Study On Application Of Dynamic Voltage Restorer

With the development of science and technology, the degree of automation in production is rapidly raising. Sensitive loads, such as computer and assembly equipments, have been applied in manufacture. The electric power customer's demand to power quality is rapidly growing. At present, Dynamic Voltage Restorer(DVR)is one of the most effective means to solve voltage sag problems. The paper analyzes main circuit, control methods of DVR, and some improvements have been achieved.Analyzing configuration of the main circuit, such as coupling cell, inverting cell, it indicates DVR coupled with series transformer and three phase bridge is a good choice. Compared feed forward control with feedback control, it indicates feed forward control has the advantages of fast response and simple control, but poor adaptability to loads, and feedback control has the advantages of wider stability margin, but slow response.A solution of installing DVR matching loads in each bus to Tianjin Pipe Corporation about DVR is proposed. While loads are switching, DVR works on mechanical bypass state. It both maintains loads voltage in each bus and reduces costs. The solution has the advantages of less harmonics, high reliability, expandable capacity, high efficiency and so on, but limited voltage rating, high costs, tediously control.Improving DVR application programs, the thesis introduces DVR coupled with transformer to improve voltage rate and proposes control strategy to inhibit inrush current. This paper presents a new concept of interline dynamic voltage restoration (IDVR) that two or more DVRs in different feeders are connected to a common dc link. While one of the DVRs compensates for voltage sag, the other DVRs connected to a common dc Link replenish the dc-link energy storage. The efficacy of the proposed IDVR system is verified by simulation results for a simple system. According to the theory of active-disturbance rejection controller(ADRC),a novel nonlinear controller of DVR is designed. The uncertainties in the model and from the circumstance outside are both evaluated by the expending state observer. With the nonlinear state error feedback control law, the disturbance can be compensated. The control law has only relationship with the reference and the output. So the controller is simplified with fewer variables to be detected and the cost is lower. The feasibility adaptability and robustness of the control are testified with parameter uncertainly and outside disturbance.Transformer separate experiment and system series experiment have been conducted on the rebuilt single phase transformer coupling DVR prototype. Finally, the experiment results demonstrate that the applied control strategies can compensate the voltage sags effectively under transformer inrush situation, with good transient and steady-state responses and load adaptability.