## 6 Congestion Management
Similarly, in [202] the authors also validate the effectiveness of combined TCSC and SVC performance to reduce congestion in the IEEE-14 bus system. Similarly, detailed research on the IEEE-30 bus system with the help of a new meta-heuristic algorithm using a combination of TCSC-SVC-HVDC devices, which reduces congestion in terms of reducing transmission line loss and increases load ability, is presented in [203]. The result showssignificant improvement in the power system using the proposed approach (the TCSC as series compensator and the SVC as a parallel compensator). More FACTS devices like the UPFC and IPFC also reduced congestion in power networks. In the literature [204,205], the UPFC and TCSC are implemented to reduce congestion and generation cost. It is further concluded that the TCSC performs better than the UPFC to improve power flow in a deregulated power system [205]. The UPFC also reduced congestion by rescheduling real power of generators in the New England 39 bus network and Indian 75 bus system [206]. Consequently, congestion in power systems increased with the integration of renewable energy resources into existing networks. Based on this, a study of a 110 kV distribution system using UPFCs to reduce congestion was presented in the literature [207]. In addition, a parallel tempering approach as well as a greedy algorithm are used to optimize UPFC devices in terms of their size, their number and placement in the power system, control parameters, and cost. Results show that an optimally placed UPFC power flow control can reduce congestion by 99.13%. Like the UPFC, the IPFC is also used to relieve congestion in power systems. A constriction factor-based particle swarm optimization analysis is used with IPFCs to reduce congestion in the IEEE-30 bus system under different loading and contingency situations. In [208], an IPFC is optimally sized in the IEEE-30 bus system and in [209] an IPFC is optimally placed in the IEEE-30 bus system to reduce cost and mitigate congestion. Similarly, the IPFC reduced congestion (by improving power flow and voltage profile) in the Nigerian 41 transmission network [210] and, in [211], an IPFC is optimally placed in Ethiopian Electric Power 400 kV to enhance the average line severity index. In [212], the authors compare single and combined FACTS devices (UPFC, TCSC, and SVC) that were used to reduce congestion in IEEE-6, 30, and 118 bus systems and the Tamil Nadu Electricity Board (TNEB) 68 bus system by enhancing system load-ability with minimum cost of installation. It is observed that the SVC offers the lowest cost of installation with the lowest system load-ability improvement as compared to other FACTS devices in IEEE-30 and 118 bus systems. However, the cost of installation is high in the case of UPFCs but provides maximum improvement in system load-ability in IEEE systems. However, the TCSC performs better with minimum installation cost. In addition, for TNEB (a practical bus system in India), the TCSC provides maximum load-ability with minimum installation cost compared to the UPFC and SVC. Furthermore, in [213] a GA-based graphical interface is presented to provide congestion management by optimally placing FACTS devices in large power systems. Therefore, researchers implemented five different FACTS devices (UPFC, TCPST, TCVR, TCSC, and SVC) to provide static system load-ability in an IEEE bus network (up to 300 buses). It is observed that the UPFC is the most effective FACTS device as compared to other FACTS devices in terms of increased load-ability while reducing loss at the same time in large power systems. However, it is further concluded that system load-ability increased by increasing the number of FACTS devices in interconnected power systems. Another comparison study [214] for FACTS devices (UPFC, SSSC, and STATCOM) has been carried out by optimal rescheduling of generators' output and thereby the congestion cost in the IEEE-24 and 57 bus systems. Results show that the UPFC enhanced the load-ability margin of power systems more than the SSSC and STATCOM.