How to eliminate output power oscillation of grid-connected inverter under unbalanced grid voltage?
At present, the main methods to eliminate the output power oscillation of grid-connected inverter under unbalanced grid voltage can be divided into two categories: the first type is to improve the control strategy; the second one is to change the topology of the inverter.
Why does a grid-connected inverter oscillate under a weak grid?
With the decline of grid stiffness, the typical roots of sub-synchronous oscillation (SSO) mode gradually shift from the left-half plane to the right-half plane, which means that the grid-connected inverter will oscillate under weak grid. By analyzing the participation factor of SSO mode, it finds that PLL is the dominant factor.
Can a grid connected inverter cause sub/super synchronous oscillations?
Under weak grid, the grid-connected inverter can easily cause sub/super-synchronous oscillations, which are determined by the oscillation modes of system. Firstly, based on the eigenvalue analysis, the sub/super-synchronous oscillation modes of the grid-connected inverter are revealed with considering the phase-locked loop (PLL) and control delay.
What is a grid connected inverter?
1. Introduction The grid-connected inverter is the vital interface module for distributed generation (DG) systems, including wind power generation, photovoltaic power generation, to be connected to the grid. It can directly determine the value and direction of current and power and is crucial for the safe operation of the grid [1, 2].
Does a grid-connected inverter have a low-frequency oscillation?
The issue of low-frequency oscillation (LFO) becomes more prominent when considering the phase-locked loop (PLL) impact of grid-connected inverter (GCI) under weak grid. Impedance analysis shows that the frequency interaction point outside the capacitive negative damping region can effectively avoid the oscillation.
How to design a grid-connected inverter under a weak grid?
Two oscillation modes of the grid-connected inverter under weak grid are analyzed. A Lyapunov theorem-based parameter design method is proposed for PLL. A phase margin design rules of PLL are formulated for the inverter in a weak grid.
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Overview of power inverter topologies and control structures for grid ...
The reference current I ref, is generated from a PLL sinusoidal signal reference which synchronizes the output inverter current with grid voltage as shown in Fig. 5 [29]. The amplitude current is regulated from the external voltage loop. ... This paper has presented different topologies of power inverter for grid connected photovoltaic systems ...
Learn More →(PDF) MPC-based control strategy of PV grid …
Based on the MPC algorithm and the establishment of a discrete-time predictive model, the PV grid-connected inverter dynamically adjusts its output current to suppress power oscillations.
Learn More →Enhanced active damping control with phase compensation …
Grid-connected inverters are crucial interfaces in renewable energy power systems. However, with the continuous increase in the penetration of renewable energy generation, the dynamic interaction between these inverters and the grid becomes increasingly complex, leading to prominent high-frequency oscillation issues. This paper addresses the …
Learn More →PLL phase margin design and analysis for mitigating …
Two oscillation modes of the grid-connected inverter under weak grid are analyzed. A Lyapunov theorem-based parameter design method is proposed for PLL. A phase margin …
Learn More →Design and Optimization of a High-Frequency Oscillation
It is found in Figure 15 that when H i = 0, the grid-connected current cannot be kept stable and a large number of high-frequency oscillations will occur in the grid-connected current. These high-frequency oscillations are mainly high-frequency harmonics introduced by LCL resonance, and the control effect of suppressing the original oscillation ...
Learn More →Active/reactive power control of photovoltaic grid-tied …
grid-tied inverters with peak current limitation and zero active power oscillation during unbalanced voltage sags ... also applied for the grid-tied inverter which results in zero active power oscillation. Experimental results of a grid-connected 3.3-kVA, three-level, neutral-point-clamped inverter laboratory prototype are presented to ...
Learn More →Stability analysis and resonance suppression of multi-inverter …
Resonance suppression method for grid-connected inverter based on feedforward loop and current loop impedance reshaping under weak grid Proceedings of the 2021 IEEE 1st International Power Electronics and Application Symposium (PEAS), Shanghai, China ( 2021 ), pp. 1 - 9, 10.1109/PEAS53589.2021.9628552
Learn More →Control of Grid Connected Converters Under Unbalanced Grid …
Abstract: A grid connected inverter with an unbalanced voltage at the point of common coupling creates oscillation in DC link voltage at twice the grid frequency and inject highly distorted current into the grid. In this paper analytical expression for oscillation of DC link voltage and distortion in current injected to the grid are derived. Two control strategies for grid connected inverter ...
