Low Speed Operation Research Articles

Optimized Virtual Vector Technique with Loss Minimization of Six Phase IM Under Low-Speed Operation for Electric Vehicles

Optimized Virtual Vector Technique with Loss Minimization of Six Phase IM Under Low-Speed Operation for Electric Vehicles

Contribution to the Improvement of Sensorless DTC-SVM for Three-Level NPC Inverter-fed Induction Motor Drive

This paper deals with the high performance of multi-level direct torque control (DTC) for induction machines without speed and stator flux sensors. The estimation is performed using a sliding mode observer, which is known for its robustness in high and low-speed operations, the control is based on a backstopping speed controller. This control technique was introduced years ago to circumvent the problems of sensitivity to parametric variations, it presents a high dynamic but their major problems are the variable switching frequency, the size and complexity of the switching tables, and undulations of the torque. The proposed approach is to replace switching tables with constant switching frequency control using three-level spatial vector modulation (SVM). Theoretical elements and simulation results are presented and discussed. As a result, the flux and torque ripple of three-level DTC-SVM control is greatly reduced compared to the flux and torque ripple of DTC-classic control. The advantages of the training system have been validated by the simulation results.

Performance analysis and comparison of NRZ-DQPSK optical wireless system with different filters under different weather conditions

Abstract The extensive use of wireless communication in recent years is due to the requirement of huge data transfer. Nowadays the optical wireless communication (OWC) in which the light is used for wireless connectivity is extensively used. Huge spectral resource, low bandwidth requirements and high speed of operation are the main asset of OWC. The major challenge of OWC system is the effect of different weather conditions as the air is used as a transmission medium in OWC. The variations in different weather conditions have a significant impact on the effectiveness of OWC system as they degrade the performance of OWC system. This paper compares the performance of NRZ-DQPSK OWC system with different filters (Bessel filer, Gaussian Filter and Trapezoidal filter) and the effect of different weather conditions (rain, haze and clear weather) on NRZ-DQPSK system is analyzed over different transmission distances. The comparison is done in terms of quality factor or Q-factor.

Acoustic Noise Reduction for Low-Speed Sensorless Operation of Dual Three-Phase PMSM With Random Winding Injection

This paper proposes a pseudorandom sinusoidal voltage signal with random winding injection method to improve the acoustic noise reduction performance for the dual three-phase permanent magnet synchronous motor (DTP-PMSM). Compared to the conventional pseudorandom frequency sinusoidal injection method, the proposed method achieves better noise reduction with similar performance in position estimation. Two fixed frequency signals are randomly selected as injection signals. Then, one of the two sets of windings of the DTP-PMSM is randomly chosen for injection. Due to this unique injection scheme, the injected frequency component in the response current can be reduced. Two pseudorandom numbers are generated synchronously by the digital signal system. The first random number selects two voltage signals with different frequencies. Meanwhile, one of the two sets of windings is chosen by the second random number. Thus, there is only one winding with the injection signal at a certain time. In addition, the power spectral density of the response current caused by the injected signal is analyzed. Finally, the experimental results verify the proposed method.

Dynamic Dead-Time Compensation Method Based on Switching Characteristics of the MOSFET for PMSM Drive System

In order to effectively avoid the shoot-through issue of the semiconductor device (such as the power metal-oxide-semiconductor field-effect transistor (MOSFET)) adopted in the phase leg of the motor drives, a dead-time zone should be inserted. However, the nonlinearity caused by the dead-time effect will bring about voltage/current distortion, as well as high-order harmonics, which largely degrades the performance of motor drives, especially in low-speed operations with slight loads. In this paper, a dead-time compensation method is proposed to suppress such side effects caused by dead-time zones and improve the performance of motor drives. Compared with other existing methods, the proposed method is mainly focused on the switching characteristics of the power MOSFET, which is directly relative to the compensation time in each pulse-width modulation (PWM) period. Firstly, a detailed derivation process is elaborated to reveal the relationship between compensation time and the switching performance of the MOSFET. Meanwhile, the switching process of the MOSFET is also well analyzed, which summarizes the variations in the switching time of the MOSFET with a varied load current. Then, the multipulse test (MPT) is carried out to obtain accurate values of the switching time with the varied load current in a wide range (0–80 A) and form a 2D lookup table. As a result, the compensation method can easily be realized by combining the lookup table and linear interpolation based on the phase current of the motor dynamically. Finally, the effectiveness of the proposed method is verified based on a 12 V permanent magnet synchronous machine (PMSM) drive system. According to the relative experiment results, it can be clearly observed that the time-domain waveform distortion, high-order harmonics, and total harmonic distortion (THD) value are reduced significantly with the proposed dynamic compensation method.

