Masakazu Michihira

A novel simulation technique of the PV generation system using real weather conditions

The photovoltaic (PV) generation system has been studied and watched with keen interest as a clean energy source. Moreover, the various MPPT control methods are proposed to more efficient utilized. Now, in order to confirm the effectiveness of each control method, simulation or experimental analysis is used. Here, from an economical point of view, simulation analysis is more effective. However, the more detailed model of a solar cell for simulation is necessary. In this paper, a novel simulation analysis method of the PV generation system with VI characteristics equation of a solar cell and real weather condition is proposed. Here, ATP is used as the simulation analysis software. We compared the results from the simulation analysis with the experimental one. Consequently, two values were very matched and the validity of the proposed method is examined. The result shows that the cost effective verification for the efficiency, availability and stability of the PV generation systems. The comparison research of various control methods like MPPT control under the same weather conditions is possible.

A novel quasi-resonant DC-DC converter using phase-shift modulation in secondary side of high-frequency transformer

This paper presents a novel quasi-resonant DC-DC converter using phase-shift modulation (PSM) in the secondary side of a high-frequency transformer. The proposed DC-DC converter can easily achieve soft-switching operation under the low commutating current and no freewheeling current. As a result, the conduction losses caused by their currents is substantially reduced compared with the conventional soft-switching DC-DC converters. The operation principle and analysis are illustrated and discussed by means of simulation and experimental results.

The time-frequency analysis of the harmonics with wavelet transform for the power electronics systems

The time frequency analysis technique using wavelet transform is proposed to overcome EMC (electromagnetic compatibility) problems. The proposed technique takes into consideration the change in amplitude of the harmonics during the observation. By applying it to harmonics analysis, we can analyze the harmonics from not only the frequency but also the time point of view. Therefore, it enables us to obtain the effective solution for harmonics problems. In this paper, a wavelet transform is carried out against the actual measured data. Based on obtained results, it is shown that the features and high validity of the proposed technique for the power electronics field by comparing with the previous approach using FFT (fast Fourier transform).

A comparative study of steady-state characteristics of permanentmagnet synchronous generator systems

The steady-state characteristics of a novel wind generator system proposed by the present authors are discussed in comparison with the conventional wind generator system consisting of a permanent magnet synchronous generator, a three-phase diode bridge rectifier, and so on. The simulation and experimental results show the ripple of the DC current and developed torque in the proposed system is significantly reduced by about 70%. Furthermore, the efficiency of the generator is improved by more than 3%. The advantage in the proposed system is that a fractional smoothing reactor can be used to draw a DC current without ripple, and a higher DC voltage compared to the conventional system is easily produced.

A comparative study on power generation characteristics of permanent magnet synchronous generators

Power generation characteristics of two generator systems consisting of a permanent magnet synchronous generator and diode bridge rectifiers are discussed in this paper. One of the discussed systems has three-phase stator windings, and the other has two sets of three-phase (six-phase) stator windings to reduce pulsation in the electromagnetic torque and DC current. Experimental results reveal that the power generation efficiency of the system having six-phase stator windings is higher than that of the system having three-phase stator windings for a light load. The maximum power generation efficiency of the system having six-phase stator windings is almost the same as that of the system having three-phase stator windings.

Operation analysis of high efficiency grid connected bi-directional power conversion system for various storage battery systems with bi-directional switch circuit topology

In recent years, there is an increasing demand for various types of storage battery systems, such as home battery systems, V2H(Vehicle-to-Home)/V2G(Vehicle-to-Grid) systems, and UPS systems. Performance requirements for the power conversion system within these storage battery systems are small size, light weight and high efficiency. We propose a new power conversion system so called the GAP-D3 converter that is a bi-directional power control system, comprising of a bi-directional switch circuit topology with natural commutation switching mode. This paper describes the features of GAP-D3 converter including this new current compensation control with simulation and experimental results.

Resonant pole-assisted soft switching DC-DC power converter with phase-shifted PWM scheme of active switches in transformer secondary-side

This paper presents a novel prototype of quasi-resonant PWM DC-DC IGBT converter using active semiconductor switches in series with diodes of rectifier circuit in link transformer secondary-side. This DC-DC converter proposed here can easily achieve soft-switching operation under the condition of low commutating current and no freewheeling circulation current. The component conduction losses caused by their currents are substantially reduced as compared with the other soft-switching DC-DC converters. Its operating principle and unique features are described on the basis of the previously developed DC-DC converters. The operating characteristics of this new converter topology in steady-state are illustrated and discussed including the simulated analysis and feasible experimental results.

An Experimental Study on a PWM Method without Dead-Time Error for Three-Phase Voltage-Fed Inverter

Voltage-fed inverters have dead-time to protect against short-circuit of the DC-link voltage. Dead-time distorts ACoutput voltage and decreases DC-link voltage utilization. To overcome these problems, the authors propose a novel PWM method without voltage error caused by the dead-time of the converter. In this paper, the principle and theoretical operation of the proposed PWM method are described in detail and the theory is confirmed through experiment results.

Proposal of Inrush Current Prevention Circuit without Electrical Relay

Generally, in electric equipment, a large inrush current flows in the capacitor when the power is turned on. The inrush current causes deposition of terminals and switches, melting of fuses, and so on. Therefore, conventional inrush current prevention circuits using an electrical relay and a controller are provided. However, the use of electrical relay enhances concern about an increase in cost and charge-time. In order to solve these problems, this paper proposes the inrush current prevention circuit without electrical relay. In this paper, the authors examine the effectiveness of the proposed circuit from experimental results.

Application of the time-frequency analysis using wavelet transform to harmonics analysis in the power conversion systems

In recent years, next generation power semiconductor devices have attracted attention such as SiC device, GaN device and so on. By applying next generation power semiconductor devices to power conversion systems, its operation frequency becomes higher. As the results, small size, light weight and high efficiency of the power conversion system can be realized. However, when operation frequency becomes high, harmonics issue is caused. Therefore, harmonics analysis of the power conversion system is very important. In order to analyze the harmonics in detail, this paper proposes Wavelet transform analysis as the time-frequency analysis. This paper describes the feature of the Wavelet transform from experimental results.