Grid-connected solar systems with integrated energy storage are increasingly vital to grid stability as renewable penetration increases. However, managing the dynamic interaction between variable PV generation, battery systems, and grid requirements remains technically challenging. Researchers have developed an advanced control framework that addresses these challenges through sophisticated voltage and current regulation techniques.
The proposed system uses a Sigmoid Least Logarithmic Absolute Difference (SLLAD) regulator to control the Voltage Source Converter (VSC), which interfaces the solar-storage system with the electrical grid. This control approach enables rapid response to grid conditions while minimizing steady-state errors. The system performs multiple simultaneous functions: injecting solar power to the grid, supporting voltage stability, and providing reactive power compensation during grid disturbances.
A key innovation is the dual energy storage architecture combining a battery for sustained power delivery with an ultracapacitor for fast transient response. This hybrid arrangement efficiently buffers the inherent variability of solar generation while handling sudden load changes. The battery manages longer-duration power imbalances, while the ultracapacitor responds to rapid fluctuations, improving overall system efficiency and grid compatibility.
The control strategy includes advanced grid voltage filtering using Second Order Generalized Integrator Frequency Locked Loop (SOGI-FLL) algorithms, enabling proper operation even when grid voltage is distorted by other connected equipment. This robustness is essential for reliable integration in diverse grid environments.
Validation through hardware-in-loop testing demonstrated that the system successfully meets IEEE 1547 interconnection standards, which govern how distributed resources must behave on the grid. The research confirms that advanced control strategies can enable solar-storage systems to function as active grid assets rather than passive power sources, providing voltage support, harmonic mitigation, and load balancing capabilities essential for modern grids with high renewable penetration.
