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

随着个人计算机和半导体产品设备等对电能质量敏感的设备的增多，电能质量成为电力系统的重要问题。有源滤波器虽然是改善电能质量最有效的对策，但由于有源滤波器储能过小，无法控制有源功率。另一方面，从交流系统方面来看，具有电压型逆变-变换器单元的超导磁能存储（SMIES）具有与有源滤波器相同的配置。因此，SMES可以像有源滤波器一样工作。不同之处在于它储存的能量。本文利用EMTP-ATP分析了中小企业采用谐波电流补偿、电压暂降补偿、UPS和三相平衡等措施改善电能质量的效果。这些功能是由基本相同的控制系统实现的。因此，这两个功能是同时实现的。为此，采用PWM变换器、直流可逆斩波器和电感对EMTP进行建模。在EMTP-ATP模型的基础上提出了控制系统。仿真结果表明，该控制系统同时实现了上述几个功能。接下来，研究了这些功能被激活时SMES的线圈电流。为了阻尼谐波电流和平衡三相分量，发现线圈电流是振动的，因为每个相位的SMES输出是不同的。虽然电压暂降补偿、UPS等其他功能需要大量的能量，但这些功能并不需要大量的能量。然而，即使对于谐波电流补偿和三相平衡的功能，SMES也应该有一定的储能，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.