Alleviation of line overloads and voltage violations by corrective rescheduling P.R. Bijwe DP. Kothari L.D. Arya Indexing terms: Overloads, Voltage violation, Corrective rescheduling, Optimisation Abstract: This paper presents simple and efficient algorithms for the alleviation of line overloads and voltage violations by corrective rescheduling. The proposed approach utilises the decoupling of real and reactive power and the decomposition between optimisation without security constraints and optimisation to satisfy security constraints. Highlights of the proposed approach are: (i) a choice of performance index which ensures that alleviation of some of the existing violations does not create any fresh violations, thus avoiding the need for cycling in optimisation and, (ii) the use of a classical optimisation technique for faster solu- tions. Results for two sample test systems have been presented to validate the proposed algo- rithms. List of principal symbols AC T WF fi.fi fi NL NG AP Gk = change in total operating cost of gen- eration = weighting factor = ith line MW-flow with corrected and base case generation schedule = ith line MW-flow limit = number of transmission lines = number of generators = generation correction at feth bus = incremental transmission losses and AP Gk = lower and upper limits for feth bus gen- eration correction Q^Git) = k tn generator operating cost = cost coefficients of feth generator IC k AVr. = base case and corrected real power generation of feth generator = incremental cost of fcth generator = generation shift factor = A-loss coefficient = inverse of penalty factor at feth gener- ator = voltage corrections at PV-buses At WU p NC NB U P QGP V V I.H 1 ' ft b, = vector of reactive power compensation changes = vector of tap changer position correc- tions = weighting factor for control changes = total number of controls for voltage subproblem = total number of buses = weighting factors for limiting Q at PV-bus = control variable for voltage sub- problem = reactive power generation at PV-buses = weighting factor for correcting the nth load bus voltage = base case and corrected voltages at nth load bus = number of switched capacitors/ reactors = change in the reactive power loss = lower and upper limits for nth load bus voltage = lower and upper limits of reactive gen- eration changes at pth bus = sensitivity matrix relating [AQ G ] with [At/] = sensitivity matrix relating [AF] with [At/] = setting of nth OLTC = ith line charging susceptance = ith line series subsceptance Introduction Paper 9284C (P9), received 7th August 1992 The authors are with the Department of Electrical Engineering and Centre for Energy Studies, Indian Institute of Technology, Delhi, India The operating point of a power system will undergo a change due to various contingencies and disturbances on the system. If the system survives the outage or dis- turbance, it will operate in a new steady state in which one or more transmission lines may be overloaded and hence voltage constraints at some buses may be violated. System dispatchers will resort to corrective rescheduling for removing constraint violations. The problem of corrective rescheduling for the allevia- tion of overloads and voltage limit violations can be solved by decomposed or nondecomposed approaches. In the nondecomposed approach the unified single optim- isation problem is solved with security constraints. This requires excessive computational storage and time. The decomposed approach is usually preferred keeping in view any computational requirements. Such an approach involves the solution of an optimisation problem without IEE PROCEEDINGS-C, Vol. 140, No. 4, JULY 1993 249