Recently, high-voltage motor direct drive systems have been put to practical use, and various multilevel PWM strategies have also been proposed. This paper describes a multilevel PWM strategy (our group calls “Carrier Phase Selection Method (CPS)") that has the lowest line voltage harmonic distortion in order to prevent the degradation of high-voltage motor winding insulations. This method takes the adverse effect of a deadtime into consideration, and it controls the shift direction of a carrier phase. Therefore, a favorable output waveform without instantaneous voltage serge is achieved even if the line voltage level changes. Moreover, the switching transitions across all switching devices are well-balanced, so the utilization of inverter unit cells is equalized. It is important factor when designing the entire system. From simulation and experimental results, it is shown that this CPS method is particularly effective to high-voltage motor direct drive systems.
This paper proposes a novel current-source multi-level inverter, which is based on a current-source half bridge topology. Multi-level inverters are effective to reduce harmonic distortion of the output voltage and the output current. However, the multi-level inverters require many gate drive power supplies to drive switching devices. The gate drive circuits using a bootstrap circuit and a pulse transformer can reduce the number of the gate drive power supplies, but a pulse width of the output PWM waveform is limited. Furthermore, high-speed power switching devices are indispensable to compose a high-frequency power converter but various problems of high frequency noise arise due to high dv/dt rate, especially in high-side switching devices. The proposed current-source multi-level inverter is composed with a common emitter topology of all switching devices. Therefore, it is possible to operate with a single power supply of gate drive circuit, which allows stabilizing a potential level of all the drive circuits. In this paper, effectiveness of the proposed circuit is verified with experimental results.
This paper deals with the expression of the high-frequency model of permanent magnet synchronous motor (PMSM) driven by a PWM inverter. The leakage current (common-mode current) flows through stray capacitance among stator windings and iron core (frame) of a synchronous motor at the switching instants of inverter transistors. A mathematical model of high-frequency model of PMSM are derived voltage and current data at the time of a PWM inverter drive based on system identification. It is verified that the proposed model can simulate oscillating current of various operating points on some motors.
A visual inspection method of textile surfaces using the translation invariant Wavelet Shrinkage is presented. The Wavelet transform, while it can be computed efficiently by the Mallat algorithm, has the translation variance problem. To deal with this problem, we use RI-Spline wavelets which are pseudo Complex wavelets consist of a pair of a symmetric bi-orthogonal spline wavelet and an anti-symmetric bi-orthogonal spline wavelet, for textile surface inspection. In our approach, we remove the regular information which consists of the textile textures and the shading effects caused by uneven lighting from the textile surfaces to be inspected, using the translation invariant Wavelet Shrinkage realized using 2D RI-Spline wavelets. The experimental results show that our inspection method is effective for detecting tiny defects as well as global defects such as dyeing unevenness.
Shaft inserting is important and frequent operation for the automatic parts assembling. Because our proposed cross PSD sensor can not detect the position error during the shaft inserting, we propose the new position sensor system by using one dimensional PSDs. This sensor can detect the position error between the center of the shaft and the center of the hole in real time. First, we show the detecting principle of this sensor and structure of the end effector with this sensor. The center of the sensor coincides with the center of the shaft. The sensor can detect the position error when the distance between the target hole and the sensor changes. So this sensor can detect position error during shaft inserting. Next, we show the configuration of the robot system with the end effector. By using this robot system, the robot can insert the shaft into the hole of the moving object with the clearance of 50μm at a velocity of 80mm/s. Though the proposed sensor system is simple structure, it is effectiveness for the shaft inserting into the hole of the moving object.
This paper describes the experimental results of a test to drive two induction motors through a VVVF inverter by 25kW class proton membrane type fuel cells (PEMFCs). The experiments are aimed at verifying the compatibility between the drive system for the railway vehicle traction and FCs. This paper describes test results of powering, powering-off procedure, and simulated slip-readhesion control test, respectively. Through the experiments, we obtained useful knowledge required in designing the fuel cell drive system.
This paper describes low-voltage and large-current DC power supplies with a high-frequency transformer coupling. Two different power supplies were developed with different configurations and operation characteristics of the two were experimentally examined in this paper. Both power supplies are simply composed of a full-bridge inverter, an amorphous-core step down transformer and a schottky diode rectifier. One power supply operates on the magnetizing frequency of 15kHz, and generates 13-V and 5000-A output. The other generates 12-V and 4000-A output, but introduces only 1-kHz magnetizing frequency due to a long overlapping period in commutation caused by large leakage inductance of its transformer. The maximum total efficiency of the former and the latter is 89.9% and 85.7%, and the total input power factor of the two is 83.5% and 92.8%, respectively. Although the output voltages and currents of the two prototypes are considerably low and large, these experimental results demonstrate excellent performance.
