Inductively coupled modular battery system for electric vehicles
01 Mar 2016-Iet Power Electronics (The Institution of Engineering and Technology)-Vol. 9, Iss: 3, pp 600-609
TL;DR: Results convincingly indicate that the proposed systems improve the vehicle's availability under fault condition and aid in overcoming the limitations such as unavailability of electric vehicle (EV) due to battery pack fault and lengthy battery recharging time.
Abstract: This study proposes two novel modularised battery systems capable of controlling the power of each module independently, and with inductive interface for convenient battery swapping. The proposed systems aid in overcoming the limitations such as unavailability of electric vehicle (EV) due to battery pack fault and lengthy battery recharging time which largely hampers the adoption of EVs for personal transportation. The proposed systems consist of a plurality of battery modules which are wirelessly coupled to the EV through inductive power transfer technology. The proposed systems are described in detail, and models are presented to analyse their steady-state behaviours. A design guideline for a 24 kWh 80 kW battery micro-pack system is discussed. Performances of the proposed topologies are investigated using simulations. To demonstrate the applicability, prototype systems of 1.5 kW are implemented and tested under various operating conditions. Results convincingly indicate that the proposed systems improve the vehicle's availability under fault condition.
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TL;DR: This article analyzes the requirements for load balancing of a new transformer-less grid-interface topology for large-scale electric vehicle (EV) charging infrastructures by controlling the internal circulating currents of the proposed topology when supplying unevenly distributed loads.
Abstract: This article analyzes the requirements for load balancing of a new transformer-less grid-interface topology for large-scale electric vehicle (EV) charging infrastructures. The proposed configuration utilizes a modular multilevel converter (MMC) to supply wireless EV chargers from each module. The inherent galvanic isolation provided by wireless inductive power transfer and the scalability of the MMC topology enable transformer-less connection to medium voltage (MV) distribution grids. This can reduce the footprint and copper volume of the internal power distribution for the parking infrastructure. The load distribution within the MMC topology depends on the location and power requirements of each EV to be charged. Requirements for load balancing by controlling the internal circulating currents of the proposed topology when supplying unevenly distributed loads are derived. It is also demonstrated how a second harmonic component of the circulating currents can be utilized to ensure balancing capability within each MMC arm, and how its required amplitude depends on the load distribution. The theoretical analysis and the performance of a corresponding control strategy are first verified by time-domain simulations of a large-scale infrastructure. Experimental results from a small-scale prototype based on an MMC where each arm has 12 modules with individual controllable loads are presented.
23 citations
TL;DR: In this article, a phase-controlled inverter is used as the power amplifier to regulate the charging power through adjusting the phase shift angle among phases with a constant operating frequency, which alleviates the EMI filter design.
Abstract: Class-D full bridge is the most common inverter topology at the primary side for wireless electric vehicles (EVs) charging systems. This study takes a novel topology of a phase-controlled inverter as the power amplifier and puts it in a context of the whole charging system. The proposed inverter topology regulates the charging power through adjusting the phase-shift angle among phases with a constant operating frequency, which alleviates the EMI filter design. For various wireless EVs chargers, the gaps between the primary side and the secondary side are changing, which results in various coupling factors k
. The equivalent resistance of the EVs battery R
battery
is also changing during the charging process. Even resonant frequencies at two sides are variable because of the components tolerances and operating environments. This study presents design considerations of a wireless EVs charging system with the proposed technology under variable k
, R
battery
, and resonant frequencies. Circuit parameters are designed and the system efficiency is derived. Industrial prototype of an EV charging system is manufactured with the proposed topology at 3.0 kW. Experiments show that these design considerations can reflect the system characteristics, and the proposed system is a good candidate to be used in wireless EV battery chargers.
22 citations
TL;DR: A unique control strategy is proposed to enhance the life time of the battery in a stand-alone photovoltaic system employing energy storage devices such as battery and super capacitor to decouple the power imbalances from the charge–discharge profile of battery, thereby contributing to the improved battery life.
