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

Abstract

In renewable energy-based generation sources a phase locked loop is one of the most popular synchronization techniques. A rapid and precise grid voltage phase and frequency estimation under a wide spectrum of possible grid disturbances is its main objective. This paper compares popular grid synchronization algorithms on grid voltage anomalies. The compared algorithms are divided in three groups: without filtering, with filtering in synchronous reference frame and with filtering in stationary reference frame. The behaviour of the algorithms is tested in a laboratory, using dSpace 1103 as a platform on which the algorithms are compiled and OMICRON CMC 356 as a programmable grid voltage generator. The benchmarks conducted in this paper include voltage sags, grid voltages harmonics, DC offset and frequency step change. The obtained results show that there are significant differences in tested PLL responses for some networks disturbances.

A Novel Repetitive Control Enhanced Phase-Locked Loop for Synchronization of Three-Phase Grid-Connected Converters

“…The Laplace complex variable is denoted with p, expected fundamental frequency with ω ff , fundamental frequency correction signal with ∆ω, and the error signal (output of the inverse tangent function) with e(p). The phase-locked loop typically consists of a phase detector (PD) that generates a signal with phase error information, LF for a phase error elimination, and a frequency/phase generation block called the voltage-controlled oscillator (VCO) [5,[7][8][9][10]. The most commonly used LF is a proportional-integral (PI) controller, and in this paper, the parallel form with the proportional gain k p and the integral time constant T i was chosen.…”

“…In the events of phase jumps or voltage sags, SRF-PLL can have a high overshoot of estimated frequency that can lead to the unexpected tripping operation of RES protection, thus disconnecting the RESs from the grid [6]. Reduction of overshoot and the amplitude of oscillations with unbalanced voltage sags can be achieved with the reduction of SRF-PLL bandwidth, resulting in precise but slow synchronization [7]. The problem of unbalanced voltage is overcome by a novel cross-feedback decoupling network used for positive and negative sequence fundamental component extraction in a synchronization structure called the decoupled double synchronous reference frame PLL (DDSRF-PLL) [7,8].…”

“…Reduction of overshoot and the amplitude of oscillations with unbalanced voltage sags can be achieved with the reduction of SRF-PLL bandwidth, resulting in precise but slow synchronization [7]. The problem of unbalanced voltage is overcome by a novel cross-feedback decoupling network used for positive and negative sequence fundamental component extraction in a synchronization structure called the decoupled double synchronous reference frame PLL (DDSRF-PLL) [7,8]. Use of the moving average filter as a harmonic filter in SRF-PLL (MAF-PLL) [9] proved effective in the elimination of periodic disturbances related to voltage imbalance and harmonics, while at the same time reducing the frequency overshoot of conventional SRF-PLL.…”

“…Along with synchronous reference frame filtering, another popular group of synchronization algorithms use a stationary reference frame for specific signal extraction. The second-order generalized integrator (SOGI) acts as a quadrature sinusoidal generator using the combination of low pass filter (LPF) for harmonic filtering and orthogonal signal generation, along with the band pass filter (BPF) for harmonic filtering [7,8]. SOGI based PLLs are also advantageous for specific harmonic extraction capability, but at the cost of higher computation burden compared to previously described PLLs [8].…”

Synchronization Algorithms for Grid-connected Photovoltaic Systems under Grid Disturbances

“…All these synchronization methods give satisfactory results in normal conditions with no noise neither disturbances in grid voltages. But in real situation, different factors in the grid could cause the presence of harmonics, voltage sags, swells, unbalances, DC offset in real voltages, in [12] are presented some grid voltages disturbances that can affect the ability of the PLL to track and estimate the precise grid phase and frequency. Several research papers have been published as part of the improvement of conventional synchronization methods in order to have a better stability and fast synchronization in case of grid disturbances.…”