Diode rectifiers have been widely used for an ac-to-dc converter. One of their problems is that they include large lower-order harmonics in the input current. A 12-pulse diode rectifier is useful for reducing them but it still includes the (12m ± 1)th (m: integer) harmonics. In order to further reduce the input current harmonics a single-phase square wave auxiliary voltage supply is inserted in the middle dc bus of a 12-pulse diode rectifier. The purpose is to obtain a 12-pulse diode rectifier whose harmonic contents are equivalent to those of a 24-pulse diode rectifier. Theoretical analysis of the auxiliary supply assisted 12-pulse diode rectifier is presented and a control method of the auxiliary supply in relation to the dc load current is proposed. Effectiveness of an auxiliary supply is verified by simulation and experimental results.
On the single-phase PWM rectifier, it is well known that a power pulsation with twice the utility frequency is contained in the DC-bus. In order to smooth the DC-bus voltage, the electrolytic capacitors with large capacitance have been used. However, the large electrolytic capacitors are bulky and those lifetime becomes short on high ripple current and high temperature environment. Hence, the electrolytic capacitor is not suitable for the DC capacitor, in the case when high power density and long lifetime are expected. The authors studied two kinds of power decoupling circuits, such the authors call a capacitive storage method and an inductive storage method, those enable to transfer the ripple energy appeared on the DC capacitors into the energy in either small capacitors or additional inductors. This paper presents experimental comparison of DC power decoupling characteristics on the single-phase voltage source PWM rectifiers. Finally, the design procedure of optimum application and possibility of high power density is discussed.
The magnetic properties of the magnetic steel sheets, which are used for the magnetic cores of motors, vary with stress. This variation affects the characteristics of motors, e.g. the cogging torque of permanent magnet motors. In this paper, a novel, highly precise motor analysis method is proposed, which consists of the combination of structural analysis and electromagnetic field analysis-that is, the electromagnetic field analysis considering the stress distribution in the stator core. The cogging torque, which arises from the stress by shrink fitting of the frame to the core, is estimated using the proposed method. The validity of the proposed method has been verified by comparing the calculated results to the experimental result. Moreover, the better expression of the stress distribution in the coupled analysis is examined, and the result is that the principal stress is suitable rather than the von-Mieses stress. The reason is that the principal stress can distinguish the magnetic properties under compressive stress from the properties under tensile stress, and it can also consider the magnetic anisotropy caused by the stress.
This paper proposes a new control method of the current balancer in single-phase three-wire secondary distribution systems using the correlation function. The components of the load currents correlative to the primary side voltage waveform, which correspond to the active currents, are detected in each feeder, then the non-active and unbalanced-active components are compensated on the source side. The balanced currents with unity power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. Digital computer simulation results demonstrate that the balanced source currents with unity power factor are obtained in spite of unbalanced load currents.
In mechanical structures such as information precision machinery, the switching from a velocity servo controller to a position servo controller is often utilized. This study proposes a unified design method of both the servo controllers based on the optimization of single time-varying criterion function. This method realizes the smooth switching of the control modes. The effectiveness of the method for a positioning problem of vibration system is verified by numerical calculations.
Harmonic control scheme using genetic algorithm (GA) for single-phase multi-level rectifiers is proposed to meet harmonic current limiting standards with minimum input filter inductance. The effectiveness of the proposed scheme was verified by experiments. As the results, switching pattern which was able to decrease about 6.3% THD of the line current more than the conventional scheme and met harmonic current limiting standard was obtained.
A single-phase voltage-quadrupler rectifier with reduced input current distortion is presented. This can be operated in the switching states for pumping action to pump twice the peak supply voltage onto each of the output capacitors and for forcing the input current to follow its sinusoidal reference in the vicinity of a zero crossing of the supply. The experimental prototype, using two dual-switch power modules with IGBTs and a controller for output voltage regulation, is implemented to investigate the operation. The experimental results confirm that the input current can be waveshaped sinusoidally with a near-unity power factor.
This paper proposes a new photovoltaic generation system which effectively uses generated power of shadowed cells. In this system, a capacitor is connected to the solar cell module in parallel. The generated power of the shadowed cells is charged into the capacitor. This charged power is added to the solar cell array output power. The proposed system needs no external power supplies and is very compact and cost-effective. The energy efficiency of the system is much better than that of the bypass diode method. The experiment shows the usefulness of this system.
method → Method
Wrong:Design of a Low Vibration and Low Acoustic Noise Seek Control method for Hard Disk Drives
Right:Design of a Low Vibration and Low Acoustic Noise Seek Control Method for Hard Disk Drives
method → Method
Wrong:Fast Charging method of the Capacitor Energy for the Voltage Sag Compensator with Controlled Gradational Voltage
Right:Fast Charging Method of the Capacitor Energy for the Voltage Sag Compensator with Controlled Gradational Voltage