Joseph Olorunfemi Ojo

Range of the Linear Modulation in Matrix Converters

This paper is focused on the improvement of the control range of matrix converters operating with nonunity input power factor. The analysis leads to the determination in closed form of a modulation strategy that allows increasing the maximum output voltage compared to the traditional strategies under the same operating conditions. The improvement of the control range is made possible by the information provided by the measurement of load currents, which is usually available in electric drives. The feasibility of the new strategy is verified by computer simulations and experimental tests.

Three-phase multilevel inverter configuration for open-winding high power application

This paper work exploits a new dual open-winding three-phase multilevel inverter configuration suitable for high power medium-voltage applications. Modular structure comprised of standard three-phase voltage source inverter (VSI) along with one additional bi-directional semiconductor device (MOSFET/IGBT) per phase and two capacitors with neutral point. Hence, introduces the additional voltage levels in each phase of the VSI. Further, this paper developed a modified single carrier five-level modulation (MSCFM) scheme in such way to overcome the complexity of standard space vector modulations, ready for implementation purpose. Proposed dual-inverter configuration generates multilevel outputs with benefit includes reduced THD and dv/dt in comparison to other dual-inverter topologies. Complete model of the multilevel ac drive is developed with simple MSCFM modulation in Matlab/PLECs numerical software. Preliminary results are provided in this paper confirm the suitability of investigation for real implementation.

Implementation of Wavelet-Based Robust Differential Control for Electric Vehicle Application

This research letter presents the modeling and simulation of electronic differential, employing a novel wavelet controller for two brushless dc motors. The proposed controller uses discrete wavelet transform to decompose the error between actual and reference speed. Error signal that is actually given by the electronic differential based on throttle and steering angle is decomposed into frequency components. Numerical simulation results are provided for both wavelet and proportional-integral-derivate controllers. In comparison, the proposed wavelet control technique provides greater stability and ensures smooth control of the two back driving wheels.

Analysis of Wavelet Controller for Robustness in Electronic Differential of Electric Vehicles: An Investigation and Numerical Developments

ABSTRACT In road transportation systems, differential plays an important role in preventing the vehicle from slipping on curved tracks. In practice, mechanical differentials are used, but they are bulky because of their increased weight. Moreover, they are not suitable for electric vehicles, especially those employing separate drives for both rear wheels. The electronic differential constitutes recent technological advances in electric vehicle design, enabling better stability and control of a vehicle on curved roads. This article articulates the modeling and simulation of an electronic differential employing a novel wavelet transform controller for two brushless DC motors ensuring drive in two right and left back driving wheels. Further, the proposed work uses a discrete wavelet transform controller to decompose the error between actual and command speed provided by the electronic differential based on throttle and steering angle as the input into frequency components. By scaling these frequency components by their respective gains, the obtained control signal is actually given as input to the motor. To verify the proposal, a set of designed strategies were carried out: a vehicle on a straight road, turning right and turning left. Numerical simulation test results of the controllers are presented and compared for robust performance and stability.

High-Voltage DC-DC Converter Topology for PV Energy Utilization - Investigation and Implementation

Abstract This paper exploited the utilization of photovoltaic (PV) energy system with high-voltage (HV) output DC-DC converter. Classical boost converters are used for both renewable energy integration and HV applications, but limited by reducing output/efficiency in performance. Moreover, as parasitic elements suppress the power transfer ratio, converter needs to maximize the PV energy utilization. This investigation study focused to include additional parasitic elements (voltage-lift technique) to a standard DC-DC buck converter and to overcome all the above drawbacks to maximize the PV power generation. The proposed power circuitry substantially improves the output power gain transfer ratio and a prototype hardware module is implemented using industrial standard DSP TMS 320F2812. Numerical simulation development followed by an experimental prototype implementation is carried out in this investigation. A set of numerical and experimental results is provided in this paper, which show close conformity with the theoretical background.

