This paper proposes a sensorless vector control using a simplified the DC-link current sampling. The motor current phase and amplitude are estimated from two different phases of the three-phase AC current in the conventional method. The timer function of a microcomputer for A/D conversion is necessary to sample two different phases current from the DC-link. The range of available microcomputers is restricted, which increases the cost of the motor drive system. The current estimation method without the timer function is proposed for a low-cost microcomputer in this paper. One phase of the three phase AC current is repeatedly sampled at regular intervals. The motor current phase and amplitude are estimated from two same phase current sampled at different timing. Because the accuracy of the proposed current estimation method depends on the sampling timing, a fluctuating error occurs in the case of a low sampling rate and a low carrier frequency. The fluctuating error is removed by using the compensation coefficient that is calculated online based on the sampling timing. The obtained simulation and experimental results confirm the effectiveness of the proposed method.
This paper describes the non-linear characteristic of output voltage and a method for determining carrier frequency. First, the linear region of the output voltage is determined by calculating the upper limit of the modulation factor (ali) for which the gate signal does not disappear. Second, the carrier frequency, which falls below ali, is determined by calculating the modulation factor that generates the rated output voltage and by calculating the compensation voltage that reduces the dead-time and impedance voltage. Third, the accuracy of the proposed design method is experimentally confirmed.
This paper investigates tracking and linkage control methods between distributed generations and power system networks based on passivity characteristics. The proposed tracking control method focuses on the energy stored in inductors and capacitors in the operating system. In addition, the proposed linkage control method maintains the phase synchronization of distributed generations. It is numerically and experimentally clarified that the proposed control methods achieve tracking targeted states and stable linkage with the power system networks at an abrupt voltage sag.
In recent years, induction heating (IH) cookers using a high-frequency (HF) inverter for home use have become increasingly popular because of their cleanliness, high efficiency, safety, and so on. With regard to the domestic consumer markets, effective applicability to a variety of pan materials such as low resistivity materials (aluminum and copper) and high-resistivity materials (iron and magnetic stainless steel) is one of the important issues. In this paper, a time-sharing HF inverter for IH cooking appliances that enables doubling of the output frequency of the switching operation is proposed. The proposed HF resonant inverter is able to reduce switching losses by the frequency doubler and the soft-switching operation. Furthermore, the current rating of the switching power devices is reduced because of the parallel-connected circuit configuration. The basic principle of the proposed time-sharing HF inverter is discussed in detail. The performance and effectiveness of the proposed time-sharing HF inverter are confirmed by experimental point of view.
A train scheduling method to minimize the trip time of passengers under restricted electrical energy is investigated in this paper. This method assumes that the consumed electrical energy of one railway artery, all the vehicles of which are local trains, is restricted to a certain value. The endogenous variables of this method are the running time for each interstation, the consumed energy for each interstation, and the number of vehicles. The solution depends on the Kuhn-Tucker theorem on the constraints of both the number of vehicles and the total amount of consumed energy per unit time. This method enables us to determine the running time for each interstation and the number of vehicles according to the solution, which gives priority to small changes in the running time in interstations over decreasing the number of vehicles. Numerical examples verify the effect of reducing the time increment caused by the restriction in some artery without reducing the number of vehicles. The results also imply that the effect on passengers of each energy-saving method differs for every traffic artery.
Contactless power transfer systems with primary series and secondary parallel resonant capacitors (SP topology) are useful for electric vehicle charging. However, SP topology is not suitable for the bidirectional power transfer. In this paper, we propose a new bidirectional contactless power transfer system with a secondary series reactor added to the SP topology's circuit (SPL topology). The experimental results of 3kW bidirectional power transfer are shown to verify the effectiveness of the proposed system. The transformer efficiencies of the SPL topology are 94.4% (G2V) and 94.8% (V2G) against 95.4% of the SP topology at a 70mm gap. Both efficiencies of the SPL topology are consistently high, regardless of the change in the gap length and misalignment.
