scholarly journals Quadrature Voltage Compensation in the Isolated Multi-Modular Converter

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 529
Author(s):  
Cristian Verdugo ◽  
Jose Ignacio Candela ◽  
Pedro Rodriguez
Keyword(s):  
Control Strategy ◽  
Phase Voltage ◽  
Multilevel Converters ◽  
Photovoltaic Panels ◽  
Circulating Current ◽  
Three Phase ◽  
Voltage Compensation ◽  
Wide Range ◽  
Modular Converter ◽  
The Impact

Series connections of modules in cascaded multilevel converters are prone to power imbalances due to voltage differences on their DC side. When modules are connected to direct current (DC) sources, such as photovoltaic panels, the capability of withstanding power imbalances is crucial for generating the maximum power. In order to provide a possible solution for this requirement, this paper proposes a control strategy called Quadrature Voltage Compensation, which allows a wide range of power imbalances. The proposed control strategy regulates the power by introducing a circulating current between the arms and a phase angle in the output voltage. The impact of the circulating current and its effect on the phase voltage are studied. To highlight the features of the proposed strategy, an analytical model based on vector superposition is also described, demonstrating the strong capability of tolerating power differences. Finally, to validate the effectiveness of the Quadrature Voltage Compensation, simulation and experimental results are presented for a three-phase isolated multi-modular converter.

scholarly journals A Control Strategy for Suppressing Zero-Sequence Circulating Current in Paralleled Three-Phase Voltage-Source PWM Converters

2020 ◽  
Vol 10 (5) ◽  
pp. 1703 ◽  
Author(s):  
Zhao Han ◽  
Xiaoli Wang ◽  
Baochen Jiang ◽  
Jingru Chen
Keyword(s):  
Control Strategy ◽  
Voltage Source ◽  
Duty Ratio ◽  
Phase Voltage ◽  
Pwm Converters ◽  
Circulating Current ◽  
Three Phase ◽  
Zero Sequence ◽  
The Difference ◽  
Zero Vector

In microgrids, paralleled converters can increase the system capacity and conversion efficiency but also generate zero-sequence circulating current, which will distort the AC-side current and increase power losses. Studies have shown that, for two paralleled three-phase voltage-source pulse width modulation (PWM) converters with common DC bus controlled by space vector PWM, the zero-sequence circulating current is mainly related to the difference of the zero-sequence duty ratio between the converters. Therefore, based on the traditional control ideal of zero-vector action time adjustment, this paper proposes a zero-sequence circulating current suppression strategy using proportional–integral quasi-resonant control and feedforward compensation control. Firstly, the dual-loop decoupled control was utilized in a single converter. Then, in order to reduce the amplitude and main harmonic components of the circulating current, a zero-vector duty ratio adjusting factor was initially generated by a proportional–integral quasi-resonant controller. Finally, to eliminate the difference of zero-sequence duty ratio between the converters, the adjusting factor was corrected by a feedforward compensation link. The simulation mode of Matlab/Simulink was constructed for the paralleled converters based on the proposed control strategy. The results verify that this strategy can effectively suppress the zero-sequence circulating current and improve power quality.

scholarly journals A New Control Strategy of Three Phase Voltage Source PWM Rectifiers

2012 ◽  
Vol 24 ◽  
pp. 997-1005 ◽  
Author(s):  
Jiuhe Wang ◽  
Hongren Yin ◽  
Shengsheng Xu
Keyword(s):  
Control Strategy ◽  
Voltage Source ◽  
Phase Voltage ◽  
Three Phase ◽  
Pwm Rectifiers

Vector Decoupling Control Strategy for Three-Phase Voltage Source PWM Rectifier

2013 ◽  
Vol 336-338 ◽  
pp. 450-453
Author(s):  
Jian Ying Li ◽  
Wei Dong Yang ◽  
Ni Na Ma
Keyword(s):  
Power Factor ◽  
Control Strategy ◽  
Reactive Power ◽  
Decoupling Control ◽  
Voltage Source ◽  
Pwm Rectifier ◽  
Phase Voltage ◽  
Unity Power Factor ◽  
Three Phase ◽  
Rotating Coordinates

In view of the fact that active power and reactive power have coupling relation, a novel vector decoupling control strategy is presented for three-phase voltage source PWM rectifier. In the paper, the power control mathematical mode of the PWM rectifier is deduced based on the mathematical model of rectifier in synchronous d-q rotating coordinates, and a new voltage feed forward decoupling compensation control strategy is proposed. The simulation results show that the voltage and current of the three-phase PWM rectifier have better respond preference, the current aberrance is smaller and the voltage is steady under the control strategy. The PWM rectifier can implement PWM commute with unity power factor, but also feed back the energy to AC side with unity power factor.

