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Control strategy of DFIG in hybrid micro-grid using sliding mode frequency controller and observer

A doubly fed-induction generator (DFIG) has a significant advantage of fast dynamic frequency regulation. However, conventional virtual inertia control (VIC) design only takes frequency into account and may face secondary frequency drop during rotor speed restoration. To solve these problems, the novel decentralised control strategy is proposed for a hybrid micro-grid. Firstly, the load disturbance is considered to enhance control system accuracy, which is estimated by using the state observer based on the dynamic mathematical model. Then, the sliding mode VIC controller is designed by taking advantage of the observed disturbance value and frequency deviation for DFIG output dynamic adjustment according to the conventional frequency control (VIC) model. Furthermore, during DFIG rotor speed restoration, pitch angle control based on the mathematical model is applied for reserve capacity, and a new triggering condition according to the conventional condition is designed, so as to release reserve power at an appropriate time. Finally, the proposed strategy is tested in a typically isolated micro-grid with diesel and DFIG through a simulation and experiment.

Development of a ZVT-PWM Buck Cascaded Buck–Boost PFC Converter of 2 kW With the Widest Range of Input Voltage

This paper describes the development of a new buck cascaded buck-boost power factor correction (PFC) converter of 2 kW with a soft-switching technique. For its wide range of input voltage, it operates in both buck and boost modes. The parameters are properly selected to endure voltage and current stress in all operating ranges. In addition, the electromagnetic interference (EMI) filter is used to reduce the EMI noise and guarantee continuous input current in buck operation. Moreover, the zero-voltage-transient pulse-width-modulation (ZVT-PWM) method is applied to improve the overall efficiency of the converter. The performance of the proposed PFC converter with the widest range of input voltage is evaluated by the hardware experimental test including harmonics analysis based on the International Electrotechnical Commission standard in all operating ranges. Also, the variations of power factor are theoretically analyzed in both buck and boost modes to determine the widest input range of the proposed PFC converter of 2 kW with an EMI filter. These are strongly required to commercialize it in practice. Finally, the efficiency of proposed PFC converter is compared with that of a conventional buck cascaded buck-boost PFC converter under various conditions.

Improving power system stability in the presence of wind farms using STATCOM and predictive control strategy

In this study, a multi-objective predictive control strategy is presented for the stability improvement of a power system in the presence of wind farms and STATCOM. The main contribution of this study is in the multi-objective consideration for controlling the active and reactive powers of the rotor-side converter in each of the induction generators, controlling the voltage of the synchronous generators’ excitation system, and designing the damping controller of STATCOM using the predictive strategy. To reduce the computational burden, and to accurately choose the input paths into the predictive control, the Laguerre functions are used. Also, for reducing the sampling time in the selection of large prediction horizons, the exponential data weighting has been employed. The simulation results were evaluated using MATLAB software in the field of time and frequency under different scenarios. Moreover, the obtained results of each domain are compared using the two techniques of the predictive strategy, i.e. the classic model, Laguerre functions, and also the conventional proportional integral controller. The comparison of these three methods reveals that the functional predictive control outfits the two other controllers in damping of the oscillations.

Single phase thirty one level inverter using only eight switches towards THD reduction

Abstract—This project proposes a single-phase thirty one level inverter with reduced switches, with a novel pulse width-modulated (PWM) control scheme. The Proposed multilevel inverter output voltage level increasing by using eight numbers of switches driven by the multicarrier modulation techniques. The inverter is capable of producing thirty one levels of output-voltage (Vdc, 14Vdc/15, 13Vdc/15, 12Vdc/15, 11Vdc/15, 10Vdc/15, 9Vdc/15, 8Vdc/15, 7Vdc/15, 6Vdc/15, 5Vdc/15, 4Vdc/15, 3Vdc/15, 2Vdc/15, Vdc/15,0, -Vdc/15,-2Vdc/15,-3Vdc/15,-4Vdc/15,-5Vdc/15,-6Vdc/15,-7Vdc/15,-8Vdc/15,-) 9Vdc/15,-10Vdc/15,-11Vdc/15,-12Vdc/15,-13Vdc/15,-14Vdc/15,-Vdc)from the dc supply voltage. This topology achieves very less THD with less number of switches. The proposed systemwas verified through MATLAB simulation.Keywords—Multi Carrier, THD, PWM, Symmetrical, MLI

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NO: 1/103 M. BARANI NAGAR OPPOSITE TO ST. XAVIERS MATRICULATION SCHOOL, kodaikanal, Vannarpettai, Tirunelveli, Tamil Nadu 627003

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