The field of electric drives in general, and medium-voltage high-power drives in particular, has recently experienced considerable progress. Numerous interesting developments have been reported in the literature. Various reliable, efficient, and cost-effective medium voltage drive topologies, handling high powers up to 120MW, have been proposed in the literature. This paper provides a detailed overview of the current state-of-the-art in medium-voltage high-power drives and the challenges facing them.
This paper proposes a power supply circuit for gate drive units (GDUs) that uses a one-turn transformer, which gives advantages in terms of cost and loss reduction. The structure of the proposed one-turn transformer consists of a primary winding in which the number of turns is one and a secondary winding in which there are multiple number of turns. The proposed one-turn transformer is connected in series with a switching device of the main circuit in order to obtain power for the GDUs. The proposed power supply circuit can be applied to all types of main circuit topologies such as a multilevel converter topology or matrix converters, in addition to a conventional six-arm inverter. In this paper, the design method of the one-turn transformer and its characteristics are described based on an equivalent circuit and fundamental experimental results with a step-down chopper. Besides, the proposed power supply circuit for GDUs is tested in a two-level three-phase inverter. Secondly, the obtained power for GDUs from the proposed one-turn transformer with three connection points is investigated by harmonics analysis from the viewpoint of core size and other parameters. Finally, experimental results confirm that the GDU in the two-level three-phase inverter with switching frequencies of 12.5kHz and 16kHz is operated by the proposed self-supplying gate power supply circuit without an external power source.
This paper discusses harmonic current compensation of the constant dc-capacitor voltage-control (CDCVC)-based strategy for smart charger for electric vehicles (EVs) in single-phase three-wire distribution feeders (SPTWDFs) under distorted load current conditions. The basic principle of the CDCVC-based harmonics compensation strategy under distorted load current conditions is discussed in detail. The instantaneous power flowing into the three-leg pulse-width modulated (PWM) rectifier, which acts as a smart charger, shows that the CDCVC-based strategy achieves balanced and sinusoidal source currents with a unity power factor (PF). The CDCVC-based harmonics compensation strategy does not require any calculation blocks of fundamental reactive, unbalanced active, and harmonic currents. Thus, the authors propose a simplified algorithm to compensate for reactive, unbalanced active, and harmonic currents. Simulation and experimental results demonstrate that balanced and sinusoidal source currents with a unity PF in SPTWDFs are obtained on the secondary side of the pole-mounted distribution transformer during both the battery-charging and battery-discharging operations in EVs, compensating the reactive, unbalanced active, and harmonic currents.
This paper provides a general sensorless method to control the position of a linear actuator. After a review of the solutions used so far, this new method is applied to identify keys passing through a linear actuator used in an industrial textile machine. The presented method describes how to find out the position of the key using two cascading discrete Kalman filters, the first for filtering the speed and the second for filtering the impedance measurement in other to retrieve the position. To speed-up the method and due to the thickness difference from one textile machine to another, an actuator model, to evaluate impedance in function of the position, is obtained by using parameter identification. Kalman's filter parameters are optimized to minimize the time necessary to learn the speed operation. Finally, we focus on the temporal evolution of Kalman Filters parameters on the learning process.
The output voltage error compensation for a pulse-width modulated (PWM) voltage source inverter (VSI) is essential for a wide range of semiconductor power conversion applications in order to suppress detrimental output voltage and current distortions. A conventional software-based compensation method added the error voltage to the output voltage reference in a feed-forward manner, and was executed every PWM carrier period. However, the compensation value was the average output voltage error in the carrier period, thus the time delay of the pulse modulated output voltage caused by each switching was not compensated, which also reduced the performance of the synchronous sampling. This paper proposes output voltage compensation for every half of the carrier period, which enables the compensation for the error at each of the switching. In addition, the instantaneous current prediction method has been proposed, which is necessary for the proposed compensation method. The proposed compensation method is more effective than conventional ones based on the average error voltage, especially when the current ripple is large and the current is around 0A. The proposed method has been confirmed through the experimental setups and it was proved that the low-order current distortions were clearly reduced compared with the conventional compensation method.
DC-DC converters in power supplies should exhibit both high efficiency and power density. Losses in these converters can be attributed to losses in its transformer and circuit. To improve the efficiency of a switching power supply, it is necessary to reduce losses in the transformer. As the use of SiC and GaN semiconductors is becoming more widespread, it is even more important to find a way to reduce the losses in a MHz drive transformer. The losses in these transformers are primarily due to copper and iron losses. These losses can be reduced by changing the winding wire and core of a transformer. In this paper, the authors propose fabricating the winding wire and core magnetic composite materials. These magnetic composite materials comprise microscale magnetic powders and binders. The authors propose using a magnetocoated wire, which is a winding copper wire that has had magnetic composite materials plated onto it. The iron-based metal composite core is made using magnetic composite materials, which can reduce eddy current losses that a core experiences during MHz driving. This paper describes our results for an LLC resonant converter using a magnetocoated wire and an iron-based metal composite core.
