Research On Series Voltage Transient Variation Compensator And Its Dtection And Control Strategies

Along with the development of modern technology, power customer has more and more severely requests of power quality. But in recent years, after the widely use of power electronics equipments and influence of the special loads such as electric arc stove and electros railroad, the pollution in power system became much more serious than before. So improving and controlling power quality became an important task for modern system. In this case, a new technology known as Custom Power came forth and became the most important and effective method to improve power quality at present.First of all, the basic concept of power quality is introduced. Aiming at transient variations of voltage magnitude, which is one of the power quality issues, the background and actuality in the area are introduced. Then in this paper, a transformer-less series voltage transient variation compensator topology without energy storage capacitors is analyzed. This topology is cost-effective by eliminating the large injection transformer and energy storage capacitors that are used in conventional series injection devices. This topology can both be used in three-phase three-line and three-phase four-line systems, and can compensate symmetrical three-phase voltage sags down to 37%, or one or two phase sags down to zero if others at least one phase is rated.In order to conquer the disadvantage of the higher DC link voltage and the higher resistence voltage the switch need. A novel method of controlling the DC link voltage is proposed in this paper. Then, the paper analyzes the control system in detail, including the closed-loop tracking control design. Then, the detection method and the control strategy, which are the important parts affecting the compensation effect of the system, are discussed and investigated in detail in the thesis. This paper adopts one kind of method for detecting the three-phase voltages respectively. This paper analyzes the principle of creating the rated voltage signal and the issues of phase locked technique during creating the three-phase reference voltages respectively. In addition, the paper use FPGA which is the Cyclone II series in Altera company to realize the detection and some control issues. The simulation and the experiment results are given at last.According to the research results, the proposed transformer-less series voltage variation compensator topology can compensate deep voltage variation and has a good performance. By using the mentioned detection method can shorten the delay during the detection.