Control of Islanded and grid-connected DC grids with embedded solar photovoltaic energy

• Main Author: Hein, Wai Yan
• Other Authors: Josep Pou
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Engineering; Power electronics; Solar photovoltaic systems; Battery energy storage systems; DC microgrids; PV algorithms; Renewable energy systems; Battery lifetime extension; PV power smoothing; Selective harmonic elimination; Power system quality and reliability
• Online Access: https://hdl.handle.net/10356/182932
• Institution: Nanyang Technological University

Clean energy generation from photovoltaic (PV) systems is rapidly increasing due to environmental concerns, making dc grids more appealing than traditional ac networks. This is due to their compatibility with PV systems, battery energy storage systems (BESSs), and modern power electronic loads. However, PV power generation is inconsistent due to intermittent environmental conditions. To maintain dc grid reliability and stability, BESSs are aggressively used to manage power imbalances between generation and consumption, which can lead to operational stress and battery degradation, especially during islanded operations. This thesis unveils new coordinated control strategies for dc grids with PV generators and BESSs to reduce the BESS usage and extend its lifetime. Additionally, a PV power ramp rate control strategy with a small BESS is introduced to smooth the PV power injection into the grid. To enhance the power quality and reliability of both dc and ac networks, a new modulation strategy for inverters, which simultaneously addresses dc current and ac voltage harmonics, is proposed. These strategies are validated through simulation and experiments.