Takuhei Hashiguchi

Monitoring of Interconnected Power System Parameters using PMU based WAMS

In order to easily monitor the wide-area power system information covering many power producers, suppliers, and power companies, authors have been developed a PMU (phasor measurement unit) based WAMS (wide area measurement system). This WAMS momentarily gather information about the power oscillation affecting the stability of Japanese longitudinal power systems by signal processing of the power outlet phasor. This paper introduces the features of the PMU based WAMS, and an availability of the power outlet phasor is validated by comparing the measurements with actual power station. And as one of the applications, an estimation method of interconnected power system parameters from the monitored power oscillation information is proposed.

Robust pitch controller design in hybrid wind-diesel power generation system

In this paper, the robust control design of pitch controller for frequency control in a hybrid wind-diesel power generation system is proposed. The structure of the pitch controller is a 1st-order lead-lag compensator. To take system uncertainties into account, the coprime factorization is applied in system modeling. To obtain the controller parameters, the performance and stability conditions of Hinfin loop shaping technique are used to formulate the optimization problem. The genetic algorithm is employed to solve the problem. Simulation studies show the frequency control effect and robustness of the proposed controller against system uncertainties in comparison with a variable structure pitch control.

Control Scheme of Hybrid Wind-Diesel Power Generation System

Global warming is one of the most serious enviromental problems facing the world community today. It is typified by increasing the average temperature of Earths surface and extremes of weather both hot and cold. Therefore, implementing a smart and renewable energies such as wind power, photo voltaic etc are expected to deeply reduce heat-trapping emissions. Moreover, wind power is expected to be economically attractive when the wind speed of the proposed site is considerable for electrical generation and electric energy is not easily available from the grid (Ackermann, 2005). This situation is usually found on islands and/or in remote localities. However, wind power is intermittent due to worst case weather conditions such as an extended period of overcast skies or when there is no wind for several weeks. As a result, wind power generation is variable and unpredictable. The hybrid wind power with diesel generation has been suggested (Hunter, 1994) and (Lipman, 1989) to handle the problem above. A hybrid wind diesel system is very reliable because the diesel acts as a cushion to take care of variation in wind speed and would always maintain an average power equal to the set point. However, in addition to the unsteady nature of wind, another serious problem faced by the isolated power generation is the frequent change in load demands. This may cause large and severe oscillation of power. The fluctuation of output power of such renewable sources may cause a serious problem of frequency and voltage fluctuation of the grid, especially, in the case of isolated microgrid, which is the a small power supply network consisting of some renewable sources and loads. In the worst case, the system may lose stability if the system frequency can not be maintained in the acceptable range. Control schemes to enhance stability in a hybrid wind – diesel power system have been proposed by much researchers in the previous work. The programmed pitch controller (PPC) in the wind side can be expected to be a cost-effective device for reducing frequency deviation (Bhatti et. al ,1997) and (Das et. al, 1999). Nevertheless, under the sudden change of load demands and random wind power input, the pitch controller of the wind side and the governor of the diesel side may no longer be able to effectively control the system frequency due to theirs slow response. To overcome this problem, an Energy Storage (ES), which is able

Inverse additive perturbation-based optimization of robust PSS in an interconnected power system with wind farms

This paper proposes a design of robust power system stabilizer (RPSS) based on inverse additive perturbation optimization in an interconnected power system with wind farms. In the design, system uncertainties are represented by the inverse additive model. The robust stability condition is used to form the optimization problem of PSS parameters. The structure of PSS is a conventional second-order lead-lag controller. The genetic algorithm is applied to solve the problem and achieve the PSS parameters. Simulation studies in the two-area four-machine system with wind farms confirm that the damping effect and robustness of the proposed PSS are superior to those of the compared PSS.

H∞ loop shaping-based robust control design of PSS and TCSC for dynamic stability enhancement

In this paper, the robust control design of power system stabilizer (PSS) and thyristor controlled series capacitor (TCSC) for enhancement of power system dynamic stability is proposed. To take system uncertainties such as variations of system parameters, several loading conditions etc., into account, the normalized coprime factorization is used to represent unstructured uncertainties in the system. The Hinfin loop shaping technique is applied to design robust PSS and TCSC controllers. Simulation results in a single machine infinite bus system show that the performance and robustness of the proposed Hinfin controllers of PSS and TCSC are superior to those of the conventional PSS and TCSC.

