Yilmaz Sozer - Academia.edu (original) (raw)

Papers by Yilmaz Sozer

A method to control switch reluctance motors (SRM) in the dq rotating frame is proposed in this p... more A method to control switch reluctance motors (SRM) in the dq rotating frame is proposed in this paper. The torque per phase is represented in this paper as the product of sinusoidal inductance related term and sinusoidal current term in the SRM controller. The SRM controller works with variables similar to that of synchronous machine (SM) controller in dq reference frame which allow the torque to be shared smoothly among different phases. The proposed controller provides efficient operation over the entire speed range and eliminates the need for an angle decoder. The controller achieves low torque ripple at low speeds and can apply phase advancing using a mechanism similar to the flux weakening of SM to operate at high speeds. The effectiveness of the proposed controller is verified through coupled finite element and circuit simulations. Link:

A flux-weakening control for switched reluctance motors (SRMs) in the rotating reference frame is... more A flux-weakening control for switched reluctance motors (SRMs) in the rotating reference frame is proposed in this paper. This rotating reference frame control of SRM mimics the control of synchronous machines (SMs). The method uses the periodic nature of the quasi-sinusoidal static torque characteristics to establish the rotating reference frame. A novel negativity removal block and a simplified nonlinearity handling block are introduced to ensure a smooth torque sharing among different phases and adjust for the SRMs unique operating principle. In the dq control method, a d-axis current is commanded for weakening the flux. An adaptive control method that uses the commanded and actual currents determines the required amount of flux weakening. Through the unique features of dq controls, the proposed method offers smooth torque at low speed and supports a wide-speed operation. The proposed control method is verified experimentally.

2014 IEEE Energy Conversion Congress and Exposition (ECCE), 2014

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a sw... more ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. A single high-frequency pulse is injected in an idle phase and the rotor position is estimated through analysis of the resultant current after the voltage pulse injection. Low speed sensorless method developed previously based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed variable pulse injection duty ratio provided uniform sensing thresholds over varying DC bus voltages. The low speed and high speed methods can be integrated together to provide a robust wide speed range rotor position estimator for SRM.

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT

2015 IEEE Applied Power Electronics Conference and Exposition (APEC), 2015

2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012

A novel chirp pulse width modulation (CPWM) scheme is proposed to improve the performance of AC m... more A novel chirp pulse width modulation (CPWM) scheme is proposed to improve the performance of AC motor drives by reducing electromagnetic interference. The proposed CPWM is operated on the chirped waveform that has a specified bandwidth defined within a minimum and a maximum switching frequency. The design procedure of CPWM that includes selecting the chirp bandwidth and the PWM frequency sweeping time period is presented and analyzed. Then the theoretical analysis is done for both the chirped and non-chirped waveforms. Optimum EMI reduction scheme is developed from the theory. The computer simulation and experimental results verify that the proposed CPWM method has better performance in comparison to PWM with fixed frequency.

2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2013

ABSTRACT In this paper, a universal controller for switched-reluctance motor (SRM) is proposed. T... more ABSTRACT In this paper, a universal controller for switched-reluctance motor (SRM) is proposed. The controller is considered to be universal because it minimizes torque ripple, maximizes the efficiency and torque production using simple operations. A combination of direct torque control in one phase and current control in another phase is proposed and implemented in a way that minimizes the torque ripple and maximizes the efficiency while being robust. Moreover, torque maximization is achieved by introducing the demagnetization curve which ensures that the phase currents are demagnetized at an optimum angle such that maximum torque is produced without any negative torque generation. The validity of the proposed controller is verified through simulation studies.

Electric Power Components and Systems, 2015

ABSTRACT Droop control method is a widely used technique for achieving load sharing in DC microgr... more ABSTRACT Droop control method is a widely used technique for achieving load sharing in DC microgrid applications. Virtual output impedance (or droop gain) and voltage reference are the main control parameters typically selected based on the power ratings of the sources for proper load sharing. The performance of droop controller is affected significantly by the voltage drops across the transmission line impedances, resulting in a load sharing error and voltage degradation across the microgrid. In this article, a new optimization procedure is proposed to find the optimal droop parameters such that the effect of the line impedances is minimized. An optimization problem along with the required constrains is formulated as the combination of current sharing errors as well as the voltage degradation for various loading conditions. Particle swarm-based technique is then used to provide a solution for this optimization problem. The performance of the droop controller with the optimal droop parameters is verified through a simulation case study implemented on the MATLAB/Simulink environment.

