Constant Voltage Mode Research Articles

Two‐/three‐coil hybrid topology and coil design for WPT system charging electric bicycles

Wireless power transfer (WPT) for charging electric bicycles (EBs) can save people from tiresome plugging actions and avoid electrical shock hazards, especially in adverse weather. This study proposed a two-/three-coil hybrid topology to achieve constant current (CC) and constant voltage (CV) for charging EBs, simplifying control schemes. The system realises CC output with two-coil topology and operates in CV mode with three-coil topology by turning on a switch. Besides, an inductor array is used to compensate reactive power in CV mode when massive EBs are charged by one high-frequency inverter (HFI). The secondary side of the proposed topology is compact, and the number of components and HFI can be reduced. A coil design process based on double-D-type for the three-coil system is given, with the constraint of mutual inductances among three coils and limited size. To demonstrate the validity of the proposed methods, an experimental setup is built, and the performance of the two-/three-coil hybrid system indicates that the fluctuations of charging current and voltage are <0.64 and 2.12% in the whole charging profile. Moreover, the performance of two WPT chargers connected with one HFI hints that massive EBs can be charged with only one HFI.

Multi-time-scale energy management strategy considering battery operation modes for grid-connected microgrids community

The advantages and promoting applications of the microgrids community (MGC) allows for a critical step being taken toward a smart grid. An energy management strategy (EMS) is essential to intelligently coordinate the operations of the MGC. This paper presents a multi-time-scale EMS considering battery operational modes for grid-connected MGCs. The proposed strategy consists of two modules: day-ahead integrated optimization and realtime distributed compensation. The first module aims to minimize the operational cost of the MGC considering battery free-overcharging protecting. This problem is solved by the mixed integer linear programming (MILP) simulating two charging/discharging modes: limited-current mode and constant-voltage mode. The second module is installed in local MGs to correct the optimizing deviations of the dayahead static scheduling, which are caused by predicting errors of renewable energy and loads. The main contribution of this work is integrating the advantages of global optimization of the centralized method and the fast computing speed of the distributed method. Experimental results prove the proposed EMS is feasible and effective. The computing time at each updating step is reduced by 75% on average, which has the potential to be adopted in engineering.

Double-wire tandem GMAW welding process of HSLA50 steel

Tandem welding process employs double wire feed in a single torch, providing increased deposition rate and consequent reduction in process times. However, the process complexity increases since an optimum combination of parameters is essential to avoid the occurrence of interference between both electric arcs. Such interferences may result in hindering stability of the welding process, leading to poor weld bead geometry. To address this problem, the present investigation proposes an approach to reduce the number of arc’s inconsistencies during welding of a 15-mm HSLA50 steel plate with ER70S-6 wire. Three configurations were tested considering high-current ratings in lead and trail wires: pulsed-pulsed waves (torch angle: 90°), continuous-pulsed waves (torch angle: 90°) and continuous-pulsed waves (torch angle: 80°). In the three cases, the welding arc voltage and currents were acquired, and penetration profile and the dimension of the heat affected zone (HAZ) evaluated. Microhardness testing was utilized to investigate the mechanical strength of the HAZ. The best combination of parameters was found considering the three welding conditions tested in this study, where the lead wire was parameterized in constant voltage mode and the trail wire in pulsed spray metal transfer with a torch angle of 90 ° from the workpiece. 20% higher displacement speed of the robot and no occurrence of inconsistences in the electric arcs were accomplished.

