Commutation Period Research Articles

Investigating the principle and application of high-frequency and high-voltage pulse AC equipment for oil–water separation of heavy crude oil

To address the challenges of oil–water separation encountered during the processing of heavy crude oil, this study meticulously examines the kinetics of demulsification under an electric field. Consequently, a cutting-edge high-frequency/high-voltage AC pulsed power supply has been innovatively developed. This device boasts a flexible voltage-adjustment mechanism, strategically enhancing the inverter output voltage incrementally throughout the pulse’s duration. This method effectively reduces the negative impact of current surges on the operational stability of crude oil desalination plants, especially during the commutation periods of the switching devices. Furthermore, it resolves the issue of premature power supply shutdowns to the desalination plant, caused by peak currents misinterpreted as critical short-circuit currents leading to pole plate breakdowns. An industrial application study conducted at Shandong Chambroad Petrochemicals Co., Ltd. Under identical operational conditions, the power supply designed in this research outperforms traditional electrical desalting transformers in several key aspects. These include a notably enhanced oil–water separation capability and significantly more stable performance. Remarkably, the desalting efficiency shows substantial improvement even at increased feed rates, under constant other conditions. The experimental findings indicate that the average rates of desalination and dehydration achieved by this power supply exceed 90%. Moreover, even when the feed rate is augmented by approximately 75% under constant operating conditions, the desalination efficiency remains 78.49% higher than that achieved by standard industrial frequency electric desalination transformers. Additionally, the desalting outcomes are predominantly unaffected by fluctuations in the initial salt content of the feedstock, demonstrating the robustness of the developed solution.

Ultrafine particle measurements in New York State

Measurements of ultrafine particles (UFP) over several years were carried out across seven different locations in New York State. The locations include urban background sites (Queens College and Albany), near road sites (Queens, Buffalo and Rochester) and rural sites (Pinnacle State Park and Whiteface Mountain). UFP at the urban background and near road sites generally show highest concentrations in the morning during the early commute period. Concentrations decrease during the day but increase again in the afternoon or evening period. Weekday concentrations are higher than on weekends. UFP correlates well with traffic related co-pollutants black carbon (BC) and nitrogen oxides (NOx). At the rural locations, UFP concentrations show less variation during the day with highest concentrations in the early afternoon to late evening hours particularly in spring. Seasonally, UFP concentrations across urban background and near road sites, are highest in winter (Dec, Jan, Feb) and lowest in summer (Jun, Jul, Aug). The variation in UFP concentration with temperature, relative humidity and wind speed was investigated. At the Queens College site, particle number concentrations in six different size fractions were measured using a TSI 3031 instrument. Annual average UFP concentrations at Queens College were found to decrease over time consistent with emission control strategies.

A novel technique for torque ripple suppression in BLDC motor drive using switched capacitor based SEPIC converter

This article reports a strategy for suppressing commutation torque ripple has been proposed by modifying a SEPIC converter using switched capacitor. The torque ripple generated during the commutation period is one of the main disadvantages of a brushless DC (BLDC) motor. The cause for the torque ripple in brushless DC motor has been mathematically analyzed in this work. Henceforth, a modified switched-capacitor based DC-DC converter has been proposed for integration with BLDC drive. Moreover, a theoretical analysis of the relationship has been established between the duty ratio of the DC-DC converter with commutation time and torque ripple. A low cost and simple method to control the dc link voltage of BLDC drive has been proposed and a comparative analysis of the proposed converter with previously existing similar converters has been shown. This work aims at reducing ripple in electromagnetic torque of BLDC motor from the view point of duty ratio of the DC-DC converter and commutation time of the drive. The feasibility of the drive has been evaluated experimentally and through simulation. It has been observed that the integration of the proposed converter with BLDC drive help in torque ripple suppression to 16.5% as compared to BLDC drive without any DC-DC converter.