DSPACE Implementation of Motor Drives using Asymmetric Converter

This paper deals with the dSPACE DS1104 based implementation of closed-loop motor drive system using asymmetric converter. The mathematical model of the drive has been simulated in the MATLAB/Simulink environment to analyze the performance of the drive system. The simulated results are then validated with the experimental investigation. For experimental work, the pulse width modulation (PWM) has been implemented in MATLAB environment with Simulink real-time interface. Meanwhile, the hardware implementation consisting of dSPACE digital signal processor, voltage source inverter and generator-coupled motor. Variable speed test was performed on the loaded motor in open loop and closed-loop design to obtain speed tracking response parameter as well as speed ripple. Overall performance of developed system is satisfactory where in low-speed operation, experimental results show good speed tracking performance with ripple within 20%.

Improved Sensorless Operation of Double Inverter Fed Wound Rotor Induction Machine With Seamless Mode Transitions

The performance of a sensorless induction motor drive depends on the accuracy in estimating the flux position from the supply voltage and machine parameters. Accurate estimation of flux position at low speed operation is difficult due to the low supply frequency. In a double inverter fed induction motor drive, the low speed operation can be obtained by maintaining the relative frequency between stator and rotor supply <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">voltage</b> without reducing the individual supply frequency to a very low value. In this paper, a novel frequency profile for the stator and rotor supplies of a DFIM drive is proposed, in which the minimum supply frequency of any side inverter is around 0.5 p.u. for the whole speed range of operation. With this proposed scheme, the zero speed operation of the drive is obtained by maintaining both the stator and rotor supply frequencies as 1.0 p.u.. To achieve this, the DFIM is required to be operated as a squirrel cage induction motor for certain speed range. The control scheme for both the stator and rotor side inverters along with seamless mode transitions are also presented. In this DFIM drive, the required motor power is only 50 % of the rated load power and the total <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">volt-ampere (VA)</b> rating of the two inverters is same as that of a conventional squirrel cage induction motor drive. Experimental studies are carried out on a 45 <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">kW</b> wound rotor induction machine to validate the control scheme with the proposed frequency profile and results are presented.

A Method for Rotor Position Detection of PMSM Using Filterless Square Wave Signal Injection

Frequency signal injection is commonly utilized in sensorless control of PMSM in low-speed operation. The HF square-wave injection technique eliminates the need for filters and enhances the system’s dynamic performance. Experiments have shown that when the motor is operating at a significantly low speed, the identification error caused by this method is too large, which often leads to the motor being difficult to start or out of control. In this paper, we provide an in-depth analysis of the HF-SWIM and suggest improvements to improve the response of the system and reduce the steady-state error of the identification. These improvements include refining the high-frequency separation formulation and improving the position observer. Simulations confirm the efficacy of the proposed method.

A Reconfigurable 7T SRAM Bit Cell for High Speed, Power Saving and Low Voltage Application

The decreasing operational voltage and scaled technology node for memory designing has widened the gap between two crucial parameters for an SRAM – delay and power. As the demand for internet of things is increasing, the need for round the clock connectivity is increasing. This mandates designing a cell with a capability to switch between low power and high speed operation. Thus, this paper presents the design of dual mode operational 7T cell that can switch between single port and dual port configuration. The proposed reconfigurable cell can operate as single port or dual port cell single ended 7T cell. The reconfigurability in the cell is realized using control signals. The noise stability of the bit cell is obtained to be 333, 333, and 470 mV for read, hold, and write modes, respectively. The robustness of the cell against temperature variation, process variation and voltage variation is also analyzed. The performance variation in each parameter will not have a dramatic impact as it is within manageable limit. Its write time is 0.14 ns, while 5 ps are required for a successful read operation. The dual port configuration of the cell supports pipelining and thus operates faster than its single port configuration.

