The charge equalization for the battery power source with battery power modules (BPMs) in series is presented in the thesis. The bidirectional power converters in BPMs are able to serve as chargers with buck conversion during the charging stage. Even though connected in series, all modules can substantially be operated individually, retaining the advantages of independent operation, such as flexible control, easy protection, simple maintenance, and favorable battery power management. Investigation results indicate that automatic charge equalization is possible for the discontinuous conduction mode (DCM) operation. On the other hand, charge equalization can be achieved much faster by individually regulating the charging currents at the continuous conduction mode (CCM). According to the analyzed results, an equalization strategy is proposed to solve the charge imbalance problem by scheduling the individual battery current. Experiments are carried out to demonstrate the effectiveness of charge equalization.

This thesis investigates the discharging behavior of serial boost-type battery power modules (BPMs). Even though the BPMs are connected in series to cope with a higher output voltage, all batteries in the BPMs can substantially be operated individually so that can realize the balanced discharging control strategy. By which, the battery currents are scheduled in accordance with their state-of-charges (SOCs).A battery power system formed by 10 boost-type BPMs is built, in which a micro controller is used for detecting the loaded voltages, estimating the SOCs, and controlling the duty ratios of the power converters. Experimental results demonstrate the balanced discharging capability of the serial BPMs. In addition, fault tolerance mechanism is introduced to isolate fault or exhausted batteries and keep the system working with a reduced load.

This thesis presents a novel configuration of battery power by the outputs with serial connection of battery power modules (BPMs) for high voltage level loads. As compared to the conventional application of series-connected battery bank, this configuration operates the BPMs individually, and thus has the advantages of flexible control, convenient maintenance, and easily favorable battery management. The associated converter is equipped to a single battery pack, so that has lower component stresses leading to a higher circuit efficiency. The operation and the design of a lead-acid battery power with series boost-typed BPMs are illustrated. The operation and the design of the converter are illustrated. The control of the power converters is accomplished by a complex programmable logic device (CPLD). To improve the converter efficiency, the technique of synchronous rectification is introduced. For the BPMs designed for discontinuous conduction mode (DCM) operation, charge equalization can be automatically achieved under the same duty-ratio, but is adequate only for batteries with a small difference. On the other hand, charge equalization for the BPMs with continuous conduction mode (CCM) can easily be accomplished by regulating the duty-ratios of the converters.

A novel battery power system configured by the battery power modules (BPMs) is proposed. Each BPM consists of a single battery pack or a battery bank equipped with an associated DC/DC converter. The output ports of BPMs can be connected in series for the high voltage applications, or in parallel to cope with a higher power or energy. For a large scale battery power system, a number of BPMs can be arrayed with combination of series and parallel connections to meet the load requirements. These all configurations allow the BPMs be operated individually. Consequently, the discharging currents of the batteries can be independently controlled, but coordinated to provide a full amount of the load current. The performances of BPMs connected in both parallel and series at outputs are analyzed theoretically and discussed from the experimental results. Batteries operating independently do not suffer from charge imbalance, and thus can avoid being over-charged or over-discharged, so that the life cycle can be prolonged. Furthermore, sophisticated discharging profiles such as intermittent currents can be realized to equalize the charges and thus to efficiently utilize the available stored energy in batteries. During the operation period, some of the batteries may take rest or be isolated from the system for the open-circuit measurement, facilitating the estimation of the state-of-charge (SOC) and the evaluation of the state-of-health (SOH). With the benefit of independent operation, the BPMs can be discharged with a scheduled current profile, such as intermittent discharging. The investigation results show that the average current plays the most important role in current discharging. By detecting the battery voltage at the break time, an SOC estimation method based on the dynamically changed open-circuit voltage exhibits an acceptable accuracy in a shorter time with considerations of the previous charging/discharging currents and the depth-of- discharge (DOD). In addition, the coulomb counting method can be enhanced by evaluating the SOH at the exhausted and fully charged states, which can be intended on the independently operated BPMs. Through the experiments that emulate practical operations, the SOC estimation methods are verified on lead-acid batteries and lithium-ion batteries to demonstrate the effectiveness and accuracy.