This paper proposes simulation methods based on the forward Euler method that are suitable for real-time simulators. However, real-time simulation using the forward Euler method has the following problems: A simulation error caused by a time step limitation and a delay in the simulated waveforms. The authors have proposed a simulation method suitable for real-time simulators, but the physical meaning of the state variables is diluted by diagonalization of the system matrix. This paper proposes a simulation method to obtain the same characteristics as the previous method, without diagonalization. Off-line and real-time simulation results demonstrate the validity and usefulness of the proposed simulation method.
This paper proposes a restart control method for position sensorless PMSM drive systems without a potential transformer for railway vehicle traction. This method can estimate the initial rotor speed and position at coasting condition over the entire speed range. Moreover, the method can also be used when the back-EMF voltage is higher than the inverter DC link voltage. The proposed method is verified by experiments using 200-kW PMSM.
This paper presents a practical compensation method for parameter variations of galvano scanners in laser drilling machines. In the galvano scanner, plant parameters, such as torque constant of motor, mechanical resonant frequencies, and viscous friction in mechanism, vary according to temperature rise and/or age-related deterioration. As a result, the positioning performance deteriorates owing to variations from the nominal condition. In this study, therefore, a practical estimation and compensation method for the variations is proposed in order to improve the settling performance, where fluctuations in settling waveforms are comparatively analyzed by a precise positioning simulator. Based on the analyses, the fluctuations are approximately expressed by simultaneous equations, while the parameters are identified by solving the equations using a multiple regression analysis. Then, a feedforward controller is redesigned with the identified parameters. The proposed compensation approach has been verified by numerical simulations and experiments using a positioning device for actual galvano scanners.
This study analyzes the performance of reproducibility and operationality in bilateral teleoperation under time delay. Acceleration-based bilateral control (ABC) is a hybrid of position control and force control in orthogonally- crossed two-modal space. This study analyzes the effect of each modal space on reproducibility and operationality. Based on this analysis, this paper proposes a novel four-channel (4ch) ABC design and the most appropriate controller gain values of the position and force controllers for balancing reproducibility and operationality taking the time delay effect into account. The validity of proposed system is demonstrated experimentally.
In this study, we investigate the machine parameters and the torque of interior permanent magnet motors by considering dq-axis interference caused by magnetic saturation of rotor cores. First, the total flux in the motor is decomposed into those produced by armature currents and permanent magnets by using finite element method. Then, the torque is decomposed into four components by using the machine parameters involving the effect of dq-axis interference. The validity of the calculated results is confirmed by experiments. The effect of the dq-axis interfrence on the torque is clarified. Finally, an appropriate magnet configuration is discussed in order to reduce the effect of dq-axis interference.
When an operational disturbance occurs, the timetable is rescheduled to recover ordinary transportation services. It is difficult for train operating companies to make appropriate rescheduling plans, because they have to predict the passenger flow in detail, which is a complicated undertaking, and consider their convenience under timetable disruption. In this study, we first reestablish train operation and passenger flow simulator to estimate under the condition of timetable disruption. With a modified simulator, we can estimate passengers' detour behavior, or express differences in behavior with or without information about rescheduling. We also propose an evaluation method for rescheduling alternatives with the estimated transportation services under disruption. We applied the modified simulator to an actual commuter line in Japan, and compared the two rescheduling plans under an imaginary disruption scenario. From the results, we conclude that the proposed method is useful for evaluating rescheduling alternatives.
This paper discusses the increase in thrust with grain-oriented electrical steel sheets (GO) in plunger-type electromagnetic actuators. In these actuators, GO-laminated cores generate reluctance thrusts due to magnetic anisotropy energies in addition to conventional reluctances which are induced by the form anisotropies of the cores. Therefore, the maximum thrusts, which are induced at a displacement of about the core tooth width, increase by using GO-laminated core. The thrusts of GO cores are approximately 10% larger with high exciting current than those of non-oriented electrical steel sheet cores, and consequently may reduce copper losses by about 40% and iron losses by about 60%.