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ABSTRACT: A new method to estimate the rotor position of permanent magnet synchronous motor (PMSM) drives over a wide speed range, including zero frequency is introduced. The method measures the motor current derivative in response to the standard pulse width modulation (PWM) sequence to estimate rotor position. No additional signal injection or separate test vectors are required although modification is needed when narrow PWM voltage vectors occur. Three compensation techniques are proposed to improve the quality of the position estimation and reduce current distortion when narrow vectors are used for position estimation. Experimental results for sensorless speed and position control of a 4 kW PMSM verify the effectiveness of the proposed techniques.
IET Electric Power Applications 05/2011; · 1.17 Impact Factor
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ABSTRACT: This paper introduces a new scheme to track the rotor slotting saliency in induction motors by using the measurement of current derivatives in response to test vectors imposed during null switching vectors of a standard PWM scheme by using 3 H-bridges connected in series with a 2-Level inverter. The scheme aims to reduce the current distortion usually introduced by applying the sensorless control strategies in 2-Level inverters. The H-Bridges can generate low voltage test vectors which can be used to track the rotor slotting saliency and the same time reduce the distortion in the current directly, as well as shortening the minimum pulse width (t<sub>min</sub>) which adds a further improvement to current distortion without compromising the quality of the sensorless performance of the system. Moreover, the new technique can work in a wide speed range and its implementation requires only the minimum of control modifications to the operation of the multilevel inverter as the proposed application of this sensorless technique is to high power multilevel converters which use a combination of series connected GTO and IGBT based H-Bridges to achieve a reasonable quality medium voltage waveform for motor drives. Also some automotive drives have recently been proposed which use the same specific topology as used in this work.
Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
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ABSTRACT: Advantages of operating a Permanent Magnet Synchronous Machine (PMSM) without a position sensor are many and are well known. This paper presents a study of the effects of space harmonics in the incremental inductances and their impact on the machine saliency. The effects of space harmonics exclusively due to the machine (i.e., the saturation saliency distribution) are given particular consideration. The results are illustrated through inductance analysis and measurement of inductance profiles of two similar PMSM machines. The space harmonics in the inductance profiles are correlated with the position estimate distortions through a Matlab/Simulink embedding finite element (FE) machine simulation. Significant differences in sensorless operation of the two machines are found which correlate to the inductance profiles. This illustrates that inductance profiling can inform upon machine design in order to improve sensorless capabilities.
Power Electronics and Motion Control Conference (EPE/PEMC), 2010 14th International; 10/2010
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ABSTRACT: This paper introduces a new scheme to track the rotor position of an induction motor, which reduces distortion introduced into the motor current by sensorless control techniques. The scheme uses the measurement of current derivatives in response to test vectors imposed during the null switching vectors of a standard PWM scheme. The test vectors are derived from H-Bridges connected in series with the main converter. These H-Bridges generate a lower voltage test vectors which will reduce the distortion in the motor current directly without compromising the quality of the sensorless performance of the system. The proposed application of this sensorless technique is to high power multilevel converters which use a combination of series connected GTO and IGBT based H bridges to achieve a reasonable quality medium voltage waveform for motor drives, although there are now similar topologies proposed for automotive drives. The implementation of this sensorless technique in such applications requires modification to he control software only.
Power Electronics, Machines and Drives (PEMD 2010), 5th IET International Conference on; 05/2010
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ABSTRACT: The principle of position estimation and sensorless control of a matrix converter fed permanent magnet synchronous motor (PMSM) has been reported before, where the current derivatives of motor line currents were measured by di/dt sensors to construct position signals. This paper presents a different implementation that eliminates the di/dt sensors. The current derivatives are calculated by measuring current changes within certain vectors. Experimental results show that the performance of sensorless control is not compromised compared with that achieved by using the di/dt sensors. Additionally, careful selection of current measurement instants ensures no higher current ripples are introduced.
Industrial Electronics, 2009. IECON '09. 35th Annual Conference of IEEE; 12/2009
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ABSTRACT: In this paper, the performance of a grid-connected wind energy conversion system (WECS), based on a doubly fed induction generator (DFIG) fed by a matrix converter (MC), is presented. The MC replaces the back-to-back converters conventionally used to control a DFIG. The MC is operated with close-to-unity power factor at the grid side. Stability issues related to the operation of the MC in the proposed WECS are discussed. A small signal model is used to investigate the dynamic performance of the two control arrangements discussed in this paper. Experimental results, obtained with a 4-kW prototype, are presented and fully discussed in this paper. The performance of the system for variable speed generation is verified using the emulation of a variable speed wind turbine implemented with a digitally controlled dc machine.
