The penetration of solar energy into centralized electric grids has increased significantly during the last decade. Although the electricity from photovoltaics (PVs) can deliver clean and cost-effective energy, the intermittent nature of the sunlight...
The increasing use of multi-parallel grid-connected inverters introduces both high-quality and high-capacity power, while it tends to cause a resonance instability problem. A resonance damper can virtualize a resistor at resonant frequency to suppres...
This study paper presents a comprehensive review of virtual inertia (VI)-based inverters in modern power systems. The transition from the synchronous generator (SG)-based conventional power generation to converter-based renewable energy sources (RES)...
Virtual synchronous generators (VSGs) simulate the operating characteristics of conventional synchronous generators to provide inertia, voltage and frequency support for new-type power systems dominated by power electronics. However, in the event of...
Grid frequency must be regulated in its nominal range to guarantee the stable operation of an electric power grid. Excessive grid frequency excursions result in load shedding, grid frequency instability, or even synchronous generator damage. With the...
With the increasing penetration of renewable energy sources, variations in grid impedance and background voltage harmonics have become major challenges to the operational stability and power quality of grid-connected inverters. Although conventional...
The paper conducts a comprehensive analysis of the impact of very large-scale photovoltaic generation systems on various aspects of power systems, including voltage profile, frequency, active power, and reactive power. It specifically investigates IE...
The voltage source converters convert the DC to AC in order to interface distributed generation units with the utility grid, typically using an LCL filter to smooth the modulated wave. However, the LCL filter can introduce resonance, potentially caus...
Grid-forming (GFM) converters are critical supporting equipment for power systems with high penetration of renewable energy. However, their complex interactions with the grid can lead to broadband instability, posing a serious threat to system securi...
Aiming to achieve fault ride-through (FRT) in a microgrid under the condition of an asymmetric power grid, this paper proposes a scheme that applies the cascaded H-bridge flexible fault current limiter to realize both voltage regulation and current l...
This paper addresses the “dual-high” challenges posed by high proportions of renewable energy and power electronic equipment in new power systems, and investigates the active support characteristics of grid-forming energy storage stations...
Currently, research on the small-signal stability of grid-forming converters under two control modes, grid-following and grid-forming, mainly focuses on low-level converters. However, studies on the differences between grid-following modular multilev...
Full-size converter variable-speed pumped storage units (FSC-VSPSUs) feature bidirectional power flow. They serve as critical equipment for enhancing regulation margins and promoting renewable energy integration. However, bidirectional energy flow el...
To accurately evaluate the small-signal stability of grid-forming (GFM) direct-drive wind turbines over time-varying operating conditions and broad frequency ranges, this paper proposes a wide-frequency stability characteristic domain method. Unlike...
The grid-forming (GFM) wind turbine with energy storage is regarded as a promising solution for the integration of renewable energy sources (RESs) into power systems. However, the system faces the risk of instability during large grid disturbances, s...
Virtual synchronous generators (VSGs) have attracted widespread attention due to their advantage in supporting voltage and frequency of power systems. However, relevant studies have shown that a VSG has similar low-frequency oscillation as synchronou...
Rising renewable penetration has accelerated the volatility and instability of the power grid. A small-scale grid is especially vulnerable. Therefore, flexibility and stability enhancement are required for small-scale grids. The interconnection with...
The high penetration of renewable energy sources (RESs) and power electronics devices has led to a continuous decline in power system stability. Due to the instability of grid-following converters (GFLCs) in weak grids, the grid-forming converters (G...
This paper studies the stability impact of the alternate voltage controller’s (AVC) low-pass filter (LPF) in a wind turbine’s grid-connected voltage source converter (VSC). A small-signal model of the grid-connected converter is designed...
Parallel converter operation enables flexible capacity expansion of energy-storage power conversion systems. However, parallel converter interactions, filter-inductor saturation, and grid-strength variations increase the risk of resonance instability...
In the past decade, inverter-integrated energy sources have experienced rapid growth, which leads to operating challenges associated with reduced system inertia and intermittent power generation, which can cause instability and performance issues of...
This paper presents a small signal stability analysis to assess the stability issues facing PV (photovoltaic) inverters connected to a weak grid. It is revealed that the cause of the transient instabilities, either high-frequency or low-frequency osc...
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 agg...
Hybrid supercapacitors possess high power and energy density, while the cascaded H-bridge converter features rapid response capability. Integrating these two components leads to an energy storage system capable of swiftly responding to power demands,...
Lack of synchronization between high voltage DC systems linking offshore wind farms and the onshore grid is a natural consequence owing to the stochastic nature of wind energy. The poor synchronization results in increased system disturbances, grid c...