This paper presents a predictive current control method for utility interactive renewable energy ... more This paper presents a predictive current control method for utility interactive renewable energy system and its application to the weak utility grid. The grid voltage is estimated in the d-q frame using the current value and the filtred inverter voltage for the next sampling cycle. The method uses the discrete time model of the system to predict the value of

Proceedings of the 1997 IEEE International Conference on Control Applications, 1997

This paper presents detailed analysis of doubly fed induction generator (DFIG) wind turbine elect... more This paper presents detailed analysis of doubly fed induction generator (DFIG) wind turbine electrical components during normal and unbalanced fault condition. Wind turbine components are individually modeled and then combined in a simulation process which is called coupled simulation. The coupled simulation results show that grid frequency oscillation occurs on q and d axis currents under one phase-ground fault condition. Experimental study has been done to show the effects of fault on rotor currents. Same behavior is also found in experimental rotor currents. Additionally experimental study shows that rotor currents are very sensitive to the grid fault voltage level.

2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012

2013 IEEE Industry Applications Society Annual Meeting, 2013

ABSTRACT The conventional switching strategy of a direct power control (DPC) scheme for doubly-fe... more ABSTRACT The conventional switching strategy of a direct power control (DPC) scheme for doubly-fed induction generator (DFIG) wind energy generation systems are based on hysteresis comparators. Non-linear behavior of this controller causes non-constant switching frequency on the rotor side converter, which depends on the wind speed, amount of power converted and the hysteresis band of the comparator. This paper proposes a constant switching frequency controller that can replace the hysteresis-based variable frequency controller. Using two triangular waveforms that are phase shifted by 180°, the DFIG can operate in wide range of speed with constant switching frequency. Matlab/Simulink and PSIM simulation packages are used to validate this type of controller.

2012 IEEE International Electric Vehicle Conference, 2012

ABSTRACT

2010 IEEE Industry Applications Society Annual Meeting, 2010

This paper presents the modeling and simulation of wind power systems based on two different indu... more This paper presents the modeling and simulation of wind power systems based on two different induction generators; the squirrel-cage induction generator (SCIG) and the doubly-fed induction generator (DFIG). The techniques of direct grid integration of SCIG system and independent power control of DFIG system are discussed. Particularly, to solve the droop in distribution line voltage in SCIG system, a reactive

2010 IEEE Energy Conversion Congress and Exposition, 2010

ABSTRACT This paper presents a systematic approach of meeting MIL-STD-461 for a 2kW brushless dc ... more ABSTRACT This paper presents a systematic approach of meeting MIL-STD-461 for a 2kW brushless dc generator that has its output power processed by a dc-dc converter. The structure of the generator system is such that the three-phase brushless dc generator provides power to an uncontrolled rectifier. The rectifier output is filtered by electrolytic capacitors. The uncontrolled dc output voltage feeds a dc-dc converter to regulate the output voltage. The electronic units, the uncontrolled rectifier and the dc-dc converter, are individual EMI noise sources. The approach taken deals with the individual noise sources separately and suppresses the noise as close to each source as possible. The EMC measurements and impedance measurements are done without any noise reduction effort to characterize the system. The characterization of the different EMC filter types is presented and simulated in Matlab. Using the measured system characteristics, and the characteristics of the actual filter types, noise reduction techniques have been implemented either through most appropriate EMC filters or through snubber networks. Tests and measurements are performed with each individual component added. The method, which approaches each individual system separately, provides compact and cheap filter solutions to meet the EMC requirements.

2012 IEEE International Electric Vehicle Conference, 2012

A bi-directional buck-boost DC-DC converter is presented for vehicle charging as well as vehicle ... more A bi-directional buck-boost DC-DC converter is presented for vehicle charging as well as vehicle to grid (V2G) energy transfer. The chosen cascaded buck-boost topology allows overlapping input and output voltage ranges and a higher intermediate DC bus voltage where the electric drivetrain traction inverter can be connected. The intermediate DC-link capacitor voltage is varied to improve the transient performance of

2012 IEEE PES Innovative Smart Grid Technologies (ISGT), 2012

We study the problem of minimizing the power generation cost and peak-to-average (PAR) of sources... more We study the problem of minimizing the power generation cost and peak-to-average (PAR) of sources' energy production for a network of multiple energy sources. We consider a power distribution network in which each load is connected to multiple sources and, depending on network connectivity, can be fed by more than one power source. We assume that the power generation cost

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a sw... more ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. A single high-frequency pulse is injected in an idle phase and the rotor position is estimated through analysis of the resultant current after the voltage pulse injection. Low speed sensorless method developed previously based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed variable pulse injection duty ratio provided uniform sensing thresholds over varying DC bus voltages. The low speed and high speed methods can be integrated together to provide a robust wide speed range rotor position estimator for SRM.

