A Versatile Control Scheme for a Dynamic Voltage Restorer for Power-Quality Improvement

This paper presents a control system based on a repetitive controller to compensate for key power-quality disturbances, namely voltage sags, harmonic voltages, and voltage imbalances, using a dynamic voltage restorer (DVR). The control scheme deals with all three disturbances simultaneously within a bandwidth. The control structure is quite simple and yet very robust; it contains a feedforward term to improve the transient response and a feedback term to enable zero error in steady state. The well-developed graphical facilities available in PSCAD/EMTDC are used to carry out all modeling aspects of the repetitive controller and test system. Simulation results show that the control approach performs very effectively and yields excellent voltage regulatio

The maximum fluidity length of solidifying Sn-Cu-Ag-Ni solder alloys

During wave soldering, it is important that a solder is able to flow easily to fill joints and to drain away to leave tidy fillets. The maximum fluidity length (L ) is a simple measure of the flow behavior of solidifying alloys, defined as the distance a cooling and solidifying alloy can flow in a constant cross-section before the developing microstructure arrests flow. This paper explores the influence of alloy composition on L in Sn-rich Sn-Cu-Ag-Ni alloys with compositions relevant to wave soldering. Significant differences in L are measured among candidate lead-free solder alloys, which are discussed with respect to the phase diagrams and the mode of solidification