Learn More →Research on Stroboscopic Mapping Modeling and …
For the grid-connected inverter system, the sustained constant-amplitude oscillations often occur. At this time, the grid-connected current undergoes oscillation, and the PWM process appears saturation nonlinearity (i.e., overmodulation). However, the existing modeling methods cannot accurately model this hard nonlinearity, thereby explaining the phenomenon of grid-connected …
Learn More →An H∞ filter based active damping control strategy for grid-connected ...
But it can cause high-frequency oscillations and instability, which limits its application in wind power system. For an LCL-type grid-connected inverter, the conventional capacitor-current-feedback type active damping control strategy can retain the high-frequency characteristics of LCL filter while suppressing the resonant peak effectively ...
Learn More →Design and Optimization of a High-Frequency Oscillation
It is found in Figure 15 that when H i = 0, the grid-connected current cannot be kept stable and a large number of high-frequency oscillations will occur in the grid-connected …
Learn More →Overview of Impedance Passivation Methods for Grid-Following and Grid ...
The grid-following inverter acts as a controlled current source externally, regulating the active and reactive power injected into the grid by controlling the AC-side grid-connected current, and synchronizing with the grid through a phase-locked loop . In contrast, the grid-forming inverter operates externally as a controlled voltage source ...
Learn More →Improved scheme of grid-connected inverters based on …
Fig. 16 shows the experimental waveform of q-axis component of grid-connected current when the grid voltage amplitude drops by 8 %. When proposed PLL is adopted, GCI recovers to the stable operation state faster, system adjustment time is shorter, and the amplitude of oscillation is also decreased.
Learn More →Parallel operation of Grid-Forming Inverters (GFMIs)
The pre-synchronization of the grid-forming inverters is shown below. Simulink model for pre-synchronization of GFMIs Experimental setup. The experimental validation of the parallel operation of grid-forming inverters is carried out with three TPIs used in a master-slave configuration (connected with SFP cables), meaning that they are programmed from the same …
Learn More →Harmonic Interaction Analysis Between Multi-Inverter …
The grid-connected system, composed of the multi-inverters with LCL filters, may cause harmonic amplification of grid-connected current by harmonic excitation, even oscillation of the system in severe cases. Therefore, analyzing the stability and harmonic interaction of the multi-inverter system is of great significance in improving the system''s power quality. …
Learn More →Stability Comparison of Grid-Connected Inverters …
Under the background of high permeability, voltage feedforward control may further weaken the stability of grid-connected inverter (GCI) systems and may cause sub-synchronous oscillation in extreme cases. To solve this problem, this paper firstly considers the influence of the frequency coupling effect and voltage feedforward control, and adopts the harmonic …
Learn More →Impedance-Based Stability Analysis of Grid …
As a common interface circuit for renewable energy integrated into the power grid, the inverter is prone to work under a three-phase unbalanced weak grid. In this paper, the instability of grid-connected inverters under the …
Learn More →Enhanced active damping control with phase compensation …
This paper proposes an enhanced grid-connected current feedback active damping control method with phase compensation. It enhances the stability and performance …
Learn More →Admittance Modeling and Stability Enhancement of Grid-connected ...
With the grid-connected inverter modeled as a current source in parallel with an output admittance, the overall inverter-grid system is established in ... It is observed from Fig. 16 that there is a harmonic oscillation in the grid-side current and the oscillation is composed of the corresponding disturbance component (20 Hz) and its ...
Learn More →Stability analysis of grid-connected inverter under full …
The grid-connected inverter, serving as the primary interface component, exhibits susceptibility to grid interactions. This results in a series of broadband oscillation issues [3] . For instance, sub/super-synchronous oscillation events at wind farms in Guyuan, Hebei, China, and Hami, Xinjiang, China, have severely threatened the stable ...
Learn More →An active damping control strategy for suppressing
The peak value of the grid-connected current is set to 20 A, and the grid-connected experiments are carried out under the grid impedance of 0mH, 2mH, and 5mH. The experimental results are shown in ...
Learn More →A Multi-Objective Control Strategy for Three Phase Grid-Connected ...
