1,720,984 research outputs found
Modeling, Control and Identification of a Smart Grid
Full text linkWe are in front of an epochal change in the power distribution and generation scenario. The increasing request of energy, the energy dependency of several countries from few foreign nations endowed with oilfield or gas field, and, on the other hand, the climate change and environmental issues are the main explanation of the recent development and spread of renewable distributed energy generation technologies. Examples of them
are photovoltaic panels, wind turbines or geothermal, biomass, or hydroelectric. They are called small-size generators, or micro-generator, since the amount of power they can produce is significantly lower than the one produced by the huge, classical power plants. These distributed energy resources (DERs) are located close to where electricity is used, in the distribution network. Furthermore, they are connected to the electrical grid via electronic interfaces, the inverters, that could allow us to control the power injected into the grid. This thesis is focused on the study of some crucial aspects of this new energetic
scenario:
1. Modeling: we recall the classical models and a recent linearized one of the power systems, that will be very useful for the design and the analysis of our algorithms.
2. Optimal Reactive Power Flow (OPRF) problem: in this part we recall classical and recent algorithms that deal with the reactive power regulation. In particular, we focus on the ones that solve the OPRF problem, i.e. the problem of the amount of reactive power to be injected by each micro-generators, in order
to achieve “optimal” performance. We choose, as an optimality achievement, the minimization of the line losses. Finally we derive and propose our OPRF algorithm, providing formal proves of its convergence to the optimal solution.
3. Optimal Power Flow (OPF) problem: the OPF problem’s aim is to find an operating point of the power system that optimize a cost function (tipically the generation cost) satisfying the power demand and some operative constraints. After recalling the most popular algorithms that solve the OPF problem, we propose two
of them. In this framework there are mainly two possible scenarios. The first is related to the “utility point of view”, where the total cost accounts for the production cost of the energy (that comes from big generation plants such as nuclear or hydro-electrical plants) and for the remuneration to be paid to the owners of DERs. In this framework, the utility imposes a behavior procedure to be followed by the producers to compute the amount of energy they have to inject into the grid to minimize the total cost. The first algorithm deal with this scenario. The second one is related to the “producer point of view”. Since the owners of the DERs are paid proportionally to the energy that they inject, they would like to
maximize the power they inject, while keeping satisfied some operative constraints. The result is a game among the agents. A first treatment on this scenario is given by the second algorithm.
4. Switches monitoring for topology identification: in this part, after a literature review, we propose a algorithm for the identification of switches actions. They modify the topology of the electrical grid, whose knowledge is fundamental for monitoring, control and estimation. This algorithm works analyzing how the phasorial voltage profile vary and recognize a kind of signature left by the switches status change
Local and distributed voltage control algorithms in distribution network
No full textIn this paper, we consider a voltage control problem in power distribution grids. The specific goal is that of keeping the voltages within preassigned operating limits by commanding the reactive power output of the microgenerators connected to the grid. We propose three strategies. The first two strategies are purely local, meaning that each microgenerator updates the amount of reactive power to be injected based only on local measurements of the voltages' magnitude. Instead the third one is distributed, namely, the microgenerators, to perform the updating steps, require some additional information coming from the neighboring agents. The local strategies are simpler to be implemented, but they might fail in solving the voltage control problem. Instead, the distributed one requires the microgenerators to be endowed with communication capabilities, but it is effective in driving the voltages within the admissible intervals and, additionally, it exploits the cooperation among the agents to reach also a power losses minimization objective. Theoretical analysis and extensive numerical simulations are provided to confirm the arguments aforementioned
Distributed Reactive Power Feedback Control for Voltage Regulation and Loss Minimization
No full textWe consider the problem of exploiting the microgenerators dispersed in the power distribution network in order to provide distributed reactive power compensation for power losses minimization and voltage regulation. In the proposed strategy, microgenerators are smart agents that can measure their phasorial voltage, share these data with the other agents on a cyber layer, and adjust the amount of reactive power injected into the grid, according to a feedback control law that descends from duality-based methods applied to the optimal reactive power flow problem. Convergence to the configuration of minimum losses and feasible voltages is proved analytically for both a synchronous and an asynchronous version of the algorithm, where agents update their state independently one from the other. Simulations are provided in order to illustrate the performance and the robustness of the algorithm, and the innovative feedback nature of such strategy is discussed
Partition-based multi-agent optimization in the presence of lossy and asynchronous communication
No full textA game theory framework for active power injection management with voltage boundary in smart grids
No full textAbstract — Smart grids are a novel paradigm for energy distribution, where instead of the traditional directed flow from a producer to the consumers, several micro-generators are spread throughout the network. We focus on the problem of coordinating the injection of active power into the grid by the micro-generators. Each of them aims at injecting the maximum amount of power, satisfying some operative constraints such as voltage boundaries; a tradeoff must be found among these conflicting objectives. First, we characterize the active power increment region, i.e., the set of all the increments of injected power that, depending on the grid state, satisfy the voltage boundary. Based on this finding, we frame the problem within game theory and propose a distributed approach that achieves a fair share of the active power injection, while at the same time satisfying the voltage boundary. I
A linear dynamic model for microgrid voltages in presence of distributed generation2011 IEEE First International Workshop on Smart Grid Modeling and Simulation (SGMS)
No full text
Algorithms for voltage control in distribution networks
No full textAbstract—We consider the problem of exploiting the micro-generators connected to the power distribution grid to provide distributed reactive power compensation for voltage support. We review some of the state-of-the-art control strategies, compare and analyze their performance. Furthermore, we propose a novel control strategy that, exploiting communications among neighboring micro-generators, achieves a fast voltage regulation and minimizes the losses of the grid. Simulations are provided in order to confirm the effectiveness of the novel algorithm and to compare its performance with respect to the performance of the state-of-the-art algorithms. In addition, a discussion on the fundamental role played by the communication among generators to guarantee that voltage constraints are satisfied is included. I
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