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Saturday, 3 March 2018

DC Electric Springs – A Technology for Stabilizing DC Power Distribution Systems

There is a growing interest in using DC power systems and microgrids for our electricity transmission and distribution, particularly with the increasing penetration of photovoltaic power systems. This paper presents an electric active suspension technology known as the DC electric springs for voltage stabilization and power quality improvement. The basic operating modes and characteristic of a DC electric spring with different types of serially-connected non-critical loads will first be introduced. Then, the various power delivery issues of the DC power systems, namely bus voltage variation, voltage droop, system fault, and harmonics, are briefly described. The operating limits of a DC electric spring in a DC power grid is studied. It is demonstrated that the aforementioned issues can be mitigated using the proposed DC electric spring technology. Experiment results are provided to verify the feasibility of the proposed technology.

1.      Smart load
2.      Distributed power systems
3.      Power electronics
4.      Electric springs
5.      DC grids
6.      Smart grid



Fig. 1. The basic configuration of DC electric springs.


Fig. 2. Enlarged experiment waveforms based on the raw data exported from the oscilloscope corresponding

Fig. 3. Enlarged experiment waveforms based on the raw data exported from the oscilloscope corresponding

In this paper, the concept of DC electric springs (ES) is firstly introduced to cope with several issues of DC power grids. The DC-ES is proposed as an active suspension system. Similar to their AC counterparts, the DC-ES can provide dynamic voltage regulation for the DC bus. The DC-ES connected in series with different types of non-critical loads to form a smart load have been analyzed and their operating modes have been identified and explained. Furthermore, the operating limits of the DC-ES under a given set of system parameters is studied, which provides quantitative analytical procedures to estimate the theoretical limits of ES. The paper provides a fundamental study on the DC-ES including the characteristics, the modes of operation, and the operating limits. The theoretical analysis and the performance of the DCES have been practically verified.
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