Commutation Method Research Articles

Fast Self-Correction Commutation Method for High-Speed Sensorless BLDCMs With Nonideal Asymmetric Back EMF

Fast Self-Correction Commutation Method for High-Speed Sensorless BLDCMs With Nonideal Asymmetric Back EMF

Direct single‐phase isolated improved gamma Z‐source AC–AC converter suitable for DVR application

AbstractA direct single‐phase isolated improved gamma Z‐source AC–AC converter is designed and manufactured in proposed paper. This converter contains an impedance source structure and its advantages. In general, these advantages are as follows. Firstly, the proposed structure has a wide range of output voltage as boost and buck as well as in‐phase or out‐of‐phase states. Secondly, the proposed converter is electrically isolated thanks to a high frequency transformer (HFT), which significantly reduces the volume of the structure; therefore, in applications such as dynamic voltage restorer (DVR), there is no need to install a coupling transformer with the grid frequency which is very bulky and full of losses. Furthermore, the HFT of the proposed converter is a three winding transformer which also acts as the inductance needed for impedance source network. In addition, the safe commutation method has been utilized, which reduces the voltage spikes on the power switches. Finally, the analysis and design of this converter has been done, and then confirmed by a small‐scale laboratory prototype.

Implementation of modified trapezoidal commutation scheme for speed control of 1 kW BLDC motor

The commutation process in brushless DC (BLDC) motors is done electrically and depends on the rotor position feedback. The Six-Step method is the most commonly used method in BLDC control, as it is easy to implement. However, this method has a high root mean square (RMS) current. On the other hand, a perfect sinusoidal commutation method is very complicated. Therefore, this research proposes a simple modified scheme of trapezoidal commutation circuits that can produce sinusoidal BLDC output voltage. This circuit can still responsively control the speed of the BLDC motor. This scheme uses 2 Arduinos. Pulse width modulation (PWM) signal from Arduino2 is then combined with hall signals from Arduino1, resulting in six outputs which are modified electrical commutation signals. This commutation signal is used as a MOSFET controller in a 3-phase inverter to produce a sinusoidal waveform. The average efficiency obtained when implementing the commutation is 75 % at low and high speeds.

Local Smoothing Estimates for Schrödinger Equations on Hyperbolic Space

We establish global-in-time frequency localized local smoothing estimates for Schrödinger equations on hyperbolic space H d \mathbb {H}^d , d ≥ 2 d \geq 2 . In the presence of symmetric first and zeroth order potentials, which are possibly time-dependent, possibly large, and have sufficiently fast polynomial decay, these estimates are proved up to a localized lower order error. Then in the time-independent case, we show that a spectral condition (namely, absence of threshold resonances) implies the full local smoothing estimates (without any error), after projecting to the continuous spectrum. In the process, as a means to localize in frequency, we develop a general Littlewood–Paley machinery on H d \mathbb {H}^d based on the heat flow. Our results and techniques are motivated by applications to the problem of stability of solitary waves to nonlinear Schrödinger-type equations on H d \mathbb {H}^{d} . Specifically, some of the estimates established in this paper play a crucial role in the authors’ proof of the nonlinear asymptotic stability of harmonic maps under the Schrödinger maps evolution on the hyperbolic plane; see Lawrie, Lührmann, Oh, and Shahshahani, 2023. As a testament of the robustness of approach, which is based on the positive commutator method and a heat flow based Littlewood-Paley theory, we also show that the main results are stable under small time-dependent perturbations, including polynomially decaying second order ones, and small lower order nonsymmetric perturbations.

A fuse‐based DC circuit breaker with vacuum interrupter enhanced by an external transverse magnetic field

AbstractDue to the increasing power system capacity, the interruption of large fault currents has gradually become a major challenge in power systems. At the moment, such currents are interrupted mainly via circuit breakers based on the method of active current commutation. However, these types of circuit breakers tend to be costly and oversized. One possible alternative—a fuse‐based circuit breaker with current commutation process enhanced by an external transverse magnetic field (ETMF)—is proposed by the authors. Its main advantage lies in the fast current commutation achieved by an ETMF‐enhanced three‐stage increase of the vacuum arc voltage. The study of the current commutation process is mainly represented by the authors, and the influencing factors of the current commutation—contact opening speed and ETMF current—are discussed. At last, the proposed circuit breaker is verified by an experiment, whose results show that a short‐circuit current of 42 kA can be interrupted within just 2 ms.

