A robust optimized active disturbance rejection control (ADRC) based grid voltage sensorless current controller is developed for an LCL -filtered grid-connected inverter (GCI) via a predictive ...control approach under various sources of disturbance, including the model uncertainties, the LCL inherent resonance phenomenon, and nonideal grid environment. Aiming to improve the sinusoidal reference tracking performance as well as to reject lumped sinusoidal disturbances in the control practice, a resonant extended state observer is integrated into the ADRC structure, which guarantees a rigorous stable operation of inverter for bounded filter parameter uncertainties and adverse grid voltage conditions. The grid frequency adaptability is thoroughly considered in the controller design process and synchronization technique, offering an extra capability for GCI to operate under different grid voltage frequency levels or even the frequency deviation caused by grid fault events. Robustness against parameter uncertainty and system stability is analyzed through the discrete-time frequency analysis and pole-zero map approaches. The simulation and hardware experiments are conducted for GCI with LCL filter parameters designed for two typical regions (i.e., the resonance frequency is less and greater than one-sixth of switching frequency) to validate the theoretical analysis and the effectiveness of the proposed control method.
This article addresses the multiview multisensor fusion problem: the limited fields of view (FoVs) of the agents in the network are partially/nonoverlapping, thereby inducing the discrepancy among ...the local multitarget densities. Besides, for labeled random finite sets (RFSs), the labels are locally generated by the agents, which causes label inconsistency among the local label spaces. In this article, a fusion method is proposed to solve the multiview fusion problem and the label inconsistency problem simultaneously. Specifically, an information complement method was proposed for appending the virtual LMB components to each local multitarget density, reducing the difference among the complemented local multitarget densities. This method is realized by solving an optimization problem based on the GCI divergence. However, this problem is hard to solve, thus, a greedy algorithm is applied to obtain a suboptimal solution. The upper bound of the gap between the suboptimal and optimal solutions is also given in the article, and a cutoff threshold of the greedy algorithm is proposed according to this upper bound. Then the joint label GCI (JL-GCI) is used to obtain the fused multitarget density among the complemented local multitarget densities. The simulation results demonstrate the effectiveness of the proposed method.
The aim of this study is to identify impact factors on the comparative evolution of competitiveness by analyzing the two macroeconomic indicators Gross Domestic Product and Global Competitiveness ...Index in the two emerging countries - Romania and Poland, in 2015-2020, based on data provided by Eurostat and the National Institute of Statistics and Economic Studies, respectively by the global competitiveness reports. Gross Domestic Product (GDP) is the most complex indicator calculated in all European Union countries and expresses an appropriate comparability (according to National Accounts record system). If we consider the analysis of the gross domestic product per capita and the parity of purchasing power, we will be able to analyze comparatively both the size of the development of each country and the standard of living of the population, respectively the quality of life. In this study, the GDP comparisons were performed after assessing the stage of economic evolution in each country. In the article we have introduced several graphs that help us to highlight the conclusions drawn from the analysis of the data we have. It is also analyzed the evolution of the Global Competitiveness Index (GCI), a comprehensive tool that measures the microeconomic and macroeconomic fundamentals of competitiveness. The GCI provides a detailed analysis of the productive potential of national economies
Under low-switching-frequency condition, there is harmonic coupling in grid-connected inverter. The harmonic state-space (HSS) modeling method is an effective means to analyze the output harmonic ...characteristics of inverter. When the switching frequency is low, the sampling/holding and control delay make the update of pulsewidth modulation pulses more untimely, which will have a non-negligible impact on system output. However, the current relevant research fails to take these factors into account in the HSS model. In addition, the existing work fails to thoroughly study the calculation and analysis methods of HSS model, and the relevant work is insufficient. Based on this, this article studies the closed-loop HSS model and its calculation and analysis methods of three-level grid-connected inverter considering the digitization impact. First, according to the different calculation and analysis methods of the HSS model of the grid-connected inverter, the methods considering the digitization impact are proposed, respectively. Second, according to the proposed method, the harmonic characteristics of low-switching-frequency grid-connected inverter are analyzed, and the necessity of considering the digitization impact is explained. Finally, the effectiveness and accuracy of the proposed HSS-model calculation and analysis methods considering the digitization impact are verified by simulation and experiment.
In LCL grid-connected inverter, low switching frequency makes the control loop, filter resonant peak, and sideband harmonics generated by modulation coupled in mid-frequency band. When multiple ...inverters operate in parallel, the asynchronous carrier phase (i.e., asynchronous carriers) will cause additional mid-frequency resonance in each inverter. This will coexist with the inherent mid-frequency harmonic coupling of each inverter. Then, the mid-frequency harmonic characteristics of parallel system will become more complex, which will increase the difficulty of accurately modeling, and analyzing the harmonic characteristics of the output current of each inverter and total grid-connected current. Based on this, a complete harmonic state-space (HSS) model of parallel system considering asynchronous carriers and its frequency-domain analysis method are proposed in this article, which realizes the accurate analysis of the impact of asynchronous carriers on system harmonic characteristics. Meanwhile, an iterative calculation method of parallel-system HSS model considering asynchronous carriers is proposed, which realizes the efficient and accurate calculation of the output current harmonic amplitude and phase of each inverter. Finally, the effectiveness of the proposed model and analysis method are verified through simulations and experiments.
•The development and characteristics of low temperature combustion are reviewed.•The various modes of achieving low temperature combustion are analyzed fuel wise.•The effects of various fuels on low ...temperature combustion are discussed.•Limitations and key factors of low temperature combustion engines are pointed out.•Vast experimental data on low temperature combustion for many fuels are tabulated.
