Commutation Method Research Articles

A High-Frequency Link Single-Stage PWM Inverter With Common-Mode Voltage Suppression and Source-Based Commutation of Leakage Energy

This paper presents a single-stage bidirectional high-frequency transformer (HFT) link dc/ac converter topology for a three-phase adjustable magnitude and frequency PWM ac drive. This type of converters find a wide range of applications including UPS systems, drives involving renewable energy sources (Solar, Fuel cell), and energy storage systems (typically low voltage dc to high voltage PWM ac). The HFT results in reduction in cost and weight along with a considerable increase in power density. The adverse effects of common-mode voltage are well known in this kind of applications. The proposed topology along with a modulation technique reduces common-mode voltage to practically zero and generates high-quality output voltage waveform comparable to conventional space vector PWM (CSVPWM). A source-based commutation method, presented in this paper, to commute the energy stored in the leakage inductance of the HFT resulting in the following advantages 1) no need for any auxiliary circuits with passive components; 2) almost complete recovery of the leakage energy; 3) soft switching of the output side converter for all load conditions; and 4) minimization of common-mode voltage switching due to commutation. The converter along with the suggested control has been analyzed in detail. The presented simulation and experimental results confirm the operation of the proposed converter.

Design methodology and self-turning velocity control for high-speed slim sensorless brushless direct current motors with self-lubricated bearings

This study presents the motor design methodology and adaptive fuzzy self-tuning proportional–integral–derivative (PID) velocity closed-loop control of slim sensorless brushless direct current (BLDC) motors with self-lubricated bearings that operate at a high speed of 14,000rpm. Moreover, the novel sensorless commutation method includes a mask-based phase shift detector to detect precise optimal commutation points. A prototype of the slim sensorless radial-flux BLDC motor with a self-lubricated bearing for use in the blowers of vacuum cleaners was manufactured and the motor design methodology was verified. The damping interaction caused by the self-lubricating hydrodynamic bearings, shafts, and blades of blowers was also considered, together with a multi-physics analysis. The velocity control experiment used a adaptive fuzzy self-tuning PID control algorithm that has been proven to improve the dynamic performance of the slim sensorless BLDC motors in the blowers of vacuum cleaners. The settling time converged within 1s, that is, the vacuum cleaners rapidly switched to different speeds, and the control approach exhibited robustness and precision in a steady state.

Operational Benefits in Large Synchronous Machine with the Application of Static Drives

In a power plant, synchronous machine work as an alternator after coupling with a prime mover (turbine). Machine discussed in this paper is a special alternator of 1500MVA rating used to supply power in a short circuit test laboratory. This alternator was initially driven by a prime mover. It is well known that a single synchronous machine can work at a time either as a motor or as a generator. With this concept, the prime mover of the said alternator was removed to make it in dual mode operation. This is achieved with the help of three static devices; they are static frequency converter (SFC), static excitation system (SES) and power electronic controllers. This paper begins with the detailed description of SFC and SES. Thereafter it looks into the starting techniques in pulse link mode and synchronous mode. Commutation methods for thyristors under different bridges are also listed out. It has also been explained about running this large machine as motor and converting it to generator for extracting power required for electrical tests. Various modes of operation (e.g. starting, running & stopping) and their inter changeability are also mentioned herewith. Savings in energy is the major outcome of the dual mode operation of this large machine. The energy saving techniques adopted on this machine is also part of this paper.

Spectral theory of the [formula omitted]-symmetric tridiagonal matrices related to Stahl’s counterexample

We recast Stahl’s counterexample from the point of view of the spectral theory of the underlying non-symmetric Jacobi matrices. In particular, it is shown that these matrices are self-adjoint and non-negative in a Krein space and have empty resolvent sets. In fact, the technique of Darboux transformations (aka commutation methods) on spectra which is used in the present paper allows us to treat the class of all G-non-negative tridiagonal matrices. We also establish a correspondence between this class of matrices and the class of signed measures with one sign change. Finally, it is proved that the absence of the spurious pole at infinity for Padé approximants is equivalent to the definitizability of the corresponding tridiagonal matrix.

