We propose a method of a sigle phase PWM for a utility-connected power supply in photovoltaic power generation systems. In this paper, the PWM is derived from camparing levels of signal waves with ones of carrier waves which have bipolar swing different from unipolar one in the conventional PWM, and shifting phase a little at exery on-off time. We can expect that array voltage needed is reduced by about 15% and harmonics content contained in output voltage is reduced by about 24% in this PWM in comparison with the conventional with equal output voltage.

抄録全体を表示

Lots of self-tuning control schemes have been proposed for unknown parameter systems. As one of them, a self-tuning pole-assignment scheme has been widely used for unknown time delay systems. However, these methods need to solve the so-called Diophantine equation to find control parameters. This is computationally easy for a single-input single-output (SISO) low order system, but requires much more computing time in the case of a high order system or a multi-input multi-output (MIMO) system. In this paper, a simple scheme for designing self-tuning controllers is presented, which can take account of the stability margin and control performance without solving the Diophantine equation. Furthermore, in order to investigate the effectiveness of the proposed scheme, it is applied to a pneumatic servo system.

抄録全体を表示

Superconducting magnetic energy storage (SMES) system would be a valuable system for a power line stabilization. It would increase stability by supporting peak energy and compensating generation shortage. With a development of a large capacity GTO thyristor suitable for 20MW level power conversion system, it is possible to control the four-quadrant of the real power (P) and the reactive power (Q) condition by self-commutated power converters with high performances. In this paper, it is shown a new direct connected multiple current source converters, and also explained the control strategies suitable for a pilot plant of a SMES system. Then they will give the feasibility of the control strategies by showing the EMTP simulation results.

抄録全体を表示

Suppression of torsional vibration is one of important topics on motion control. A torsional vibration is generated because of elastic elements of a mechanical system driven by a servo motor. The simplest model of such systems is two-mass system. In recent years, several kinds of controllers for two-mass system are proposed, but their design methods are not simple.
This paper proposes a new design method of a second-order controller for two-mass system. Two types of controllers are designed using this design method. One of them shows good performances in vibration suppression, and the other shows good robustness. The method is very simple because the parameters of these controllers are determined using linear equations of the ratio of moment of inertia of two-mass system. The validity of this method is confirmed by experiments.

抄録全体を表示

In a harmonic detection system of active power filters, the pq-theory can be used for the calculation of harmonic current detection. A high pass filter of the first order is usually used for the detection of the ac component of instantaneous real power (p) and instantaneous imaginary power (q). But, in that system transient response for a load change is not high enough. We propose a new detection system in which ac components are derived from p and q using a moving average high-pass filter. By the proposed system, control response and accuracy are very good even in the case of an abrupt load change. The operating performance of the proposed system is confirmed by laboratory model test.

抄録全体を表示

The paper presents a computing method of functional derivatives with respect to system parameters such as magnetic resistivity, electric conductivity and source current in steady-state electromagetic fields. The method is based on Gataux differential, namely a kind of sensitivity analysis, and the functional derivatives are proved to be calculated by explicit forms of the solutions of the electromagnetic field equation and its adjoint equation. The methodis applied in success to a simple eddy current testing problem

抄録全体を表示

Self-commutated converters are intensively studied to realize high performance power equipment for electric power systems. The converters have attractive features such as independent control of active and reactive power and reliable operations in power line faults. The switching losses of the converters with gate turn-off thyristors are, however, rather larger than those of conventional line commutated converters. To reduce the losses, a conventional PWM scheme such as subharmonic modulation requires low switching frequencies and causes inferior control performance especially in power line faults.
This paper proposes a novel PWM method for series connected multiple self-commutated converters. The method employs the space vector representation of the multiple converters and the switching actions are determined through comparing the vectors with voltage command vectors. The scheme realizes a low switching number in steady state as well as fast response to ensure reliable operations even in the power line faults. The validity of the control is examined by a computer simulation and experiments with a static var compensator.

抄録全体を表示

Overhead rigid conductor line in tunnel is free from the fear of disconnection because the contact wire is not tensioned, and it is superior in maintenance saving. In order to introduce this in open section, we have developed “a long span type overhead rigid conductor line of catenary system”. This contact line structure consists of contact wire of no tension attached to the supporter which has a small drag coefficient hanged by the messenger wire. In this time, we have developed “square supporter” to make the drag smaller and put it to various tests with support point interval 50m and 10m. As the testing results, the contact loss is 1_??_2% at 130km/h, and this overhead rigid conductor line can collect the current with stability equal to the normal catenary system.

