An effective analytical expression for maximum energy conversion in terms of DC-bus voltage, shaft speed, and turn-on and turn-off angles of a switched-reluctance generator (SRG) based on self-excitation mode and single-pulse operation is successfully presented. The proposed analytical model, which can describe the nonlinearity of the magnetic characteristics of an SRG with sufficient accuracy, is the key to derive the relation between maximum energy conversion and the aforementioned control variables. The optimal ratio of DC-bus voltage to shaft speed and excitation angle are proposed. Simulation and experimental results are provided to validate the analysis.
An exact 2D analytical model for predicting the magnetic field in idealized structures of flat and tubular linear permanent magnet machines with surface-mounted magnets and semi-closed slots is described. The open-circuit and armature reaction magnetic field distributions are analytically derived and compared to those obtianed by finite elements analyses. The analytical model is then used for studying the effect of the slot-opening dimensions on the performance of linear machines. The developed analytical model can be advantageously used for the analysis and design of a class of linear machines.
The flux density has a linear relationship with the magnetic field intensity when the flux density of a magnetic material is in the millitesla (mT) region. However in the high-frequency region, the magnetic flux is concentrated near the surface of the magnetic material owing to the skin effect. Therefore, it is necessary to consider the nonlinear magnetic properties of the material. In this paper, we propose a modified frequency response analysis method that takes into account the nonlinear distribution of the complex magnetic permeability with respect to the magnetic flux density, in order to accurately compute the magnetic flux distribution in the high-frequency range. The validity of the proposed analysis method is verified by comparing the computed data with measurements obtained by using a prototype (toroidal coil).
This paper summarizes the multilevel power conversion technologies published in THE IEEJ TRANSACTIONS ON INDUSTRY APPLICATIONS and presented at IEEJ Technical Meetings on Semiconductor Power Converter or Japan Industry Applications Society Conferences (JIASC) as well as international conference proceedings and journals. This survey includes various types of circuit topologies from the first neutral-point clamped PWM converter to the hottest modular multilevel cascaded converters, and their applications. In addition, some new circuit topologies of multilevel converters for low voltage applications are also reported.
This paper describes power system stabilization with a VSG (virtual synchronous generator) control scheme by using VSC (voltage source converter) type HVDC (high-voltage DC transmission) with SMES (superconducting magnetic energy storage). Power system stabilization schemes that prevent instability due to the disturbance in grids that are connected to renewable power sources were studied. This paper further discusses the effect of SMES connected to the DC link of the VSC-HVDC system for the compensation of power fluctuation caused by distributed generators in one AC newtork of HVDC for eliminating the influence on the network on the other side to which the HVDC is connected. Simulations using PSCAD/EMTDC were carried out to evaluate the performance of the applied control system.
Recently, linear resonant actuators (LRAs) have been used in a wide range of applications since they have many advantages: high efficiency, simple structure, easy control, and so on. On the other hand, they have a problem in that the amplitude decreases significantly in response to an external load. To overcome this problem, the effectiveness of PID control using back electromotive force (EMF) in maintaining a constant amplitude against an external load is investigated. This paper proposes a numerical method involving the use of the 3-D finite element method to analyze the dynamic characteristics of LRA when it is operated under PID control in PWM feedback control by using the back EMF detected from a coil. The effectiveness of this method is shown through measurements obtained by using a prototype.
The authors have proposed some actuators to be able to drive multi degree of freedom with the unit(1)-(3), and dynamic analysis methods involving the 3D finite element method for resonant actuators. This paper presents a new two-degree-of-freedom (two-DOF) resonant actuator that can be driven in the direction of X and Z axes under vector control. Vector control is employed to control each drive axis independently; the field current element (id element) is used as the Z-axis thrust element and the torque current element (iq element) is used as the X-axis thrust element. The effectiveness of the proposed two-DOF resonant actuator was confirmed by the amplitude in the direction of the X and Z axes being well controlled without there being any mutual interference.