• fault ride-through
• offshore converter station
• half-bridge sub-module