Showing papers on "Stationary Reference Frame published in 2010"

Dead Time Compensation Method for Voltage-Fed PWM Inverter

Abstract: A new dead time compensation method for a pulsewidth modulation (PWM) inverter is proposed. In the PWM inverter, voltage distortion due to the dead time effects produces fifth and seventh harmonics in the phase currents of the stationary reference frame, and a sixth harmonic in the d- and q-axis currents of the synchronous reference frame, respectively. In this paper, the sixth harmonic of the integrator output of the synchronous d-axis proportional-integral (PI) current regulator is used to compensate the output voltage distortion due to the dead time effects, since the integrator output has ripple corresponding to six times the stator fundamental frequency. The proposed method can be easily implemented by feedforwardly adding compensation voltages to the output reference voltage of the synchronous PI current regulator. The proposed method, therefore, has some significant advantages such as simple implementation without additional hardware, easy mathematical computation, no offline experimental measurements, and application in both the steady state and the transient state. The validity of the proposed compensation algorithm is shown through several experiments.

Optimization of Delayed-State Kalman-Filter-Based Algorithm via Differential Evolution for Sensorless Control of Induction Motors

Abstract: This paper proposes the employment of the differential evolution (DE) to offline optimize the covariance matrices of a new reduced delayed-state Kalman-filter (DSKF)-based algorithm which estimates the stator-flux linkage components, in the stationary reference frame, to realize sensorless control of induction motors (IMs). The DSKF-based algorithm uses the derivatives of the stator-flux components as mathematical model and the stator-voltage equations as observation model so that only a vector of four variables has to be offline optimized. Numerical results, carried out using a low-speed training test, show that the proposed DE-based approach is very promising and clearly outperforms a classical local search and three popular metaheuristics in terms of quality of the final solution for the problem considered in this paper. A novel simple stator-flux-oriented sliding mode (SFO-SM) control scheme is online used in conjunction with the optimized DSKF-based algorithm to improve the robustness of the sensorless IM drive at low speed. The SFO-SM control scheme has closed loops of torque and stator-flux linkage without proportional-plus-integral controllers so that a minimum number of gains has to be tuned.

Adaptive Nonlinear Direct Torque Control of Sensorless IM Drives With Efficiency Optimization

Abstract: Efficiency optimization of induction motor (IM) drives is a major subject based on these drives' extensive use in the industry. Among the different proposed methods, a model-based approach (MBA) seems to be the fast one. However, this method needs the motor parameters that must be correctly identified. On the other hand, a search-based approach (SBA) is a parameter-independent method but needs a greater convergence time. In this paper, a novel model-based loss-minimization approach is presented, which is combined with a backstepping direct torque control of the IM drive. An improved search-based method for efficiency optimization is also introduced. The proposed controller is realized in the stationary reference frame and has a fast-tracking capability of rotor flux and electromagnetic torque. Moreover, a sliding-mode rotor-flux observer is introduced, which is employed for simultaneous determination of rotor-flux space vector, rotor speed, and rotor time constant. The proposed control idea is experimentally implemented in real time using a field-programmable gate-array board synchronized with a personal computer. Simulation and experimental results are finally presented to verify the effectiveness of the method proposed.

New Stationary Frame Control Scheme for Three-Phase PWM Rectifiers Under Unbalanced Voltage Dips Conditions

Abstract: A new stationary frame control scheme for three-phase pulsewidth-modulation (PWM) rectifiers operating under unbalanced voltage dips conditions is proposed in this paper The proposed control scheme regulates the instantaneous active power at the converter poles to minimize the harmonics of the input currents and the output voltage ripple This paper's novelty is the development of a new current-reference generator implemented directly in stationary reference frame This allows using proportional sinusoidal signal integrator (P-SSI) controllers for simultaneous compensation of both positive and negative current sequence components No phase-locked loop (PLL) strategies and coordinate transformations are needed for the proposed current-reference generator Experimental results are presented for a 20-kV A alternative current (ac)/direct current (dc) converter prototype to demonstrate the effectiveness of the proposed control scheme A comparison with two other existing control techniques is also performed Fast dynamic performance with small dc-link voltage ripple and input sinusoidal currents are obtained with this control scheme, even under severe voltage dips operating conditions

Evaluation of current controller performance and stability for voltage source converters connected to a weak grid

Abstract: This paper investigates the operation of a current controlled Voltage Source Converter (VSC) under weak grid conditions caused by large grid impedance. Three different current controller structures are investigated; the conventional decoupled PI-controller in the synchronously rotating reference frame, Proportional Resonant (PR) controllers in the stationary reference frame, and the phase current hysteresis controllers. The different control strategies are studied by simulation, and the results show how large grid impedances can influence the dynamic response of the system. It is further discussed how the interaction between the current controllers, the Phase Locked Loop (PLL) and the grid inductance can trigger instability when the voltage measurements are highly influenced by the operation of the converter. The results indicate that the tuning of the PLL and the way of utilizing the phase information is of large importance for the stability and dynamic response of the control system.

