An Active Voltage Quality Regulator with variable dc-bus voltage topology
The active voltage quality regulator (AVQR) is an equipment designed to mitigate the long-term voltage disturbance, such as undervoltage, overvoltage and voltage harmonics etc. For the existing AVQR topology, the dc-bus voltage is either uncontrolled or controlled to a constant value, and it can not vary with the missing voltage variation. When the missing voltage is small, the corresponding and required dc-bus voltage should be small as well. But in the existing topology, the dc-bus voltage usually keep very high. Therefore, the duty ratio of the inverter is very small and then the efficiency is very low. In order to overcome its drawbacks, a new AVQR topology is proposed in which the diode-rectifier is replaced by the thyristor-rectifier in this paper. Then for the sake of show the advantage of the proposed topology, the dc-bus voltage in the both topologies (uncontrolled or controlled) are compared by simulations. Through comparative analysis, the proposed topology is proven to be better than the existing topology, especially on a large missing voltage variation. At last, the validity and effectiveness of the proposed topology and control strategy are also verified by the laboratory experimental results. In a case, under the same supply voltage and load conditions, the efficiency increases from 89.1% of uncontrolled dc-bus voltage to 96.1% of controlled dc-bus voltage on a 2 kVA prototype, so the efficiency is increased significantly.