EPE Association: EPE 2019 - DS3e: Estimation and Identification Methods; Sensorless Control

EPE 2019 - DS3e: Estimation and Identification Methods; Sensorless Control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2019 ECCE Europe - Conference > EPE 2019 - Topic 03: Measurement and Control > EPE 2019 - DS3e: Estimation and Identification Methods; Sensorless Control

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   Comparative Power Loss Analysis of DCM Flyback Transformer Based On FEA, Numeric Simulation, Calculation and Measurements
By Halil Alper ONAY [View]
[Download]

Abstract: The flyback transformer is a crucial part of the flyback converter, which has the highest portion oftotal power losses for most applications. Accurately prediction of the power losses due to flybacktransformer early in the design stage provides an advantage about revealing reliable prototypes. In this paper, several loss prediction methods are applied for a 40W universal input and single output DCM flyback transformer as; analytical calculations via well-known Steinmetz and Dowell's formulas, asimulation including numerical solutions, and a finite element analysis (FEA) based investigation. It isshown that the comprehensiveness of the methods accounting for hysteresis losses, eddy currentlosses, DC bias, and fringing effect based losses determine the accuracy of the results. In the paper, itis shown that the more the comprehensiveness, the closer the results to the values of electrical andthermal measurements. The power loss results obtained from theory and measurements with fivedifferent methods are compared and discussed in the detail.

   Electrolytic Capacitor Degradation Monitoring using an On-line Parameter Estimation Scheme involving Sliding Mode Differentiators and a Kalman Filter
By José Manuel ANDRADE [View]
[Download]

Abstract: An indication of electrolytic capacitor gradual degradation may be obtained by observing an increase in the equivalent series resistance (ESR) and a decrease in capacitance over time. On-line condition monitoring of these two electrical parameters allows for early detection of the capacitor ageing that can reduce catastrophic failure and their costly consequences. In this paper, a parameter estimation scheme consisting of sliding mode differentiators and a Kalman filter is proposed for electrolytic capacitor degradation monitoring. Satisfactory on-line estimation of the ESR and capacitance under noisy conditions is achieved with the proposed approach as demonstrated through computer simulation results.

   Improved current estimation in paralleled half-bridge converters
By Nikola BOSKOVIC [View]
[Download]

Abstract: When paralleling half bridges, their individual currents should be balanced to prevent large circulating currents. This paper improves an existing perturbation-based current estimation method by modifying the perturbation signal allowing a faster estimation of the currents, resulting in a reduction of current stress on components.

   Moving Horizon Parameter Estimation of Permanent Magnet Synchronous Machines
By Xinyue LI [View]
[Download]

Abstract: In this paper a general moving horizon estimation (MHE) scheme for online parameter estimation of permanent magnet synchronous machines (PMSMs) is investigated. The optimization problem is solved with the generalized Gauss-Newton method and the real-time iteration approach, which enables the real time implementation of the moving horizon estimation. Furthermore, the proposed estimator is compared with state-of-the-art observers, i.e. extended Kalman filter (EKF) and unscented Kalman filter (UKF), under two test cases. The proposed estimation scheme shows superior performance at the steady state and during the transient both in simulation as well as in experiment.

   Offset Estimation Strategies and Influence on Slotting Signal Resolution in Angular Voltage Step Excitation for Speed Sensorless Control of Induction Machines
By Eduardo RODRIGUEZ MONTERO [View]
[Download]

Abstract: The stable operation around zero electrical frequency of sensorless AC drives requires the utilization of external injection techniques (as high frequency or as voltage step) in order to obtain a leakage inductance modulated by the machine inherent saliencies. During the last two decades, numerous attempts have been done in order to reduce the impact of the external injection in terms of current ripple. In this sense, strategies have calculated the machine position from the saliency-offset vector using the actual SVPWM switching states.The saliency-offset vector obtained from one active SVPWM switching state delivers, in induction machines, a huge load and sector dependent offset. Its elimination is critical to obtain the machine saliency (in this work, slotting), as a poor offset amplitude estimation distorts the saliency signal and may lead to an untraceable sensorless rotor angle. This paper will analyze the effect that offset estimation errors produce in the desired saliency vector, and will compare the accuracy of two estimation strategies based on mean and circle-fit functions.

