## What is/are Double Synchronous?

Double Synchronous - This paper provides virtual inertia and mechanical power-based double synchronous controller (DSC) for power converters based on the dand q-components of the converter current to assure the stable operation of the grid with the penetration of large-scale renewable energy resources (RERs).^{[1]}In Stage III, the IIRES sequence currents are controlled in the double synchronous reference frame to track the reference angle.

^{[2]}As the inverter detects the voltage unbalance at its terminal, the proposed control algorithm calculates the compensation reference currents based on the double synchronous reference frame (DSRF) analysis of the PV terminal voltage.

^{[3]}It contains a microscopic and macroscopic view of the entire system and an analytic description in a double synchronous reference frame.

^{[4]}

## synchronous reference frame

The simulation results show that the proposed novel NDSRF technique is superior over existing single synchronous reference frame (SSRF) and decoupled double synchronous reference frame (DDSRF) transformation techniques, in terms of less harmonic distortion for MMC controller under the background harmonics condition.^{[1]}In this study, synchronous reference frame-PLL (SRF-PLL) and decoupled double synchronous reference frame-PLL (DDSRF-PLL) which are mostly used, state-of-arts and effective PLL algorithms are analyzed by modeling in grid synchronization applications.

^{[2]}The performance of five different PLL techniques: an abc Reference Frame PLL, a Stationary Reference Frame PLL (αβ-PLL), a Synchronous Reference Frame PLL (dq-PLL), a Voltage Reforming Synchronous Reference Frame PLL (VRSR-PLL), a Decoupled Double Synchronous Reference Frame PLL (DDSRF-LL); are analyzed in this paper under three grid voltage conditions: a set of three-phase balanced voltages, a set of three-phase unbalanced voltages in magnitudes and a set of three-phase unbalanced voltages in magnitudes and phases.

^{[3]}The reference scenario is compared firstly to the reaction of the model with the same synchronous reference frame PLL combined with a low-pass filter and secondly to the reaction of the model with a decoupled double synchronous reference frame PLL.

^{[4]}

## Decoupled Double Synchronous

This paper suggests an innovative point of common coupling (PCC) voltage controller in Decoupled Double Synchronous Reference Frame (DDSRF) to compensate for an unbalanced PCC voltage and reduce the oscillating couple using STATCOM.^{[1]}The presented control algorithm relies on the basic principle of the decoupled double synchronous frame (DDSRF) based current control theory, to transfer voltage amplitude and phase-angle related information into sequential components.

^{[2]}DDSRF (Decoupled Double Synchronous Reference Frame) theory is utilized in the proposed converter for generating the reference current from the AC supply.

^{[3]}The scheme for the single-phase signal transformation is extended for transforming three-phase unbalanced sinusoids to the decoupled double synchronous reference frame.

^{[4]}Furthermore, decoupled double synchronous reference frame (DDSRF) PLL, which is a benchmark tool for unbalanced grid synchronization, is investigated for its behavior upon small disturbances.

^{[5]}The decoupled double synchronous reference frame - PLL is used for a fast and robust positive and negative voltage sequence synchronization.

^{[6]}This work is based on using the decoupled double synchronous reference frame PLL (DDSRF-PLL), and this kind of PLL has been expanded to solve its problems in the presence of harmonics and high disturbance in the input voltage.

^{[7]}, lessening current harmonics using Decoupled Double Synchronous Reference Frame (DDSRF) theory in this paper.

^{[8]}The simulation results show that the proposed novel NDSRF technique is superior over existing single synchronous reference frame (SSRF) and decoupled double synchronous reference frame (DDSRF) transformation techniques, in terms of less harmonic distortion for MMC controller under the background harmonics condition.

^{[9]}In this study, synchronous reference frame-PLL (SRF-PLL) and decoupled double synchronous reference frame-PLL (DDSRF-PLL) which are mostly used, state-of-arts and effective PLL algorithms are analyzed by modeling in grid synchronization applications.

^{[10]}The performance of five different PLL techniques: an abc Reference Frame PLL, a Stationary Reference Frame PLL (αβ-PLL), a Synchronous Reference Frame PLL (dq-PLL), a Voltage Reforming Synchronous Reference Frame PLL (VRSR-PLL), a Decoupled Double Synchronous Reference Frame PLL (DDSRF-LL); are analyzed in this paper under three grid voltage conditions: a set of three-phase balanced voltages, a set of three-phase unbalanced voltages in magnitudes and a set of three-phase unbalanced voltages in magnitudes and phases.

^{[11]}That applies to the positive as well as negative sequence components, hence a Decoupled Double Synchronous Reference Frame - Phase-Locked-Loop (DDSRF-PLL) and Current Control (DDSRF-CC) are implemented.

^{[12]}Decoupled double synchronous reference frame software phase lock loop (DDSRF-SPLL) is used to synchronize the grid-connected power converter with the utility voltages under unbalanced load conditions.

^{[13]}, lessening current harmonics using Decoupled Double Synchronous Reference Frame (DDSRF) theory in this paper.

^{[14]}The reference scenario is compared firstly to the reaction of the model with the same synchronous reference frame PLL combined with a low-pass filter and secondly to the reaction of the model with a decoupled double synchronous reference frame PLL.

^{[15]}the method of Decoupled Double Synchronous Reference Frame Phase-Locked Loop(DDSRF-PLL) is studied.

^{[16]}This study suggests a phase-locked loop (PLL), decoupled double synchronous reference frame (ddsrfPLL) for synchronization of grid connected inverters in unbalanced grid and variable frequency conditions.