Bi-commutative digital contraction mapping and fixed point theorem on digital image and metric spaces

The contraction mapping theorem is a powerful and most useful method in constructing the solution of linear and nonlinear systems. The principle of Banach fixed point guarantees that a self-contraction mapping of a complete metric space has a unique fixed point which can be obtain using the limit of iteration technique defined by repeated images under mapping of an arbitrary starting point in space. In this paper, we propose a Bi-commutative (II-commuting) digital maps for Kannan and Reich contraction mapping theorem and analyze the existence and uniqueness of the fixed point in the framework of digital metric spaces. We applied the contraction and commutative maps methods in proving our results. The results obtained satisfies the existence and uniqueness condition of the Banach contraction principle for a digital contraction mapping in digital metric space.

A New Four-Step Commutation Method for Indirect Matrix Converter With Active-Voltage Vectors Being Applied

The existing two commutation methods of the rectifier stage for indirect matrix converter (IMC) are zero-current commutation and four-step commutation. The premise of zero-current commutation is that the inverter stage of IMC uses a zero-voltage vector, but when the inverter stage cannot use zero-voltage vectors (such as space overmodulation, common mode suppression modulation, etc.), the four-step commutation is adopted. The conventional four-step commutation method has a complex switching sequence and requires additional sensors. Based on the natural freewheeling characteristic of IMC and the switching sequence of zero-current commutation, a new four-step commutation method is proposed when active-voltage vectors are applied in the inverter stage, first turn off the two switches at 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> and 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> steps, and then turn on the two switches at 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> and 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> steps. The switching sequence of the new four-step commutation is not affected by the polarity of input voltage or output current direction, thus solving the complexity switching sequence problem of the conventional four-step commutation, and does not require additional voltage or current sensors, making the IMC commutation process safer and more reliable. Finally, this paper verifies the effectiveness of the new four-step commutation method of IMC through experiments.

Improved sharp spectral inequalities for Schrödinger operators on the semi-axis

We prove a Lieb–Thirring inequality for Schrödinger operators -\frac{\mathrm{d}^2}{\mathrm{d}x^2}+V on the semi-axis with Robin boundary condition at the origin. The result improves on a bound obtained by P. Exner, A. Laptev, and M. Usman [Commun. Math. Phys. 362 (2014), 531–541] albeit under the additional assumption V\in L^1(\mathbb{R}_+) . The main difference in our proof is that we use the double commutation method in place of the single commutation method. We also establish an improved inequality in the case of a Dirichlet boundary condition.

Performance Evaluation of Brushless Direct Current Motor Control Methods through Low-Cost Microcontroller-Based Real-Time Experiments

Brushless direct current (BLDC) motors are high efficiency synchronous motors that are employed in a variety of applications due to prominent features such as long operational life, low maintenance requirements, and great dynamic response. BLDC motors are driven by energizing the motor stator windings with an inverter circuit. To commute the inverter switches, the trapezoidal (120°) method is generally used by considering the back electromagnetic force induced on unenergized phase of BLDC. Furthermore, depending on the application requirements, alternative commutation modes (CM) such as 180°, 150°, and sinusoidal-based approaches are utilized. In the literature, the performance comparison of some CMs was studied for two-phase on operation and three-phase on operation mode as a switching pattern. However, only a few research assessed the performance of two or three commutation modes simultaneously. In this study, the performance comparison of pulse width modulation (PWM) based commutation modes are examined by considering 120°, 180°, 150° modes, and sinusoidal PWM. In this scope, it is the first time that direct digital synthesis (DDS) is addressed as a BLDC control algorithm in a performance comparison study. In experimental studies, a simple and a low-cost drive circuit is designed to acquire the case results. According to the results, the proposed DDS-based sine commutation method is more efficient than other commutation methods and it has lower power consumption at both low and high speeds also a wider operable speed range.

RESEARCH OF VALVE MOTOR CONVERTER CONTROL METHODS

A technique for selecting the electrical equipment of a valve motor with machine commutation has been developed, which takes into account the ways of controlling the inverter. The installed capacity of the electrical equipment of the valve motor (VD) is determined by technological requirements and depends on the structure of the converter, the method of commutation of the converter keys and the methods of controlling the inverter. The use of autonomous inverters with artificial switching, the keys of which are switched due to the reactive energy accumulated in additional switching devices, increases the utilization factor of the synchronous machine. However, in this case, the circuit becomes more complicated and the installed power of the converter increases. The use of IGBT transistors and IGCT thyristors leads to a significant increase in the cost of the equipment.&#x0D; To reduce the influence of the rectifier VD on the network and match the drive voltage with the supply voltage, a matching transformer and reactive power compensation device may be needed. The amount of power of this equipment is affected by the method of controlling the rectifier, the nature of the engine load and the range of speed changes.&#x0D; Voltage regulation of the rectifier can be symmetrical or asymmetrical. Several methods of asymmetric regulation are known, among which one of the most expedient is alternating. In the case of alternating control in the three-phase bridge circuit, an artificial zero circuit is created, as a result of which the duration of the current flowing through the secondary windings of the transformer becomes less than 2/3 of the half-cycle of the supply voltage. In addition, the energy indicators also increase, in particular, the reactive power consumption decreases and the shift and power coefficients increase.

