The development of FACTS devices based on the advance of semiconductor technology opened up new opportunities for controlling the power flow and extending the load ability of the power transmission network. Amongst the various FACTS devices, the UPFC is considered the most versatile FACTS device that can simultaneously control bus voltage and both active and reactive power flow through the transmission line. This chapter discusses the implementation of grey wolf optimization (GWO), teaching-learning-based optimization (TLBO), biogeography-based optimization (BBO), krill herd algorithm (KHA), chemical reaction optimization (CRO), and hybrid CRO (HCRO) approaches to find the optimal placement and parameter setting of unified power flow controller (UPFC) to achieve the optimal performance of optimal power flow (OPF) and optimal reactive power dispatch (ORPD) problems. Two test systems, namely IEEE 14-bus and IEEE 30 with valve-point non-linearity, are considered to demonstrate the effectiveness of proposed approaches.
TopIntroduction
The electric power grid is the largest man-made machine in the world. It consists of synchronous generators, transformers, transmission lines, switches and relays, active/reactive components, and loads. Power system networks are complex systems that are nonlinear, non-stationary, and prone to disturbances and faults. Reinforcement of a power system can be accomplished by improving the voltage profile, increasing the transmission capacity and others. Nevertheless, some of these solutions may require a considerable investment that could be difficult to recover. Installation of FACTS devices in optimal position is one alternate to address some of those problems (Hingorani & Gyugyi, 2001).
Optimal reactive power dispatch (ORPD), a sub problem of optimal power flow (OPF), has a significant influence on the economic and secure operation of power systems. Optimal reactive power dispatch (ORPD) is an important tool for power system operators for both planning and reliable operation in the present day power systems. The important aspect of ORPD is to determine the optimal settings of control variables for minimizing transmission loss, improve the voltage profile and voltage stability, while satisfying various equality and inequality constraints. The ORPD problem is in general non-convex, non-linear and exists many local minima.
In the view of the above, the main objective of this chapter is to propose new, efficient optimization techniques to locate various FACTS devices in an optimal position in order to minimize transmission loss and voltage stability of short, medium and large-scale power systems. There are a number of FACTS devices available, such as, the static synchronous series compensator (SSSC) (Basu, 2008; Vijayakumar & Kumudinidevi, 2008) which can be used to generate and insert a series voltage, and it can be regulated to change the impedance of the transmission line. In this way, the power flow of transmission line, where the SSSC is connected is controlled. Similarly, Static synchronous compensator (STATCOM) is connected in parallel with the power system which can be controlled the power flow of the transmission line. UPFC is the most versatile FACTS device which can simultaneously controls the active power and the reactive power of the bus voltage at which it is connected (Gyugyi, 1992). It is used in the transmission system to reduce the flows in heavily loaded lines, resulting in increased load ability, low system loss and improved stability of transmission system by controlling the power flows in the network.