The fast rate of depletion of fossil fuel resources due to increasing demands and the adverse environmental impact by the automotive engines forced researchers to develop alternative strategies to meet the stringent emission norms in terms of oxides of nitrogen and particulate matter. In this regard, low temperature combustion is one of the promising advanced in-cylinder combustion strategies for reducing both oxides of nitrogen and particulate matter emissions simultaneously with a beneficial effect on specific fuel consumption. The low temperature combustion is achieved through homogeneous charge compression ignition, premixed charge compression ignition, reactivity controlled compression ignition and gasoline compression ignition. In this paper, an attempt is made to assemble and summarize a listing of important research articles on low-temperature combustion using a wide variety of conventional and alternate renewable fuels. The effect of low-temperature combustion on engine performance and emission characteristics over a wide range of engine test conditions and the challenges faced in these strategies are also described. From the assemblage of articles on low-temperature combustion using conventional and renewable fuels, it is understood that this strategy can help in achieving better performance, lower cylinder pressure and heat release rate, and simultaneous reductions of nitrogen oxides and particulate matter, but typically with an increase in carbon monoxide and hydrocarbon emissions. This literature review is expected to be useful to the researchers for understanding the concept, challenges, and the state-of-the-art of the different modes of low-temperature combustion using conventional and sustainable alternate fuels.
•Multi-target tracking using multiple sensors having different fields of view.•Fusion of the posterior Probability Hypotheses Densities of the sensors.•Robust distributed fusion based on generalized ...covariance intersection.•A clustering algorithm is used to derive an efficent parallelized fusion strategy.•Compensation strategy to preserve targets outside the common field of view.
Distributed multi-target tracking (DMTT) is addressed for sensors having different fields of view (FoVs). The proposed approach is based on the idea of fusing the posterior Probability Hypotheses Densities (PHDs) generated by the sensors on the basis of the local measurements. An efficient and robust distributed fusion algorithm combining the Generalized Covariance Intersection (GCI) rule with a suitable Clustering Algorithm (CA) is proposed, named CA-GCI fusion algorithm. The CA is used to decompose each posterior PHD into well-separated components (clusters). For the commonly detected targets, an efficient parallelized GCI fusion strategy is proposed and analyzed in terms of L1 error. For the remaining targets, a suitable compensation strategy is adopted so as to counteract the GCI sensitivity to independent detections while reducing the occurrence of false targets. Detailed implementation steps using a Gaussian Mixture (GM) representation of the PHDs are provided. Numerical experiments clearly confirm the effectiveness of the proposed CA-GCI fusion algorithm.
The weak grids may be unstable due to the negative resistance behavior of the grid-connected inverter (GCI) caused by the synchronization unit with the phase-locked loop (PLL). This article proposes ...a passivity enhancement method to attain the positive output resistance of GCI in the qq channel. Initially, the impedance decomposition is utilized to reveal the reason for the negative output resistance brought by PLL. Secondly, with decomposed impedance, a novel PLL by adding a prefilter and an impedance phase regulator with a normalized amplitude to the input of traditional synchronous reference frame PLL (SRF-PLL) is proposed. Afterward, the effect of the critical system parameters and GCI operating conditions on the GCI's passivity is discussed based on the established small-signal impedance model. Theoretical analysis manifests that the proposed PLL does not affect the system's stability under rectifier mode and brings the passivity of GCI's output impedance in the qq channel in broad system parameters under inverter mode. Lastly, the experiments are implemented, verifying that using the proposed PLL, the instability caused by the intersection between grid and GCI impedances is removed due to the passivity, and the system can operate at 1.0 per unit (pu) active power reference under the very-weak-grid conditions.
Multiresonant controllers are widely used in the current control of grid-connected converters due to their accurate tracking of reference sinusoidal signals containing high harmonic counts. However, ...the performance of multiresonant controllers relies heavily on the suitability of the parameter design. In this paper, a generalized multiresonant controller that unifies various existing resonant controllers is proposed, which achieves the decoupling of the proportional terms, eliminates the need for online operation of trigonometric functions, and obtains a more extensive range of regulation capability. Furthermore, a new multioptimized parameter tuning method that considers several performance indexes is proposed to utilize the generalized resonant controller's performance fully. Finally, based on the proposed method, a generalized multiresonant controller is designed for <inline-formula><tex-math notation="LaTeX"> {\bm {L}}</tex-math></inline-formula>-type and <inline-formula><tex-math notation="LaTeX"> {\bm {LCL}}</tex-math></inline-formula>-type grid-connected inverters, respectively, demonstrating the universality of the proposed approach. Simulation and experimental results validate the effectiveness of the proposed method.
To enhance the interactive stability between an LCL -type grid-connected inverter (GCI) and the grid, a passive damper (PD) is necessary for passivizing the output admittance of the GCI system since ...an active damper (AD) may not work in scenarios such as beyond the Nyquist frequency. This article explores the best installation locations of PD where higher efficiency can be obtained. To this end, a general admittance model of LCL -type GCI with an internal PD (IPD) or external PD (EPD) for different scenarios is derived. By leveraging the derived model, the passivity compensation burden is compared for IPD and EPD by analyzing the amplification and reduction characteristics of output admittance seen from the point of common coupling (PCC). Then, the EPD additivity conditions are figured out for different scenarios to guide the installation of the PD in the GCI system, which can fulfill full-frequency passive output admittance at the expense of relatively lower damping losses. Moreover, a design method for the EPD is also detailed in the article. Finally, GCI prototypes with high or low switching frequencies are tested in the laboratory and compared with state-of-the-art PD methods. The experimental results verify the effectiveness and superiority of the proposed EPD method.
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