Proceedings of the Third International Conference on Computing and Wireless Communication Systems, ICCWCS 2019, April 24-25, 2019, Faculty of Sciences, Ibn Tofaïl University -Kénitra- Morocco, 2019
With the proliferation of non-linear loads in electricity supply industry, interests in improving... more With the proliferation of non-linear loads in electricity supply industry, interests in improving quality of electrical supply have increased significantly. Power quality challenges have generated disputes between customers, network operators and equipment manufacturers globally. Identification of the sources of harmonics, and the quantification of the identified variables at the points of common coupling (PCC) pose challenges in the electricity supply industry. Critical in the determination of the harmonic contributions are data for harmonic distortions in phase currents and voltages, power factor, apparent power, active power, reactive power, and frequency. The data were obtained at the PCC between 5 different arc furnace steel plant and the transmission network. The data were captured at 33kV and 132kV voltage level at the steel plant PCC using a Circuitor AR6 power analyser connected through incoming voltage transformers (VTs) and current transformers (CTs). Histograms and cumulative probability distribution plots present the harmonic contents of the data. This data can be reused for artificial intelligence and machine learning application in real-time monitoring of state of health at the PCC and design of filter networks to mitigate harmonics.
2018 9th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2018
A control scheme of a three-phase multi-level multi-string inverter for grid integration of photo... more A control scheme of a three-phase multi-level multi-string inverter for grid integration of photovoltaic (PV) power systems is presented. The three-phase inverter synthesizes a five level output voltage from six isolated PV sources using reduced number of power switches when compared to conventional multilevel inverter topologies. Only eighteen power semiconductor switches are required to synthesize the five level ac output, six of which are operated at line frequency. This reduces the switching losses and also the overall cost of the system. The inverter uses a new modulation scheme in its control for handling power imbalance between the PV sources in each phase and amongst the three phases. Some results obtained from the grid connected five level multi-string inverter are presented
2018 9th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2018
This paper presents a direct model predictive method for controlling the grid current of a three-... more This paper presents a direct model predictive method for controlling the grid current of a three-phase photovoltaic system. The model of the inverter with an LCL filter in synchronous reference frame is presented in state-space format. The model predictive control scheme uses a compact cost function for simultaneously controlling the injected grid current, maintaining the capacitor dc-link voltage constant, and minimizing the switching frequency. Also, the reference signals for the control loop are generated in the predictive algorithm rather than through the use of cascaded PI controllers. Results for the proposed control scheme are presented.
Transitioning a conventional doubly fed induction generator (DFIG) into a shorted-stator mode ext... more Transitioning a conventional doubly fed induction generator (DFIG) into a shorted-stator mode extends its operation for low wind speed power application. Since the stator of the shorted-stator mode disconnects from grid, the grid's voltages no longer contribute to building up of stator flux linkage. Stability boundaries for both modes are predicted using eigenvalue computations from steady-state models obtained from both electrical and mechanical dynamics. Propensity for instability at subsynchronous stator frequency is investigated for situations such as subsynchronous resonance. An effective control scheme that transitions the conventional DFIG to and from the shorted-stator mode is developed for loss minimization and flux weakening. Robustness of the controller to system parameter mismatch is investigated. Simulation and experimental results are presented for a 5 Hp machine.
2015 IEEE 6th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2015
This paper presents a control scheme for autonomous operation of a doubly-fed induction generator... more This paper presents a control scheme for autonomous operation of a doubly-fed induction generator (DFIG) based wind turbine system with an integrated battery storage system. The standalone DFIG feeds an electric load that is characterized to have linear and nonlinear load structures with varying reactive power demand and variation in system frequency. Therefore, a droop control is implemented by the DFIG's line side converter (LSC) to regulate magnitude of voltage supplied to the load and system frequency. The connected battery storage system is controlled to supply extra active power demand when required for system frequency stability. Simulation results are presented.
This paper presents an approach to the modeling and analysis of fourth order DC-DC converters bas... more This paper presents an approach to the modeling and analysis of fourth order DC-DC converters based on switching function and harmonic balance technique. The proposed method readily predicts both the dynamic and steady state quantities of the state variables. To demonstrate this method, Cúk DC-DC converter topology is considered. Also presented is the large signal computer simulations of the steady state average and ripple quantities for the state variables and the switching devices.
