Ming-Wang Cheng

Intelligent control battery equalization for series connected lithium-ion battery strings

An intelligent battery equalization scheme based on fuzzy logic control is presented to adaptively control the equalizing process of series-connected lithium-ion batteries. The proposed battery equalization scheme is a bidirectional dc-dc converter with energy transferring capacitor that can be used to design the bidirectional nondissipative equalizer for a battery balancing system. Furthermore, it can be designed as a ripple-free converter for improving the input current distortion of the battery charge supply power system. A fuzzy-logic-controlled strategy is constructed with a set of membership functions to prescribe the cells equalizing behavior within a safe equalizing region for rapid cell voltage balancing. The simulation and experimental results show the advantage of the predicted equalizing performance of the lithium-ion battery stacks. The proposed fuzzy logic control battery equalization controller can abridge the equalization time about 32%. The proposed method maintains safe operation during the charge/discharge state in each lithium-ion cell of the battery strings.

Individual Cell Equalization for Series Connected Lithium-Ion Batteries

A systematic approach to the analysis and design of a bi-directional Cuk converter for the cell voltage balancing control of a series-connected lithium-ion battery string is presented in this paper. The proposed individual cell equalizers (ICE) are designed to operate at discontinuous-capacitor-voltage mode (DCVM) to achieve the zero-voltage switching (ZVS) for reducing the switching loss of the bi-directional DC/DC converters. Simulation and experimental results show that the proposed battery equalization scheme can not only enhance the bi-directional battery equalization performance, but also can reduce the switching loss during the equalization period. Two designed examples are demonstrated, the switch power losses are significantly reduced by 52.8% from the MOSFETs and the equalization efficiency can be improved by 68-86.9% using the proposed DCVM ZVS battery equalizer under the specified cell equalization process. The charged/discharged capacity of the lithium-ion battery string is increased by using the proposed ICEs equipped in the battery string.

Fuzzy controlled fast charging system for lithium-ion batteries

A DSP is adopted to construct a fuzzy controlled lithium-ion battery charging system. By using this intelligent charging system, the data collection, calculation and peripheral circuit control are performed for the battery charging status. According to the lithium-ion battery charging specifications, two hours are required for battery charging. A fuzzy logic controller (FLC) is constructed by using the battery protection cell voltage and voltage difference among the batteries. They are used as the input variable to shorten the charging and equalizing time and assure that the battery will be operated within the safety voltage range.

Time Domain Measurement System for Conducted EMI and CM/DM Noise Signal Separation

This article discusses how to use a digital oscilloscope to match the time-domain measurement computer-aided technique and Fourier transformation to measure the conducted EMI. Taking advantage of the multi-channel oscilloscope and the computer, it will deal with the Line and Neutral lines synchronization. It can mitigate the phase coherency problem to separate the common-mode (CM) and differential-mode (DM) EMI noise at the same time without any hardware implementations. Due to the time-domain measuring method, which allows the noise amplitude and phase in parallel processing for the whole spectrum range, measuring time is reduced. The computerized time-domain measurement environment is based upon the LabVIEW test and measurement system. The separation results are compared with the frequency-domain measurements. The proposed time-domain measured system can provide a user friendly and convincible approach for fast EMI measurement and countermeasures.

Cell voltage equalization using ZCS SC bidirectional converters

A quasi-resonant zero current switching (QR ZCS) switch-capacitor (SC) converter for the cell voltage balancing control of a series connected battery string is presented in this paper. The proposed cell voltage equalizers (CVE) are designed to operate in the discontinuous-current mode (DCM) to achieve zero-current switching (ZCS) for reducing the switching loss in the bi-directional DC/DC converters. Results indicate that the switching loss, conducted EMI emissions and equalization efficiency can be substantially improved using ZCS technology in the battery charging system with the CVE. The validity of the battery equalization is further verified using a three cells lithium-ion battery string installation. Simulation and experimental results show that the proposed battery equalization scheme can enhance the bi-directional battery equalization performance and also reduce the switching loss and conducted EMI emissions during the equalization period. Equalization efficiency above 90% can be achieved by the proposed QR ZCS battery equalizer under the specified cell equalization process.

ZCS Switched-Capacitor Bi-directional Quasi-Resonant Converters

This paper presents the new topologies of zero-current switching switched-capacitor (ZCS SC) quasi-resonant converters with bidirectional power flow control conversion schemes. It possesses the features of quasi resonant switched-capacitor converters: low weight, small volume, high efficiency, low EMI emission and low current stress. A family of zero-current switching switched-capacitor bidirectional converters is proposed to improve the current stress problem during the bidirectional power flow control processing. They are able to provide the voltage conversion ratios from double-mode/half-mode to n-mode/1/n mode by using four power MOSFET main switches and a set of switched-capacitors with a small series connected resonant inductor for non-inverting or inverting modes. The operation principle of converter operation of the proposed bi-directional power conversion scheme is described in detail with circuit model analysis for non-inverting mode. Simulation and experimental results are carried out to verify the concept and the performance of the proposed double-mode/half-mode ZCS SC bi-directional quasi-resonant converters.

Fuzzy Controlled Individual Cell Equalizers for Lithium-Ion Batteries

A fuzzy logic control battery equalizing controller (FLCBEC) is adopted to control the cell voltage balancing process for a series connected Li-ion battery string. The proposed individual cell equalizer (ICE) is based on the bidirectional Cuk converter operated in the discontinuous capacitor voltage mode (DCVM) to reduce the switching loss and improve equalization efficiency. The ICE with the proposed FLCBEC can reduce the equalizing time, maintain safe operations during the charge/discharge state and increase the battery string capacity.

Intelligent charged system for Lithium-ion battery strings

We use DSP to construct an intelligent Lithium-ion battery charging system. By adopting this intelligent charging system, we perform the data collection, calculation and peripheral circuit control for the battery charging status. According to the lithium-ion battery charging specifications, two hours are required for battery charging. A fuzzy controller constructed using the battery protection voltage and voltage difference among the batteries is used as the input variable to shorten the charging and equalizing time and assure that the battery will be operated within the safety voltage range.

Measurement and Mitigation of Conducted Emission for Voltage Phase Controlled Capacitor-Run Single Phase Induction Motor

A TRIAC-based voltage phase speed controller is typically used to control the voltage of the winding of a variable speed single phase induction motor. Transient voltage and highly harmonic current will be produced when TRIAC switches turn on and off. This will result in significantly conducted emissions, causing serious problems concerning the EMI issue. This paper presents a measurement and mitigation method of the conducted electromagnetic interference (EMI) for the voltage phase controlled capacitor-run single-phase induction motor (CR SPIM). The conventional and improved voltage phase controlled schemes, for the speed control of the SPIM driving system are investigated. The measuring results of the common mode (CM) and differential mode (DM) are compared and used to design a power line filter to improve the conducted EMI performance, compliant with the regulatory requirement of CISPER 22/EN5502.

Generalized Construction of ZCS Switched-Capacitor Bi-directional Converter

The proposed zero-current switching switched-capacitor (ZCS SC) DC-DC converter is an innovative bi-directional power flow control conversion scheme. A zero-current switching switched-capacitor step-up/step-down bi-directional converter is presented that can improve the current stress problem during bi-directional power flow control processing. It can provide a high voltage conversion ratio of n/1 n (n-mode/1 n-mode) us-ing four power MOSFET main switches, a set of switched-capacitors and a small resonant inductor. Simulation and experimental results are carried out to verify the concept and performance of the proposed quadruple-mode/quarter-mode bi-directional DC-DC converter.