LAUSR

Grid faults constitute the main challenge for distributed generation, especially permanent magnet synchronous generator (PMSG)-based wind turbines connected to the grid via back-to-back (BTB) converters. On the other hand, grid codes enforced wind turbines to aid network and accomplish low-voltage ride-through (LVRT) requirements during grid faults. DC-link overvoltage suppression without external devices and reactive current injection to the grid in symmetrical and asymmetrical faults were the main required subjects in different grid codes. Reactive current injection may lead to overcurrent in one or two phases during asymmetrical faults. This paper presents solutions to accomplish LVRT requirements during grid faults, including dc-link overvoltage suppression by improving BTB converter's controllers and the design of active power limitation to maintain the peak current of the grid side inverter in a safe range during different asymmetrical grid faults. In fact, by controlling generation of PMSG active power directly with grid side inverter, the peak current remained in the safe limit and required reactive current, including negative-sequence component can be injected to the grid. Furthermore, the grid side active power oscillation and dc-link voltage ripple can be suppressed by using the proposed controller. Simulation results showed the validity and efficiently of the proposed control approach in different conditions.