Portable industrial X-ray flaw detectors operating in outdoor environments predominantly rely on small diesel generators for power supply. However, the inherent grid frequency drift of such weak grids induces critical phase-shift mismatches in conven...
Under the drive of the “dual carbon” goals, the insufficient frequency regulation capability of nuclear power as a baseload source and the dynamic demand of integrating a high proportion of renewable energy into the grid have increasingly...
Under the condition of asymmetric system voltage, grid-connected inverters exhibit obvious sequence impedance frequency coupling characteristics, which can easily lead to resonance and the misoperation of protection and control devices. Currently, ta...
With the large-scale integration of converter-based renewable energy into power systems and the large-scale construction of HVDC, risks associated with supply–demand imbalance and post-contingency frequency instability of sending-end power grid...
Wind-driven turbines utilizing the doubly-fed induction generators aligned with the progressed IEC 61400 series standards have engrossed specific consideration as of their benefits, such as adjustable speed, consistent frequency mode of operation, se...
This paper proposes a phase-compensated enhanced second-order generalized integrator phase-locked loop (ESOGI-PLL) to suppress the frequency coupling effect (FCE) and its associated power quality degradation in grid-following inverters (GFLIs). An ou...
To address the potential oscillation instability issues of grid-forming (GFM) inverter systems integrated into grids with reactive power compensation devices, an impedance-based model of the grid-connected system is established. The impedance analysi...
The hybrid parallel operation of the grid-following (GFL) converter and the grid-forming (GFM) converter has become a typical scenario in distribution networks. The vastly different control philosophies and dynamics between the two give rise to compl...
With the large-scale integration of Class B distributed photovoltaic power sources without fault-tolerant capabilities, the “pulse blocking-recovery” transient behavior during power grid faults has become a key factor affecting the freque...
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 unbalanced grid condition...
The DC-link voltage control (DVC) timescale (i.e., the frequency dynamics covering converter outer controls) instabilities in wind generation have gained increased attention recently. This paper presents DVC timescale modeling and stability analysis...
New energy power sources can be categorized into grid-following and grid-forming types based on their synchronization characteristics with the grid. Due to the different basic control operation principles of these two types of new energy power source...
The microgrid (MG) system is a controlled and supervised power system consisting of renewable energy (RE)-based distributed generation (DG) units, loads, and energy storage. The MG can be operated autonomously or while connected to the grid. Higher i...
In distributed generation systems, the inverter is the main power interface and its stability directly determines the reliable operation of the grid-connected system. As a typical topology for a three-phase four-wire inverter, the LCL-type three-phas...
The replacement of synchronous generators (SGs) with inertia-less renewable energy sources (RESs) poses a significant challenge to grid stability due to the reduction of system inertia. To prevent grid instability, energy storage systems (ESSs) with...
The progressive replacement of synchronous machines by inverter-based resources (IBRs) reduces system inertia and short-circuit strength, making power systems more vulnerable to frequency and voltage instabilities. Grid-forming (GFM) inverters can mi...
The increased penetration of renewable energy sources (RES) in the electrical grid has necessitated the concept of a Virtual Synchronous Generator (VSG) control which is used to make grid-connected power electronic converters behave as synchronous ge...
In light of the challenges of integrating more renewable energy sources (RESs) into the utility grid, the virtual synchronous generator (VSG) will become an indispensable configuration of modern power systems. RESs are gradually replacing the convent...
The rapid integration of solar power into distribution grids has intensified challenges related to frequency instability caused by fluctuating renewable generation. These unexpected frequency variations are difficult to capture using traditional or s...
The escalating adoption of low-carbon energy technologies underscores the imperative to transition from conventional fossil fuel-dependent sources to sustainable alternatives. The expansion of Distributed Energy Resources (DERs) signifies an essentia...
This paper develops the impedance models of grid-connected converters under the virtual synchronous generator (VSG) strategy with a cascaded inner control loop and analyzes the system stability of VSG controlled converters with different kinds of wea...
To address the decline in system inertia and the risk of frequency instability resulting from high penetration of renewable energy, and to overcome the limitations of centralized control—such as high computational burden and slow response&mdash...
Wind power generation exhibits pronounced volatility and intermittency, and direct grid connection may cause instability in grid frequency. To address this issue, this paper proposes an optimisation strategy for hybrid energy storage systems to mitig...
To investigate the harmonic resonance, harmonic instability and low-frequency oscillation phenomena in high-speed railways, this paper proposes a full-frequency impedance model of the train-traction network system (simplified as ‘train-network&...
To mitigate the fast-growing demand of electrical energy, the use of renewable energy resources, e.g., solar and wind, can offer an environmentally friendly and sustainable solution. Due to their intermittent nature, the grid connected operation of r...
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