A5101918395- Microgrid Control and Optimization
- Islanding Detection in Power Systems
- Power Systems and Renewable Energy
- HVDC Systems and Fault Protection
- Multilevel Inverters and Converters
- Smart Grid Energy Management
- Advanced DC-DC Converters
- Energy Harvesting in Wireless Networks
- Power Systems and Technologies
- solar cell performance optimization
- Advanced MEMS and NEMS Technologies
- Power System Optimization and Stability
- Smart Grid and Power Systems
- Wind Turbine Control Systems
- Photovoltaic System Optimization Techniques
- Induction Heating and Inverter Technology
- Frequency Control in Power Systems
- Acoustic Wave Resonator Technologies
- Thermochemical Biomass Conversion Processes
- Extremum Seeking Control Systems
- Coal and Its By-products
- Energy, Environment, and Transportation Policies
- Wireless Body Area Networks
- Optimal Power Flow Distribution
- 2D Materials and Applications
Central South University
2013-2024
Nanjing University
2002-2018
Institute of Acoustics
2002
Electric Power Research Institute
2000
Brown University
2000
The weak grids may be unstable due to the negative resistance behavior of grid-connected inverter (GCI) caused by synchronization unit with phase-locked loop (PLL). This article proposes a passivity enhancement method attain positive output GCI in qq channel. Initially, impedance decomposition is utilized reveal reason for brought PLL. Secondly, decomposed impedance, novel PLL adding prefilter and an phase regulator normalized amplitude input traditional synchronous reference frame (SRF-PLL)...
The phase-locked loop (PLL)-caused couplings on the grid-connected converter (GCC) are strengthened by increasing its bandwidth and then incur synchronization instability. This article proposes a constant-coupling-effect-based PLL (CCE–PLL) to resolve aforementioned issues. Initially, feature of PLL-caused GCC is explored. It exhibits that varied along with hence jeopardizing system's stability. Subsequently, CCE–PLL constant low coupling regardless proposed. illustrates does not influence...
The wide bandwidth of phase-locked loop (PLL) will increase the negative real part output impedance grid-connected inverter (GCI), thus destroying stability weak grids. This article proposes a novel method to improve system through decoupling PLL and grid impedance. Initially, coupling relationship between is revealed. It can explain why choice magnitude limited. Then, proposed where primary control structure GCI does not need change uses structured voltage, product PCC voltage admittance,...
The power coupling issue in grid-forming converters (GFMs) is an emerging concern within systems dominated by inverter-based resources. Specifically, the phase difference between two rotational frames, i.e., system/grid and controller has not been associated with effect. It demonstrated that such causes interaction inner control loops. To this end, we first developed a detailed model of GFM system to study sensitivity parameters against issues. In particular, found voltage loop could impact...
We report the experimental realization of Dirac semimetal state in NdSb, a material with antiferromagnetic ground state. The occurrence topological has been well supported by our band structure calculations and observation chiral anomaly induced negative magnetoresistance. A field-induced Fermi surface reconstruction is observed, response to change spin polarization. magnetic provides an opportunity investigate magneto-topological phenomena.
Grid-connected inverters (GCIs) with a voltage harmonics compensation function (VHCF) have been widely applied to ensure the quality of bus voltages in weak grids, while analysis and design process VHCF-GCIs, influence phase-locked loop (PLL) is usually ignored. To cover this gap, harmonic instability amplification VHCF-GCI considering PLL are explored. With small-signal model PLL, mathematical descriptions dynamics on impedance control current derived, output including presented. Based...
In this paper, an improved active stabilization strategy of the interface converters in microgrid applications is proposed on basis passivity-based stability criterion (PBSC). As a critical part AC and DC hybrid microgrids, taken as example. particular, method with proportional-integral (PI) controller firstorder high-pass filter (HPF) to meet passivity requirements overall control diagram respect output voltage. Meanwhile, current feedback loop introduced ensure impedance passivity....
Virtual inertia control (VIC) allows grid-connected converter (GCC) to emulate via the dc-link capacitance. Yet, such a scheme's stability impact revealed by impedance perspective is often overlooked, resulting in coupling issues between and grid. This article presents comprehensive analysis of effect dc-link's VIC on GCC system. The GCC's small-signal model first proposed, which reveals strong <italic xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Eight commercial fly ash samples including two from petroleum coke/coal co-firing were characterized to determine the origin, structure, and properties of unburned carbon. Because its relevance utilization, characterization included measurements adsorptivity toward concrete surfactants, dependence on carbon form, particle size, contact time. The coal/coke ashes are observed possess unique optical adsorptive which related density, internal porosity coke-derived residual char.
