2020 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM)
This paper proposes a sensorless control of an electrically excited synchronous machine (EESM) us... more This paper proposes a sensorless control of an electrically excited synchronous machine (EESM) using mutual inductance. EESM is a synchronous machine that has a field winding to generate field flux. The field winding and the stator winding are mutually coupled together with mutual inductance. The mutual inductance is derived as a function of the rotor position by the principle of a rotary transformer. With the derived mutual inductance, the proposed method estimates the rotor position from the mutually induced field current by fundamental pulse-width modulation (PWM) switching voltage of stator winding. High-frequency current sampling synchronized with PWM switching is used to process the field current. The simulation results of sensorless speed control and position estimation under saturation condition validate the proposed method and its robustness to parameter variation.
2021 23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)
An adjustable current source driver based on shaping the gate current of a SiC MOSFET is presente... more An adjustable current source driver based on shaping the gate current of a SiC MOSFET is presented in this paper. A sequential optimization algorithm to reduce the turn-on and turn-off switching losses while maintaining equal device stress is developed. The proposed driver uses the maximum operating conditions in the entire operating range, in contrast to commercial drivers which are usually designed for a worst-case operating point. Thus, an improvement on full load as well as on partial load conditions is attained in comparison to the conventional voltage source driver. At system level, the reduction of switching losses lead to an improvement of the inverter efficiency and to a reduction of the electrical drive WLTP cycle losses by 7%.
International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, PCIM Europe 2020, 7 July 2020 through 8 July 2020, 2020
2013 IEEE International Symposium on Sensorless Control for Electrical Drives and Predictive Control of Electrical Drives and Power Electronics (SLED/PRECEDE), 2013
ABSTRACT We consider multiple-objective model-predictive control (MPC) of a linear time-invariant... more ABSTRACT We consider multiple-objective model-predictive control (MPC) of a linear time-invariant (LTI) single-input single-output (SISO) system (for simplicity without input constraints and/or disturbances). The performance index is the sum of weighted convex functionals J = Σi=1nwiJi (with wi ≥ 0). Although, by theory, the overall model-predictive control problem has a unique, globally optimal solution, this does not imply optimality of each sub-performance index Ji. To achieve “desirable” control performance, one has to find “decent” weighting factors wi; often done by “trial-and-error” which should be avoided, since weighting factor design might be not intuitive (even for LTI SISO systems without constraints; as we will show). The inherent difficulty lies in the mismatch between the “human performance index” (the optimality measure in the mind of the control engineer) and the implemented performance index J. In this paper, we illustrate these difficulties for a simple, linear third-order system and present some (old and new) approaches to ease weighting factor design. We do not give full answers but discuss first ideas which are admissible within the theoretical framework of standard MPC of LTI SISO systems.
2017 IEEE 26th International Symposium on Industrial Electronics (ISIE), 2017
This paper presents a performance comparison of feedback linearization and field oriented control... more This paper presents a performance comparison of feedback linearization and field oriented control for a synchronous reluctance machine. In order to represent realistic drive performance and dynamics, look-up tables of the machine inductances as a function of currents are used to include saturation effect. Additionally, a trained neural network was implemented to take the nonlinear behavior of the voltage source inverter into consideration. For a fair comparison between both methods, a genetic algorithm has been used for optimization of the controller settings. A linear model of the synchronous reluctance machine has been obtained after the nonlinearities are canceled through the feedback linearization where the dynamics of the machine are dictated by a reference plant model.
2019 IEEE International Symposium on Predictive Control of Electrical Drives and Power Electronics (PRECEDE), 2019
This paper presents an approach to continuous control set model predictive control, which uses re... more This paper presents an approach to continuous control set model predictive control, which uses reduced integration step size. The reduced integration step size allows to obtain a stream of finite control set, which can be filtered in order to obtain continuous control set. The Sinc-filter can be used to obtain improved accuracy of the voltage references. This approach is suitable for the motors with the high nonlinearity of the magnetization curve, which can be taken into account. The simulation results are presented in case of interior permanent magnet motor.
2019 IEEE International Electric Machines & Drives Conference (IEMDC), 2019
Neglecting magnetic saturation and cross-coupling effects in permanent magnet synchronous machine... more Neglecting magnetic saturation and cross-coupling effects in permanent magnet synchronous machines (PMSM), reduces the accuracy of tasks such as online parameter estimation, machine control and machine performance predictions. Taylor's theorem for multi-variable functions is used to express the direct-axis and quadrature-axis flux-linkages as power series in the PMSM model presented in this paper. Therefore, the model can be extended to a $n$-degree polynomial, where $n$ determines how accurately the saturation and cross-coupling effects are represented in the model. In addition, the identification of the model coefficients is formulated as an optimization problem that can be solved using quadratic programming. The proposed identification method is applied to data obtained from finite element simulations and measurements. Furthermore, for measured data, the method is extended to identify the machines winding resistance.
