Commutation Frequency Research Articles

DTC-SVM-based position regulation of an induction motor: a comparison between different strategies

This work is aimed at looking into potential advantages of direct torque control (DTC) strategies for position regulation applications. Of particular interest is the capability exhibited by DTC strategies to develop the maximum torque at standstill. Within this background, the paper is devoted to the presentation of a comparison study between three DTC strategies dedicated to position control of an induction motor, such that: 1) the basic DTC strategy; 2) the DTC strategy with a look-up table including only active voltage vectors; 3) the DTC-SVM strategy with hysteresis controllers and imposed commutation frequency. Following simulation works, it has been found that the third strategy offers the lower torque ripples. Furthermore, it exhibits a high capability to reject the demagnetisation problem which penalises the stator flux regulation at low speeds in the Takahashi basic strategy. However, the DTC-SVM requires a control system with higher CPU frequencies in such a way its implementation scheme is more complex than the basic DTC strategy.

Design and Analysis on the Vibration Piston Seal

Features of the piston reciprocating motion is a high commutation frequency, small displacement, the impact force. Requirements of the piston movement is able to adapt quickly to change. Reducing the resistance movement of the piston will be able to make more flexible movement of the piston .The seal with mating surfaces can reduce the resistance movement . The gap of mating surface of the piston rod formed hydraulic oil spill. Mating surface seal problem is that the oil leakage is larger。Piston movement way of hydraulic vibrator is a kind of variable frequency and variable amplitude, in the form of constant flow. The form of the oil cylinder and the piston movement is the same. The cylinder as the output component of hydraulic vibrator output movement is to reduce the leakage .

Terminal‐voltage‐based starting strategy for brushless DC motors without position sensors

A new starting strategy is presented for brushless DC motors (BLDCMs) without rotor position sensors. This strategy can accelerate the rotor by regulating commutation frequency to be suitable for the supplied voltage according to the waveform of average terminal voltages. Experimental results demonstrate the effectiveness of the strategy.

Exploration on the Dual Spool Design of Rotary Hydraulic Valve

There is also a monomer leak valve body on the single spool, Leakage between the guide groove affected the layout of the form guide groove. Two end faces of the single spool work in the different fluid pressure in the chamber. When the working pressure of the hydraulic system is high, the pressure differential will cause the spool bearings subject to large axial force. It will increase the resistance torque of bearing rotation. Effects of axial force also limits the increase spool diameter. Double spool valve with two spool rotation series manner. Each spool in the same pressure in the working medium. Eliminating the axial force of the valve body due to fluid pressure differential generated, also reduces the resistance to rotation of the spool moment and the impact of guide groove arrangement by oil leak, and also the commutation frequency of the rotary valve can be improved by increasing the diameter of the spool.

Noise and vibration due to rotor eccentricity in a HDD spindle system

This paper numerically and experimentally investigates the characteristics of torque ripple and unbalanced magnetic force (UMF) due to rotor eccentricity and their effects on noise and vibration in a hard disk drive (HDD) spindle motor with 12 poles and 9 slots. The major excitation frequencies of a non-operating HDD spindle system with rotor eccentricity are the least common multiples (LCM) of pole and slot numbers of the cogging torque and the harmonics of slot number ±1 of the UMF. An experimental setup is developed to measure the UMF generated by rotor eccentricity and to verify the simulated UMF. In the operating HDD spindle motor, the harmonics of the commutation frequency of torque ripple (multiplication of pole and phase) are increased by the interaction of the driving current and rotor eccentricity, and they are the same as the LCM of pole and slot numbers for a HDD spindle motor with 12 poles and 9 slots. The major excitation frequencies of the UMF while operating condition are also the harmonics of slot number ±1 and the harmonics of commutation frequency ±1. We verify that the source of the harmonics of slot number ±1 and the harmonics of commutation frequency ±1 in acoustic noise and vibration is rotor eccentricity of the UMF through experiments.

Improved torque regulator to reduce steady‐state error of torque response for direct torque control of permanent magnet synchronous machine drives

This study presents an improved switching-table-based direct torque control method for three-phase permanent magnet synchronous machine drives. The instantaneous variation rates of stator flux and torque of each converter output voltage vector are analysed. It is found that large steady-state error of torque response exists because of the difference in the decreasing and increasing variation rates. A novel and simple on-line band-shifted torque regulator is proposed to reduce this steady-state error of torque response. The experimental results verify that the proposed method can significantly reduce the steady-state error of torque response with the extra bonus of slight reduction of both the torque ripple and average commutation frequency, while preserve the merits of the conventional direct torque control, that is, simple structure, good robustness and excellent transient response.