To improve the system performance, such as suppress harmonics, restrain resonance, etc., bus voltage feed-forward (BVF) is often added in control of three-phase inverter. Specially, under harmonic and unbalance condition, band pass filter (BPF) embedded path BVF to selected frequency components. While, influence Phase-Locked Loop (PLL) on this ignored prior. In letter, multi-frequency model with BPF considering time-periodic trajectory PLL proposed. Afterwards, adverse effect condition...
Virtual synchronous generators (VSGs) are susceptible to transient instability, especially under large disturbances without equilibrium points (EPs). This article proposes an additional frequency control restore EPs and ensure stability. In this control, the damping effect is enhanced improve behavior, potential energy introduced after detecting instability characteristics of VSGs. Compared with previous stabilizing methods, proposed method can address stability issues both EPs, it does not...
This paper considers the three-phase grid-connected inverter (GCI) as a MIMO system, and presents some new perspectives on stability of GCI. It is found that with traditional Nyquist criterion (NC)-based method which ignores off-diagonal components impedance or admittance matrix, results models are different. To make up this disadvantage, simple analysis based system feedback ratio matrix (SFRM) proposed. Instead ignoring couplings admittance, SFRM in proposed can be equivalent to diagonal...
In this paper, the Single-Input Single-Output (SISO) theory-based stability analysis method for weak grids with a three-phase grid-connected inverter (GCI) incorporating asymmetrical control is proposed in dq-frame and sequence domain, respectively. Initially, paper presents two-coordinate decomposed models Multi-input Multi-output (MIMO) systems. These reveal that of MIMO system can be evaluated by analyzing two open-loop gains or single gain domain using Nyquist/Bode plots. Next,...
This paper presents a new approach of compensating truck scale's weighing errors based on prior knowledge and neural network ensembles (PKNNEs). Truck scale is typical nonlinear system it fussy labor intensive to compensate the with conventional method, leading low accuracy results. The general idea this proposed consists building individual networks (NNs) designing constraint conditions for optimizing (NNEs) scale. First, three uncorrelated NNs are created by using step-distribution...
This article proposes a frequency-locked loop (FLL) with fast and smooth dynamic performance for single-phase grid-connected inverters under adverse grid conditions. Different from modeling the orthogonal signals of same amplitudes or ideal signal, proposed linear frequency estimation model is developed difference signal that are generated by cascaded delayed cancellation operators. Based on this model, an enhanced variable-step-size least mean square algorithm to construct FLL, where factor...
This article proposes a zero-tracking second-order generalized integrator-based frequency-locked loop (ZT-SOGI-FLL) with better dynamics and stability than the conventional SOGI-FLL. Unlike internal model principle, ZT-SOGI-FLL reconstructs input signal under frequency deviation by tracking zeros. Also, it has same compact structure as A linearized is then derived to show that always an over-damped or critical damper system. More importantly, proves larger damping factor higher bandwidth...
Equivalent grid impedance is an essential parameter in the stability analysis of grid-forming converters. The estimator based on PQ variations technique popular practice, yet this has limited estimation accuracy and dynamics. To address issue, effect phase error during power demonstrated paper. quantitatively described by investigating impact controller dynamics equivalent model. By compensating for error, improved with only active disturbance proposed, its implementation tuning are...
This paper proposes a virtual impedance-based bandwidth control method for multi-parallel harmonic-compensation grid-connected inverters (HCGIs). Firstly, the influence of resonance points caused by interaction multiple HCGIs on is analyzed, and analysis result shows that becomes narrow due to appearance new point. Then, increase HCGIs, six different types impedance circuits are constructed compared, based capacitor voltage feedback proposed. Following that, relationship between coefficient...
State variable feedback predictive control (SVFPC) obtains the advantage of and state control, which is proposed to single phase shunt active power filter (SAPF) in nonlinear load (uncontrolled rectifier with inductive capacitive load) conditions. The strategy suppresses most harmonics different loads. advantages using SVFPC compared conventional proportional-integral (PI) are more accurate, strong robustness small overshoot. Moreover, adaptability step-change disturbance SAPF improved. To...
In micro-grid, the quality problems of grid voltage, i.e. unbalance, harmonic pollution and frequency fluctuation, may occur at same time. order to maintain synchronization grid-connected inverter this particular circumstance, an improved dual second-order generalized integrator (DSOGI) PLL is proposed. The components phase are eliminated by adding closed-loop feedback control angular frequency. Meanwhile, precise reference accomplished means zero cross detection circuit relevant soft...
The online estimation of grid impedance is essential for gird-forming (GFM) converters. Due to the requirement prior knowledge voltage, method based on steady-state information GFM converters suffers from limited speed and low accuracy. To address this issue, a transient-responses-based non-intrusive proposed in paper. By exploring transient responses converters, relationship between instantaneous powers used construct linear model parameters. recursive least squares algorithm employed...