Introduction of Multi-functional Power Quality Improvement Energy Storage System to Power Systems

近年来，由于个人计算机和半导体生产设备等对电能质量敏感的设备增多，电能质量成为电力系统的重要问题。虽然有源滤波器是改善电能质量的最有效措施，但由于其存储的能量太小，无法控制有功功率。另一方面，从交流系统的角度来看，采用电压型逆变器的超导磁储能装置与有源滤波器具有相同的结构。因此，SMES可以像有源滤波器一样工作。本文利用EMTP-ATP对SMES的谐波电流补偿、电压暂降补偿、不间断电源(UPS)和三相平衡等改善电能质量的效果进行了研究。这些功能都是由基本相同的控制系统实现的。因此，这些功能中的几个是同时实现的。为了确保SMES的模型是由PWM变流器、直流可逆斩波和电感组成的EMTP来实现的。以EMTP-ATP模型为基础，给出了控制系统。仿真结果表明，该控制系统同时实现了上述几种功能。其次，研究了这些功能被激活时SMES的线圈电流。为了抑制谐波电流和平衡三相分量，发现线圈电流是振荡的，因为每相SMES的输出是不同的。虽然电压暂降补偿和UPS等其他功能需要很大的能量，但这些功能不需要很大的能量。然而，即使具有谐波电流补偿和三相平衡的功能，SMES也应该有大量的储能，以抑制线圈电流中的振动。

Power quality becomes the important problems of power systems recently due to the increase of the sensitive equipments to power qualities, such as personal computers and product facilities of semiconductors. Though the active filter is the most effective countermeasure for the power quality improvement, it cannot control the active power because its stored energy is too small. On the other hand, seeing form the AC system side, SMIES (Superconducting magnetic energy storage) with the voltage type inverter-converter unit has the same configuration as the active filter. Therefore, SMES can work as well as the active filter. The difference is its stored energy.In this paper, using EMTP-ATP, the effect of the power quality improvement by SMES, such as the harmonics current compensation, voltage sag compensation, UPS and three-phase balancing, is examined. These functions are achieved by the basically same control system. Therefore, a couple of these functions are achieved at the same time. To make sure, SMES is modeled on EMTP by PWM converter, DC reversible chopper and inductance. The control system is presented on MODELS of EMTP-ATP. Thus the simulation results are made clear that the control system achieves a couple of these functions at the same time.Next, the coil current of SMES is investigated when these functions are activated. To damp harmonics current and to balance three-phase components, it is found that the coil current is vibrating, because the output of SMES in each phase is different. Though the other functions such as voltage sag compensation and UPS need large energy, these functions do not need large energy. Nevertheless, even for the functions of harmonics current compensation and three-phase balancing, SMES should have amount of stored energy in order to damp the vibration in the coil current.