A Proportional ${\bm +}$ Multiresonant Controller for Three-Phase Four-Wire High-Frequency Link Inverter

Abstract: A new solution for unbalanced and nonlinear loads in terms of power circuit topology and controller structure is proposed in this paper. A three-phase four-wire high-frequency ac-link inverter is adopted to cater to such loads. Use of high-frequency transformer results in compact and light-weight systems. The fourth wire is taken out from the midpoint of the isolation transformer in order to avoid the necessity of an extra leg. This makes the converter suitable for unbalanced loads and eliminates the requirements of bulky capacitor in half-bridge inverter. The closed-loop control is carried out in stationary reference frame using proportional + multiresonant controller (three separate resonant controller for fundamental, fifth and seventh harmonic components). The limitations on improving steady-state response of harmonic resonance controllers is investigated and mitigated using a lead-lag compensator. The proposed voltage controller is used along with an inner current loop to ensure excellent performance of the power converter. Simulation studies and experimental results with 1 kVA prototype under nonlinear and unbalanced loading conditions validate the proposed scheme.

Model predictive direct current control

Abstract: This paper presents a model predictive current controller and its application to ac electrical drives. In a stationary reference frame, the proposed control scheme keeps the α and β currents within given hysteresis bounds while minimizing the switching frequency of the inverter. Based on a internal model of the drive, the controller predicts the drive's future behavior for each switching sequence, extrapolates the output trajectories and selects the inverter switch position (voltage vector) that minimizes the switching frequency and keeps the predicted current trajectories within the hysteresis bounds. The scheme is applicable to a large class of (three-phase) ac electrical machines driven by inverters and it is also effective under all operating conditions, including transients and zero stator frequency operation. Specifically, the very fast transient response time of the classic hysteresis control scheme is inherited.

Reference Current Computation for Active Power Filters by Running DFT Techniques

Abstract: This paper analyzes the feasibility and convenience of applying the efficient discrete Fourier transform (DFT) techniques for the computation of reference currents in active power filters. Existing methods designed for this purpose rely on a high-pass filter in order to obtain the harmonic components of the load current to be filtered. Among these methods, the stationary reference frame (SRF) method reveals itself as the most accurate one because of its inherent immunity to distorted voltage conditions. In this paper, two different implementations of the running DFT, including their recursive and nonrecursive versions, are compared to the SRF approach in terms of steady-state performance, adequacy of transient response, and computational effort. In addition to simulation results, an experimental setup is designed to prove the advantages of resorting to the DFT. Conceptual similarities between both schemes are also stressed in this paper.

Synchronous reference frame based controllers applied to shunt active power filters in three-phase four-wire systems

Abstract: This work presents compensation algorithm schemes used for shunt active power filters applied to three-phase four-wire systems, allowing harmonic current suppression and reactive power compensation, which results in an effective power factor correction. The strategies used to extract the three-phase reference currents are based on the synchronous reference frame method. Although this method is based on balanced three-phase loads, it can also be used for single-phase loads, allowing independent control of all three phases. Accordingly, a fictitious quadrature current needs to be generated through software implementation, and be orthogonal to the measured load current. This creates the fictitious balanced currents in the two-phase stationary reference frame system, allowing the choice of an adequate compensation strategy which will result in either balanced or unbalanced sinusoidal source currents. Three shunt APF topologies are evaluated under unbalanced load conditions: Split-Capacitor (S-C), Four-Leg (F-L) and Three Full-Bridge (3F-B). The proposed algorithms applied to the three APF topologies are evaluated and discussed. Mathematical analyses of the SRF-based algorithms are presented and simulation results are performed to validate the theoretical development and confirm the performance of the shunt APFs.

