Research On Unified Power Quality Conditioner With Nine Switch

With the increasingly wide applications of non-linear and time-varying power electronic devices, grid harmonics and reactive power problem are getting nonignorable. In the mean time, power quality requirements of sensitive electrical equipment are getting higher and higher, consequently, how to control power quality comes to be a problem demanding prompt solution. Unified Power Quality Conditioner, which can comprehensively manage a variety of power quality problems appearing in gird, is an important apparatus to govern the problems related to power quality with theoretical significance and good engineering applications.First of all, due to the traditional back-to-back UPQC needs more switch device, higher production costs and low power density, and based on analysis of a variety of new converter, this design selected nine switching converter. Besides,nine switching converter can not only reduce the number of switches but also can achieve independent control of its two AC ports by rational controlling.Secondly, on the basis of studying nine switching UPQC the circuit topology,this paper built the mathematical model of the nine switching unified power quality conditioner, and established a d-q comprehensive detection method of voltage and current based on Park transformation, DC voltage control method, and the specific SPWM modulation method of whole nine switch control block and the overall control block of nine switching Unified Power Quality Conditioner as well. Then this paper built the simulation model of nine switching UPQC and back-to-back UPQC with Matlab Simulink application. Simulation results showed that nine switching UPQC can successfully achieve traditional back-to-back UPQC’s performance and comprehensive management of a variety of power quality.Finally, for the relatively high DC voltage problem of nine switching UPQC, a method of connecting single-tuned filter branch in series with nine switching Unified Power Quality Conditioner equivalent parallel side has been put forward and by reducing the AC grid fundamental component on its equivalent parallel side,the magnitude of nine switching UPQC DC-side voltage was proved to be feasible,and the simulation also showed that the method is feasible and effective.This study shows that nine switching UPQC can not only comprehensively manage all types of power quality problems, but also demonstrate its own advantages in its cost and device volume.