Machine Learning Methodologies for Prediction of Rhythm-Control Strategy in Patients Diagnosed with Atrial Fibrillation: Model Development and Comparison Study (Preprint)

2021 ◽  
Author(s):  
Rachel Soon-Yong Kim ◽  
Steve Simon ◽  
Brett Powers ◽  
Amneet Sandhu ◽  
Jose Sanchez ◽  
...  
Keyword(s):  
Machine Learning ◽  
Atrial Fibrillation ◽  
Control Strategy ◽  
Prediction Models ◽  
Rhythm Control ◽  
Machine Learning Algorithms ◽  
Support Tool ◽  
Wide Range ◽  
Complex Models ◽  
The Impact

BACKGROUND Identification of the appropriate rhythm management strategy for patients diagnosed with atrial fibrillation (AF) remains a major challenge for providers. While clinical trials have identified sub-groups of patients in whom a rate- or rhythm-control strategy might be indicated to improve outcomes, the wide range of presentations and risk factors among patients presenting with AF makes such approaches challenging. A strength of electronic health records (EHR) is the ability to build in logic to guide management decisions, such that the system can automatically identify patients in whom a rhythm-control strategy is more likely and promote efficient referrals to specialists. However, like any clinical decision-support tool, there is a balance between interpretability and accurate prediction. OBJECTIVE In this investigation, we sought to create an EHR-based prediction tool to guide patient referral to specialists for rhythm-control management by comparing different machine learning algorithms. METHODS We compared machine learning models of increasing complexity and using up to 50,845 variables to predict the rhythm-control strategy in 42,022 patients within the UC Health system at the time of AF diagnosis. Models were evaluated on their classification accuracy, defined by the F1 score and other metrics, and interpretability, captured by inspection of the relative importance of each predictor. RESULTS We found that age was by far the strongest single predictor of a rhythm-control strategy, but that greater accuracy could be achieved with more complex models incorporating neural networks and more predictors for each subject. We determined that the impact of better prediction models was notable primarily in the rate of inappropriate referrals for rhythm-control, in which more complex models provided an average of 20% fewer inappropriate referrals than simpler, more interpretable models. CONCLUSIONS We conclude that any healthcare system seeking to incorporate algorithms to guide rhythm management for patients with AF will need to address this trade-off between prediction accuracy and model interpretability.

Current predictive control of three-phase voltage source PWM rectifiers under unbalanced grid voltage conditions

2016 ◽  
Vol 39 (7) ◽  
pp. 976-986
Author(s):  
Meng Wang ◽  
Yanyan Shi ◽  
Zhen Qi ◽  
Minghui Shen
Keyword(s):  
Predictive Control ◽  
Control Strategy ◽  
Voltage Source ◽  
Phase Voltage ◽  
Two Phase ◽  
Grid Voltage ◽  
Three Phase ◽  
Pwm Rectifiers ◽  
Current Error ◽  
Unbalanced Grid

To improve the performance of three-phase voltage source pulse-width modulated (PWM) rectifiers (VSR) under unbalanced grid voltage conditions, a fixed-frequency current predictive control (CPC) strategy is presented. Instantaneous power of the three-phase VSR is analysed in a two-phase stationary frame. The calculation method for the reference current is improved to achieve the power stability at the AC side of the rectifier. Based on the current predictive model, the optimal duration of the voltage vectors is computed under the restricted condition of minimizing current error at α- and β-axes in fixed intervals. The control system is free of synchronous rotation coordinate transformation, and avoids positive and negative sequence decomposition, which simplifies the calculation. The simulation and experimental results show that the proposed control strategy is able to eliminate the AC current distortion effectively and depress DC link voltage fluctuation under unbalanced grid voltage. Furthermore, the control strategy has faster dynamic response ability, enhancing the control performance of the three-phase VSR system.

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