Control and synchronization algorithms for a grid-connected photovoltaic system under harmonic distortions, frequency variations and unbalances

Abstract

a b s t r a c tIn this paper, an implementation of the control and the synchronization algorithms for a Voltage Source Inverter used as the power conditioner for Photovoltaic renewable energy in a grid-connected structure is carried out. Its main purpose is to show, in a simple manner, the design and combined operation of the control and synchronization algorithms for attaining the proper behaviour of the Grid Inverter when the 3-phase utility grid is disturbed by voltage unbalances, frequency variations and harmonic distortions, according to power quality standards.In order to obtain a high efficiency of the system during perturbations, a Proportional Resonant controller with a Harmonic Compensator structure is designed for the control algorithm, whereas a Dual Second Order Generalized Integrator Frequency-Locked Loop (DSOGI-FLL) is used as the synchronization algorithm.In order to validate both the control and the synchronization algorithms, some simulations using MATLAB/SIMULINK from The MathWorks, Inc. are shown firstly, and secondly, some real-time digital simulations are carried out.

Control and Grid Synchronization of Two Level Voltage Source Inverter Under Temporary Voltage Unbalance

“…The topic of grid connected power electronic control has been elaborated in number of papers [25,38,45,63,75,76]. The variety both methods makes it possible to find the optimal solution for nearly every application.…”

Improvement of DSOGI PLL Synchronization Algorithm with Filter on Three-Phase Grid-connected Photovoltaic System

“…However, the voltage signal can be distorted by the unbalance grid condition. In addition, the error of the sensor can produce second-order harmonic [34]. On the three-phase utility grid, Positive Sequence Detector (PSD) based on the symmetrical component method or Fortescue theorem on [35] is used on Dual Second Order Generalized Integrator Phase Locked Loop (DSOGI PLL) synchronization algorithm [16], [36], [37].…”

“…Quadrature signals generated based on double SOGI (QSG) are used to filter and obtain quadrature signals, the signals that shift 90 o from the original signal. The transfer function of SOGI is explained by (8) and the block diagram of a quadrature signal based on SOGI (QSG) is presented in Figure 3 [34], [36], where ω' is the frequency adaptive and k is the gain of the SOGI (QSG). Then the signal obtained from DSOGI quadrature signals generator (QSG) is used as inputs on the instantaneous symmetrical components (ISC) method in the stationary reference frame (αβ).…”

“…From the Figure 3, the transfer functions of the inquadrature signals respectively suggest a behavior of band-pass filter D(s) and low-pass filter Q(s). The transfer functions of thefilters are described by (9) and (10) [34], [36].…”

“…When the value of the gain k is lower, the transient response of the SOGI to achieve on settling time becomes longer, but the immunity response of the harmonics is good and obtain better transient response. The gain k setting on 1.414 [34], [35] is a good trade-off between the harmonic rejection (for 5th and 7th harmonics) and the dynamic response is achieved, corresponding to a damping factor ζSOGI-QSG= 0.707 for second order systems [34].…”