Kozhushko Y. Power Converters of Hybrid Energy Storage Systems for Pulsed Load Applications

The vast majority of portable devices and systems have complicated and nonlinear power consumption characteristics. The power supplies of these devices and systems, as well as the energy storage of the Microgrid and wind or solar power generation, have to provide average and peak load power, required weight and size, high energy efficiency. Various battery types are typically utilized in these power supply systems due to the high energy density of the cell. However, the high peak load current that is significantly greater than the nominal battery discharge current could lead to battery life cycle reducing and deteriorating cell characteristics. The hybridization of high power density storage and high energy density storage could be an effective solution to the problem of power supply portable devices and energy storage in Microgrid, solar and wind energy systems. Thus, the implementation of hybrid energy storage systems based on batteries and supercapacitors for self-contained power supplies and portable systems is becoming a new promising research field in recent years. Another perspective area of battery supercapacitor energy storage application could be power supplies of a micro resistance welding equipment, that also have pulsed power consumption. Energy storage that is simultaneously characterized by high power and energy density is required for micro resistance welding power supplies based on capacitive discharge topology. Auxiliary DC-DC power converters are used for energy distribution between battery and supercapacitor. This work focuses on the DC-DC converter of hybrid energy storage that is used in a system with pulsed current consumption on the example of welding current for micro resistance welding technology. Novelty of the obtained results. The topology of a battery supercapacitor energy storage has been improved by means of a DC-DC converter, which allows extending the functionality of such energy storage in systems with pulsed load current consumption. The mathematical model of a battery supercapacitor hybrid energy storage with a DC-DC converter that considers the components parasitic parameters and variations of the component parameters within the tolerance region has been proposed. The simplified mathematical model of the battery supercapacitor energy storage with DC-DC converter, that due to reducing the number of passive components of the topology allows reducing differential equations system order and simplifies the analysis of the system accordingly. The method of regulator synthesis based on Kharitonov's method, which considered the tolerance parameters of the components and allows to analyze the stability of the system in a certain range of allowable values of the model parameters has been improved. The voltage equalization system of the supercapacitor module cell of hybrid energy storage, that due to utilizing a DC converter allows providing the necessary values of the accuracy of cells voltage equalization of the module during pulse current consumption has been proposed. The practical importance. The theoretical results could be practically applicable. The proposed prototype of the hybrid energy storage system with a DC-DC converter is experimentally verified. As a result of the work, a schematic of the DC-DC converter that is applied for energy distribution between battery and supercapacitor is proposed. The DC-DC converter allows extending the functionality of such hybrid energy storages, which is used in systems with high current pulse load. A microprocessor control system of the DC-DC converter for hybrid energy storage is designed. The proposed control system allows ensuring the uncertainty of the supercapacitor voltage regulation is not worse than 5% and the battery discharges current regulation at the nominal value with uncertainty not greater than 15% during the supercapacitor charging process and consumption the pulse load current.