Enhanced Proportional-Resonant Current Controller for Unbalanced Stand-alone DFIG-based Wind Turbines

Abstract: An enhanced control strategy for variable-speed unbalanced stand-alone doubly-fed induction generator-based wind energy conversion systems is proposed in this paper. The control scheme is applied to the rotor-side converter to eliminate stator voltage imbalance. The proposed current controller is developed based on the proportional-resonant regulator, which is implemented in the stator stationary reference frame. The resonant controller is tuned at the stator synchronous frequency to achieve zero steady-state errors in rotor currents without decomposing the positive and negative sequence components. The computational complexity of the proposed control algorithm is greatly simplified, and control performance is significantly improved. Finally, simulations and experimental results are presented to verify the feasibility and the robustness of the proposed control scheme.

Rotating machinery condition monitoring using position sensor

Abstract: Continuous monitoring and fault diagnosis of rotating machinery during variable speed operation is performed using only a position feedback signal. The position sensor generates a periodic waveform having multiple pulses per revolution of the machine. A circuit is included to detect, for example, a zero crossing or edge of the periodic waveform. At each detected zero crossing or edge, the time and position of the event is stored in memory. Other data, such as the current in the motor, may also be sampled and stored in memory. Because the sampled data is triggered by repeated feature of the position feedback signal, the sampled data is in a stationary reference frame in the position domain. Frequency analysis is performed on the sampled data, and the frequency components present in either the sampled signal are analyzed to identify the presence of a fault in the rotating machinery.

Cascaded EMF and speed sliding mode observer for the nonsalient PMSM

Abstract: The paper presents an EMF and speed estimator for the nonsalient permanent magnet synchronous motor (PMSM). The method uses two cascaded sliding mode (SM) observers and is realized using only the measured voltages and currents of the motor. A first SM observer estimates the EMFs of the machine in the stationary reference frame. These EMFs are passed as inputs to a second SM observer that estimates the motor speed and re-estimates the EMFs. The method is applicable in a sensorless PMSM speed control scheme where the estimated EMFs are used to obtain the rotor position and the estimated speed is used for speed feedback. The paper verifies the existence conditions of the sliding mode motion and proves the convergence of the observers. The theoretical findings are validated with simulation results that show that the estimated EMFs and speed are of good quality. The advantages of the proposed method compared to the state of the art are discussed.

Transient performance of a three-phase self-excited induction generator supplying single phase load with Electronic Load Controller

Abstract: This paper presents the transient analysis of a three-phase self-excited induction generator (SEIG) feeding single-phase inductive load with an Electronic Load Controller (ELC) used in stand-alone micro-hydro power generation employing uncontrolled turbines. A complete mathematical model of the total system has been developed. The dynamic model of the SEIG using a three-phase star-connected induction machine is developed based on stationary reference frame d-q axes theory, with three capacitors connected in series and parallel with the single-phase load. The effect of cross-saturation is also incorporated in the model. The implemented ELC consists of a rectifier-chopper system feeding a resistive dump load whose power consumption is varied through the duty cycle of the chopper. Simulated results are compared with the experimental ones, obtained on a developed prototype of an SEIG-ELC system for the different transient conditions such as sudden application of load, sudden removal of load to validate the effectiveness of the proposed approach.

Integral sliding-mode flux observer for sensorless vector-controlled induction motors

Abstract: The control performance of sensorless vector-controlled induction motors mainly relies on an accurate flux estimation. However, due to the variations of electrical parameters, the inaccuracy of estimated fluxes will cause the performance degradation of speed control. In this paper, an integral sliding-mode flux observer is provided to estimate the d-and q-axis fluxes in the stationary reference frame. To certify the closed-loop stability, the stability analysis based on the Lyapunov theory is also presented. In addition to simulations, a DSP/FPGA based experimental platform is setup to evaluate the feasibility of proposed control scheme. Simulations and experimental results illustrate that the responses of flux and speed can be performed as desire by utilizing the integral sliding-mode flux observer in a wide speed range.

Reduction of Current Ripples due to Current Measurement Errors in a Doubly Fed Induction Generator

Abstract: This paper proposes a new compensation algorithm for the current measurement errors in a DFIG (Doubly Fed Induction Generator) Generally, current measurement path with current sensors and analog devices has non-ideal factors like offset and scaling errors As a result, the dq-axis currents of the synchronous reference frame have one and two times ripple components of the slip frequency In this paper, the main concept of the proposed algorithm is implemented by integrating the 3-phase rotor currents into the stationary reference frame to compensate for the measured current ripples in a DFIG The proposed algorithm has several beneficial features: easy implementation, less computation time, and robustness with regard to variations in the electrical parameters The effectiveness of the proposed algorithm is verified by several experiments

