A Capacitively Level Shifted Fast Cell-to-Cell Battery Voltage Equalizer

Battery voltage equalizer circuit is an essential part of battery-based storage management system. It makes the voltages of series connected batteries equal to avoid overcharging and over-discharging In this work, a fast cell-to-cell voltage equalizer topology is proposed. The equalizer has a modular structure consisting of one power converter leg for each battery. Capacitors are used to level shift voltage in order to provide capacitive isolation among the converter legs. Converter legs are modulated with sine-triangle modulation and power flow is controlled by phases of these modulation signals. This equalizer can transfer charge among multiple batteries in a string simultaneously or selectively. This topology has been theoretically analyzed and experimentally verified with a prototype

Battery impedance spectroscopy using bidirectional grid connected converter

Battery impedance can provide valuable insight into the condition of the battery. Commercially available impedance measurement instruments are expensive. Hence their direct use in a battery management system is not justifiable. In this work, a 3-kW bi-directional converter for charging and discharging a battery bank has been implemented with the capability of impedance measurement. The converter is grid connected and controlled to operate at unity power factor. Additional requirements on filter design and control structure of battery converter for impedance measurement are discussed. An algorithm has been developed to measure impedance by frequency sweep, avoiding transients. The measured impedance has been compared to that from a commercially available impedance measurement equipment and is shown to have a good match

High Resolution Converter for Battery Impedance Spectroscopy

Monitoring the condition of battery is beneficial for many applications. Internal impedance of the battery can be used to monitor battery health. The power converter for interfacing the battery bank, can be used to measure battery impedance instead of using any dedicated commercial equipment, thus reducing system cost significantly. However, the power converter has some additional requirements in terms of control and power circuit, to be able to measure battery impedance. This work analyzes the power circuit requirements and describes possible methods to meet them. These additional measures are necessary when power level is medium or high. Advantages and disadvantages of each method are discussed. Among the suggested methods, the in-built PLL of FPGA is used to enhance PWM resolution along with an interleaved converter circuit approach is used to successfully measure battery impedance with a 3 kW converter

High-Resolution Converter for Battery Impedance Spectroscopy

Monitoring the condition of a battery is beneficial in many applications. The internal impedance of the battery can be used to monitor battery health. The power converter for interfacing the battery bank can be used to measure battery impedance instead of using any dedicated commercial equipment, thus reducing system cost significantly. However, the power converter has some additional requirements in terms of control and power circuit to be able to measure battery impedance. This work analyzes the power circuit requirements and describes possible methods to meet them. These additional measures are necessary when the power level is medium or high. Advantages and disadvantages of each method are discussed. Among the suggested methods, the in-built phase-locked loop of field programmable gate array for enhancing pulse-width modulation (PWM) resolution and an interleaved PWM converter circuit approach are used to successfully measure battery impedance with a 3 kW converter. Requirements for the measurement circuit are also discussed and a suitable measurement circuit is proposed