Commutation torque ripple suppression method for brushless DC motors with minimum phase shift angle

SummaryCommutation torque ripple occurs when brushless DC (BLDC) motor runs in the high‐speed range, which degrades operation performance. To overcome the problem, this paper presents a commutation torque ripple suppression method based on the minimum phase shift angle (MPSA) of hall signals. In the paper, the effect of the phase shift angle (PSA) of hall signals on phase current is analyzed, and the MPSA is deduced on the basis of the unit duty cycle of the incoming and non‐commutation phase. With the proposed method, two‐phase conduction mode is used in the full speed range, commutation period and non‐commutation period, which avoids switching modulation mode and enhances system reliability. The proposed method is implemented through shifting hall signals by the MPSA, and it is simple and feasible without the requirement to redesign a controller. Moreover, no additional power devices and precise sensors are required, which reduces design cost and volume size. The proposed method is experimentally compared with different methods under steady operation condition, and the results show superior performance on suppressing commutation torque ripple. The loading experiment demonstrates that the proposed method exhibits good dynamic response. The frequency spectrum of the electromagnetic torque is analyzed, and it is verified that the 6nf harmonics are diminished with the proposed method.

Estimating morning and evening commute period O3 concentration in Taiwan using a fine spatial-temporal resolution ensemble mixed spatial model with Geo-AI technology

Elevated levels of ground-level ozone (O3) can have harmful effects on health. While previous studies have focused mainly on daily averages and daytime patterns, it's crucial to consider the effects of air pollution during daily commutes, as this can significantly contribute to overall exposure. This study is also the first to employ an ensemble mixed spatial model (EMSM) that integrates multiple machine learning algorithms and predictor variables selected using Shapley Additive exExplanations (SHAP) values to predict spatial-temporal fluctuations in O3 concentrations across the entire island of Taiwan. We utilized geospatial-artificial intelligence (Geo-AI), incorporating kriging, land use regression (LUR), machine learning (random forest (RF), categorical boosting (CatBoost), gradient boosting (GBM), extreme gradient boosting (XGBoost), and light gradient boosting (LightGBM)), and ensemble learning techniques to develop ensemble mixed spatial models (EMSMs) for morning and evening commute periods. The EMSMs were used to estimate long-term spatiotemporal variations of O3 levels, accounting for in-situ measurements, meteorological factors, geospatial predictors, and social and seasonal influences over a 26-year period. Compared to conventional LUR-based approaches, the EMSMs improved performance by 58% for both commute periods, with high explanatory power and an adjusted R2 of 0.91. Internal and external validation procedures and verification of O3 concentrations at the upper percentile ranges (in 1%, 5%, 10%, 15%, 20%, and 25%) and other conditions (including rain, no rain, weekday, weekend, festival, and no festival) have demonstrated that the models are stable and free from overfitting issues. Estimation maps were generated to examine changes in O3 levels before and during the implementation of COVID-19 restrictions. These findings provide accurate variations of O3 levels in commute period with high spatiotemporal resolution of daily and 50m * 50m grid, which can support control pollution efforts and aid in epidemiological studies.

Torque Ripple Minimization Technique of Position Sensorless BLDC Motor for Variable Speed Drives

Brushless Direct Current (BLDC) motors are advantageous because of their higher efficiency, higher speed operations and higher power density. Industrial applications demand BLDC motors free from torque ripple. The torque ripple is due to the unequal commutation period between the energised phase and unenergized phase current. It is a perilous problem in sensorless BLDC drive as it leads to speed oscillations, acoustic noise, serious faults, and vibration in machines. The torque ripple can be reduced either by improving motor design parameter or by improving the motor control strategy. This paper proposes a Proportional Integral (PI) controller-based control scheme for a cuk converter driven sensorless BLDC motor to reduce the torque ripple. The proposed scheme invokes Zero Crossing Point (ZCP) detection with back emf sensing approach. The presence of inductor reduces the ripple in the input and output currents. The performance of the strategy is verified using MATLAB R2018a Simulink for different operating conditions of a BLDC drive and the results prove that the recommended scheme decreases the torque ripple compared to the conventional scheme.

