Impedance-Based Interactions in Grid-Tied Three-Phase Inverters in Renewable Energy Applications

Abstract

Impedance-ratio-based interaction analyses in terms of stability and performance of DC-DC converters is well established. Similar methods are applied to grid-connected three-phase converters as well, but the multivariable nature of the converters and the grid makes these analyses very complex. This paper surveys the state of the interaction analyses in the grid-connected three-phase converters, which are used in renewable-energy applications. The surveys show clearly that the impedance-ratio-based stability assessment are usually performed neglecting the cross-couplings between the impedance elements for reducing the complexity of the analyses. In addition, the interactions, which affect the transient performance, are not treated usually at all due to the missing of the corresponding analytic formulations. This paper introduces the missing formulations as well as explicitly showing that the cross-couplings of the impedance elements have to be taken into account for the stability assessment to be valid. In addition, this paper shows that the most accurate stability information can be obtained by means of the determinant related to the associated multivariable impedance ratio. The theoretical findings are also validated by extensive experimental measurements.

Impedance-Based Stability Analysis of Paralleled Grid-Connected Rectifiers: Experimental Case Study in a Data Center

“…The high power consumption of a data center may cause issues in power quality, such as high total harmonic distortion (THD) or flicker in grid voltages [4,5]. In addition, the grid interface of power-electronic devices is prone to adverse interactions, which may lead to dramatic stability issues [6]. The threat of instability increases as more power-electronic units are connected in parallel [7].…”

Harmonic Stability Analysis for Multi-Parallel Inverter-Based Grid-Connected Renewable Power System Using Global Admittance

“…The nonlinear methods [12,13] involve intensive computations and are not suitable for large-scale grid-connected systems. In contrast, the linear methods require fewer computations and The impedance-based approach is a frequency-domain analysis technique [19][20][21][22][23][24][25][26]. This method was originally presented in [19] and was used to study the interactions between DC-DC converters and their filters.…”

Low-Loss Active Grid Impedance Cancellation in Grid-Connected Inverters with LCL Filter

“…In the DPGS, an impedance-based analytical approach is usually applied to incorporate multiple paralleled inverters into a single inverter based on the assumption that all paralleled inverters together with their control function are equal [24,25], but it becomes difficult to use when DPG inverters are not equal because the system with different inverters requires a complicated reformulation of the system description [26]. As previously described, the existence of grid impedance is the critical factor to challenge the suppression of the local filter resonance, arouse the multiple interactive resonance, and aggravate the injected power quality of the DPGS [27,28]. A well-known method is to utilize the PCC voltage feedforward control to ease such dynamic interaction between inverters and the grid and improve the power quality of the inverter.…”

“…In reference [34], an active circuit in series at the inverter output is used to mimic the negative grid impedance and cancel the effects of grid impedance on the dynamic interaction between inverters and the grid. By doing so, the stability of the grid-connected inverter is As previously described, the existence of grid impedance is the critical factor to challenge the suppression of the local filter resonance, arouse the multiple interactive resonance, and aggravate the injected power quality of the DPGS [27,28]. A well-known method is to utilize the PCC voltage feedforward control to ease such dynamic interaction between inverters and the grid and improve the power quality of the inverter.…”