Optimization Algorithm for Selective Compensation in a Shunt Active Power Filter

This paper proposes an optimization algorithm based on linear matrix inequalities (LMIs) to be implemented in a shunt active power filter (SAPF) enabling it to perform a selective compensation of nonefficient powers when the rated power of the SAPF is limited. The system uses the IEEE Standard 1459 to identify the different power terms (active, reactive, unbalance, and harmonics) demanded by local loads in a three-phase four-wire system. Then, the algorithm solves a quadratically constrained quadratic program by means of an LMI formulation and calculates the optimal reference currents that allow the SAPF to cancel a selection of the previously identified nonefficient power terms. For this selection, the algorithm presents different weighting coefficients in the cost index to be optimized. These coefficients assign a relative importance to each different nonefficient power term, giving priority to some over the others. Moreover, the optimization performed in this work to calculate the reference currents considers that the SAPF presents a power limitation. Finally, the reference currents' tracking has been implemented using a proportional feedforward controller which assures a constant commutation frequency of the SAPF. Experimental results demonstrate the validity of the proposal.

A linear quadratic regulator control of a stand-alone PEM fuel cell power plant

This paper introduces a technique based on linear quadratic regulator (LQR) to control the output voltage at the load point versus load variation from a standalone proton exchange membrane (PEM) fuel cell power plant (FCPP) for a group housing use. The controller modifies the optimal gains ki by minimizing a cost function, and the phase angle of the AC output voltage to control the active and reactive power output from an FCPP to match the terminal load. The control actions are based on feedback signals from the terminal load, output voltage and fuel cell feedback current. The topology chosen for the simulation consists of a 45 kW proton exchange membrane fuel cell (PEMFC), boost type DC/DC converter, a three-phase DC/AC inverter followed by an LC filter. Simulation results show that the proposed control strategy operated at low commutation frequency (2 kHz) offers good performances versus load variations with low total harmonic distortions (THD), which is very useful for high power applications.

Research on Neutral-Point Balancing for Three-Level Space Voltage Vector Converter

A novel hybrid clamped dual-PWM three-level converter topology is proposed for induction motor drives in this paper. The switching states of hybrid clamp three-level converters increase to sixty-four from twenty-seven switching states of diode clamp three-level converters. In order to realize optimization of its redundant voltage space vectors by detecting voltage of clamp capacitor and difference of capacitor voltage in DC side, Generating an optimized switching pattern, The hybrid clamped three-level converter increases the voltage levels number, reducing the harmonics associated to the commutation frequency and limiting the dv/dt by all the switches . It can quickly balance the DC voltage, Realized system of 4-Quardant Running. the control circuit and main circuit was designed with DSP and CPLD, experimentation results proved it is very effective and practicability.

Carrier-Based Randomized Pulse Position Modulation of an Indirect Matrix Converter for Attenuating the Harmonic Peaks

To attenuate the peaks of harmonics, three carrier-based randomized pulse position modulation schemes are proposed for an indirect matrix converter (IMC), which, to date, have not been discussed in existing literatures. In the first scheme, to avoid commutation of a rectifier stage at instants of carrier transition, one of four different pulse positions of the rectifier stage is selected randomly based on the Markov chain. The second scheme randomly places the center of the pulse position with a limited degree of freedom, which has a lower harmonic spectrum but higher commutation frequency. The maximum degree of freedom is achieved in the third scheme, which randomly varies the pulse position by delaying its edge along entire carrier cycle, resulting in a continuous and flat harmonic spectrum, but the maximum commutation frequency in three proposed schemes. An alternative carrier of an inverter stage is applied in all the schemes to maintain smooth operation at instants of carrier transition. Effectiveness of the proposed schemes is validated through experimental tests on an IMC prototype.

