Hiroyuki Sugihara

Analysis Results of Output Power Loss Due to the Grid Voltage Rise in Grid-Connected Photovoltaic Power Generation Systems

This paper describes the connected photovoltaic (PV) power generation systems grid overvoltage protection function and summarizes the occurrence of the output power loss due to the grid voltage rise. Power injection from the PV system will raise the voltage at the power distribution line. A power conditioning subsystem (PCS) needs to regulate its output if the voltage becomes higher than the upper limit in order to avoid the overvoltage at the power grid. Thus, a PV system cannot generate electricity under the high grid voltage. There are 553 residential PV systems installed in Ota, Japan, for the demonstration research project of clustered PV systems. Measurement data of these 2.1-MW grid-connected PV systems are used for the analysis. Only the limited number of PV systems experienced a significant amount of output energy loss due to the high grid voltage in a particular day, whereas the other systems outputs also raise the grid voltage. The causes of this maldistribution of the output energy loss are the difference of the line impedance, the difference of the starting voltage of the PCSs grid overvoltage protection function, and the imbalance of the load in single-phase three-wire power distribution systems. The present control of the PCS successfully avoids the overvoltage on the grid but cannot share the loss.

Performance Ratio and Yield Analysis of Grid Connected Clustered PV Systems in Japan

It is becoming more important to evaluate the installed PV systems performance and loss factors to enhance the systems efficiency and pull more electric power from the systems. This paper describes the evaluation method of PV systems and summarizes the results of annual performance and loss analysis. Grid voltage and snow coverage are two major serious loss factors for PV systems, optimized array configuration results in more system yield on roof mounted residential PV systems

Demonstrative research on clustered PV systems

An ongoing project of large scale PV systems is described. The target of this project is to solve technical problems such as restriction of PV system output, higher harmonics and islanding operation of PV systems clustered in a residential district. In this project, 553 grid-connected PV systems with batteries installed at residences are under continuous monitoring. The results obtained in this project are expected to provide information and technologies for further introduction of PV systems.

The characteristics of higher harmonics in clustered PV systems

The PCS on the market approved by Japan Electrical Safety & Environment Technology Laboratory (JET) is satisfactory for the standards specified in the governments guideline of higher harmonics. So problems of higher harmonics are less serious than those of others in the present time. However the characteristics of higher harmonics are partially unknown if clustered PV systems are interconnected to the distribution line. In this research, higher harmonics voltage and higher harmonics current and phase are measured as for as 39 harmonics every one minute. We investigate quantity of generated higher harmonics and the transition. This investigation is carried out for PV-Systems made by main 4 manufacturers in Japan

The simulated equipment of distribution line for the research on clustered PV Systems

In the process of rapid expansion of PV systems, it is expected clustered PV systems are installed at a particular distribution system. In this case, if the suppression of output of the PV systems by over-voltage and influence on the system become actual, they may be a restriction of expansion still more. Therefore new energy and industrial technology development organization started demonstrative research on clustered PV systems in the FY 2002, which is a 5-year plan in order to expand PV systems smoothly and solidly. In this R&D, the islanding test on the condition that clustered PV systems are interconnected to the simulated equipment of distribution line that consists of 30 simulated residences with simulated power supply of PV arrays, simulated load and, simulated impedance

Development & Verification of New Simulation Method for Islanding Protection Under Clustered Installation of Over 500 PV Systems

Authors developed a new simulation method for analysis on an islanding protection of a utility grid including 500 PV systems or more. The validity of this method was verified by comparing the calculated results with the actual test results that carried out. As a result, it was verified that the combination use of the passive and the active protection functions to PCS (power conditioning sub-system) is very effective to avoid the occurrence of an islanding phenomenon in a utility grid under large-scale clustered installation of PV systems