2009 IEEE Power Electronics and Machines in Wind Applications, 2009
This paper presents the models of a five-phase interior permanent magnet machine (IPM) feeding a ... more This paper presents the models of a five-phase interior permanent magnet machine (IPM) feeding a rectifier resistive load. The model predicts the performance of a machine with a non-integer number of stator slots per pole. Using the stationary and rotor reference frames, the approximate diode switching functions are derived. Then harmonic balance technique is used to obtain the steady state
2009 IEEE International Electric Machines and Drives Conference, 2009
Abstract Traditional electric machine design requiring the balancing of the phases both in phase ... more Abstract Traditional electric machine design requiring the balancing of the phases both in phase voltage magnitudes and the angles between adjacent phases informs that the number of stator slots per phase must be an integer. There are situations however, where ...
2009 IEEE International Electric Machines and Drives Conference, 2009
... Sosthenes Karugaba, Olorunfemi Ojo and Adeola Balogun Department of Electrical and Computer ... more ... Sosthenes Karugaba, Olorunfemi Ojo and Adeola Balogun Department of Electrical and Computer Engineering/Center for Energy Systems Research Tennessee Technological University, Cookeville, TN 3805, USA Department of Electrical Engineering, University of Lagos ...
A method for obtaining natural variable model of induction machines (IM) is presented. The variab... more A method for obtaining natural variable model of induction machines (IM) is presented. The variables of the model are electromagnetic torque (Te), reactive torque (Tr), magnitude of rotor flux linkage (lambdar), magnitude of stator flux linkage (lambdas), and rotor speed (omegar). These variables do not change in any reference frame of transformation. The model obtained is expressed in a state-space form with the natural variables as state variables. Simulation is carried out and the results are compared with a conventional induction machine simulation technique. Simulation results show the efficacy of this model in predicting electrical behavior of induction machines. Flux linkage orientation is done to facilitate the simulation, which is similar to method of alignment in vector control.
2014 IEEE Energy Conversion Congress and Exposition (ECCE), 2014
A doubly-fed induction generator connected to a weak grid is presented. The grid is characterized... more A doubly-fed induction generator connected to a weak grid is presented. The grid is characterized by unbalanced voltage conditions, which introduces a negative sequence voltage to the stator windings. The negative sequence voltage conditions generate pulsations in the torque and power quantities of the generator, which affects its stability. Proportional plus resonant controllers are introduced into direct control of torque and power schemes to mitigate the pulsations. In order to extend the speed range of operation of the DFIG, the shorted-stator mode operation is considered so that at low wind speed some corresponding power are still generated into the PCC. The control of the shorted-stator mode shows more robustness against the unbalanced voltage conditions at the PCC with no pulsations in the electromagnetic torque. Some results are presented for a 5hp machine.
2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012
The electromagnetic torque, stator power, and the grid side converter (GSC) power outputs of a do... more The electromagnetic torque, stator power, and the grid side converter (GSC) power outputs of a double-fed induction generator (DFIG) are differentiated to obtain a feedback linear relationship with the rotor voltage vectors serving as the control inputs. The derived model is such that the torque and power quantities are the state variables of the system, which are insensitive to coordinate system orientation. The steady-state equations from the derived model are used to obtain the optimal operating region with respect to minimal electrical losses. Decoupled torque control is developed by field orientation, while decoupled power control is derived from voltage orientation of the DFIG. Robustness of the decoupled controllers against parameter variation is investigated by locating the poles of its closed-loop transfer function. Results for a 5Hp machine are presented.
2010 IEEE Energy Conversion Congress and Exposition, 2010
Abstract - A doubly fed induction generator (DFIG) system is presented in terms of its natural ... more Abstract - A doubly fed induction generator (DFIG) system is presented in terms of its natural and power variables as the state variables. The natural variables are the electromagnetic torque (Te), the reactive torque (Tr), the magnitude of rotor flux linkage (λr), the magnitude of ...
2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2013
The torque and power outputs of a doubly-fed induction generator (DFIG) are differentiated once t... more The torque and power outputs of a doubly-fed induction generator (DFIG) are differentiated once to obtain a linear relationship with the rotor voltage vectors, which are the control input quantities. The derived model is used to develop direct control of the torque and power of the DFIG whereby the rotor voltage quantities are generated at a constant switching frequency. Decoupled control of torque and power is obtained by field orientation and voltage alignment, respectively. Sensitivity of the direct control schemes to system parameter variation is investigated using small signal analysis. Results for a 5 hp machine indicate that the vector control is more affected by system parameter mismatch.
