This paper presents a new method for control of the grid-side converter (GSC) of a doubly fed induction generator (DFIG) system under unbalanced and harmonic grid voltage conditions. The proposed controller is designed based on the sliding-mode control (SMC) method, and operates better than the current ones as the power quality of the DFIG is improved. The fluctuations in electromagnetic torque and stator reactive power are removed by control of the rotor-side converter (RSC). In addition, the GSC keeps the DC-link voltage at a reference value and mitigates not only fluctuations but also oscillations in steady injected active power to the network. Therefore, the output power of the system is free from any fluctuation and distortion. The control algorithm is implemented in the stationary reference frame and it is not necessary to extract voltage or current sequences in either of the converters. The proposed control algorithms are also robust against parameter variations and the resulting dynamic response is fast. The simulation results confirm the validity of the mentioned advantages and the effectiveness of the proposed method.

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In this study, a direct torque and flux control is described for a six-phase asymmetrical speed and voltage sensorless induction machine (IM) drive, based on non-linear backstepping control approach. First, the decoupled torque and flux controllers are developed based on Lyapunov theory, using the machine two axis equations in the stationary reference frame. In this control scheme, the actual stator voltages are determined from dc-link voltage using the switching pattern of the space vector pulse-width modulation inverter. Then, for a given motor load torque and rotor speed, a so-called fast search method is used to maximise the motor efficiency. According to this method, the rotor reference flux is decreased in the small steps, until the average of real input power to the motor reaches to a minimum value. In addition, a model reference adaptive system-based observer is employed for online estimating of the rotor speed. Finally, the feasibility of the proposed control scheme is verified by simulation and experimental results.

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In this paper, the power quality in a wind power generation system is studied. It is shown that adding a Series Grid-Side Converter (SGSC) to the Doubly Fed Induction Generator (DFIG) structure and applying a suitable control algorithm will make the system be able to compensate the adverse effects of the voltage unbalance and consequently can improve the power quality. In order to decrease design complexity and implement the control algorithms in the stationary reference frame, a Sliding-Mode Control (SMC) method for controlling of the DFIG system with SGSC is proposed. One of the advantages of the proposed method in this paper is its robustness to parameter variations both in the DFIG and the connected network. Moreover, the designed controller leads to a fast dynamic response. It should be mentioned that, a coordinated control carries out between SGSC with the other DFIG converters. The simulation results approve the validity of the mentioned advantages and the effectiveness of the proposed method.

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This paper aims to improve transient stability using the Ant Colony Optimization for Continuous Domains (ACOR). This improvement is obtained by solving the Transient Stability Constrained Optimal Power Flow (TSCOPF) problem and extracting the sensitivity coefficients. The presented costs minimization approach requires less execution time to manage energy resources efficiently and compared to other conventional methods, it also outperforms based on statistical indicators such as mean and standard deviation. Furthermore, the sensitivity analysis of the suggested method considers the active power generation of the generating units along with their terminal voltage, which notably decreases the operation cost and reduces risk to the power system. On the other hand, the application of ACOR algorithm can reduce the fuel cost of power system operation to 60,928.36 $/h with a decrease of 15.33 $/h compared to the conventional method with a standard deviation equal to 2.51 $/h and an execution time of 7.66 s. This strategy could be used in power system dispatching. This method is implemented on the New England 39 bus system, and the results demonstrate the method's efficiency compared to other conventional methods.

Advanced Static Var Compensators (ASVCs) are used to improve transient stability of power systems. Transient stability enhancement is one of such applications which employs Flexible AC Transmission System (FACTS). This paper proposes a new method for ealculating the current references for an ASVC. These current references are calculated based on Transient Energy Function (TEF). The simulations have been carried out using CH and Matlab Sirnulink, and the corresponding results are provided