1,720,985 research outputs found
Complex-Array-Operation Newton Solver for Power Grids Simulations
Full text linkThis paper presents a robust and efficient technique for performing repeated power flow simulations of power networks. The method relies on a vector-based formulation of the power balance equations combined with a complex-array operation Newton solver. It is shown how the method is suitable for advanced simulations of power grids, such as probabilistic analyses, where a large number of scenarios have to be explored in reasonable simulation times. Applications to benchmark single phase networks as well as to unbalanced three phase grids are provided
Data-driven uncertainty analysis of distribution networks including photovoltaic generation
Full text linkThis paper investigates residential distribution networks with uncertain loads and photovoltaic distributed generation. An original probabilistic modeling of consumer demand and photovoltaic generation is presented that is based on the analysis of large set of data measurements. It is shown how photovoltaic generation is described by complex non-standard distributions that can be described only numerically. Probabilistic analysis is performed using an enhanced version of the Polynomial Chaos technique that exploits a proper set of polynomial basis functions. It is described how such functions can be generated from the numerically available data. Compared to other approximate methods for probabilistic analysis, the novel technique has the advantages of modeling accurately truly nonlinear problems and of directly providing the detailed Probability Density Function of relevant observable quantities affecting the quality of service. Compared to standard Monte Carlo method, the proposed technique introduces a simulation speedup that depends on the number of random parameters. Numerical applications to radial and weakly meshed networks are presented where the method is employed to explore overvoltage, unbalance factor and power loss, as a function of photovoltaic penetration and/or network configuration
Piece-Wise Linear (PWL) Probabilistic Analysis of Power Grid with High Penetration PV Integration
Full text linkThis paper aims at presenting a novel effective approach to probabilistic analysis of distribution power grid with high penetration of PV sources. The novel method adopts a Gaussian Mixture Model for reproducing the uncertainty of correlated PV sources along with a piece-wise-linear approximation of the voltage-power relationship established by load flow problem. The method allows the handling of scenarios with a large number of uncertain PV sources in an efficient yet accurate way. A distinctive feature of the proposed probabilistic analysis is that of directly providing, in closed-form, the joint probability distribution of the set of observable variables of interest. From such a comprehensive statistical representation, remarkable information about grid uncertainty can be deduced. This includes the probability of violating the safe operation conditions as a function of PV penetration
Linear Multistep Discretization Methods with Variable Step-Size in Nonlinear Wave Digital Structures for Virtual Analog Modeling
Full text linkA Versatile Surrogate Model of the Power Distribution Grid Described by a Large Number of Parameters
Full text linkThis paper aims to present a general-purpose Surrogate Model for the probabilistic analysis of power distribution grids with a large number of input parameters. The distinctive feature of the novel technique is the employment of the partial derivatives of output variables versus input parameters to tame the “curse of dimensionality” problem exhibited by prior surrogate model calculation techniques. The second important feature of the proposed Surrogate Model method is that it does not require any a priori assumption about the nature or statistical distribution of the input parameters. In fact, it can be applied whenever design parameters are deterministic variables as well as when they are uncertain and represented by continuous and/or discrete random variables. Relevant applications presented in the paper refer to the probabilistic analysis of the distribution grid in the presence of a large number of photovoltaic sources and electric vehicle charging stations
Vector Wave Digital Filters and Their Application to Circuits with Two-Port Elements
Full text linkWave Digital Filters (WDFs) turn circuits into networks of input-output relationships that can be computed in an explicit fashion. This is done through a linear port-wise mapping of Kirchhoff variables into pairs of incident-reflected waves introducing one scalar free parameter per port, called reference port resistance. Parameters are then used to eliminate the implicit equations relating wave variables, referred to as delay-free-loops. Unfortunately, this methodology can only be applied under strong linearity and topological conditions. This manuscript presents an extension of the WDF formalism involving a novel 'cross-port' vector definition of waves, whose reference resistance is a matrix of free parameters. This generalization greatly simplifies the WDF implementation of circuits with two-port elements, such as operational amplifiers. It allows us to derive wave-based descriptions of elements such as nullors, for which no scattering relation is available in the literature. Moreover, it enables a full adaptation of a wide class of two-port elements, thus avoiding the delay-free-loops that would otherwise form in traditional WDFs. This new formalism allows us to implement a wider range of circuits with two-port elements in a modular fashion, since the topology and the elements can be modeled independently
Passivity and its Relation to Stability in LRTI N-Ports
No full textAmong the properties of Linear Resistive Time Invariant (LRTI) N-port networks, passivity plays a crucial role. In fact, passivity has a strong relation to stability of the corresponding Linear Dynamic Time Invariant (LDTI) circuit, where a positive dynamic element, i.e. a capacitor or an inductor, is connected to each port. This relation is less intuitive than expected and requires a more formal and in depth approach than that normally found in circuit theory textbooks. Passivity is also very important to characterize AC N-ports, even if, in this case, it takes a somewhat different meaning. Passivity in AC is important in applications, especially those concerning power grids. Reciprocity of these elements will also be considered
Comparison and Analysis of Algorithms for Coordinated EV Charging to Reduce Power Grid Impact
Full text linkElectric vehicle (EV) adoption has been increasing rapidly, posing new challenges for integrating EV charging infrastructure with the existing electrical grid. Uncoordinated charging of EVs can cause transformers to overload, leading to instability and unreliability in the grid. This article introduces two smart charging coordinators for EV charging pools designed to manage EV charging while considering transformer power limits. The first strategy aims to minimize operational costs, while the second maximizes the charger flexibility. Both coordinators account for uncertainties in EV arrival time and state of charge, as well as inflexible demands on transformers. The strategies are evaluated and compared using grid-aware and grid-unaware methods regarding transformer power limits. Real-world datasets are utilized to assess the performance of the proposed strategies through simulation studies across three scenarios: single charging station behavior, average parking lot occupancy, and worst-case occupancy scenarios. Comparative analysis against uncoordinated and coordinated strategies from the literature reveals that the flexibility maximization strategy provides the most uniform response, effectively mitigating transformer overload events by optimizing charging power and scheduling flexibility. The study underscores the importance of accurate, innovative charging strategies for seamless EV integration and emphasizes the necessity of coordinated charging pools for reliable EV charging operations
Statistical analysis of PV penetration impact on residential distribution grids
Full text linkThis paper presents a comprehensive approach to the probabilistic analysis of residential distribution grid injected by distributed PV sources. The approach is data-driven and is able to deal with the general scenario that includes the uncertainty of correlated PV sources and of statistically independent consumer loads. The novel method adopts a Gaussian-Mixture-Model for correctly representing PV sources correlation and a fresh probabilistic analysis technique employing Multi-Expansion polynomial chaos. Numerical experiments carried out on the Non-Synthetic European low voltage test system, highlight the importance of the comprehensive modeling strategy in order to realistically quantify uncertainty impact on the grid
Advanced probabilistic load flow methodology for voltage unbalance assessment in PV penetrated distribution grids
Full text linkThe balancing of three-phase node voltages in modern power distribution grids can be significantly deteriorated by the penetration of single-phase PV renewable sources. For a given grid topology and prescribed loads, voltage unbalance critically depends on the nodes where power is injected. Its amount can vary substantially at different observations Buses in the grid. In this paper, we present a methodology that can inform network operators about the critical Buses in the grid and critical injection scenarios. The method is based on a numerically efficient but accurate probabilistic load flow that can handle the case of many PV sources and provides detailed information on the probability distribution of voltage unbalance. The proposed methodology relies on the complex-domain modeling of voltage unbalance sensitivity and on accelerating Monte Carlo simulations via parameter space partitioning
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