A lithium-ion battery has advantages such as high energy density and long calendar life, but it suffers from the risk of thermal runaway. Overcharge-induced thermal runaway accidents hold a considerable percentage. This article discovers that the slope of the dynamic impedance in the frequency band of 30–90 Hz turns positive from negative when the cell just starts to overcharge and proposes the theoretical explanation. Taking 70 Hz impedance as an example, the thermal runaway accident can be successfully avoided by cutting off the charging when the slope turns positive from negative during charging. The warning time is 580 s ahead of the thermal runaway. This feature is easy to identify and requires no complex mathematical models and parameters. Besides, the prediction method based on this feature can be conducted by using an online dynamic impedance measurement device designed by us, which is suitable for large-scale applications. Thus, the overcharge-induced thermal runaway accidents can be avoided.

Although Li-ion batteries are widely used, recent catastrophic accidents have seriously hindered their widespread application. In this study, a novel acoustic-signal-based battery fault warning and location method is proposed. This method requires only four acoustic sensors at the corners of the energy storage cabin. It captures the venting acoustic signal when a fault occurs in the cell and calculates the spatial location of the cell. The maximum spatial error is 0.1 m. Considering that the effective range of a fire-fighting facility is significantly greater than 0.1 m, such a location error is acceptable. Furthermore, a wavelet-transform-based anti-misjudgment method that ensures the reliability of the fault warning and location is proposed. Thus, a nonintrusive, timely, and effective solution to ensure the safety of the battery energy storage system is provided.

DC-DC boost converters with better performances, including improved voltage gain, efficiency, power density and reliability, are urgently needed for wide conversion range applications. In this article, a single-inductor boost converter (SLBC) with ultrahigh voltage boosting capability is proposed and analyzed. For the SLBC, low-voltage-rating MOSFET with small on-resistance can be chosen and losses of switches can be reduced owing to the lower switches voltage stress and intrinsic small duty cycle, which are conducive to enhance the system efficiency. The single inductor of the SLBC is in series with its input source, therefore, continuous input current and high power density are attainable. Moreover, the SLBC has common grounded input and output terminals, which is benefit to avoid the du/dt issues and achieve reliable output. The operational principles of steady-state mode and small-signal mode are presented to analyses the SLBC in detail. Based on these, performance comparisons with other typical converters and 250W experiment prototype are implemented to validate the feasibility and effectiveness of the SLBC.

In this paper, two inverting buck-boost converters which possess wide conversion ratios are proposed. At the proper duty cycles, the inverting buck ² -boost converter (IB2BC) achieves high step-down gain while the inverting buck-boost ² converter (IBB2C) realizes high step-up gain. Advantages of the IB2BC and the IBB2C also include fourth-order simple common-ground structures to increase the power density and operability, low components stress to decrease the corresponding losses and then to improve the system efficiency, no sudden changings on capacitors voltage to prevent the instantaneous overcurrent phenomenon. Owing to the special structures of the IB2BC and the IBB2C, their improved single-switch topologies with reduced number of switch and extensional topologies with wider conversion ratios are constructed, respectively. Operational principles and corresponding comparisons of the above mentioned buck-boost converters are deeply studied and analyzed. As the representative, the single-switch inverting buck-boost ² converter (SIBB2C) is designed and experimented in step-down/up modes for verifying the family of buck-boost converters performance.

As the promising and ideal clean energies, wind and solar energy systems are in desperate need of high‐performance DC–DC converters to realize efficient and reliable energy transformation. Conventional DC–DC converters for renewable energy systems will work at extreme duty cycles and affect the system efficiency and reliability owing to their limited voltage gains and high‐voltage stress. In this paper, by adopting the hybrid voltage multiplier cells, two enhanced quadratic boost converters (EQBCs) which are highly desirable for renewable energy applications are proposed and analyzed. The EQBCs possess super‐wide voltage gain ranges and ultra‐low voltage stress; therefore, small duty cycle conditions can be achieved and components with low‐rated voltages can be chosen to decrease system volumes and increase system efficiencies. Besides, the EQBCs possess continuous input currents, which can realize small input current ripples and avoid the serious effect of pulsating current on the input sources. What's more, stable output voltages and simple controller circuits are realized by the EQBCs because of the common grounded structures of the input terminal, the single active switch and the output terminal. Detailed principle analyses, parameter designs, performance comparisons and experimental prototypes are conducted to verify the characteristics and feasibilities of the EQBCs.

Conventional DC-DC converters for renewable energy systems work in large duty cycle conditions, which will lead to the inductor saturations and decrease the system efficiencies and stabilities. In this paper, a new fifth-order boost converter, which can work in dual operating modes when different control technologies are adopted, is proposed. To obtain a wider conversion ratio, the required duty cycle for the proposed converter with synchronous controller is smaller than 0.333 while with interleaved controller is smaller than 0.5. Also, dual modes of this converter both have lower switches voltage stress. Then, the inductor saturation issues can be avoided and the system efficiencies and stabilities can be improved. Besides, the lower topological order and simple grounded structure of this converter are benefit to reduce the modeling complexity, topology volume and system noises. Detailed analyses, comparisons and prototype are implemented to study the improved conversion ratio, efficiency and power density of the proposed converter in-depth, and to validate its feasibilities for renewable energy applications.