Model Following Sliding-Mode Control of a Six-Phase Induction Motor Drive

Abstract: In this paper an effective direct torque control (DTC) and stator flux control is developed for a quasi six-phase induction motor (QIM) drive with sinusoidally distributed windings Combining sliding-mode (SM) control and adaptive input-output feedback linearization, a nonlinear controller is designed in the stationary reference frame, which is capable of tracking control of the stator flux and torque independently The motor controllers are designed in order to track a desired second order linear reference model in spite of motor resistances mismatching The effectiveness and capability of the proposed method is shown by practical results obtained for a QIM supplied from a voltage source inverter (VSI)

Sliding mode current control of grid-connected voltage source converter

Abstract: This paper presents a new sliding mode current control (SMCC) of three-phase grid-connected voltage source converters (VSCs). The proposed SMCC strategy employs a nonlinear sliding mode control scheme to directly calculate the required converter control voltage so as to eliminate the line current errors in the stationary reference frame without involving any synchronous coordinate transformation. Constant converter switching frequency is achieved by using space vector modulation (SVM) which eases the design of the ac harmonic filter. Simulation results on a 3kVA grid-connected VSC system are provided to validate the feasibility of the proposed SMCC strategy during normal and faulted grid voltage conditions.

Super-twisting control of induction motors with core loss

Abstract: A novel nonlinear affine model for the induction motor with core loss is developed in the well known (α β) stationary reference frame. The core is represented with a resistance in paralled with the magnetization inductance. Then, an optimal rotor flux modulus is calculated such that, the power loss due to stator, rotor and core resistances is minimized, and as a consequence the motor efficiency is raised. The calculated optimal flux modulus is forced to be tracked by the induction motor along with a desired rotor velocity by means of a super-twisting sliding mode controller. Using a novel Lyapunov function, the closed-loop stability of the system is demonstrated. A simulation study is carried on, where the superior performance of the proposed controller is put in evidence when compared to the same controller when not taking into account an optimal flux modulus.

Compensation of Unbalanced Non Linear Load and neutral currents using stationary Reference Frame in Shunt Active Filters

Abstract: Inasmuch as there are many single phase unbalanced linear and non linear loads in distribution system, current flows through null wire. Because of voltage drops of null wire, load voltage will be unbalance. Different methods have been presented for compensation of load current compensation, which shunt active filter is one of them. Shunt active filter is effective on source current, and it can compensate reactive and non sinusoidal currents. If voltage is unbalanced because of unbalanced current, shunt active filter can compensate harmonics, zero and negative sequences of current and the result of compensation is balanced voltage. Is network cause of voltage unbalancing, shunt active filter won't efficient. This paper has presented a Compensation of Unbalanced Non Linear Load Currents and Null Current by Use of Stationary Reference Frame in Shunt Active Filter in order to compensation of harmonics, zero and negative sequences of current. Not only presented control method can compensate harmonic and unbalanced currents, but also it can compensate reactive current, and power factor will be near to unity. To confirm it, shunt active filter has been simulated by PSIM, and the resultants demonstrate efficiency of presented method on compensation of non linear load current, null current and power factor improvement.

Neural based MRAS sensorless techniques for high performance linear induction motor drives

Abstract: This paper proposes a neural based MRAS (Model reference Adaptive System) speed observer suited for linear induction motors (LIM). Starting from the dynamical equation of the LIM in the synchronous reference frame in literature, the so-called voltage and current models of the LIM in the stationary reference frame, taking into consideration the end effects, have been deduced. Then, while the inductor equations have been used as reference model of the MRAS observer, the induced part equations have been discretized and rearranged so to be represented by a linear neural network (ADALINE). On this basis, the so called TLS EXIN neuron has been used to compute on-line, in recursive form, the machine linear speed. As machine under test, a complete dynamic model, based on the constructive elements of the LIM and taking into consideration the end effects by the definition of a proper air-gap function, has been adopted. The proposed MRAS observer has been tested in numerical simulation at high and low linear speeds of the inductor and has been further compared with both the classic MRAS observer taking into consideration the LIM's end effects and with the MRAS observer based on the RIM's equations, not considering the end effects.