IEEE Transactions on Industrial Electronics 11/2009; · 5.16 Impact Factor
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ABSTRACT: A sensorless control system for a surface mounted permanent magnet (PM) machine is developed which uses measurement of motor current derivative during the fundamental PWM vector excitation only. Vector extension is required when the vector width falls below a minimum time duration. The extension is made to allow the high frequency switching oscillations due to parasitic capacitances in the drive to die down. This paper introduces a new method to reduce these high frequency switching oscillations, in order to achieve position estimation with lower motor current distortion. Experimental results demonstrate the improved sensorless speed and position control using the proposed method.
Power Electronics and Applications, 2009. EPE '09. 13th European Conference on; 10/2009
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ABSTRACT: In this paper, a new control system to regulate the reactive power supplied by a variable-speed wind energy conversion system (WECS), based on an induction generator fed by a matrix converter (MC), is presented. The control system discussed in this paper is based on an input current observer, implemented using an estimation of the modulation matrix, and a nonlinear control loop that regulates the displacement angle at the MC input. The reactive power capability of the proposed system is also investigated. The work presented in this paper demonstrates that, for the proposed WECS, the maximum reactive power supplied to the grid is about 40% of the nominal value. Experimental results obtained from an experimental prototype are presented in this paper. The performance of the system using a wind turbine emulator and typical wind profiles is discussed in this paper.
IEEE Transactions on Industrial Electronics 03/2009; · 5.16 Impact Factor
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ABSTRACT: The paper presents the use of the inherent high frequency PWM harmonics for sensorless control of AC machines. The amplitude and position of the PWM voltage harmonics cannot be controlled and depends on the fundamental machine operation. The paper examines the feasibility of sensorless control based on the extracted rotor bar slot position information in the case of a cage induction machine. The position signal demodulation and compensation schemes used are discussed. Experimental results of sensorless torque, speed and position control at loaded conditions including zero excitation and zero speed are given for an off-the-shelf induction machine.
Industry Applications Society Annual Meeting, 2008. IAS '08. IEEE; 11/2008
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ABSTRACT: The design method of adaptive rotor flux observer gain to improve stability at low speed and regenerating mode was proposed in [1]. The method is based on the stability analysis. The stability analysis utilizes the linearized model considering all systems including each control loop. Therefore the proposed method considers the effects of motor constants and control circuit constants. The stability analysis using the transfer function for rotor speed considers the arrangement of pole and zero and the steady state error. The rotor flux observer gain which improves the stability for each operating condition was clarified. Also the real time tuning method of observer gain was proposed in [1]. The validity of the proposed method was confirmed on the simulation using Matlab Simulink and the experiment. Then this paper evaluates the experimental performance for low speed and regenerating operation of sensor-less vector control system of induction motor using observer gain tuning.
Power Electronics and Motion Control Conference, 2008. EPE-PEMC 2008. 13th; 10/2008
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ABSTRACT: In this paper the control of a grid-connected Wind Energy Conversion System (WECS), based on a sensorless vector controlled Doubly-Fed Induction Generator (DFIG) fed by a matrix converter, is presented. The matrix converter is controlled using a space vector modulation algorithm. Stability issues related to the operation of the WECS connected to the grid using a matrix converter are also discussed in this work. The influence of a synchronous rotating filter in the dynamic of the proposed WECS is analysed. A Model Reference Adaptive System (MRAS) observer for sensorless control of the proposed WECS is used in this work. Using the speed estimated by the MRAS observer the electrical torque of the induction generator is regulated in order to drive the WECS to the operating point where the aerodynamic efficiency is maximized. Experimental results, obtained with a 3.5 kW prototype are presented, and fully discussed in this work.
Industrial Electronics, 2008. ISIE 2008. IEEE International Symposium on; 08/2008
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ABSTRACT: It has been well established in the literature that inverter non-linearity effects afflict saliency based sensorless drives operating in the low and zero speed region. The inverter non-linearity leads to the generation of signals that corrupt the useful position signals. In certain cases, the magnitude of the former signals is comparable if not higher to the latter. Various compensation techniques to overcome this effect have been published in the literature. This paper is concerned with the sensorless technique utilizing the current derivatives during the zero voltage vector states without additional test signal injection, as proposed in. This paper incorporates the varying on-state resistance of the inverter power devices in the system model to explain the corrupting signal experienced in. Knowledge of the source of the corrupting signals facilitates compensation and determines its applicability. The same effect will also be present in sensorless techniques utilizing signal injection although its influence might be less significant due to the magnitude of the injected signal.
Industrial Electronics, 2008. ISIE 2008. IEEE International Symposium on; 08/2008
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ABSTRACT: In this paper the control of a grid-connected wind energy conversion system (WECS) based on a sensorless vector controlled cage induction machine fed by a matrix converter is presented. The machine is vector controlled using a model reference adaptive system (MRAS) observer to estimate the rotational speed and rotor position. The electrical torque of the induction generator is regulated to drive the WECS to the operating point where the wind turbine aerodynamic efficiency is maximised. Stability issues related to the operation of a WECS connected to the grid using a matrix converter are also discussed in this work. Experimental results, obtained with a 2.5 kW prototype are presented and fully discussed in this paper.
Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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ABSTRACT: This paper addresses the analysis and performance of several model reference adaptive system (MRAS) observers for sensorless vector control of doubly-fed induction machines. Small signal models allow the formal analysis of the observers for a given dynamic. The performance of each MRAS observer is analyzed, considering grid-connected and stand-alone operation. The MRAS observers are implemented in a 3.5 kW experimental prototype composed of a doubly-fed induction generator and a wind turbine emulator. Experimental results validate the predictions of the small signal models and demonstrate the performance of the sensorless methods during both steady state and variable speed wind energy generation.
IEEE Transactions on Power Electronics 06/2008; · 4.65 Impact Factor
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ABSTRACT: This paper considers the formal design for the grid frequency control in an offshore wind farm connected with line-commutated converter high voltage dc (HVDC) link. The control paradigm is based on using the grid frequency control to regulate the HVDC rectifier firing angle or dc-link current and hence control the power flow in the system. The dynamic behaviors of the system are verified by comparing the response from derived transfer functions and PSCAD simulations; hence the grid frequency controllers are designed. The control system performance has been validated by simulations of normal operation and fault regimes. The work provides a good basis for wider research investigation into wind farm operation.
IEEE Transactions on Power Electronics 06/2008; · 4.65 Impact Factor
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ABSTRACT: In this paper, the modeling and control strategy of a wind-diesel generation system are discussed. In the proposed topology, the diesel engine and the wind turbine are both variable-speed machines, allowing maximum fuel efficiency and optimal energy capture from the wind. A vector-controlled doubly fed induction generator is used in each generation system to provide fixed voltage and frequency to the load. The diesel unit balances the system power and changes the speed according to the power demand in order to minimize the fuel consumption. The electrical torque of the wind system generator is regulated to maximize the energy capture of the wind turbine. The advantages of operating a diesel engine at variable speed are discussed. The dynamic and steady-state operation of the wind-diesel system, including voltage and frequency control, active power balancing, and control of the reactive power supplied to the grid/load are analyzed in this paper. Experimental results, from a 3-kW experimental prototype are presented in this paper.
IEEE Transactions on Energy Conversion 04/2008; · 2.27 Impact Factor
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ABSTRACT: The paper considers a solution for integration of large offshore doubly fed induction generator-based wind farms with a common collection bus controlled by a STATCOM into the main onshore grid using line-commutated high-voltage dc connection. A design procedure is described and the controlled system is validated using PSCAD/EMTDC simulations confirming high performance of the proposed control strategy in both normal operation conditions and faults. Engineering issues related to STATCOM capacitor sizing and reduction of STATCOM rating are considered and their effectiveness is confirmed.
IEEE Transactions on Energy Conversion 04/2008; · 2.27 Impact Factor
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ABSTRACT: This paper presents a new sensorless method for the vector control of doubly-fed induction machines (DFIMs) without using speed sensors or rotor position measurements. The proposed sensorless method is based on the model reference adaptive system (MRAS) estimating the rotor position and speed from the machine rotor currents. The method is appropriate for both stand-alone and grid-connected operation of variable speed DFIMs. To design the MRAS observer with the appropriate dynamic response, a small signal model is derived. The sensitivity of the method for variation in the machine parameters is also analyzed. Speed catching on the fly and synchronization of the doubly-fed induction generator with the utility are also addressed. Experimental results obtained from a 3.5-kW prototype are presented and fully analyzed.
IEEE Transactions on Industrial Electronics 02/2008; · 5.16 Impact Factor
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ABSTRACT: This paper first identifies and quantifies the saliency components in symmetric permanent magnet synchronous machines. The saliency component dependence on the geometry and operating regime of the machine will be investigated in an effort to set out guidelines for machine and control design of these type of machines.
Industrial Electronics Society, 2007. IECON 2007. 33rd Annual Conference of the IEEE; 12/2007
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ABSTRACT: This paper addresses the sensorless speed and position control of induction motors using high-frequency injection at zero and low frequencies. A novel algorithm is presented which allows the rejection of saturation and nonlinear inverter effects without the need for an offline precommissioning process. The method is based on a set of synchronous filters to identify the disturbance waveforms and a memory algorithm that refines the quality of the disturbance waveforms as the motor's operational history is increased. The algorithm is entirely sensorless. Experimental results show sensorless low-frequency operation with and without the memory algorithm.
IEEE Transactions on Industrial Electronics 11/2007; · 5.16 Impact Factor
