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ABSTRACT: The operation of switch-mode converters results in electromagnetic noise propagating throughout the power electronic system. Pulsewidth modulation (PWM) strategies with fixed switching frequency generate harmonics in the spectra of converter voltages and currents. Random PWM techniques allow the elimination of the harmonics, resulting in a continuous spectrum of noise, i.e., a spectrum retaining all frequency components. As a next step in advanced spectral shaping, a method presented in this paper produces spectral nulls at selected frequencies. This allows the carving of communication channels in the noise and the removal of spectral power at frequencies potentially harmful for the system. The theoretical analysis, computer simulations, implementation details, and experimental results are presented.
IEEE Transactions on Industrial Electronics 08/2011; · 5.16 Impact Factor
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ABSTRACT: This paper presents two improved control strategies for the sensorless control of permanent magnet reluctance synchronous motor (PM-RSM) in wide speed range. The first control strategy is a novel torque referencing strategy, which includes a reference torque calculator for maximum torque/ampere below base speed, and also in flux weakening region where voltage limitations impose constraints on the allowable dq-currents. The second control strategy is an alternative to the first one, with the advantage of being much simpler, involving less off-line computational effort. The PM-RSM motion sensorless control is obtained via model-based ldquoactive fluxrdquo concept. Comprehensive digital simulations for wide speed range operating down to 1 rpm and up to 6000 rpm, demonstrate the effectiveness of both proposed sensorless control strategies. Experimental results between 30 rpm and 3000 rpm are in agreement with digital simulations and validate the theoretical background. The proposed strategies provide stable and reliable operation up to a speed equal eight times the machine base speed (CPSR = 8/1), at low (25%) rated voltage.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: A new family of speed-sensorless sliding-mode observers for induction motor drives has been developed. Three topologies are investigated in order to determine their feasibility, parameter sensitivity, and practical applicability. The most significant feature of all schemes is that they do not require the rotor speed adaptation, i.e., they are inherently sensorless observers. The most versatile and robust is a dual-reference-frame full-order flux observer. The other two schemes are flux observers implemented in stator frame and rotor frame, respectively. These are simpler than the first one and make use of the sliding-mode invariance over a specified range of modeling uncertainties and disturbances. Main theoretical aspects, results of parameter sensitivity analysis, and implementation details are given for each observer in order to allow the comparison. Experimental results with the dual-reference-frame observer, considered the most adequate for practical applications, are presented and discussed. Sensorless operation with a sliding-mode direct-torque-controlled drive at very low speeds is demonstrated. It is concluded that the new proposed observers represent a feasible alternative to the classical speed-adaptive flux observers.
IEEE Transactions on Industrial Electronics 10/2009; · 5.16 Impact Factor
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ABSTRACT: This paper compares four current control structures for selective harmonic compensation in active power filters. All controllers under scrutiny perform the harmonic compensation by using arrays of resonant controllers, one for the fundamental and one for each harmonic of interest, in order to achieve zero phase shift and unity gain in the closed-loop transfer function for selected harmonics. The complete current controller is the superposition of all individual harmonic controllers and may be implemented in various reference frames. The analysis is focused on the comparison of harmonic and total closed-loop transfer functions for each controller. Analytical similarities and differences between schemes in terms of frequency response characteristics are emphasized. It is concluded that three of them have identical harmonic behavior despite the fact that their implementation is significantly different. It emerges that the fourth one has superior behavior and robustness and can stably work at higher frequencies than the others. Theoretical findings and analysis are supported by comparative experimental results on a 7-kVA laboratory setup. The highest harmonic frequency that can be stably compensated with each control method has been determined, indicating significant differences in the control performance.
IEEE Transactions on Industrial Electronics 03/2009; · 5.16 Impact Factor
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ABSTRACT: This paper describes a variable-speed motion-sensorless permanent magnet synchronous generator (PMSG) control system for wind energy generation. The proposed system contains a PMSG connected to the grid by a back-to-back PWM inverter with bidirectional power flow, a line filter, and a transformer. The control system employs PI current controllers with cross- coupling decoupling for both inverters, an active power controller, and a DC link voltage controller. The PMSG rotor speed without using emf integration, and the line voltage frequency are estimated by two PLL based observers. A D- module filter is used to robustly estimate the grid voltage positive- sequence for control in the case of asymmetric voltages. The paper investigates the ride-through performance of this system during asymmetric power grid voltage sags. Design details for various parts of the control system are presented, together with experimental results for single-, two-, and three-phase voltage source sags. Smooth transition through asymmetric voltage sags is demonstrated by all experiments.
