Low-voltage Battery Research Articles

Isolated DC/DC converter with three‐level high‐frequency link and bidirectional power flow ability for electric vehicles

A high-frequency isolated bidirectional DC/DC converter based on the combination of an H-bridge, a three-level half-bridge and a three-phase full bridge topology is proposed for electric vehicle applications. The 24 V low-voltage battery pack is the power supply of the converter and it is raised to about 144 V, which is then converted to three-phase AC voltage to drive the induction motor. A multilevel high-frequency link is proposed to implement the conversion from the low voltage side (LVS) to the high voltage side (HVS). The switching patterns and single-phase three-level pulse width modulation is proposed to maintain the voltage on HVS and to control the power flowing out of the battery. The zero voltage switching characteristics of the low rating-voltage metal-oxide-semiconductor field-effect transistors on LVS and HVS are analyzed. The algorithms to suppress DC bias of magnetising current and to equalise the capacitor voltages are also introduced. The effectiveness and the control strategy of the proposed converter are verified by simulation and experimental results.

Charging balance management technology for low-voltage battery in the car control unit with combined power system

The article presents the results of mathematical models and algorithms development complex, which is aimed at ensuring a positive charge balance of an automobile low-voltage rechargeable battery in car control systems with a hybrid power system. The aim of the work is to create and implement a set of software and mathematical models on one of the existing passenger car model, using the default components and systems of the car, to achieve a positive energy balance of the automotive low-voltage power network, and also to solve the problem of battery discharge by normalizing the turn-on time of powerful consumers leading to fast battery discharge. As criteria for the optimal performance of the proposed models and algorithms, the SOC parameters are considered - state of charge (%), battery charge (A * h), charge and discharge current of a battery (A), voltage on a battery during its charge when a charging current is absent or in a quiescent state (V), ambient temperature (˚C). Authors defined: composition of a control system, the necessary logic and a set of mathematical models implemented by electronic systems to control the charging balance of the automotive low-voltage power supply network, connections and functions of systems and components. As a result of a full-scale experiment, charge and discharge graphs, experimental data, current characteristics and dynamics of their changes during operation, experimental time-current dependencies during the operation of each component of a low-voltage power grid were obtained. The results of the work support to improve energy balance of an electrical power network, increase the efficiency and service life cycle of batteries, formulate system and technical requirements for control systems and their subsequent implementation. Versatility solutions are provided for improving management of charge balance car battery.

Preparation of 3D nanostructured MnCo2S4 as a robust electrocatalyst for overall water splitting

AbstractThe exploitation and use of efficient and inexpensive electrochemical catalysts accelerate overall water splitting, which rapidly produces oxygen and hydrogen. In this work, MnCo2S4 is grown on nickel foam by a two‐step method, hydrothermal and sulfuration method. Experiments have shown that the resulting MnCo2S4/NF exhibits a low overpotential of 310 mV to achieve a current density of 50 mA cm−2 in 1.0 M potassium hydroxide for oxygen evolution reaction (OER). In addition, the MnCo2S4/NF exhibits a low overpotential of only 167 mV at 10 mA cm−2 for hydrogen evolution reaction (HER). Furthermore, MnCo2S4/NF is acted as a bifunctional water splitting catalyst, and in 1.0 M potassium hydroxide, in order to maintain a current of 10 mA cm−2, a low battery voltage of 1.61 V is required. The nanostructure, which provides a large specific surface area, which in turn increases the reactive sites, facilitates contact of large areas of water with the catalyst, and rapid transfer of electrons. At the same time, through a series of characterization (XRD, SEM and XPS), it is proved that the catalyst is efficient and stable under alkaline condition.

A Family of Bidirectional DC–DC Converters for Battery Storage System with High Voltage Gain

In low power energy storage systems, to match the voltage levels of the low-voltage battery side and high-voltage direct current (DC) bus, a high voltage gain converter with bidirectional operation is required. In this system, the cost effectiveness of the design is a critical factor; therefore, the system should be designed using a small number of components. This paper proposes a set of bidirectional converters with high voltage gain range based on the integration of the boost converter with a Ćuk converter, single ended primary inductor converter (Sepic), and buck-boost converter. The proposed converters consist of a small number of components with a high voltage gain ratio. Detailed comparisons are made with respect to the operating mode, number of components, voltage, and current ripple and efficiency. The efficiency of proposed converters are higher than the conventional converters in entire power range, and 6% higher efficiency can be achieved in large duty cycle by calculating loss analysis. To verify performances of the proposed converters, three 200-W prototypes of the converters are developed under the same experimental conditions. The results revealed that converter I exhibits the highest efficiency in the boost mode (92%) and buck mode (92.2%). The experimental results are shown to verify the feasibility and performances of the set of converters.

