|Kirill Rykov, M.Sc||PhD student|
|dr. J.L. Duarte||Co-promotor|
|Prof. dr. E.A. Lomonova, M.Sc.||First promotor|
The present use of alternating current (AC) power grids within commercial buildings is not only inefficient but also requires significant upfront investment. Furthermore, it brings about additional power losses in rectifier and inverter electronics for equipment that ultimately requires direct current (DC). These drawbacks of AC power grids can be substantially reduced by changing the electricity distribution in buildings to a mixture of AC and DC sources (Fig. 1). A 380 V DC power grid enables the highest efficiency in building appliances such as heating, ventilation and air conditioning and lighting systems by eliminating the need for local rectifiers and power factor correction circuits. The objectives of the ENIAC JU project DCC+G therefore include the development of novel semiconductor power devices, their application demonstrating the efficient use of electric power in buildings by means of DC power grid technology and validation of such installations in commercial building environments. European industry has not yet started any action in this area. By addressing the topic of DC distribution in commercial buildings DCC+G will place Europe in the lead in this competitive market.
Low-voltage DC-grids (Fig. 2) with up to 1500 V DC are conceived as an enabling technology to integrate (sustainable) electricity sources, energy storage devices and a variety of loads in an efficient way. The system design and integration require a variability of operating conditions and, therefore, system stability issues may arise from dynamical interactions among multiple components, which are normally designed to meet their own stability requirements. As the result, after the system integration, interactions among modules can lead to instabilities in the DC-grid.
When including the impact of the control algorithms of the individual power processing converters, the processing time for obtaining meaningful results with standard simulation tools, like MatLab/Simulink or LTSpice, is prohibitive. The approach focuses on the forecast of voltage instability at each point of common coupling in the DC network. For this purpose an impedance identification technique is applied that subsequently enables for a relatively simple and effective data analysis (Fig. 3) using such control engineering theory techniques as the Nyquist Stability Criterion and Bode Plots analysis.
The resulting software tool is supposed to provide essential information for system designers to consider different load scenarios and the extension of existing small-scale grids with a considerable number of sources and loads