   Online parameter estimator of the DC bus capacitor bank for Doubly-Fed Induction Generators
By Cristian BLANCO [View]
[Download]

Abstract: This paper proposes an online parameter estimator of the DC Bus (series resistance, capacitance and in- ductance) used in Doubly-Fed Induction Generators (DFIG) in wind applications. The proposed method relies on electrical variables that are used for the control of DFIG, i.e. stator-side and rotor-side voltages and currents. The estimation is based on a recursive least squares algorithm using transients delivered by the normal operation of the system in wind generation applications. The validity of the proposal is discussed by the theoretical analysis and simulation results.

   Online Parameter Identification of Permanent Magnet Synchronous Machines with Nonlinear Magnetics based on the Inverter Induced Current Slopes and the dq-System
By Simon DECKER [View]
[Download]

Abstract: This paper shows a fast online parameter identification method for permanent magnet synchronous machines (PSMs), which uses the PWM (pulse width modulation) excitations and no additional test signals. Based on the inverter induced current slopes, the corresponding applied voltages, the rotor angle and a precise machine model, the model's parameters are calculated. Thereby the machine model consists of the dq-system equations, linearized within one PWM period. For stable and precise identification of the PSM machine parameters, the machine model has to be modified with a regularization approach. The identified parameters enable self-commissioning, tuning of the control parameters, condition monitoring or inner fault detection. In this paper the theoretical approach of the suggested method and simulation results of an equivalent test-bench system are presented.

   Performance Evaluation of Wideband Binary Identification of Grid Impedance Using Grid-connected Inverters
By Nabil MOHAMMED [View]
[Download]

Abstract: The application of the pseudo random binary sequence (PRBS) estimation technique for wideband grid impedance estimation using grid-connected inverters has gained more attention recently because of its several advantages. This includes its simple implementation in the control loop of the inverters and the small disturbance amplitude produced. In this context, this paper aims to evaluate the performance influences of the PRBS design parameters bit length, frequency resolution, and disturbance amplitude. This goal is achieved by exploring their effects on the grid impedance estimation accuracy and the produced total distortion (THD\%+PRBS noise) of the inverter output current. A 3-phase balanced inverter system is simulated and investigated using MATLAB/Simulink based on a discrete-time model to show the trade-off of a real implementation such as the PRBS disturbance amplitude and the sampling frequency of the analog-to-digital converters. Simulation results show the trade-off between the investigated PRBS parameters and the accuracy and frequency range of the estimated grid impedance as well as the total distortion.

   Positive-sequence flux estimator based on Second-Order Generalized Integrators for grid synchronization and motor control under imbalanced conditions
By Georgios ORFANOUDAKIS [View]
[Download]

Abstract: The estimation of flux as the integral of voltage presents challenges due to known integrator issues such as drift and saturation, while requiring high-pass filters to suppress DC offsets and low-frequency harmonics. High-pass filters in applications such as motor control need to be adaptive, in order to allow operation in an extended frequency range. The estimated fluxes are commonly fed to a Phase-Locked Loop (PLL), to calculate the voltage/flux angle and frequency. Common PLLs for three-phase systems operate on the basis of balanced input signals. Their estimates deteriorate in the existence of imbalance, which can affect the response of the controllers acting based on them. This paper presents an adaptive positive-sequence flux estimator based on Second-Order Generalized Integrators (SOGIs). The balanced fluxes generated by the estimator can be used for synchronization with an imbalanced grid or for sensorless control of a motor over an imbalanced cable. Simulation results are included to illustrate the method's application to an imbalanced grid and its response to transient conditions. Experimental results using a commercial motor drive running a permanent magnet motor (PMM) connected to the drive via a long cable are presented to compare the method with the conventional alternative. _ representative example of instability and loss of control occurring when using conventional integrators for sensorless control of a PMM over a flat armoured cable is included to illustrate the advantage offered by the proposed approach.

