Yoshinobu Ueda

A method of three-phase balancing in microgrid by photovoltaic generation systems

Recently, a small-scale power system has been able to perform autonomous or islanding operation with some distributed generators. But in such a microgrid, it is afraid that serious voltage imbalance may be caused by unbalanced loads during the islanding operation. Fortunately, grid interactive inverters of the distributed generators often have some amount of surplus capacity. This paper deals with a three-phase balancing method utilizing the surplus capacity. By the proposed method, the inverters output negative sequence currents to suppress the voltage imbalance within their surplus capacities. Operating characteristics and its effectiveness are confirmed by some simulation results.

Estimation of battery capacity for suppression of a PV power plant output fluctuation

Demonstration project named “Verification of Grid Stabilization with Large-scale PV Power Generation” has been conducted by the New Energy and Industrial Technology Development Organization (NEDO). In the Wakkanai PV power station, Sodium-Sulfur battery system is introduced to realize some additional functions. Since fluctuation in output of MW-class PV system may disturb the stable operation of power station, it is important to develop a fluctuation suppression technology. The authors have developed a fluctuation suppression using a battery system. In this paper, the relation between available battery capacity and fluctuation suppression performance is analyzed by computational simulation. This paper also estimates and discusses required battery capacity for fluctuation suppression.

Optimized operation and stabilization of microgrids with multiple energy resources

A microgrid supply/demand control system is proposed. In this control system, operation planning is realized based on generation and load forecasting by using artificial neural network and fuzzy systems. Unit commitment of generation includes start/stop of power generation and energy storage. Load following function is accomplished based on PI control scheme. To compensate for the power fluctuation in microgrid, power system stabilizer with EDLC is proposed.

Verification test results of the wide-area control and operation system for distributed generation of renewable energy

The Wide-Area Control and Operation System for stabilizing renewable energy generations utilizing averaging effect was proposed to reduce capacity of battery energy storage system and a demonstrative project supported by Ministry of Environment of Japan was conducted in order to verify effects of the proposed system. In this paper, concept and configuration of the system are introduced and verification test results and effects of the demonstrative project are reported.

Power electronics solutions applied to a variety of demonstrative microgrid projects

Three different energy storage systems by use of power electronics technologies are presented. These systems were applied to demonstrative microgrid projects which have concepts different one another. Concepts of the projects, requirements on energy storage systems and demonstration results are introduced.

An active network control method using distributed energy resources in microgrids

An active network control method using distributed energy resources in microgrids is shown. Some features of the system were outlined. And also, power system stabilizer to compensate for the fluctuation of active power in microgrid is proposed. The microgrid with these new techniques can contribute to efficient operation of DGs and stable power supply for customers.