In this paper, a conventional constant-switching-frequency discontinuous mode converter is analyzed by applying the double Fourier series expansion. It is found that the fundamental component and higher-order harmonics included in the input current waveform are obtained by the Fourier series expansion of the mean value of the inductor current. As the result of analysis, components included in the input current waveform are fundamental plus third harmonics and other components can be neglected. From the theoretical analysis, a new method removing the distortion of the input current waveform is also proposed. In spite of an open loop system, the proposed method makes a great improvement of the total harmonic distortion even if the ratio of output voltage to input voltage is very low.
A high voltage switch (50kV 2kA) with IGBTs in series driven by displacement current has been developed. Displacement current, which is generated when the master stage is turned on, drives other stages of the high voltage switch. This method avoids the problems of increasing the turn-on time of the high voltage switch because the displacement current flows in series through those stages and drives them simultaneously. To increase the stages driven by this methods, we have increased the displacement current with improved driving method. In the improved driving method, first, the master stage makes the second stage turn on with the sub-capacitance between second stage and ground, next the displacement current generated with the master stage and the second stage makes other stages turn on. With increased displacement current, switching operation under conditions of 50kV and 2kA is obtained with 56 IGBTs' stages in series. Clamp circuits with Zener diodes are adopted to the high voltage switch and it is shown that these clamp circuits are effective to protect IGBTs from overvoltage in this switch.
This paper presents a DSP-controlled shunt active filter for harmonic termination of a power distribution line. The purpose of the active filter based on voltage detection is to damp out harmonic propagation caused by line inductors and shunt capacitor for power factor correction. However, time and phase delays inherent in the control circuit of the active filter might lead to poor harmonic damping performance. The hardware and software designs are important for achieving stable operation and satisfactory damping performance. This paper provides the details of design and implementation of a fully-digital controller for the active filter. Experimental results verify the viability and effectiveness of the DSP-controlled shunt active filter.
“A waveform compensation circuit”, which generates compensation voltage to suppress ripple in current and flatten output current pulse of pulse forming network, is developed to increase the efficiency of pulse modulator with a Klystron. A waveform compensation circuit consists of compensation units connected in series. Each compensation unit consists of capacitances charged with compensation voltage, diodes, and FET switches. Compensation voltage is generated by turning on FET switches and turning eff diodes. Waveform shaping of output pulse of pulse forming network has been realized with compensation voltage up to 3kV. Flat top region of current pulse has been spread to double by increasing compensation voltage and improving fineness of timing control. Using the waveform compensation circuit, ripple in output current pulse of pulse forming network has been suppressed under ±0.1% of the peak current.
Chip current imbalances caused by the difference of impedance of each parallel circuit in an Insulated Gate Bipolar Transistor (IGBT) module were analyzed using the three dimensional finite element method (3D-FEM). The circuit inductance of the test module was also calculated using the results of the analysis. Measurements of the current of each parallel circuit and circuit inductance using a test module were performed to confirm the results of the analysis. The results of the analysis were in good agreement with the experimental results. The 3D-FEM analysis was therefore used to design a new structure of bus bars in a module and the results presented a good current sharing.
At substations of Shinkansen, three-phase power received from the utility power system is converted into a pair of single phase power sources with different phases. When a Shinkansen car passes the boundary of two power sources with different phases, the power source for Shinkansen instantly switches from one to the other. Vacuum switches have been used as changeover switches so far. It takes about 300 msec for switching. By this system, Shinkansen cars can pass the boundary of two power sources under powering. Generally speaking, when a vacuum switch is closed at a voltage-phase of 90°, the inrush current into transformer will become small. On the other hand, although the power from substation is not supplied to Shinkansen at no-voltage of power source switching at the changeover section, counter electromotive force by auxiliary motor appears on the main transformer on the car. Due to the counter electromotive force, it is difficult to suppress the inrush current into the main transformer by the conventional vacuum switch. In contrast, the use of static switch such as semiconductor device can decrease the exciting inrush current into the transformer of Shinkansen car, when the turn-on timing of changeover switch is controlled. We investigated the control method for suppressing the exciting inrush current into transformer when a static switch is used as a changeover switch instead of vacuum switch. To verify the control method, we built and tested a mini model to simulate a changeover switch.
