The optimal power flow (OPF) problem focuses on the operational efficiency of electric power systems. Modern grids include a variety of devices that are often omitted in traditional OPF formulations, namely, different types of generators, transformers, or power electronics-based devices. The modified and augmented nodal analysis (MANA) extends the traditional nodal analysis by expressing circuit equations in a generic sparse matrix representation. The MANA approach can seamlessly accommodate constraints from various types of devices commonly encountered in modern networks. This, in turn, allows their straightforward inclusion as constraints in OPF by modelling them through MANA using their current and voltage equations. This work proposes a new OPF formulation based on MANA and the corresponding power flow constraints, which we refer to as MANA-OPF. The non-convex MANA-OPF is solved using a nonlinear solver, namely, IPOPT in Julia. The formulation is tested on several test cases. The results are compared to a standard approach used by PowerModels.

The type of carrier signal waveform plays a pivotal role in the dynamic response of the PWM-controlled DC-DC converters. To fully understand the nonlinear behavior of DC-DC converters, this paper aims to dissect the bifurcation process in a PWM-controlled buck converter under various modulations. To this end, various carrier signal waveforms, including single-edge modulation, symmetrical and asymmetrical dual-edge modulations, and various phase-shifted PWMs are considered. Next, using discrete-time modeling, the dynamic analysis of the system at various phase shifts is performed. Inspection of the bifurcation diagram and eigenvalue trajectories, obtained by shifting the gate signal within the switching period, reveals that the converter experiences period-1, period-2, and period-4 orbits within one switching period. The results of this analysis are validated through simulation studies and experiments.

One key factor in the operation of droop-controlled islanded microgrid (IMG) systems is its maximum loadability. In this paper, the effect of droop controllers on loadability of IMGs is studied. Moreover, the effect of different unbalanced conditions, droop functions, reactive droop coefficients, and also inverse droop on the IMG loadability are taken into account. The proposed model is examined on an unbalanced 38-bus and IEEE 906-bus ac IMGs. The findings substantiate that for conventional and inverse droop cases, respectively, reactive (Q-droop) and active droop functions (P-droop), due to their intentional voltage deviation, highly affect the IMG loadability.

Increased penetration level of plug-in electrical vehicles (PEVs), necessitates the need for more PEVs charging stations. However, by high penetration of charging stations, distribution power systems may have more challenges, such as high power loss and deteriorated voltage profile. So far, optimal sizing and sitting of charging stations have been utilized to improve the features of the power systems affected by charging stations. While, our studies show that distributed arrangements of charging stations can also play an important role. This role is more highlighted, when vehicle-to-grid (V2G) capability is also considered. To this aim, in this paper, considering total charging and discharging capacities of stations, a factor known as distribution factor is proposed. Then, the effect of different distribution factors, considering grid-to-vehicle (G2V) and V2G modes of PEVs, is discussed. Numerical results verify that distribution factor and hence distributed arrangements of charging stations can affect power loss and voltage profile of the host power system.

In this paper, it is shown that by increasing the number of Micro-Inverters (MIs), the performance of their harmonic compensators, may be deteriorated. Therfore, to design harmonic compensators for a large number of parallel MIs, it is not enough to consider the performance of only one MI. The analysis show that, in the design of harmonic compensators, presence of filter capacitor, can cause the MIs to have capacitive behaviors. On the other hand, by increasing the number of MIs, the probable interaction frequency between the MIs and the grid, drifts down to the lower frequency range and close to the harmonic frequencies. In this situation, the interaction among the inductive grid and the capacitive MIs, at harmonic frequencies, is inevitable. As a solution, in this paper, the modified design of harmonic compensators is proposed. A complete set of simulations is also provided to evaluate the effectiveness of the proposed analysis.