Kiyoyuki Kitamura

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

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