Autonomous decentralized voltage profile control using multi-agent technology considering time-delay

In a future distribution network, it is difficult to maintain system voltage because a large number of distributed generators are introduced to the system. The authors have proposed an autonomous decentralized voltage control method using power factor control of distributed generators and multiagent technology. In our previous work, the proposed method works efficiently and the voltage profile is maintained with saving the excessive reduction of power factor. The method is consisted of three controls whose control targets are different. And those methods are combined with switching to fit situation. However, such a switching control likely causes the hunting phenomenon in the case that the time-delay with communications among the agents is considered. Then in this study, the proposed method is improved not to include the discrete control. The proposed method is tested in 4-node and 24-node model. The relationship between control performance and time-delay is discussed.

Design of Robust Power System Stabilizer using Genetic Algorithm-based Fixed-Structure H∞ Loop Shaping Control

Abstract This paper proposes a genetic algorithm (GA)-based fixed-structure H ∞ loop shaping technique to design a robust power system stabilizer (PSS). The fixed-structure of designed PSS is a 2 nd -order lead-lag compensator. In the design, system uncertainties are modeled by a normalized coprime factor. The performance and robust stability conditions of the designed system satisfying the H ∞ loop shaping are formulated as the objective function in the optimization problem. The GA is applied to solve an optimization problem and to achieve control parameters of PSS. The performance and robustness against system uncertainties of the designed PSS are investigated in the single-machine infinite bus system in comparison with a conventional PSS and a PSS designed by H ∞ loop shaping. Simulation results show that the robustness and damping effect of the proposed PSS are almost the same as those of the PSS with high-order controller designed by H ∞ loop shaping method.

A study on autonomous decentralized voltage controller in distribution network considering control priority

It is of prime importance to introduce a large amount of distributed generators in order to solve the energy and environmental issue. In distribution network with a large amount of distributed generators, it becomes difficult to maintain the system voltage within an allowable range. Thus, we have developed a new voltage control method using reactive power control of system connection inverter. Especially, the method is based on the autonomous decentralized approach because it will be difficult to treat a large number of distributed generators by a centralized manner. And the method is composed by three control modes and they are switched by voltage change. However, such a switching control method often becomes unstable especially in the case the dead time is included in the control block. Hence, in this paper, we have developed a new method which is based on not the switching control but the continuous control. The autonomous decentralized controller for voltage profile maintenance is proposed and its dynamics are discussed in this paper.

Autonomous Decentralized Voltage Profile Control Method in Future Distribution Network using Distributed Generators

Takao Tsuji1, Tsutomu Oyama1, Takuhei Hashiguchi2, Tadahiro Goda2, Kenji Horiuchi3, Seiji Tange3, Takao Shinji4 and Shinsuke Tsujita4 1Faculty of Engineering, Yokohama National University 2Graduate School of Information Science and Electrical Engineering, Kyushu University 3Transmission & Distribution Systems Center, Mitsubishi Electric Corp. 4Smart Energy Technology Center, Tokyo Gas Co.,Ltd. Japan

A Study on Estimation Method of Reactive Power Control of DGs in Distribution Systems with a large amount of PVs

Abstract To solve the energy and environmental issues, it is expected that a large amount of Distributed Generators (DGs) such as renewable energy are introduced to power systems. In distribution systems with many DGs, the voltage maintenance becomes an important issue due to the reverse power flow. Although reactive power control of DG is effective for the voltage maintenance, the increase of distribution power loss may be caused by such a reactive power control. Additionally, the decrease of active power output of DG may be also required for the reactive power control when its reserve capacity is not sufficient. Thus, it is desired to reduce the amount of reactive power controlled by DGs. On the other hand, in general, distribution systems consist of High Voltage Systems (HVSs) and Low Voltage Systems (LVSs). Most voltage control equipments such as Load Ratio control Transformer (LRT) and Step Voltage Regulator (SVR) are included in HVSs, and DGs are introduced mainly in LVSs. To reduce the reactive power of DGs, the utilization of equipments in HVS is important. However, it is required for system operators to estimate the occurrence of reactive power control of DGs properly. Hence, we developed a new state estimation method of DGs by using sensor information supposing that existing section switchgears will be replaced with new ones that can measure voltage and current using their attached sensors.