Sharif Digital Repository

The increasing application of non-linear loads in power system causes additional losses in transformers resulting in premature damage. Manufactures and users of transformers realise the importance of this phenomenon and it is vital to adopt a procedure to prevent it thereby enhancing the reliability of power system. To achieve this, the most common method is derating of transformers. This paper intends to review derating of transformers under nonsinusoidal operation, for which all available approaches are classified into four major methods including IEEE recommended, analytical, experimental and finite elements based method. For each method, the fundamental theory, significant factors... 

We present a nonlinear geometric approach to fault detection and isolation (FDI) in a grid-connected inverter system. Open-switch faults in inverter power transistors together with faults in grid voltages and source current sensors are detected and isolated in the presence of disturbance. The detection process is based on dynamic model of an inverter, including a dc-bus capacitor and an output $RL$ filter. The proposed FDI system does not rely on balanced or zero-sum conditions in the grid point and is functional under nonsinusoidal voltages and currents. © 1993-2012 IEEE  

We present a nonlinear geometric approach to fault detection and isolation (FDI) in a grid-connected inverter system. Open-switch faults in inverter power transistors together with faults in grid voltages and source current sensors are detected and isolated in the presence of disturbance. The detection process is based on dynamic model of an inverter, including a dc-bus capacitor and an output RL filter. The proposed FDI system does not rely on balanced or zero-sum conditions in the grid point and is functional under nonsinusoidal voltages and currents. IEEE  

Increase of nonlinear loads has led to the rise of harmonic currents, voltage distortion and imbalance in power systems. IEEE Std. 1459 proposes new definitions for electric power in sinusoidal, nonsinusoidal, balanced and unbalanced conditions which can be used for compensation of nonsinusoidal and unbalanced systems. Among different definitions, IEEE Std. 1459 proposes the new concept of effective apparent power and power factor which is more related to the real losses in a power system. In this paper, by expansion of definitions of IEEE Std. 1459, instantaneous forms of effective parameters are defined. Then, a new control strategy for a Shunt Active Power Filters (SAPFs) is defined based... 

We revisit the mathematical formulation of the famous Jaynes-Cummings-Paul Hamiltonian, which describes the interaction of a two-level atom with a single mode of an electromagnetic cavity reservoir. We rigorously show that under the condition of ultrastrong coupling between the atom and cavity in which the transition frequency is comparable to the coupling frequency, the bosonic field operators undergo non-sinusoidal time variations. As a result, the well-known solutions to the Jaynes-Cummings-Paul model are no longer valid, even when the rotating wave approximation is not used. We show how a correct mathematical solution could be found instead