Nobuyuki Kasa

Flyback inverter controlled by sensorless current MPPT for photovoltaic power system

This paper presents a flyback inverter controlled by sensorless current maximum power point tracking (MPPT) for a small photovoltaic (PV) power system. Although the proposed system has small output power such as 300 W, a few sets of small PV power systems can be easily connected in parallel to yield higher output power. When a PV power system is constructed with a number of small power systems, the total system cost will increase and will be a matter of concern. To overcome this difficulty, this paper proposes a PV system that uses no expensive dc current sensor but utilizes the method of estimating the PV current from the PV voltage. The paper shows that the application of this novel sensorless current flyback inverter to an MPPT-operated PV system exhibits satisfactory MPPT performance similar to the one exhibited by the system with a dc current sensor as well. This paper also deals with the design method and the operation of the unique flyback inverter with center-tapped secondary winding.

A mechanical sensorless control system for salient-pole brushless DC motor with autocalibration of estimated position angles

In this paper, a mechanical sensorless control system is reported for salient-pole brushless DC motor drives. Here, two new methods are proposed for obtaining the position angle, the accuracy of which affects the operation of the switching devices of the inverter that drives the motor. First, the method for estimating the position angle is proposed. Secondly, the correcting method for reducing the errors involved in the estimation of position angle is given. The experimental results show that the estimated position angles are calibrated automatically, and then the proposed sensorless control system can control the speed and the position angles of the motor precisely.

A digital current controller for zero-current transition bidirectional converter

This paper presents a digital current controller for zero-current transition (ZCT) bidirectional converters. In order to reduce switching losses and noises, a soft-switching technique is adopted. It is suitable for the pulse-width modulation (PWM), because the resonant transition is very short and it is independent of the switching frequency. A field programmable gate array (FPGA) and a 2.5 MHz analog to digital (A/D) converter can control the inductor current within 2 us. From the experimental results, the current is controlled precisely even if the duty factor is more than 50%. Also, the zero-current transition operation of the main switch is confirmed and it is expected that the efficiency of the converter can be improved. The proposed converter is suitable for an energy transformer between batteries and motors, or generators.

Analysis of a coupled inductor for zero-current transition boost converters

This paper presents an analysis of a coupled inductor for zero-current transition (ZCT) converters. In order to reduce switching losses and noises, a soft-switching technique is adopted. It is suitable for the pulse-width modulation (PWM), because the resonant transition is very short and it is independent of the switching frequency. We adapt a coupled inductor which consists of a boost inductor and a resonant inductor to ZCT converters. To analyze and simulate a magnetic field distribution of the coupled inductor, the ANSYS software is employed. A prototype converter is implemented by a field programmable gate array (FPGA) and a 2.5MHz analog to digital (A/D) converter. From the experimental results, the zero-current transition operation of the main switch is confirmed and the efficiency of the converter using the coupled inductor is improved.

Modeling of novel type diaphragm pump

This work deals with modeling of magnetically driven new type diaphragm pump and further development of driving control system for it. The pump has highly nonlinear behavior and complicated structure which makes the modeling task quite involved. After designing a motion model of the pump, an analysis of the magnetic field distribution and generated electromagnetic forces driving the pump is given. Several simulation results show the effectiveness of the proposed system model.

Modeling and control of a new type diaphragm pump using DSP

This paper deals with modeling and design of reliable controller for a new type diaphragm pump. Because of parameter uncertainties and nonlinear dynamics of the pump model, a fuzzy-like PID controller is designed. The controller design is based on fuzzy Lyapunov synthesis and stability and the robustness analysis of the designed system are straightforward. The pump control system is driven by a digital signal processor (DSP) allowing high control quality. Several simulation results show the effectiveness of the proposed system.

Zero-current transition flyback inverter for small scale wind power generation systems

This paper presents a zero-current transition (ZCT) flyback inverter for small scale wind power generation systems. Although the proposed system has such small output power as 500 W, a few sets of wind power generation systems can be easily connected in parallel for the higher output power requirements. When the wind power generation system is constructed by a lot of small power ones, the total system-cost and the efficiency of an inverter will be a matter of concern. To overcome these difficult problems, we propose a speed controller without a wind speed sensor. The speed controller consists of the maximum power point tracking and the two-degree of freedom controller. And we also propose a ZCT flyback inverter and the IGBT is turned off at zero-current switching (ZCS).

Analysis of coupled inductors and transformers for zero-current transition boost converters

This paper presents an analysis of coupled inductors and transformers for zero-current transition (ZCT) converters. The coupled inductors and the transformer are adapted to ZCT converters to improve the efficiency of the converters. To analyze and simulate a magnetic field distribution of the coupled inductors and the transformers, the ANSYS software is employed. Prototype converters are a boost converter and a forward converter. Their controllers are implemented on a field programmable gate array (FPGA) and a 2.5 MHz analog to digital (A/D) converter.