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Voltage stability analysis using a modified continuation load flow and optimal capacitor bank placement

CM Muriithi, LM Ngoo, GN Nyakoe, SN Njoroge

Abstract


This paper addresses the rising problem of identifying the voltage stability limits of load buses in a power system and how to optimally place capacitor banks for voltage stability improvement. This paper uses the concept of the continuation power flow analysis used in voltage stability analysis. It uses the modified continuation load flow to plot the PV curves of a load bus with an aggregate induction motor load. Neuro-fuzzy techniques have been used to model the induction motor load which represents an industrial load. In the subsequent predictor]corrector stages, the induction motors are increased to depict increment in loading. Different motor ratings are used in the investigations. The process starts at some base values of the system and leading to the critical point. Further the reduced Jacobian is used to strategically locate the capacitor banks in the power system so as to effect maximum voltage improvement. In case study, illustrative  examples with the IEEE 30 bus system are shown. The results indicate
that the modified continuation load flow captures the active and reactive power consumption of the induction motors revealing cases which could lead to voltage instability. In general, the larger rated aggregated  induction motors posed a greater voltage instability risk by demanding more reactive power at lower voltages compared the equivalent lower rated aggregated induction motors. In all, manipulation of the reduced Jacobian identified the optimal placement of capacitor banks for voltage stability improvement.

Key words: Continuation load flow, induction motors, voltage stability, neuro-fuzzy




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