Improved DC-Link Voltage Regulation Strategy for Grid-Connected Converters

In this article, an improved dc-link voltage regulation strategy is proposed for grid-connected converters applied in dc microgrids. For the inner loop of the grid-connected converter, a voltage modulated direct power control is employed to obtain two second-order linear time-invariant systems, which guarantees that the closed-loop system is globally exponentially stable. For the outer loop, a sliding mode control strategy with a load current sensor is employed to maintain a constant dc-link voltage even in the presence of constant power loads at the dc-side, which adversely affect the system stability. Furthermore, an observer for the dc-link current is designed to remove the dc current sensor at the same time improving the reliability and decreasing the cost. From both simulation and experimental results obtained from a 15-kVA prototype setup, the proposed method is demonstrated to improve the transient performance of the system and has robustness properties to handle parameter mismatches compared with the input-output linearization method

Greening the design brief

Front End Innovation is a hot research topic, but there is still little research done on its relationship to design for sustainability. This paper explores the challenges of integrating environmental sustainability in this early stages of an innovation process and the design brief. The study is based on a content analysis of 35 design briefs from Belgian SMEs and multinationals, and a practitioners session with representatives from 14 Belgian companies. This results indicate a limited uptake of sustainability in Belgian design briefs. Furthermore, it argues that the use of certain strategies, such as front-loading, pushing sustainability upstream in the briefing process and sustainability opportunity identification in the front end, could help in greening the design brief