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The aim of the paper is to define a limit performance of highly efficient battery electric quadricycles for urban mobility. The vehicle is employed for an energy efficiency competition in which urban concepts compete. A multi-physics (thermo-electro-mechanical) Tank To Wheels (TTW) model has been developed and validated. Given the information on the track route (track map and elevation) and on the throttle input command, the model computes the vehicle power demand and cruising speed. The model is validated by means of both indoor and outdoor experimental tests. The validated model is employed for the optimization of the transmission gear ratio and of the driving strategy to minimize the overall energy consumption on a given track. Design variables are related to the transmission gear ratio and to the throttle command profile. The algorithm aims to minimize the energy consumption, including constraints on the maximum current provided by the battery and on the maximum time available to complete the lap. Comparison with some common driving strategies confirmed the effectiveness of the proposed solution, with a foreseen 9% reduction of the vehicle overall energy demand. The single seater ultra-efficient electric vehicle, compared to other urban quadricycles, has a battery capacity ten times lower and a 50% longer driving range. [ABSTRACT FROM AUTHOR]

The paper addresses a real-time optimization-based reference calculation integrated with a control structure for Modular Multilevel Converters (MMC) operating under normal and constrained situations (where it has reached current and/or voltage limitations, as it may occur during system faults). Firstly, a nonlinear optimization problem has been developed in which it prioritizes to satisfy the AC grid current set-points imposed by the transmission System Operator (TSO). The constrained nonlinear optimization problem is formulated based on the steady-state model of the MMC, whereby the prioritization is achieved through distinct weights defined in the Objective Function’s (OF) terms. The resultant optimization problem, however, is highly nonlinear requiring high computation burden to be solved in real-time. To cope with this issue, this paper applies a Linear Time-Varying (LTV) approximation, which permits to represent the nonlinear dynamics of the system as constant parameters, while a Linear Time-Invariant (LTI) system is used to formulate the optimization constraints. The converter’s current references are determined in real-time by solving a constrained linearized optimization problem at each control time step, which considers the TSO’s demands, the current MMC operating point and its physical limitations. Theoretical analyses comparing the responses of the linear and nonlinear optimization problems are performed to validate the accuracy of the LTV approximation. Finally, the linearized-optimization problem is integrated with the MMC controllers, evaluated under different AC and DC network conditions and compared with conventional control strategies, where it is shown that the presented method can be potentially employed to obtain the MMC current references for distinct network scenarios. [ABSTRACT FROM AUTHOR]

Legacy distribution systems need to adapt quickly to upcoming operating scenarios. The expected growth of electromobility and distributed generation will bring forth many challenges regarding efficient operation. Additionally, the limited communication infrastructure of these networks hinders the applicability of heavily centralized control strategies. In this context, this paper proposes a distributed control scheme for photovoltaic generators. The scheme comprises a local real–time control layer for the synthesis of active and reactive power references, using traditional voltage droop control, along with affine policies to handle the uncertainty associated to solar irradiance and demand levels. The characterization and periodic adaptation of such control scheme is achieved via a global, computationally tractable robust model able to co–optimize both droop and affine policy parameters. Performance is benchmarked via extensive computational experiments against other state–of–the–art distributed and local control strategies. Results suggest the proposed scheme is able to outperform all competitive frameworks. Its performance is also evaluated as a strictly local control scheme obtaining superior voltage regulation as compared to the recommendations in the Standard IEEE 1547.8. [ABSTRACT FROM AUTHOR]