A method to control switch reluctance motors (SRM) in the dq rotating frame is proposed in this p... more A method to control switch reluctance motors (SRM) in the dq rotating frame is proposed in this paper. The torque per phase is represented in this paper as the product of sinusoidal inductance related term and sinusoidal current term in the SRM controller. The SRM controller works with variables similar to that of synchronous machine (SM) controller in dq reference frame which allow the torque to be shared smoothly among different phases. The proposed controller provides efficient operation over the entire speed range and eliminates the need for an angle decoder. The controller achieves low torque ripple at low speeds and can apply phase advancing using a mechanism similar to the flux weakening of SM to operate at high speeds. The effectiveness of the proposed controller is verified through coupled finite element and circuit simulations. Link:

A flux-weakening control for switched reluctance motors (SRMs) in the rotating reference frame is... more A flux-weakening control for switched reluctance motors (SRMs) in the rotating reference frame is proposed in this paper. This rotating reference frame control of SRM mimics the control of synchronous machines (SMs). The method uses the periodic nature of the quasi-sinusoidal static torque characteristics to establish the rotating reference frame. A novel negativity removal block and a simplified nonlinearity handling block are introduced to ensure a smooth torque sharing among different phases and adjust for the SRMs unique operating principle. In the dq control method, a d-axis current is commanded for weakening the flux. An adaptive control method that uses the commanded and actual currents determines the required amount of flux weakening. Through the unique features of dq controls, the proposed method offers smooth torque at low speed and supports a wide-speed operation. The proposed control method is verified experimentally.

2014 IEEE Energy Conversion Congress and Exposition (ECCE), 2014

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a sw... more ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. A single high-frequency pulse is injected in an idle phase and the rotor position is estimated through analysis of the resultant current after the voltage pulse injection. Low speed sensorless method developed previously based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed variable pulse injection duty ratio provided uniform sensing thresholds over varying DC bus voltages. The low speed and high speed methods can be integrated together to provide a robust wide speed range rotor position estimator for SRM.

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT

2015 IEEE Applied Power Electronics Conference and Exposition (APEC), 2015

2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012

A novel chirp pulse width modulation (CPWM) scheme is proposed to improve the performance of AC m... more A novel chirp pulse width modulation (CPWM) scheme is proposed to improve the performance of AC motor drives by reducing electromagnetic interference. The proposed CPWM is operated on the chirped waveform that has a specified bandwidth defined within a minimum and a maximum switching frequency. The design procedure of CPWM that includes selecting the chirp bandwidth and the PWM frequency sweeping time period is presented and analyzed. Then the theoretical analysis is done for both the chirped and non-chirped waveforms. Optimum EMI reduction scheme is developed from the theory. The computer simulation and experimental results verify that the proposed CPWM method has better performance in comparison to PWM with fixed frequency.

2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2013

ABSTRACT In this paper, a universal controller for switched-reluctance motor (SRM) is proposed. T... more ABSTRACT In this paper, a universal controller for switched-reluctance motor (SRM) is proposed. The controller is considered to be universal because it minimizes torque ripple, maximizes the efficiency and torque production using simple operations. A combination of direct torque control in one phase and current control in another phase is proposed and implemented in a way that minimizes the torque ripple and maximizes the efficiency while being robust. Moreover, torque maximization is achieved by introducing the demagnetization curve which ensures that the phase currents are demagnetized at an optimum angle such that maximum torque is produced without any negative torque generation. The validity of the proposed controller is verified through simulation studies.

Electric Power Components and Systems, 2015

ABSTRACT Droop control method is a widely used technique for achieving load sharing in DC microgr... more ABSTRACT Droop control method is a widely used technique for achieving load sharing in DC microgrid applications. Virtual output impedance (or droop gain) and voltage reference are the main control parameters typically selected based on the power ratings of the sources for proper load sharing. The performance of droop controller is affected significantly by the voltage drops across the transmission line impedances, resulting in a load sharing error and voltage degradation across the microgrid. In this article, a new optimization procedure is proposed to find the optimal droop parameters such that the effect of the line impedances is minimized. An optimization problem along with the required constrains is formulated as the combination of current sharing errors as well as the voltage degradation for various loading conditions. Particle swarm-based technique is then used to provide a solution for this optimization problem. The performance of the droop controller with the optimal droop parameters is verified through a simulation case study implemented on the MATLAB/Simulink environment.

