This paper proposes a construction method for battery systems that are widely used in industries. The battery system uses a building block structure combined with a battery module, whose capacity is less than 1kWh. To manage the building block structured system, we propose a hierarchical structured management method. In each hierarchy, the voltage and temperature of the battery are monitored, and the information necessary for calculating charge states and detecting faults are sent to the upper hierarchy for the state management of the lower hierarchy. Furthermore, to ensure the safety during maintenance activities, we provide a guidance for understanding the insulation structure for the battery module, and develop a ground fault detection method that detects a decline in the insulation performance by using a rising method. For the experiment we use a 30kWh trial manufacture battery system combined with the hierarchical management method. We verify that charge states and faults are detected in the battery of the system, and confirm that the system can be charged and discharged safely.
The objective of this study is to reduce rear-end vehicle collisions caused by human errors. In order to achieve this objective, we studied a technique to detect preceding vehicles with image processing using a monocular in-vehicle camera and a computer. As an image characteristic for vehicle detection, we adopt the shadow under the vehicle. However, the detection of preceding vehicles using only the shadow has low reliability. In this paper, we propose a technique of identifying the region over the shadow as either vehicle or non-vehicle by machine learning. Experimental results show that the proposed method is more effective than the method using only the shadow.
In this paper, a driving method for an interior permanent magnet (IPM) motor is proposed; this method increases the system efficiency in the constant power region. In the driving method, the PWM inverter with a voltage booster system allows the use of both flux weakening control (FWC) and DC link voltage control (DVC) to drive an IPM motor at high speed. The authors investigate how a combination of FWC and DVC is suitable for the system. First, a simulation model is introduced. This model allows the calculation of the system efficiency and each part of the system losses in the voltage booster, inverter, and IPM motor. Furthermore, the system efficiency is calculated using the simulation model, and the simulation results are discussed when the ratio between the FWC and the DVC is changed. The IPM motor drive method is expected to help achievement of high efficiency by adjusting the ratio between the two control methods in the constant power region.
Recently, a multilevel inverter has been applied as the DC/AC converter of the UPS and PCS. A harmonic reduction, size reduction, and higher efficiency are the advantages of a multilevel inverter. In this study, we focus on the ratio of the input voltage of the single-phase NPC inverter. It is possible to output a voltage if this ratio is the same as that in the 5-level mode or if this ratio is different from that in the 7-level mode. However, the areas that output 0V during the dead time period deteriorate the quality of the generated current waveform in the 7-level mode. We propose the insertion of a new dead time (PDL: Partial Dead-time Less) that is suitable for the 7-level mode to solve this problem. In this paper, we demonstrate the validity of the PDL with an experiment.
Inductive Power Transfer systems (IPT system) for moving Electrical Vehicles (EV) are often discussed. However an IPT system for moving railway vehicles has not been sufficiently examined. In order to employ the IPT system for railway vehicles, this paper examines the characteristics of railway IPT systems, such as efficiency, temperature rise, and durability. Because the required characteristics of the IPT system for railway are different from those of EV, one example of a railway IPT system is proposed, and the verification items for practical use are examined. Moreover, we manufactured test equipment that can imitate the field environment in order to verify these items before practical use in the field. The test procedure and test results demonstrate the possibility of practical use of a railway IPT system.
This paper discusses the performance of compensation methods for dead-time voltage error in voltage-source grid-connection PWM converters. The theoretical analysis in this paper reveals the relationship between the voltage error and the current ripples through the converter. The analytical results imply that the voltage error is strongly affected by the amplitude of the current ripples as well as the source power factor. This paper proposes a new compensation method which makes it possible to use two lookup tables to reduce the calculation time in the controller. The compensation characteristics are compared by using a 200-V 5-kW three-phase grid-connection converter. As a result, conventional approximation-based compensation methods exhibit an acceptable performance in a restricted power-factor operation range. In contrast, the turn-off transition-based compensation method and the proposed method have a good compensation performance all over the power-factor.
This paper presents a new type of magnet-free motor that has concentrated stator windings and rotor coils with a pair of diodes. The most important feature of this motor is that currents in the rotor coils can be generated by utilizing the changes in the spatial second harmonic of the magnetic fields due to the concentrated stator windings, which normally increase motor losses. A prototype of the motor was designed and fabricated, and its basic performance was evaluated. First, using simplified analytic models, we explain the mechanism of inducing currents in the rotor coils by the changes in the spatial second harmonic of the magnetic fields. Second, we compare the torque performance of the proposed motor and that of other types of motors including a magnet motor through FE analyses. The analyzed data show that the proposed motor can possess greater torque/volume ratio than that of the other motors. Finally, using the measured data, we validate the mechanism of inducing currents in the rotor coils, and examine the torque and power characteristics of the motor.
This paper proposes a bi-directional isolated DC/DC converter for battery charger and discharger of electric vehicles controlled by a new phase-shift topology. The proposed DC/DC converter consists of two full-bridge inverters, an isolated transformer, and boost reactors. The converter provides bi-directional transmission, buck-boost conversion and zero-voltage switching, adjusting the phase-shift of two full bridge inverters continuously. A 400V-3.5kW experimental system provides stable bi-directional buck-boost conversion and seamless transition between charging and discharging modes. A maximum efficiency of 93.3% can be achieved for this experimental system.
This paper proposes an FRT (Fault ride through) method for a matrix converter in a grid-connected system to control the grid reactive current and the generator torque during a three-phase short voltage sag. In the proposed method, the control period of the system is divided into three modes. In the first mode, all switches are turned off, and in the second mode, a zero vector is obtained at the output of the matrix converter. By using these two modes along with a snubber circuit in the matrix converter, the generator torque is controlled during the three-phase voltage sag. Further, in the third mode a non-zero vector is selected to connect the generator to the grid for providing the reactive current to the grid. In addition, the paper proposes a feedback control to obtain a stable ride through operation. From the experimental results, it is confirmed that grid reactive current of 0.86p. u. and generator torque of 1.07 p.u. are achieved by the proposed FRT method during the three-phase voltage sag.
Fuel Cell (FC) power should be minimized because of its expensive cost, when it is applied to hybrid powered railway vehicles with Electric Double Layer Capacitors (EDLCs). This paper proposes a method to determine FC output power and EDLC capacitance in order to minimize the hybrid system, considering the time delay of FC output power and energy losses for running. This paper also verifies the energy management strategy for EDLCs with FC output power and for power flow controls of DC/DC chopper by a 1kW class experimental system.
The continuous current mode (CCM) boost Power factor correction (PFC) converter using closed-coupled inductors is one of the well-known topologies that can achieve miniaturization and weight reduction of the inductors. Change in the magnetic flux during the half cycle of an input AC voltage has not been analyzed in detail so far. In this paper, the change in the magnetic flux in the half cycle of the input AC voltage is analyzed.