Christopher M. Muriithi

Load flow analysis with a neuro-fuzzy model of an induction motor load

In the conventional load flow study, the active and reactive powers of all load buses are generally specified. Although the constant power model is applicable for approximate studies, it may not be suitable for the motors because the reactive power is very sensitive to the voltage variations while the active power is dependent upon the torque being driven. This paper proposes to solve the load flow equations using a neuro-fuzzy model of an induction motor. Both the active and reactive powers of the motor are estimated at each iteration using neuro fuzzy techniques. The efficiency is estimated using the IEEE 30 bus system. The results indicate that the inclusion of induction motor loads has an effect on the convergence characteristic of the active and reactive power mismatches of the modified load flow.

MPPT of a standalone wind energy conversion system using magnetostrictive amorphous wire speed sensor and fuzzy logic

This paper details the design and implementation of a Fuzzy Logic based controller for Maximum Power Point Tracking (MPPT) of a case study standalone wind energy conversion system(WECS). A magnetostrictive amorphous wire speed sensor is used for rotational speed measurement to provide an inexpensive, fast and robust solution to speed measurement. The designed MPPT algorithm includes a peak detection feature and a self-tuning capability which makes it intelligent and generic. The designed fuzzy logic controller determines the appropriate duty cycle D that yields optimum speed for maximum power extraction from the WECS for various wind speeds. It then applies this D to the DC-DC boost converter to control the speed of rotation of the PMSG to track maximum power point curve. The designed system was implemented on a real case study wind turbine under controlled conditions. Experimental results show that the designed system was able to significantly increase the maximum electrical power extracted for varying wind speeds.

Novel Modeling of a Fast DC Breaker for a VSC-HVDC Transmission System Protection

The inability to quickly isolate the faulty sections of the direct current (DC) network damages the converters and the transmission system. Further delay in fault interruption can be escalated to the generation system thus shutting down the whole power system. Currently, Voltage Source Converter-High Voltage Direct Current (VSC-HVDC) systems provide the best mode of bulky power transmission over long distance. Though VSC-HVDC have their own internal protection, they still suffer from short-circuit faults especially on the DC side hence requiring a novel fast DC breaker. The novel design of the DC breaker in this paper utilizes a systematically calculated mutual inductance to divert the energy generated during fault to resistive elementson both sides of the DC breaker thus, preventing the transient voltage and backward current generated at the time of clearing the fault. The major challenge for DC breaker is that current is not alternating inferring that it has no natural zero current occurring point. Thus, the current has to be artificially forced to cross a current zero point so that the fault can be easily interrupted.This study aims at reviewing the currently available DC breakers with a fault clearing time of 5msby modelinga novel fast DC breaker therefore, providing the best possible protection against short-circuit faults on VSC systems. The results indicate that the proposed DC breaker model has a fault clearing time of 1ms. This is a major contribution towards the development a fast DC breaker.