Proceedings of the Third International Conference on Computing and Wireless Communication Systems, ICCWCS 2019, April 24-25, 2019, Faculty of Sciences, Ibn Tofaïl University -Kénitra- Morocco, 2019
With the proliferation of non-linear loads in electricity supply industry, interests in improving... more With the proliferation of non-linear loads in electricity supply industry, interests in improving quality of electrical supply have increased significantly. Power quality challenges have generated disputes between customers, network operators and equipment manufacturers globally. Identification of the sources of harmonics, and the quantification of the identified variables at the points of common coupling (PCC) pose challenges in the electricity supply industry. Critical in the determination of the harmonic contributions are data for harmonic distortions in phase currents and voltages, power factor, apparent power, active power, reactive power, and frequency. The data were obtained at the PCC between 5 different arc furnace steel plant and the transmission network. The data were captured at 33kV and 132kV voltage level at the steel plant PCC using a Circuitor AR6 power analyser connected through incoming voltage transformers (VTs) and current transformers (CTs). Histograms and cumulative probability distribution plots present the harmonic contents of the data. This data can be reused for artificial intelligence and machine learning application in real-time monitoring of state of health at the PCC and design of filter networks to mitigate harmonics.
2018 9th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2018
A control scheme of a three-phase multi-level multi-string inverter for grid integration of photo... more A control scheme of a three-phase multi-level multi-string inverter for grid integration of photovoltaic (PV) power systems is presented. The three-phase inverter synthesizes a five level output voltage from six isolated PV sources using reduced number of power switches when compared to conventional multilevel inverter topologies. Only eighteen power semiconductor switches are required to synthesize the five level ac output, six of which are operated at line frequency. This reduces the switching losses and also the overall cost of the system. The inverter uses a new modulation scheme in its control for handling power imbalance between the PV sources in each phase and amongst the three phases. Some results obtained from the grid connected five level multi-string inverter are presented
2018 9th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2018
This paper presents a direct model predictive method for controlling the grid current of a three-... more This paper presents a direct model predictive method for controlling the grid current of a three-phase photovoltaic system. The model of the inverter with an LCL filter in synchronous reference frame is presented in state-space format. The model predictive control scheme uses a compact cost function for simultaneously controlling the injected grid current, maintaining the capacitor dc-link voltage constant, and minimizing the switching frequency. Also, the reference signals for the control loop are generated in the predictive algorithm rather than through the use of cascaded PI controllers. Results for the proposed control scheme are presented.
Transitioning a conventional doubly fed induction generator (DFIG) into a shorted-stator mode ext... more Transitioning a conventional doubly fed induction generator (DFIG) into a shorted-stator mode extends its operation for low wind speed power application. Since the stator of the shorted-stator mode disconnects from grid, the grid's voltages no longer contribute to building up of stator flux linkage. Stability boundaries for both modes are predicted using eigenvalue computations from steady-state models obtained from both electrical and mechanical dynamics. Propensity for instability at subsynchronous stator frequency is investigated for situations such as subsynchronous resonance. An effective control scheme that transitions the conventional DFIG to and from the shorted-stator mode is developed for loss minimization and flux weakening. Robustness of the controller to system parameter mismatch is investigated. Simulation and experimental results are presented for a 5 Hp machine.
2015 IEEE 6th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2015
This paper presents a control scheme for autonomous operation of a doubly-fed induction generator... more This paper presents a control scheme for autonomous operation of a doubly-fed induction generator (DFIG) based wind turbine system with an integrated battery storage system. The standalone DFIG feeds an electric load that is characterized to have linear and nonlinear load structures with varying reactive power demand and variation in system frequency. Therefore, a droop control is implemented by the DFIG's line side converter (LSC) to regulate magnitude of voltage supplied to the load and system frequency. The connected battery storage system is controlled to supply extra active power demand when required for system frequency stability. Simulation results are presented.
This paper presents an approach to the modeling and analysis of fourth order DC-DC converters bas... more This paper presents an approach to the modeling and analysis of fourth order DC-DC converters based on switching function and harmonic balance technique. The proposed method readily predicts both the dynamic and steady state quantities of the state variables. To demonstrate this method, Cúk DC-DC converter topology is considered. Also presented is the large signal computer simulations of the steady state average and ripple quantities for the state variables and the switching devices.