Pulse Width Modulation Methods for Minimizing Commutation Torque Ripples in Low Inductance Brushless DC Motor Drives

This paper proposes pulse width modulation (PWM) methods for low inductance brushless DC (BLDC) motor drives that minimize the commutation torque ripples. An uneven current of non-commutation phase generates the commutation torque ripples. In the low inductance BLDC motor drives, two types of time delays in PWM also induce critical torque ripples. In this paper, the analyses of the time delays in PWM and their effects are introduced. Then, two PWM methods are proposed to eliminate the time delays in the commutation region and the conduction region, respectively. The commutation period is controlled to be synchronized to the switching period. In addition, the proposed methods synchronize the switching period to the commutation interrupt. As a result, the proposed methods effectively maintain the minimum commutation period as well as minimize the commutation torque ripples in the low inductance BLDC motor drives. The validity of the proposed methods is demonstrated by the simulation and experimental results in various driving conditions. The results show that the commutation period is remarkably shortened and the commutation torque ripples are reduced by 27.6% in comparison to the conventional method.

Simulation Approach for Torque Ripple Minimization of BLDC Motor

This project presents the design and implementation of neural network controller for reducing torque ripples in permanent magnet brushless DC (PMBLDCM) motor drive with trapezoidal back-emf. The performances of the proposed neural network controller are compared with the corresponding fuzzy PI controller and conventional PI controller. Simulation results are used to show the abilities and shortcomings of the proposed speed regulation scheme for brushless dc motor which is considered as a highly nonlinear dynamic complex system. Matlab/Simulink software was used to simulate the proposed model. Buck-boost converter connected in between the input DC source and three phase bridge inverter, used for minimizing the commutation torque ripples in Permanent Magnet Brushless DC Motor is presented in this paper. Torque during the commutation period depends on phase current which is not undergoing commutation, so by controlling it, torque ripple can be minimized. Moreover, a greater DC link voltage is needed during the commutation time period in comparison to the normal conduction period. The Buck-boost converter operates in boost mode in commutation period for stepping up the DC voltage to the inverter. A simple mode switching circuit is employed to amend the output modes of the Buck-boost converter in normal and commutation time intervals. Simulation studies of this topology are carried out in MATLAB/Simulink environment. Index Terms – Permanent Magnet Brushless DC Motor (PMBLDCM), Buck-boost Converter, Commutation Time period,PI Controller.

High-Efficiency Asymmetrical Half-Bridge Converter With Linear Voltage Gain

A conventional asymmetrical half-bridge (AHB) converter is one of the widely used topologies in low to medium power applications. However, when it is designed in a wide input voltage range, it operates with a low duty ratio at nominal input voltage. In addition, it has disadvantages, such as a dc offset of magnetizing current, an unbalanced average current of the diode, and a nonlinear voltage gain due to asymmetrical operation. To solve these disadvantages, an AHB converter with linear voltage gain is proposed. The proposed converter has a structure in which a capacitor is added as a voltage source to obtain a symmetrical operation by extending the commutation period. Therefore, it has a narrow range of operating duty ratio and a zero dc offset of magnetizing current. Due to the zero dc offset of magnetizing current, it has a small size transformer and improved zero-voltage switching conditions of the primary-side switches. In addition, it has a low primary rms current and a balanced average current of the diode. Consequently, the proposed converter has high efficiency under the entire load conditions. A 300–400 V input and 48 V/400 W output prototype is tested to verify the feasibility of the proposed converter.