Abstract: This study proposes a unique control strategy to enhance the life time of the battery in a stand-alone photovoltaic (PV) system employing energy storage devices such as battery and super capacitor. The intermittent fluctuations in PV power and load power affect the DC bus voltage leading to a random and frequent charging/discharging profile of the battery since the controlling converters are operated as constant voltage sources. To overcome this drawback, the supercapacitor converter is commanded as a constant voltage source so as to adapt to varying load conditions and the battery converter is commanded as a constant current source. This strategy helps to decouple the power imbalances from the charge–discharge profile of battery, thereby contributing to the improved battery life. The detailed experimental results are presented. Further, the proposed control strategy is tested and validated under various scenarios.
19 citations
26 Mar 2017
TL;DR: In this article, an online method of measuring battery AC impedance spectrum is presented by adding a square wave perturbation to the steady-state value of the duty cycle of a boost power converter.
Abstract: An online method of measuring battery AC impedance spectrum is presented in this paper By adding a square wave perturbation to the steady-state value of the duty cycle of a boost power converter, AC impendence values can be devised from the responses of the battery voltage and current at the odd harmonics of the perturbation frequency FFT analysis is applied to battery voltage and current to obtain the harmonic components, then the harmonic components of battery voltage and current can be used to calculate the battery AC impedance at these odd harmonics of perturbation frequency The battery AC impedance measurement method of this paper allows for the measurement of battery impedance at several different frequencies in one single perturbation period An experimental laboratory prototype is constructed to verify and validate the proposed online battery AC impedance spectrum measurement method
18 citations
Cites background from "Inductively coupled modular battery..."
...Batteries and battery systems are important energy storage devices used in several applications [1-5]....
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TL;DR: Experimental results prove the feasibility of the extended efficiency control method, which can be used in wireless powered devices in a smart grid or other extremely loosely coupled WPT systems.
Abstract: This study presents an extended efficiency control method with resonant frequency tracking, load optimisation and output voltage regulation of extremely loosely coupled wireless power transfer (WPT) systems for smart grid applications. Adaptive resonant frequency tracking of this specified system is proposed and implemented to achieve a robust and efficient transmission efficiency with fast searching and less fluctuation. Automatic load optimisation of the system with the required output is realised to further improve the efficiency by adjusting the phase-shift angle of the converter on the transmitter side. Owing to a receiving feedback circuit, the proposed system does not require any communication which is suited for operating under high-voltage insulation conditions. Input current from source is the only parameter to be sensed for the proposed strategy of extended efficiency control, which makes the method cost-effective and work-robust even in the harsh environments. Experimental results prove the feasibility of the extended efficiency control method, which can be used in wireless powered devices in a smart grid or other extremely loosely coupled WPT systems.
14 citations
References
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TL;DR: In this article, the authors proposed a coordinated charging strategy to minimize the power losses and to maximize the main grid load factor of the plug-in hybrid electric vehicles (PHEVs).
Abstract: Alternative vehicles, such as plug-in hybrid electric vehicles, are becoming more popular The batteries of these plug-in hybrid electric vehicles are to be charged at home from a standard outlet or on a corporate car park These extra electrical loads have an impact on the distribution grid which is analyzed in terms of power losses and voltage deviations Without coordination of the charging, the vehicles are charged instantaneously when they are plugged in or after a fixed start delay This uncoordinated power consumption on a local scale can lead to grid problems Therefore, coordinated charging is proposed to minimize the power losses and to maximize the main grid load factor The optimal charging profile of the plug-in hybrid electric vehicles is computed by minimizing the power losses As the exact forecasting of household loads is not possible, stochastic programming is introduced Two main techniques are analyzed: quadratic and dynamic programming
2,601 citations
TL;DR: In this paper, the authors present the current status and implementation of battery chargers, charging power levels, and infrastructure for plug-in electric vehicles and hybrid vehicles and classify them into off-board and on-board types with unidirectional or bidirectional power flow.