Industry Applications Conference, 2007. 42nd IAS Annual Meeting. Conference Record of the 2007 IEEE; 10/2007
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ABSTRACT: The paper presents three methods of selective harmonic compensation with shunt active power filters in different reference frames: harmonic dq-frame, stationary frame and fundamental dq-frame; and shows that the last two methods are derived from the first one. By analyzing their advantages and drawbacks, the paper shows that the last two methods have a more compact mathematical representation which may extend to straightforward DSP implementation. However, the first method, i.e. selective compensation in harmonic dq-frame, is more flexible and allows a better tuning and adjustment, which is of a great importance in practice. For experimental tests only the selective harmonic control in fundamental dq-frame is presented, to demonstrate the selectiveness harmonic current compensation. The experimental results are performed in laboratory conditions on a 7 kVA active filter prototype, indicating a reduction in current THD<sub>i</sub> factor from the existing 27% to 2%.
Power Electronics and Applications, 2007 European Conference on; 10/2007
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ABSTRACT: A new current control scheme for selective harmonic compensation is proposed for shunt active power filters. The method employs an array of resonant current controllers, one for the fundamental, and one for each harmonic, implemented in fundamental reference frame in order to reduce the overall computational effort. The proposed controller design is based on the pole-zero cancellation technique, taking into account the load transfer function at each harmonic frequency. Two design methods are provided, which give controller transfer functions with superior frequency response. The complete current controller is realized as the superposition of all individual harmonic controllers. The frequency response of the entire closed loop control is optimal with respect to filtering objectives, i.e., the system provides good overall stability and excellent selectivity for interesting harmonics. This conclusion is supported by experimental results on a 7.6-kVA laboratory filter, indicating a reduction in current THD factor from 34% to 2%, while the highest harmonic compensated is the 37th harmonic current.
IEEE Transactions on Power Electronics 10/2007; · 4.65 Impact Factor
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ABSTRACT: This paper describes the control and parallel operation of two active power filters (APFs). Possible parallel operation situations of two APFs are investigated, and then the proposed topology is analyzed. The filters are coupled in a combined topology in which one filter is connected in a feedback loop and the other is in a feedforward loop for harmonic compensation. Thus, both active power filters bring their own characteristic advantages, i.e., the feedback filter improves the steady-state performance of the harmonic mitigation and the feedforward filter improves the dynamic response. Another characteristic of the proposed topology is the possibility of joint operation of both filters either as frequency-sharing or load-sharing, with or without redundancy. The frequency-sharing operation is possible due to the control algorithm, which is based on selective harmonic compensation using equivalent harmonic integrators. Implementation details and a discussion on the efficiency improvement for various switching frequencies are provided. The evaluation of the proposed topology concludes that this approach is very practical for achieving both low and high order harmonic compensation and stable grid operation. This is supported by extensive measurement results on a 15-kVA laboratory setup, indicating a reduction in total harmonic current distortion from the existing 30% to less than 2% for a typical adjustable speed drive application
IEEE Transactions on Power Electronics 02/2007; · 4.65 Impact Factor
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ABSTRACT: The paper deals with a wound rotor induction generator (WRIG), also known as the doubly-fed induction generator. A complete experimental set-up is presented and analyzed. It is composed of: WRIG, two power electronics converters connected in the rotor side of WRIG, a line filter, and the data acquisition and control system (dSpace DS 1103). Both converters are commercial units and are vector controlled using appropriate interfaces. They are back-to-back connected, sharing the same DC bus, one supplied through a line filter from the power grid, and the other one with the output on the rotor of the generator. The stator of the generator is directly connected to the power grid. Two stator flux observer topologies were investigated and compared, one with the voltage model in parallel with the current model and the other one with both models connected in series. A speed estimation strategy, which works also during the synchronization procedure, was implemented and tested. It is based on model reference adaptive system (MRAS) principles. All control strategies, the flux observers and the MRAS, were developed in Matlab-Simulinkreg and implemented using a dSpacereg DS1103 single-board control and acquisition interface. Different tests were performed, and sample results are presented and discussed in the paper. The schemes used are illustrated in the paper, and the experimental results are shown and analyzed
IEEE Industrial Electronics, IECON 2006 - 32nd Annual Conference on; 12/2006
