Advanced controller design of solar energy integrated modular multilevel converter based VSC-HVDC system

Industrialization and technological advancement have raised the increase in power demand all around the world. Due to limited reserve of fossil fuels, it is urgent to investigate alternative energy resources and develop new methodology for harvesting energy from renewable sources. Among different renewable sources, solar is the fastest growing and most promising for generating electric power in Saudi Arabia due to its cheap abundance land and high radiation of sunlight. Integration of intermittent solar energy requires complicated control techniques. Traditional maximum power point tracking (MPPT) of solar energy suffers from oscillation around the optimum power point. Besides, fault ride through (FRT) capability and transient stability are major concerns of modular multilevel converter (MMC) based voltage source converter-high voltage direct current (VSC-HVDC) system. However, according to grid code requirements, MMC-VSC-HVDC should stay connected and continue its operation during grid side fault. Conventional PLL unable to track grid angle during unbalanced fault, which in turn produces oscillation on the DC link voltage and distortion of AC side current. In this project, advanced controller for MMC based VSC-HVDC system for solar energy integration is proposed employing enhanced PLL and MPPT techniques. This controller will improve MMC submodule voltage balancing and circulating current problems. The proposed work will also improve transient stability of the system during all type of balance and unbalanced solid faults. The VSC will remain connected throughout the fault duration and fulfill the grid code requirements. The work in this project entails four main phases. In the first phase, a comprehensive literature review on MMC and the latest techniques to control VSC-HVDC system with solar energy will be conducted. In the second phase, MMC based VSC-HVDC system modeling will be developed and a novel control strategy that can improve transient stability and FRT capability of the system will be proposed. The third phase of the project will focus on developing the simulation codes and examining the system performance under different disturbances. The fourth phase of the project will focus on experimental validation of the proposed controller with real time hardware in loop (RTHIL) setup based on RTDS and real-time board for controller implementation. Such setup will help also in building the research capacity for further utilization in KFUPM. The last phase will be dedicated to comparisons, discussions, and conclusions. In addition, the developed prototype system will help in building research capacity in the area of renewable energy and MMC based VSC-HVDC, which is of major importance in the Kingdom of Saudi Arabia 2030 vision in view of the Ministry of Energy ambitious plan of integrating about 40 GW of PV systems by 2030. The project will be completed within 30 calendar months at a total cost of 75,000 USD, approximately.