Commutator methods for the spectral analysis of uniquely ergodic dynamical systems

AbstractWe present a method, based on commutator methods, for the spectral analysis of uniquely ergodic dynamical systems. When applicable, it leads to the absolute continuity of the spectrum of the corresponding unitary operators. As an illustration, we consider time changes of horocycle flows, skew products over translations and Furstenberg transformations. For time changes of horocycle flows we obtain absolute continuity under assumptions weaker than those to be found in the literature, and for skew products over translations and Furstenberg transformations we obtain countable Lebesgue spectrum under assumptions not previously covered in the literature.

Position‐sensorless method for electric braking commutation of brushless DC machines

To increase the cruising distance and braking reliability of various light electric vehicles (LEVs) actuated by brushless DC machines, this study proposes three cost-effective braking commutation strategies based on a general full-bridge DC/AC inverter without using position sensors. The braking commutation strategies investigated in this study are named according to the number of power switches in action over each commutation state; designated as single-switch, two-switch, and three-switch, respectively. Theoretical analysis of the operation principle and important performance indices such as maximum voltage conversion ratio, braking torque, energy recovery ratio etc, are conducted and compared among each commutation strategy. Moreover, a cost-effective, sensorless method for each different braking commutation strategy is used. The commutation signals are extracted directly from the average terminal voltages. Since additional power switches, passive components and costly position sensors are not essential, the proposed method is particularly suitable for various LEVs such as electric bicycles, electric scooters, electric wheelchairs and so on. Finally, several experiments are performed to justify the effectiveness of the proposed method.

Commutator methods for unitary operators

We present an improved version of commutatormethods for unitary operators under a weak regularity condition. Once applied to a unitary operator, the method typically leads to the absence of singularly continuous spectrum and to the local finiteness of point spectrum. Large families of locally smooth operators are also exhibited. Half of the paper is dedicated to applications, and a special emphasis is put on the study of cocycles over irrational rotations. It is apparently the first time that commutator methods are applied in the context of rotation algebras, for the study of their generators.

Automation of construction of characteristic curves in impulse control problems for the power amplifier-servomotor system. I. Speed-torque characteristics

An automated approach to deriving analytical expressions for the speed-torque characteristics for an arbitrary impulse control method for the power amplifier-servomotor electric drive system is developed. Mathematical expressions for the speed-torque characteristics for impulse modes and commutation methods are obtained based on the suggested approach, and an interactive application is developed. This application makes it possible to represent the family of speed-torque characteristics for the corresponding control method and impulse mode and study voltage and current wave-form diagrams at an arbitrary point of the speed-torque characteristics for the given motor parameters and pulse-width modulation period. Automation of the procedure of deriving analytical expressions and the development of the interactive application were carried out using the Mathematica system.

High-performance doubly fed induction machine drive system using predictive direct torque control drive system fed by indirect matrix converters

SUMMARY This paper presents a novel predictive direct torque control for doubly fed induction machine based on indirect matrix converter (IMC), which is characterized by its simple structure, minimal-torque ripple, and constant switching frequency. Nowadays, the control strategies based on predictive methods have proved their efficiency to improve drive systems capabilities. So, in this paper, one of the best predictive methods that have recently been suggested for doubly fed induction machine drive systems is applied to IMC. The purpose of this combination is to modify the control parameters and size/volume reduction of drive system structure, which is difficult to achieve in conventional systems based on voltage source inverters. The good tracking behavior with reduced torque and flux ripple for both motoring and generating modes as well as removing bulky electrolytic capacitor from the DC link of a converter resulted by using three vectors, two active vectors together with one zero vector per switching period, and applying these vectors to the inverter stage of IMC. To improve the motor drive system performance and reduce losses caused by snubber circuits, the rectifier four-step commutation method in rectifier bridge is used. In the inverter stage, the predictive direct torque control method is employed. The simulation results of the proposed model confirm its effectiveness and accuracy. Copyright © 2013 John Wiley & Sons, Ltd.