抄録全体を表示

A nonlinear model is proposed representing air-gap magnetic flux density distribution in a synchronous machine with magnetic saturation in the teeth of rotor and stator. To consider saturation of teeth of iron core, the authors assume that saturatable part is distributing around air-gap. A model to express air-gap flux is derived from magnetic circuit inside of the synchronous machine. The co-saturation function is decided from the no-load saturation curve. The calculated air-gap magnetic flux distribution by this saturation model is compared with that of measured at the on-load test. As a result, the calculated air-gap magnetic flux distribution from the proposed saturation model agrees well to measured one.

抄録全体を表示

Since their discovery, many attempts have been made in industrial applications of superconducting oxides whose critical temperature(Tc) is higher than the boiling temperature of liquid nitrogen. In particular, levitation technologies with the pinning effect have been drawing attention, which is the basis of many applications, including magnetic bearings, flywheels, and non-contact transportation systems. This paper describes a new type of magnetic levitation type surface motor using the bulk high-Tc superconductor and electromagnets. The present system consists of the stator constructed by two-dimensional array(8×4) of small electromagnets with 10×10mm² pole-face and the mover made of styrofoam containing YBaCuO superconductor with the size of 42×42mm² prepared by MPMG (Melt-Powder-Melt-Growth) method. The mover can be shifted between the nearest neighbor poles on the array by flipping the polarity of electromagnets, without any contact. By the control combined with PC, continuous shifts toward forward and backward directions were realized.

抄録全体を表示

A brushless and slotless dc linear motor employing a movable set of neodymium-boron-iron type magnets is discussed in this paper. The motor can be used as a linear stepping motor as well, due to its unique topology. The flux density at specific points and the static force along the travel length of the motor were measured. A 3D finite element analysis of the flux distribution and of the static force were carried out. The dynamic characteristics such as velocity, output power and efficiency for various conditions were measured.

抄録全体を表示

We developed SR compact superconducting magnets which are used for X ray lithography. If the vertical axis of the superconducting coil of SR magnet is out of the vertical line the horizontal field Bx will be appeared. The electron beam is kicked toward vertical direction by this field and this causes a large electron beam orbit distortion in the horizontal coordinate. From the beam optics, the gradient of the coil axis needs to be less than 1 mrad. We developed a magnetic field distribution measurement system of the horizontal magnetic field Bx(s) in the high bending magnetic field By₀ which is 3.5T at the center of the SR (Synchrotron Radiation) magnet and measured the distribution of Bx(s) . Where, s is the beam direction. From the horizontal magnetic field Bx(s) and vertical dipole field By₀(=3.5T), we can evaluate the gradient of bending field from the vertical direction. The average gradient along S direction was 0.55mrad. This value satisfies our requirement which is less than 1mrad.

抄録全体を表示

The presence of stator current harmonics from static frequency converter starter operation results in the induction of currents of various magnitudes and frequencies on the surface of the rotor. These eddy currents flow in series-parallel paths comprised of rotor iron, rotor wedges, damper bars and retaining rings and distribute according to the impedance of the paths. If the plural rotor wedges retain field coils in one slot, the eddy current paths are complicated further. This paper describes turbine generator rotor eddy currents and losses for a static frequency converter starting. To consider air parts between a rotor wedge and the adjoining wedge, the currents are calculated by three-dimensional numerical magnetic field analysis. The results are as follows.
(1) The eddy currents flow mainly in the wedge.
(2) If there are the damper bars, the eddy currents concentrate in the damper bars between two adjoining wedges.
(3) If there is no damper bar, the eddy currents concentrate in the rotor tooth between two adjoining wedges.

抄録全体を表示

This paper presents a new vector control for induction motor drives in full block mode, so called One-Pulse mode, of inverters. For traction drives the inverter usually operates in this mode in a high speed region. The amplitude of voltage vector is restricted constant in the mode. The conventional vector control is not applicable as it requires controllability of both the amplitude and the phase of the voltage vector for all time. The proposed scheme provides quick torque response even in the One-Pulse mode. Experimental results are shown to validate the effectiveness of the control.

抄録全体を表示

Induction motor drive with PWM inverter control, which can reduce the weight of the driving devices, is used for Shinkansen trains in order to achieve high speed transportation.
This paper describes the experimental results for controlling wheel slip and re-adhesion at high speed running with the type 953 Shinkansen test train. The induction motor for each axle of this train is individually controlled by an independent PWM inverter. By introducing the vector control for the induction motor drive system, quick response for the motor torque can be achieved when wheels are going to slip. The control scheme for the wheel slip and re-adhesion is that the motor torque is gradually reduced by increasing of wheel slip speed.
The results show, it is possible to recover to adhesive condition against wheel slip, without excessive motor torque reduction, when the reducing torque value and control time constant are properly selected.
By these tests, re-adhesion characteristics improvement by induction motor vector control are obtained. To the next step, the parallel motor control system with a vector controlled inverter will be investigated.

抄録全体を表示