Abstract
Photovoltaic (PV) power systems are increasingly being used as renewable power generation sources. Quasi-Z-source inverters (qZSI) are a recent, high-potential technology that can be used to integrate PV power systems into AC networks. Simultaneously, concerns regarding the stability of PV power systems are increasing. Converters reduce the damping of grid-connected converter systems, leading to instability. Several studies have analyzed the stability and dynamics of qZSI, although the characterization of qZSI-PV system dynamics in order to study transient interactions and stability has not yet been properly completed. This paper contributes a small-signal, state-space-averaged model of qZSI-PV systems in order to study these issues. The model is also applied to investigate the stability of PV power systems by analyzing the influence of system parameters. Moreover, solutions to mitigate the instabilities are proposed and the stability is verified using PSCAD time domain simulations.
Highlights
The flexibility and efficiency of two-stage voltage source inverter (VSI) topologies have led to their widespread use; single-stage topologies based on impedance-source networks with a centralized inverter [6,7,8,9] or micro-inverters [10,11] are increasing in popularity as simple and economical configurations that can overcome the shortcomings of two-stage VSI topologies
The models in [25] only allow Simulink and PSCAD dynamic studies of Quasi-Z-source inverters (qZSI)-PV system behavior to be performed, while our model enables the use of different software programs (e.g., Simulink and MATLAB environments), increasing the possibility to carry out qZSI-PV
The stability of the steady-state operating point in case #1 when the irradiation level increases to G = 800 W/m2 (Vmpp = 712.3 V, Impp = 156.4 A; see right of Figure 2a) is analyzed; Case #3: The impact of the total number of PV arrays connected in parallel Np on the PV system stability is studied
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Photovoltaic (PV) systems have become some of the most popular renewable generation sources [1,2,3] They can have different configurations based on centralized or multiple inverters with single- or two-stage topologies [4,5]. Many studies have dealt with this issue in PV power systems based on traditional two-stage converter topologies by means of small-signal state-space (SS) models. The contributions to the knowledge of the following stability issues are presented through the application of the proposed equation: Impacts of qZSI-PV system parameters on stability; Proposals for stability improvement from PFs and analysis of qZSI-PV system damping parameters All of these contributions, which are numerically validated by PSCAD simulations, can be used together as a valuable transient modeling tool and in qZSI-PV system stability studies
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