Transient stability analysis (TSA) is one of the important issues in the power system operation. The common methods of TSA are typically based on offline simulations so that some preventive and corrective actions may be designed to be adopted in real time conditions. To More
Transient stability analysis (TSA) is one of the important issues in the power system operation. The common methods of TSA are typically based on offline simulations so that some preventive and corrective actions may be designed to be adopted in real time conditions. To reduce the risk of these actions, in this paper a new method of transient stability estimation is proposed in which both local and wide-area measurements are used. According to the proposed method, the coherent generator groups of the two-area power system are initially identified and then the system is simplified based on the single machine equivalent (SIME) method. Thereafter, the equal area (EA) criterion is used to estimate the system transient stability. The innovation of this paper is the calculation of the acceleration area of SIME system based on the acceleration areas calculated locally in generator buses. The proposed method is applied on a10-mchine 39-bus test system and its results are presented by further explanation of its technical advantages.
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Stability challenges in Microgrids (MGs) usually arise from low inertia of Distributed Generation (DG). In this paper, a voltage stability improvement method is proposed in order to improve MG operation. Voltage Stability Index (VSI) is applied to evaluate and improve v More
Stability challenges in Microgrids (MGs) usually arise from low inertia of Distributed Generation (DG). In this paper, a voltage stability improvement method is proposed in order to improve MG operation. Voltage Stability Index (VSI) is applied to evaluate and improve voltage stability of MGs including different types of DGs. A new hybrid optimization is introduced to find the optimal operation of autonomous MG and to improve VSI. Operational optimization is performed by finding optimal droop parameters of DGs and sitting wind DGs to reduce energy generation cost. Optimization is defined as a multi-objective function and a hybrid HS-GA algorithm is applied to solve the optimization problem. A new power flow formulation is also proposed in which the steady state frequency, reference frequency, droop coefficients and, reference voltage of droop based DGs are considered as optimization variables. Results of proposed approach are compared with other methods for 33 and 69-bus IEEE systems using MATLAB software. Results prove the efficiency of proposed approach for operational improvement of MGs.
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With the rise in the penetration of inverter based distributed energy sources, grid codes say that converters should not be disconnected during the fault. These sources should also help the grid by reactive power injection. Power system grids are resistive inductive and More
With the rise in the penetration of inverter based distributed energy sources, grid codes say that converters should not be disconnected during the fault. These sources should also help the grid by reactive power injection. Power system grids are resistive inductive and the converter may be unstable during the fault. Converters use phase locked loop (PLL) to synchronize with the grid. PLL is not able to be stable during severe voltage drop, so converters cannot ride through the fault and should be disconnected. In this paper a novel method based on virtual impedance is proposed to maintain the synchronization during severe voltage drop. This method needs grid impedance estimation and virtually connects the converter to a point that has a stronger connection. By this novel method, during voltage drop, the converter stays connected to the grid and injects reactive power. Simulation results in MATLAB verify the ability of proposed method in improving the transient stability of converter.
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