^{[17]}

## Decouple Double Synchronous

Comparing the characteristics of the Decouple Double Synchronous Reference Frame (DDSRF)and the Delay Signal Cancellation (DSC) to decompose the positive and negative sequence line parameters, the DSC with faster dynamic response is selected for the practical application effect.^{[1]}Various control strategies are given such as stationary reference frame PLL, rotating reference frame PLL, Decouple double synchronous reference frame PLL etc.

^{[2]}

## double synchronous reference

This paper suggests an innovative point of common coupling (PCC) voltage controller in Decoupled Double Synchronous Reference Frame (DDSRF) to compensate for an unbalanced PCC voltage and reduce the oscillating couple using STATCOM.^{[1]}In addition, a double synchronous reference frame PI (DSRF-PI) controller method is adopted as the fault tolerant controller.

^{[2]}DDSRF (Decoupled Double Synchronous Reference Frame) theory is utilized in the proposed converter for generating the reference current from the AC supply.

^{[3]}The scheme for the single-phase signal transformation is extended for transforming three-phase unbalanced sinusoids to the decoupled double synchronous reference frame.

^{[4]}Comparing the characteristics of the Decouple Double Synchronous Reference Frame (DDSRF)and the Delay Signal Cancellation (DSC) to decompose the positive and negative sequence line parameters, the DSC with faster dynamic response is selected for the practical application effect.

^{[5]}This paper investigates a double synchronous reference frame-based control method to compensate unbalanced voltage, helping to properly active and reactive power-sharing.

^{[6]}The synchronous reference frame (SRF), αβ, double synchronous reference frame (DSRF), sinusoidal signal integrator (SSI), dual second-order generalized integrator (DSOGI), and enhanced PLL methods have been introduced and compared in this chapter, while the controllers of grid-connected inverters are depicted with synchronous reference frame, stationary reference frame, and natural reference frame control methods.

^{[7]}Furthermore, decoupled double synchronous reference frame (DDSRF) PLL, which is a benchmark tool for unbalanced grid synchronization, is investigated for its behavior upon small disturbances.

^{[8]}The decoupled double synchronous reference frame - PLL is used for a fast and robust positive and negative voltage sequence synchronization.

^{[9]}This work is based on using the decoupled double synchronous reference frame PLL (DDSRF-PLL), and this kind of PLL has been expanded to solve its problems in the presence of harmonics and high disturbance in the input voltage.

^{[10]}, lessening current harmonics using Decoupled Double Synchronous Reference Frame (DDSRF) theory in this paper.

^{[11]}The simulation results show that the proposed novel NDSRF technique is superior over existing single synchronous reference frame (SSRF) and decoupled double synchronous reference frame (DDSRF) transformation techniques, in terms of less harmonic distortion for MMC controller under the background harmonics condition.

^{[12]}In Stage III, the IIRES sequence currents are controlled in the double synchronous reference frame to track the reference angle.

^{[13]}As the inverter detects the voltage unbalance at its terminal, the proposed control algorithm calculates the compensation reference currents based on the double synchronous reference frame (DSRF) analysis of the PV terminal voltage.

^{[14]}In this study, synchronous reference frame-PLL (SRF-PLL) and decoupled double synchronous reference frame-PLL (DDSRF-PLL) which are mostly used, state-of-arts and effective PLL algorithms are analyzed by modeling in grid synchronization applications.

^{[15]}Various control strategies are given such as stationary reference frame PLL, rotating reference frame PLL, Decouple double synchronous reference frame PLL etc.

^{[16]}The performance of five different PLL techniques: an abc Reference Frame PLL, a Stationary Reference Frame PLL (αβ-PLL), a Synchronous Reference Frame PLL (dq-PLL), a Voltage Reforming Synchronous Reference Frame PLL (VRSR-PLL), a Decoupled Double Synchronous Reference Frame PLL (DDSRF-LL); are analyzed in this paper under three grid voltage conditions: a set of three-phase balanced voltages, a set of three-phase unbalanced voltages in magnitudes and a set of three-phase unbalanced voltages in magnitudes and phases.

^{[17]}That applies to the positive as well as negative sequence components, hence a Decoupled Double Synchronous Reference Frame - Phase-Locked-Loop (DDSRF-PLL) and Current Control (DDSRF-CC) are implemented.

^{[18]}Decoupled double synchronous reference frame software phase lock loop (DDSRF-SPLL) is used to synchronize the grid-connected power converter with the utility voltages under unbalanced load conditions.

^{[19]}, lessening current harmonics using Decoupled Double Synchronous Reference Frame (DDSRF) theory in this paper.

^{[20]}In this paper, the output impedance of a three-phase inverter based on a dual current control (also called double synchronous reference frame current control) is modelled, which includes: the current loop gain, the control delay, and the Phase-Locked Loop (PLL).

^{[21]}The reference scenario is compared firstly to the reaction of the model with the same synchronous reference frame PLL combined with a low-pass filter and secondly to the reaction of the model with a decoupled double synchronous reference frame PLL.

^{[22]}It contains a microscopic and macroscopic view of the entire system and an analytic description in a double synchronous reference frame.

^{[23]}the method of Decoupled Double Synchronous Reference Frame Phase-Locked Loop(DDSRF-PLL) is studied.

^{[24]}This study suggests a phase-locked loop (PLL), decoupled double synchronous reference frame (ddsrfPLL) for synchronization of grid connected inverters in unbalanced grid and variable frequency conditions.

^{[25]}