Multibattery-Fed Neutral-Point-Clamped DC–AC Converter With SoC Balancing Control to Maximize Capacity Utilization

Abstract

This paper studies a multilevel multiphase dcac conversion system configured by a neutral-pointclamped converter fed by multiple battery packs connected in series. A virtual-vector modulation is selected and a state-of-charge (SoC) balancing control is designed to be able to employ the full battery bank capacity, even under different battery initial SoC values or different battery nominal capacities. The SoC balancing among battery packs is accomplished through the multilevel converter operation in a lossless manner, by simply distributing the dc-to-ac power flow among the batteries according to their SoC. A simple average system model is also presented, which allows performing very fast system simulations over long periods of time and serves as a convenient tool to tune the compensator parameters. The satisfactory performance of the proposed system configuration and control, which can be applied with any number of levels and phases, has been verified through simulations and experiments in a four-level three-phase dc-ac converter fed by three Lithium-ion battery packs. The results prove the feasibility and advantages of the proposed system configuration, which can be used to implement conversion systems with different specifications combining several instances of a standard battery pack and a standard power semiconductor device.

A Survey on Capacitor Voltage Control in Neutral-Point-Clamped Multilevel Converters

“…In conventional 2-level inverters with batteries, since the battery modules are series connected, when one of the battery modules is fully discharged, all the series-connected battery modules must stop working to avoid damaging this module. The application of multilevel NPC converters to battery management is shown in Figure 19 [33]. This converter structure allows individual control of the charging/discharging of each battery module.…”

“…Moreover, a higher number of levels, which can enhance the converter voltage and current quality, will increase the difficulty to balance the capacitor voltages. Even more, some applications can benefit from operating with a capacitor voltage imbalance that must be controlled [32,33]. That is, the capacitor voltage balance issue is complex and not straightforward.…”

“…Since multiple voltage levels are available at the DC-link, it enables the implementation of a specific control for each DC-link voltage level, which may allow a more efficient control of the power flow between systems [32,33].…”

A comprehensive review on inconsistency and equalization technology of lithium‐ion battery for electric vehicles

“…Laboratory experiments were performed on a 5.3 kWh battery module and the experimental results demonstrate the proposed method has better accuracy than traditional CC method. Sergio et al 154 introduced an equalization method based on SOC estimation, and the results under different initial SOC and different battery capacities proved the feasibility of the method.…”

Predictive Control With Battery Power Sharing Scheme for Dual Open-End-Winding Induction Motor Based Four-Wheel Drive Electric Vehicle

“…In addition to normal operation, this drive train has some attractive features like lower DC bus voltage and ability to generate full torque when one of the inverters powering the front OEWIM (FM) and rear OEWIM (RM) fails. However one limitation of this drive train is the loading of these battery packs may differ due to variations in environmental conditions, manufacturing tolerances, aging, charging characteristics, internal resistance and misalignment of charging levels [19]. The weaker battery pack may get loaded more and therefore discharged faster, thus creating load imbalance and performance degradation.…”