Research on the Influence of Stray Parameters in the Circuit of the Hybrid Energy Storage
In the course of battery discharge in hybrid energy storage, overvoltage trends to appear at opposite ends of the IGBT (Insulated Gate Bipolar Transistor) when the IGBT is switched off, which is likely to cause overvoltage to damage the IGBT. To solve the problem, this paper has made analyses of the mechanism of capacitor when overvoltage caused by the IGBT failure, the stray inductance in the hybrid energy storage circuit and the inductance of switch-off current on the overvoltage. And the corresponding mathematical formula is derived. On the basis, a simulation model is established. The rational distribution and the addition of an absorption loop can reduce the peak value of overvoltage. It is found from simulations that the absorption circuit will lead to voltage oscillation in the main circuit. Aimed at this phenomenon, the design of the absorption loop is optimized. Simulations and experiments prove the proposed method to be effective.
A Novel Closed-Loop Control Method for Li-Ion Batteries Connected in Series Power Supply Based on the Time Sequences Recalculation Algorithm
The charging time of Li-ion batteries connected in series (LBCSs) power supply is the main concern in an electromagnetic propulsion system. However, the capacity loss of a Li-ion battery is inevitable due to the repetitive operation of LBCSs power supply, which leads to the decrease in the average current. Thus, the voltages of symmetrically distributed pulse capacitors of LBCSs power supply will not reach the setting value in the specified time. This paper proposes a novel closed-loop control method to solve the problem. By collecting the pulse capacitor voltage and the circuit current, the time sequences of Li-ion batteries are recalculated in real time in a closed-loop to increase the average current. The time-domain model of the circuit topology of the LBCSs power supply and an innovative closed-loop control method based on the time sequences recalculation algorithm are described first. Then, the circuit model is built in PSIM for simulation analyses. Finally, a series of experiments are conducted to confirm the effectiveness of the method on the megawatt LBCSs power supply platform. Both the simulation and experimental results validate that the proposed method not only shortens the charging time, but also increases the average current. In practical experiments, the charging time is shortened by 4.5% and the average current is increased by 4.8% using the proposed method at the capacity loss of 50 V.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.