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Pervious concrete (PC) pavements can effectively reduce surface runoff, but it will be clogged with time and its service life will be affected. In this study, based on three groups of PC specimens with different aggregate gradations optimized by previous experiments, the pavement-clogging simulation test is carried out using the two-way coupling of the particle flow code with computational fluid dynamics (PFC-CFD). The results show that when the gradation of aggregates in the pervious pavement is different, the volume fraction of clogging material in the pavement and the time when the volume fraction of the clogging material reaches the maximum are also different. It is related to the zigzag degree and size of the pore in the pervious pavement. The smaller the particle size of coarse aggregate in the pervious pavement, the easier it is to be clogged, and the discontinuous graded coarse aggregate has a good shielding effect on the clogging material. Different clogging material gradations have different effects on the clogging of pervious pavements. According to the aforementioned research results, researchers can select different mix ratios of anti-clogging PC according to different areas of use. The law obtained from the experiment can provide a reference for further study of the double-layer pervious pavement structure design.

Abstract Solid‐state transformer (SST) is an attractive concept, which provides galvanic isolation and voltage scaling by means of a medium‐frequency link. In this paper, a single‐stage alternative current (AC)‐AC SST solution without bulky energy storage elements is presented. The front‐end rectifier (FER) and rear‐end inverter (REI) of the SST works at line‐frequency, while the intermediate LLC series resonant converter (SRC) fulfils the tasks of galvanic isolating and regulating the output voltage. To achieve high efficiency and bidirectional power flow capability of the SST, the zero voltage switching (ZVS) condition of the LLC SRC is comprehensively analysed, and the parameters design method of the LLC SRC is developed, where the resonant currents are constructed by applying the same gating signals to the primary‐side and secondary‐side bridges and the dead‐time is properly selected. Consequently, the presented SST has the merits of high conversion efficiency, naturally bidirectional power flow capability, potentially high power density and high reliability. The experimental results on a 1.5 kW SST prototype show that sinusoidal input and output current, ZVS operation over the full load range are achieved, and the peak efficiency is 97.63%. The experimental results verify the functionality and effectiveness of the developed methods.

In the wind energy generation system, the brushless doubly-fed induction machine (BDFIM) has shown significant application potential, since it eliminates the electric brush and slip ring. However, the complicated rotor structure increases the control difficulty, especially resulting in complicated coupled terms in the current sub-system, which deteriorates the dynamic performance and reduces the system robustness. In order to address the problems caused by complex coupled terms, an internal model current control strategy is presented for the BDFIM, and an active damping term is designed for suppressing the disturbance caused by the total resistance. The proposed method simplifies the controller parameters design, and it achieves the fast-dynamic response and the good tracking performance, as well as good robustness. On the other hand, the feedforward term composed by the grid voltage is added to the internal model controller in order to suppress the disturbance when the symmetrical grid voltage sag happens. Finally, the simulation and experimental results verify the feasibility and effectiveness of the proposed method.

The relatively low-linear voltage transfer ratio (VTR) is considered an intrinsic drawback of the conventional two-stage matrix converter (TSMC). However, the studies demonstrate that the linear VTR of the third-harmonic injection TSMC (3TSMC) can push this limit. After reviewing the operating principles and modulation strategy of 3TSMC briefly, the VTR characteristic of 3TSMC is analysed and a control method to enhance the linear VTR is proposed. With the developed method, the maximum linear VTR can break through the intrinsic limit and VTR > 0.866 can be achieved by regulating the input reactive power under arbitrary output conditions theoretically. Finally, simulations and experimental results verify the correctness of the theoretical analysis, and the comparison of 3TSMC and other TSMCs with improved VTR demonstrates the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This study presents an active third-harmonic injection indirect matrix converter (3HI2MC) topology with dual three-phase outputs. The presented 3HI2MC has the advantages of sinusoidal input and output currents, bi-directional power flow, and can provide two sets of three-phase outputs, whose frequencies and amplitudes can be regulated independently. Compared with the conventional indirect matrix converter (IMC), the input reactive power control range is extended significantly, and the converter can even work as a static compensator. Moreover, a maximal voltage transfer ratio of 0.866 is achievable under all operation conditions. Furthermore, operations of the rectifier and inverters are independent. Thus, for a 3HI2MC system containing multiple voltage-source-type inverters (VSIs), modulation and control task can be implemented flexibly by a separate controller for each VSI, while it is difficult for the conventional IMCs to achieve such a goal. All of the features above make 3HI2MC competitive for the applications that require multiple three-phase outputs such as multiple drives. After describing the topology structure, operating principles and control algorithm in detail, simulation and experimental results are presented to demonstrate the validity and effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

To improve the input and output waveform quality in terms of total harmonic distortion (THD) for the three-level diode-clamped matrix converter topology, the phase disposition carrier-based modulation method is a good option. However, it is difficult to implement because of the loss of zero-current commutations. Aiming at addressing the problem above, a hybrid switching sequence for the phase disposition method is presented to realise the safe commutation, and a prediction-based method is used to alternate the switching sequences. The current direction information of the switches in cascaded rectifier for commutations is obtained by a current reconstruction method. As demonstrated by experimental results, the phase disposition method contributes to lower input and output waveforms THD values compared with the phase opposition disposition method. [ABSTRACT FROM AUTHOR]