Day-Ahead Corrective Adjustment of FACTS Reactance: A Linear Programming Approach

Abstract

Abstract-Reserve requirements serve as a proxy for N-1 reliability in the security-constrained unit commitment (SCUC) problem. However, there is no guarantee that the reserve is deliverable for all scenarios (post-contingency states). One cheap way to improve reserve deliverability is to harness the flexibility of the transmission network. Flexible AC transmission system (FACTS) devices are able to significantly improve the transfer capability. However, FACTS utilization is limited today due to the complexities these devices introduce to the DC optimal power flow problem (DCOPF). With a linear objective, the traditional DCOPF is a linear program (LP); when variable impedance based FACTS devices are taken into consideration, the problem becomes a nonlinear program (NLP). A reformulation of the NLP to a mixed integer linear program, for day-ahead corrective operation of FACTS devices, is presented in this paper. Engineering insight is then introduced to further reduce the complexity to an LP. Although optimality is not guaranteed, the simulation studies on the IEEE 118-bus system show that the method finds the globally optimal solution in 98.8% of the cases. Even when the method did not find the optimal solution, it was able to converge to a nearoptimal solution, which substantially improved the reliability, very quickly.Index Terms-FACTS devices, linear programming, power system reliability, power transmission reliability, transfer capability, transmission topology optimization.

Review of Trends and Targets of Complex Systems for Power System Optimization

“…Flexible AC transmission system (FACTS) devices are modern power flow control equipment used in transmission systems (TS). OSs in [88][89][90][91][92] maximize the transmission capacity of TS's power lines by changing the FACTS settings. An OS in [93] determines the locations in the TS where it would be optimal to install FACTS to optimize the TS power flows while there are many wind turbines connected to the TS.…”

Contribution of FACTS devices in power systems security using MILP‐based OPF

“…It is expected that FACTS devices could increase the transfer capability over the existing transmission lines by 50% [4,9], if deployed optimally. Major challenges that prevent better utilisation of FACTS devices in power systems are computational complexities of incorporating these devices in ACOPF problem [9][10][11]. In general, the ACOPF problem incorporating FACTS devices is a large-scale non-convex optimisation problem [11].…”

“…Moreover, the formulation developed in [11,13] is computationally expensive and will not be applicable to large-scale power systems. A mixed-integer linear program (MILP)-based DC OPF model is proposed in [9,10] to provide suggestions to the operator regarding the operation of FACTS devices and upgrading the usage of transmission capacity. Moreover, in [9], the TCSC device has been included in the DC optimal power flow problem (DCOPF).…”

Impacts and benefits of UPFC to wind power integration in unit commitment

“…The results show that the installation of FACTS devices can improve power flow and reduce transmission line losses. A UC model considering FACTS devices for corrective operation is proposed in [24]. The original mixed-integer non-linear problem is reformulated as an mixed-integer linear problem.…”

“…It is more general and can easily be used to model other types of FACTS devices. In [24], a linear programming approach is proposed to reduce computational complexity. However, only DC power flow is considered.…”