A High-Power-Density Active-Clamp Converter with Integrated Planar Transformer

This paper proposes an active-clamp forward-flyback (ACFF) converter with an integrated planar transformer for wide-input voltage and high-output current applications, such as low-voltage direct-current (LDC) converters in electric vehicles. An integrated planar transformer that consists of a forward-flyback transformer, single primary winding, and efficient structure of secondary windings is adopted for the proposed converter, and since this transformer is implemented with a common four-layer printed circuit board (PCB) winding, a high power density and low cost of the proposed converter can be achieved. In addition, due to the low leakage inductance induced by the planar transformer, a reduced commutation period can be achieved, and it is possible to increase the switching frequency resulting in low volume of transformer. Although the integrated planar transformer has relatively high conduction loss, the active-clamp topology can significantly reduce the conduction loss on switches compared with widely used full-bridge (FB) converters because it only utilizes two switches and shows the low circulating current. As a result, the proposed converter with an integrated planar transformer has strengths in high power density and cost competitiveness without degraded efficiency, and it is a very attractive topology for LDC converters and other applications that require wide-input voltage and high-output current.

A periodic adaptive controller for the torque loop of variable speed brushless DC motor drives with non-ideal back-electromotive force

In this paper, an adaptive current controller is proposed for variable speed brushless direct current (BLDC) motor drives to minimize the output torque ripples caused by parametric and periodically varying uncertainties. Phase-to-phase non-ideal back-electromotive force (back-EMF) in BLDC motor changes periodically with respect to the shaft angle, and hence the period of these signals alters depending on the rotor frequency. To address these problems, the uncertain current dynamics of the BLDC motor is reformulated by transforming the time variable, then the periodic adaptive controller employing the instantaneous estimation values of the unknown periodic signal is developed to achieve the torque ripple reduction. The periodic estimation of the non-ideal back-EMF waveform is achieved considering the switching between conduction and commutation periods. Also, the update rules based on direct adaptation for parametric uncertainties are derived, and thus, hybrid differential-periodic adaptation rules are obtained considering the switching phenomenon. Asymptotic convergence of the phase currents to the reference values is proven by an appropriate Lyapunov–Krasovskii function depending on the angular position. Comprehensive numerical simulation studies have been successfully carried out to verify the performance and the effectiveness of the proposed controller for variable speed applications.

Commutation Torque Reduction Strategy of Brushless DC Motor Based on Single-Input Dual-Output Cuk Converter

Based on the Single-Input Dual-Output (SIDO) Cuk converter, a novel commutation torque ripple suppression strategy is proposed for a brushless DC motor (BLDCM). Two voltage scalars are constructed, according to the operating principle of SIDO Cuk converter and BLDCM, and applied to the non-commutation and commutation periods, respectively, of BLDCM; the commutation torque ripple in the full speed range is effectively reduced, and this occurs without the need to switch the control strategy according to the speed range. The inverter in the proposed strategy is controlled by the pulse amplitude modulation (PAM) during both non-commutation and commutation periods, and the voltage spike damage caused by the inverter chopping to the motor can be minimized. In addition, the multiple outputs of the SIDO Cuk converter improve the utilization of the DC power for the BLDCM control system. The experimental results verify the effectiveness of the proposed strategy.

Commutation Torque Ripple Reduction Strategy of Brushless DC Motor Drives Based on Boosting Voltage of DC-Link Small Capacitor.

Based on the brushless DC motor system with DC-link small capacitance powered by a single-phase AC power source, a boosting DC-link voltage strategy to reduce the commutation torque ripple of brushless DC motors is proposed in this paper. The control strategy utilizes the special topology of the motor system to boost the DC-link capacitor voltage in a specific zone during the non-commutation period. During the commutation period, the high voltage of the DC-link capacitor is released to meet the voltage requirement of the brushless DC motor during commutation. In order to reduce the commutation torque ripple and ensure the normal operation of the brushless DC motor, each rectifier cycle is divided into three zones according to the characteristics of the periodic change of the rectifier output voltage. Different operation modes are proposed for different zones. In DC-link capacitor boost voltage mode, the DC-link capacitor boosts the voltage to meet the voltage of the motor demand during the commutation period for achieving the purpose of reducing the commutation torque ripple. In this paper, the controller of the brushless DC motor system is designed and the experimental platform is built. The experimental results verified the correctness of the theoretical analysis and the feasibility of the proposed method.

