Security assessment is traditionally checked using a deterministic criterion. Based on that, the system may be considered as secured or unsecured. If an unsecured condition is detected, preventive actions are foreseen to make it secure. Recently, risk based security as More
Security assessment is traditionally checked using a deterministic criterion. Based on that, the system may be considered as secured or unsecured. If an unsecured condition is detected, preventive actions are foreseen to make it secure. Recently, risk based security assessment is used in power systems. In this paper, risk-based static and dynamic security assessment is proposed and a new transient stability index is defined. In this paper, the risk index is used as an objective function in the generation reallocation algorithm. In this algorithm, the security is maintained using the generation reallocation. The algorithm is tested on IEEE 24-bus test system and its capabilities are assessed in comparison with a traditional OPF, in which the security is maintained based on a deterministic criterion. Particle Swarm Optimization (PSO) algorithm is used as the optimization tool.
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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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