A Robust and Less-Complex Phase-Locked Loop Algorithm Immune to Electricity Grid Disturbances for RES Applications

The increasing penetration of renewables requires advanced control algorithms to enable accurate control of the grid side converter (GSC) of renewable systems. The control of GSC mainly depends on the fast and accurate estimation of grid voltage phase angle and frequency under adverse grid conditions. Various grid disturbances occur on electricity grids, however, those that require special attention are harmonics, interharmonics and DC offset. Typically, a Phase-locked Loop (PLL) is used to obtain the grid voltage information. When designing a GSC control algorithm the accurate and proper design as well as the computational complexity, are important elements for the accurate real-time control. For real-time PV systems, embedded microcontrollers have limited computational resources and thus their effective utilization is critical. This paper proposes an advanced less-complex disturbance rejection PLL (LCDRPLL) that offers improved performance with reduced complexity. The proposed PLL is equipped with advanced features such as immunity to grid voltage unbalance, presence of harmonics, interharmonics and DC offset. More importantly, its computational complexity is very low. Experimental and simulation results are provided to justify the performance and complexity of proposed LCDRPLL.