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ABSTRACT: The paper describes a new current control structure for active power filters. The proposed current controller uses an array of resonant controllers, one for the fundamental, and one for each harmonic, to achieve zero phase-shift and unity gain in the close-loop transfer function for selected harmonics. The complete current controller is the superposition of all individual harmonic controllers. The novelty consists on the controller structure and design, which is based on the pole-zero cancellation technique, taking into account the load transfer function at each harmonic frequency. An important feature of the proposed control is that the cross-coupling between d- and q-axis is considered and compensated for within the transfer function of each resonant controller. This gives stable operation at higher frequencies for the active filter compared to similar existing controllers. A comparative theoretical and experimental analysis of the proposed control with an existing resonant controller is provided. The results are supported by measurement on a 7 kVA laboratory setup, indicating a reduction in total harmonic current distortion factor from 27 % to less than 2 %
Industry Applications Conference, 2006. 41st IAS Annual Meeting. Conference Record of the 2006 IEEE; 11/2006
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ABSTRACT: Two flux observers for wide speed range direct torque control (DTC) of sensorless induction-motor drives are presented and compared. The first one is a full-order sliding-mode observer with proportional plus integral (PI) compensation, without rotor speed adaptation. The second one is based on a zero phase-delay-improved integrator of the voltage model, which uses only a PI flux amplitude control with stator-flux reference magnitude in the correction loop. In both cases, an estimated dc offset is built up and memorized by the PI integral component and this totally compensates for all dc offsets and drifts originated in the acquisition channels. Two feasible solutions for on-line stator-resistance identification are proposed. Simulation and experimental results prove the accuracy, robustness, and high-dynamic performance of both observers when employed in sensorless DTC drives. The effectiveness of state estimation is confirmed by a steady state and transient sensorless operation at very low speed with rated load torque and step-speed reversal.
IEEE Transactions on Industrial Electronics 07/2006; · 5.16 Impact Factor
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ABSTRACT: Permanent magnet-assisted reluctance synchronous machine (PM-RSM) starter alternator systems are credited with good performance for wide speed range in hybrid electric vehicles. This paper proposes a motion-sensorless motor/generator control of PM-RSM from zero speed up to maximum speed, using direct torque and flux control with space vector modulation. A quasioptimal stator flux reference with a flux versus torque functional is proposed. A stator flux observer in wide speed range uses combined voltage-current models for low speeds, and only the voltage model for medium to high speeds, both in proportional-integral closed loop. A novel rotor speed and position observer with a fusion strategy employs signal injection and only one D-module vector filter in stator reference for low speed, combined with a speed observer from the stator flux vector estimation-for medium-high speed. The proposed system is introduced piece by piece and then implemented on a dSpace 1103 control board with a 350-A metal-oxide-semiconductor field-effect transistor-pulse-width modulation converter connected to a 42-Vdc, 55-Ah battery, and a 140-Nm peak torque PM-RSM. Extensive experimental results from very low speed to high speed, regarding observers and drive responses, including artificial loading (motoring and generating), seem very encouraging for future starter-alternator systems
IEEE Transactions on Power Electronics 06/2006; · 4.65 Impact Factor
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ABSTRACT: State observers are key components of modern ac drives. The paper presents a comparative analysis of two state observers for induction-motor (IM) drives: the speed-adaptive observer and the inherently sensorless observer. The adaptive observer employs the time-variable full-order motor model with the rotor speed as the adaptive quantity. Thus, the speed estimation accuracy significantly impacts on the flux observer. It is shown that the popular model reference adaptive system (MRAS) speed estimator displays reduced bandwidth, and does not deliver adequate performance for the flux estimation. The inherently sensorless observer employs a full-order dual reference-frame model in order to eliminate the speed adaptation. In this way, it becomes decoupled from the speed estimator and its performance is superior to that of its adaptive counterpart. Theoretical aspects and comparative simulation results are discussed for both observers. Comparative experimental results for both observers are presented. Very low-speed-operation (3 r/min) capability of the drive with the sensorless observer is demonstrated.
IEEE Transactions on Industrial Electronics 03/2006; · 5.16 Impact Factor
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ABSTRACT: A sensorless induction machine drive is presented, in which the principles of variable-structure control and direct torque control (DTC) are combined to ensure high-performance operation in the steady state and under transient conditions. The drive employs a new torque and flux controller, the "linear and variable-structure control", which realizes accurate and robust control in a wide speed range. Conventional DTC transient merits are preserved, while the steady-state behavior is significantly improved. The full-order state observer is a sliding-mode one, which does not require the rotor speed adaptation and provides accurate state estimation in the entire speed range. The proposed scheme is a complete variable-structure solution that allows persistent sensorless operation of the drive at very low speeds, including zero and 3 r/min, with full load. Simulations and extensive experimental results confirm the robustness, accuracy, quickness, and low-chattering operation of the drive.