   Resource optimal FPGA implementation of a Least-Squares-Estimator for fast and robust online measurement of current slope and absolute value
By Andreas LISKE [View]
[Download]

Abstract: This paper presents an improved Least-Squares-Estimator for the fast, non-recursive online measurement of the first derivative and absolute value of a piecewise linear oversampled current signal. Core topic is the partially online calculation of the pseudoinverse matrix in combination with an optimized small lookup table, minimizing memory requirements significantly.

   Scalar/Vector Sensorless Control Combination Solution for Induction Motor Drives at Whole Speed Range Operation
By Iker PEÑA-GONZALEZ [View]
[Download]

Abstract: This paper presents a solution for induction motor sensorless drives, especially focused on low fundamental frequencies. The proposed strategy involves a combination of scalar and vector control techniques. Its performance is augmented with three different strategies that improve its behavior in the low frequencies range. Finally, the proposed strategies are verified via simulation and experimental tests, demonstrating the suitability of the solution.

   Sensorless and Modulated Model-Predictive Control for a Doubly Fed Induction Machine
By Jacopo RICCIO [View]
[Download]

Abstract: In this paper a sensorless control strategy has been implemented and experimentally validated to control independently the electromagnetic torque and the reactive power of a doubly-fed induction machine. The machine acts as a grid connected generator at variable speed operations around the synchronous speed. This control strategy is based on a model-predictive control strategy with the governing equations represented in a synchronous reference frame aligned to the stator flux. A modulation stage has been introduced in order to overcome the well-known issues of the model-predictive control strategies, such as high current ripple and the non-constant switching frequency. The stator flux vector has been identified by using a programmable low-pass filter achieving an acceptable estimate which is not affected by the integer offset derived problems, and it does not require high number of calculations as by using a full-order observer. The rotor position feedback signal needed to implement the control strategy has been estimated by using an extended Kalman filter. The machine under test is a 7.5kW doubly-fed induction machine. Simulations are carried out by using the software Matlab/Simulink 2018b showing how the electromagnetic torque and the reactive power of the machine can be successfully controlled without the need of the encoder signal; furthermore low current ripple and high dynamic response can be achieved making the studied control strategy suitable for grid-connected variable speed operation such as wind energy conversion systems.

EPE 2019 - DS3e: Estimation and Identification Methods; Sensorless Control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2019 ECCE Europe - Conference > EPE 2019 - Topic 03: Measurement and Control > EPE 2019 - DS3e: Estimation and Identification Methods; Sensorless Control
	[return to parent folder]

	Comparative Power Loss Analysis of DCM Flyback Transformer Based On FEA, Numeric Simulation, Calculation and Measurements By Halil Alper ONAY	[View] [Download]
Abstract: The flyback transformer is a crucial part of the flyback converter, which has the highest portion oftotal power losses for most applications. Accurately prediction of the power losses due to flybacktransformer early in the design stage provides an advantage about revealing reliable prototypes. In this paper, several loss prediction methods are applied for a 40W universal input and single output DCM flyback transformer as; analytical calculations via well-known Steinmetz and Dowell's formulas, asimulation including numerical solutions, and a finite element analysis (FEA) based investigation. It isshown that the comprehensiveness of the methods accounting for hysteresis losses, eddy currentlosses, DC bias, and fringing effect based losses determine the accuracy of the results. In the paper, itis shown that the more the comprehensiveness, the closer the results to the values of electrical andthermal measurements. The power loss results obtained from theory and measurements with fivedifferent methods are compared and discussed in the detail.

	Electrolytic Capacitor Degradation Monitoring using an On-line Parameter Estimation Scheme involving Sliding Mode Differentiators and a Kalman Filter By José Manuel ANDRADE	[View] [Download]
Abstract: An indication of electrolytic capacitor gradual degradation may be obtained by observing an increase in the equivalent series resistance (ESR) and a decrease in capacitance over time. On-line condition monitoring of these two electrical parameters allows for early detection of the capacitor ageing that can reduce catastrophic failure and their costly consequences. In this paper, a parameter estimation scheme consisting of sliding mode differentiators and a Kalman filter is proposed for electrolytic capacitor degradation monitoring. Satisfactory on-line estimation of the ESR and capacitance under noisy conditions is achieved with the proposed approach as demonstrated through computer simulation results.