Torque Ripple Reduction for BLDC Permanent Magnet Motor Drive Using DC-Link Voltage and Current Modulation

This paper proposes a torque ripple reduction for brushless DC (BLDC) permanent magnetic (PM) motor drive based on the DC-link voltage pulse amplitude modulation (PAM). The proposed method improves torque ripple drawback for BLDC drives at low speed. BLDC drives have the better inverter efficiency and requires low position sensing resolution. However, both freewheeling current during diode conduction and discontinuous motor phase current cause high torque ripples. In this paper, a front-end DC converter is added to improve BLDC torque ripples. Although the integration of DC converter and BLDC drive has been reported, the DC voltage regulation for the BLDC torque ripple compensation is this paper novelty. On the basis, the DC bus is modulated during diode conduction to manipulate the DC current dynamically every BLDC commutation period. In addition considering the discontinuous six-step commutation, the DC current is also regulated with the 6th-order spatial harmonic to minimize the commutation reflected torque ripple. The proposed torque ripple compensation of BLDC drive is verified by simulation for different PM motor types. According to experimental results, around 40% torque ripple reduction on a PM motor is demonstrated using the proposed BLDC drive with DC voltage modulation.

Performance Investigation of Switched Reluctance Motor Driven by Quasi-Z-Source Integrated Multiport Converter with Different Switching Algorithms

Switched reluctance machines (SRMs) have received increasing attention for their many potential uses, such as for wind power and electric vehicle (EV) drive systems. The Quasi-Z-source Integrated Multiport Converter (QZIMPC) was recently introduced to improve the reliability of the SRM driver through small capacitance values. It is not possible, however, to simultaneously energize and deenergize two SRM phases in QZIMPC. This phenomenon can significantly increase the commutation period which, in turn, degrades the performance of SRM; in addition, this causes high-voltage ripples on the converter’s capacitors. Two switching algorithms are introduced and applied in this paper, and their performance with SRM is investigated in terms of torque ripple and peak phase current. The algorithms are based on prioritizing the control command in the on-going and off-going phases to fulfill the required load torque, as well as to accelerate the commutation process where possible. This is achieved without the interference of high-level controllers, which include speed controllers and/or torque ripple minimization. Through the simulation results, a comparison between the two switching algorithms is presented to determine their potential to improve the SRM drive system’s performance.

МОДЕЛЮВАННЯ ПРОЦЕСІВ НА ОСНОВІ УСЕРЕДНЕННЯ В ПРОСТОРІ СТАНІВ У ПІДВИЩУВАЛЬНОМУ ПЕРЕТВОРЮВАЧІ З МАГНІТОПОВ’ЯЗАНИМИ ЕЛЕМЕНТАМИ

The features of the state-space average method using Lagrange's theorems for calculation of processes in the boost converter with magnetically coupled elements (with autotransformer connection of inductors) in continuous currents mode are considered. A mathematical model of the converter based on relative variables has been developed, which makes it possible to calculate processes in a wide range of parameters taking into account the degree of magnetic coupling between inductive elements, including the definition of constant and pulsating components. It is shown that to obtain a complete system of the algebraic equations as a mathematical model of converters, which provides its single solution, it is advisable to additionally use the ratio according to energy balance in reactive elements in a steady state at the operation intervals of the converter during commutation period. The boundary dependences of boost converter parameters with magnetically coupled elements between the modes of discontinuous and continuous currents are calculated. The relative characteristics of the converter have been studied, which demonstrate the influence of imperfection of the magnetic coupling in the regulation zone of the relative duration value of switching interval. Ref. 21, fig. 6.