Control of Power Electronic Converters in Distributed Power Generation Systems: Evaluation of Current Control Structures for Voltage Source Converters operating under Weak Grid Conditions

Abstract: The performance of different current controller structures for Voltage Source Converters (VSC) under weak grid conditions caused by large grid impedance is investigated. The VSC is synchronized to the grid by a Phase Locked Loop (PLL). Current control techniques and PLL techniques for handling both symmetrical and asymmetrical conditions are presented and discussed. The investigated current control structures are; the conventional Proportional Integral (PI)-controller in the synchronous rotating reference frame, dual PI-controllers implemented in positive- and negative-sequence rotating reference frame, the Proportional Resonant (PR)-controller in the stationary reference frame, the phase current hysteresis controller, and a space vector base hysteresis controller in the synchronous rotating reference frame. The PLL-techniques used for synchronization are; a conventional synchronous rotating reference frame PLL, a PLL with notch filter, and a Decoupled Double Synchronous Reference frame PLL (DDSRF-PLL). The different current control strategies and PLL-techniques are studied by simulations. The results show how large grid impedance can influence the dynamic response of the system and how the interaction between the PLLs, the current controllers and the large grid inductance can even trigger instability when the voltage measurements are highly influenced by the operation of the converter. The PI-controllers in the synchronous rotating reference frames are particularly sensitive to oscillations that can be reinforced when the measured voltage feed-forward terms are used in the control system. The response of the PR-controller is instead slowed down by the interaction with the PLL, while both the hysteresis controllers are quickly tracking the reference value as long as the interaction with the PLL is not leading to instability. Operation under asymmetrical weak grid conditions are investigated for current controllers that exploit PLL techniques designed to remove the oscillations that occur in the positive sequence reference frame voltage during unbalanced grid voltage. The simulations show that the DDSRF-PLL has a shorter transient period than the PLL with notch filter, but with a small steady state 100 Hz oscillation under the weak asymmetrical grid conditions. The results indicate that the tuning of the PLL is of large importance for the stability of the control system, and that a slower PLL can lead to less interaction with the current controllers at the cost of a slower and less accurate dynamic overall control performance.

Full order EMF observer for PMSM — design, analysis and performance under improper speed signal

Abstract: The paper focuses on the problem of rotor position estimation for the nonsalient permanent magnet synchronous motor (PMSM) that is used as a generator in a windmill system. The paper presents the design and analysis of a Full Order EMF observer that is based on the PMSM model in the stationary reference frame. The inputs in the observer are the motor voltages and currents (which are measured) and the motor speed. The convergence of the observer is first analyzed assuming that the speed signal is available — it is shown how to design the feedback gains such that the observer is asymptotically stable. Second, the observer is analyzed under the assumption that the speed signal used is different from the real speed. This corresponds to the situation when a speed estimate would be used (instead of the real speed) in an attempt to obtain a sensorless observer. The PMSM is treated as a linear, time-varying system and the observer presented is analyzed using Lyapunov's stability theory. It is shown that, under correct speed, the observer converges. Under improper speed signal, the estimates have errors and the design gains do not influence these errors and cannot eliminate them. However, since the errors are relatively small, the method could be used in a sensorless drive if the estimated rotor position is corrected with a correction block. The theoretical findings are validated by simulations.

The optimized strategy for input current harmonic of low switching frequency PWM rectifier

Abstract: The industry application of High-power medium-voltage drives converter is an appealing spot in Power electronics technology in recent years. This paper presents an optimized control strategy for input current harmonic of rectifier of three-level NPC back-to-back converter under low switching frequency conditions. A modified P-N SVPWM method includes asymmetrical regular sampling, even-order harmonic elimination and natural DC bus balancing is applied for optimize the THD performance of input currents. And a modified proportional sinusoidal signal integrator method based on control scheme in two phase stationary reference frame which is different from ordinary direct-quadrature (DQ) rotating reference frame is proposed. It provides a specific input current harmonic elimination performance especially considerable in low switching frequency circumstance. Simulation and experimental results based on a rectifier of a 75kVA three-level NPC back-to-back converter prototype with a 400Hz device switching frequency constraint show satisfactory performance.

Rotor position estimation of PMSM by Sliding Mode EMF observer under improper speed

Abstract: The paper discusses the problem of rotor position estimation for the nonsalient permanent magnet synchronous motor (PMSM) and presents a Sliding Mode (SM) EMF observer that is based on the machine's model in the stationary reference frame. The speed of the PMSM which is an input of the proposed sliding mode observer is obtained from a speed estimator. The paper assumes that the speed estimate is different from the real speed and shows that the gains of the SM observer can be designed such that the EMF estimates produced by the SM observer tend to the real EMFs. The observer is designed and analyzed in the framework of nonlinear control using Lyapunov's theory and is validated using simulations. The method proposed is relatively simple and can be used to estimate the rotor position of the PMSM in a sensorless drive.

