An Overview of Assessment Methods for Synchronization Stability of Grid-Connected Converters Under Severe Symmetrical Grid Faults

Abstract

Grid-connected converters exposed to weak grid conditions and severe fault events are at risk of losing synchronism with the external grid and neighboring converters. This predicament has led to a growing interest in analyzing the synchronization mechanism and developing models and tools for predicting the transient stability of grid-connected converters. This paper presents a thorough review of the developed methods that describe the phenomena of synchronization instability of grid-connected converters under severe symmetrical grid faults. These methods are compared where the advantages and disadvantages of each method are carefully mapped. The analytical derivations and a detailed simulation model are verified through experimental tests of three case studies. Steady-state and quasi-static analysis can determine whether a given fault condition results in a stable or unstable operating point. However, without considering the dynamics of the synchronization unit, transient stability cannot be guaranteed. By comparing the synchronization unit to a synchronous machine, the damping of the phase-locked loop is identified. For accurate stability assessment, either nonlinear phase portraits or timedomain simulations must be performed. Until this point, no direct stability assessment method is available which consider the damping effect of the synchronization unit. Therefore, additional work is needed on this field in future research.

Current Reference Generation Based on Next-Generation Grid Code Requirements of Grid-Tied Converters During Asymmetrical Faults

“…Due to this, the Dy transformer is neglected and the grid simulator is directly used to generate the asymmetrical voltage sag of interest. For a detailed description of the experimental setup used, please refer to [36]. The parameters listed in Table I is as well used for the experimental verification.…”

Transient Stability of Vdc – Q Control-Based PV Generator With Voltage Support Connected to Grid Modelled as Synchronous Machine

“…From (6), (7), it can be seen that the V pv is dependent on V s as well as d d and d q . The (6) and (7) imply that any changes in the voltage magnitude V s will be reflected in V pv as well. So, it can be concluded that monitoring V pv will be sufficient to analyze the voltage stability of SP-SM system.…”

“…The stability definitions and importance of stability analysis of power systems with high penetration of RE generators are discussed in-detail in [5]. An overview of the stability assessment methods of grid connected Voltage Source Converters (VSC) during severe faults is presented [6]. The need to develop new stability assessment methods for grid tied VSCs is also highlighted in [6].…”

“…An overview of the stability assessment methods of grid connected Voltage Source Converters (VSC) during severe faults is presented [6]. The need to develop new stability assessment methods for grid tied VSCs is also highlighted in [6]. Transient stability analysis of grid connected converters equipped with various control strategies has been reported in the recent works [7]- [16].…”

Applications of Power Electronics

“…The main aim of this Special Issue was to seek high-quality submissions that highlight and address recent breakthroughs over the whole range of emerging applications of power electronics, the harmonic and electromagnetic interference (EMI) issues of the devices and system levels, as also discussed in [1][2][3][4], robust and reliable power electronics technologies, including fault prognosis and diagnosis techniques [5][6][7], the stability of grid-connected converters [8,9], and the smart control of power electronics for devices, microgrids and at system levels [10][11][12][13].…”