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Summary form only given. This paper describes a modified phase-shifted carrier-based pulsewidth-modulation (PSC-PWM) scheme for modular multilevel converters (MMC). In order to reduce the average device switching frequency, a reduced switching-frequency (RSF) voltage balancing algorithm is developed. This paper also proposes a circulating current(More)
This paper presents an analysis and control design of a doubly-fed induction generator (DFIG)-based wind generation system operating under unbalanced network conditions. A DFIG system model in the positive and negative synchronous reference frames is presented. Variations of stator active and reactive powers and generator torque are fully defined in the(More)
This paper presents a new direct power control (DPC) strategy for a doubly fed induction generator (DFIG)-based wind energy generation system. The strategy is based on the direct control of stator active and reactive power by selecting appropriate voltage vectors on the rotor side. It is found that the initial rotor flux has no impact on the changes of the(More)
This paper proposes a new direct power control (DPC) strategy for a doubly fed induction generator (DFIG)-based wind turbine system. The required rotor control voltage, which eliminates active and reactive power errors within each fixed time period, is directly calculated based on stator flux, rotor position, and active and reactive powers and their(More)
This paper describes the use of voltage source converter (VSC)-based HVDC transmission system (VSC transmission) technology for connecting large doubly fed induction generator (DFIG)-based wind farms over long distance. The operation principles of the proposed system are described, and new control strategies for normal and grid fault conditions are(More)
  • Lie Xu
  • IEEE Transactions on Power Electronics
  • 2008
This paper proposes a coordinated control of the rotor side converters (RSCs) and grid side converters (GSCs) of doubly-fed induction generator (DFIG) based wind generation systems under unbalanced voltage conditions. System behaviors and operations of the RSC and GSC under unbalanced voltage are illustrated. To provide enhanced operation, the RSC is(More)
System control for dc microgrids with variable generations and energy storage is proposed in this paper. An autonomous three-level control strategy is proposed for dc microgrids with selective slack terminal(s) assigned to each operation level. The system operational status is acknowledged via the common dc voltage and the transitions between different(More)
This paper presents a hybrid modular multilevel converter (MMC), which combines full-bridge submodules (FBSM) and half-bridge submodules (HBSM). Compared with the FBSM-based MMC, the proposed topology has the same dc fault blocking capability but uses fewer power devices hence has lower power losses. To increase power transmission capability of the proposed(More)
This paper presents a predictive current control (PCC) strategy for doubly fed induction generators (DFIGs). The method predicts the DFIG's rotor current variations in the synchronous reference frame fixed to the stator flux within a fixed sampling period. This is then used to directly calculate the required rotor voltage to eliminate the current errors at(More)