Commutation Compensation Strategy for Brushless DC Motor Based on Terminal Voltage Reconstruction

In the sensorless brushless DC (BLDC) motor control system, the commutation signal is the key to measure the system performance. To improve the commutation accuracy, a commutation compensation strategy based on terminal voltage reconstruction is proposed. By analyzing the commutation process, the integral of ideal terminal voltage is adopted to determine the commutation error. Then considering the voltage clamping of the freewheel diode, the actual terminal voltage is analyzed in different periods. In the non-commutation period, a PWM cycle is divided into three regions, and the corresponding duration can be calculated by floating phase current, and then the equality of actual and ideal terminal voltage integrals is revealed. In the commutation period, the instantaneous value of back-electromotive force (back-EMF) at commutation point is used to construct the ideal terminal voltage and the commutation time is determined by the edge detection. In this way, the integral of terminal voltage can be calculated precisely. Then the error index is introduced and the relationship between the commutation error and the error index is presented. To eliminate the commutation error, the PI controller is adopted which outputs the compensation angle. The proposed strategy avoids the phase shift errors and the accumulation of integral errors, moreover the feasibility and effectiveness are verified by simulations and experiments under different conditions. In addition, the strategy can also be used to correct the installation error of Hall sensor.

Docupling Control of High Power Factor Inverter without Electrolytic Capacitor SRM Driver Simulation

DC bus electrolytic capacitors influential on the life of Switched reluctance motor (SRM) due to their chemical properties. For the drive system without electrolytic capacitor SRM, the power decoupling type without electrolytic capacitor scheme is studied. The parallel bidirectional Buck/Boost compensation circuit is a power decoupling circuit, a feed-forward control strategy for output voltage fluctuations of the electrolytic capacitor PFC circuit. The inverter side uses the voltage hysteresis control to stabilize the DC bus voltage. During the two-phase adjacent commutation period, the measured DC bus voltage is compared with two predetermined high and low voltages, make the DC bus voltage fluctuate within a certain range. The effectiveness of the control strategy is verified by electrical tools. The grid-side power factor is 0.958, and the grid current harmonics meet the EN61000-3-2 standard.

Analysis and evaluation of the influence of heat storage material on coke oven flue gas exothermic process

Sufficient heat storage and proper flue-gas outlet temperature were prerequisites for selective non-catalytic reduction denitrification in coke oven regenerators. This work performed an energy balance analysis on the established regenerator model to obtain a new thermal storage evaluation index ? total thermal storage temperature. Furthermore, ten cases of thermal storage parameters were set to analyze the effects of thermal effusivity and thermal diffusivity on heat storage and transfer. The transient simulation results shown that the channel shape of the lattice brick limited the uniformity of fluid-solid heat transfer and temperature distribution during the 30 minutes commutation period, and the temperature window (1100~1300 K) suitable for selective non-catalytic reduction denitration slowly moved down. The increase of thermal effusivity led to the rise of heat storage and reduction of flue-gas outlet temperature. However, the transform in thermal diffusivity did not contribute substantially to the heat storage performance. Besides, the temperature-time-height equation obtained by fitting was used for predicting the suitable location of selective non-catalytic reduction denitration temperature. The total thermal storage temperature was positively correlated with the flue-gas outlet temperature and negatively correlated with the heat storage capacity. The total thermal storage temperature evaluated the effects of material properties on heat storage and flue gas outlet temperature.

Mathematical description of commutation in multipulse rectification schemes with voltage asymmetry

Modern achievements in the field of construction of transformers and Converter technology allow creating integrated multipulse rectifier units that meet the currently increased requirements of electromagnetic compatibility between different consumers of electric energy and the network feeder. Current rectification carried out with the help of valve devices is closely related to commutation processes, the widespread use and distribution of which requires accurate consideration of the factors that determine them. One of the important questions is the degree of influence of the structural asymmetry of the transformer converter of the number of phases on the overlap angle and on the rectified voltage in the commutation zone. The paper offers a mathematical description of the steady-state process for solving a wide group of practical problems, including commutation periods for the case of converter asymmetry with an arbitrary number of ripples of the rectified voltage.