Sensitivity Analysis of a Bidirectional Wireless Charger for EV

Bidirectional chargers are required to fully integrate Electric Vehicle (EV) into the smart grids. Additionally, wireless chargers ease the charge/discharge process of the EV batteries so that they are becoming more popular to fulfill a V2G scenario. When considering the load of wireless chargers, it is a requirement to know the real output power that these systems offer. The designed output power may differ from the real one as components suffer from tolerance. This paper defines six sensitivity factors to model the severity of the effects of tolerance into the output power. To do so, an electric circuit analysis is used and a mathematical formulation is derived. The six sensitivity factors are computed for a laboratory prototype.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Capacity and Energy Local Flexibility Markets for Imbalance and Congestion Management

Local Flexibility Markets (LFMs) are a type of marketplace where flexibility products are traded to solve network issues. In the last several years, efforts were made in the field of LFM for imbalance and congestion management, but they only trade with energy products with highly complex mathematical descriptions. This paper presents a description of an efficient LFM formulation where both capacity and energy products are considered through a linear programming (LP) optimization problem to clear the LFM in a centralized manner. It is assumed that flexibility assets present in the distribution network are managed by Aggregators (Aggs). Results from this centralized approach are provided under three different scenarios, demonstrating the feasibility of the proposed approach to solve network issues at a distribution levelUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Coordinated Trading of Capacity and Balancing Products in Multi-Area Local Flexibility Markets.

In a scenario with high penetration of renewable and distributed energy resources, Local Flexibility Markets (LFMs) emerge to enhance operation of distribution networks. They deal with new consumption patterns, flexibility, and storage systems to mitigate imbalances and congestions. In recent years, efforts toward the definition of stand-alone LFMs have been made, enabling energy trading in isolated systems. This paper present an alternative solution for congestion and imbalance mitigation using capacity and balancing flexibility products. Products prices are defined considering their intrinsic relation with traditional markets, what enhances compatibility and enables full deployment of this local structures. Besides of that, using the properties of an adaptive ADMM algorithm, the market clearing problem is solved under a Multi-Area setting while information privacy is preserved. The feasibility of the proposed approach is demonstrated on a radial network based on the IEEE 34 bus system, where the solution for the two-area LFM is found in four tens iterations. Furthermore, the scalability analysis provides shows a linear relation between the number of areas and the convergence.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Evaluation of losses in a bidirectional wireless power transfer system for electric vehicles

Inductively power transfer systems are becoming increasingly popular in modern applications like electric vehicles. In order to make this technology attractive, its transfer efficiency must be considerably high. Most works in the literature define the efficiency of the wireless charger as the one associated to the inverter, the coupled coils and the compensation networks. Therefore, they usually omit the study of the losses occurring in other parts of the system such as in the secondary rectifier. This paper evaluates the losses in a complete wireless charger, built and designed to provide V2G functionalities. The experimental evaluation based on the waveform analysis is contrasted with a theoretical model, which relies on the non-idealities of the components. The evaluation reveals that measurement error greatly impact on the power losses derived by the two approachesUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Effect of Ramping Requirement and Price Cap on Energy Price in a System with High Wind Penetration

Sebastian Martin, Yves Smeers, and Jose Aguado. Effect of Ramping Requirement and Price Cap on Energy Price in a System with High Wind Penetration. In proceedings of the 22nd International Symposium on Mathematical Programming, Pittsburgh, July 12-17, 2015The European power market is currently retiring or mothballing large capacities of conventional plants, and at the same time incorporating a significant amount of non-dispatchable renewable generation, in particular wind. We analyse the mothballing process (and the resulting system) and study how they are affected by a price cap implemented in the energy only market, and by a possible implementation of ramping products in the system.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Power Factor Corrector Design applied to an 85-kHz Wireless Charger

Wireless charging technology extends the battery autonomy by allowing more flexible and practical ways of recharging it even when the electric vehicle is on move. The frequency conversion, which is required to generate a kHz-ranged magnetic field, also leads to considerable harmonics. As a result, the power factor and the corresponding efficiency decrement. This paper proposes a Power Factor Corrector which overcomes this drawback. The most relevant feature of the designed Power Factor Corrector is that it does not need any electrical signal from the secondary side to adjust its operation properly. The simulation results show the ability of the proposed scheme to increment the system efficiency for different State-Of-Charge in the Battery.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Detection of emerging faults in power transformers using self-organising maps

Power transformers are a crucial part of the power system, one of the largest infrastructures in industrialised countries. In particular, wind turbine transformers are subjected to frequent thermal cycling as a function of varying turbine loads. Thus transformers are prone to developing faults and defects that can involve high repair costs for instance due to the repeated thermal stress on the winding. Faults develop mainly when the insulation produces small leakage currents between turns, which if not detected early, might become short circuits that can result in interruptions in electricity supply, and difficult and costly repairs. An optimum overhaul of damaged transformers is not accomplished often because of lack of appropriate inspection tools. Detailed assessment and preventive maintenance work, which will allow the detection and repair of failures at early stages, is believed to be the only suitable way to cope with power transformer degradation at low cost. This paper presents a methodology based on the analysis of current signals converted by the S transform for the detection of incipient faults in transformers. The procedure is based on calculating the energy of the zones of the time-frequency spectrum. Its main advantage is its possible real time implementation that can be applied while the transformer is in use. Experimental results with PSCAD are presented.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Independent primary-side controller applied to wireless chargers for electric vehicles

Electric vehicles rely on batteries that need to be frequently recharged. As an alternative to conductive charging, wireless chargers provide a higher reliability to pollution and electric failures and they also extend the situations and places where the recharge could be available without user’s intervention (e.g. parking spaces, on-road). In order to optimize the performance of a wireless charger, its configuration should be dynamically adapted to the varying battery’s electrical features. Towards this goal, controllers are incorporated into the system to modify the behavior of some switching devices belonging to the power electronics blocks. This paper presents a controller that acts in the DC/DC structure placed in the primary side. As a novelty, the controller infers the instantaneous battery power demands by exclusively measuring voltage and current in the primary side. In this way, there is no need for communicating (via wired or wireless links) the primary and the secondary sides. The simulation results show the ability of the controller to adapt to different battery states.Universidad de Málaga. Campus de Excelencia Internacional Andalucia Tec

A Decision Tree and S-Transform Based Approach for Power Quality Disturbances Classification

In this paper, it is presented an automated classification based on S-transform as feature extraction tool and Decision Tree as algorithm classifier. The signals generated according to mathematical models, including complex disturbances, have been used to design and test this approach, where noise is added to the signals from 40dB to 20dB. Finally, several disturbances, simple and complex, have been considered to test the implemented system. Evaluation results verifying the accuracy of the proposed method are presented.IEE

Sensitivity analysis of Component's Tolerance in Inductively Coupled Power Transfer System

ICPT systems help drivers to recharge their electrical vehicles via wireless. The core of the system is a pair of coils and two reactive structures. In order to predict the performance of a practical implementation, it is necessary to study the impact of using real components which suffer from variations in their nominal values. Basing on the performed study, we conclude that the components on the side where the inductance is in series with the capacitance should be carefully selected as variations in their values greatly affect the system performance. A 50 kW system has been evaluated in terms of efficiency and load voltage.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech