Currently one of the promising trends in the global energy sector is the introduction of renewable energy sources (RES) into the existing grid. The use of RES can be favourable in autonomous power systems where fuel costs are high. However the stochastic nature of power generation creates a number of difficulties in maintaining the power balance. To solve this problem, it is proposed to connect a hybrid energy storage system (HESS) consisting of a battery and a supercapacitor to the load busbars. The efficiency of such HESS depends mainly on the way of its connection to the grid and the choice of control method. The article gives an overview of the existing mechanisms for controlling the power consumption of HESS.

Keywords: Renewable energy, hybrid electricity storage, power converter topology, electricity storage control strategy

The article considers the process of relaxation of fibrous material after the action of the load on it is completed. A simple model of the relaxation process is constructed in the form of an exponential function, which describes this process quite accurately. It is determined that the relaxation time estimates are robust with respect to the parameter distributions. The constructed relaxation models make it possible to estimate the magnitude of the residual relative strain corresponding to the plastic strain of the material.

Keywords: relaxation, deformation, fibrous material, robustness, Monte Carlo method, exponential model, regression

The article raises the issue of maintaining the stability of the power system, including maintaining the balance of electric power. The occurrence of power imbalance can be determined by a criterion such as frequency. The authors have proposed a method of maintaining frequency including maintaining power balance in the power system by changing voltage on electric energy consumers, a hypothesis has been set and a corresponding laboratory study has been carried out, as a result of which dependence of frequency change on voltage of some electric power receivers has been obtained. A device an automatic unloading regulation of voltage has been developed and described, which will make it possible to supplement the existing emergency control equipment.

Keywords: renewable energy sources, grid inverters, mode parameters, Clark conversions, Park conversions