arXiv subjects

Joaquim Dias Garcia

Publications and source records attributed to Joaquim Dias Garcia.

25 records · Page 2Linked to original sources

arXiv2020

Multiscale Stochastic Simulation of the US Pacific Northwest Using Distributed Computing and Databases with Integrated Inflow and Variable Renewable Energy

Modelling challenges of the United States Pacific Northwest system have grown in the last decade. Besides classical modelling difficulties such as a complex hydro cascade with many operational constraints, we have seen higher penetration of variable renewable energy inside and outside the system leading to internal issues and completely different power exchanges with the West Coast System. The analysis of adequacy and reliability of this system motivated the design and implementation of a five-step simulator including four planning phases and an operation step. The five levels were modeled as mathematical programs that are linked from top to bottom by fixed decisions and improvements in forecasts, on the other hand they are also linked from bottom to top by system updated states. The solution of the millions of resulting mathematical programs was made possible by applying state of the art optimization techniques and high performance data bases in a massively parallel environment.

math.OC↗

arXiv2020

Application of Progressive Hedging to Var Expansion Planning Under Uncertainty

This paper describes the application of a Progressive Hedging (PH) algorithm to the least-cost var planning under uncertainty. The method PH is a scenario-based decomposition technique for solving stochastic programs, i.e., it decomposes a large scale stochastic problem into s deterministic subproblems and couples the decision from the s subproblems to form a solution for the original stochastic problem. The effectiveness and computational performance of the proposed methodology will be illustrated with var planning studies for the IEEE 24-bus system (5 operating scenarios), the 200-bus Bolivian system (1,152 operating scenarios) and the 1,600-bus Colombian system (180 scenarios).

math.OC↗

arXiv2020

Modeling Multiscale Variable Renewable Energy and Inflow Scenarios in Very Large Regions with Nonparametric Bayesian Networks

In this paper, we propose a non-parametric Bayesian network method to generate synthetic scenarios of hourly generation for variable renewable energy(VRE) plants. The methodology consists of a non-parametric estimation of the probability distribution of VRE generation, followed by an inverse probability integral transform, in order to obtain normally distributed variables of VRE generation. Then, we build a Bayesian network based on the evaluation of the spatial correlation between variables (VRE generation and hydro inflows, but load forecast, temperature, and other types of random variables could also be used with the proposed framework), to generate future synthetic scenarios while keeping the historical spatial correlation structure. Finally, we present a real-life case study, that uses real data from the Brazilian power system, to show the improvements that the present methodology allows for real-life studies.

stat.AP↗

arXiv2019

Community Detection for Power Systems Network Aggregation Considering Renewable Variability

The increasing penetration of variable renewable energy (VRE) has brought significant challenges for power systems planning and operation. These highly variable sources are typically distributed in the grid; therefore, a detailed representation of transmission bottlenecks is fundamental to approximate the impact of the transmission network on the dispatch with VRE resources. The fine grain temporal scale of short term and day-ahead dispatch, taking into account the network constraints, also mandatory for mid-term planning studies, combined with the high variability of the VRE has brought the need to represent these uncertainties in stochastic optimization models while taking into account the transmission system. These requirements impose a computational burden to solve the planning and operation models. We propose a methodology based on community detection to aggregate the network representation, capable of preserving the locational marginal price (LMP) differences in multiple VRE scenarios, and describe a real-world operational planning study. The optimal expected cost solution considering aggregated networks is compared with the full network representation. Both representations were embedded in an operation model relying on Stochastic Dual Dynamic Programming (SDDP) to deal with the random variables in a multi-stage problem.

physics.soc-ph↗

arXiv2019

Reliability-Constrained Power System Expansion Planning: A Stochastic Risk-Averse Optimization Approach

This work presents a methodology to incorporate reliability constraints in the optimal power systems expansion planning problem. Besides LOLP and EPNS, traditionally used in power systems, this work proposes the use of the risk measures VaR (Value-at-Risk) and CVaR (Conditional Value-at-Risk), widely used in financial markets. The explicit consideration of reliability constraints in the planning problem can be an extremely hard task and, in order to minimize computational effort, this work applies the Benders decomposition technique splitting the expansion planning problem into an investment problem and two sub-problems to evaluate the system's operation cost and the reliability index. The operation sub-problem is solved by Stochastic Dual Dynamic Programming (SDDP) and the reliability sub-problem by Monte Carlo simulation. The proposed methodology is applied to the real problem of optimal expansion planning of the Bolivian power system.

math.OC↗

arXiv2019

Modelling power markets with multi-stage stochastic Nash equilibria

The modelling of modern power markets requires the representation of the following main features: (i) a stochastic dynamic decision process, with uncertainties related to renewable production and fuel costs, among others; and (ii) a game-theoretic framework that represents the strategic behavior of multiple agents, for example in daily price bids. These features can be in theory represented as a stochastic dynamic programming recursion, where we have a Nash equilibrium for multiple agents. However, the resulting problem is very challenging to solve. This work presents an iterative process to solve the above problem for realistic power systems. The proposed algorithm is consist of a fixed point algorithm, in which, each step is solved via stochastic dual dynamic programming method. The application of the proposed algorithm are illustrated in case studies with the Panama systems.

math.OC↗

arXiv2016

A Low-Frequency Tone Sweep Method for in-Service Fault Location in Sub-Carrier Multiplexed Optical Fiber Networks

We demonstrate an optical fiber fault location method based on the frequency response of the modulated fiber optical backscattered signal in a steady state low-frequency step regime. Careful calibration and measurement allows for the reconstruction of the fiber transfer function, which, associated to its mathematical model, is capable of extracting the fiber characteristics. The technique is capable of identifying non-reflective fault events in an optical fiber link and is perfectly compatible with previous methods that focus on the reflective events. The fact that the recuperation of the complex signal is performed in the frequency domain and not via a Fourier Transform enables the measurements to overcome the spatial resolution limitation of Fourier Transform incoherent-OFDR measurements even with frequency sweep ranges down to 100-100000 Hz. This result is backed up by a less than 10 meters difference in fault location when compared to standard OTDR measurements.

physics.ins-det↗