Control Scheme and Performance Analysis of Dual-Frequency Single-Phase Grid-Connected Inverter Interfaced With Weak and Distorted Grids

“…Stiff Grid (ΔV, Δω) 0 Weak Grid or Islanded System (ΔV, Δω) > 0 (1) Short Circuit Ratio (2) X/R Ratio (3) Inertia Constant Distortion (4) The authors in [27] showed that the grid distortion increases the challenge of stabilizing the system even with small disturbance when the grid's inductive performance shifts the resonance frequency toward a lower frequency range. This is because the harmonic interactions induce the system instability and minimize the stability margins.…”

Section: Harmonics and Resonance Interaction Voltage Stabilitymentioning

confidence: 99%

“…Small grid impedance values result in a stiff grid with a high SCR. Large values of grid impedance seen at the POC result in a low SCR due to the increased voltage drop at the transmission lines [2][3][4]. This, in turn, deteriorates the voltage quality and the power transfer capability of the grid.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Performance Evaluation of Inverter Feeding a Weak Grid Considering Variable System Parameters

et al. 2021

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Interfacing a weak grid imposes challenges on distributed generators (DGs). These challenges include transient frequency and voltage dynamics that can destabilize the system. Accordingly, this paper investigates the grid stiffness based on different scenarios and the dynamics of a grid feeding DG connected to a weak grid. Moreover, the dynamic effects of the physical and control parameters on the system's stability are deeply analyzed and evaluated. Specifically, complete mathematical models and graphical representation are carried out to precisely examine the impact of the system parameters on the stability and performance of the DG. Therefore, stable deployment of renewable energy resources into power networks can be achieved as well as an efficient and robust performance of DGs can be ensured when connected to weak grids. The obtained results show the importance of the performed study in optimal sizing and designing the output filter of the inverter and the impact of tuning the control parameters on the system dynamics. As a result, a proper design of system physical and control parameters can be accurately achieved considering all factors affect the system performance. The paper also conducts detailed and elaborated analyses and simulations to evaluate the performance of a PI-controlled RC damped inverter connected to a weak grid. The proposed filter design of the interfacing inverter can significantly extend the integration of DGs into microgrids without requiring complex control schemes or oversized components.

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“…To solve the above-mentioned problems, a novel single-phase inverter was proposed in [25][26][27], which included two converters operating at different switching frequencies. One converter operated at low pulse ratio to inject current into the grid, while the other converter eliminated the grid current ripple with a high pulse ratio, using the feedforward compensation method.…”

Section: Introductionmentioning

confidence: 99%

Grid Harmonics Suppression for Three Phase Dual-Frequency Grid-Connected Inverter Based on Feedforward Compensation

Chen,

Ma,

Yang

et al. 2023

Symmetry

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Using a low pulse ratio, the electromagnetic interference and switching loss of an inverter can be effectively reduced, particularly in high-power applications. However, due to variations in grid impedance, it is a challenging task to achieve stable operation of an LCL-type grid-connected inverter (GCI) using the active damping method with low pulse ratio. Thus, a novel three-phase dual-frequency GCI is presented to ensure the symmetry of the output power and the stable operation of the system address stability issues. The proposed inverter topology in this article is composed of two inverters in parallel, which are, respectively, a power inverter unit (PIU) and an auxiliary harmonic elimination unit (AHEU). To reduce the switching loss and improve the inverter efficiency, the switching frequency of the PIU is relatively low, injecting current into the grid. Moreover, the feedforward compensation method is used in AHEU. AHEU operates at high switching frequency to generate a current component that is symmetrical with the ripple com-ponent, improving the power quality, without extracting the current harmonic as the current reference. The operating principle of feedforward compensation is explained, and a proper parameter design procedure is presented in this paper. Since L filters are used for the proposed inverter, the system can operate stably where the ratio of switching frequency to fundamental frequency is low. A 10 kW laboratory prototype was built. The experimental results showed that the grid current ripple could be effectively eliminated and the THD of the grid current was 3.01%. The proposed inverter has good stability in a weak grid, and the efficiency of the proposed inverter is 95.98% at rated current, which is 0.81% higher than the traditional GCI, effectively increasing the efficiency of the system.

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Control Scheme and Performance Analysis of Dual-Frequency Single-Phase Grid-Connected Inverter Interfaced With Weak and Distorted Grids

Cited by 8 publications

References 45 publications

Robust Delay Compensation Strategy for LCL-Type Grid-Connected Inverter in Weak Grid

Robust Delay Compensation Strategy for LCL-Type Grid-Connected Inverter in Weak Grid

Dynamic Performance Evaluation of Inverter Feeding a Weak Grid Considering Variable System Parameters

Grid Harmonics Suppression for Three Phase Dual-Frequency Grid-Connected Inverter Based on Feedforward Compensation

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