Preparation and formation mechanism of copper incorporated micro-arc oxidation coatings developed on Ti-6Al-4V alloys

Micro-arc oxidation (MAO) was used to fabricate light-red coatings with a maximum Cu amount of 3.06 wt% on Ti-6Al-4V alloys in electrolytes composed of Na2CuY, KOH, and phytic acid. The influences of electrolyte composition and concentration as well as the electrical control mode on coating properties were investigated. In addition, the cathode surface after MAO treatment was first characterized. The results show that the used electrolytes determine the coating composition and surface morphology through influencing the solution pH and conductivity. During MAO, copper is simultaneously involved in the formation of the MAO coating on the anode and the precipitation of metallic Cu on the cathode. The copper content in MAO coatings can be improved slightly by Na2CuY and significantly by KOH attributed to their influences on solution pH. Phytic acid is beneficial in developing MAO coatings, but at higher concentrations up to 4 g/L decreases the copper content. The copper in MAO coatings exists primarily in the form of Cu2O, while metallic copper particles in the range of 150–600 nm are deposited on the cathode through the reduction reaction. Compared with the constant current density mode, the fabricated MAO samples under the constant voltage mode contain a lower content of Cu and more evident microcracks.

Three‐coil structure‐based WPT system design for electric bike CC and CV charging without communication

In comparison with the traditional plug-in charging systems for the electric bike (EB), wireless power transfer (WPT) systems have superior advantages of convenience and safety. Combining the application requirement range of the EB, this study proposes a three-coil structure-based WPT system in order to achieve ideal and reliable constant current (CC) output and constant voltage (CV) output without the need for a sophisticated control strategy and the real-time communication links between the transmitter and receiver sides. Two ac switches are utilised at the transmitter side to implement the change of charging mode from CC to CV. By correctly selecting the parameters of compensation components, the required load-independent CC and CV characteristics with zero phase angle in the CC and CV modes can be achieved. Besides this, a load identification method based on the active power calculation used to estimate the equivalent resistance of the battery in the whole charging process, is utilised to judge the switching point from CC to CV mode. Finally, the feasibility of the method is verified through the construction of a laboratory platform with a 3.3 A charging current and a 57 V charging voltage.

Inductive Power Transfer to Charge Electric Bicycles

Inductive power transfer is nothing but wireless power transfer. That is transferring power from transmitter to receiver side without any physical contact. Nowadays this technique has wide applications. Mainly it is used to charge the batteries of the electric vehicles (EV). Due to the increasing pollution rate and scarcity of fuel in future days, the demand for the electric vehicles is increasing. Charging EV’s using IPT is simpler and risk free when compared to traditional wired charging systems. Using IPT technique the battery can be charged in constant current (CC) and constant voltage (CV) modes without using any feedback. A switch (consists of 2 AC switches and capacitor) is used to change the mode from CC to CV. The current output from the CC and the voltage output from the CV mode are load independent. This can be obtained by proper selection of inductances and capacitors. Here the feedback control techniques are not required to regulate the output according to charging profile. This IPT technique to charge battery is economical because using a single inverter many batteries can be charged at a time. The possibility of this method of charging is tested with an experimental prototype for efficiency and using MATLAB/SIMULINK software the simulation results are obtained for stability of current and voltage output of CC and CV mode.

Power Factor Improvement in Modified Bridgeless Landsman Converter Fed EV Battery Charger

This work deals with the design and implementation of a new charger for a battery-operated electric vehicle (EV) with power factor improvement at the front end. In the proposed configuration, the conventional diode converter at the source end of existing EV battery charger is eliminated with the modified Landsman power factor correction (PFC) converter. The PFC converter is cascaded to a flyback isolated converter, which yields the EV battery control to charge it, first in constant current mode then switching to constant voltage mode. The proposed PFC converter is controlled using single sensed entity to achieve the robust regulation of dc-link voltage as well as to ensure the unity power factor operation. The proposed topology offers improved power quality, low device stress, and low input and output current ripple with low input current harmonics when compared to the conventional one. Moreover, to demonstrate the conformity of the proposed charger to an IEC 61000-3-2 standard, a prototype is built and tested to charge a 48 V EV battery of 100 Ah capacity, under transients in input voltage. The performance of the charger is found satisfactory for all the cases.