彩色图像处理的可交换Clifford代数方法

By using the commutative Clifford algebra method to model for a color image,the parallel processing of R,G and B components in the color image can be realized in a holistic manner and the integrating processing for the color image can be implemented. This paper reviews the progress of color image modeling,researches a type of commutative Clifford algebra,namely Clcom2and gives the definitions of the arithmetic operations,unit element,inverse element,conjugation,and the norm for the commutative Clifford algebra. Then,it describes the expression of the color image based on the commutative Clifford algebra and introduces an application example of this method: the edge detection of color image. In comparison with the quaternion-based color image modeling,the proposed method can remove the data redundancy and reduce the computational complexity to the utmost extent. The proposed color image modeling method can be applied in color image processing tasks as a useful tool.

Design of BLDCM Fuzzy Control System for Electric Vehicle Based on DSP

In this paper, the design of BLDCM fuzzy control system for electric vehicle which bases on TMS320F2812 Digital Signal Processor (DSP) is given. The design methods of hardware and software of the control system are described in details. Using of brushless DC motor current and speed double closed loop control, meanwhile, the fuzzy self-tuning PI algorithm is applied in the control system, and achieve the intelligent control of brushless DC motor control system. In this paper, the PWM control of the overlapping commutation method to suppress torque ripple. Experimental results show that this system has such characteristics as sound controlling effects, obvious restrain of torque pulsation and reliable operation.

Comparison of Two Overmodulation Strategies in an Indirect Matrix Converter

This paper discusses two overmodulation controls, namely, square wave and trapezoidal, in the indirect matrix converter (IMC) for motor drive application. The differences between these two modulations are analyzed based on the output-input voltage transfer ratio (VTR), the efficiency, and the current total harmonic distortions under two load conditions. Moreover, the performance is then improved by implementing four-step commutation methods in the primary side of the IMC. The validity of the proposed methods will be demonstrated through simulation and experimentally. The experimental results show that the VTR can be improved from 0.866 to 0.97 in the square wave modulation and 0.92 for the trapezoidal wave modulation in an induction motor drive system.

Current-bounded commutation of a long-stroke magnetically levitated stage with moving coils

Magnetically levitated stages(MLS) have potentials to obtain good motion performances in high vacuum environment. Yet the electromagnetic forces/torques corresponding to six degrees of freedom(DOF) motions have coupling relationship with each current of coil array, and this coupling is still associated with the relative positions between the mover and the stator of the stage. So it is quite difficult to control the 6-DOF motions of the stage. By reasonable commutation of coil array, this complicated coupling relationship can be decoupled. The analytical force/torque-decomposing model of the stage is established first. Then the initial currents of coil array are commutated based on the pseudo inverse of the analytical force/torque-decomposing model matrix. And then the coil array currents are commutated again with different current bounds given to the initial currents as well as in the sense of minimum 2-norm of currents vector. Using the long stroke magnetically levitated stage with moving coils under investigation as examples, the currents of coil array are commutated with different current bounds adopting the proposed commutation method, the determination of current bound and the current bounds’ influences on the heat-losses in coil array are analyzed, and the effectiveness of implementation algorithm of proposed commutation method is discussed. Simulation, analysis and discussion results indicate that the currents of coil array within the given current bound can be solved analytically by proposed commutation method, and the implementation algorithm does not need any searching or iteration. By the current-bounded commutation method proposed, the amplitude of coil array currents can be limited within an appropriate current bound(This is very beneficial to the improvement of the reliability and motion performance of the stage), as well as these currents can also generate the desired forces and torques.

SEMI F47을 만족하는 10kW급 3상 전압 새그 보상기 개발

3-Phase voltage sag compensator protects a critical load from grid sags. The paper presents an algorithm and design of 3-phase voltage compensator. Compensator algorithm consists of a 3-phase voltage sag detection, thyrister commutation method and inverter output voltage control. The compensator satisfies SEMI F47 standard and 10kW 3-phase voltage sag compensator prototype is assembled. Validity of the proposed compensator is verified by simulation and experiment.

Analysis Method of the Dynamic Force and Torque Distribution in the Magnet Array of a Commutated Magnetically Levitated Planar Actuator

This paper concerns the analysis of the dynamic forces and torques acting on the magnets in a Halbach permanent magnet array of a magnetically levitated moving-magnet planar actuator. A new analysis tool is presented which predicts the dynamic force and torque distribution on the magnet array. This design tool uses lookup table data, which are generated by numerically solving the Lorentz force and torque integral, to describe the force and torque between each magnet and coil in the topology. It offers a fast and accurate solution for the analysis of magnetically levitated planar actuators. The results for two different commutation methods are presented.