Lieb—Thirring type bounds for perturbed Schrödinger operators with single-well potentials

We prove an upper bound on the sum of distances between eigenvalues of a perturbed Schrödinger operator H0 − V and the lowest eigenvalue of H0. Our results hold for operators H0 = −Δ − V0 in one dimension with single-well potentials. We rely on a variation of the well-known commutation method. In Pöschl–Teller and Coulomb cases, we are able to use explicit factorizations to establish improved bounds.

Extended Operation of Brushless DC Motors Beyond 120° Under Maximum Torque Per Ampere Control

Hall-sensor-controlled brushless dc (BLDC) motors are widely used in many electromechanical applications due to their simplicity and good torque-speed characteristics. The conventional commutation methods include the 120° and 180° switching logics that can be derived directly from the Hall sensor signals. The 120° switching method is the most common due to its natural approximation of the maximum torque per Ampere (MTPA) operation, while the 180° switching method offers a higher available phase voltage for the same dc voltage. Both methods are typically used with additional pulse-width modulation to control the motors from a fixed dc source. Recently, attention has been given to the operation of BLDC motors with conduction angles between 120° and 180° (e.g., 150°, 160°, etc.), where some benefits may be gained. This paper proposes a new methodology that continuously extends the operation from 120° to 180°, while maintaining the MTPA property. Simulations and experimental results based on a typical industrial BLDC motor demonstrate the proposed control methodology and its benefits over the conventional alternative methods.

An isolated high‐gain impedance source‐based single‐phase AC–AC converter with safe commutation and variable output frequency

SummaryConventional AC–AC converters have some critical disadvantages, such as inappropriate input and output power quality features, employing snubber circuits to suppress the voltage stress on high‐frequency switches without a safe commutation method that increases the converter size and cost, confined voltage gain, and using huge passive components. This paper proposes an isolated high‐gain single‐phase AC–AC converter with variable output frequency, extended voltage gain, and a safe commutation strategy. Ten semiconductors are only employed for the proposed topology that only two switches and two diodes are operated with high‐frequency PWM signals. This new topology has noteworthy specifications like continuous input and output current, voltage isolation, extended inverting and non‐inverting buck‐boost modes, and frequency regulation. The high voltage gain has been achieved with small values for passive components in the impedance source section, reducing the volume and cost of the converter. The impedance source‐based section of the converter comprises one input inductor, two coupled inductors, and two capacitors in each converter leg. A safe commutation strategy has been designed and applied to the converter to mitigate the voltage and current stresses without extra snubber circuits. The number of semiconductors that simultaneously conduct in each state of the converter has been reduced. So, the conduction loss of the converter diminished. The achieved efficiency equals 95.5% and 93.5% in step‐down and step‐up modes, respectively, validated by an accurate power loss model and experimental analysis. An experimental prototype has been designed to confirm the performance of the suggested converter. Results confirm the theory and operation of the proposed converter.

A continuous analog of the binary Darboux transformation for the Korteweg–de Vries equation

AbstractIn the Korteweg–de Vries equation (KdV) context, we put forward a continuous version of the binary Darboux transformation (aka the double commutation method). Our approach is based on the Riemann–Hilbert problem and yields a new explicit formula for perturbation of the negative spectrum of a wide class of step‐type potentials without changing the rest of the scattering data. This extends the previously known formulas for inserting/removing finitely many bound states to arbitrary sets of negative spectrum of arbitrary nature. In the KdV context, our method offers same benefits as the classical binary Darboux transformation does.

Development of four‐terminal DC circuit breaker based on commutating path multiplexing

AbstractMulti‐terminal flexible DC power grid plays an important role in large‐scale new energy integration, which usually requires the installation of multi‐terminal DC circuit breaker (MTCB) at the intersection of multiple DC lines. At present, the research on multi‐terminal DC circuit breaker is mostly limited to theoretical simulation calculation, and there are few experimental studies and engineering applications. In this paper, a four‐terminal DC circuit breaker based on commutating path multiplexing is proposed, which combines with the compact natural commutation scheme of hybrid gap, greatly reducing the cost and volume of the circuit breaker. The commutation characteristics of the four‐terminal hybrid DC circuit breaker equivalent prototype at 10‐kV voltage level were tested. On this basis, the equivalent prototype of the circuit breaker test results shows that under 10‐kV voltage level, the four‐terminal circuit breaker topology can achieve breaking of 11 kA in 2.8 ms by the natural commutation method.