IEEE Transactions on Industry Applications 04/2005; · 1.66 Impact Factor
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ABSTRACT: A sensorless hybrid direct torque control (DTC) drive for high-volume low-cost industrial, domestic, and automotive applications has been developed using the inexpensive TMS329F243 digital signal processor controller. Under transient operating conditions, the drive is controlled using the classic bang-bang DTC. In the steady state, using linear torque and flux controllers, the control system generates a reference voltage vector for the inverter feeding the induction motor. The vector is then realized using the well-known space-vector pulsewidth modulation (SVPWM) technique. As a result, the irregular switching pattern typical for the classic DTC strategy is replaced with a quasi-optimal one, typical for the SVPWM. Description of the drive, including a novel motor state observer, is followed by selected experimental results confirming its excellent operating characteristics.
IEEE Transactions on Industrial Electronics 11/2004; · 5.16 Impact Factor
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ABSTRACT: A family of variable-structure controllers for induction machine drives is presented, in which the principles of direct torque control (DTC), variable-structure control (VSC), and space-vector pulsewidth modulation are combined to ensure high-performance operation, both in the steady state and under transient conditions. Three new VSC schemes are designed following the DTC voltage-control-based philosophy. These provide robust, fast, and accurate torque and flux control, without the penalty of high chattering. Comparative results demonstrate that proposed techniques preserve the DTC transient merits, while the steady-state behavior is significantly improved. Experimental results prove the strong robustness, accuracy, quickness, and low-ripple sensor-less operation of a drive that uses the new schemes.
IEEE Transactions on Industrial Electronics 09/2004; · 5.16 Impact Factor
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ABSTRACT: Direct torque control (DTC) is known to produce fast response and robust control in ac adjustable-speed drives. However, in the steady-state operation, notable torque, flux, and current pulsations occur. A new, direct torque and flux control strategy based on variable-structure control and space-vector pulsewidth modulation is proposed for induction motor sensorless drives. The DTC transient merits and robustness are preserved and the steady-state behavior is improved by reducing the torque and flux pulsations. A sliding-mode observer using a dual reference frame motor model is introduced and tested. Simulations and comparative experimental results with the proposed control scheme, versus classic DTC, are presented. Very-low-speed sensorless operation (3 r/min) is demonstrated.
IEEE Transactions on Industry Applications 04/2004; · 1.66 Impact Factor
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ABSTRACT: A sensorless induction motor drive is presented, in which the principles of sliding-mode control, direct torque control (DTC), and space-vector modulation are combined to ensure high-performance operation, both in the steady state and under transient conditions. Merits of the classic DTC transient behavior are preserved, while the steady-state operation is significantly improved. The torque and flux controllers, and motor state observer are of the sliding-mode type. The inverter is directly controlled on the basis of torque and flux errors, using space-vector pulsewidth modulation. Computer simulations and experimental results presented demonstrate the robustness, accuracy, quickness, and low-chattering, wide-speed-range operation of the drive.
IEEE Transactions on Industry Applications 02/2004; · 1.66 Impact Factor
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ABSTRACT: A variable structure, direct torque controlled, sensorless induction machine drive is presented, in which the principles of Direct Torque Control (DTC), Variable Structure Control, and Space Vector Pulse Width Modulation are combined to ensure high-performance operation, both in the steady state and under transient conditions. The classical DTC transient merits are preserved, while the steady-state behavior is significantly Improved. The full-order Sliding Mode Observer does not require speed information and provides accurate state estimation in wide speed range. The proposed scheme is a complete Variable Structure solution that allows sensorless operation of the drive at very low speeds, including zero and three rpm, full load. Simulations and extensive experimental results confirm the robustness, accuracy, quickness, and low-chattering operation of the drive.
Electric Machines and Drives Conference, 2003. IEMDC'03. IEEE International; 07/2003
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[show abstract]
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ABSTRACT: A robust torque estimator for induction motor drives is described.
The estimator is based on a full-order MRAS flux observer and
implemented in the TMC320C243 DSP controller. Low price of the DSP
controller allows application of the torque estimator in inexpensive
drive systems, both uncontrolled and controlled, for industrial and
domestic applications. Implementation details and experimental results
are presented
Electric Machines and Drives Conference, 2001. IEMDC 2001. IEEE International; 02/2001
