Automatic Phase Shift Method for Islanding Detection of Grid-Connected Photovoltaic Inverters

Abstract

The traditional frequency-shift methods for islanding detection of grid-connected PV inverters-the active frequency drift method and the slip-mode frequency-shift method-become ineffective under certain paralleled RLC loads. The automatic phase-shift method is proposed in this paper to alleviate this problem. The method is based on the phase shift of the sinusoidal inverter output current. When the utility malfunctions, the phase-shift algorithm keeps the frequency of the inverter terminal voltage deviating until the protection circuit is triggered. Simulation and experiments are performed for verification.

Problems in the Classic Frequency Shift Islanding Detection Methods Applied to Energy Storage Converters and a Coping Strategy

“…As shown in Fig. 2, if θ con is slightly perturbed by implementing the classic methods, there is dθ c /dθ con > 0 According to (6), the following relationship is required.…”

“…The active methods have received more attention due to their advantages in expense and performance. Two famous ones are Sandia Frequency Shift (SFS) and Slip-Mode Frequency Shift (SMS), which belong to frequency shift methods and have been the classic active islanding detection methods up to the present day [1]- [6]. In addition, [7] and [8] proposed two methods based on the relationships between reactive power and frequency; [9] and [10] added a reactive power perturbation on the basis of SMS and SFS; [11] proposed a method based on a relationship between active power and voltage; [12] proposed the concept of perturbing reactive current, and [13]- [15] realized and tested it.…”

An Improved Frequency Measurement Method from the Digital PLL Structure for Single-Phase Grid-Connected PV Applications

“…In addition, this information is used to generate the PV inverter controller command, such as the anti-islanding function and the Active Frequency Drift (AFD) method [10][11][12]14]. This section discusses both the conventional PLL technique and the proposed one to calculate the line frequency.…”

“…To obtain grid synchronization between the grid voltage and the inverter output current, it is very important to obtain grid voltage information, such as the phase, frequency, and magnitude [3][4][5][6][7][8][9]. The frequency measurement, used in the PV inverter controller, is especially important, since it plays a key role in the inverter current command, such as the anti-islanding function [10][11][12][13][14][15].…”

Education in the Sustainable Energy Based on Simulation and Laboratory Innovation: A Case Study

“…MPPT block will regulate the duty cycle of the DC/DC converter by measuring the terminal voltage and current. The research on PV power system is mostly focused on the PV modeling [8], converter topology [9], MPPT control [10], and others [11], [12]. The PV modelling, boost converter and MPPT control are discussed here to show the effectiveness of simulation and laboratories in the sustainable energy education.…”