Adaptive, robust, and fault-tolerant control strategies for grid-connected renewable energy systems
| dc.contributor.author | Nkhabu, Tsitso | |
| dc.contributor.supervisor | Makhele, Molefe | |
| dc.contributor.supervisor | Mokeke, Sebota | |
| dc.date.accessioned | 2026-06-15T09:05:44Z | |
| dc.date.available | 2026-06-15T09:05:44Z | |
| dc.date.issued | 2024 | |
| dc.description.abstract | Lesotho is currently facing a power generation-demand imbalance. The 2023/24 annual report by the Lesotho Electricity and Water Authority highlights a peak demand of 222.12 MW, which is nearly three times the country’s installed generation capacity of 74.7 MW. Consequently, the nation relies on costly power imports from Mozambique and South Africa to cover the shortfall. To address this issue, Lesotho plans to integrate renewable energy sources, specifically wind and solar, into its national grid. However, integrating these low-inertia and intermittent renewable power sources introduces grid stability challenges, as they are vulnerable to disturbances like load changes or grid faults. This research focused on designing control strategies capable of not only adjusting system voltage to accommodate uncertainties from power system dynamics, internal changes, and external disturbances but also stabilizing the system under small disturbances. The analysis was conducted on a grid-connected 38 MW wind power plant, using five control strategies: Constant Voltage (Const. V), Constant Reactive Power (Const. Q), Constant Power Factor (Const. cosɸ), Voltage Droop based on Reactive Power (voltage Q-droop), and voltage droop based on reactive power in the q-axis (voltage Iq-droop). These strategies were evaluated for their adaptability, robustness, and fault tolerance under two operational scenarios: variations in wind speed and fluctuations in the Point of Connection (POC) bus voltage. With a three-phase short circuit created and cleared on the high voltage (HV) bus bar, all control strategies are within a 5 % voltage deviation upon service restoration and fault clearance within a period of 0.015 seconds. A Supervisory Control and Data Acquisition (SCADA) system was designed for the monitoring and control of the wind power plant. Determined from the closeness of the HV bus voltage to the POC voltage, the most adaptive control strategy is used for each operation scenario, taking into account the wind speed as well as the POC voltage. It was observed that the evaluation by the SCADA system is consistent with the result obtained from the DIgSILENT PowerFactory software. For further exploration, research is recommended for the implementation of Artificial Neural Networks (ANNs) in machine learning to accommodate any wind speed and POC voltage levels for the control strategies under investigation. | |
| dc.description.sponsorship | National Manpower Development Secretariat | |
| dc.identifier.uri | https://hdl.handle.net/20.500.14155/2323 | |
| dc.language.iso | en | |
| dc.publisher | National University of Lesotho | |
| dc.title | Adaptive, robust, and fault-tolerant control strategies for grid-connected renewable energy systems | |
| dc.title.alternative | A condition monitoring approach |