Goro Shirai

Automatic generation control for DC-link power system

This paper discusses LFC (load frequency control) with HVDC (high voltage DC transmission system). So far, AGC (automatic generation control) has been focused on economic dispatch control and load frequency control; especially the latter is mainly on frequency stabilization for AC-link network systems. However, the upcoming power-electronics based HVDC transmission system offers new aspects for the improvement of frequency control. In this paper, 2-area and 3-area network systems are used to discuss how a HVDC interconnected system works to improve frequency fluctuation for random load disturbance. Because DC-interconnection provides an adequate power exchange, reduction of frequency deviations for both systems is achieved if the control gain is tuned properly. However, the effect differs by geometrical differences. In order to discuss the effectiveness of HVDC link for load frequency control, the HVDC-link is designed as a feedback system of system state variables, whose concept has been used for Hokkaido-Honshu link in Japan and also proposed for Minami-Fukumitsus link in Japan. The simulated load fluctuation model is constructed to demonstrate actual loads behavior. In AC-interconnected power systems, the HVDC-link connecting two of the local systems does not provide frequency improvement since power exchange has been already achieved on the links. However, if two isolated power systems are interconnected, the HVDC-link will make the important role to sustain the frequency deviation within regular tolerance even if the capacity is very small compared to those of two systems, these acts as a single system and the disturbance to the smaller system is cancelled as a tiny disturbance of the whole system.

Robust thyristor-controlled series capacitor controller design based on linear matrix inequality for a multi-machine power system

Abstract Power system stabilizing control has an important role in maintaining synchronism in power systems during major disturbances resulting from sudden changes of load and configuration. The thyristor-controlled series capacitor (TCSC) is one of the representative devices in flexible AC transmission systems. In this paper, robust TCSC controllers are applied to suppress disturbances in realistic power systems. H ∞ control is adopted as the methodology of the robust controller design along with a linear matrix inequality (LMI), which solves the Lyapunov inequality without the weighting coefficients used in other control theories. In the proposed design, load changes are treated as a system uncertainty in the LMI approach. The proposed LMI-based approach is shown to be effective in the design of TCSC controllers to enhance robustness and response by simulations on a test system.

Load frequency control using Lyapunov's second method: Bang-bang control of speed changer position

This letter reports a bang-bang load frequency control policy based on the second method of Lyapunov. The proposed method is simple and practically feasible for implementation. A numerical illustration on a two-area load frequency control system is presented in order to verify the practicality of the proposed method.

Suppression of short term disturbances from renewable resources by load frequency control considering different characteristics of power plants

A new control method based on PID for load frequency control in power systems is proposed in order to suppress frequency deviations due to load and generating power fluctuations occurring by increased penetration of renewable resources such as photovoltaics or wind farms. The variation of renewable resources can be considered to be a kind of load fluctuations. For the appropriate absorption of load fluctuations, these are separated into three components — short-term less than 10 minutes, medium-term ranging 10 to 30 minutes, and long-term sustaining over 30 minutes. In this paper, to absorb these random load disturbances effectively fast generators and slow ones are separately controlled by processing the filtered random frequency deviations. The separation of slower and fast load fluctuations is carried out by low pass filter. The effectiveness of the proposed method is illustrated by a three area power systems.

TCSC control for longitudinal network

This paper proposes a new TCSC control scheme for integrated power systems realizing many number of TCSC in complex power systems. The proposed method is based on pseudo inverse, DC power flow, and linear quadratic control (LQR) methodology. DC power flow equation is usually used to make a relationship between power flows and phase angles but this is applied to relate the state variables and local power flows observed at the bus where the TCSC is installed. This method is capable for both of radial and loop system. A 3-machine 9-bus longitudinal system is employed to show the design procedure, and the effectiveness is discussed through stability analysis.

Load frequency control using a governor and voltage controls vis a new approach

This letter reports the decentralized load frequency control through a governor and voltage controls by a new approach based on Siljaks theory [1]. The design of the optimal feedback gains in each area can be made using the state variables belonging to the corresponding decoupled area.

Load frequency sampled-data control via Lyapunov's second method

This letter presents a sampled-data load frequency control based on the second method of Lyapunov. The proposed method is simple and practically feasible for implementation. A numerical illustration on a two-area load frequency control system is presented in order to verify the practicality of the proposed method.

Autonomous Distributed Control of Micro Grid with Diesel Generator

Recently, solar energy generation and wind power generation have been introduced to electric power system. But, as for this natural energy, influence such as frequency fluctuation is exerted on electric power system, which is a fundamental problem in operation of a small grid system such as micro-grid. These systems should provide appropriate power quality compared to a large grid. However, using the telecommunication line for monitoring and controlling the system devices is costly, as an alternative method, autonomous distribution control that enables local power supply and demand control is also required in design and operational stage. This paper discusses benefits of these methods conducting cost evaluation

Contribution of power electronics for load frequency control of interconnected power system

In recent years, it begins to be anxious about the warming problem by the increase in carbon dioxide on a scale of the Earth. Actually, this is considered to be also a cause that this year is overly developing of a large-scale typhoon and the direct hit to a Japanese mainland. Inside of such backgrounds, every country in the world is performing the research and development about the new power generation system from various viewpoints in such backgrounds for the amount curtailment of discharge of carbon dioxide. In our country, a target called the amount of domestic wind power of 3000 MW is held up by the 2010 fiscal year. Then, (in this research, by using a control device original whether it is what cannot increase system interconnection more paying attention to a wind power place, stability is improved and comparison and examination is performed. This research shall perform comparison and examination for the ability to carry out which the system interconnection of the wind power place in the future, without causing quality aggravation of electric power by imitating the existing electric utility in a specific area

Output feedback TCSC controller design making use of linear matrix inequality

Power system stabilizing control plays an important role to remain in synchronism during major disturbances resulting from sudden or sustained load changes. TCSC (thyristor controlled series capacitor) is one of the representative devices of FACTS (flexible AC transmission system), in this paper, a design method for an output feedback TCSC controller using a detailed model has been applied to suppress system disturbances in large-scale power systems. As the methodology of robust controller design, H/sub /spl infin// control has been adopted. Currently, LMI (linear matrix inequality) is very effective, since it solves the Lyapunov inequality without considering the weighting coefficients used in other control theories. In the proposed approach, the load change is treated as a system uncertainty in the LMI approach. The proposed LMI-based approach is proved to be applicable for the design of TCSC controllers to enhance robustness and response by simulations on a test system.