Research And Development On The Three-phase Intelligent Voltage Quality Controller Based On VSC

On the one hand, with the larger scale of the grid and more integration of nonlinear loads,voltage quality become worse, such as three-phase unbalance, voltage variation, fluctuationand flicker, harmonic, sag, etc. These problems cause huge impact on the consumers. On theother hand, with the development of society and economy, power consumers demand onbetter voltage quality. At the same time, the utilities present strict voltage qualification rate.As a consequence, an integrated solution to all kinds of voltage quality problems is needed toimprove the voltage quality and provide power consumers with reliable, good quality ofpower supply. The thesis researched and developed a three-phase intelligent voltage qualityconditioner based on voltage source converter (VSC). The device can mitigate all thesteady-state voltage quality problems. The main works are given as follows.Firstly, the topology of the three-phase intelligent voltage quality device based on VSCwas designed according to the requirements of the voltage quality control; the principle ofvoltage quality control was presented; and mathematic models of the device in the domainwere established in the three-phase stationary coordinates and two-phase synchronous rotarycoordinates.Secondly, the control strategies of the device were proposed based on the mathematicalmodel. The overall control strategy is composed of two parts: double-loop control in rectifier,which consists of DC voltage outer loop and double-loop control used in inverter, whichconsists of AC voltage outer loop and AC current inner loop. The key technologies of thedevice’s control strategies in the physical implementation process were given, including softstart technology, outage control, and space vector pulse width modulation (SVPWM).Thirdly, the experiment test platform of the device was developed. The parameterscalculation methods and principles of selection of elements in the main circuit were studied.The detail types of the element were selected. The controller hardware circuit was designedand realized based on TMS320F28335. The modularization software system of the controllerwas developed independently.Finally, the function and performances of the device were verified by the experimentsunder different conditions, specifically including three-phase unbalance, harmonic, voltagedeviation and fluctuation. The experiment results show that the device solved thesesteady-state voltage quality problems effectively, and achieved the voltage quality controlfunctions. This device was also of many advantages, for example, high power factor, lowinput current harmonics, fast dynamic response, and strong ability to resist load disturbance. The results of the study provide a new idea to solve the grid voltage problemscomprehensively.The paper is supported by the Natural Science Foundation of China (No.51007024).