Power Quality Improvement of Three-Phase Grid-Tied Inverter Using Sliding Mode Controller

The implementation of sustainable energy technologies, particularly grid-connected photovoltaic (PV) systems, plays a vital role in modern power systems. Achieving stable operation and maintaining high power quality under dynamic conditions remain key challenge in this field. This paper proposes an enhanced sliding mode control (SMC) strategy, that mitigates steady-state error and improve disturbance rejection capability by modifying the sliding surface incorporating integral error dynamics and a tan-based reaching law with continuous saturation function is applied to suppress chattering, tailored for grid-tied PV systems. Unlike conventional proportional-integral (PI) controllers, which exhibit moderate dynamic response and elevated harmonic distortion during disturbances, the SMC demonstrates strong robustness against solar irradiance, fluctuations in grid voltage, short-circuit faults, and load unbalance. The proposed SMC precisely regulates grid currents, enhancing overall system performance and assuring superior power quality. In particular, under unbalanced load conditions, the PI controller produces a total harmonic distortion (THD) of 6.04%, surpassing IEEE limits. In contrast, the proposed SMC achieves a THD of 1.25%, outperforming the conventional SMC and PI, that's acceptable limit. These results emphasize the efficiency of the proposed SMC strategy in delivering faster transient response, improving grid power quality, minimizing harmonics, and positioning it as a promising solution for future PV system integration.