Kenji Arimatsu

Development of a Novel Three-Phase Laminated-Core Variable Inductor for Var Compensation

This paper presents a novel three-phase laminated-core variable inductor made for the purpose of voltage stabilization in electric power systems. The proposed variable inductor has three-phase secondary ac windings together in one laminated-core to reduce the size and weight in comparison with the other single-phase ones. It can be applied as a var compensator since it can control the effective inductance of the secondary ac windings by dc excitation from the primary dc windings. First, the operating principle of the three-phase laminated-core variable inductor is described. Next, a trial 4.0 kVA variable inductor is designed based on reluctance network analysis (RNA), and then, the availability of the proposed variable inductor, which has good controllability and sinusoidal output current, is proved in experiments.

Iron Loss Calculation in a Three-Phase-Laminated-Core Variable Inductor Based on Reluctance Network Analysis

Variable inductors, which consist of only a magnetic core and primary dc and secondary ac windings, can control effective inductance of the secondary ac winding by primary dc excitation. Therefore, the variable inductors can be applied as a var compensator in electric power systems. In a previous paper, we have proposed a novel three-phase-laminated-core variable inductor. It has only one laminated core in which the three-phase secondary ac windings are installed to reduce size and weight in comparison with a conventional single-phase variable inductor. Good controllability and sinusoidal output current of the proposed variable inductor were demonstrated. This paper presents a method for calculating iron loss of the three-phase-laminated-core variable inductor based on reluctance network analysis (RNA). The validity of the proposed method is proved by comparing with measured values.

Development of Concentric-Winding Type Three-Phase Variable Inductor

A variable inductor, which consists of only magnetic core and primary dc and secondary ac windings, can control effective inductance of the secondary ac winding by the primary dc current due to the magnetic saturation effect. Hence, the variable inductor can be applied as a VAR compensator for voltage regulation in electric power systems. In a previous paper, a novel concentric-winding type three-phase variable inductor was proposed, in which the primary dc and secondary ac windings are concentrically wound on the same leg. It was indicated by a numerical analysis that the proposed variable inductor has good controllability and low distortion current. This paper presents the experimental results of a 4 kVA concentric-winding type three phase variable inductor. Furthermore, to prove the advantage of the proposed variable inductor, copper and iron losses, leakage flux, and reactive power per weight are compared with those of the previous variable inductor. It is demonstrated that the copper loss of the proposed variable inductor is improved by 40%, the leakage flux is reduced by half, and the weight can be reduced by 40% in comparison with the previous variable inductor.

Design for size and weight reduction of lap-winding type three-phase variable inductor

Variable inductors have a simple structure that consists of only magnetic core and primary dc and secondary ac windings, but can control effective inductance of the secondary ac winding by the primary dc current due to magnetic saturation effect. Hence, the variable inductors can be applied as a var compensator in electric power systems. In a previous paper, a lap-winding type three-phase variable inductor, which has the primary dc and secondary ac windings concentrically arranged on the same leg, was presented. It has a good controllability and low distortion current. This paper describes size and weight reduction of the lap-winding type three-phase variable inductor by focusing on the leg width. First, an initial design method of the leg width considering the influence of the dc-biased magnetization is presented. Next, a detailed design of the leg width for the size and weight reduction of the proposed variable inductor is described. Finally, characteristics of the size- and weight-reduced variable indu...

High-efficiency and cost-minimization method of energy storage system with multi storage devices for grid connection

An energy storage system is integrated into a power-grid to compensate for the power fluctuation from renewable energy systems. This paper proposes a high-efficiency and low-cost energy storage system for the power-grid. The proposed system combines multi-energy storage devices such as a LaB and an EDLC for reducing the cost incurred by the system for the complete operation period. This paper also proposes a control method to improve the converter efficiency. The proposed method divides the amplitude of the compensation power reference into the LaB and the EDLC. A 10-kW prototype system has been designed and implemented to validate the proposed architecture and system performance. Experimental results demonstrate that the proposed control method effectively compensated for the power fluctuation from the renewable energy system. Simulation analysis confirms that the proposed system reduces the cost and losses in comparison with the conventional system.

Development of a small, high-performance, voltage sag compensator COMPACT for high voltage users

The influence of instantaneous voltage drops in the power systems due to lightning have become a significant issue, because manufacturing facilities have become highly sophisticated and intelligent. On the other hand, it may be impossible to completely avoid instantaneous voltage drops in power systems caused by natural phenomena. In order to solve the problem of the voltage drops, this paper presents a high-speed compensation system for the instantaneous voltage drops, COMPACT. This paper describes the COMPACT and confirms its high speed switching performance.

A novel three-dimensional concentric-winding type three-phase variable inductor for reactive power compensation in electric power systems

Variable inductors consist of magnetic core and primary dc and secondary ac windings, which can control effective inductance of the secondary ac winding by the primary dc current due to magnetic saturation effect.

A Novel 3-D Concentric-Winding-Type Three-Phase Variable Inductor for Reactive Power Compensation in Electric Power Systems

A variable inductor consists of a magnetic core, primary dc windings, and secondary ac windings. The effective inductance of the secondary ac winding can be controlled by the primary dc current because of its nonlinear magnetic characteristic. Hence, variable inductors can be applied as a reactive power compensator for voltage stabilization in electric power systems, and have desirable features such as a simple and robust structure, low cost, and high reliability. In a previous paper, a concentric-winding-type three-phase variable inductor with a 2-D structure has been proposed. It was demonstrated that the 2-D variable inductor has good controllability and a low distortion current. To further increase productivity and reduce costs, this paper presents a novel concentric-winding-type three-phase variable inductor with a 3-D structure. It is demonstrated that the leakage flux of the proposed 3-D variable inductor is reduced by more than 30%. Furthermore, a 6.6 kV–100 kVA 3-D variable inductor is designed and compared to its 2-D counterpart. It is proved that eddy current loss, which is induced within an oil-immersed self-cooled tank because of leakage flux from the variable inductor, can be reduced to one-third of that of the 2-D variable inductor.

Loss analysis of energy-storage system with multiple storage devices for grid connection

Energy storage system is used in power-grid to compensate for the power fluctuation caused by renewable energy systems. This paper presents loss-analysis results of power converter utilized for the energy-storage systems. The system has multiple energy storage devices such as a LaB and an EDLC. This paper discusses two methods to distribute the compensation power reference to each device. Conventional method is that the compensation power reference is divided by frequency filter. Proposed method is that the compensation power reference is divided by amplitude limiter. This paper designs and implements a prototype system to validate the performances of the control method. Experimental results demonstrate that the proposed control method effectively compensated for the power fluctuation caused by the renewable energy system. This paper uses FRR (Fluctuation Reduction Rate) in order to evaluate the compensation ability of the system.