This paper presents a predictive current control method for utility interactive renewable energy ... more This paper presents a predictive current control method for utility interactive renewable energy system and its application to the weak utility grid. The grid voltage is estimated in the d-q frame using the current value and the filtred inverter voltage for the next sampling cycle. The method uses the discrete time model of the system to predict the value of

Proceedings of the 1997 IEEE International Conference on Control Applications, 1997

This paper presents detailed analysis of doubly fed induction generator (DFIG) wind turbine elect... more This paper presents detailed analysis of doubly fed induction generator (DFIG) wind turbine electrical components during normal and unbalanced fault condition. Wind turbine components are individually modeled and then combined in a simulation process which is called coupled simulation. The coupled simulation results show that grid frequency oscillation occurs on q and d axis currents under one phase-ground fault condition. Experimental study has been done to show the effects of fault on rotor currents. Same behavior is also found in experimental rotor currents. Additionally experimental study shows that rotor currents are very sensitive to the grid fault voltage level.

2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012

2013 IEEE Industry Applications Society Annual Meeting, 2013

ABSTRACT The conventional switching strategy of a direct power control (DPC) scheme for doubly-fe... more ABSTRACT The conventional switching strategy of a direct power control (DPC) scheme for doubly-fed induction generator (DFIG) wind energy generation systems are based on hysteresis comparators. Non-linear behavior of this controller causes non-constant switching frequency on the rotor side converter, which depends on the wind speed, amount of power converted and the hysteresis band of the comparator. This paper proposes a constant switching frequency controller that can replace the hysteresis-based variable frequency controller. Using two triangular waveforms that are phase shifted by 180°, the DFIG can operate in wide range of speed with constant switching frequency. Matlab/Simulink and PSIM simulation packages are used to validate this type of controller.

2012 IEEE International Electric Vehicle Conference, 2012

ABSTRACT

2010 IEEE Industry Applications Society Annual Meeting, 2010

This paper presents the modeling and simulation of wind power systems based on two different indu... more This paper presents the modeling and simulation of wind power systems based on two different induction generators; the squirrel-cage induction generator (SCIG) and the doubly-fed induction generator (DFIG). The techniques of direct grid integration of SCIG system and independent power control of DFIG system are discussed. Particularly, to solve the droop in distribution line voltage in SCIG system, a reactive

2010 IEEE Energy Conversion Congress and Exposition, 2010

ABSTRACT This paper presents a systematic approach of meeting MIL-STD-461 for a 2kW brushless dc ... more ABSTRACT This paper presents a systematic approach of meeting MIL-STD-461 for a 2kW brushless dc generator that has its output power processed by a dc-dc converter. The structure of the generator system is such that the three-phase brushless dc generator provides power to an uncontrolled rectifier. The rectifier output is filtered by electrolytic capacitors. The uncontrolled dc output voltage feeds a dc-dc converter to regulate the output voltage. The electronic units, the uncontrolled rectifier and the dc-dc converter, are individual EMI noise sources. The approach taken deals with the individual noise sources separately and suppresses the noise as close to each source as possible. The EMC measurements and impedance measurements are done without any noise reduction effort to characterize the system. The characterization of the different EMC filter types is presented and simulated in Matlab. Using the measured system characteristics, and the characteristics of the actual filter types, noise reduction techniques have been implemented either through most appropriate EMC filters or through snubber networks. Tests and measurements are performed with each individual component added. The method, which approaches each individual system separately, provides compact and cheap filter solutions to meet the EMC requirements.

2012 IEEE International Electric Vehicle Conference, 2012

A bi-directional buck-boost DC-DC converter is presented for vehicle charging as well as vehicle ... more A bi-directional buck-boost DC-DC converter is presented for vehicle charging as well as vehicle to grid (V2G) energy transfer. The chosen cascaded buck-boost topology allows overlapping input and output voltage ranges and a higher intermediate DC bus voltage where the electric drivetrain traction inverter can be connected. The intermediate DC-link capacitor voltage is varied to improve the transient performance of

2012 IEEE PES Innovative Smart Grid Technologies (ISGT), 2012

We study the problem of minimizing the power generation cost and peak-to-average (PAR) of sources... more We study the problem of minimizing the power generation cost and peak-to-average (PAR) of sources' energy production for a network of multiple energy sources. We consider a power distribution network in which each load is connected to multiple sources and, depending on network connectivity, can be fed by more than one power source. We assume that the power generation cost

2013 IEEE Energy Conversion Congress and Exposition, 2013

ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a sw... more ABSTRACT In this paper, a pulse injection based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. A single high-frequency pulse is injected in an idle phase and the rotor position is estimated through analysis of the resultant current after the voltage pulse injection. Low speed sensorless method developed previously based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed variable pulse injection duty ratio provided uniform sensing thresholds over varying DC bus voltages. The low speed and high speed methods can be integrated together to provide a robust wide speed range rotor position estimator for SRM.