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The new grid codes demand the wind turbine systems to ride through recurring grid faults. Many control strategies have been proposed for the Doubly Fed Induction Generator under single grid fault, but their performance under recurring grid faults have not been studied yet. In this paper, five different control strategies for DFIG to ride through single grid faults are presented, and their performance...
During grid faults, grid codes required wind turbine (WT) to provide dynamic reactive support within tens of ms as well as maintain grid connection continuously, namely low voltage ride through (LVRT). But owing to the limited DC bus voltage, the rotor side convertor in doubly fed induction generator (DFIG) cannot actually output sufficient voltage to provide reactive support until the rotor-side...
Variable speed drives (VSD) constructed with doubly-fed machines (DFM) offer interesting flexibility for power electronic drive design. They also offer opportunities for controlling interactions with an ac grid. Design options are most flexible for the VSD DFM when the machine stator can be operated from an ac or dc source, selected “on-the-fly” as appropriate. This paper presents a SCR-based transfer...
Bearing currents cause a reduction of ball bearing's lifetime in electronically commutated permanent magnet motors. To compensate the lifetime decreasing factors, a tradeoff between special bearings and additional changes in the machine design have to be found. Stator grounding, for example, keeps the bearing voltage low and thus guarantees a long fan system's lifetime, however, results in a higher...
Typical AC traction drive electrical components include the motor, inverter, dc link and filter elements. Drive design parameters and component values are chosen to minimize system-level drive losses. This paper presents a systematic approach for selecting rotor flux magnitude and passive component values in an induction motor drive using a comprehensive loss-minimization algorithm. The total losses...
In this paper, the angle estimation error in the signal injection based sensorless control using analog band pass filter (BPF) is analyzed. The analog BPF has been used to minimize a level of the injection voltage. However, the current which pass through the analog BPF is distorted and the sampled q-axis current is not zero even though the additional voltage signal is injected on the real rotor position...
This paper presents a control method to improve the efficiency and dynamic response of wind energy control systems (WECS) that use a permanent magnet synchronous generator (PMSG) operating under a wide input and load range. An adaptive passivity-based nonlinear controller (APBC) is developed and tested. This controller is designed to overcome the limitations of conventional dq-control methods, which...
This paper presents an improved direct torque control (DTC) method for permanent magnet synchronous motors. The proposed DTC method generates the diver signal with SVPWM for the fixed switching frequency and low torque ripple relative to conventional hysteresis controllers. Different with the popular SVM-DTC, the proposed method obtains amplitude and angle of reference voltage vector directly by the...
This paper presents a saliency-based position sensorless drive of permanent magnet (PM) machines using a single current sensor for cost-effective applications. For the single current sensor system, the dc-link current is measured for the reconstruction of three-phase currents. The phase current reconstruction can only be realized when active voltages are applied. This limitation results in six immeasurable...
This paper presents a simple algorithm for estimation of the rotor position. The injected high frequency voltage is a sinusoidal voltage and is injected into the stator of a motor. An interior permanent magnet synchronous motor (IPMSM) has spatial saliency because d-axis inductance and q-axis inductance are different from each other. The injected high frequency voltage is influenced by saliency. Therefore,...
In recent years, sensorless techniques based on HF carrier injection have become very popular as they are capable to estimate rotor position in a wide speed range. They can provide precise control over interior PMSMs without the accompanying need for a position sensor. However, in surface-mounted PMSMs, the estimation of rotor position is only reliable at light loads due to the very small saliency...
In order to overcome the excitation problem of three-stage synchronous machine(TSM) used as starter for the engine cranking, this paper presented a novel three-phase open-winding structure of the exciter for the proposed machine with the dual-inverter for supplying the integrated AC and DC excitation power. The operation principle of the dual-inverter and the control method of the three-phase AC excitation...
Model reference adaptive system (MRAS) is usually employed for the rotor position/speed estimation in sensorless interior permanent magnet motor (IPMSM) drives, and the adjustment of control parameters in MRAS is a key issue for the IPMSM drive system with the cyclic fluctuating load. In order to avoid the complicated manual tuning of the control parameters, a new MRAS scheme based on fuzzy logic...
Stepper motor drives exhibit advantages like open loop capability, high torque density and lower cost with respect to other brushless servo alternatives. However, the typical performances of conventional open loop stepper motor drives are limited, making them unsuitable where high speeds, fast dynamics and smooth motion is required. They are also easily prone to stall and usually produce loud audible...
Recently, magnetic gearboxes (MGBs) are attracting more followers as they offer great benefits over conventional mechanical gearboxes including contactless operation, lower noise, lower vibration, and they are maintenance-free. Improving MGBs performance is one of the popular topics under research. Axial MGB is one of the magnetic gear topologies that is suitable for applications which require a physical...
This paper proposes a novel wound-rotor machine which has a single-phase stator winding and three-phase rotor windings. The machine is called Single-Phase Wound-rotor Machine (SPWM). The machine can be driven in motoring and generating modes in single-phase grid system. The dynamic model and control system of the machine are also designed. Typically, the double revolving field model is used for singlephase...
Ride-through capabilities of the doubly-fed induction generator (DFIG) during grid fault have been studied a lot. However, the thermal performance of the power device during this transient period is seldom investigated. In this paper, the dynamic model for the DFIG and the influence of the rotor current to the damping time of the stator flux and rotor terminal voltage during the symmetrical grid fault...
New grid codes demand the wind turbine systems to ride through recurring grid faults. In this paper, the performance of the Doubly Fed Induction Generator wind turbine system under recurring grid faults is analyzed. The stator natural flux produced by the voltage recovery after the first grid fault may be superposed on the stator natural flux produced by the second grid fault, and it may result in...
This paper investigates the sub-synchronous resonance (SSR) phenomenon in a series compensated doubly-fed induction generator (DFIG) based wind farms. A detailed linear state space model of a fixed-series compensated DFIG wind farm is presented for different operating point conditions. The model of the system includes a wind turbine aerodynamics, a 6th order induction generator, a 3rd order two-mass...
With the stator directly connected to the grid, doubly-fed induction generator is very sensitive to gird disturbance. However, wind turbines are required to stay connected to the grid for a given time duration during grid fault, according to the low voltage ride-through requirement. The key point of the low voltage ride-through solution is to depress high rotor current during grid fault. This paper...
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