A stable operation method for membrane capacitive deionization systems without electrode reactions at high cell potentials

A method for operating membrane capacitive deionization (MCDI) systems without electrode reactions at a high cell potential was studied. The charge supplied to the cell was controlled to suppress Faradaic reactions. The maximum allowable charge (MAC) that can be supplied to a carbon electrode without electrode reactions was measured to be 58 C/g. Adsorption experiments were conducted while supplying a charge of 55 C/g (95% of the MAC value) in constant-current (CC) and constant-voltage (CV) mode. The cell potential increased to 1.42 V in CC (1.43–4.29 mA/cm2) mode, but the concentration and pH of the effluent were kept constant. In addition, the effluent pH was stable in CV (1.25–2.0 V) mode. The salt adsorption capacities and charge efficiencies were approximately 15.5 mg/g and 92%, respectively, regardless of the current densities and cell potentials applied to the cell. With increasing cell potential, the concentration polarization in the feed stream was intensified, resulting in an increase in cell resistance. It was thought that electrode reactions did not occur at a high cell potential because of the high voltage drop due to the cell resistance. The higher the cell potential (or current density) is, the faster the desalination rate in MCDI operation. It is expected that this operation method applying the MAC concept will contribute to the stable operation of MCDI systems and an improvement in desalination performance.

LLC Resonant Converter for LEV (Light Electric Vehicle) Fast Chargers

This paper presents a Light Electric Vehicle (LEV) fast charger with a Lithium-Ion Battery (LIB) and Super-Capacitor (SC). The LEV fast charger consists of an AC/DC rectifier and LLC (Inductor-Inductor-Capacitor) resonant Full bridge converter. The LLC resonant converter has high-efficiency and low switching loss because of Zero Voltage Switching (ZVS). So, it is used widely in the industry. In general, the fast charger algorithm uses the Constant Current (CC) mode and Constant Voltage (CV). The CC mode starts at first and then the CV mode finishes. However, there is a big control value gap between the CC mode and CV mode. Therefore, when changing from CC to CV, the transient state occurs. To compensate for the transient state, we propose a new control algorithm. By means of this algorithm, we can achieve a higher level of safety and stability. The fast charger with LIB of 800 Wh and SC of 50 Wh is analyzed and verified, and we obtain a maximum efficiency of 96.4%. The discussions are validated using the LLC resonant full bridge converter prototype at the laboratory level.

Implication of Non-electrostatic Contribution to Deionization in Flow-Electrode CDI: Case Study of Nitrate Removal From Contaminated Source Waters.

While flow-electrode capacitive deionization (FCDI) operated in short-circuited closed cycle (SCC) mode appears to hold promise for removal of salt from brackish source waters, there has been limited investigation on the removal of other water constituents such as nitrate, fluoride or bromide in combination with salt removal. Of particular concern is the effectiveness of FCDI when ions, such as nitrate, are recognized to non-electrostatically adsorb strongly to activated carbon particles thereby potentially rendering it difficult to regenerate these particles. In this study, SCC FCDI was used to desalt source waters containing nitrate at different concentrations. Results indicate that nitrate can be removed from source waters using FCDI to concentrations <1 mg NO3-N L−1 though a lower quality target such as 10 mg L−1 would be more cost-effective, particularly where the influent nitrate concentration is high (50 mg NO3-N L−1). Although studies of the fate of nitrate in the FCDI system show that physico-chemical adsorption of nitrate to the carbon initially plays a vital role in nitrate removal, the ongoing process of nitrate removal is not significantly affected by this phenomenon with this lack of effect most likely due to the continued formation of electrical double layers enabling capacitive nitrate removal. In contrast to conventional CDI systems, constant voltage mode is shown to be more favorable in maintaining stable effluent quality in SCC FCDI because the decrease in electrical potential that occurs in constant current operation leads to a reduction in the extent of salt removal from the brackish source waters. Through periodic replacement of the electrolyte at a water recovery of 91.4%, we show that the FCDI system can achieve a continuous desalting performance with the effluent NO3-N concentration below 1 mg NO3-N L−1 at low energy consumption (~0.5 kWh m−3) but high productivity.