	Improved current estimation in paralleled half-bridge converters By Nikola BOSKOVIC	[View] [Download]
Abstract: When paralleling half bridges, their individual currents should be balanced to prevent large circulating currents. This paper improves an existing perturbation-based current estimation method by modifying the perturbation signal allowing a faster estimation of the currents, resulting in a reduction of current stress on components.

	Moving Horizon Parameter Estimation of Permanent Magnet Synchronous Machines By Xinyue LI	[View] [Download]
Abstract: In this paper a general moving horizon estimation (MHE) scheme for online parameter estimation of permanent magnet synchronous machines (PMSMs) is investigated. The optimization problem is solved with the generalized Gauss-Newton method and the real-time iteration approach, which enables the real time implementation of the moving horizon estimation. Furthermore, the proposed estimator is compared with state-of-the-art observers, i.e. extended Kalman filter (EKF) and unscented Kalman filter (UKF), under two test cases. The proposed estimation scheme shows superior performance at the steady state and during the transient both in simulation as well as in experiment.

	Offset Estimation Strategies and Influence on Slotting Signal Resolution in Angular Voltage Step Excitation for Speed Sensorless Control of Induction Machines By Eduardo RODRIGUEZ MONTERO	[View] [Download]
Abstract: The stable operation around zero electrical frequency of sensorless AC drives requires the utilization of external injection techniques (as high frequency or as voltage step) in order to obtain a leakage inductance modulated by the machine inherent saliencies. During the last two decades, numerous attempts have been done in order to reduce the impact of the external injection in terms of current ripple. In this sense, strategies have calculated the machine position from the saliency-offset vector using the actual SVPWM switching states.The saliency-offset vector obtained from one active SVPWM switching state delivers, in induction machines, a huge load and sector dependent offset. Its elimination is critical to obtain the machine saliency (in this work, slotting), as a poor offset amplitude estimation distorts the saliency signal and may lead to an untraceable sensorless rotor angle. This paper will analyze the effect that offset estimation errors produce in the desired saliency vector, and will compare the accuracy of two estimation strategies based on mean and circle-fit functions.

	Online parameter estimator of the DC bus capacitor bank for Doubly-Fed Induction Generators By Cristian BLANCO	[View] [Download]
Abstract: This paper proposes an online parameter estimator of the DC Bus (series resistance, capacitance and in- ductance) used in Doubly-Fed Induction Generators (DFIG) in wind applications. The proposed method relies on electrical variables that are used for the control of DFIG, i.e. stator-side and rotor-side voltages and currents. The estimation is based on a recursive least squares algorithm using transients delivered by the normal operation of the system in wind generation applications. The validity of the proposal is discussed by the theoretical analysis and simulation results.

	Online Parameter Identification of Permanent Magnet Synchronous Machines with Nonlinear Magnetics based on the Inverter Induced Current Slopes and the dq-System By Simon DECKER	[View] [Download]
Abstract: This paper shows a fast online parameter identification method for permanent magnet synchronous machines (PSMs), which uses the PWM (pulse width modulation) excitations and no additional test signals. Based on the inverter induced current slopes, the corresponding applied voltages, the rotor angle and a precise machine model, the model's parameters are calculated. Thereby the machine model consists of the dq-system equations, linearized within one PWM period. For stable and precise identification of the PSM machine parameters, the machine model has to be modified with a regularization approach. The identified parameters enable self-commissioning, tuning of the control parameters, condition monitoring or inner fault detection. In this paper the theoretical approach of the suggested method and simulation results of an equivalent test-bench system are presented.

	Performance Evaluation of Wideband Binary Identification of Grid Impedance Using Grid-connected Inverters By Nabil MOHAMMED	[View] [Download]
Abstract: The application of the pseudo random binary sequence (PRBS) estimation technique for wideband grid impedance estimation using grid-connected inverters has gained more attention recently because of its several advantages. This includes its simple implementation in the control loop of the inverters and the small disturbance amplitude produced. In this context, this paper aims to evaluate the performance influences of the PRBS design parameters bit length, frequency resolution, and disturbance amplitude. This goal is achieved by exploring their effects on the grid impedance estimation accuracy and the produced total distortion (THD\%+PRBS noise) of the inverter output current. A 3-phase balanced inverter system is simulated and investigated using MATLAB/Simulink based on a discrete-time model to show the trade-off of a real implementation such as the PRBS disturbance amplitude and the sampling frequency of the analog-to-digital converters. Simulation results show the trade-off between the investigated PRBS parameters and the accuracy and frequency range of the estimated grid impedance as well as the total distortion.

