Source-Side Series-Virtual-Impedance Control to Improve the Cascaded System Stability and the Dynamic Performance of Its Source Converter

• Published in: IEEE transactions on power electronics 2019-06, Vol.34 (6), p.5854-5866
• Main Authors: Zhang, Xin, Zhong, Qing-Chang, Kadirkamanathan, Visakan, He, Jinsong, Huang, Jingjing
• Format: Article
• Language: English
• Subjects: Adaptive control; Cascaded system; Control stability; Control systems; Converters; Cutoff frequency; dynamic performance; Dynamic stability; Frequency conversion; Impedance; impedance control; Input impedance; Load modeling; Performance enhancement; source-side series-virtual-impedance (SSVI); stability; Strategy; Systems stability; Thermal stability; Transfer functions; Voltage control
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2018.2867272

Instability problem is an important issue for dc/dc conversion cascaded systems (Cascaded system in short). Though most of the existing stabilization methods can stabilize the whole system very well, they may ignore their impacts on the dynamic performance of the original cascaded system. Unfortunately, these impacts are negative to some extent. Recently, an adaptive-series-virtual-impedance (ASVI) control strategy has been reported to address the above problem. It not only can stabilize the cascaded system via shaping the load input impedance, but also can reduce its impact on the original load converter. However, though the ASVI control strategy has already greatly reduced its impact on the load converter, its remaining impact is negative. To solve this problem, this paper moves the ASVI from the load side to the source side via a proposed source-side series-virtual-impedance (SSVI) control strategy for the source converter. This SSVI control strategy not only has the same stabilization function and adaptive characteristics as the ASVI control strategy, but also improves the performance of the source converter. In addition, since the SSVI control strategy is realized by changing the control block of the source converter, the performance of the load converter is not affected. Therefore, the SSVI control strategy can be treated as a supplement and expansion of the ASVI control strategy. Moreover, depending on the method of realization, the SSVI control strategy can be divided into the source stabilization methods of the cascaded system. Finally, a 100 W 48 V-32 V-24 V cascaded system has been fabricated to validate the proposed control strategy.