This paper proposes a robust encoderless predictive control strategy for variable-speed wind turb... more This paper proposes a robust encoderless predictive control strategy for variable-speed wind turbines (VSWTs) with permanent-magnet synchronous generator (PMSG). The proposed predictive control is based on the deadbeat (DB) scheme, which has a good transient response but it requires the full knowledge of the system parameters. To overcome such a limitation, a discrete time integral action (DTIA) is added to the DB algorithm in order to increase the robustness against parameter variations and achieve a good steady-state response. The proposed DTIA is simple and easy to implement. Furthermore, a novel model reference adaptive system (MRAS) observer is presented for estimating the rotor speed and position of the PMSG. A search algorithm based on the finite control setmodel predictive control (FCS-MPC) concept is utilized to replace the fixed-gain PI controller in the adaptation mechanism of MRAS observer. Experimental results are presented to illustrate the feasibility of the proposed ...
IECON 2021 – 47th Annual Conference of the IEEE Industrial Electronics Society, 2021
This study presents current control algorithm based on a finite control set model predictive cont... more This study presents current control algorithm based on a finite control set model predictive control (FCS-MPC) to achieve both high dynamics and current ripple suppression. In the proposed method, the smoothed voltage vectors with a finite set are applied as a control input candidate to avoid a sudden change in output voltage which generates large current ripple. In addition, the smoothness is determined automatically depending on a drive situation and system’s specification. Owing to this, fast transient response is achieved while keeping small current ripple during drive operation. The simulated and experimental results obtained with a permanent magnet synchronous motor (PMSM) show that the proposed method is effective for current ripple reduction and high dynamics control as compared to traditional FCS-MPC approach.
2019 IEEE International Symposium on Predictive Control of Electrical Drives and Power Electronics (PRECEDE), 2019
This paper presents the hardware design, software architecture and workflow for rapid control pro... more This paper presents the hardware design, software architecture and workflow for rapid control prototyping intended for a wide-range of power electronics based systems. The proposed system is especially useful for computationally intensive algorithms and applications with high demands on the number of required measurements and gate signals. The focus is on a heterogeneous system architecture with minimized latency and jitter as well as a high signal integrity. The software architecture enables a simple, fast and performance driven implementation. A combination of carrier board and exchangeable interfacing adapter boards allows to control a wide range of power electronics applications and converters, i.e., starting with a single switching device, converters with one or several voltage levels and one or several phase legs, up to large modular multilevel converters for grid-tied connection or variable speed drives.
This article proposes an enhanced timely and robust constant current (CC) control for wireless in... more This article proposes an enhanced timely and robust constant current (CC) control for wireless in-flight charging systems. The challenge for practical wireless in-flight charging systems is to maintain a CC output for hovering drones under circumstances of the continuous variation of coupling effect, various charging power requirements, and the parameter shifting, which is nearly unexplored in previous studies on wireless power transfer technologies. In order to address the issue, this article adopts the online-trained radial basis function neural network (RBFNN) to ensure the expected CC output for battery charging, which aims to handle negative impacts of the continuously varied coupling effect, the disturbance of parameters, and the change of charging current. In this article, both simulated and experimental results are given to verify the effectiveness of the proposed control scheme, wherein the accuracy of the controlled output current is within 5% and the average response time is less than 100 ms. It shows that the proposed dynamic-balancing robust current control is an ideal technical solution for wireless in-flight charging of drones by means of remarkable characteristics of the adopted RBFNN-based controller, namely, the increased rapidity and the enhanced robustness.
Power converters are used in a wide range of industrial processes. Computational complexity, trac... more Power converters are used in a wide range of industrial processes. Computational complexity, tracking ability, and calculation accuracy are the main parameters that affect the switching performance of power converters. One of the major parts of switch-mode power converters is the controllers which are essential for proper operation. A new adaptive controller is proposed to reduce the computational complexity, the algorithm is presented based on Improved Variable Forgetting Factor (IVFF), Leading Dichotomous Coordinate Descent (DCD), and Exponentially-weighted Recursive Least Square (ERLS). The proposed method estimates the system coefficients with 98% accuracy. The settling time of the output voltage is 0.008[Formula: see text]ms which is faster than other algorithms. According to Leading DCD, this structure needs no multiplier and divider blocks. VFF leads to the improvement of the tracking ability and convergence rate in the system variations. This structure can be implemented on any application that needs an optimal controller. The Vedic mathematics as a multiplier operation is used in the structure of the improved VFF for reducing the calculation delay and area. The error of the proposed method converges to zero with lower than 60 iterations. In other words, the proposed algorithm calculates the optimal coefficients with lower than 50 iterations and is faster than another algorithm.
