In this paper, a novel risk-based, two-objective (technical and economical) optimal reactive power dispatch method in a wind-integrated power system is proposed which is more consistent with operational criteria.  The technical objective includes the minimization of the new voltage instability risk index. The economical objective includes cost minimization of reactive power generation and active power loss. The proposed voltage instability risk employs a hybrid possibilistic (Delphi-Fuzzy)-probabilistic approach that takes into consideration the operator’s experience, the wind speed and demand forecast uncertainties when quantifying the risk index. The decision variables are the reactive power resources of the system. To solve the problem, the modified multi-objective particle swarm optimization algorithm with sine and cosine acceleration coefficients is utilized. The method is implemented on the modified IEEE 30-bus system. The proposed method is compared with those in the previously published literature, and the results confirm that the proposed risk index is better at estimating the voltage instability risk of the system, especially in cases with severe impact and low probability. In addition, according to the simulation results compared to typical security-based planning, the proposed risk-based planning may increase the security and economy of the system due to better utilization of system resources.

This paper deals with the simulation of eight bus system having fixed capacitor and thyristor controlled reactor. The system is modeled and simulated using MATLAB. The simulation results are presented. The power and control circuits are simulated. The current drawn by the TCR varies with the variation in the firing angle. The simulation results are compared with the theoretical results.

This study addresses the problem of controlling a variable- speed wind turbine with a doubly fed ‎induction generator (DFIG) by control System that called One-Cycle control (OCC). Generator-side converter regulator speed and Grid-side converter controls reactive power and voltage of the DC-Link. Proposed method under different conditions such as load change, fault and nonlinear loads are studied. The whole DFIG wind turbine model is set up in Matlab/Simulink and simulation has been done for a sample network in different conditions. Comparisons of OCC and PWM control methods have been presented through simulations where OCC has demonstrated better features compared to PWM control.

The most commonly used variable speed wind turbine is based on Doubly Fed Induction Generator (DFIG). To control the reactive power of DFIG-based wind turbines, several methods are suggested that controls the reactive power of the DFIG with slow dynamics and considerable ripples. This paper proposes a new control method based on the adaptive reference model which controls the active and reactive powers of DFIG with high dynamics and low ripples. Given that, the proposed technique has proportional-integral (PI), selecting the proper coefficient for PI controller is significant. To overcome this problem, the grey-wolf algorithm is used to optimize the PI coefficients. The results show that the proposed method gives satisfactory performance with lower overshoots and faster dynamic response.

This paper uses the coordination between the reactive power of a solid oxide fuel cell (SOFC) and a battery to control the frequency within an islanded microgrid. By this coordination, the microgrid frequency regulation becomes faster and better during contingencies. Moreover, the energy storage capacity, which is usually required for the frequency control of islanded microgrids, has significantly been reduced. Furthermore, there will be no need to consider reserve capacity in renewable sources for frequency control. Therefore, renewable energy sources can be operated at their maximum power point. Also, this paper introduces a new frequency-reactive power control concept and a related coefficient that shows the degree of dependence of the microgrid frequency on the injected reactive power changes at each bus. This coefficient determines the priority of buses for the installation of reactive power control devices to control the frequency of the microgrid. Simulation studies have been performed in the MATLAB/Simulink environment. The results show the applicability and accuracy of the proposed coefficient and demonstrate the effectiveness of the coordinated control of reactive power between the SOFC and the battery for frequency control.

Voltage and reactive power control in distribution networks is one of the most basic tasks of a distribution network operator. This is usually controlled by on-load tap-changer (OLTC)، substation capacitors، and feeder capacitors. This paper first investigates a local voltage and reactive power control in a distribution system and then how the presence of induction machine based DG affects it. In the following a proper coordination among OLTC and capacitors to minimize losses in the distribution system، with and without DG، is formulated. The results showed that in the presence of induction generator، local control was not optimal، and sometimes operating constraints are violated. Finally three methods for controlling voltage and reactive power in the presence of induction generator to reduce losses and comply with the limitations operation during the day are proposed. Induction generator can be both fixed and variable be evaluated. Simulation studies on a distribution network of 10 bus with 70/10kV voltage has been made.

The brushless doubly fed induction generator (BDFIG) is one of the main members of doubly fed electrical generators which has come close to commercialization in recent years. This generator has some of outstanding features of squirrel cage induction generator and conventional synchronous generator, and at the same time, it requires a partially rated converter. One of the major challenges in the evolution of this generator is the problem of controlling it and the necessity of having a suitable and efficient controller to stabilize the generator in the operating speed range. Therefore, in this paper, a comprehensive vector control scheme based on nonlinear control methods is proposed. Accordingly, a reference model controller fulfills the control of rotor speed. In addition, for simultaneous control of reactive power and torque, a combined approach based on sliding mode and PI controllers are used. The simulation results show in presence of the mentioned control structure, the dynamic response of system in different conditions such as change of mechanical input power and reference speed variation is much more appropriate than when a linear controller is used.

With recent advances in power-electronics، inverter-based microgrids are gaining great attention. Droop control is one of the main methods to share the real and reactive power among distributed energy resources (DERs) in an islanded microgrids. Due to different characteristics of microgrid feeders، reactive power sharing is not fully accurate and consequently، some DERs may face overload. To address this problem، this paper presents a droop-based method using virtual impedance concept in the DER control system. The resultant voltage drop on the virtual impedance increases reactive power sharing accuracy. To adjust this virtual impedance، the local controllers of DERs exchange the required data with the microgrid management center using the low bandwidth communication links. Then، a virtual impedance? reactive power droop characteristic is proposed to calculate the value of virtual impedance. The slope of this characteristic is adaptively adjusted based on the microgrid load. To verify the effectiveness of the proposed method، various scenarios are tested on the benchmark low voltage microgrid network.