Consistency analysis of polymer electrolyte membrane fuel cell stack during cold start

This paper investigates the cold start characteristic of the polymer electrolyte membrane fuel cell stack in the constant voltage startup mode. The stack is used in actual vehicle working conditions, so it is practical significance to study the cold start characteristics of the stack. The evolution of the temperature and current density distribution at different regions in the constant voltage mode of the stack are studied. Consistency analyzes from two dimensions, in-plane and through-plane are studied. Then, the performance degradation of the stack after the cold start is explored through the polarization curve and the voltage consistency.The cold start characteristics and performance degradation mechanism of the stack are found. The stack has better cold start performance than that of the single cell, which can realize a rapid cold start at −15 °C in 95 s. Also, the performance of the single cell in the middle position is obviously better than that of the single cell on both sides. The internal behavior of each single cell during cold start process is different and the performance consistency is poor after the failed cold start. The performance degradation gradually decreases from the single cell near the inlet to the single cell far away from the inlet. This paper can provide direction for the optimization cold start strategy.

Reconfigurable Intermediate Resonant Circuit Based WPT System With Load-Independent Constant Output Current and Voltage for Charging Battery

In this letter, a compact battery charger based on wireless power transfer (WPT) technology without any communication requirement is proposed. Here, a new intermediate coil is developed to achieve load-independent constant current (CC) and constant voltage (CV) outputs. The intermediate coil is split into two coils and is overlapped with the receiver coil to form a compact structure. Two switches on the receiver side are used to reconfigure the intermediate resonant circuit in order to select different charging modes, i.e., CC mode or CV mode. The communication between the transmitter side and the receiver side as well as complex control strategies is not needed in the proposed structure. Besides, the proposed system can achieve zero phase angle operation, fixed operating frequency, and zero-voltage switching, which not only can lower the power rating of power devices but also improve the efficiency. A laboratory prototype with a 3.6 A charging current and a 48 V charging voltage is built to verify the feasibility of the proposed method.

Electro-dewatering of sewage sludge: Influence of combined action of constant current and constant voltage on performance and energy consumption

In this study, mechanically-dewatered sludge was used to investigate the effect of electro-dewatering (EDW) under two electrical modes, which are constant current mode followed by constant voltage mode (CV-EDW), and constant voltage mode followed by constant current mode (VC-EDW). The effect of current and voltage changes on dewatering efficiency and energy consumption of sludge electroosmosis under CV-EDW and VC-EDWs was evaluated The results show that compared with constant current mode (C-EDW), CV-EDW can improve the final dry solids content and reduce the heating rate, and the final dry solids content and unit energy consumption increase with the decrease of current and the increase of voltage. Under CV-EDW, when the dry solids content is 32%, the energy consumption can be reduced by changing to the constant voltage stage, and the energy consumption is 0.093–0.113 kWh/kgwater. Compared with constant voltage mode (V-EDW), VC-EDW significantly improves sludge dewatering rate. Under VC-EDW, the final dry solids content of sludge increases with the decrease of current and voltage. When the voltage is decreased by 10 V, the unit energy consumption is reduced by 27.15 ± 1.77% on average, and the energy consumption is 0.132–0.163 kWh/kgwater. Compared with CV-EDW, the dehydration rate of VC-EDW is increased by 72.9% on average. However, the unit energy consumption required for dehydration increases by 43.09% when the dry solids content is less than 45%.