Instantaneous Balancing of Neutral-Point Voltages for Stacked DC-Link Capacitors of a Multilevel Inverter for Dual-Inverter-Fed Induction Motor Drives

This paper proposes a novel method for instantaneous balancing of neutral-point (NP) voltages with stacked multilevel inverters (MLIs) for variable-speed drives. The stacked MLI uses series-connected dc sources and NPs (connecting points of dc sources) to obtain the desired levels. The balancing of NP voltages are obtained by using a low-voltage-capacitor-fed cascaded H-bridge (CHB) per phase of a symmetrical six-phase induction machine (IM), which ensures zero current drawn from NPs (at any given instant). Since no current is drawn from NPs, the single dc-link operation with stacked capacitors is also possible. The scheme is suitable for applications, where low-voltage dc sources and batteries are stacked to form a dc link. A variable-speed operation is done using a seven-level inverter scheme for a symmetrical six-phase IM, which is formed by three dc-link stacked capacitors cascaded with two low-voltage-capacitor-fed CHBs per phase. Furthermore, the method is extended for an open-end IM to obtain a seven-level common-mode eliminated space vector structure using a single dc link. The generalization of this method for any stacked $n$ -level inverter without NP voltage deviation is also presented in this paper. The experimental results and analysis are included to validate the proposed method.

Novel broken line detection circuit for multi‐cells Li‐ion battery protection ICs

To reduce the excessive power consumption and eliminate the battery voltage imbalance caused in conventional method, a novel broken line detection scheme for Li-ion battery protection integrated circuits (ICs) is presented in this study. The main part of the proposed circuit consists of pull-up, pull-down current source, source-driven MOS, a control switch and a bias current source. A narrow pulse control signal is adopted to trigger broken line detection periodically so as to suppress the detection current consumption, while the disadvantage of battery voltage imbalance is overcome. The proposed circuit has been implemented in a seven cells Li-ion battery protection IC with 0.18 µm 45 V bipolar-CMOS-DMOS process successfully. The experimental results confirm that the chip can reliably detect the disconnections of Li-ion batteries and take protective measures in a wide cell voltage range from 2.2 to 4.2 V. Furthermore, based on the derivation in this study, the proposed technique can significantly reduce the detection current consumption of each cell, which is well beneficial for low power consumption and battery voltage balance.

Power Management Strategy for the 48 V Mild Hybrid Electric Vehicle Based on the Charge-Sustaining Control

To enhance the 48 V mild hybrid electric vehicle performance using a smaller capacity and lower voltage battery than the full hybrid electric vehicle, a novel power management strategy needs to be established that considers the characteristics and limitations of the components. This paper proposes a charge-sustaining control strategy as a ground principle of the 48 V hybrid electric vehicle control for managing the battery state-of-charge (SOC) to stay near the most efficient regime. The base efficiency characteristics of the component models including engine, motor/generator, and battery are determined in the form of efficiency maps using the powertrain analysis tool. Then the control strategy is formulated as a nonlinear optimal regulation problem that meets two conflicting control objectives, such as fuel efficiency improvement and state-of-charge maintenance. The optimal regulation problem implements a discrete-time Hamilton-Jacobi-Bellman approach. The proposed strategy is evaluated by comparing with the reference strategy applying the Dynamic Programming (DP), i.e. a global optimal result, under urban dynamometer driving schedule and worldwide harmonized light duty test cycle. Through the evaluation, the fuel efficiency of the proposed strategy with three different electrical loads is slightly deteriorated at most by 5.03 % from the DP results with staying within a desirable SOC. This suggests that the proposed strategy is operating very closely to global optimal performances.

