Journal of Modern Power Systems and Clean Energy

ISSN 2196-5625 CN 32-1884/TK

Power and Voltage Control Based on DC Offset Injection for Bipolar Low-voltage DC Distribution System
Author:
Affiliation:

1. key Laboratory of Control of Power Transmission and Conversion of Ministry of Education, Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2. School of Electronic and Electrical Engineering, Shanghai University of Engineering Science, Shanghai, China
3. School of Mechatronic Systems Engineering, Simon Fraser University, Surrey, BC, Canada

Fund Project:

This work was supported by the National Natural Science Foundation of China (No. 51877136), the Shanghai Committee of Science and Technology (No. 19DZ1205403), and the Inner Mongolia Autonomous Region Committee of Science and Technology (No. 2020GG0299).

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    Abstract:

    The bipolar low-voltage DC (LVDC) distribution system has become a prospective solution to better integration of renewables and improvement of system efficiency and reliability. However, it also faces the challenge of power and voltage imbalance between two poles. To solve this problem, an interface converter with bipolar asymmetrical operating capabilities is applied in this paper. The steady-state models of the bipolar LVDC distribution system equipped with this interface converter in the grid-connected mode and off-grid mode are analyzed. A control scheme based on DC offset injection at the secondary side of the interface converter is proposed, enabling the bipolar LVDC distribution system to realize the unbalanced power transfer between two poles in the grid-connected mode and maintain the inherent- pole voltage balance in the off-grid mode. Furthermore, this paper also proposes a primary-side DC offset injection control scheme according to the analysis of the magnetic circuit model, which can eliminate the DC bias flux caused by the secondary-side DC offset. Thereby, the potential core magnetic saturation and overcurrent issues can be prevented, ensuring the safety of the interface converter and distribution system. Detailed simulations based on the proposed control scheme are conducted to validate the function of power and voltage balance under the operation conditions of different DC loads.

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History
  • Received:February 15,2022
  • Revised:June 12,2022
  • Adopted:
  • Online: September 20,2023
  • Published: