IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society, 2019
The conditions for minimum losses in a salient-pole wound-field synchronous machine (WFSM) drive ... more The conditions for minimum losses in a salient-pole wound-field synchronous machine (WFSM) drive are studied in this paper. The drive comprises a WFSM energized by a stator inverter and excited by a dc-dc converter both tied to a DC link. The minimum-loss operation is formulated as a nonlinear constrained optimization problem with equality constraints (e.g, torque command), and inequality constraints (flux, voltage and current limits). Lagrange multipliers are applied to solve this problem analytically. At low load, the torque demand can be met using different values for two independent electric variables (e.g. stator flux and field current magnitude). These can be optimized, thereby leading to two optimal implicit conditions. At higher load, when the stator flux reaches the maximum value, the free variables reduce to one and yield a single implicit optimal condition. For these two scenarios, the paper presents analytical derivations of the optimal conditions and numerical validatio...
This paper addresses the minimum-loss control of the Dual-VSI DFIG system connected to a dc link.... more This paper addresses the minimum-loss control of the Dual-VSI DFIG system connected to a dc link. The minimum-loss operating conditions for fieldoriented control based on the airgap flux are obtained analytically using Lagrange multipliers and validated with numerical optimization. As the main contribution of the paper, the analysis accounts for core and VSI losses, providing the optimal stator frequency law and rotor/stator d-axis current split ratio, and an implicit expression for the optimal flux trajectory formulated as equality between suitable d-axis and q-axis loss functions. In the proposed implementation, this implicit condition is enforced by using a proportional-integral controller and avoiding look-up tables. Furthermore, the stator and rotor VSI controls are implemented in two independent DSPs with no communication, which may ease the use of off-the-shelf VSI units. The optimal conditions and control strategy are fully validated by simulations and experiments on a prototype. The main scope of application is wind-energy dc-grid technology.
The doubly fed induction machine has been traditionally adopted in adjustable-speed ac power gene... more The doubly fed induction machine has been traditionally adopted in adjustable-speed ac power generation drives in order to take advantage of the reduced rating for the power electronic interface. Aside this well-established application where the doubly fed induction generator (DFIG) is controlled by a back-toback converter, recent literature records a growing interest toward un-conventional DFIG drives for dc power generation, combining DFIG high control freedom with simplified power electronic interfaces to achieve an overall cheap and fully controllable system. Despite several concepts have been demonstrated on small-scale rigs, there is a lack of systematic comparison among different topologies and control solutions. This paper bridges this gap by providing a review of recent topologies, their control, design and performance, and operation issues. As major novelties, this paper includes off-spec performance comparison of different torque-ripple mitigation strategies, discussion of sizing requirements for generator and power electronics, fundamental aspects of the behavior under voltage dips, and priorities and challenges for future research on the subject. Index Terms-DC grid, doubly fed induction machine, fieldoriented control (FOC), microgrid, rectifier. NOMENCLATURE a Referring factor for the equivalent circuit. e Induced electromotive force (p.u.). i s , i r Stator and rotor current (p.u.). i dc1 , i dc2 Diode bridge and inverter dc current (p.u.). K r Resonant controller parameter (p.u.). k p , k i Parameters of the PI controller (p.u.). k s Integral gain of the frequency controller (p.u.). L s , L m , L r Stator, magnetizing, and rotor inductance (p.u.). m Voltage ratio u dc /(2/3U sn). n 12 Stator/rotor turn ratio. p g , p f e Airgap power, core losses (p.u.).
This paper describes an innovative solution for the power supply of a fast field cycling (FFC) nu... more This paper describes an innovative solution for the power supply of a fast field cycling (FFC) nuclear magnetic resonance (NMR) spectrometer considering its low power consumption, portability and low cost. In FFC cores, the magnetic flux density must be controlled in order to perform magnetic flux density cycles with short transients, while maintaining the magnetic flux density levels with high accuracy and homogeneity. Typical solutions in the FFC NMR literature use current control to get the required magnetic flux density cycles, which correspond to an indirect magnetic flux density control. The main feature of this new relaxometer is the direct control of the magnetic flux density instead of the magnet current, in contrast with other equipment available in the market. This feature is a great progress because it improves the performance. With this solution it is possible to compensate magnetic field disturbances and parasitic magnetic fields guaranteeing, among other possibilities...
The severe torque ripple normally occurring in the DFIG-dc system can cause premature failure of ... more The severe torque ripple normally occurring in the DFIG-dc system can cause premature failure of mechanical components and shorten the life of the drive train. This paper addresses the torque ripple issue by proposing a predictive direct torque control strategy which delivers at the same time torque ripple suppression and minimization of losses. The existing control algorithms for torque ripple mitigation are mostly based on resonant controllers and repetitive control forcing the compensation signal either through the current chain or directly into the rotor voltage commands. All these techniques lead to structures with multiple controllers whose tuning is not straightforward. Furthermore, they are very sensitive to the operating frequency, making optimized operation with variable frequency highly challenging. Conversely, the proposed algorithm predicts directly the best rotor voltage space vector to minimize torque ripple and track a prescribed rotor flux amplitude to minimize losses, with no current control chain. As confirmed by simulations and experiments, the strategy allows large stator frequency variations as required by the optimal flux command for minimum losses, whilst ensuring effective torque ripple compensation.
... Titre du document / Document title. Control of a reversible AC/DC voltage converter based on ... more ... Titre du document / Document title. Control of a reversible AC/DC voltage converter based on input-output linearization. Auteur(s) / Author(s). MARQUES GD (1) ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). ... Corriente contínua. ; Línea corriente. ; Control lineal. ; ...
Ieee Transactions on Industrial Electronics, Jun 1, 2013
This paper presents a new sensorless method for the direct estimation of the slip position of the... more This paper presents a new sensorless method for the direct estimation of the slip position of the wound-rotor induction machine. The main purpose of this study is to implement the control of the doubly fed induction machine (DFIM). The method computes directly the slip position as the difference between the position of the air gap power vector (q e , p e) and the position of the measured rotor current. The method does not need any information about the stator or rotor fluxes, and so, it is only indirectly dependent of the flux dynamics. Because the slip position is directly obtained, it is not necessary the knowledge of the stator flux to implement field orientation. The method is sensitive to errors in the stator inductance parameter. A general analytic expression for the estimation error is presented. The sensitivity becomes important when the rotor current is small. To overcome the sensitivity problem, an open-loop on-line adjustment is proposed and tested with acceptable results. Experimental results confirm that the method is appropriate for the vector control of the DFIM.
... The computer simulation program presented in this paper can be used to examine the transient ... more ... The computer simulation program presented in this paper can be used to examine the transient perform-ance of the slip power recovery system for the proper rating of semiconductor devices and other components such as the DC inductor. ... 2 Electrical machine simulation ...
2013 IEEE International Symposium on Sensorless Control for Electrical Drives and Predictive Control of Electrical Drives and Power Electronics (SLED/PRECEDE), 2013
ABSTRACT This paper presents a frequency regulation system and a sensorless method for the direct... more ABSTRACT This paper presents a frequency regulation system and a sensorless method for the direct estimation of the slip position of the wound-rotor induction machine connected to a DC link, performing a torque control. Since the stator is connected to the DC link through a diode bridge, it is also necessary to implement the stator frequency regulation. Connecting the DFIG to a DC link using a diode bridge on the stator brings considerable benefits, because only a dc/ac power electronic inverter is required. In this system the magnetizing current is necessarily fed by the rotor: this makes the considered sensorless method particularly appropriate, because, under mismatched parameters, it gives small estimation errors. Simulation and experimental results are presented matching and showing good performances.
This paper deals with the sensorless vector control of a doubly fed induction generator (DFIG) wh... more This paper deals with the sensorless vector control of a doubly fed induction generator (DFIG) whose stator is connected by a rectifier to a dc link, which also feeds the rotor-side inverter. A noticeable reduction of the costs can be achieved by this topology, because only a single inverter and a diode rectifier are needed instead of the traditional back-to-back converter. A sensorless stator-flux-oriented control is implemented by using an observer, which directly computes the necessary slip angle based on of the air-gap power and without the need of the stator flux estimation. The direct-axis component of the rotor current is adjusted to regulate the stator frequency near the rated value. In order to track the actual stator frequency, the phase-locked-loop approach is used. The control method is validated by simulations and experimental results obtained using a small-rating laboratory setup. Index Terms-Doubly fed induction generator (DFIG), frequency regulation, phase-locked loop (PLL), sensorless control. NOMENCLATURE e s Stator electromotive force (p.u.). i Stator or rotor current (p.u.). k ratio L s /M. L s , M Stator and mutual inductance (p.u.). L lk Leakage inductance (p.u.). p g Power transferred across the air gap (p.u.). p f e Electrical power to stator due to magnetic losses (p.u.). r s Stator resistance (p.u.). u Stator voltage (p.u.). γ Slip position estimation error. γ m Electrical position of the rotor. γ s Electrical position of the stator flux vector. γ sr Estimated electrical slip angle. γ dq Rotor current position on field coordinates. γ r Rotor current position on rotor coordinates. ψ Flux linkage (p.u.). ω b Base value of the angular frequency (rad/s). ω c Bandwidth of the frequency estimator (p.u.). ω cg Closed-loop bandwidth of frequency control (p.u.).