The servo motor systems with the PMSM have been widely used for industry applications, home electric appliances, and so on, due to the progress of the power electronics, because of simple structure, easy maintenance, high efficiency, etc.. Moreover, because the PMSM can realize the same high performance as DC motor, it is used in the fields where the high speed and high accuracy control is required. However, when the PMSM rotates, the motor frame is vibrated due to the torque ripple of the PMSM and so on. Also, when frequency of the motor frame vibration is especially close to the resonant frequency of the mechanical system, large vibration and acoustic noise are produced. In this paper, authors propose a suppression control method of the vibration for PMSM utilizing feedforward compensation control, and a generation method of compensation signals for the feedforward control by repetitive control with the auto-tuning function, and Fourier transform using a vibration signal acquired by an acceleration sensor attached to the motor frame, considering periodicity. However, the proposed auto-tuning function is not perfect. So a method to cope with this imperfectness is also presented. An experimental system to detect and reduce the vibration is constructed, and the effectiveness of the proposed method is confirmed by experimental results.
This paper describes a study for the Sbinkansen traction power converter with the Injection Enhanced Gate Transistors, IEGT's. The IEGT is a newly developed power device, which can be applied not only for high voltage circuits, but also for high switching frequency operation. It also reduces power dissipation compared with GTO thyristors, and the neutral point clamped IGBT converters will be replaced by it. For evaluating practical performances of the IEGT power converters, both bench and actual running tests with a test train, were taken place with prototype equipment.
In recent years, three-phase small induction motors fed by inverter have been widely employed in industrial machines, home appliances, office automation equipments, etc as a drive device. Howevex the inverter generates a vibration, a noise, a heating, etc in such induction motor. The three-phase small induction motors are required to have both a large average torque and a small alternating torque. Previously, we have derived the practical equations to calculate the generated torque [6, 7]. In this paper, we research a new design strategy for a three-phase small induction motor fed by a six-stepped wave voltage-source inverter. Our new strategy is based on the equivalent circuit parameter approach. At first, by using the practical operating characteristic equations, we have shown the relationship among the equivalent circuit parameters and the operating characteristics. In other words, the equivalent circuit parameters have some effects on the various operating characteristics. Simulations have demonstrated one of the guidelines for the optimum design. Secondly, in order to verify the validity of our new strategy, a three-phase small induction motor having optimum equivalent circuit parameters has been compared with previous three-phase small induction motors. As a result, we have clarified that our new strategy is capable of the optimum design of the three-phase small induction motors fed by the six-stepped wave voltage-source inverter for practical use.
With the rapid development of power electronic devices, rare earth permanent magnet (PM) and motor control technology, interior permanent magnet synchronous motor (IPMSM) is being widely used in various applications. In some applications such as electric vehicles and compressors, except for high efficiency, extensive constant-power operating range is also desired. This paper discusses an IPMSM with adjustable PM armature flux linkage by means of adapting flux-shortening iron pieces in the space of rotor's flux barriers. The performance of the proposed IPMSM is studied using normalized analysis for general meaning. It shows that the operating range of the proposed IPMSM can be greatly extended by lowering the PM armature flux level through the iron pieces. Due to the possibility of decreasing the PM armature flux linkage, the proposed IPMSM requires less d-axis armature current in the area of flux-weakening control, so the efficiency and power factor can be improved, especially at light load and high speed operation. The variations of efficiency relating to operating conditions and PM flux level are discussed. The efficiency and power factor map of the proposed IPMSM is presented. The maps show that the high-efficiency and high-power factor operating area of the proposed IPMSM is larger than that of the conventional one, indicating the advantage of the proposed IPMSM in improving efficiency. Based on the analysis of the efficiency performance at various decreasing rates of PM armature flux linkage, optimal decreasing pattern of PM armature flux linkage is obtained corresponding to various operating conditions.
This paper proposes position and force hybrid control of a mobile manipulator to cooperate with its subsystems which are a wheeled mobile robot and a manipulator arm. These subsystems have different dynamical characteristics. Moreover, a wheeled mobile robot is subject to nonholonomic constraints. In general, these issues are taken into consideration in developing a planning and control algorithm. This paper describes a unified approach to control a mobile manipulator which can regarded as a redundant manipulator. In the proposed approach, realizing the high manipulability of the end-effector's motion, the redundancy of the whole system is utilized under consideration of the dynamical behavior. Then equivalent mass matrix is introduced as a performance index of the end-effector's dynamical motion. The effectiveness of the proposed control methods is confirmed by several experimental results.
Many researchers have attempted to clarify the definitions of active power, reactive power, active current, reactive current, etc. for unbalanced and non-sinusoidal three-phase situations. The so-called pq theory has given a new definition of instantaneous reactive power, and it has been discussed and developed by many authors. In this paper, the merits and demerits of the instantaneous reactive power compensator are discussed. It is shown theoretically that applying instantaneous reactive power compensation to unbalanced three-phase systems has a serious disadvantage in that it causes third-order harmonic currents on the source side, which problem cannot be avoided. To overcome this problem the authors propose a new approach, and name it the “quasi-instantaneous” reactive power compensator. It compensates individual-phase reactive currents. The basic principles of the quasi-instantaneous reactive current compensator are discussed in detail, and its validity is confirmed using digital simulation. In particular the authors show that the power factor of each phase becomes unity on the source side, but the source currents remain unbalanced when the proposed method is applied.
