STRUCTURAL AND PARAMETRIC SYNTHESIS OF THE DC-LINK OF A HYBRID ELECTROTECHNICAL COMPLEX WITH HYDROGEN STORAGE AND A VARIABLE-FREQUENCY ELECTRIC DRIVE

Abstract

The aim of the study is to develop a reproducible approach to the structural and parametric synthesis of the DC-link of a hybrid electrotechnical complex including a photovoltaic unit, an electrolyzer, a hydrogen storage system, a fuel cell, a variable-frequency electric drive of a pumping load, and the utility grid. An explicit mathematical model of the DC-bus energy balance is used as a scientific basis, supplemented by dynamic equations for the electrolyzer and the fuel cell and by a grid-support control law. A computational experiment in MATLAB is performed for a sharp reduction in photovoltaic generation power. The measurable technical criteria are the maximum DC-link voltage deviation, recovery time, peak grid support power, and the duration of the voltage staying outside the admissible range. For the base case with a DC-link capacitance of 0.10 F and a grid support gain of 1.2 kW/V, the following results are obtained: maximum voltage deviation 5.79 V, minimum voltage 644.21 V, recovery time 0.183 s, peak grid power 17.48 kW, and zero time outside the 600–700 V range. It is established that increasing the DC-link capacitance reduces the maximum voltage deviation but increases the recovery time, whereas increasing the grid support gain decreases both the voltage deviation and the transient duration. The obtained results confirm that the parameters of the DC-link and the grid support gain must be selected jointly according to transient quality criteria.