Characteristic analysis of a 2MW wind power system with doubly-fed induction generator (DFIG) is carried out. In the analysis, tower shadow effect that occurs in case of downwind turbine remarkably is considered. Tower shadow effect is modeled as a variation of the output power. Stator-field-oriented vector control is applied to the control system in order to compensate the variation. Furthermore, influence of the moment of inertia against the rotor input in considering of the tower shadow effect is clarified by computer simulation.Index Terms--Wind power system, tower shadow effect, downwind turbine, doubly-fed induction generator.
A boost converter is used in various applications to obtain a higher voltage than the input voltage. One of the current main circuit systems for hybrid electric vehicles (HEVs) is a combination of a two-phase boost converter (parallel circuit) and a three-phase two-level inverter. In this study, we focus on the boost converter to achieve even higher efficiency and propose an interleaving scheme for a boost converter suitable for a three-level inverter (series circuit). The series circuit has two capacitors connected in series and makes it suitable as a power supply for a three-level inverter. We analyze the input current ripple of the series and parallel circuit in order to show the superiority of the series circuit. Furthermore, we propose a novel output voltage control strategy using an optimal regulator, namely a Linear Quadratic Regulator (LQR), for the series circuit. As a result, we found the input current ripple of the series circuit is smaller than the parallel circuit and demonstrated the superiority of the series circuit. The simulation and experimental results show the effectiveness of the proposed interleaving scheme and optimal regulator.
This paper presents a new PWM method with suppressed the neutral point potential variation of three level inverter for AC servo motor drive. The basic idea is that the vector output intervals corresponding to increase or decrease of neutral point potential during one sampling period are decided to equal. The authors will show the following simulation and experimental results: 1) In case of without suppression, the variation width of neutral point potential become large, and the deviation of neutral point potential produce the distortion of output current waveforms. 2) In case of with suppression, the variation width of neutral point potential is reduced. Simulation and experimental results are presented to confirm the performance of proposed method.
Three level inverter has several advantages of large capacity, large voltage and low current waveform distortion. However, there is an important problem of neutral point potential variation in three level inverter. The variation causes an unbalance in the DC link voltage levels and current waveform distortion. In this paper, we propose a new method to control the neutral point potential. First, the neutral point potential variation in three level inverter for permanent magnet synchronous motor drive is analyzed by state variable method and is calculated on the basis of the analytic results. Second, using the estimated value, proposed compensation for the variation can be done. Third, analytic and experimental results of proposed method are compared with the results of feedforward compensation by simply adjusting the vector output intervals.
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