Direct Torque Control of Permanent Magnet Synchronous Motor With Reduced Torque Ripple and Commutation Frequency

In conventional direct torque controlled (DTC) permanent magnet synchronous motor drive, there is usually undesired torque and flux ripple. The existing literature have proposed some methods to reduce torque and flux ripple by optimizing the duty ratio of the active vector. However, these methods are usually complicated and parameter dependent. This paper first compares the performances of three duty determination methods in detail and then proposes a very simple but effective method to obtain the duty ratio. The novel method is superior to the existing methods in terms of simplicity and robustness. By appropriately arranging the sequence of the vectors, the commutation frequency is reduced effectively without performance degradation. To further improve the performance of system, a low-pass filter-based voltage model with compensations of amplitude and phase is employed to acquire accurate stator flux estimation. The proposed scheme is able to reduce the torque and flux ripple significantly while maintaining the simplicity and robustness of conventional DTC at the most. Simulations and presented experimental results validate the effectiveness of the proposed schemes in this paper.

Harmonic current cancellation and control of a grid-connected synchronous generator entrained by a wind turbine

Nonlinear devices, such as power electronics converters inject harmonic currents in the AC system and increase overall reactive power demanded by the equivalent load. Also, the number of sensitive loads that require ideal sinusoidal supply voltages for their proper operation has increased. In order to keep power quality under limits proposed by standards, it is necessary to include some sort of compensation. Different types of power quality compensators of higher or lower complexity have been reported. It is now well known that an active filter can easily compensate for harmonic current contents in the load current by inserting negative harmonics into the power network. The aim of this paper is to present the efficiency of the electrical part of a wind generation system with a synchronous generator. In attempt to minimize the commutation frequency harmonics in the current and voltage in the stator and to avoid the overlap phenomenon in the diode bridge, an LC filter is inserted between the excited circuit and the DC-DC converter. Simulation results are curried out to validate the proposed solution.

Who are Bicyclists? Why and how much are they Bicycling?

The factors influencing the decision to bicycle are explored and unraveled to inform the development of appropriate and effective strategies to increase bicycling and promote the health of individuals and of the environment. The data used in the analysis were drawn from a survey of Texas bicyclists, and the study includes a comprehensive explanatory analysis of bicyclists and their bicycling habits. Various econometric models are used to evaluate the determinants of bicyclists’ perception for safety and quality issues and the frequency of bicycling for commute and noncommute purposes. The results of the study indicate that the perceptions of the quality of bicycle facilities and safety from traffic crashes show significant variation depending on bicyclists’ demographic and work characteristics and bicycle amenities and facilities on the commute route and at the workplace. Bicyclist demographics (gender, age, education level, commute distance), household demographics (number of automobiles, number of bicycles, number of children), residential location and season, bicycle amenities at work (bicycle racks, showers), bicyclist perceptions of the overall quality of bicycle facilities, and bicycle-use characteristics affect commute and noncommute bicycling frequency. These study results can assist in the development of informed policies to increase commute and noncommute bicycling, and the results highlight the ongoing need for detailed surveys to understand bicycling behavior.

Microflow injection system based on a multicommutation technique for nitrite determination in wastewaters

In this work a microflow structure, suitable for micro-FIA (micro flow injection analysis), will be described, evaluated and applied to real samples. Microchannels, the detector flow cell and input/output ports have been micromachined in silicon and sealed with anodically bonded Pyrex glass. The channels are defined by etching approximately 200 microm depth in silicon using a dry reactive ion etching (RIE) process. Optical windows integrated in the chip structure allow simple absorbance/transmission measurements to be made. The optical measurements were made using an LED as emitter (lambda=525 nm) and a photodiode as a detector. A Visual-Basic program has been developed to control an automatic burette, three-way solenoid valves and the data acquisition system. The micro-FIA for nitrite determination using the Griess-Ilosvay reaction has been implemented for the on-line monitoring of wastewater treatment plants (WWTPs). The multicommutation concept has been applied in order to enhance the mixing process inside the microsystem. Tandem streams of reagent and sample were generated and evaluated at different commutation frequencies. Two optimal frequencies, 400/200 ms and 150/450 ms, were found to be the most suitable ones. The first commutation ratio gave rise to wide linear working range (0-250 ppm), in spite of a high detection limit (0.35 ppm) and a low sensitivity (0.0041+/-0.0004 AU ppm-1). With the second ratio, the working linear range was smaller (0-50 ppm) but the detection limit (0.17 ppm) and the sensitivity (0.0091+/-0.0003 AU ppm-1) improved remarkably. Finally, real samples with a high nitrite concentration (0-1500 ppm) coming from a study of kinetic inhibition in the nitrification process at a WWTP has been analysed with the proposed micro-FIA system. The obtained results have allowed the corroboration of the model of inhibition by the nitrite ion with great exactitude.