Investigation on cold start of polymer electrolyte membrane fuel cells with different cathode serpentine flow fields

The flow velocity and pressure distribution of the three cathode flow fields are simulated in this study. Larger pressure drop and more rapid flow rate reduce residual water, resulting in minimal ice formation during the cold start process. The simulation results show that the single variable cross section serpentine flow field has the largest pressure drop and the most rapid flow rate.The evolution of the temperature and the segment current density characteristics of three different cathode flow fields during cold start process is studied by printed circuit board technology. The results show that the 2 to 1 serpentine flow field has the best cold start performance and the best current density uniformity when cold start at constant voltage mode above −5 °C. However, the single variable cross section serpentine flow field has the best performance when cold start temperature is below −5 °C. Based on these results, cold start at −30 °C can be realized in 97s by using hot antifreeze liquid.

Intelligent closed-loop deep brain stimulation modulation platform with multi-sensor information feedback

This paper describes an intelligent closed-loop deep brain stimulation modulation platform with multi-sensor information input feedback, adaptive, interactive, and high integration. This platform has 16 channels of data acquisition channels and 4 channels of stimulation channels. Four channels of the acquisition channel are used for intracranial LFPs acquisition, and 12 channels are used for acquisition of extracranial signals (EEG, ECG and EMG). The output waveform of stimulation channels is a configurable and arbitrary waveform. The stimulation voltage is in constant voltage mode, the stimulation voltage range is -5 V ∼ +5 V, and the impedance range of the stimulation load is 500 Ω ∼ 5 KΩ. This study achieved simultaneously the stimulation at the recording, which effectively reduces the influence of the stimulation artifacts on the recorded signal. The platform constructs multi-information closed-loop deep brain stimulation for Parkinson's disease from three aspects: motor behavior signal feedback, extracranial electrical signal feedback, and deep brain field potential signal feedback. A modular portable and universal closed-loop neuromodulation research platform has been formed. This study completed the acquisition and recording and adaptive closed-loop algorithm and stimulation function, effectively eliminating the stimulus artifacts, adapting to wide dynamic range brain impedance, and enhancing the stability of stimulus output. It has the characteristics of compact structure, small size, low power consumption and stable operation.

Optimization of Time-Weighted Average Efficiency for Reconfigurable IPT Battery Charging System

Constant current (CC) and constant voltage (CV) combined charging is considered as the most popular and efficient method for charging batteries. There are a lot of works done to achieve CC/CV characteristics by utilizing reconfigurable circuits for easy control but without the consideration of efficiency optimization in the CV mode. In this paper, the optimization of mutual-inductance proportion between transmitter/receiver mutual inductance and transmitter/intermediate mutual inductance of the three-coil circuit is investigated to maximize the time-weighted average efficiency (TWAE). With two switches, a section of receiver coil of the series-series (SS) circuit, which corresponds to the optimized mutual inductance proportion, can be converted into an intermediate coil of the three-coil circuit. Therefore, the system can be transferred from the CC mode to CV mode, and with the optimized mutual-inductance proportion, the efficiency in the CV mode can be improved. An experimental prototype is built to validate the feasibility of the proposed approach. In the CC (CV) mode, the impedance range is 30-108 Ω (108-500 Ω), and the maximum fluctuation for current (voltage) is 3.37% (4.55%). Besides, the TWAE is 94.5% (maximum 95.3% and minimum 94.49%) for the three-coil circuit, while that of SS circuit with control is 91.54% (maximum 95.20% and minimum 85.31%).

A Hybrid Compensation Topology With Single Switch for Battery Charging of Inductive Power Transfer Systems

This paper presents an inductive-power transfer (IPT) system with load-independent constant current (CC) and constant voltage (CV) charging characteristics for low power systems. An inductor-capacitor-capacitor series (LCC-S) compensation-based hybrid topology that can achieve both CC and CV charging with only one additional switch under zero-phase-angle conditions is proposed. Additionally, the CC/CV charging mode can be realized with two different fixed frequencies. The proposed system has a simple structure and low cost and uses only primary-side electrical information to control the battery charging profile, achieving communication-less control between the primary and secondary sides. It greatly simplifies the controller design process. A 200-W laboratory prototype is built to verify the feasibility of the proposed topology, and the maximum efficiencies of the CC and CV modes are approximately 85% and 87%, respectively.

