Decentralized Frequency and DC-Voltage Deviation Control in Multi-Terminal HVDC (MTDC) Grids with High Penetration of Renewable Sources

In the AC surrounded MTDC (AC-MTDC) grids, Frequency and DC-Voltage Deviation (FDVD) control are decisive for the system stability, and reliability. Accomplishing it through the decentralized manner while reducing interaction between droop controls is more exigent. To address this problem, FDVD based Adaptive Droop Control (FDVD-ADC) has been proposed in this paper. It adaptively changes Grid Side Voltage Source Converters (GS-VSC's), and Renewable Source side Voltage Source Converters (RS-VSCs) say Wind Farm VSC (WF-VSC) or Solar Farms VSC (SF-VSC) droop values based upon the deviation in frequency, and DC-voltage in the AC-MTDC grid. With the proposed method, renewable sources (like solar and wind farms) are also utilized to reduce FDVD in the AC-MTDC grid. To extract this support, these bulk solar and wind farms are operated in the Derated Mode of Operation (DMO). The simulation of the proposed method has been implemented on the CIGRE B4 DC benchmark model integrated into the two-area power system in PSCAD/EMTDC software. The efficacy of the proposed methodology is validated by comparing the traditional double droop control <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(PV^{2}F)$</tex> with the proposed method.