Energy storage may improve power management in microgrids that include renewable energy sources. The storage devices match energy generation to consumption, facilitating a smooth and robust energy balance within the microgrid. This paper addresses the optimal control of the microgrid's energy storage devices. Stored energy is controlled to balance power generation of renewable sources to optimize overall power consumption at the microgrid point-of-common-coupling (PCC). Recent works emphasize constraints imposed by the storage device itself, such as limited capacity and internal losses. However, these works assume flat, highly simplified network models, which overlook the physical connectivity. This work proposes an optimal power flow solution that considers the entire system: the storage device limits, voltages limits, currents limits and power limits. The power network may be arbitrarily complex, and the proposed solver obtains a globally optimal solution.

In this study a new scheme of a step-up converter with very high voltage gain is proposed. The scheme is based on a natural combination of the switched-coupled-inductor boost converter and the diode-capacitor multiplier. The study proposes a special scheme of their mutual use for attaining very high voltage gain. An important advantage of the proposed circuit is the avoidance of the current spikes through the transistor and diodes because of the leakage inductance of the coupled inductors. The scheme provides soft commutation of the switch and the diodes. The study analyses the modes of operation and obtains the basic fundamental relations in steady state; an expression for voltage stress across the switch is derived. A new method for dynamic analysis is proposed. The corresponding analytical expressions and curves of the transient behaviour are also obtained. Modelling of the proposed structure and the experimental results are in full agreement regarding the expected efficiency and correctness of the theoretical analysis. A 100 W laboratory prototype was built and verified.

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Abstract:In this paper a new real-time optimization method for reactive power distribution in microgrids is proposed. The method enables location of a globally optimal distribution of reactive power under normal operating conditions. The method exploits the typical compact structure of microgrids to obtain a solution by parts, using the dynamic programming method and Bellman equation. The proposed solution method is based on the fact that the microgrid is designed with a central feeder line to which clusters of generators and loads are connected, and is suitable for microgrids with ring topologies as well as radial ones. The optimization problem is formulated with the cluster reactive powers as free variables, and the solution space is spanned by the cluster reactive power outputs. The optimal solution is then constructed by efficiently scanning the entire solution space, by scanning every possible combination of reactive powers, by means of dynamic programming. Since every single step involves a one-dimensional problem, the complexity of the solution is only linear with the number of clusters, and as a result, a globally optimal solution may be obtained in real time. The paper includes the results of two test-case networks.

A method to extract unique features from measured waveforms of nonlinear loads is presented. These features can be used for the identification of loads connected to the grid. The method is based on the currents' physical components (CPC) electric power transport theory combined with the Z-transform (for implementation using digital signal processing (DSP). A set of admittance-based Z-transform functions that reflect the current physical components suggested by the CPC is constructed. The resulting transfer functions are shown to reflect the electric physical significance, and are used for electric load and machine identification through its electric characteristics. In this paper, the Z-transform analytic expressions are developed and extended along with their physical comprehension. Moreover, the strength of the theory over more traditional spectral analysis is explained. The method presented in this paper is demonstrated and analyzed using real-world measured waveforms (measured by power quality monitors). Index Terms-Load identification, power transfer theory, smart grid.1551-3203 worked with R&D for the Israel Air-Force (IAF), where he developed power processing topologies for avionic systems. During 1997-1999, he was a Post-Doctorate Fellow with New York Polytechnic University, Brooklyn, NY, USA. Since 2000, he has been with the Faculty of Engineering, Tel-Aviv University, where he heads the Power Electronics and Power Quality Research Group. He has authored and coauthored over 100 papers, of which over 40 are in refereed journals. His research interests include general circuit theory, switched-mode converters, power quality, special applications of power electronics (such as for alternative energy sources) powering of autonomous sensor networks, and implanted medical devices.

This paper describes three ideal topologies of switched-capacitor converters, taking into account integration considerations and multiple DC voltage ratios. First, the ideal continuous capacitor idea is described, and then a Matrix of Capacitors configuration is proposed. This configuration is based on rectangular matrices of capacitors charging and discharging in transposed configuration for achieving the input/output DC voltage ratio. The third topology is The General Transposed Series-Parallel configuration. This is a modification with a discrete number of capacitors. The configuration is based on parallel brunches of series capacitors in the charging state and series elements of parallel capacitors in the discharging state. This topology is suitable for fine tuning in the DC voltage ratios. The Matrix and the Transposed Series-Parallel topologies are compared for an input/output ratio of 1.1. In the later topology, fewer components are required for the assumed ratio. Simulation is performed for 3 elements in the Transposed Series-Parallel topology, where each element consists of two dual identical capacitors for the elimination of external large capacitors.

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