Abstract
This paper proposes an error compensation algorithm based on synchronous reference frame phase-locked loop for accurate phase estimation of the distorted three-phase voltages including asymmetrical phase voltages, harmonics, and dc offset. These errors cause undesirable periodic ripples with grid frequency in the traditional PLL and significantly degrade the overall performance of the grid-connected converters. In this paper, the effects of the errors are comprehensively analyzed in the stationary and synchronous reference frames. In particular, the errors are estimated and compensated by controlling the $\alpha $ -axis and $\beta $ -axis components in a PLL to be balanced. The proposed compensation algorithm can be implemented by some integral operations followed by simple Integral-controllers. The performance and robustness of proposed compensation technique are investigated under distorted grid conditions. The proposed technique is numerically and experimentally verified using Matlab/Simulink and Dspace1202 control board platform.
Highlights
The three-phase grid-connected converter is very important for many applications such as renewable energy conversion systems, active power filters, battery charger of electric vehicles, static VAR compensators, uninterruptible power supplies (UPSs), and energy storage systems [1]-[3]
The errors caused by the offset of the signal measurement and conditioning circuits, the harmonics, or any type of amplitude imbalances seriously influence the performance of phase-locked loop (PLL), the dynamic performance of the grid-connected converters systems may be degraded [5]
A variety of advanced synchronous reference frame-PLL (SRF-PLL) with enhanced disturbance rejection capability can be found in the literature
Summary
The three-phase grid-connected converter is very important for many applications such as renewable energy conversion systems, active power filters, battery charger of electric vehicles, static VAR compensators, uninterruptible power supplies (UPSs), and energy storage systems [1]-[3]. A novel algorithm of error compensation based on SRF-PLL is proposed for accurate phase estimation of the distorted three phase voltages. The errors are readily estimated by using integral operations for the synchronous qd-axes voltages according to the estimated phase angle followed by Integral-controllers. The proposed compensation algorithm, which is directly embedded in the SRF-PLL, enables a new concept of phase estimation under distorted grid conditions and it can be a suitable candidate to eliminate the distortion errors and improve the performance of traditional SRF-PLLs. The proposed compensation method is numerically and experimentally verified using Matlab/Simulink and Dspace1202 control board platform.
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