Three‐phase wireless power supply system using a matrix converter

AbstractThis paper proposes a three‐phase wireless power transfer (WPT) system with a three‐phase‐to‐three‐phase matrix converter. The proposed system directly converts power from an AC grid to high‐frequency AC for WPT. The three‐phase WPT system with the matrix converter is effectively expands the lifetime of the WPT system. A novel hybrid commutation method, which is suitable for the WPT system with a resonant characteristic, is proposed to avoid the commutation failure of the matrix converter. The strategy of the proposed hybrid commutation is based on an estimation of the current direction considering the resonant characteristics and elimination of commutation in the critical area. The proposed commutation method achieves an AC input‐current total harmonic distortion (THD) of 4.7% with the resonant three‐phase load without a current sensor on the high‐frequency side. Furthermore, the proposed WPT system achieves a system efficiency of 88.2% at a load of 4 kW.

A Novel Three-Step Commutation Method for Direct Matrix Converter Free From Inrush Current and Voltage Error

The direct matrix converter is a well-accepted topology for AC/AC converters. The commutation method should be considered in the direct matrix converter topology to avoid failures caused by the input short circuit and output open circuit during commutations. The conventional three-step commutation method of input voltage not only avoids the aforementioned failures but also removes errors between actual and command output voltage. However, it increases the number of hard switching and the flow of inrush current originating from the mismatch between the turn-on and turn-off delay time of switches. This paper proposes a new three-step commutation method that eliminates inrush current and reduces the number of hard switching. In this way, the conversion efficiency is improved, and circuit hazards caused by inrush current are over. Meanwhile, the proposed commutation method keeps the advantage of canceling the voltage error of conventional three-step commutation. Noteworthy that the proposed commutation method is introduced based on a novel fixed-slope direct duty ratio PWM simplifying the practical implementation. The performance and effectiveness of the proposed method have been verified by simulation and experimental results.

Voltage-Fed Isolated Matrix-Type AC/DC Converter for Wind Energy Conversion System

In this article, a voltage-fed isolated matrix-type ac/dc converter (VF-MC) is proposed for wind energy conversion system (WECS). Instead of the line-frequency transformer, the high-frequency transformer (HFT) is used for isolation between the generator and the grid. The direct matrix converter (MC) is employed to connect the wind power generator and the HFT, and the intermediate dc capacitors are saved in the ac/ac conversion. Moreover, the proposed VF-MC can work without use of filter capacitors on generator side, and enable more compact size. The dedicated space-vector-modulation scheme and commutation method are proposed for safe operation of the MC. The voltage spikes due to the leakage inductance of HFT are thus reduced and the additional snubber circuit is avoided in the proposed system. A 1-kW laboratory prototype of the proposed VF-MC-based WECS is built to verify the effectiveness of the system experimentally.

Commutator method for averaging lemmas

We introduce a commutator method with multipliers to prove averaging lemmas, the regularizing effect for the velocity average of solutions for kinetic equations. This method requires only elementary techniques in Fourier analysis and shows a new range of assumptions that are sufficient for the velocity average to be in $L^2([0,T],H^{1/2}_x).$ This result not only shows an interesting connection between averaging lemmas and local smoothing property of dispersive equations, but also provide a direct proof for the regularizing effect for the measure-valued solutions of scalar conservation laws in space dimension one.

A single‐phase p‐type ac–ac converter with reduced components count and high boost factor

AbstractThis paper proposes a new single‐phase direct step‐up ac–ac converter by modifying the p‐type impedance source. It provides a high boost factor as well as high efficiency, while only six parts are required to design it, involving just two bidirectional power switches. A safe commutation method has been applied to power switches to make the converter snubber‐free and high efficient. Input and output harmonic filters are no longer required since input and output currents variate continuously with small ripple and low total harmonic distortion (THD). The proposed topology only modulates the output voltage amplitude, not the phase and frequency, so the output frequency is identical to the input frequency and constant. Thus, it can be utilized in step‐up conversion applications, like inductive power transmission from low ac voltage sources. Input and output have the same ground, which is a good protective feature. In this paper, the operating principle of the converter is demonstrated. Experimental results have been represented to evaluate the performance of the converter. For this purpose, an experimental prototype has been fabricated. Results are investigated and compared with other previous step‐up ac–ac converters. Results confirm the theory, operating principle, and performance of the converter.