UPFC对动态电能质量影响的分析研究

Study of the Impacts of UPFC on Dynamic Power Quality

从动态电能质量的角度出发,分析UPFC对电能质量的影响。首先利用PSCAD/EMTDC软件包,建立了UPFC的动态模型,并分别考虑在系统遭受单相故障、输电线路雷击情况,安装UPFC和未安装UPFC情况下母线电压的电压偏移,研究结果表明UPFC可以有效减小故障后暂态过程中电压跌落的幅值和雷击后系统暂态过电压的振荡过程。然后,对系统谐波和UPFC之间的关系进行分析。研究结果表明UPFC的确向系统输入谐波,但可以通过提高PWM的载波频率并在UPFC两侧加滤波器,使谐波成分几乎可忽略;同时,UPFC对系统谐波又有很好的抑制作用,在系统产生谐波时,可以充当有源滤波器。

The ability of UPFC on transmission line has been widely approved because it integrates functions of series compensation, shunt compensation and phase-shift together. But it is obvious that UPFC itself is a harmonic source. From the point of view of dynamic power quality, the paper takes the influence of UPFC into account. Firstly, the dynamic model of UPFC is designed. Both the system with or without UPFC are simulated under the situations when a fault happened and a line was stricken by a lightning. Simulation results show the amplitude of voltage dip during the transient process is reduced, and the oscillation of transient over-voltage causing by lightning is damped. Then the relationship of UPFC and system harmonics is discussed. Although UPFC introduces harmonics into system, certain methods such as enhancing carrier wave frequency or filtering at both sides of UPFC, can reduce those harmonics to minute components.Moreover, when harmonics come from other part of the system, the UPFC will operate as an active power filter (APF) to suppress those harmonics.