Research on path following control system of wave gliders based on maneuverability demand estimator

The wave glider (WG) with a propeller-rudder system represents a novel kind of unmanned surface vehicle that has a hybrid driving capability of wave energy and solar energy, compared to the WG with only a rudder system. The propeller-rudder system can improve the flexibility and maneuverability of the WG, especially in low-speed and nearshore operations. However, owing to the limited solar power generation and high energy consumption of the propeller, studying the precise control switching strategy of the propeller is of great significance. In this paper, a path following control system is proposed for the WG with a propeller-rudder system based on an adaptive line-of-sight algorithm (ALOS), a maneuverability demand estimator and a maneuverability controller. The maneuverability demand estimator is determined by the cross-track error and sideslip angle. And the cross-track error and sideslip angle are fused by using fuzzy mathematics to establish the mobility demand estimation model. The maneuverability demand index (MDI) intuitively expresses the urgency of the mobility demand during the path following process and is input to the maneuverability controller to control the propeller revolution. Through numerical simulations and sea trials, the effectiveness and superiority of the proposed path-following control system is verified.

Position Sensorless Control of Dual Three-Phase IPMSM Drives With High-Frequency Square-Wave Voltage Injection

Dual three-phase interior permanent-magnet synchronous motor (IPMSM) drives have received more attention by the merits of better fault-tolerant capability and lower torque ripples. To improve the reliability of the system against failures in position sensor, it is necessary to investigate the position estimation method for dual three-phase IPMSM drives. The high-frequency (HF) signals injection is utilized for position estimation in three-phase IPMSM drives during low-speed operation region. However, the torque ripples are inevitable owing to the mixing of fundamental and HF components in the same control space for three-phase IPMSM drives. In this paper, the position sensorless control method has been proposed by injecting HF square-wave voltage in the harmonic subspace for the dual three-phase IPMSM drives. Since the harmonic subspace is decoupled from the torque subspace, the torque disturbance can be mitigated well with the proposed HF signal injection based position sensorless method. Moreover, the digital filters in signal extraction and current feedback can be avoided and the signal separation process becomes easy with the proposed method. The experiments have been conducted to validate the performance of the proposed method.

Dual Random Noise Suppression Strategy for Permanent Magnet Synchronous Motor Based on Random Pulse Width Modulation and Random High-frequency Injection Method

This study proposes an innovative dual control strategy to tackle the challenge of electromagnetic noise in the sensorless low-speed operation of Permanent Magnet Synchronous Motors (PMSM). The strategy combines random Pulse Width Modulation (PWM) technology with a stochastic high-frequency injection approach. By incorporating two distinct randomized frequency switching techniques into the high-frequency injection circuit, the method integrates two-state Markov chains into both PWM technology and the random high-frequency injection method. Subsequently, a mathematical model for signal processing is developed, and extensive simulation and experimental verification are conducted. The experimental findings affirm the effectiveness of this approach in effectively mitigating electromagnetic noise while ensuring accurate location estimation within an acceptable range.

A novel capacitor voltage fluctuation suppression method for the low-frequency operating stage of MMC driven pumped storage system

The pumped storage power plant, which has the energy conversion and storage capacity, is an important solution for improving the power grid absorption ability to the unstable and fluctuating new energy from wind farms, as well as photovoltaic power stations. The modular multilevel converter (MMC) is a competitive topology for driving the pumped storage motor due to the advantages of high output power level and low output current harmonics. However, the voltages of the sub-module capacitors fluctuate largely when the MMC is operating at low-frequency stage, which would lead to an abnormal start-up process or an unstable low-speed running state of the variable speed pumped storage system. In order to suppress the low-frequency voltage fluctuation of the MMC sub-module capacitors, this paper proposes a charge channel topology including in-phase and inter-phase channel between the sub-modules for transferring the capacitor charge. Then, the reverse fluctuating fundamental component and third harmonic circulating component, as well as the synchronizing fluctuating second harmonic component, of the sub-module capacitor voltages could be counteracted, respectively. Eventually, the start-up operation performance, as well as the low-speed operation performance of the variable speed pumped storage system are enhanced greatly. The effectiveness of the proposed low-frequency capacitor voltage fluctuation suppression method is verified through simulation results.