	Positive-sequence flux estimator based on Second-Order Generalized Integrators for grid synchronization and motor control under imbalanced conditions By Georgios ORFANOUDAKIS	[View] [Download]
Abstract: The estimation of flux as the integral of voltage presents challenges due to known integrator issues such as drift and saturation, while requiring high-pass filters to suppress DC offsets and low-frequency harmonics. High-pass filters in applications such as motor control need to be adaptive, in order to allow operation in an extended frequency range. The estimated fluxes are commonly fed to a Phase-Locked Loop (PLL), to calculate the voltage/flux angle and frequency. Common PLLs for three-phase systems operate on the basis of balanced input signals. Their estimates deteriorate in the existence of imbalance, which can affect the response of the controllers acting based on them. This paper presents an adaptive positive-sequence flux estimator based on Second-Order Generalized Integrators (SOGIs). The balanced fluxes generated by the estimator can be used for synchronization with an imbalanced grid or for sensorless control of a motor over an imbalanced cable. Simulation results are included to illustrate the method's application to an imbalanced grid and its response to transient conditions. Experimental results using a commercial motor drive running a permanent magnet motor (PMM) connected to the drive via a long cable are presented to compare the method with the conventional alternative. _ representative example of instability and loss of control occurring when using conventional integrators for sensorless control of a PMM over a flat armoured cable is included to illustrate the advantage offered by the proposed approach.

	Resource optimal FPGA implementation of a Least-Squares-Estimator for fast and robust online measurement of current slope and absolute value By Andreas LISKE	[View] [Download]
Abstract: This paper presents an improved Least-Squares-Estimator for the fast, non-recursive online measurement of the first derivative and absolute value of a piecewise linear oversampled current signal. Core topic is the partially online calculation of the pseudoinverse matrix in combination with an optimized small lookup table, minimizing memory requirements significantly.

	Scalar/Vector Sensorless Control Combination Solution for Induction Motor Drives at Whole Speed Range Operation By Iker PEÑA-GONZALEZ	[View] [Download]
Abstract: This paper presents a solution for induction motor sensorless drives, especially focused on low fundamental frequencies. The proposed strategy involves a combination of scalar and vector control techniques. Its performance is augmented with three different strategies that improve its behavior in the low frequencies range. Finally, the proposed strategies are verified via simulation and experimental tests, demonstrating the suitability of the solution.

	Sensorless and Modulated Model-Predictive Control for a Doubly Fed Induction Machine By Jacopo RICCIO	[View] [Download]
Abstract: In this paper a sensorless control strategy has been implemented and experimentally validated to control independently the electromagnetic torque and the reactive power of a doubly-fed induction machine. The machine acts as a grid connected generator at variable speed operations around the synchronous speed. This control strategy is based on a model-predictive control strategy with the governing equations represented in a synchronous reference frame aligned to the stator flux. A modulation stage has been introduced in order to overcome the well-known issues of the model-predictive control strategies, such as high current ripple and the non-constant switching frequency. The stator flux vector has been identified by using a programmable low-pass filter achieving an acceptable estimate which is not affected by the integer offset derived problems, and it does not require high number of calculations as by using a full-order observer. The rotor position feedback signal needed to implement the control strategy has been estimated by using an extended Kalman filter. The machine under test is a 7.5kW doubly-fed induction machine. Simulations are carried out by using the software Matlab/Simulink 2018b showing how the electromagnetic torque and the reactive power of the machine can be successfully controlled without the need of the encoder signal; furthermore low current ripple and high dynamic response can be achieved making the studied control strategy suitable for grid-connected variable speed operation such as wind energy conversion systems.