A NEW CONTROL STRATEGY OF AN OFFSHORE INTEGRATED MMC MULTI-TERMINAL HVDC SYSTEM
Author’s Name : G Vijay | K Vijay | M L Dwarakanand
Volume 04 Issue 04 Year 2017 ISSN No: 2349-2503 Page no: 12-17
The modular multilevel converter (MMC) provides promising development for high-voltage direct current (HVDC) applications, including multi terminal HVDC (MTDC) and renewable energy integration. This paper, considering an offshore wind farm (OWF) integrated MMC MTDC system, investigates its start-up process with three main developments: 1) it further develops the mathematical model of MTDC with active networks and proposes a hierarchical start-up control scheme; 2) for the terminal which connects the OWF, it proposes a reduced dc voltage control scheme of mitigating the current surges with de-blocking the converter at zero voltage difference on sub modules (SMs) and proposes an overall sequential start-up control scheme for the offshore integrated MTDC; and 3) it analyzes and compares different start-up control schemes. To evaluate the proposed sequential start-up control scheme, an offshore MMC HVDC system is established on the RTDS. The simulation results verify effectiveness of the proposed scheme on the MMC MTDC system with two control paradigms, i.e., master–slave control and droop control, respectively. In comparison with different start-up control schemes, the superiority of the mitigation of voltage spikes and current surges are shown using the proposed scheme with less complexity and easier implementation.
Droop Control, Master–Slave Control, Modular Multilevel Converter (MMC), Multi-Terminal HVDC (MTDC), Offshore Wind Farm (OWF), Sequential Start-up Control
- B. Anderson and C. D. Barker, “A new era in HVDC?,” Inst. Elect. Eng. Rev., vol. 46, no. 2, pp. 33–39, Mar. 2000.
- J. Dorn, H. Huang, and D. Retzmann, “A new multilevel voltage sourced converter topology for HVDC applications,” in Proc. CIGRE Session, Paris, France, 2008, pp. 1–8.
- N. Flourentzou, V. Agelidis, and G. Demetriades, “VSC-based HVDC power transmission systems: An overview,” IEEE Trans. Power Electron., vol. 24, no. 3, pp. 592–602, Mar. 2009.
- H. Wang, G. Tang, Z. He, and J. Yang, “Efficient grounding for modular multilevel HVDC converters (MMC) on the AC side,” IEEE Trans. Power Del., vol. 29, no. 3, pp. 1262–1272, Jun. 2014.
- G. Bathurst and P. Bordignan, “Delivery of the Nan’ao multi terminal VSC-HVDC system,” in Proc. IET 11th Int. Conf. AC DC Power Transmission, Feb. 2015, pp. 1–6.
- CIGRE Working Group B4.52, “Feasibility of HVDC grids,” CIGRE Technical Brochure. Paris, Apr. 2013.