Multi-stage Drive of Switched Reluctance Motor Based on Ring Winding Structure

A new ring winding structure can drive switched reluctance motors (SRMs). It uses a full-bridge power converter circuit to drive SRMs and is significant for developing SRMs. For this structure, this paper proposes an optimization strategy. A voltage regulator is used to boost the winding current during the motor starting phase to ensure the average starting and low-speed operation of the motor. After the motor speed reaches a specific value, the passive device replaces the voltage regulator, which ensures the stable operation of the SRM while reducing the frequency of the voltage regulator and improving the service life of the regulator. This paper simulates the optimization strategy of the ring winding structure and derives the calculation method for switching speed.

Installed Fan Noise Simulation of a Supersonic Business Aircraft

Overcoming the problem of excessive engine noise at low altitudes is a formidable task on the way to developing a supersonic passenger aircraft. The focus of this paper is on the fan noise shielding during take-off, investigated as part of the DLR project ELTON SST (estimation of landing and take-off noise of supersonic transport) for an in-house aircraft design. The supersonic inlet is required to provide the proper quantity and uniformity of air to the engine over a wider range of flight conditions than the subsonic inlet. For passenger aircraft, the noise problem influences engine integration and placement, and the new generation of supersonic transport would require innovative engineering solutions in order to come up with an efficient low-noise design. Potential solutions are evaluated using DLR tools capable of accurate source generation and noise propagation to the far-field. For low-speed aircraft operation, the method of choice is a strongly coupled volume-resolving discontinuous Galerkin (DG) and fast multipole boundary element method (FM-BEM) which is applied due to a large disparity between the Mach numbers on the interior and exterior of the inlet. The method is used for obtaining the acoustic signature of the full-scale model at realistic flight points, including the application of the programmed lapse rate (PLR), which involves simulations at higher pitch angles than for the reference flight path. The results show that the proposed method is highly suitable for obtaining accurate noise footprints during the low-speed phase and could be used to assist with certification procedures of future supersonic aircraft.

Pump-Controlled AGC Micro-Displacement Position Control of Lithium Battery Pole Strip Mill Based on Friction Model

Electrode roll-forming refers to rolling a battery electrode into a preset thickness through the electro-hydraulic servo pump-controlled hydraulic roll gap thickness automatic control system (known to as pump-controlled AGC). Compared with the motor servo system, the friction problem of the electro-hydraulic servo system is more serious and the friction problem of the actuator itself is very prominent. Moreover, low-speed performance is one of its core indicators, the friction phenomenon is the most abundant during the low-speed stage and the impact on the servo system is also the most obvious. Therefore, for high-performance electro-hydraulic servo control, friction compensation is not only unavoidable, but also a very difficult problem. Aiming to influence the friction on the position control of the pump-controlled system of a lithium battery pole strip mill, the rolling mechanism and process procedure under micro-displacement position control based on the friction model were studied and compared from the perspective of considering friction factors, and a friction compensation controller based on the LuGre model was designed. The control precision of a pump-controlled AGC system was improved through combination with an adaptive robust controller. Because of the diversity of unmeasurable states of the system, a dual observer was designed, and the known model of the system was added to the observer. In the final comparative experiment, the steady-state accuracy of the friction adaptive robust compensation controller system based on the LuGre model reached ±0.3 μm, which is superior to the fuzzy IMC compensation and traditional PID control strategies.