New Composite Equalization Strategy for Lithium Battery Packs

In order to improve the working efficiency of the power battery pack and prolong the service life, there is a problem of inconsistency among the individual cells. Based on the centralized equalization structure of the multi-output winding transformer, a three-stage hybrid equalization control strategy is designed for equalization. The equalization scheme realizes that the high voltage single battery transfers the energy to the low voltage battery cell during the charging of the battery pack, improving not only charging efficiency and energy use loss, but also the high voltage battery transferring the power to the low voltage battery cell when the pressure difference is greater than 10 mv during the discharge. Between 5 mv and 10 mv, it performs passive equalization, reducing the output fluctuation of the power battery pack and achieving the balance purpose. During the standing time, the maximum active balancing operation within the battery pack is performed in order to achieve intra-group optimum consistency. It is proved by experiments that the equalization control method can realize the quick and effective equalization in the battery pack, and the energy balance of each single battery.

Control and Optimization of Residential Photovoltaic Power Generation System With High Efficiency Isolated Bidirectional DC–DC Converter

Currently, residential photovoltaic power generation system is increasingly used worldwide. In this paper, an optimized structure of residential photovoltaic (PV) power generation system with 1500V DC bus is proposed. It includes PV panels, a three-level boost converter, a high efficiency isolated bidirectional DC-DC converter, battery and three-phase five-level DC-AC converter that can work under islanding mode or grid-connected mode. The higher DC bus voltage greatly reduces line loss and improves efficiency of the system. An energy management scheme used for the system is proposed in this paper to guarantee the stability of the system and to increase its economic benefits. Besides, the optimized method for the structure of the bidirectional dc-dc converter is proposed. This structure can achieve higher DC voltage gain and higher efficiency. Furthermore, for low voltage battery application in the residential system, LLC and CLLC under DC transformer (DCX) mode are evaluated and the LLC is selected as the isolated bidirectional DC-DC converter. The optimized designed method of bidirectional LLC is proposed. Finally, experiments are carried out to verify the performance of the optimized converters and the system.

An Overview of Bidirectional AC-DC Grid Connected Converter Topologies for Low Voltage Battery Integration

<p>Battery energy storage systems are becoming more and more popular solution in the household applications, especially, in combination with renewable energy sources. The bidirectional AC-DC power electronic converter have great impact to the overall efficiency, size, mass and reliability of the storage system. This paper reviews the literature that deals with high efficiency converter technologies for connecting low voltage battery energy storage to an AC distribution grid. Due to low voltage of the battery isolated bidirectional AC-DC converter or a dedicated topology of the non isolated converter is required. Review on single stage, two stage power converters and integrated solutions are done in the paper.</p>

A Battery Balancing Auxiliary Power Module With Predictive Control for Electrified Transportation

This paper proposes the integration of the auxiliary power module (APM) and nondissipative balancing hardware of a high-voltage battery. The proposed battery-balancing APM is projected to reduce the costs of nondissipative battery balancing by providing two functionalities: balancing of the high-voltage battery cells and charging of the low-voltage battery. This paper proposes two model predictive control strategies that address simultaneous balancing and charging. Both approaches make unbalanced charge available that increases the effective capacity of the high-voltage battery. The monolithic controller solves the balancing and charging problem as a single optimization problem. In contrast, the decoupled controller defines a separate control law for charging to achieve a higher bandwidth, e.g., for systems without dedicated low-voltage battery. The battery-balancing APM concept is validated on a software-in-the-loop and experimental test bench.

230 VDC elementary block in off-grid PV systems

This paper reports on a new development approach of off-grid systems based on PV and batteries, representing, among other things, a great interest for rural electrification in developing countries. A renewable energy production elementary block is proposed and analyzed. This block can work autonomously or as a basic element of a high power production cluster dedicated to rural areas. Replacement of AC bus by DC power bus is shown to be more advantageous thanks to better energy efficiency. The proposed approach also allows new architectures in the field of storage, and the systematic use of typical batteries associations, cause of their accelerated ageing, can thus be avoided. Each low voltage battery is found to be able to separately supply a high power standalone inverter or even a grid reinjection inverter following the retained boost ratio. The proposed architecture could be considered as a basis for solar DC micro-grids, gathering several individual producers on the same network, minimizing instabilities due to phase and frequency mismatches in case of AC grids. With even a high elevation ratio, the proposed block can be integrated in long-distances DC or HVDC power transport, thus, contributing to the improvement of wider spread of renewable energy.

