Three-phase phase-locked loop synchronization algorithms for grid-connected renewable energy systems: A review

Abstract

The increasing penetration of distributed renewable energy sources (RES) requires appropriate control techniques in order to remain interconnected and contribute in a proper way to the overall grid stability, whenever disturbances occur. In addition, the disconnection of RES due to synchronization problems must be avoided as this may result in penalties and loss of energy generation to RES operators. The control of RES mainly depends on the synchronization algorithm, which should be fast and accurately detect the grid voltage status (e.g., phase, amplitude, and frequency). Typically, phase-locked loop (PLL) synchronization techniques are used for the grid voltage monitoring. The design and performance of PLL directly affect the dynamics of the RES grid side converter (GSC). This paper presents the characteristics, design guidelines and features of advanced state-of-the-art PLL-based synchronization algorithms under normal, abnormal and harmonically-distorted grid conditions. Experimental tests on the selected PLL methods under different grid conditions are presented, followed by a comparative benchmarking and selection guide. Finally, corresponding PLL tuning procedures are discussed.

Benchmarking of phase lock loop based synchronization algorithms for grid-tied inverter

“…All the tested algorithms have undamped oscillation in frequency estimation, although magnitude of this oscillation is not large. Similar conclusion is drawn in [9]. Step change in the grid voltage frequency is the fourth test.…”

“…Both MAF and EPMAF type 2 PLL have rejected disturbances in control loop after one window length. Testing on harmonics conducted in [9] provided similar results.…”

“…This is expected behaviour since it cannot effectively suppress inverse sequence voltage disturbances. If the previous results are compared to the ones from [9], it can be concluded that all voltage sags that induce inverse voltage component result in undamped oscillations in SRF-PLL's frequency estimation.…”

“…EPMAF-PLL type 2 showed best frequency change tracking ability. All algorithms in frequency step change test have similar settling time to each other and some are substantially different than in [9], due to the fact that all controllers in these tests are tuned with the same natural frequency and damping ratio.…”

Diversifying the Role of Distributed Generation Grid-Side Converters for Improving the Power Quality of Distribution Networks Using Advanced Control Techniques

“…A filter-based controller enabling the injection of only positive sequence current under grid voltage harmonics is presented in [31]. The injected currents, however, suffer from slow dynamic response due to the presence of filter in the control path [17,32,33]. All above mentioned controllers, do not allow the "on-purpose" injection of harmonic currents, necessary for improving the grid power quality by providing non-linear harmonic currents through the GSC of the RES.…”