Offshore wind power converter high-reliability operation modes and swapping strategy

Offshore wind power generation has been widely applied. Generally, the offshore wind farms are far from land. Thus, maintenance is inconvenient and the costs for offshore wind power conversion systems are high. Several offshore wind power converter units are parallel connected to meet power capacity and redundancy requirements. However, operating reliability is easily affected by mistriggered switches from complex electromagnetic interference and sudden drops in output current can occur when the inverter modules switch directly. This paper studies high-reliability operation modes and a swapping strategy for offshore wind power converters to address these issues. Different operating patterns are defined based on the output power of the system. By enabling the power switches of the inverter bridges in an interleaved manner, the working patterns are reconstructed. The short-circuited current is suppressed in the power switches caused by the shoot-through of DC-link capacitors. Moreover, the power switches used in different operating modes are activated synchronously and deactivated asynchronously with the mode-swapping signals to optimize the swapping transitions. Finally, the effectiveness is validated on an experimental platform using dual active neutral-point-clamped inverters connected in parallel.