2009 IEEE Power Electronics and Machines in Wind Applications, 2009
This paper presents the models of a five-phase interior permanent magnet machine (IPM) feeding a ... more This paper presents the models of a five-phase interior permanent magnet machine (IPM) feeding a rectifier resistive load. The model predicts the performance of a machine with a non-integer number of stator slots per pole. Using the stationary and rotor reference frames, the approximate diode switching functions are derived. Then harmonic balance technique is used to obtain the steady state
2009 IEEE International Electric Machines and Drives Conference, 2009
Abstract Traditional electric machine design requiring the balancing of the phases both in phase ... more Abstract Traditional electric machine design requiring the balancing of the phases both in phase voltage magnitudes and the angles between adjacent phases informs that the number of stator slots per phase must be an integer. There are situations however, where ...
2009 IEEE International Electric Machines and Drives Conference, 2009
... Sosthenes Karugaba, Olorunfemi Ojo and Adeola Balogun Department of Electrical and Computer ... more ... Sosthenes Karugaba, Olorunfemi Ojo and Adeola Balogun Department of Electrical and Computer Engineering/Center for Energy Systems Research Tennessee Technological University, Cookeville, TN 3805, USA Department of Electrical Engineering, University of Lagos ...
A method for obtaining natural variable model of induction machines (IM) is presented. The variab... more A method for obtaining natural variable model of induction machines (IM) is presented. The variables of the model are electromagnetic torque (Te), reactive torque (Tr), magnitude of rotor flux linkage (lambdar), magnitude of stator flux linkage (lambdas), and rotor speed (omegar). These variables do not change in any reference frame of transformation. The model obtained is expressed in a state-space form with the natural variables as state variables. Simulation is carried out and the results are compared with a conventional induction machine simulation technique. Simulation results show the efficacy of this model in predicting electrical behavior of induction machines. Flux linkage orientation is done to facilitate the simulation, which is similar to method of alignment in vector control.
2014 IEEE Energy Conversion Congress and Exposition (ECCE), 2014
A doubly-fed induction generator connected to a weak grid is presented. The grid is characterized... more A doubly-fed induction generator connected to a weak grid is presented. The grid is characterized by unbalanced voltage conditions, which introduces a negative sequence voltage to the stator windings. The negative sequence voltage conditions generate pulsations in the torque and power quantities of the generator, which affects its stability. Proportional plus resonant controllers are introduced into direct control of torque and power schemes to mitigate the pulsations. In order to extend the speed range of operation of the DFIG, the shorted-stator mode operation is considered so that at low wind speed some corresponding power are still generated into the PCC. The control of the shorted-stator mode shows more robustness against the unbalanced voltage conditions at the PCC with no pulsations in the electromagnetic torque. Some results are presented for a 5hp machine.
2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012
The electromagnetic torque, stator power, and the grid side converter (GSC) power outputs of a do... more The electromagnetic torque, stator power, and the grid side converter (GSC) power outputs of a double-fed induction generator (DFIG) are differentiated to obtain a feedback linear relationship with the rotor voltage vectors serving as the control inputs. The derived model is such that the torque and power quantities are the state variables of the system, which are insensitive to coordinate system orientation. The steady-state equations from the derived model are used to obtain the optimal operating region with respect to minimal electrical losses. Decoupled torque control is developed by field orientation, while decoupled power control is derived from voltage orientation of the DFIG. Robustness of the decoupled controllers against parameter variation is investigated by locating the poles of its closed-loop transfer function. Results for a 5Hp machine are presented.
2010 IEEE Energy Conversion Congress and Exposition, 2010
Abstract - A doubly fed induction generator (DFIG) system is presented in terms of its natural ... more Abstract - A doubly fed induction generator (DFIG) system is presented in terms of its natural and power variables as the state variables. The natural variables are the electromagnetic torque (Te), the reactive torque (Tr), the magnitude of rotor flux linkage (λr), the magnitude of ...
2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2013
The torque and power outputs of a doubly-fed induction generator (DFIG) are differentiated once t... more The torque and power outputs of a doubly-fed induction generator (DFIG) are differentiated once to obtain a linear relationship with the rotor voltage vectors, which are the control input quantities. The derived model is used to develop direct control of the torque and power of the DFIG whereby the rotor voltage quantities are generated at a constant switching frequency. Decoupled control of torque and power is obtained by field orientation and voltage alignment, respectively. Sensitivity of the direct control schemes to system parameter variation is investigated using small signal analysis. Results for a 5 hp machine indicate that the vector control is more affected by system parameter mismatch.
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