Enhancing fault ride‐through capability of DFIG with modified SMES‐FCL and RSC control

Abstract

For grid-connected doubly fed induction generators (DFIGs), fault ride-through (FRT) capability and transient stability are vital problems that urgently need to be addressed. To overcome these problems, a novel superconducting magnetic energy storage-fault current limiter (SMES-FCL)-based protection scheme by modified control of superconducting coil (SC) and rotor-side converter (RSC) is investigated here. A rotor-side mathematical model is used to estimate and optimise the SC inductance parameter. Two modified control strategies of SMES-FCL cooperative operation and positive-sequence d - q current modification (PCM) are proposed to control the SC and RSC for enhancing the transient stability of the overall DFIG system. In addition to maintaining good FRT performance from the SMES-FCL on stabilising the electromagnetic torque, DC-link voltage, active and reactive power, and stator and rotor current during grid fault, the PCM control is also demonstrated in the simulations to suppress the transient oscillations and thus to shorten the recovery time after grid fault. Meanwhile, compared with conventional SMES-FCL scheme, the requirement of SC current capacity is much lowered for smoothing the DFIG output power under a varying wind speed condition and for enhancing the FRT performance under a grid fault condition.