1、 PDF外文：http:/ 外 文 文 献 翻 译 专业 电气工程及其自动化 学生姓名 陈嘉俐 班级 BD 电气 071 学号 0720601103 指导教师 胡国文 电气工程学院 Compensation of Voltage Sags and Swells using a Single-Phase AC-AC Converter Abstract-In this paper, a topology to compensate voltag
2、e sags and swells simultaneously in critical loads is proposed. It consists in a single-phase AC-AC converter in a matrix arrangement, which keeps a continuous regulation in the output voltage. The proposed scheme has the capability to compensate up to 25% voltage sags and 50% voltage swells.
3、Energy storage devices are not required by the AC-AC converter and it is connected between the AC mains and the load by using a series transformer. One of the advantages of this topology is that taps for the coupling transformer are no necessary to change the polarity of the compensation voltage. A
4、four step switching technique is used to drive the AC-AC converter switches, executing snubber-less operation. The reference signal is generated using single-phase d-q theory, obtaining a fast response time and high regulation. Simulation and experimental results of a 5kW capacity, 127V, 60Hz
5、equipment are presented. I.INTRODUCTION The quality of the AC mains has been affected by the use of new semiconductor-devices technologies. Nowadays, it is common to find disturbances in the amplitude or waveform shape of current and voltage in the electric systems. These conditions could prod
6、uce fails in the equipments, raising the possibility of an energy interruption. The voltage fast variations that appear in the AC mains during 10 seconds or less are commonly known as voltage sags and swells. These variations are produced by normal operation of high power loads as well as thei
7、rs connection and disconnection； the voltage fast variation effects are function of the amplitude and the duration of the event. Some studies show that 92% of all disturbances in the electrical power distribution systems are produced by voltage sags 1. It is important to eliminate the voltage fast v
8、ariations because they are the most frequently cause of disrupted operations for many industrial processes, particularly those using modern electronic equipment, which are highly sensitive to short duration source variations 2. Dynamic Voltage Restorer(DVR) and Uninterrupted Power Supply (UPS)
9、 systems had been researched and developed along the last decades and they are capable to compensate voltage sags and swells. Nevertheless, they depend on devices to store energy, like large capacitors or batteries bank. The nominal power operation is a function of size and capacity of those d
10、evices； if the power is increased, the size of the devices will increase. In spite of the above, the UPS systems are capable to support energy interruptions. Other option developed, which is able to compensate voltage sags is based on PWM AC-AC converter3,4.This solution uses an autotransformer comp
11、osed by one primary side and two secondary windings presenting a good performance. The system compensates until 50% voltage sags and swells and can continuously shape the output voltage to be sinusoidal (with low THD). Nevertheless, the autotransformer drives all the load power due to it is connecte
12、d between the load and the AC mains. In this paper a PWM AC-AC converter is presented, in order to compensate voltage sags and swells simultaneously in critical loads, and to maintain a continuous regulation in the output voltage. The system consists in a single-phase AC-AC converter in a matrix arr
13、angement, and energy storage devices are not required. A four step switching technique is used to drive AC-AC converter switches, executing snubber-less operations. The reference signal is generated using single-phase d-q theory, obtaining a fast response time and continue regulation, with a h
14、igh efficiency. One of the advantages in this structure is that the taps of the coupling transformer are not required to change the polarity of the compensation voltage, and the converter drives only a percent of the load power. Design, construction and performance are detailed, and several simulations and experimental results obtained with a laboratory prototype are showed to validate the approach. II.CONVERTER ANALYSIS The structure of the proposed approach is shown in Fig. 1.