Service restoration (SR) is essential to recovering distribution systems with outages when extreme weather conditions occur. However, the occurrence of long-duration extreme weather events may cause a restored system to become susceptible to subsequent random contingencies. To address this challenge, this paper proposes a microgrid-based SR approach for recovering critical loads in wind power penetrated distribution systems incorporating the impacts from subsequent random contingencies. A hybrid stochastic-robust optimization model is developed considering both the subsequent random contingencies that may occur and the uncertainty of wind power generation. The expected load shedding is minimized by locating mobile emergency generators, dynamically adjusting microgrid (MG) topologies, and dispatching power sources. To ensure the tractability of the optimization, the original problem is reformulated and decomposed into a master problem and several robust optimization subproblems based on the column-and- constraint generation approach. In addition, the master problem, which is in the format of stochastic optimization is solved by an improved progressive hedging algorithm to accelerate optimization. The proposed method is validated on the modified IEEE distribution systems and the simulation results show the effectiveness of the proposed SR method in reducing security violation risk and reducing the computational complexity. [ABSTRACT FROM AUTHOR]

Objective: Computational modeling is increasingly used to design charging systems for implanted medical devices. The design of these systems must often satisfy conflicting requirements, such as charging speed, specific absorption rate (SAR) and coil size. Fast electromagnetic solvers are pivotal for enabling multi-criteria optimization. In this paper, we present an analytical model based on the quasi-static approximation as a fast, yet sufficiently accurate tool for optimizing inductive charging systems. Methods: The approximate model was benchmarked against full-wave simulations to validate accuracy and improvement in computation time. The coupling factor of two test coils was measured for lateral and axial displacements and the SAR was measured experimentally in a PAA phantom. Results: The approximate model takes only 11 seconds to compute a single iteration, while the full-wave model takes 5 hours to compute the same case. The maximum difference with full-wave simulations was less than 24% and the mean difference less than 2%. Adding a novel figure of merit into the multi-criterion optimization resulted in a 16% higher charging speed. The measured results of the SAR and coupling factor are within a 5 mm coil offset margin. Conclusion: The proposed approximate model succeeds as a rapid prototyping tool, enabling fast and sufficiently accurate optimization for wireless charging systems. Significance: The approximate model is the first of its kind to compute both the coupling factor and the SAR near conducting structures fast enough to enable optimization of charging speed. [ABSTRACT FROM AUTHOR]

The advancements in machine learning (ML) opened a new opportunity to bring intelligence to the low-end Internet-of-Things (IoT) nodes, such as microcontrollers. Conventional ML deployment has high memory and computes footprint hindering their direct deployment on ultraresource-constrained microcontrollers. This article highlights the unique requirements of enabling onboard ML for microcontroller-class devices. Researchers use a specialized model development workflow for resource-limited applications to ensure that the compute and latency budget is within the device limits while still maintaining the desired performance. We characterize a closed-loop widely applicable workflow of ML model development for microcontroller-class devices and show that several classes of applications adopt a specific instance of it. We present both qualitative and numerical insights into different stages of model development by showcasing several use cases. Finally, we identify the open research challenges and unsolved questions demanding careful considerations moving forward. [ABSTRACT FROM AUTHOR]

A linear and convex model has been recently presented for the operation of battery energy storage units that does not explicitly prevent their simultaneous charge and discharge in the problem formulation. This letter claims that the model in such a literature contribution is capable of ensuring the physical realizability of the battery dispatch only when nondiscrete decisions are considered in the optimization problem. This claim is demonstrated through the solution of two instances of a simple unit-commitment-based example comprising two generating units, one battery energy storage unit, and two time periods. [ABSTRACT FROM AUTHOR]

Handling nonlinear constraints in continuous optimization is challenging, and finding a feasible solution is usually a difficult task. In the past few decades, various techniques have been developed to deal with linear and nonlinear constraints. However, reaching feasible solutions has been a challenging task for most of these methods. In this article, we adopt the framework of estimation of distribution algorithms (EDAs) and propose a new algorithm (EDA++) equipped with some mechanisms to deal with nonlinear constraints. These mechanisms are associated with different stages of the EDA, including seeding, learning, and mapping. It is shown that, besides increasing the quality of the solutions in terms of objective values, the feasibility of the final solutions is guaranteed if an initial population of feasible solutions is seeded to the algorithm. The EDA with the proposed mechanisms is applied to two suites of benchmark problems for constrained continuous optimization and its performance is compared with some state-of-the-art algorithms and constraint-handling methods. Conducted experiments confirm the speed, robustness, and efficiency of the proposed algorithm in tackling various problems with linear and nonlinear constraints. [ABSTRACT FROM AUTHOR]

