Design of a High Performance Phase-Locked Loop With DC Offset Rejection Capability Under Adverse Grid Condition

Abstract

In the new energy grid-connected power generation system, accurately extracting the grid synchronization signals such as the frequency, phase and amplitude of the grid voltage is the basis for effective control. Aiming at the requirements for detecting grid synchronization signals under unbalanced, harmonics and DC offset voltage mixed conditions, a dual second-order complex coefficient filter with DC offset rejection capability (DSOCCF dc) is proposed, combining the approach of moving average filter (MAF), a novel hybrid filter in dq-frame is designed and on the basis of this design a new synchronous reference frame phase locked loop (SRF-PLL) design approach based on the hybrid filter is proposed. The proposed approach employs moving average filter (MAF) to block the high-frequency harmonics in the grid voltage, and uses DSOCCF dc to separate the fundamental frequency positive and negative sequence and reject DC offset. It can accurately extract the synchronization information of the grid fundamental frequency positive sequence. After simulation and experiment verification, it can be confirmed that the proposed PLL can quickly and accurately lock the properties of the grid voltage under adverse grid condition, and also have high detection accuracy and strong robustness to frequency fluctuations. INDEX TERMS Dual second-order complex coefficient filter (DSOCCF), harmonic, phase-locked loop (PLL), dc offset, moving average filter (MAF).

Nonlinear Self-Synchronizing Current Control for Grid-Connected Photovoltaic Inverters

“…Finally, the dynamic equation of the DC-link capacitor voltage for the PV inverter system in the γδ estimated reference frame is obtained by substituting ( 13) into (5) as shown in (14):…”

“…Taking the time derivative of ( 16), and pre-multiplying it by C, and using the DC-link dynamic from (14) as well as the assumption cos θ ≈ 1, the open loop error dynamic of the DC-link voltage can be obtained as…”

“…The main method that is used in the literature for this purpose is a Phase Locked Loop (PLL). Moreover, the grid's information that is extracted from PLLs is used in the coordinate transformation in three-phase systems [12][13][14]. A PLL system is mainly integrated with the primary current control scheme as an outer loop, thus creating a cascaded control system [13,15].…”

Modified Second Order Generalized Integrator-frequency Locked Loop Grid Synchronization for Single Phase Grid tied System Tuning and Experimentation Assessment

“…However, these phase detection approches suffer from a sluggish dynamic performance [13][14][15]. These approaches have the potential to increase dynamic performance while overcoming the drawbacks of conventional low-pass filters [9][10][11][12][13][14][15][16]. However, selecting and calculating the sliding window width is time-consuming [15,16].…”

“…These approaches have the potential to increase dynamic performance while overcoming the drawbacks of conventional low-pass filters [9][10][11][12][13][14][15][16]. However, selecting and calculating the sliding window width is time-consuming [15,16]. Thus, a modified SOGI-FLL (MSOGI-FLL) for single-phase systems is suggested to reduce frequency estimation errors caused by DC quantity and other grid irregularities (e.g.…”