This paper presents a control method for the Doubly-fed Induction Generator connected to a dc lin... more This paper presents a control method for the Doubly-fed Induction Generator connected to a dc link through a diode bridge on the stator. In this system, the rotor is fed, at the slip frequency, by a PWM electronic converter and the stator is directly connected to the dc link using a simple diode bridge. The cost of power electronics is reduced in this system when compared with the classic DFIG machine because the system uses less one PWM inverter and additionally it uses a diode bridge. The application in mind is for microgrids. Microgrids need several elements that should work together. The usual way to connect these elements is to use power electronic devices in a common dc link. This paper presents a new form for the DFIG for this application and presents a control system for the inner control loop. Simulation and experimental results show that the system can work acceptably using a stator frequency near the rated frequency of the machine.
ABSTRACT The operation of a doubly fed induction generator (DFIG) connected to a dc net is consid... more ABSTRACT The operation of a doubly fed induction generator (DFIG) connected to a dc net is considered in this study. The dc net is connected to the stator of the DFIG by a diode rectifier and simultaneously feeds the rotor-side inverter, which is used to control the machine. When the dc net operates at constant voltage, this solution preserves the possibility to work with a low flux at low speed, and, at the same time, reduces the cost of the power electronics. In fact, the only needed electronic converter is the rotor inverter designed for a fraction of the machine power. After introducing a simple control technique, the study proposes an analytic model for the steady-state operation and discusses the design specifications of the DFIG for given values of the dc voltage and of the power of the wind turbine. The most appropriate stator and rotor rated powers, rated stator voltage and turns ratio of the DFIG are deduced. Simulations and experimental results are presented in order to support the theory.
IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society, 2019
The conditions for minimum losses in a salient-pole wound-field synchronous machine (WFSM) drive ... more The conditions for minimum losses in a salient-pole wound-field synchronous machine (WFSM) drive are studied in this paper. The drive comprises a WFSM energized by a stator inverter and excited by a dc-dc converter both tied to a DC link. The minimum-loss operation is formulated as a nonlinear constrained optimization problem with equality constraints (e.g, torque command), and inequality constraints (flux, voltage and current limits). Lagrange multipliers are applied to solve this problem analytically. At low load, the torque demand can be met using different values for two independent electric variables (e.g. stator flux and field current magnitude). These can be optimized, thereby leading to two optimal implicit conditions. At higher load, when the stator flux reaches the maximum value, the free variables reduce to one and yield a single implicit optimal condition. For these two scenarios, the paper presents analytical derivations of the optimal conditions and numerical validatio...
This paper addresses the minimum-loss control of the Dual-VSI DFIG system connected to a dc link.... more This paper addresses the minimum-loss control of the Dual-VSI DFIG system connected to a dc link. The minimum-loss operating conditions for fieldoriented control based on the airgap flux are obtained analytically using Lagrange multipliers and validated with numerical optimization. As the main contribution of the paper, the analysis accounts for core and VSI losses, providing the optimal stator frequency law and rotor/stator d-axis current split ratio, and an implicit expression for the optimal flux trajectory formulated as equality between suitable d-axis and q-axis loss functions. In the proposed implementation, this implicit condition is enforced by using a proportional-integral controller and avoiding look-up tables. Furthermore, the stator and rotor VSI controls are implemented in two independent DSPs with no communication, which may ease the use of off-the-shelf VSI units. The optimal conditions and control strategy are fully validated by simulations and experiments on a prototype. The main scope of application is wind-energy dc-grid technology.