On the reduction of the commutation frequency in DTC: a comparative study

AbstractThe paper deals with a comparison between three DTC strategies: (i) the original one introduced by Takahashi which is based on an empirical approach, (ii) a strategy based on an analytical approach which takes into account the torque dynamic considering four quadrant operation, and (iii) an extension of the second approach considering twelve ‘active’ voltage space vectors. It has been found that a reduction of the commutation frequency has been gained going from the first strategy to the third one. This opens up crucial efficiency benefits, as far as the commutation losses in the inverter are considerably reduced. Copyright © 2005 John Wiley & Sons, Ltd.

Two-dimensional simulation of the transient electrothermal effects during the gate turn-off thyristor turn-off

The electrothermal behavior of a 1200V-30A gate turn-off (GTO) thyristor operating in its electrical circuit has been studied using two-dimensional (2D) simulation tools. The program realized for this purpose uses a combination of Silvaco tools and takes into account the thermal environment of the GTO. It was validated by direct experimental measurements. The studied GTO is a silicon device with a symmetrical doping profile (N+PN−P+). It operates in a dc-dc converter at a 400 Hz commutation frequency, its conduction time is in the range of 0.05–0.25 ms. The thermal environment of the device is reproduced by including its thermal parameters and those of its package in the calculation, the simulation accounts, then, for all the thermal generation and conduction in the device. The simulation program was validated by comparing the electrical parameters (anode and gate currents, anode–cathode voltage, and dissipated power) of the GTO, obtained in the same operating conditions, by both simulation and direct measurements. The transient behavior of the GTO during its turn-off at a nanosecond scale was then obtained. We first obtained the 2D time-dependent distribution of most of the internal electrical parameters (carriers, current density, …); then we obtained the 2-D time-dependent distribution of temperature inside the GTO.

Proposal of a new method for controlling the torque and the flux of a voltage source inverter‐fed induction motor

AbstractIn this paper, a method for controlling the torque and the flux of an induction motor is presented. It consists in calculating, within each time‐step, appropriate values of the voltage to be impressed across the phase windings. The method takes into account the effects of the magnetic saturation, as well as those of the variations of the rotor and stator resistances versus the temperature. It does not require any integrators for evaluating the stator‐flux and works under controlled commutation frequencies.

High-performance direct-frequency converters controlled by predictive-current loop

Two predictive space-vector control strategies for direct-frequency converter (DFC) structures are presented. Both algorithms require output-current feedback in order to decide the next best state of the power converter. The performance of the control techniques is compared with a high-performance fictitious-link DFC. Computer simulation using Microsim PSpice 5.3 is used to examine the operation of the DFC converter algorithms. The evaluation is performed for a wide-operational output frequency and includes input/output-voltage ratio, commutation frequency, input-current balance, input-current total harmonic distortion (THD) and input power factor. From these results, the high performance exhibited by the proposed algorithms is verified.

Comparability and Transferability of Commuter Behavior Characteristics Between Cities: Departure Time and Route-Switching Decisions

Extensive diary surveys of commuter behavior were conducted in Dallas and Austin. These surveys provide data to characterize the day-today dynamics of commuter decisions, including departure time and route, for both morning and evening commutes. The data were used to develop user decision models that relate route and departure time switching patterns to socioeconomic characteristics, workplace conditions, and traffic system characteristics. Comparisons were made to assess the extent of transferability of behavioral findings and model parameters. Remarkable similarity was found in the general commuting behavior patterns observed in the two cities, such as greater switching activity in the evening than in the morning commute and greater frequency of departure time switching relative to route changes. Differences between the two cities appear to be primarily due to the larger size of Dallas.

Comparability and Transferability of Commuter Behavior Characteristics between Cities: Departure Time and Route-Switching Decisions

Extensive diary surveys of commuter behavior were conducted in Dallas and Austin. These surveys provide data to characterize the day-today dynamics of commuter decisions, including departure time and route, for both morning and evening commutes. The data were used to develop user decision models that relate route and departure time switching patterns to socioeconomic characteristics, workplace conditions, and traffic system characteristics. Comparisons were made to assess the extent of transferability of behavioral findings and model parameters. Remarkable similarity was found in the general commuting behavior patterns observed in the two cities, such as greater switching activity in the evening than in the morning commute and greater frequency of departure time switching relative to route changes. Differences between the two cities appear to be primarily due to the larger size of Dallas.