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Abstract-This paper presents three new contributions to power flow analysis of unbalanced three-phase distribution systems. First, a complex vector based model in αβ0 stationary reference frame is developed to state the power flow equations using a compact matrix formulation. The proposed model is based on Kirchhoff' s current law (KCL) and Kirchhoff' s voltage law (KVL). Then, a general and exact power transformer model in the αβ0 reference frame is proposed. Finally, this transformer model is incorporated into the power flow problem. It will be shown that the use of an orthogonal reference frame simplifies the modeling of the distribution network components. In this work, both the network and the power transformer, as well as PQ type loads, PQ and PV type generators and a slack bus are modeled. By using the node incidence matrix instead of the admittance matrix, the information about the grid topology and the grid parameters (including power transformers) is separately organized. As it will be demonstrated, the proposed formulation is ready to incorporate other complex models of loads, generators or storage devices. The model is tested by using the IEEE 4 and the IEEE 123 Node Test Feeders with different transformer connections and balanced and unbalanced lines and loads.

Abstract-In a smart micro-grid (MG) each generator or load has to take part into the network management, joining in reactive power supply/voltage control, active power supply/frequency control, fault ride-through capability and power quality control. The present paper includes a new concept for building integration in MGs with zero grid-impact so improving the MG efficiency. These aims are shown to be achievable with an intelligent system, based on a DC/AC converter connected to the building Point of Coupling (PC) with the main grid. This system can provide active and reactive power services also including a DC link where storage, generation and loads can be installed. The system employed for validation is a prototype available at ENEA labs (Italian National Agency for New Technologies). A complete and versatile model in MATLAB/SIMULINK is also presented. The simulations results and the experimental test validation are included. The trial confirms the model goodness and the system usefulness in MG applications.

This paper presents two innovative contributions related to the combined AC/DC power flow in railway power supply systems (RPSS). First, most of the power flow equations (the linear ones) are expressed in a compact matrix form by using graph theory based protocol. Such approach simplifies the statement of the unified power flow problem and allows the train motion to be modeled without varying the system topology. Second, the problem is formulated as an Optimization Problem (OP) instead of using the non-constrained power flow approach. This technique allows the authors to simulate the effect of trains regenerative braking, considering system constraints such us the catenary voltage limit, which determines the amount of available regenerated energy injected to the network, and burned through the resistors.

This paper presents a detailed model of a DC train to be applied to an unified AC/DC power flow analysis. The model will consider the regenerative braking of the train and the squeezing control that derives part or all regenerated power to the rheostatic braking system depending on the catenary voltage. The model also considers an on board accumulator (ACR) that can be charged with the regenerated power, depending on the network and train parameters. When the train is in traction mode, both the network and the ACR can contribute in feeding the train traction system. 2 In the present work, the authors develop a train model to be combined with the previous mentioned power flow approach. The proposed model combines the regenerative braking with an on-board accumulator, the so-called (ACR) developed by CAF Company. ACR is a Spanish acronym that stands for to Acumulador de Carga Rapida (Fast Charge Acummulator). The train can work under two different modes. The first one is the traction mode. In this mode, the required power can be provided by the catenary or the ACR depending on the ACR charge level, the amount of power demanded by the train and the catenary voltage. The second one is the braking mode, in which the power can be injected in the catenary, used to charge the ACR or burned in the rheostatic braking system depending on the operating variables. The squeezing control is also simulated when the catenary voltage exceeds a given value. Thus, part of the power is derived to the rheostatic system, and over a given catenary voltage value, no power can be injected in the catenary and all regenerated power must be burned. the developed model is a general parametric model that could be used with most of the accumulation technologies.The authors must remark that this model was developed for power flow purposes, that is why the model do not include any derivative term considering the train dynamics or the electrical network dynamics. A more accurate formulation considering such dynamic behaviour will make the formulation much more difficult and it wont add more information or accuracy when calculating the power flow solution. The authors run a steady state simulations at each simulation instant neglecting the transients between successive instants as it was proposed in [8]. This approach, known as stationary equivalent method for moving loads, is widely accepted among the authors, not only for modelling DC traction networks, but also for modelling AC traction networks for high speed trains [2][3][4][5][9][10][11][12][13][14]. This method assumes that the speed of the trains is not very high to induce pronounced electrical transients and the dc traction network slowly moves from one state to another as the locations and the input power of the trains vary. For this reason, steady state problems are solved at each instant, neglecting the electrical transients and the dynamic of the components. It is true that this is a simplification of the reality, and a differential model solved for transient purposes would be more acc...

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This paper intends to give a common modeling framework for power flow calculations in power systems with embedded FACTS devices. The proposed method uses the node incidence matrix (Γ) to avoid the problems derived from the widely used admittance matrix. The proposed approach is formulated so that the system of differential equations which are the core of the power flow problem, will be kept invariant regardless of the number of embedded FACTS or their location.

Self-supply consists on turning the electrical consumers in prosumers; they produce a part or all the energy that they consume. In Spain, the regulatory frame that affects these kind of facilities has not been published yet. This regulatory gap causes different law interpretations that lead to misunderstandings between prosumers and electrical companies. This paper tries to explain in an objective way the present regulation as well as all royal decree drafts related to self-supply developed until now. Two cases of study will be analyzed to evaluate how the regulation will affect to the taxes that the consumers must pay.