The doubly fed induction machine has been traditionally adopted in adjustable-speed ac power gene... more The doubly fed induction machine has been traditionally adopted in adjustable-speed ac power generation drives in order to take advantage of the reduced rating for the power electronic interface. Aside this well-established application where the doubly fed induction generator (DFIG) is controlled by a back-toback converter, recent literature records a growing interest toward un-conventional DFIG drives for dc power generation, combining DFIG high control freedom with simplified power electronic interfaces to achieve an overall cheap and fully controllable system. Despite several concepts have been demonstrated on small-scale rigs, there is a lack of systematic comparison among different topologies and control solutions. This paper bridges this gap by providing a review of recent topologies, their control, design and performance, and operation issues. As major novelties, this paper includes off-spec performance comparison of different torque-ripple mitigation strategies, discussion of sizing requirements for generator and power electronics, fundamental aspects of the behavior under voltage dips, and priorities and challenges for future research on the subject. Index Terms-DC grid, doubly fed induction machine, fieldoriented control (FOC), microgrid, rectifier. NOMENCLATURE a Referring factor for the equivalent circuit. e Induced electromotive force (p.u.). i s , i r Stator and rotor current (p.u.). i dc1 , i dc2 Diode bridge and inverter dc current (p.u.). K r Resonant controller parameter (p.u.). k p , k i Parameters of the PI controller (p.u.). k s Integral gain of the frequency controller (p.u.). L s , L m , L r Stator, magnetizing, and rotor inductance (p.u.). m Voltage ratio u dc /(2/3U sn). n 12 Stator/rotor turn ratio. p g , p f e Airgap power, core losses (p.u.).
This paper describes an innovative solution for the power supply of a fast field cycling (FFC) nu... more This paper describes an innovative solution for the power supply of a fast field cycling (FFC) nuclear magnetic resonance (NMR) spectrometer considering its low power consumption, portability and low cost. In FFC cores, the magnetic flux density must be controlled in order to perform magnetic flux density cycles with short transients, while maintaining the magnetic flux density levels with high accuracy and homogeneity. Typical solutions in the FFC NMR literature use current control to get the required magnetic flux density cycles, which correspond to an indirect magnetic flux density control. The main feature of this new relaxometer is the direct control of the magnetic flux density instead of the magnet current, in contrast with other equipment available in the market. This feature is a great progress because it improves the performance. With this solution it is possible to compensate magnetic field disturbances and parasitic magnetic fields guaranteeing, among other possibilities...
The severe torque ripple normally occurring in the DFIG-dc system can cause premature failure of ... more The severe torque ripple normally occurring in the DFIG-dc system can cause premature failure of mechanical components and shorten the life of the drive train. This paper addresses the torque ripple issue by proposing a predictive direct torque control strategy which delivers at the same time torque ripple suppression and minimization of losses. The existing control algorithms for torque ripple mitigation are mostly based on resonant controllers and repetitive control forcing the compensation signal either through the current chain or directly into the rotor voltage commands. All these techniques lead to structures with multiple controllers whose tuning is not straightforward. Furthermore, they are very sensitive to the operating frequency, making optimized operation with variable frequency highly challenging. Conversely, the proposed algorithm predicts directly the best rotor voltage space vector to minimize torque ripple and track a prescribed rotor flux amplitude to minimize losses, with no current control chain. As confirmed by simulations and experiments, the strategy allows large stator frequency variations as required by the optimal flux command for minimum losses, whilst ensuring effective torque ripple compensation.
... Titre du document / Document title. Control of a reversible AC/DC voltage converter based on ... more ... Titre du document / Document title. Control of a reversible AC/DC voltage converter based on input-output linearization. Auteur(s) / Author(s). MARQUES GD (1) ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). ... Corriente contínua. ; Línea corriente. ; Control lineal. ; ...
Ieee Transactions on Industrial Electronics, Jun 1, 2013
This paper presents a new sensorless method for the direct estimation of the slip position of the... more This paper presents a new sensorless method for the direct estimation of the slip position of the wound-rotor induction machine. The main purpose of this study is to implement the control of the doubly fed induction machine (DFIM). The method computes directly the slip position as the difference between the position of the air gap power vector (q e , p e) and the position of the measured rotor current. The method does not need any information about the stator or rotor fluxes, and so, it is only indirectly dependent of the flux dynamics. Because the slip position is directly obtained, it is not necessary the knowledge of the stator flux to implement field orientation. The method is sensitive to errors in the stator inductance parameter. A general analytic expression for the estimation error is presented. The sensitivity becomes important when the rotor current is small. To overcome the sensitivity problem, an open-loop on-line adjustment is proposed and tested with acceptable results. Experimental results confirm that the method is appropriate for the vector control of the DFIM.