An Improved Modulation Scheme of Current-Fed Bidirectional DC–DC Converters For Loss Reduction

Current-fed bidirectional dc–dc converters have attracted much attention in battery energy storage system applications due to their zero-voltage-switching performances and greater degree of control freedom. However, high efficiency cannot be achieved for both light and heavy load ranges with the present modulation schemes for a current-fed bidirectional dc–dc converter, especially with low battery voltages. A new modulation scheme is proposed to improve the conversion efficiency over a wide load range and with variations in the battery voltage. The relationship between the duty cycle of the secondary full bridge and the phase-shift angle was investigated to lower the power losses with the wide load variations. Based on the operation mode analysis, the control loop with the proposed pulse wide modulation plus phase-shift modulation scheme was developed. Comparisons of the switch conduction loss and the core loss in the series inductor for the previous modulation schemes and the proposed modulation scheme were carried out. The results show that lower power losses occur with the proposed scheme. The experimental results verify the theoretical analysis and effectiveness of the proposed modulation scheme on loss reduction.

A Distributed Optimization Approach for Complete Vehicle Energy Management

In this paper, a distributed optimization approach is proposed to solve the complete vehicle energy management (CVEM) problem of a hybrid truck with several controllable auxiliaries. The first part of the approach is a dual decomposition, which allows the underlying optimal control problem to be solved for every subsystem separately. For the second part of the approach, the optimal control problem for every subsystem is further decomposed by splitting the control horizon into several smaller horizons. Two methods for splitting the control horizon are used; the first method uses alternating direction method of multipliers and divides the horizon a priori , while the second method divides the horizon iteratively by solving unconstrained optimization problems analytically. We demonstrate the approach by solving the CVEM problem of a hybrid truck with a refrigerated semitrailer, an air supply system, an alternator, a dc–dc converter, a low-voltage battery, and a climate control system. Simulation results show that the fuel consumption can be reduced up to 0.52% by including smart auxiliaries in the energy management problem. More interestingly, the computation time is reduced by a factor of 64 up to 1825, compared with solving a centralized convex optimization problem.

Bidirectional Grid-Connected Single-Power-Conversion Converter With Low-Input Battery Voltage

This study proposes a bidirectional grid-connected single-power-conversion converter with low-input battery voltage. The proposed bidirectional converter consists of a bidirectional dc–dc converter and an unfolding bridge, and the power conversion stage only corresponds to a bidirectional dc–dc converter. The bidirectional dc-dc converter can perform bidirectional power conversion between the low input battery voltage and a rectified sine wave due to its step-up/down voltage regulation functions. The unfolding bridge unfolds the rectified sine wave into the grid voltage and provides a current path to the grid. The study also proposes a control algorithm to regulate the grid current through a single power-processing stage. The control algorithm is comprised of a feed-forward nominal voltage compensator and a repetitive control scheme. The feed-forward nominal voltage compensator presets the operating point to lighten the burden of the grid current control, and the repetitive controller provides precise control of the grid current. Thus, the proposed bidirectional grid-connected single-power-conversion converter results in high power quality and high efficiency. Experimental results based on a 250-W prototype module are conducted to evaluate the performance of the converter and to verify the analysis.

A High-Gain Reflex-Based Bidirectional DC Charger with Efficient Energy Recycling for Low-Voltage Battery Charging-Discharging Power Control

This study proposes a high-gain reflex-charging-based bidirectional DC charger (RC-BDC) to enhance the battery charging efficiency of light electric vehicles (LEV) in a DC-microgrid. The proposed charger topology consists of an unregulated level converter (ULC) and a two-phase interleaved buck-boost charge-pump converter (IBCPC), which together provide low ripple and high voltage conversion ratio. As the high-gain RC-BDC charges, the LEV’s battery with reflex charging currents, high battery charging efficiency, and prolonged battery life cycles are achieved. This is possible due to the recovering of negative pulse energy of reflex charging currents to reduce charge dissipations within LEV’s batteries. Derivations of the operating principles of the high-gain RC-BDC, analyses of its topology, and the closed-loop control designs were presented. Simulations and experiments were implemented with battery voltage of 48 V and DC-bus voltage of 400 V for a 500 W prototype. The results verify the feasibility of the proposed concept and were compared with the typical constant-current/constant-voltage (CC/CV) charger. The comparison shows that the proposed high gain RC-BDC improves battery charging speed and reduces the battery thermal deterioration effect by about 12.7% and 25%, respectively.