2020 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM)
This paper proposes a sensorless control of an electrically excited synchronous machine (EESM) us... more This paper proposes a sensorless control of an electrically excited synchronous machine (EESM) using mutual inductance. EESM is a synchronous machine that has a field winding to generate field flux. The field winding and the stator winding are mutually coupled together with mutual inductance. The mutual inductance is derived as a function of the rotor position by the principle of a rotary transformer. With the derived mutual inductance, the proposed method estimates the rotor position from the mutually induced field current by fundamental pulse-width modulation (PWM) switching voltage of stator winding. High-frequency current sampling synchronized with PWM switching is used to process the field current. The simulation results of sensorless speed control and position estimation under saturation condition validate the proposed method and its robustness to parameter variation.
2021 23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)
An adjustable current source driver based on shaping the gate current of a SiC MOSFET is presente... more An adjustable current source driver based on shaping the gate current of a SiC MOSFET is presented in this paper. A sequential optimization algorithm to reduce the turn-on and turn-off switching losses while maintaining equal device stress is developed. The proposed driver uses the maximum operating conditions in the entire operating range, in contrast to commercial drivers which are usually designed for a worst-case operating point. Thus, an improvement on full load as well as on partial load conditions is attained in comparison to the conventional voltage source driver. At system level, the reduction of switching losses lead to an improvement of the inverter efficiency and to a reduction of the electrical drive WLTP cycle losses by 7%.
International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, PCIM Europe 2020, 7 July 2020 through 8 July 2020, 2020
2013 IEEE International Symposium on Sensorless Control for Electrical Drives and Predictive Control of Electrical Drives and Power Electronics (SLED/PRECEDE), 2013
ABSTRACT We consider multiple-objective model-predictive control (MPC) of a linear time-invariant... more ABSTRACT We consider multiple-objective model-predictive control (MPC) of a linear time-invariant (LTI) single-input single-output (SISO) system (for simplicity without input constraints and/or disturbances). The performance index is the sum of weighted convex functionals J = Σi=1nwiJi (with wi ≥ 0). Although, by theory, the overall model-predictive control problem has a unique, globally optimal solution, this does not imply optimality of each sub-performance index Ji. To achieve “desirable” control performance, one has to find “decent” weighting factors wi; often done by “trial-and-error” which should be avoided, since weighting factor design might be not intuitive (even for LTI SISO systems without constraints; as we will show). The inherent difficulty lies in the mismatch between the “human performance index” (the optimality measure in the mind of the control engineer) and the implemented performance index J. In this paper, we illustrate these difficulties for a simple, linear third-order system and present some (old and new) approaches to ease weighting factor design. We do not give full answers but discuss first ideas which are admissible within the theoretical framework of standard MPC of LTI SISO systems.
2017 IEEE 26th International Symposium on Industrial Electronics (ISIE), 2017
This paper presents a performance comparison of feedback linearization and field oriented control... more This paper presents a performance comparison of feedback linearization and field oriented control for a synchronous reluctance machine. In order to represent realistic drive performance and dynamics, look-up tables of the machine inductances as a function of currents are used to include saturation effect. Additionally, a trained neural network was implemented to take the nonlinear behavior of the voltage source inverter into consideration. For a fair comparison between both methods, a genetic algorithm has been used for optimization of the controller settings. A linear model of the synchronous reluctance machine has been obtained after the nonlinearities are canceled through the feedback linearization where the dynamics of the machine are dictated by a reference plant model.
2019 IEEE International Symposium on Predictive Control of Electrical Drives and Power Electronics (PRECEDE), 2019
This paper presents an approach to continuous control set model predictive control, which uses re... more This paper presents an approach to continuous control set model predictive control, which uses reduced integration step size. The reduced integration step size allows to obtain a stream of finite control set, which can be filtered in order to obtain continuous control set. The Sinc-filter can be used to obtain improved accuracy of the voltage references. This approach is suitable for the motors with the high nonlinearity of the magnetization curve, which can be taken into account. The simulation results are presented in case of interior permanent magnet motor.
2019 IEEE International Electric Machines & Drives Conference (IEMDC), 2019
Neglecting magnetic saturation and cross-coupling effects in permanent magnet synchronous machine... more Neglecting magnetic saturation and cross-coupling effects in permanent magnet synchronous machines (PMSM), reduces the accuracy of tasks such as online parameter estimation, machine control and machine performance predictions. Taylor's theorem for multi-variable functions is used to express the direct-axis and quadrature-axis flux-linkages as power series in the PMSM model presented in this paper. Therefore, the model can be extended to a $n$-degree polynomial, where $n$ determines how accurately the saturation and cross-coupling effects are represented in the model. In addition, the identification of the model coefficients is formulated as an optimization problem that can be solved using quadratic programming. The proposed identification method is applied to data obtained from finite element simulations and measurements. Furthermore, for measured data, the method is extended to identify the machines winding resistance.