This paper presents a new multi-objective control strategy for inverter-interfaced distributed generation (IIDG) to ensure its safe and continuous operation under unbalanced voltage sags. The proposed control strategy can effectively improve the low voltage ride through (LVRT) capability, reduce active power oscillations, and limit overcurrent simultaneously, …
Learn More →Improvement of grid injected currents in single-phase inverters ...
Two possible paths are detected to propagate the voltage oscillations from the inverter DC link voltage to the inverter output current: (1) directly from the DC link to the output …
Learn More →A Modified Grid-Connected Inverter Topology for Power …
In this paper, considering the solvability of reference current matrix equation, the inherent mechanism of inverter output power oscillation is analyzed, and a modified topology …
Learn More →Analysis and Suppression of Harmonic …
In photovoltaic grid-connected systems, the interaction between grid-connected inverters and the grid may cause harmonic oscillation, which severely affects the normal operation of the system. To improve the quality of …
Learn More →Modeling and Control Parameters Design for Grid-Connected Inverter ...
Small-signal stability problems often occur when the inverter for renewable energy generation is connected to weak grid. A small-signal transfer function integrated model reflecting the interaction of grid impedance, phase locked-loop (PLL), and current control loop is established in this paper. Based on the established model, the oscillation mechanism of the grid …
Learn More →Minimisation of power oscillations with a novel …
The grid-connected inverters (GCIs) are widely used in the renewable energy source (RES)-based distributed generation (DG) ... the DC-link oscillations, current loop or voltage support under unbalanced operating …
Learn More →MPC-based control strategy of PV grid connected …
grid-connected systems in power oscillation was analyzed. Then, based on the established discrete-time predictive model ... based control strategy dynamically adjusted the output current of the PV grid-connected inverter to suppress the oscillation of the generator rotor transient angle to dampen the power oscillations. The advantage of the ...
Learn More →A Modified Grid-Connected Inverter Topology …
Under unbalanced grid voltage faults, the output power oscillation of a grid-connected inverter is an urgent problem to be solved. In the traditional topology of inverters, it is impossible to eliminate power oscillation and …
Learn More →Harmonic characteristics and control strategies of grid-connected ...
The three-phase voltage-source inverter circuit uses IGBT as the switching device and constitutes a bridge arm with an anti-parallel diode. For three-phase grid-connected inverter, the grid-connected current harmonics include high-order harmonics and low-order harmonics [74,75]. High order harmonics are caused by PWM modulation.
Learn More →Innovative adaptive virtual impedance for resonance …
The study in [29]investigates the harmonic interaction between virtual synchronous generators (VSGs) and the utility grid, proposing a capacitor current control strategy for grid-connected inverters to enhance resonance suppression. It establishes an output impedance model and validates its effectiveness through simulation and experimental ...
Learn More →Active/reactive power control of photovoltaic …
Therefore, the design of the controller of the grid-connected inverter becomes more challenging during unbalanced grid voltage sags. ... or two phases may be higher than the inverter nominal current because the …
Learn More →Grid Forming Control of Grid-Connected Converters with …
By exploring the virtual impedance of inverters with virtual synchronous generator control and optimizing the virtual inertia and damping coefficient, an enhanced grid forming control strategy is proposed to improve the power grid support capability of converters for renewable energy integration, leading to improved stability of power system ...
Learn More →Oscillation Suppression Method by Two Notch Filters for …
With plenty of parallel inverters connected to a weak grid at the point of common coupling (PCC), the impedance coupling interactions between the inverters and the grid are enhanced, which may cause high-frequency harmonic oscillation and further aggravate the system instability. In this paper, a basic technique for inverter output impedance is proposed to suppress the oscillation, …
Learn More →A Unified Method of Frequency Oscillation Characteristic Analysis for ...
Angular frequency interactions between inverters and the grid exhibit various numbers of complicated characteristics that seriously threaten the connected power system''s stable …
Learn More →Oscillation Suppression Strategy of Three-Phase Four-Wire Grid …
As the penetration of renewable energy increases year by year, the risk of high-frequency oscillation instability increases when a three-phase, four-wire split capacitor inverter (TFSCI) is connected to the grid with complementary capacitors in weak grids. Compared to the three-phase, three-wire inverter, the TFSCI has an additional zero-sequence current loop. To …
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