Switched-Boost Action Based Multiport Converter

Multioutput converters with single input source are currently studied as an alternative to conventional dc–dc topologies in order to improve power density in low-power multiload applications. This paper reviews three different ways in which a boost topology can be customized to supply multiple outputs. The first way uses a charge-sharing approach using individual switches to distribute inductor energy to different capacitors. The second method of creating a multiport converter (MPC) combines two converters with similar front end to generate two outputs using only one controlled switch. Using this method, a boost converter can be combined with single–ended primary–inductor converter (SEPIC), Cuk, and current source converter topologies. The third method uses time multiplexing of switches to produce two regulated ports and is referred to as switched-boost action. This method uses relatively less number of switches and allows regulation and control of all the outputs. Practical utility of switched-boost action based MPC is reported in this paper. This switched-boost MPC is applied to a renewable power converter system to interface a solar panel, a battery, and home loads to produce a 12-V and a 48-V bus. The 12-V bus is interfaced to battery and capable of optimally charging the battery in constant current–constant voltage (CC-CV) mode. The converter is demonstrated to operate with solar panel as it supplies a 12-V battery and a 48-V load bus. When the solar power is not available, the converter automatically goes into a mode in which the 12-V battery supplies the loads on the 48-V bus.

Analysis and Design of Three-Coil Structure WPT System With Constant Output Current and Voltage for Battery Charging Applications

Compared with the traditional plug-in charging system, the wireless charging system for battery charging has broad application prospects due to its significant advantages, such as security, convenience, and aesthetics. In practical applications, in order to prolong the battery lifecycles, it is preferred to charge the battery with constant current (CC) and constant voltage (CV) modes. However, since the battery equivalent resistance varies greatly during charging, it is not easy to design a complete charging system owning CC and CV output characteristics. Besides, the equivalent input impedance of the system is preferably resistive to improve efficiency and enhance power transfer capability; therefore, achieving the zero phase angle (ZPA) operation is extremely important. Hence, a novel three-coil structure WPT system is proposed in this paper to solve the above issues. A comprehensive theoretical analysis for the three-coil system to realize the CC and CV charging modes with perfect ZPA operation at two fixed operating frequencies is presented. Furthermore, due to the parasitic losses of passive components and the instability of the dc input voltage, it is unrealistic to achieve accurate and stable CC and CV outputs through the inherent properties of the circuit itself. Consequently, a simple closed-loop controller is introduced into the system to enable the desired CC and CV charging characteristics with zero voltage switching (ZVS) operation by slightly adjusting the operating frequency. Finally, a confirmatory experimental prototype with 4.6-A charging current and 56-V charging voltage is fabricated to confirm the feasibility and validity of the proposed method. The experimental results agree well with the theoretical analysis.

Step‐charging technique for CC/CV mode battery charging with low‐cost control components in IPT systems

In wireless power transfer technology, power control technique is required to realise constant current (CC) and constant voltage (CV) modes for battery charging. CC and CV modes are needed to effectively charge lithium (Li)-ion batteries to ensure long life span and maximum capacity utilisation. The use of additional battery charging circuitry reduces efficiency, increases volume, and increases circuit complexity. The frequency modulation method is a method that can control power without an additional charging circuit, but a high-resolution controller is needed to control the voltage and current for charging the battery by frequency modulation. This study proposes a system that controls current and voltage for CC and CV modes through a step-charging method using a battery hysteresis with a low-cost control system. The in-band communication circuit is analysed and used to link the primary and secondary sides of the inductive power transfer (IPT) coils, which enables effective feedback control without an additional wireless communication module. This method enables high-efficiency charging while minimising the overall size and cost of mobile IPT applications such as power tools. The proposed system shows 90.3% transfer efficiency with a 20.75 V, 4 Ah Li-ion battery at 7 mm distance.