In recent years, inductors and transformers have become increasingly important factors in power electronics circuit design, not only because their volume is now a dominant aspect in these circuits, but also because their losses sometimes cannot be neglected. Therefore, there is much interest in the development of simple and quick methods capable of calculating the losses of magnetic components with high accuracy, and thus support the design of magnetic components. However, calculating the iron losses of gapped inductors requires much measurement data or/and complex electromagnetic simulations. This paper proposes a novel iron loss calculation method for gapped inductors, based on the loss-map method. An advantage of the proposed method is that the iron losses of gapped inductors can be calculated accurately without the need for complex simulations and with less measurement effort than the existing approaches. The proposed method is experimentally verified using gapped inductors with both MnZn ferrite and iron dust cores.
In recent years, wireless power transfer technology has received considerable attention because of its wide range of applications. Most of the literature focuses on the resistance load or constant voltage load, and the constant power load is almost never considered. The open loop transfer function of a constant power load is unstable, and therefore closed loop stabilization is required. Furthermore, communication between the two sides is often used but it may not be available. In order to stabilize the load voltage without resorting to coordination with the primary side and discontinuous operation causing big voltage transients, this paper proposes a control strategy for only the secondary side using a single converter. It is based on the combination of synchronous rectification and symmetric phase shift, without communication with the primary side. While the primary side is not manipulated, the AC/DC converter regulates the amplitude of the secondary coil voltage and stabilizes the constant power load voltage on the DC side via a simple PI control. In this paper, the control concept, design and stability analysis are provided. The proposed control is verified through experimental results in both static and dynamic scenarios, achieving a controller that is simple to design and has smooth waveforms.
Force/torque control is attracting considerable attention for the realization of compliant motion in mechatronic systems such as industrial robots and human-support robots. They have transmission mechanisms such as gear reducers, which introduce resonance in the low frequency range and nonlinearity by backlash. To achieve high precision even with transmission mechanisms, the reduced cost of high-resolution encoders has increased the number of devices with load-side (gear-output-side) encoders in industry. Therefore, this study proposes a precise joint torque control method with backlash compensation by using load-side encoder information. The effective use of the load-side encoder information enables the proposed method to compensate the fast backlash effect in a feed forward manner. Moreover, based on the experimental analyses, the novel backlash compensation model is proposed to solve the problems caused by the conventional backlash compensation model. Simulation and experimental results demonstrate the advantages of the proposed method.
Recently, research on gene for different biological substances has attracted significant attention. Protein extraction is the first step to get the information about DNA, RNA, etc. Protein is also essential in manufacturing medicine, food and various types of biological reagents. In order to extract protein from the cell of a biological substance, cell fractionation is the first step to be performed. There are several processes for cell fractionation, such as, enzymatic digestion, cell lysis, ultrasonic fragmentation, freeze-thaw, etc. However, these methods are mostly expensive and sometimes, different types of reagents may need to be added. Therefore, a low-cost and easier method is required for cell fractionation. We have developed a methodology by using ferrite particles, whose motion is controlled using an AC voltage source with low frequency. The system works like the ball mill method, where the ferrite particles act similar to ceramic balls. The motion of ferrite particles is controlled by the magnetic flux produced by an electromagnet aligned vertically to the treatment container. As ferrite particles are not toxic to biological substances, they are kept together under AC magnetic flux. The ferrite particles collide with cells and thus cell fractionation occurs, leading to protein extraction. We have measured the protein as well as nucleic acid concentration of the treated biological substances and observed increase in protein concentration after the treatment. Thus, our method can peovide a simple and easy technique for cell fractionation in the field of protein analysis.
In this paper, a current control method for discontinuous current mode (DCM) is proposed for a three-phase grid-tied inverter to minimize inductors without worsening current total harmonic distortion (THD). In conventional continuous current mode (CCM) control, current THD increases as an inductor value is reduced because a zero-clamping phenomenon occurs due to dead-time. In the proposed DCM current control, a zero-current interval is intentionally controlled and a dead-time-induced error voltage is simply compensated with conventional dead-time feedforward compensation. The validation of the control method is confirmed by simulations and a 700-W prototype. Compared to conventional CCM current control, the current THD is reduced by 97.6% with the proposed DCM current control, whereas the inductor volume is reduced by 70%. In the experiments, the current THD is maintained below 5% over load range from 0.3p.u. to 1.0p.u. even when the inductance impedance is reduced to 0.5% of the inverter total impedance.
A dual active bridge (DAB) dc-dc converter with the conventional combined pulse-width modulation (CPWM) performs hard-switching operation in the low power range when the input or output voltage varies. In this paper, a novel modulation strategy named tunable dual pulse-width modulation (TDPWM) is proposed to modify Interval 1 of CPWM, which enables the DAB converter to perform complete zero voltage switching (ZVS) operation, only in the low power range, by adding two tunable parameters. In order to tune the two parameters accurately, the dead time effect and the parasitic components are considered in the complete ZVS analysis. In addition, the TDPWM strategy combines the three independent parameters into two tunable parameters and the fundamental phase which, enables bidirectional power transfer. The efficiencies of the DPWM and TDPWM operations are compared under various voltage variations using a prototype. The experimental results demonstrated that the complete ZVS operation with TDPWM achieved higher efficiency than that with DPWM when the input/output voltage was varied.
