Decoupled Control Strategy for Electric Springs: Dual Functionality Feature

Abstract

Smart grid philosophy recommends a wide spread of residential roof-top installed grid-connected photovoltaic (PV) systems as a benchmark for renewable energy (RE) emphasis to future power generation. These systems must adopt power electronic-based converters to perform grid integration function. On the other side, concerns about voltage fluctuations, which are directly related to power system stability, have arisen from the increasing use of intermittent renewable energy sources (RES) distributed in the grid. Hence, a power electronic-based converter topology, known as Electric Spring (ES), has been developed to be additively connected in series with non-critical residential loads. It has the ability to regulate the mains voltage via reactive power compensation. In this paper, a novel control scheme is proposed for ESs operation. The presented control technique offers conventional ES a decoupled dual functionality. Besides, its inherent ability of feeder voltage regulation, the ES can, under the proposed control technique, simultaneously inject locally available PV power into the grid via the same power electronic converter. The system analysis and mathematical modeling of the proposed control scheme are demonstrated in detail. To verify the proposed technique effectiveness, both simulation and experimental investigation are carried under various bus voltage levels' cases: normal, sag, and swell. Moreover, the system performance is attested under irradiance changes. The results from simulations and experimental setup prove the applicability of the ES dual functionality even under severe disturbances.

Keywords

• Bus voltage regulation
• dual function converter
• electric spring
• maximum power point tracking
• photovoltaic
• grid interface