In the assembly process of a printed circuit board, automatic flow soldering equipment has been used for more than 50 years. Authors have succeeded in the practical use of a perfectly noncontact linear electromagnetic pump (abbreviated LEP). As a result of the optimization of thrust characteristics, the considerable improvement in the solder performance was confirmed. In this paper, the following subjects are described. (1) The considerable reduction of the bridge defects between adjacencies electrodes is possible, when following conditions are satisfied, solder rise height y=0.01[m], substrate desorption angle θ=20[deg], square of solder flow velocity vsy2>0.14. (2) As a result of evaluating the LEP, it was confirmed that required thrust 15[N] were generated. And then, it became clear that soldering equipment using the LEP surpassed the system using a mechanical pump with regard to soldering performance.
The interior permanent magnet (IPM) motor has many advantages, such as high efficiency etc., and this motor is becoming widely used not only in home applications like air conditioners but also electric vehicles. Although the investigation of optimal design of IPM motors is important, the analysis of IPM motors using the finite element method and the optimization method is very rare. This is, because the IPM motor should be analyzed considering the rotation of rotor in order to obtain the torque ripple, the mesh generation at each step of rotation is troublesome. If the nonconforming mesh technique is used in the optimization problems with rotating meshes, the practical optimization considering the rotation of rotor becomes easy, because the mesh at each angle of rotation can be obtained by only combining meshes of a rotor and a stator. In this paper, techniques for the optimal design of permanent magnet motor considering rotation are investigated. The nonconforming mesh and the optimization technique such as Rosenbrock's mthod (RBM), evolution strategy (ES) are introduced for practical design. The constraints of the minimum average torque and the maximum induced voltage are also taken into account during the optimization. The effects of the kind of objective function and the optimization method on the obtained result are discussed. It is shown that about 25% of volume of magnet and about 20% of torque ripple can be reduced by using ES.
Magnetic Levitation Transport system is suspended by magnetic levitation, and it is therefore basically free of contact parts that produce dust particles by friction. In order to take advantage of this no-dust characteristic, a number of magnetic levitation systems are currently being developed as transport systems for use in semiconductor manufacturing processes. The authors proposed the development of a new magnetic levitation system using a linear induction motor. Although the magnetic levitation characteristic was stabilized successfully, the moving control was complicated because the moving speed is dependent on the frequency of the commercial-frequency power supply. The present paper proposes the moving control of an AC attraction-type magnetic levitation transport system using a two-phase linear motor. The present system uses a low-frequency two-phase sinusoidal power supply amplitude-modulated from the commercial-frequency power supply. The levitation force is generated and controlled by a commercial-frequency AC magnetic field. In order to control the moving of the system, a low-modulation frequency control method is adopted.
The AC system voltage sensitivity is shown to be affected by the SVC operation point change in addition to the AC system short circuit capacity change. Then, an SVC detailed model is proposed considering the dead times in the digital control and the phase controlled thyristors. With this model, the control instability characteristics is discussed based on the root locus calculation. In this discussion, it is indicated that the instability possibly appears in a real AC system and that the oscillation frequency is in a narrow range. Then, based on the discussion, a fast on-line automatic gain adjustment function is proposed. The instability and its oscillation frequency are confirmed to be consistent with the discussion results through the simulation test with the actual SVC controller and through the field test in the actual AC system and the SVC facility. Furthermore, the automatic gain adjustment function is also confirmed to show good performance as designed in these tests.
A superconducting(SC) magnetically levitated (Maglev) transportation system has been developed in Japan and various experiments have been done in the new test line at Yamanashi prefecture. Although the superconducting electrodynamic suspension (EDS) system has the advantage of stable levitation without active control, various electromagnetic or mechanical disturbances can cause the change of gap length and the displacement or oscillation of the bogie. As the damping of the EDS system is shown to be small, additional damping factor is needed to increase the stability of the levitation under the influence of disturbance. Then the damper coil system is proposed. The copper coils are installed in front of the SC coils on the bogie. We have developed three dimensional numerical simulation program for the Maglev bogie. The damper coils system is included in this program, and running simulations of the Maglev bogie are undertaken. The damping factor for each rotational direction is shown. The running simulation when the bogie passes the lateral guideway displacement is calculated, and effect of the damper coils is clearly shown.