Li, Mingshen



PROJECT TITLE: DC Microgrid Control Technologies applied to HVDC Systems   


PhD period: 2017.01.15 – 2020.01.14.
Section: Power Electronic Systems 
Research Programmes: Microgrids
Supervisor: Josep Guerrero
Co-Supervisor: Yonghao Gui 
Contact Information

Collaborator: Hunan University, China.
Funding: Scholarship from China Scholarship Council.

ABSTRACT

Given the global changes in energy generation and transmission, flexible Multi-terminal High Voltage Direct Current (HVDC) networks have the potential to offer energy transfer from diverse and isolated generation sources, particularly offshore wind farm. Comparing with the AC grids, the DC grid has the lower impedance of DC lines, inherent inertia and faster dynamics. Consequently, a growing oscillation will be observed widely, which will cause the power quality problems in the DC system. Otherwise, many other problems such as nonlinear loads, unbalancing power, and weak AC grid etc. will also reduce the stability and reliability of HVDC system operation. However, it will not be sufficient to develop converter controls using traditional steady-state approaches.

Meanwhile, as an effective measure of accommodating distributed generation, Microgrid techniques has attracted wide attention and become more mature. Due to similar structures and operation characteristics between DC Microgrid and HVDC, the DC Microgrid techniques such as droop control, secondary control, virtual impedance etc. are available in the HVDC to improve the system performance and power quality.

The main objective of the project is to investigate the control strategies of DC Microgrid applied to HVDC systems. The project will involve:

  • Proposing the new control strategies to avoid the effect of insufficient power margin of a converter and keep a good stability for HVDC system.
  • Implementing an efficient control strategy for smoothing switching between grid-connected mode and island mode in voltage source converter (VSC).
  • Optimizing the virtual impedance control method to improve VSC’s robustness and disturbance abilities in weak AC grid.
  • Developing the experiment platform of VSC by using the proposed control strategies.


Papers

Publications in journals and conference papers may be found at VBN.