Abstract: This paper reviews the current status and implementation of battery chargers, charging power levels, and infrastructure for plug-in electric vehicles and hybrids. Charger systems are categorized into off-board and on-board types with unidirectional or bidirectional power flow. Unidirectional charging limits hardware requirements and simplifies interconnection issues. Bidirectional charging supports battery energy injection back to the grid. Typical on-board chargers restrict power because of weight, space, and cost constraints. They can be integrated with the electric drive to avoid these problems. The availability of charging infrastructure reduces on-board energy storage requirements and costs. On-board charger systems can be conductive or inductive. An off-board charger can be designed for high charging rates and is less constrained by size and weight. Level 1 (convenience), Level 2 (primary), and Level 3 (fast) power levels are discussed. Future aspects such as roadbed charging are presented. Various power level chargers and infrastructure configurations are presented, compared, and evaluated based on amount of power, charging time and location, cost, equipment, and other factors.
2,327 citations
TL;DR: In this article, 3-D finite-element analysis modeling is used to optimize circular power pads for electric vehicles to transfer 2-5 kW with a large air gap and have good tolerance to misalignment.
Abstract: A solution that enables safe, efficient, and convenient overnight recharging of electric vehicles is needed. Inductive power transfer (IPT) is capable of meeting these needs, however, the main limiting factor is the performance of the magnetic structures (termed power pads) that help transfer power efficiently. These should transfer 2-5 kW with a large air gap and have good tolerance to misalignment. Durability, low weight, and cost efficiency are also critical. 3-D finite-element analysis modeling is used to optimize circular power pads. This technique is viable, since measured and simulated results differ by 10% at most. A sample of power pads was considered in this work, and key design parameters were investigated to determine their influence on coupled power and operation. A final 2 kW 700-mm-diameter pad was constructed and tested having a horizontal radial tolerance of 130 mm (equivalent to a circular charging zone of diameter 260 mm) with a 200 mm air gap. The leakage magnetic flux of a charging system was investigated via simulation and measurement. The proposed pads meet human exposure regulations with measurement techniques specific by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) which uses the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines as a foundation.
822 citations
TL;DR: Results indicate that the proposed bidirectional IPT system is an ideal power interface for efficient and contactless integration of multiple hybrid or EVs into typical power networks.
Abstract: Demand for supplying contactless or wireless power for various applications, ranging from low-power biomedical implants to high-power battery charging systems, is on the rise. Inductive power transfer (IPT) is a well recognized technique through which power can be transferred from one system to another with no physical contacts. This paper presents a novel bidirectional IPT system, which is particularly suitable for applications such as plug-in electric vehicles (EVs) and vehicle-to-grid (V2G) systems, where two-way power transfer is advantageous. The proposed IPT system facilitates simultaneous and controlled charging or discharging of multiple EVs through loose magnetic coupling and without any physical connections. A mathematical model is presented to show that both the amount and direction of power flow between EVs or multiple systems can be controlled through either phase or/and magnitude modulation of voltages generated by converters of each system. The validity of the concept is verified by theoretical analysis, simulations, and experimental results of a 1.5-kW prototype bidirectional IPT system with a 4-cm air gap. Results indicate that the proposed system is an ideal power interface for efficient and contactless integration of multiple hybrid or EVs into typical power networks.
651 citations
TL;DR: In this paper, a new inductive power transfer system with a narrow rail width, a small pickup size, and a large air gap for online electric vehicles is proposed, allowing them to drive freely on specially implemented roads by obtaining power from the buried power supply rail.
Abstract: A new inductive power transfer system with a narrow rail width, a small pickup size, and a large air gap for online electric vehicles is proposed in this paper. By introducing a new core structure, the orientation of the magnetic flux alternates along with the road; hence, an inductive power transfer system with a narrow rail width of 10 cm, a large air gap of 20 cm, and a large lateral displacement about 24 cm was implemented. The resonant circuit of the inductive power transfer system, driven by a current source, was fully characterized. The experimental results showed that the maximum output power was 35 kW and that the maximum efficiency was 74% at 27 kW. The proposed system was found to be adequate for electric vehicles, allowing them to drive freely on specially implemented roads by obtaining power from the buried power supply rail.
581 citations