Although time-variant nonlinear optimization with equality and inequality constraints (TVNOEIC) is a widespread problem in real life, the research on this issue is much less than the time-invariant one. Large lagging errors may not be inevitable if the traditional models designed for time-invariant optimizations are exploited to time-variant ones. To eliminate the lagging errors, models for handling time-variant optimization problems are urgently required. Recently, neural networks and the related neural dynamics approaches have witnessed rapid developments and made significant contributions to the online solution of various problems. On this basis, a noise-suppressing discrete-time neural dynamics (NSDTND) model is proposed in this article for solving the TVNOEIC problem. Theoretical analysis is presented to prove that the residual error of the proposed model is tiny enough to estimate the actual solution even in the presence of noise perturbation. In addition, numerical simulations, including an application on winner-take-all operation, are provided to further demonstrate the effectiveness and robustness of the proposed NSDTND model. [ABSTRACT FROM AUTHOR]

A local constrained multiobjective Bayesian optimization (LoCoMOBO) method is introduced to address automatic sizing and tradeoff exploration for analog and RF integrated circuits (ICs). LoCoMOBO applies to constrained optimization problems utilizing multiple Gaussian process (GP) models that approximate the objective and constraint functions locally in the search space. It searches for potential pareto optimal solutions within trust regions of the search space using only a few time-consuming simulations. The trust regions are adaptively updated during the optimization process based on feasibility and hypervolume metrics. In contrast to mainstream Bayesian optimization approaches, LoCoMOBO uses a new acquisition function that can provide multiple query points, therefore allowing for parallel execution of costly simulations. GP inference is also enhanced by using GPU acceleration in order to handle highly constrained problems that require large sample budgets. Combined with a framework for schematic parametrization and simulator calls, LoCoMOBO provides improved performance tradeoffs and sizing results on three real-world circuit examples, while reducing the total runtime up to $\times 43$ times compared to state-of-the-art methods. [ABSTRACT FROM AUTHOR]

In cyber-physical power systems (CPPSs), false data injection attack (FDIA) has drawn much attention due to its stealthiness. It is of great importance to investigate the potential behaviors of attackers to improve the cyber-security of CPPSs. However, most FDIA models are often constructed separately on the effect of attackers or the impact of attacks. Accordingly, this brief proposes a multi-objective stealthy FDIA scheme in AC grid model. The attack model is described as a multi-objective optimization problem, where minimization of contaminated measurements and maximization of the attack impact are considered as two objectives while remaining stealthy. To deal with the established attack model, a non-dominated sorting genetic algorithm II (NSGAII) is introduced as the solver. To improve the efficiency of generating attack vector, a new representation mechanism is proposed to describe locations and values of injected states. Additionally, during the evolutionary process, we propose a mutation operation to balance the sparsity and impact of FDIA. Simulation results on the IEEE 14-bus, 30-bus, and 118-bus systems demonstrate the feasibility of the NSGAII-based FDIA model. [ABSTRACT FROM AUTHOR]