Evaluation of Wear Models for the Wear Calculation of Journal Bearings for Planetary Gears in Wind Turbines

To increase the power density of the electromechanical drive train of wind turbines, journal bearings can be used as planetary gear bearings instead of rolling bearings. This technological change presents new challenges. For example, wind turbine drive systems are subject to dynamic and low-speed operating conditions, which can lead to accelerated abrasive wear of the journal bearings. In addition, oil supply failure or peak loads due to wind gusts and grid and power converter faults could potentially result in catastrophic failure due to adhesive wear in a very short time. Such operating characteristics are, therefore, critical regarding the journal bearing wear lifetime and must be considered in the design. The successful implementation of journal bearings in wind turbines depends on a reliable estimation of adhesive and abrasive wear. In this paper, five different models for the wear calculation of journal bearings are evaluated regarding their suitability for the wear calculation of planetary gear bearings in wind turbines. For this purpose, the following evaluation criteria were defined: parameter uncertainty, parametrization effort, in particular number of parameters, parameterization method, load case dependency of parameters and calculation effort. In order to be able to evaluate the wear models, the wear models are numerically implemented, and the wear of a test journal bearing is exemplarily calculated under load conditions, which are comparable to load conditions in a wind turbine. Relevant influences from the wind turbine system, such as lubricant, material and manufacturing-dependent surface influences, such as roughness and hardness, are considered. The wear models are evaluated with respect to their fulfillment of the defined criteria. The resulting evaluation allows the selection of a wear model that can be used to calculate the wear of planetary gear journal bearings in wind turbines, considering the available input variables.

基于 Arduino 的小型蔬菜播种机远程控制系统设计与性能试验

Facilities greenhouses are relatively narrow and airtight, and the machine operation turns frequently. The existing vegetable seeders is supported by manual hand, and the straightness of operation is poor, Turning around is time-consuming and laborious. This paper designs a remote control system of small vegetable seeder based on Arduino microcontroller, the Arduino single-chip microcomputer remote control technology, multi-motor synchronous drive technology, differential-electric push rod combined with lifting and steering control and other methods are adopted, Through remote control, the forward, speed regulation, lifting of the whole machine and field line change and steering of the seeder during vegetable sowing are realized. The differential steering model and brushless motor speed control model are established, and the android human-computer interaction APP is designed to realize the remote precise control of vegetable seeder. The performance test of the accuracy of the control system was carried out with the accuracy and steering accuracy of the seeder. The results showed that : under the condition of medium speed and medium and low speed operation, the seeding level of vegetable seeder is the most stable and reliable, the speed deviation rate of the seeder is 1.59 %, after starting the drive motor for 2s, the actual speed is close to the target speed, differential steering is relatively accurate, the qualified rate of steering is more than 89.8 %, the synchronous speed error of the lifting mechanism tends to be stable.This study can provide reference for the development of intelligent equipment for facility agriculture.

An Innovative H-Type Flux Switching Permanent Magnet Linear Generator for Thrust Force Enhancement

In this paper, two H-type flux switching permanent magnet linear generators with outer-translator and inner-translator configurations are discussed and compared to a more conventional flux switching topology. The stators consist of H-Type modules housing circumferential coils and are surrounded by two annular permanent magnets. In conventional flux switching machines, the windings are orientated perpendicular to the direction of motion and the conductors twist around the magnets. In H-type topologies, the orientation of the windings is in the same plain as the magnets and parallel to the direction of motion, resulting in an increase in flux linkage. The proposed topologies are designed for a low operating speed and a large magnetic gap, as found in wave energy converters. All topologies are optimized using the Taguchi optimization approach with the goals of reducing force ripple and increasing the average thrust force and efficiency. The 2D finite element method (FEM) is used in the optimization stage to calculate the optimized parameters of the presented generators, after which the optimized structures are simulated using 3D FEM, and the results are extracted. The results of the optimization show that the H-type topologies deliver a 20% higher shear stress whilst offering an easier to assemble structure.

An Application of the Functional Resonance Analysis Method (FRAM) to Risk Assessment of Low-Speed Helicopter Operations to Avoid the Aerodynamic Phenomenon Known as Vortex Ring State

An Application of the Functional Resonance Analysis Method (FRAM) to Risk Assessment of Low-Speed Helicopter Operations to Avoid the Aerodynamic Phenomenon Known as Vortex Ring State