Kazutaka Itako

A single sensor type MPPT control method for PV generation systems

This paper introduces a new MPPT control method for solar photovoltaic (PV) power generation systems. The proposed method include its ability to perform MPPT using only a single solar cell voltage detection sensor and simultaneously predicting the voltage necessary for load voltage control, which is essential to real systems. As a result, this control method offers advantages of the simplified hardware configuration and the low cost.

A new current sensorless MPPT control method for PV generation systems

This paper proposes a new current sensorless maximum power point tracking (MPPT) control for PV generation systems. This control method offers advantages of the simplified hardware configuration and the low cost, by using only one sensor to measure the PV output voltage. Furthermore, its MPPT efficiency is extremely high

New I-V Characteristics Scan-Type MPPT Control Method for PV Generation System

This paper proposes the new scanning interval control method in I-V characteristics scan-type MPPT control for a PV generation system. From the experimental results, it is clarified that even if the value of L is low, the set detecting interval can be assured regardless of difference of the solar radiation intensity, and that the new MPPT control offers outstanding effectiveness in partially shaded environments.

PCS with scanning-type MPPT control for industrial grid-connected PV power generation system

In a standalone photovoltaic (PV) power generation system, the author previously proposed a new type of MPPT (Maximum Power Point Tracking) control method in which the I-V characteristics are scanned with detection interval control at specified intervals and the maximum power point is monitored. The author obtained satisfactory results using this new MPPT control method. This paper investigates applying the new MPPT control method to power conditioning system (PCS) in an industrial grid-connected type PV power generation system. The experimental results clearly demonstrate that the developed PCS offers outstanding effectiveness in partially shaded environments.

Unity power factor PWM rectifier reducing the number of sensors

In this paper, a new control method of a reversible PWM rectifier is discussed, where the input voltage sensor and the DC current sensor are eliminated; the performance corresponds to that of the original system can be obtained by estimating the input voltage and DC load current from measured input current and DC output voltage. By using this method, the simplified circuit configuration with half number of required sensors and reduction of the cost is realized. Because when the system has an inverter load, the DC load current includes the high switching frequency components, it is impossible to use directly the DC load current for the feed-forward control. Therefore, the treatment of the DC load current for the feed-forward control is also investigated

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.

MPPT Control Method Using Boost Type DC-DC Converter for PV Generation System with Mismatched Modules

Nowadays in a household PV generation system, it is generally connecting PV modules in series and then output to the power-conditioner. However, when PV modules are mismatched, it will lead to a wrong maximum power point tracking (MPPT) to all modules and a power decreasing of the whole system. Aiming at this problem, this paper presents the idea which improves the MPPT without changing the conventional power-conditioner, by adding a boost type DC-DC converter behind each module. Simulations of PSIM and experiments are taken to prove this theory. The result shows that, by this idea, the generated power of the conventional PV generation system can be greatly increased under the condition of mismatch.

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.

Study on Improvement of MPPT Efficiency in PV Generation System with Partial Shadow

The maximum power point of PV (photovoltaic) generation moves depending on weather conditions and load. Therefore, it is significant to make sure that the panels can work at the maximum power point under MPPT (maximum power point tracking) control. However, it has the problems of low efficiency and unstable operation when panels are covered by the partial shadow. The result is that the output power may be substantially decreased. To overcome this issue, the authors propose a new plug-in operation point correction system. This system is put between PV panels and PCS (power conditioning system) in the existing PV generation system. In this paper, the experimental results describe that the output electric energy increases approximately 1.4 times as compared with the conventional system when the proposed correction system is inserted.

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.