An active shunt compensator for reactive, unbalanced and harmonic loads under balanced and unbalanced grid voltage conditions

Abstract: This paper focuses on an active shunt compensator suitable for reactive, unbalanced and harmonic loads under both balanced and unbalanced operating conditions of the grid. A stationary reference frame based controller with multiple resonant peaks (proportional + multiresonant controller) is used in order to achieve high accuracy of current compensation. However, the performance of the system depends to a great extent on the PLL structure or unit vector generation process. Under unbalanced grid voltage condition, SRF PLL becomes inefficient because of the presence of double the fundamental frequency components in D- and Q- axis voltages. A similar situation is true for the DC bus voltage as it supplies the oscillatory power during unbalanced compensation. This phenomena results in degradation of the grid current power quality. A resonant filter is adopted in the PLL and DC voltage loop to mitigate the problems. The simulation and experimental results are presented to verify the effectiveness of the scheme.

A nonlinear full order observer for rotor flux position estimation of induction motors

Abstract: The paper discusses the problem of rotor flux position estimation for the induction motor (IM) drive and presents a full-order nonlinear observer that is developed based on the motor's stationary reference frame model. In the method, the IM speed is treated as a slowly time varying parameter and nonlinear control methods are used to design the observer. In the initial development, the speed of the IM is assumed as known and the paper shows how to design the gains of the observer for convergence — some of the resulting gains are time varying. Later, the speed signal is replaced by a speed estimate in an attempt to obtain a speed sensorless observer. The resulting observer is analyzed and it is shown that, despite the lack of asymptotic stability, it allows to estimate the rotor flux position of the IM drive with good accuracy. The theoretical developments are validated with simulations and experimental tests.

Torque ripple reduction in direct torque control based induction motor drive using novel optimal controller design technique

Abstract: In the present work a novel strategy for optimum design of flux and torque controller for carrier space vector pulse width modulation based direct torque control (CSVPWM DTC) of induction motor (IM) drive has been implemented. Two positive and one negative torque slope levels per half the switching period has been predicted for CSVPWM DTC IM drive based on which a new optimal control strategy is proposed for the design of flux and torque controllers where, a P controller is used in the flux loop and a PI controller is used in the torque loop. Performance investigation shows that optimally tuned controllers used in CSVPWM DTC technique are helpful in reducing torque ripple. In proposed control strategy flux and torque slopes are derived using d-q axis induction motor model in stationary reference frame. These slope parameters are respectively utilized to find the transfer function (TF) of flux and torque loops. Using these TF, flux P and torque PI controller settings are obtained such that they give the best results in terms of reduced torque ripple for any flux and torque slopes. In order to show the superiority of the proposed control strategy for CSVPWM DTC IM drive over conventional DTC technique, comparison of simulation and hardware results are presented.

Performance improvement of an induction motor drive using feedback linearization and fuzzy torque compensator

Abstract: This paper presents the dynamic modeling and simulation of a feedback linearization scheme for high performance induction motor control which decouples the rotor flux and the rotor speed (torque) control loop In this scheme the controller takes rotor flux from the feedback path and uses it for the cancellation of nonlinearity present in the rotor flux and the rotor speed control signal As direct flux measurement is proved not to be suitable due to the need of sensor and the sensor in itself sensitive to temperature The scheme uses a flux estimator Furthermore the process is implemented on the stationary reference frame This offers less complex method than the Vector Control Scheme where the requirement for the precise knowledge of the instantaneous position of space flux and the transformation of a synchronous coordinates system into a structure of stationary reference frame and vice-versa makes the system more complex Like vector control it uses PI controller for speed and flux To confront the problem of uncertainties fuzzy controller is used The control scheme is simulated in MATLAB environment Simulation result demonstrates good performance and makes it fair competitive to the other high performance schemes of Induction motor

Control algorithms for a multistage VSI-fed poly-phase PMSM electric drive with non-sinusoidal back-EMF

Abstract: The paper discusses control algorithms for a multistage VSI-fed polyphase PMSM drive with nonsinusoidal back-EMF. FOC principle-related regulation of the motor currents and regulation of individual VSI currents described in both rotor-oriented and stationary reference frames are considered. Computer model-based evaluations of the current and torque spectrum have shown that regulation of the drive variables in a VSI stationary reference frame results in the most efficient suppression of current high-order harmonics and reduction of torque ripples.