This paper proposes a robust encoderless predictive control strategy for variable-speed wind turb... more This paper proposes a robust encoderless predictive control strategy for variable-speed wind turbines (VSWTs) with permanent-magnet synchronous generator (PMSG). The proposed predictive control is based on the deadbeat (DB) scheme, which has a good transient response but it requires the full knowledge of the system parameters. To overcome such a limitation, a discrete time integral action (DTIA) is added to the DB algorithm in order to increase the robustness against parameter variations and achieve a good steady-state response. The proposed DTIA is simple and easy to implement. Furthermore, a novel model reference adaptive system (MRAS) observer is presented for estimating the rotor speed and position of the PMSG. A search algorithm based on the finite control setmodel predictive control (FCS-MPC) concept is utilized to replace the fixed-gain PI controller in the adaptation mechanism of MRAS observer. Experimental results are presented to illustrate the feasibility of the proposed ...
IECON 2021 – 47th Annual Conference of the IEEE Industrial Electronics Society, 2021
This study presents current control algorithm based on a finite control set model predictive cont... more This study presents current control algorithm based on a finite control set model predictive control (FCS-MPC) to achieve both high dynamics and current ripple suppression. In the proposed method, the smoothed voltage vectors with a finite set are applied as a control input candidate to avoid a sudden change in output voltage which generates large current ripple. In addition, the smoothness is determined automatically depending on a drive situation and system’s specification. Owing to this, fast transient response is achieved while keeping small current ripple during drive operation. The simulated and experimental results obtained with a permanent magnet synchronous motor (PMSM) show that the proposed method is effective for current ripple reduction and high dynamics control as compared to traditional FCS-MPC approach.
2019 IEEE International Symposium on Predictive Control of Electrical Drives and Power Electronics (PRECEDE), 2019
This paper presents the hardware design, software architecture and workflow for rapid control pro... more This paper presents the hardware design, software architecture and workflow for rapid control prototyping intended for a wide-range of power electronics based systems. The proposed system is especially useful for computationally intensive algorithms and applications with high demands on the number of required measurements and gate signals. The focus is on a heterogeneous system architecture with minimized latency and jitter as well as a high signal integrity. The software architecture enables a simple, fast and performance driven implementation. A combination of carrier board and exchangeable interfacing adapter boards allows to control a wide range of power electronics applications and converters, i.e., starting with a single switching device, converters with one or several voltage levels and one or several phase legs, up to large modular multilevel converters for grid-tied connection or variable speed drives.
This article proposes an enhanced timely and robust constant current (CC) control for wireless in... more This article proposes an enhanced timely and robust constant current (CC) control for wireless in-flight charging systems. The challenge for practical wireless in-flight charging systems is to maintain a CC output for hovering drones under circumstances of the continuous variation of coupling effect, various charging power requirements, and the parameter shifting, which is nearly unexplored in previous studies on wireless power transfer technologies. In order to address the issue, this article adopts the online-trained radial basis function neural network (RBFNN) to ensure the expected CC output for battery charging, which aims to handle negative impacts of the continuously varied coupling effect, the disturbance of parameters, and the change of charging current. In this article, both simulated and experimental results are given to verify the effectiveness of the proposed control scheme, wherein the accuracy of the controlled output current is within 5% and the average response time is less than 100 ms. It shows that the proposed dynamic-balancing robust current control is an ideal technical solution for wireless in-flight charging of drones by means of remarkable characteristics of the adopted RBFNN-based controller, namely, the increased rapidity and the enhanced robustness.
Power converters are used in a wide range of industrial processes. Computational complexity, trac... more Power converters are used in a wide range of industrial processes. Computational complexity, tracking ability, and calculation accuracy are the main parameters that affect the switching performance of power converters. One of the major parts of switch-mode power converters is the controllers which are essential for proper operation. A new adaptive controller is proposed to reduce the computational complexity, the algorithm is presented based on Improved Variable Forgetting Factor (IVFF), Leading Dichotomous Coordinate Descent (DCD), and Exponentially-weighted Recursive Least Square (ERLS). The proposed method estimates the system coefficients with 98% accuracy. The settling time of the output voltage is 0.008[Formula: see text]ms which is faster than other algorithms. According to Leading DCD, this structure needs no multiplier and divider blocks. VFF leads to the improvement of the tracking ability and convergence rate in the system variations. This structure can be implemented on any application that needs an optimal controller. The Vedic mathematics as a multiplier operation is used in the structure of the improved VFF for reducing the calculation delay and area. The error of the proposed method converges to zero with lower than 60 iterations. In other words, the proposed algorithm calculates the optimal coefficients with lower than 50 iterations and is faster than another algorithm.
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Papers by Ralph Kennel