A Novel RC-Based Architecture for Cell Equalization in Electric Vehicles

Nowadays, research on electric vehicles is increasing because they have the potential to decrease greenhouse-gas emissions dramatically in the transport sector. For these types of vehicles, the battery is one of the main components. The traction system needs a cell series connection to fulfill the energy requirements. Nevertheless, batteries differ from each other due to a normal dispersion in their capacity, internal resistance, and self-discharge rate. This paper presents a novel battery equalizer circuit using an RC-based topology to equalize two adjacent cells of a battery pack. It has the advantage of merging a resistor-based equalizer, a capacitor-based equalizer, and an RC-based equalizer in one circuit. In this way, it is possible to limit the current stress in the components of the circuit. The proposed method increases the equalization time by 35% for a threshold current of 4 A. However, it is possible design the system for another threshold current. Finally, the complexity of the controller is not compromised in the proposed architecture. The operation, analysis, and design of the architecture are presented and compared to the classic schemes. The theoretical analysis is validated through simulation results. Document type: Articl

An Improved Battery Equalizer with Reduced Number of Components Applied to Electric Vehicles

The investigation of electric vehicle technologies has increased significantly in the last few years. These vehicles can substantially reduce the environmental impact of the transportation sector. In electric cars, the battery is a crucial element. The batteries are made up of several stacked cells to meet the requirements of the propulsion system. Battery equalizer circuits take active measures to ensure that a particular variable is kept inside an allowable range in all cells. Inductor-based equalizers are very popular since the equalization current is controlled. This paper proposes a single-inductor architecture with a reduced number of components. The proposed topology can transfer energy from adjacent cell-to-cell or adjacent string-to-string. This paper analyzes the operation of the converter, its design, and the design of the controller. Furthermore, a comparison of the proposed equalizer with other inductor-based schemes was made considering the component count, stress on devices, equalization time, driver complexity, and other parameters. The theoretical efficiency of the proposed equalizer obtained was 84.9%, which is competitive with other literature solutions. The impact of battery size on the number of circuit components was also analyzed. Finally, simulation results in open load and changes of current through the battery conditions were performed to validate the theoretical analysis

An Improved Battery Equalizer with Reduced Number of Components Applied to Electric Vehicles

The investigation of electric vehicle technologies has increased significantly in the last few years. These vehicles can substantially reduce the environmental impact of the transportation sector. In electric cars, the battery is a crucial element. The batteries are made up of several stacked cells to meet the requirements of the propulsion system. Battery equalizer circuits take active measures to ensure that a particular variable is kept inside an allowable range in all cells. Inductor-based equalizers are very popular since the equalization current is controlled. This paper proposes a single-inductor architecture with a reduced number of components. The proposed topology can transfer energy from adjacent cell-to-cell or adjacent string-to-string. This paper analyzes the operation of the converter, its design, and the design of the controller. Furthermore, a comparison of the proposed equalizer with other inductor-based schemes was made considering the component count, stress on devices, equalization time, driver complexity, and other parameters. The theoretical efficiency of the proposed equalizer obtained was 84.9%, which is competitive with other literature solutions. The impact of battery size on the number of circuit components was also analyzed. Finally, simulation results in open load and changes of current through the battery conditions were performed to validate the theoretical analysis

Leakage Current Reduction in Single-Phase Grid-Connected Inverters—A Review

The rise in renewable energy has increased the use of DC/AC converters, which transform the direct current to alternating current. These devices, generally called inverters, are mainly used as an interface between clean energy and the grid. It is estimated that 21% of the global electricity generation capacity from renewable sources is supplied by photovoltaic systems. In these systems, a transformer to ensure grid isolation is used. Nevertheless, the transformer makes the system expensive, heavy, bulky and reduces its efficiency. Therefore, transformerless schemes are used to eliminate the mentioned disadvantages. One of the main drawbacks of transformerless topologies is the presence of a leakage current between the physical earth of the grid and the parasitic capacitances of the photovoltaic module terminals. The leakage current depends on the value of the parasitic capacitances of the panel and the common-mode voltage. At the same time, the common-mode voltage depends on the modulation strategy used. Therefore, by the manipulation of the modulation technique, is accomplished a decrease in the leakage current. However, the connection standards for photovoltaic inverters establish a maximum total harmonic distortion of 5%. In this paper an analysis of the common-mode voltage and its influence on the value of the leakage current is described. The main topologies and strategies used to reduce the leakage current in transformerless schemes are summarized, highlighting advantages and disadvantages and establishing points of comparison with similar topologies. A comparative table with the most important aspects of each converter is shown based on number of components, modes of operation, type of modulation strategy used, and the leakage current value obtained. It is important to mention that analyzed topologies present a variation of the leakage current between 0 to 180 mA. Finally, the trends, problems, and researches on transformerless grid-connected PV systems are discussed

Modeling and Control of a Phase-Shifted Full-Bridge Converter for a LiFePO4 Battery Charger

A proper charge in an electric vehicle (EV) battery allows it to have a longer useful life and lower maintenance costs. For this purpose, the voltage and current supplied to the battery must be precisely regulated. In this article, the model of a phase-shifted full-bridge (PSFB) converter is obtained. Moreover, a dual control loop was designed to regulate the state of charge of a lithium ferrofosfate (LiFePO4) battery. The autoregressive exogenous (ARX) model is used to model the system. Once the plant model is obtained, it is controlled using a classical controller. A couple of cases are evaluated where the control parameters are modified, and the best approach is selected. From the obtained model, the controller is designed for the proposed cases. The theoretical controller response is compared with the experimental response. The results show a 94% accuracy of the model. In the same way, the result obtained from the controller is accurate in a 96% by comparing it with a simulation. Both the modeling and the control obtained experimentally resemble the results obtained theoretically. The controller manages to respond as expected in all proposed cases

A Critical Comparison of the Cuk and the Sheppard–Taylor Converter

The use of and interest in renewable energy have increased in recent years due to the environmental impact of the technologies currently used to generate electricity. Switched converters play a fundamental role in renewable energy systems. The main goal is to manipulate the output signal of the renewable energy source to meet the requirements of different loads. Therefore, the increase in research on renewable energy sources has resulted in an increase in studies on switched converters. However, many DC–DC converters can be used in a particular application, and there is no clear guidance on which converter to use. The choice of whether to use one converter over another is highly reliant on the expertise of the researcher. Two examples of DC–DC converters are the Sheppard–Taylor converter and the Cuk converter. In this work, a critical comparison is made between these converters. The parameters considered in this comparison are the number of components, gain, stress on parts, and others. The simulation results were obtained to evaluate the performance of the converters in different scenarios. Finally, we conclude that the only application for which the use of the Sheppard–Taylor converter is justified are those that require high specific power and power density

A Novel Integrated Topology to Interface Electric Vehicles and Renewable Energies with the Grid

Electric Vehicles (EVs) are an alternative to internal combustion engine cars to reduce the environmental impact of transportation. It is common to use several power sources to achieve the requirements of the electric motor. A proper power converter and an accurate control strategy need to be utilized to take advantage of the characteristics of every source. In this paper is presented a novel topology of a multiple-input bidirectional DC-DC power converter to interface two or more sources of energy with different voltage levels. Furthermore, it can be used as a buck or a boost in any of the possible conversion of energy. It is also possible to independently control the extracted power in each source and any combination of the elements of the system can be used as source and destiny for a transfer. Finally, the interaction with the grid is possible. The operation, analysis and design of the converter are presented with different modes of power transfer. Simulation results are shown where the theoretical analysis of the converter is validated