Tsugutomo Kudoh

Development of real time hotspot detection system using scan-method for PV generation system

This paper presents a development of real time hotspot detection system using scan-method about the PV solar panel I-V characteristic to distinguish between normal cells and hot-spot cells depending on the changes of the panel output current in real time. The current changes help to detect the hot-spot phenomenon. In case if partial shadowing occurs to the PV panel, the power conditioning system (PCS) gives an immediate judgment whether hot-spot arises from one of the cells or not by applying the scan-method. The PCS is programed to calculate the current rate depending on the difference in the current divided by the short circuit current. From the experimental results, it is clarified that the hot-spot cells can be determined regardless of the solar intensity radiation.

Proposition of novel real time hot-spot detection method for PV generation system

Currently, the production and the number of installations of photovoltaic (PV) modules has been increasing rapidly. Accordingly, the number of failures has also increased. Many failures are a result of the Hot-Spot phenomenon in which defective cell becomes hot when shadow occurs on the cell. Previously, the authors performed operating analysis of the PV module with Hot-Spot so that we construct a system to monitor Hot-Spot. Therefore, we perform operating analysis of Hot-Spot modules with string composition, and propose novel real time Hot-Spot detection method based on the result of the analysis in this paper.

Hot-Spot Detection System with Correction of Operating Point for PV Generation System

Currently, the production and the number of installations of PV (photovoltaic) modules have been increasing rapidly because of a feed-in tariff in Japan. Accordingly, the number of failures has also increased. Many failures are a result of the Hot-Spot phenomenon in which defective cell becomes hot when shadow occurs on the cell. On the other hand, if shadow occurs on normal cell, there are cases that P&O method that is MPPT (maximum power point tracking) control method incorporated in conventional PV system cannot track maximum power point and generated power decreases. The correspondence is required rapidly if these trouble occur. However, conventional PV system monitors generated power, correspondence is impossible by monitoring generated power. Previously, the authors developed real time Hot-Spot detection system that incorporates into PCS (power conditioning system). Thus, the authors developed plug-in type Hot-Spot monitoring system that includes “PV peak shift method” and confirmed effectiveness of the system in this time. “PV peak shift method” loads “Scan method” that is MPPT control method and measures I-V (current-voltage) characteristic by changing voltage of module from open to short by “Scan method” on a regular basis. The developed Hot-Spot monitoring system uses slope of I-V characteristic of PV module. Inserting developed system into already installed PV system, Hot-Spot can be easily monitored in real time and PV system can be operated at maximum power point. Key word: PV generation system, Hot-Spot phenomenon, correction of operating point, plug-in type.

A study of the electrical properties of self-biased channel MOS diodes for solar-cell applications

AbstractWe propose two types of low-cost, low-loss diodes as alternatives to Schottky barrier diodes (SBDs) for use as bypass diodes connected in parallel with solar-cell panels. Both of our proposed devices are self-biasing channel MOS diodes consisting of an n-channel MOS structure that features three-terminal operation combined with a DMOS cell structure exploiting self-biasing effects. By reducing the threshold voltage of the MOS gate, these devices feature lower on-voltages and lower rates of growth in the reverse leakage current with increasing temperature, thus preventing thermal runaway. To investigate the properties of our devices, we used a device simulator to analyze their performance as bypass diodes for a solar-cell panel. Our results indicate that when a shadow partially covers the cell, the current flowing on the load side of the solar-cell panel is about 50% larger than that observed for a Cr SBD, indicating the potential for significantly improved performance.

Voltage-based hot-spot detection method for PV string using projector

This paper proposes a voltage-based hot-spot detection method for PV string using projector. Hot-spots form in solar cells at defects causing high carrier recombination rate, it appears as high reverse leakage current of p-n junction when solar cells are partial shadowed. Using this characteristic, authors previously developed a Voltage-based hot-spot detection method to quickly identify and characterize the severity of module hot-spot. The validity of this method has been confirmed. However, previous experimental results were show for just one module. In this paper, experiments are done on plural modules in string. From the result, this method works effectively for PV string. It provides the possibility of hot-spot inspection after modules are installed.