Masashi Kitayama

Study on rotary loop flow controller for futuristic distribution networks

With a rapid increase of environmental friendly Renewable type Dispersed Generation (RDG) like Photovoltaic, Wind Power etc., in Japan and around the world, there are many issues like voltage deviation, reverse power flow and effective management of existing distribution network that are likely to surface on their integration to the network due to the variable output of some RDG. In finding solutions to such issues, loop configuration based futuristic distribution networks are being explored. However, to realize these networks the development of a reliable, efficient and cheaper device like a loop flow controller is imperative. Hence, this paper proposes two types of Rotary Loop Flow Controllers, one is series type and the other is UPFC type. Both of them are based on the induction machine technique with no slip rings and are capable of regulating the power flow by rotating rotors. The proposed controllers are less costly, more efficient, more tolerant to over voltages/currents as compared to self-commutated type controllers. Further, UPFC type rotary loop flow controller has additional advantages like smaller capacity, ability to control reactive power than the series type of rotary loop flow controller. The proper functioning of the proposed controllers is confirmed through simulations and experiments.

Real-time grid simulation platform for system analysis using virtual power source

A smart grid test bed with 6.6kV experimental distribution network which includes mega-photovoltaic generation systems, rechargeable batteries and so on has been conducted. In order to demonstrate the system performance of smart grid with this test bed, a new simulation platform has been developed. The simulation platform consists of BTB (Back-To-Back), real-time power system simulator and interface controller, and it performs the upper power grid which can reproduce various disturbances such as frequency deviation and instantaneous voltage drop. This paper describes the system configuration, verification test result and application example of this simulation platform.

Development of Fast Simulation Model for Doubly-Fed Wind Generation Systems

Abstract – We propose a fast simulation model of wind generator with a frequency converter, such as a doubly-fed type. The aim of the model is to provide a model that can evaluate an impact of wind generator system (WG) on utility side in both transient and relatively long term normal operation. Through, some simulation software based on root mean square value, for example EUROSTAG, provides a unified method that can handle both short-term and long-term analysis. But it is difficult for RMS based model to handle with a behavior of WG with a frequency converter under system fault condition. So we have developed an instantaneous value based fast simulation model that can handle with both short-term and relatively longer-term analysis.. Keywords : Wind power generation, Fast simulation model, Simplification for converter 1. Introduction The integration of wind generator system (WG) has large influences over a variety of operational conditions. These operational conditions vary from short-term, such as a transient behaviour during a fault, to longer-term, such as power fluctuation under a normal operation. In order to harness WG successfully, the impact of WG must be analyzed in both short and long term. As a result, both short-term and long-term simulation models for WG are required, and it is high burden in view of cost and maintenance. For longer-term analysis, the focus point is mainly active and reactive power swing due to wind fluctuation, and a simulation model based on root mean square value (RMS) is suitable. There are already some RMS based simulation tools that can handle with both long and short term analysis, such as MATLAB. But, in short-term analysis, a simulation model for WG should be represented in detail manner, and a model based on an instantaneous value is appropriate. Because, under a fault condition, WG with FRT(fault ride through) function acts in complex manner, and the behavior during a fault condition could have a large impact over a subsequent longer-term situation. It means that a simulation model for WG based on an instantaneous value is suitable. But it is very time consuming to conduct a long-term analysis with a model based on an instantaneous value. To solve this problem, we have developed and evaluate a fast simulation model for WG based on an instantaneous value that can handle with relatively longer-term analysis. In this study, we first developed a simulation model for WG to conduct both short-term and long-term analysis. Our aim of the model is to evaluate an impact of WG on utility side. The developed model is doubly-fed type. It includes pitch control, frequency conversion, start-up and shut-down function, and FRT(Fault Ride Through) so that we can evaluate WG under a various operational conditions. Then we applied a simplification method to the simulation model so that the model can handle with relatively longer-term analysis. The method of simplifica-tion is to model self-commutated converters in frequency converter as a pair of voltage and current source. The AC side of converter is represented as a voltage source, whereas the DC side of converter is represented as a current source. Through this kind of simplification may be popular in simplifying a self-commutated converters, we do not see any report that evaluates this simplification method under various operational conditions of WG. So, we evaluate this simplification method in this study.