Investigation of Commutative Properties of Discontinuous Galerkin Methods in PDE Constrained Optimal Control Problems

The aim of this paper is to investigate commutative properties of a large family of discontinuous Galerkin (DG) methods applied to optimal control problems governed by the advection-diffusion equations. To compute numerical solutions of PDE constrained optimal control problems there are two main approaches: optimize-then-discretize and discretize-then-optimize. These two approaches do not always coincide and may lead to substantially different numerical solutions. The methods for which these two approaches do coincide we call commutative. In the theory of single equations, there is a related notion of adjoint or dual consistency. In this paper we classify DG methods both in primary and mixed forms and derive necessary conditions that can be used to develop new commutative methods. We will also derive error estimates in the energy and L 2 norms. Numerical examples reveal that in the context of PDE constrained optimal control problems a special care needs to be taken to compute the solutions. For example, choosing non-commutative methods and discretize-then-optimize approach may result in a badly behaved numerical solution.

The Application of Resonant Controllers to Four-Leg Matrix Converters Feeding Unbalanced or Nonlinear Loads

Matrix converters (MC) have some advantages when compared to conventional back-to-back pulsewidth modulation voltage-source converters. The MC may be considered more reliable and is smaller because the bulky dc capacitor is eliminated from the topology. Therefore, when MCs are used in ac-ac power conversion, the size and weight of the whole generation system is reduced. To interface a MC-based generation system to an unbalanced three-phase stand-alone load, a four-leg MC is required to provide an electrical path for the zero-sequence load current. Moreover, to compensate for the voltage drops in the output filter inductances, nonlinearities introduced by the four-step commutation method and voltage drops in the semiconductor devices, closed-loop regulation of the load voltage is required. In this paper, the design and implementation of a resonant control system for four-leg MCs is presented. The application of this control methodology when the four-leg MC is feeding, a linear/nonlinear unbalanced load is also presented in this study. High-order resonant controllers are also analyzed. Experimental results, obtained from a small prototype, are discussed.

Matrix Converter Based on Asymmetric Regular Sampling Method SPWM Control Strategy

In this paper, the Matrix converter can be viewed as AC-DC-AC converter, the asymmetric regular sampling method SPWM control technique is applied in the control of matrix converter, the asymmetric regular sampling method SPWM control strategy of matrix converter, 48 allowed switch combinations and Four-Step Current Commutation method is presented. Based on Matlab/simulink the simulation of the matrix converter with such strategy is carried out. Inductive load simulation is carried out on the matrix converter prototype. The simulation results verify the workability of the asymmetric regular sampling method SPWM strategy for matrix converter.

Spectral analysis of time changes of horocycle flows

We prove (under the condition of A. G. Kushnirenko) that all time changes of thehorocycle flow have purely absolutely continuous spectrum in the orthocomplement ofthe constant functions. This provides an answer to a question of A. Katok and J.-P.Thouvenot on the spectral nature of time changes of horocycle flows. Our proofs relyon positive commutator methods for self-adjoint operators.

A Novel Four-Step Commutation for Bidirectional Switch Cells of AC-AC Matrix Converter

A novel four-step commutation is proposed with unequal step for each bidirectional switch cell on the basis on analysis of many proposed commutation methods of matrix converter in this paper. The first and fourth step can be shorter than the second or third one because the actual switching on or off of output current happens on the second and third steps. Here the second step is equal to the third one. This method is implemented with four steps by programming in VHDL language. First, the special flip-flop, 74AHC16373, is obtained by programming so as to make input sector signals, output sector ones and active switching time PWM ones synchronize. Second, the required switching states are flexibly realized in the form of the look-up table by programming in VHDL language for 36 switching combinations of input sectors with output ones. Third, the obtained switching states are judged whether they need commutation by delayers. Finally, the novel method proposed is implemented by switching sequencers. The simulation results have verified its feasibility.