Onboard Battery Chargers for Plug-in Electric Vehicles With Dual Functional Circuit for Low-Voltage Battery Charging and Active Power Decoupling

This paper proposes a single-phase onboard battery charger (OBC) for plug-in electric vehicles, where the low-voltage (LV) battery charging circuit is utilized for an active power decoupling function. The OBC is operated in three different modes by sharing the transformer, switches, and capacitors. For a grid-to-vehicle mode or a vehicle-to-grid mode, the LV battery charging circuit serves as an active filter to eliminate the low-frequency power ripple at the DC link. Thus, the small film capacitors can be employed instead of large capacitors at the DC link. For the third operating mode, where the LV battery is charged from the HV battery, the isolation is provided by the dual active bridge (DAB) DC-DC converter. Since some components in the proposed OBC are used in common, the size and cost of the OBC can be reduced significantly. The simulation and experimental results have verified the validity of the proposed system.

Energy Management of Low Voltage Power Supply of Plug-in Hybrid Electric Vehicle

Under the pressure of energy crisis and environmental pollutions, regulations of automotive emission and energy consumption are becoming more and more stringent. Plug-in Hybrid Electric Vehicle (PHEV), which can solve environmental issues and mileage limitations, becomes the most popular development trend at present. Optimization control of power battery energy contributes greatly to improving vehicle fuel economy and dynamic performance, energy optimization control of vehicle low voltage power supply also has significant influence on vehicle fuel consumption and dynamic performance. In this paper, a Low-Voltage Power Supply Energy Management System (LVPSEMS) is proposed to optimize the energy of low voltage power supply of PHEV. Dynamic management voltage output of DC/DC is conducted and realized based on vehicle states, power battery SOC and low voltage battery status with the purpose of achieving fuel economy and dynamic performance of automobile. The tests in vehicle show that the proposed LVPSEMS and control strategy can effectively improve the pure electric mileage of 1.72% and reduce the electric energy consumption by 4%.

A Primary Full-Integrated Active Filter Auxiliary Power Module in Electrified Vehicles With Single-Phase Onboard Chargers

In single-phase ac high-voltage (HV) battery chargers, as the input current is enforced to be varying sinusoidally in phase with the input voltage, the pulsating power at two times of the line frequency will be seen on the dc-link. Bulky capacitor bank or extra active filter (AF) circuits are needed to assimilate this harmonic current, which become a major barrier in terms of power density and cost. Sinusoidal charging method can be applied, while this might affect the charging efficiency and a deep study is still needed to further investigate on the impact to the Lithium-ion battery. An active filter auxiliary power module (AFAPM) based dual-mode dual-voltage charging system for vehicle application has been proposed. The AFAPM converter has two modes: the HV active filtering mode, in which the vehicle is connected to the grid and the converter assimilates the significant second-order harmonic current; and the low-voltage (LV) battery charging mode, in which the vehicle is running and the converter charges the LV battery from HV battery. However, a relay and inductors are still required in that converter to achieve the dual-mode operation. This paper proposes a primary full-integrated AFAPM for electrified vehicle applications with single-phase onboard chargers. The proposed AFAPM converter is composed of a two-phase bidirectional buck converter to work as an AF and a dual-active-bridge to operate as a LV battery charger auxiliary power module (APM). With the proposed converter, only an extra active energy storage capacitor is needed to achieve the active filtering. All the switches and inductors on the primary stage are shared between the AF and APM. Therefore, the use of a bulky capacitor bank or an additional AF circuit is avoided and, thus, the cost, size, and weight of the dual-voltage charging system in the electrified vehicle applications can be reduced. A 720-W prototype has been built to confirm the effectiveness of the proposed converter.

Dynamic Response Improvements of Parallel-Connected Bidirectional DC–DC Converters for Electrical Drive Powered by Low-Voltage Battery Employing Optimized Feedforward Control

Parallel-connected modular current-fed bidirectional dc–dc converters are used for the AC motor drive system powered by batteries with low voltage and wide voltage range. The input current ripple can be reduced significantly by employing interleaving technology not only for individual module but also for all the modules. A current sharing control strategy is applied for the constituent modules. Double pulse width modulation plus double phase shifted control with equal duty cycles for one module can minimize the circulation loss and avoid nonactive power issue. Factors affecting dynamic performance are investigated based on the small-signal modeling. The leakage inductance value is optimized in view of system reliability and better dynamic performance. Besides, to improve the dynamic performance further, feedforward control employing optimized feedforward coefficient based on the small-signal analysis is implemented. A 4-kw prototype composed of two bidirectional dc–dc converters is built to verify the effectiveness for the proposed control strategy in AC motor drive application with fast regenerative braking.