This paper proposes an island-mode voltage control method using an open-loop control that applies a high-gain disturbance observer (DOB) for a single-phase inverter with a low-capacitance output filter. The output voltage is distorted with low capacitance obtained from the conventional method that consists of a PID regulator for an automatic voltage regulator and a PI regulator for an automatic current regulator. To compensate for the output voltage distortion, the high-gain DOB for the output voltage is applied for open-loop-based voltage control. DOB is implemented into a field-programmable gate array with high-speed sampling. In the LC filter of a 1-kW prototype, the impedance of the inductor is minimized to 1.0% of the normalized inverter impedance, whereas the admittance of the capacitor is reduced to 0.25% of the normalized inverter admittance. Using the proposed method, the inverter output voltage total harmonic distortion is reduced by 82.4% even with the diode rectifier load compared to conventional voltage control, whereas the constant output voltage is achieved regardless of load conditions.
This paper deals with harmonics compensation with reactive power control of the previously proposed constant dc-capacitor voltage-control (CDCVC)-based strategy in a smart charger (SC) for electric vehicles (EVs) in single-phase three-wire distribution feeders (SPTWDFs) under distorted load current conditions. For the control algorithm of SC, only the CDCVC block, which is typically used in grid-connected inverters including active power line conditioners, is used. No calculation blocks of the load-side fundamental active-reactive currents and harmonic currents are required. Thus, the authors offer a simplified harmonics compensation strategy with reactive power control for the SC in SPTWDFs. The basic principle of the CDCVC-based strategy is discussed in detail. Simulation and experimental results demonstrate that during battery-charging and battery-discharging operations in EVs, balanced and sinusoidal source currents with a predefined power factor of 0.9 on the source side, which is an acceptable value for Japanese domestic consumers, are achieved on the secondary side of the pole-mounted distribution transformer using the CDCVC-based algorithm. Simulation and experimental results also demonstrate that controlling the reactive power on the source side can reduce the capacity of the SC.
Co-simulation for a hard disk drive (HDD) servo system and its microcontroller control system was developed to analyze computational aspects of the control system such as memory use and calculation load on processors. The microcontroller was modeled with its instruction set simulator that executed the binary codes of control commands. The model also incorporated the peripheral functions of timer units, an interrupt controller, an analog-to-digital converter, and so forth. The plant model of the HDD mechanism and its control algorithms were adopted from a study on HDD servo controls. The microcontroller and HDD models communicated with each other periodically to realize co-simulation. The control algorithms, which were originally written in Matlab®, were converted to C codes and eventually to binary codes by an automated code generation tool to eliminate manual programming and to guarantee fair comparison. The proposed co-simulation method compared different control algorithms, as well as different microcontrollers, for selection. The accuracy of the co-simulation was investigated, and the potential use of co-simulation approach was discussed. A synchronization adaptor was proposed to improve the timing accuracy of the control system simulation.
In this study, the absorption boundary conditions (ABCs) in electromagnetic field numerical analysis were investigated to improve the estimation accuracy of the magnetic coupling coefficient (k) for wireless power transfer (WPT). When using Berenger's perfectly matched layer (B-PML), the estimation accuracy of the k value was higher than that obtained using Mur's ABC. However, in the low-frequency band, at around 400Hz, the magnetic field was not sufficiently attenuated in the absorption layer. There was also a problem with numerical stability. To solve these problems, we introduce the convolutional perfectly matched layer (C-PML). In this study, we propose a simple Debye distribution function as the matrix coefficient of the stretch coordinate metric. As a result, it was possible to evolve from B-PML to C-PML simply by adding a proportional coefficient γ. With the introduction of C-PML, the magnetic field was sufficiently attenuated in the absorption layer, and the numerical stability dramatically improved. C-PML is thus useful for low-frequency WPT simulation.
This paper reports on two methods that achieve a reduction in the power consumption of a stepping motor for driving the hands of wristwatches. The first of these methods involves the enhancement of the magnetic bonding between the rotor, comprised of a dipolar permanent magnet, and the stator. The gap between the rotor and the stator has been narrowed for this purpose. The second of these methods involves suppressing the increase of the detent torque, which occurs in association with the former method. The portion of the stator that generates this detent torque has been thinned on both sides to adjust the thickness for the same reason.
In a vehicle, radiational noise generated by the common-mode current in an inverter system is the cause of electromagnetic issues affecting in-vehicle radio antennas. This paper proposes a new method “Z-matched ACC” for suppressing the common-mode current at the AM band. Using this method, the exciting current of the common-mode transformer, which reduces the common-mode current suppression effect higher than 100kHz in conventional voltage-cancellation ACC, flows into a Z-matched circuit rather than into a motor parasitic capacitor. Therefore, the Z-matched ACC can suppress the common-mode current at the AM band. The suppression effect of the Z-matched ACC is superior to the conventional ACC from 100kHz to 10MHz. In addition, the Z-matched ACC can reduce the size of the common-mode transformer compared to the conventional ACC by reducing the ET product applied to the common-mode transformer.