Modeling of nine-phase interior permanent magnet machines (IPM) including harmonic effects

This paper presents the modeling of the nine-phase interior permanent magnet machine (IPM) with and without damper windings for the clear understanding of its advantages such as fault tolerant and torque ripple reduction. This includes the influence of the higher order magneto-motive force (MMF) harmonics of the stator windings and the buried magnets for the improvement of the torque capability of the machine through injection of corresponding stator harmonic currents. The inductances are determined using the concept of winding functions for exact computer simulation based calculation and using Fourier components of the stator windings and the magnet flux for achieving closed-form expressions for the fundamental, third, fifth and the seventh harmonic components. Further analysis of the q-d equations of the nine-phase machine also shows the presence of low impedance circuits which could be excited under fault conditions signaling the detrimental effects of fault conditions on the multi-phase machines which may be avoided/reduced when the machine is connected into various three-phase sets. Some inductances showing their existence in different harmonic representation as well as experimental waveforms have been included.

Decoupled control of doubly fed induction generator for wind power system

Wind power, as an important and promising renewable resource, is widely studied. Recently, doubly fed induction generator (DFIG) becomes more popular in wind power due to its various advantages over other types of wind turbines, such as variable speed, lower power electronic cost and so on. However, the back-to-back converters require effective and accurate control to accommodate the complexity of power system operation. In this paper, first of all, a dynamic model of DFIG-based wind power system is derived in complex form. Based on the dynamic model, a complete control strategy is presented to control the rotor-side converter and grid-side converter, respectively. A decoupled control method, which is capable of separating d-axis and q-axis components of rotor current, is applied to harness wind power. The concept of instantaneous power is introduced to regulate DC-link voltage. The control strategy is tested in RTDS/RSCAD. The effectiveness of the proposed method is verified by the simulation results.

Direct vector controlled six-phase asymmetrical induction motor with power balanced space vector PWM multilevel operation

In this paper, a six-phase (asymmetrical) machine is investigated, 300 phase displacement is set between two three-phase stator windings keeping deliberately in open-end configuration. Power supply consists of four classical three-phase voltage inverters (VSIs), each one connected to the open-winding terminals. An original synchronous field oriented control (FOC) algorithm with three variables as degree of freedom is proposed, allowing power sharing among the four VSIs in symmetric/asymmetric conditions. A standard three-level space vector pulse width modulation (SVPWM) by nearest three vector (NTV) approach was adopted for each couple of VSIs to operate as multilevel output voltage generators. The proposed power sharing algorithm is verified for the ac drive system by observing the dynamic behaviours in different set conditions by complete simulation modelling in software (Matlab/Simulink-PLECS) and the results are provided in this paper. Furthermore, harmonic components are shown in each subspace and analysed with Fourier spectrum to confirm the smooth torque propagation with free of harmonic components. The numerical simulation results provided in this paper are closely matching with theoretical developments.

Wavelet transform with fuzzy tuning based indirect field oriented speed control of three-phase induction motor drive

This manuscript presents the details about the novel controller using wavelet transform and fuzzy logic tuning for speed control of an induction motor drive. The conventional proportional-integral (PI) speed controller in an indirect vector control of induction motor drive has been replaced by the proposed controller for an improved transient and steady state performances. The discrete wavelet transform has been used to decompose the error speed into different frequency components and the fuzzy logic is used to generate the scaling gains of the wavelet controller. The complete model of the proposed controller along with an induction motor drive incorporating the proposed controller has been developed in numerical simulation software using Matlab/Simulink environment and a set of results are provided within this paper in comparison to the conventional controller scheme.

Control schemes for field weakening of induction machines: A review

This paper provides an extensive overview of the control schemes that can be used for field-weakening operation of induction motors. Although almost all commercial drives offer this capability, a multitude of solutions have been proposed and the need of a classification arises. Therefore this paper attempts to illustrate the most used solutions that can be found in the literature. The control schemes can be classified according to different criteria, such as the control principle, the method used for the calculation of the optimal flux level (look-up tables, explicit equations, regulator-based solutions), the robustness against variations of the machine parameters and the exploitation of the dc-link voltage.