Katsuya Hirachi

Switched-mode PFC rectifier with high-frequency transformer link for high-power density single phase UPS

The general purpose of single-phase UPS topologies are indispensable for the considerable reduction of harmonic current components in AC mains as well as realization of unity power factor correction (PFC). In particular, the single phase PFC rectifier with a high-frequency isolation transformer link has some advantages as an electrically-isolated AC/DC conversion circuit for small scale UPS. This UPS is capable of eliminating harmonic currents, leak current components and realizing an isolation between AC input and DC output power stage as well as matching the DC voltage of the PWM inverter by means of incorporating a compact high frequency transformer into high-frequency intermediate state. Three types of isolated PFC rectifiers designed for 2 kVA, 3 kVA and 5 kVA-UPSs are put into practical use respectively, as new topology. This paper presents a high-frequency link PFC rectifier, its related operating principle and control strategy, together with the steady-state and dynamic state performances of these types of UPSs developed from a practical point of view.

Cost-effective practical developments of high-performance and multi-functional UPS with new system configurations and their specific control implementations

The state-of-the art UPS which is composed of power conversion and inversion conditioning and processing configuration incorporating simple half-bridge active AC/DC converter and half-bridge PWM inverter circuits with no electrical isolation power stage has attracted special interest in computer and telecommunication systems. This UPS topology is highly cost-effective and suitable for power conversion efficiency improvement and volumetric size and weight reduction. However, this attractive UPS topology has a significant disadvantage that storage batteries have to be connected to the high DC link bus. In order to provide an acceptable DC voltage link with storage batteries, an improved type of application-specific UPS topologies have been proposed and investigated from a practical point of view. This paper presents a nonelectrical isolated prototype of UPS circuit topologies incorporating converter circuits for battery bank interface and their related specific multi-functional control strategies, which are composed of cost-effective IGBT modules. The operating principles of power conversion topologies and control strategies are described. The experimental results of a unique and high-performance UPS topology with battery bank interface circuit are illustrated for 3 kVA UPS application and compared with the latest conventional UPS with storage batteries connected to the high DC voltage bus.<<ETX>>

Characteristics of a novel energy transmission for a rechargeable cardiac pacemaker by using a resonant DC-DC converter

A full-bridge resonant converter which transfers several W of power across a large, variable air gap has been designed and built. The converter can power a rechargeable cardiac pacemaker through intact skin by utilizing a transformer with an air gap of 0.5-1.5 cm between the primary and the secondary. The secondary winding would be implanted under the skin, and the primary would be placed on top of the secondary outside the body.<<ETX>>

A large air gap flat transformer for a transcutaneous energy transmission system

A flat transformer for a full-bridge series resonant DC/DC power converter which transfers several W of power across a large, variable human skin gap has been designed and built, The power converter can power a rechargeable cardiac pacemaker battery through intact skin by utilizing a transformer with an air gap of 0.5 to 1.5 cm between the primary and the secondary windings. A ferrite pot core is used for the primary winding. The secondary winding with a flat amorphous core would be implanted under the skin, and the primary would be placed on top of the secondary outside the body.<<ETX>>

Two buck choppers built-in single phase one stage pfc converter with reduced DC voltage ripple and its specific control scheme

This paper present an improved circuit topology for a buck chopper type single phase PFC-AC/DC converter with active power filtering function, which has smaller in reactor size and lighter in its weight, and can minimize the DC output voltage ripple factor. In addition, this active PFC-AC/DC converter can be also suppressed the current harmonics in utility AC grid without any specific feedback control scheme with current sensor interface. The circuit configuration treated here is more suitable for a variety of emergency power as well as telecommunication supply, where the lightning resistance is particularly considered to be more effective for 48 V-10 A output specification. In this paper, the operating principle of proposed AC-DC converter circuit using power MOSFETs and its related control implementation are described, along with its simulation and experimental results and their evaluations. The extended PFC-AC/DC converter topologies are demonstrated, which are operating at the proposed control scheme.

Practical development of a high-performance UPS with a novel buck-boost chopper circuit

In UPS without transformers, a boost chopper circuit is of the greatest importance for stepping up battery voltage and feeding it to the inverter. Problems with conventional boost chopper circuits are that a high step-up ratio worsens efficiency, and that there is a voltage imbalance between the high side and the low side of DC link voltage. The circuit type proposed here overcomes the conventional circuit types shortcomings by employing a buck-boost chopper circuit with two magnetically coupled coils. Further, with this circuit type as a bi-directional chopper, the authors added a battery charging function, which allowed them to omit the independent charging circuit that has been necessary until now. They used this circuit type in developing a 1 kVA UPS and achieved excellent characteristics.

Feasible developments of utility-interactive multi-functional bidirectional converter for solar photovoltaic generating system incorporating storage batteries

In recent years, expecting photovoltaic generating system using utility-interactive PWM inverters have attracted special interest as effective means to broaden the application areas of clean natural energy sources without using a large amount of fossil fuels. This paper presents a unique circuit and system configurations for the solar battery and storage battery in such a PV power system. The system implementation incorporating the control strategy introduced in switching schemes between stand-alone and utility-interactive operations is discussed. Furthermore the experimental results tested through trially-produced 3 kVA prototype power converters and their effectiveness are illustrated and evaluated.<<ETX>>

A Novel Prototype Discontinuous Inductor Current Mode Operated Three-Phase PFC Power Converter with Four Active Switches

The paper presents an advanced three-phase active PFC power converter with three-phase diode rectifier cascaded four-switch boost chopper. Its operating principle is described in detail as compared with the circuit operations of two conventional three-phase PFC power rectifiers; one switch boost chopper type and two switch boost chopper type. The operating characteristics of four switch boost chopper type three-phase PFC power converter are described from a practical point of view, being compared with those of one switch boost and two switch boost chopper type PFC converter topologies.

Practical performance evaluations on an improved circuit topology of active three-phase PFC power converter

This paper presents an operating principle in steady state and unique features of a new prototype topology of a utility interactive three-phase active PFC power converter circuit. Its harmonic components of utility-gridside line current and PFC performances are evaluated and discussed on the basis of the experimental and simulation results as compared with the other conventional types of three-phase PFC converters.

Dual high-frequency chopper-based single stage PFC converter with output DC high quality

This paper presents a one stage circuit topology for a double buck chopper type single phase PFC converter with active power filtering function in a utility AC grid side and DC output power quality, which can realize much smaller in reactor size and lighter in its weight, along with two unique channel control schemes. The main advantageous point of the newly-proposed PFC converter includes that the output DC output voltage ripple factor can be minimized by using two channel pluse modulation control loops. In addition, the active PFC converter treated here can also effectively suppress the line current harmonics in utility AC grid without any specific feedback control scheme employing a current sensor interface circuit. In this paper, the operating principle of new PFC AC-DC converter circuit using power MOSFETs and its related PWM control implementation are described, including its simulation and experimental results. The effective modified PFC converter topologies such as high-frequency link, double boost and double buck-boost topologies, which can operate under the same plinciple as the proposed two channel control scheme, are discussed notion.