... The computer simulation program presented in this paper can be used to examine the transient ... more ... The computer simulation program presented in this paper can be used to examine the transient perform-ance of the slip power recovery system for the proper rating of semiconductor devices and other components such as the DC inductor. ... 2 Electrical machine simulation ...
2013 IEEE International Symposium on Sensorless Control for Electrical Drives and Predictive Control of Electrical Drives and Power Electronics (SLED/PRECEDE), 2013
ABSTRACT This paper presents a frequency regulation system and a sensorless method for the direct... more ABSTRACT This paper presents a frequency regulation system and a sensorless method for the direct estimation of the slip position of the wound-rotor induction machine connected to a DC link, performing a torque control. Since the stator is connected to the DC link through a diode bridge, it is also necessary to implement the stator frequency regulation. Connecting the DFIG to a DC link using a diode bridge on the stator brings considerable benefits, because only a dc/ac power electronic inverter is required. In this system the magnetizing current is necessarily fed by the rotor: this makes the considered sensorless method particularly appropriate, because, under mismatched parameters, it gives small estimation errors. Simulation and experimental results are presented matching and showing good performances.
This paper deals with the sensorless vector control of a doubly fed induction generator (DFIG) wh... more This paper deals with the sensorless vector control of a doubly fed induction generator (DFIG) whose stator is connected by a rectifier to a dc link, which also feeds the rotor-side inverter. A noticeable reduction of the costs can be achieved by this topology, because only a single inverter and a diode rectifier are needed instead of the traditional back-to-back converter. A sensorless stator-flux-oriented control is implemented by using an observer, which directly computes the necessary slip angle based on of the air-gap power and without the need of the stator flux estimation. The direct-axis component of the rotor current is adjusted to regulate the stator frequency near the rated value. In order to track the actual stator frequency, the phase-locked-loop approach is used. The control method is validated by simulations and experimental results obtained using a small-rating laboratory setup. Index Terms-Doubly fed induction generator (DFIG), frequency regulation, phase-locked loop (PLL), sensorless control. NOMENCLATURE e s Stator electromotive force (p.u.). i Stator or rotor current (p.u.). k ratio L s /M. L s , M Stator and mutual inductance (p.u.). L lk Leakage inductance (p.u.). p g Power transferred across the air gap (p.u.). p f e Electrical power to stator due to magnetic losses (p.u.). r s Stator resistance (p.u.). u Stator voltage (p.u.). γ Slip position estimation error. γ m Electrical position of the rotor. γ s Electrical position of the stator flux vector. γ sr Estimated electrical slip angle. γ dq Rotor current position on field coordinates. γ r Rotor current position on rotor coordinates. ψ Flux linkage (p.u.). ω b Base value of the angular frequency (rad/s). ω c Bandwidth of the frequency estimator (p.u.). ω cg Closed-loop bandwidth of frequency control (p.u.).
This paper presents a control method for the Doubly-fed Induction Generator connected to a dc lin... more This paper presents a control method for the Doubly-fed Induction Generator connected to a dc link through a diode bridge on the stator. In this system, the rotor is fed, at the slip frequency, by a PWM electronic converter and the stator is directly connected to the dc link using a simple diode bridge. The cost of power electronics is reduced in this system when compared with the classic DFIG machine because the system uses less one PWM inverter and additionally it uses a diode bridge. The application in mind is for microgrids. Microgrids need several elements that should work together. The usual way to connect these elements is to use power electronic devices in a common dc link. This paper presents a new form for the DFIG for this application and presents a control system for the inner control loop. Simulation and experimental results show that the system can work acceptably using a stator frequency near the rated frequency of the machine.
ABSTRACT The operation of a doubly fed induction generator (DFIG) connected to a dc net is consid... more ABSTRACT The operation of a doubly fed induction generator (DFIG) connected to a dc net is considered in this study. The dc net is connected to the stator of the DFIG by a diode rectifier and simultaneously feeds the rotor-side inverter, which is used to control the machine. When the dc net operates at constant voltage, this solution preserves the possibility to work with a low flux at low speed, and, at the same time, reduces the cost of the power electronics. In fact, the only needed electronic converter is the rotor inverter designed for a fraction of the machine power. After introducing a simple control technique, the study proposes an analytic model for the steady-state operation and discusses the design specifications of the DFIG for given values of the dc voltage and of the power of the wind turbine. The most appropriate stator and rotor rated powers, rated stator voltage and turns ratio of the DFIG are deduced. Simulations and experimental results are presented in order to support the theory.
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Papers by Gil Marques