Yuji Shindo

Cauer Circuit Representation of the Homogenized Eddy-Current Field Based on the Legendre Expansion for a Magnetic Sheet

Using the Legendre expansion of the magnetic field distribution, we derive the standard Cauer circuit representation of the frequency-dependent properties of magnetic sheets and discuss its physical meaning. The representation of non-linear inductors is derived so as to apply the Cauer circuit in the dynamic hysteresis modeling of silicon steel. This circuit accurately reconstructs the hysteretic property under pulsewidth modulation excitation using only one or two hysteretic elements.

Low voltage ride through capability of a grid connected inverter based on the virtual synchronous generator

When distributed generators are connected to the grid, it is required that the system withstand the voltage dip caused by the grid failure. This is known as the low voltage ride through (LVRT). One of the effective choices to realize the LVRT is a grid connected inverter with virtual synchronous generator (VSG). This paper present a VSG control with capability for LVRT. By using this control, the operation of inverter can be continued even if a severe voltage dip at the grid has happened.

PWM inverter-excited iron loss characteristics of a reactor core

In this paper, we focus on an evaluation of iron losses in a reactor core under pulse width modulation (PWM) inverter excitation. We examine the inverter- and sinusoidal-fed iron losses of the reactor core through both experiments and numerical simulations. The proposed measurement includes operation at a higher frequency than is used commercially. We discuss the building factor (BF) of reactor losses under PWM inverter and sinusoidal excitations based on material iron losses measured in a ring specimen. The BF calculation based on inverter-fed tests is an almost constant value because the magnetic flux density distributions related to the carrier frequency mostly do not depend on the reactor gaps.

Impact of Material on the Iron Losses of a Reactor With an Air Gap

The iron losses of a reactor with an air gap are investigated and compared for three different magnetic materials, namely, grain-oriented material (GO230), high performance non-oriented Fe-Si metal (super E ST125), and nanocrystalline soft magnetic material (FINEMET FT-3M). The iron losses of the reactor are measured by the experiments for different voltage supply frequencies and amplitudes. The measured data are compared with the material iron losses that are calculated from the manufacturers material datasheets. It is concluded that the air gap is responsible for a large part of the increase between the reactor and material iron losses and that the FT-3M has sensibly higher building factor compared with the other materials.

Effects of suppressing frequency fluctuations by parallel operation of virtual synchronous generator in microgrids

When a greatly varying load is connected to a weak power system, stability of the system becomes a problem. In these days, because the use of renewable energy is accelerating, not only the loads but also the distributed generators can be critical factors in destabilizing the system. A virtual synchronous generator (VSG) control allows a static inverter to behave similar to a synchronous generator (SG). Using this VSG technology, we can increase the introduction ratio of renewable sources, and thus, we can combine various types of power sources. Simultaneously, if the combination of governor and rotor inertia is represented in a first-order lag element, the VSG can suppress the frequency fluctuations in microgrids. In this paper, the oscillation mechanism in parallel operations of generators is clarified, and we present the effects of suppressing the frequency fluctuations using the VSG. The results are verified by simulation using EMTP-RV and in laboratory experiments.

Virtual Synchronous Generator control with Double Decoupled Synchronous Reference Frame for single-phase inverter

We have proposed the Virtual Synchronous Generator control (VSG control) and have tested it using the demonstration equipment [1]. By using the VSG control, three-phase inverters of current control type are able to run both in grid-connecting operation and in grid-disconnecting operation. Furthermore, in order to control a single-phase inverter like a three-phase inverter using the VSG control, we have applied the technique called “Double Decoupled Synchronous Reference Frame” (DDSRF). In this paper, we will show you the simulation results and experimental results of the single-phase inverter using the VSG control with DDSRF.

Frequency response of an actuator with solid iron core

This paper is concerned with a new method for a derivation of frequency response of an actuator with solid iron core. This actuator is designed for a magnet bearing of thrust-direction at a high-speed motor. The rotor of this motor is levitated by magnetic bearings. Authors developed a high-speed permanent magnet synchronous motor and other components of this system including the magnet bearings and this controller. To design the control system of the actuator, we want transfer function of plant described by polynomial expression because this makes design of controller easy.

Cauer Ladder Network Representation of Eddy-Current Fields for Model Order Reduction Using Finite-Element Method

A novel model order reduction method for efficient analysis of linear eddy-current problems is proposed in which the quasi-static electromagnetic fields are expressed by a weighted sum of a sequence of static electric- and magnetic-field modes. The modes are calculated sequentially by static electric and static magnetic computations using the conventional finite-element method, and the time-dependent weights are the voltages and currents of an equivalent Cauer ladder network of the problem. In this paper, the formulation of the method and a numerical test problem are presented, and the accuracy and enormous efficiency of the method are demonstrated by solving a 3-D nonlinear inductor model with a voltage excitation by a dc–dc converter, linearized around the dc current using frozen differential permeability.

Efficient circuit representation of eddy-current fields

Purpose This paper aims to discuss the relationship between the continued fraction form of the analytical solution in the frequency domain, the orthogonal function expansion and their circuit realization to derive an efficient representation of the eddy-current field in the conducting sheet and wire/cylinder. Effective frequency ranges of representations are analytically derived. Design/methodology/approach The Cauer circuit representation is derived from the continued fraction form of analytical solution and from the orthogonal polynomial expansion. Simple circuit calculations give the upper frequency bounds where the truncated circuit and orthogonal expansion are applicable. Findings The Cauer circuit representation and the orthogonal polynomial expansions for the magnetic sheet in the E-mode and for the wire in the axial H-mode are derived. The upper frequency bound for the Cauer circuit is roughly proportional to N4 with N inductive elements, whereas the frequency bound for the finite element eddy-current analysis with uniform N elements is roughly proportional to N2. Practical implications The Cauer circuit representation is expected to provide an efficient homogenization method because it requires only several elements to describe the eddy-current field over a wide frequency range. Originality/value The applicable frequency ranges are analytically derived depending on the conductor geometry and on the truncation types.

Dynamical model of an electromagnet by cauer ladder network representation of eddy-current fields

This paper presents a novel dynamical modeling method for the magnetic actuators. The magnetic field is decomposed into orthogonal distribution functions by using continued fraction, which is equivalent to Cauer ladder network. The linearized transfer function of the magnetic force is derived by using theses distribution functions. Numerical example of electromagnet is also presented to show the effectiveness of this method.