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A model-free direct predictive grid-current control strategy for grid-connected converter with an inductance-capacitance-inductance filter

Guo Leilei, Zheng Mingzhe, Yu Changzhou, Xu Haizhen, Li Yanyan

Archives of Electrical Engineering

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2023

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Vol. 72, nr 1

23--42

EN

The disadvantages of the conventional model predictive current control method for the grid-connected converter (GCC) with an inductance-capacitance-inductance (LCL) filter are a large amount of calculation and poor parameter robustness. Once parameters of the model are mismatched, the control accuracy of model predictive control (MPC) will be reduced, which will seriously affect the power quality of the GCC. The article intuitively analyzes the sensitivity of parameter mismatch on the current predictive control of the conventional LCL-filtered GCC. In order to solve these issues, a model-free predictive current control (MFPCC) method for the LCL-filtered GCC is proposed in this paper. The contribution of this work is that a novel current predictive robust controller for the LCL-filtered GCC is designed based on the principle of the ultra-local model of a single input single output system. The proposed control method does not require using any model parameters in the controller, which can effectively suppress the disturbances of the uncertain parameter variations. Compared with conventional MPC, the proposed MFPCC has smaller current total harmonic distortion (THD). When the filter parameters are mismatched, the control error of the proposed method is smaller. Finally, a comparative experimental study is carried out on the platform of Typhoon and PE-Expert4 to verify the superiority and effectiveness of the proposed MFPCC method for the LCL-filtered GCC.

2

Shear behavior and analytical model of T-type perfobond rib connectors

Zhan Yulin, Huang Wenfeng, Li Yanyan, Zhang Cheng, Shao Junhu, Tian Bo

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e150, 2023

EN

The stress of shear connectors becomes more complicated with the increase of the span length of steel–concrete composite bridges. To ensure sufficient stiffness and ductility, a T-type perfobond rib (T-type PBL) shear connector is proposed. However, its mechanical behavior is not well understood due to the special shape and numerous influencing factors. Therefore, sixty-three finite element models were established based on the push-out test specimens with T-type PBL connectors to investigate the shear behavior and influencing parameters of ultimate bearing capacity. The effects of concrete end-bearing, perforated reinforcement, hole diameter, rib height, and flange width of T-type PBL on the shear-bearing capacity were performed and discussed based on the numerical results. The results showed that the bearing capacity provided by the concrete end-bearing and the perforated reinforcements was about 16% and 10% of the ultimate load. Additionally, the ductility of the specimen could be improved by the perforated reinforcements. It was showed that the shear-bearing capacity increased nonlinearly with the growth of the hole diameter. When the height of rib increased from 80 to 120 mm, the shear-bearing capacity was improved by 12% on average. The impact of flange width on the shear-bearing capacity was insignificant, which was less than 1.5%. Based on the results of parametric analysis. An analytical model for shear-bearing capacity of the T-type perfobond rib shear connector was established, and the validity was verified by relative test results. A basis for the evaluation of shear-bearing capacity, and application of the T-type PBL connectors was provided in this paper.

3

Model predictive control of NPC three-level grid-tied converter based on reconstructed current

Li Yanyan, Xiao Han, Jin Nan, Yan Guanglu

Archives of Electrical Engineering

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2022

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Vol. 71, nr 2

363--377

EN

The neutral point clamped (NPC) three-level grid-tied converter is the key equipment connecting renewable energy and power grids. The current sensor fault caused by harsh environment may lead to the split of renewable energy. The existing sensor fault-tolerant methods will reduce the modulation ratio index of the converter system. To ensure continuous operation of the converter system and improve the modulation index, a model predictive control method based on reconstructed current is proposed in this paper. According to the relationship between fault phase current and a voltage vector, the original voltage vector is combined and classified. To maintain the stable operation of the converter and improve the utilization rate of DC voltage, two kinds of fault phase current are reconstructed with DC current, normal phase current and predicted current, respectively. Based on reconstructed three-phase current, a current predictive control model is designed, and a model predictive control method is proposed. The proposed method selects the optimal voltage vector with the cost function and reduces time delay with the current reconstruction sector. The simulation and experimental results show that the proposed strategy can keep the NPC converter running stably with one AC sensor, and the modulation index is increased from 57.7% to 100%.