Shigeaki Ogawa

Excitation control system design of rotary type frequency converter for performance improvement of power system dynamics

A rotary type frequency converter using two sets of adjustable speed generators/motors is expected to be applied at the interconnections between 50 Hz and 60 Hz power systems in Japan. The rotary type frequency converter can work not only as a power interchanger, but also as a power system stabilizer by effectively utilizing energy stored in rotors. In this paper, we investigate how the rotary type frequency converter affects power system dynamics. Since shaft torsional oscillation and slow response due to mechanical connections are inevitable and may lead to instability in power systems, we also present some countermeasures and control schemes to handle such inherent problems, and to improve the performance of power system dynamics. Control performance and effectiveness is examined for a test model system by digital transient simulation.

Practical evaluations for three-phase soft-switching inverter with high-frequency pulse-current transformer

In this paper, a prototype of the auxiliary resonant commutated snubber circuit (ARCS) incorporating a pulse-current feedback high-frequency transformer with power regeneration loop is described for three-phase inverter from a practical point of view. For three-phase voltage-fed soft-switching inverter, soft-switching active power filter and active PFC rectifier, the soft-switching inverter topology treated here has significant advantages of effective power loss reduction in the auxiliary active switching power devices in the ARCS. In addition, this paper presents a DSP-based digitally-control space vector-modulated three-phase voltage-fed inverter with high-frequency pulse-current transformer (HFPT) assisted ARCS, which can efficiently operate under a stable condition of a zero voltage soft-switching commutation. The steady-state operating circuit analysis of the new ARCS has the salient features and the practical design procedure of this resonant snubber are illustrated and discussed on the basis of simulation and experimental results. The operating performance of this soft-switching inverter using IGBT power modules and its evaluations in the steady-state are actually discussed as compared with the conventional three-phase voltage-fed space vector modulated hard-switching inverter.

Feasible system evaluations of 3-phase voltage source NPC soft-switching inverter with new space voltage vector modulation strategy

This paper presents a digitally-controlled 3-level 3-phase voltage source type soft switching IGBT inverter topology with two simple auxiliary active resonant DC link (ARDCL) snubbers which can basically operate under a condition of zero voltage switching (ZVS). Its operating principle and its related new instantaneous space vector allocation modulation method are originally proposed and discussed for telecommunication, transportation, industry and energy plants as well as distributive power supply systems. The feasible performances of ARDCL-assisted soft switching inverter suitable for high power applications is illustrated for 3-phase high power applications and evaluated on the basis of simulation and experimental results as compared with the 3-level 3-phase hard switching inverter using the latest IGBT power modules.

Simulation study of power quality compensation system using EDLC for distribution systems

Power quality problems such as voltage sags, voltage distortions, voltage interruptions and frequency or phase variations In distribution systems are serious concerns, especially for semiconductor manufacturing companies, paper mill companies and so on. We have been studying a power quality compensation (PQC) system using electric double-layer capacitors (EDLCs) for distribution systems, which compensates not only reactive powers but active powers for a short period to the systems. It has large capacitors on the DC side. There are two methods for the PQC system, a series connection type and a parallel connection type for loads. We compared them on needed capacities, the compensation ability and so on. Based on the comparison, we selected the parallel connection type for future development. A control system of the PQC system was developed to deliver power to the loads. Finally, detailed digital simulations of the PQC system were carried out and the behaviors were confirmed.

Robust control for rotary type frequency converter using two sets of adjustable speed generators/motors

Japan has two different frequency power systems, 50 Hz system and 60 Hz system. A frequency converter is required for interconnection between them. A power electronics based frequency converter, which is called static type frequency converter, is exploited at the interconnection points. The frequency converter can also be realized by using two sets of adjustable speed generator/motor (ASGM), whose structure is identical to that of an induction machine; rotor windings are excited by an AC voltage, and so called rotary type frequency converter. When applying this type of frequency converter to the interconnection points between two systems, where nonlinearity and disturbance inherently exist, in addition to functioning for interchange power between two systems, it should enhance power system stability by use of an effective and appropriate controller. Robust control for this kind of frequency converter has been studied in this paper and an effective controller is designed against disturbance and uncertainty in the power systems and examined in model power systems by digital simulation.

A Study on Reclosing Operation Considering Fault Current Limiter

Abstract This paper proposes the effective reclosing operation method in the current lirniter introduction power system. From a angular velocity, a field system voltage, a phase of the generator, the proposed method calculates the optimum reclosing time domain. The current lirniter used reactance type and resistive type. The examination was carried out using the Inst. of Electrical Engineers of Japan one-machine infinite bus system model in order to demonstrate the effectiveness of the proposal method. In the simulation, Impact ver2.3 was used.

Power interchange control of frequency converter using adjustable speed generator/motor taking into account multiple power flow conditions

ASGM (adjustable speed generator/motor) can control active power and reactive power independently by the AC excitation. It can also change the rotor speed. Because of the above characteristics, ASGM can be applied to frequency converter, where two ASGMs are used. The rotor shaft of their ASGMs is common. Here, it is necessary to design a control system in order to adjust active power to the specified value quickly. The design for the active power control by using a multiple-state eigenvalue control algorithm is described in this paper, which considers the both states before and after power interchange. It is made clear from the digital dynamic simulation that the power interchange control proposed in this paper is effective.