Design and Implementation of A Three-Level Boost converter for Battery Impedance Spectroscopy

Lithium-ion batteries are the most are widely used as electrical storage device in various applications such as portable electronics, electric vehicles, Photovoltaic application, telecommunication etc due to the characteristics of the batterie such as high-power density, long cycling and high-power efficiency. Extensive condition monitoring of the battery should be implemented due to the usage of the battery so that there will be an increase in all the overall performance and expectancy. This research is focused on implementing an online condition monitoring on the Li-ion battery using a signal injection through a power converter. The implemented technique in this research is known as the Electrochemical Impedance Spectroscopy (EIS). The EIS is a widely known technique used in determining the internal impedance of a battery cell. The estimated impedance can be used to determine the state of charge (Soc) and State of health (SoH) of a battery. The EIS is used to characterize the electrochemical behaviour thereby monitoring the change in the impedance of the cell of the battery. The EIS technique is accomplished by sinusoidally injecting current at different frequencies and measuring the voltage response. A standard Frequency Response Analyser (FRA) is used as an offline test while the battery is disconnected from the Load. The limitation of this standard FRA analyser is that it is bulky and Expensive. Attempts have been made to migrate the techniques to online operations, each having their own challenges. For an online Implementation, the interfacing power converter is used for Signal injection to measure the impedance of the battery. This work explores the low current ripple advantage of a threelevel boost converter to implement EIS on lithium ion battery

A novel hybrid DC traction power supply system integrating PV and reversible converters

A novel hybrid traction power supply system (HTPSS) integrating PV and reversible converter (RC) is proposed. PV is introduced to reduce the energy cost and increase the reliability of power systems. A reversible converter can achieve multiple objectives including regenerative braking energy recovery, PV energy inverting, DC voltage regulation and power factor improvement. In this paper, the topology and operating modes of the HTPSS are first introduced. Three-level boost converter (TLBC) is employed in the PV system. A double closed-loop control scheme considering both maximum power point tracking (MPPT) and midpoint potential balancing (MPB) is recommended. The reversible converter adopts a multi-modular topology and the independent control for active power and reactive power has been achieved by a current decoupling control. According to the working characteristic of each device, a coordinated control strategy is designed, and four basic principles are given. A system simulation model containing a hybrid traction substation and a train was built, and comprehensive simulations under multi-scenario were carried out. The results show that the reversible converter can accomplish PV energy inversion, DC voltage regulation, regenerative braking energy recovery and power factor improvement, by which a high utilization rate and energy-saving effect can be obtained