The benefit of real-time joint dynamic route guidance and signal control (DRG-SC) is usually compromised by a centralized framework since it naturally leads to an un-timely solution with the growing data-processing needs and problem-solving complexity. Mobile edge computing (MEC) pushes the data storage and computation from the remote cloud to local infrastructures and hence reduces response time and improves network bandwidth when further combined with 5G. As such, our study first develops a novel distributed framework to facilitate DRG-SC in connected vehicle (CV) environment with clarifying the MEC’s vital role. The method captures the interaction of vehicles’ routing and signal control, wherein we use a more realistic and accurate way to define the relationship between travel time and traffic volume. Vehicles make route decisions and cooperate to reach user optimal (UO) or system optimal (SO) traffic state. In tandem, the developed adaptive signal control (ASC) adjusts the signal timing plan with considering both the adjacent intersections’ traffic volume and the vehicles’ waiting time. Our method achieves significant reductions in vehicles’ average departure delay, waiting time and travel time when justified by a comprehensive case study implemented in SUMO. Moreover, the effectiveness of adopting such a distributed framework in saving computation time is verified. Overall, our study provides valuable and practical insights into the intelligent operation and control. [ABSTRACT FROM AUTHOR]

Due to the potentially severe consequences of coordinated cyber-physical attacks (CCPA), the design of defenses has gained significant attention. A popular approach is to eliminate the existence of attacks by either securing existing sensors or deploying secured PMUs. In this work, we improve this approach by lowering the defense target from eliminating attacks to preventing outages and reducing the required number of PMUs. To this end, we formulate the problem of PMU Placement for Outage Prevention (PPOP) under DC power flow model as a tri-level non-linear optimization problem and transform it into a bi-level mixed-integer linear programming (MILP) problem. Then, we propose an alternating optimization framework to solve PPOP by iteratively adding constraints, for which we develop two constraint generation algorithms. In addition, for large-scale grids, we propose a polynomial-time heuristic algorithm to obtain suboptimal solutions. Next, we extend our solution to achieve the defense goal under AC power flow model. Finally, we evaluate our algorithm on IEEE 30-bus, 57-bus, 118-bus, and 300-bus systems, which demonstrates the potential of the proposed approach in greatly reducing the required number of PMUs. [ABSTRACT FROM AUTHOR]

Max-affine regression refers to a model where the unknown regression function is modeled as a maximum of $k$ unknown affine functions for a fixed $k \geq 1$. This generalizes linear regression and (real) phase retrieval, and is closely related to convex regression. We study this problem in the high-dimensional setting assuming that $k$ is a fixed constant, and focus on the estimation of the unknown coefficients of the affine functions underlying the model. We analyze a natural alternating minimization (AM) algorithm for the non-convex least squares objective when the design is Gaussian. We show that the AM algorithm, when initialized suitably, converges with high probability and at a geometric rate to a small ball around the optimal coefficients. In order to initialize the algorithm, we propose and analyze a combination of a spectral method and a search algorithm in a low-dimensional space, which may be of independent interest. The final rate that we obtain is near-parametric and minimax optimal (up to a polylogarithmic factor) as a function of the dimension, sample size, and noise variance. In that sense, our approach should be viewed as a direct and implementable method of enforcing regularization to alleviate the curse of dimensionality in problems of the convex regression type. Numerical experiments illustrate the sharpness of our bounds in the various problem parameters. [ABSTRACT FROM AUTHOR]

The parameter mismatch problem has a great impact on the control performance of model predictive control, which is however unavoidable during the operation. In order to improve the system robustness against the parameter mismatches and disturbances, an improved direct model predictive current control with a disturbance observer is proposed in this article, where the disturbance observer is realized by an incremental moving horizon estimator. Moreover, another concern raised from the applications of direct model predictive current control is the computational burden, especially for the long-horizon implementations. Therefore, a dual reference frame solution for the surface permanent-magnet synchronous motor (SPMSM) is proposed in this article to allocate a great proportion of heavy computations required for the optimization problem to the offline preparation, which can reduce the computational burden by almost 50% on average for a prediction horizon of five time-steps. Besides, the parameter mismatch effects of individual electrical parameters on the control performance of the model predictive direct current control method are investigated and quantified via simulations. A five-step direct model predictive current control is implemented on a dSPACE system with a sampling frequency of 20 kHz to validate the effectiveness of the proposed scheme with an SPMSM drive system. [ABSTRACT FROM AUTHOR]