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The modeling, modulation and control of the three-phase four-switch (TPFS) PWM rectifier are investigated in this paper. Three space vector pulse width modulation methods using different equivalent zero vectors are developed, where sector identification and the trigonometric function are not required. Then, the high frequency model for the current ripple analysis is proposed, and the effects of three SVM approaches on the AC current ripple are investigated. According to the analytical results, the method introducing the smallest current ripple is selected. With the optimized SVM approach, a control-oriented model, considering the capacitor voltage oscillation and deviation, is built in the d-q synchronous frame to facilitate the controller design. Furthermore, a control strategy implementing the proportional controller is developed to eliminate the capacitor voltage deviation. Meanwhile, the dual-loop control of the TPFS is not affected by the proposed strategy as the capacitor voltage deviation is eliminated. Finally, a novel linear modulation index function is defined to reject the low frequency harmonic current introduced by the overmodulation. Experimental results demonstrate that excellent current performance is achieved with comprehensive considerations of the modeling, modulation and control strategy.Index Terms-AC-DC power rectifiers, space vector modulation (SVM), three-phase four-switch (TPFS), current ripple root mean square (RMS), linear modulation. 0885-8993 (c)

Room temperature hydrophilic ionic liquids, 1-methyl-3-ethylimidazolium salts containing ethyl-sulfate anions, have dramatic effects on the morphology changes of electrochemically grown Cu 2 O crystals at room temperature in aqueous solutions. The shape of Cu 2 O crystals evolves from cubic to octahedral and spherical shape only by adding a varied small amount of the ionic liquids in the deposited solutions. The possible mechanism has been explored, and the ethyl-sulfate anion is believed to play a key role in the morphology control.

Multi-functional grid-connected inverters (MFGCIs) not only interface renewable energy sources into the utility, but also provide ancillary power quality enhancement service. Therefore, extra installment of power quality conditioners can be partially avoided in a micro-grid including MFGCIs. Because the capacity of an MFGCI employed for power quality compensation is limited, how to balance the multiple functions and optimally utilise the limited capacity becomes a challenging for MFGCI application, and this is studied in details in this paper. First, to set up a benchmark for balancing the multiple functions of the MFGCI, a comprehensive power quality evaluation (CPQE) index is presented based on the catastrophe decision theory to quantify the power quality of a micro-grid. Then, for the strategic utilisation of the limited capacity, a multi-objective optimal compensation model is proposed in which the objectives are to optimise the CPQE index and minimise the occupied capacity of an MFGCI for power quality compensation. Finally, the solutions of the model are derived on the basis of Pareto approach. As a result, the MFGCI can flexibly customise the power quality of the micro-grid according to its available capacity margin and the users' requirement. Finally, the experimental results performed on a 10 kVA MFGCI prototype have confirmed the validity of the proposed model.

Owing to the numerous non-linear and reactive local loads, the applied grid-tied inverters etc., the quality of power supply of micro-grids becomes a challenging issue need to be highly addressed. As the power quality can significantly affect the secure, stable, effective and economic operation of the micro-grids, the compensation of the harmonic and reactive current in the micro-grids by the use of power quality conditioners and/or advanced control strategies has been highlighted. In this study, the multi-functional grid-tied inverters (MFGTIs) are attempted to interface renewable energy resources and enhance the power quality within the micro-grid. The MFGTIs encompassed with the coordinated control strategy based on the Fryze-Buchholz-Dpenbrock (FBD) theory. Through limiting the harmonic and reactive conductance and susceptance detected by FBD theory, the harmonic and reactive current within the micro-grid can be shared among the MFGTIs in a coordinated and automatic fashion in accordance with their capacities without communication. A set of the experiments based on the microgrid test-bed are carried out and the results confirm the effectiveness and feasibility of the suggested control strategies.

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