Investigations on Power System Transfer Capability in Electricity Market

Abstract

The structure of the power system is undergoing the transition from a vertically integrated arrangement to the deregulated one to adapt to competitive market practices for the benefit of all the participants. However, the want of market participants for profit maximization is a security risk and threat to the reliable operation of the system. Accordingly, it becomes essential for the system operator to enumerate the Available Transfer Capability (ATC) of the network and earmark the same to the market applicants in a well-organized way. The optimal allocation of the Flexible Alternating Current Transmission Systems (FACTS) can be worked out to improve the power flow and minimize the losses. Among various FACTS devices, the series compensator namely Thyristor Controlled Series Capacitor (TCSC) can be utilized to compensate for line reactance and thus improve the ATC. In the present work, the allocation of TCSC has been accomplished by the Sensitivity and Power loss-based Congestion Reduction (SPCR) method. The SPCR method presents the technique of finding the optimal location of TCSC by computing the sensitivity of lines while utilizing the DC Power Flow Sensitivity Index and Reactive Power Loss Sensitivity Index after considering N-1 contingency. The reactive and real power losses along with real power flow are compared on the sensitive lines. With the placement of TCSC, the loadability of lines increases which ensures the relief of congestion on sensitive lines. The real power flows are analyzed by comparing the SPCR method with Power System Analysis Toolbox (PSAT). The efficacy of the proposed method is authenticated on 6-bus and 30-bus test systems. The Metaheuristic Evolutionary Particle Swarm Optimization (MEEPSO) is proposed to enhance the ATC considering line flow limits termed as Static ATC (SATC). MEEPSO resulted in a higher rate of convergence and helped in optimizing the value of SATC. The acceleration parameter is selected at 2. The minimum and maximum inertia weights are fixed at 1 and 1.2 respectively. The maximum compensation is limited to 50% of line reactance. The base case values of SATC are calculated using the Newton–Raphson load flow and the AC Power Transfer Distribution Factor (ACPTDF) are used under different transactions. The SATC value is then optimized using the MEEPSO method and compared with conventional techniques like the DC Power Transfer Distribution Factor (DCPTDF) technique. MEEPSO resulted in a higher rate of convergence and helped in optimizing the value of SATC by improving it through 25.85% and 9.34% as compared to DCPTDF and ACPTDF respectively for 6-bus system. These values were nearly 33% and 34% for 30-bus system. The performance of the developed algorithm in obtaining SATC values is compared with PWS. The results with PWS have been taken using Single Linear (SL) step solution technique. The system is divided into areas. The optimum cost of an individual case is calculated to visualize the influence of the modification in transactions amongst areas. The outcomes of the transactions are compared based on the above factors to obtain the economic operation. The ATC determined under dynamic stability limits is known as Dynamic ATC (DATC). The DATC has been calculated using the novice Single Machine Infinite Bus Eigen Area-based Modal Bifurcation (SEAMB) method and is executed using PWS by dividing the system into areas. The critical sensitivity is ascertained using eigen values. The three-phase faults are applied at the designated buses for 0.1s. The respective line is tripped at 0.15s and the simulation is performed for 5s. The DATC calculation is accomplished till the accurate Hopf Bifurcation (HB) point of eigen value is reached. A comparison between ATC values observed by taking static load and dynamic load is presented. The effectiveness and accuracy of the proposed method are verified on WSCC 9 bus as well as the New England 39 bus system.