Eitaro Omine

Coordinated control of battery energy storage system and diesel generator for isolated power system stabilization

Nowadays, renewable energy such as wind turbine generator and photovoltaic system are introduced in power system. Output power fluctuations of these generation systems will result in frequency deviations and terminal voltage fluctuations. In order to overcome these problems, battery energy storage system is used for frequency and voltage control. However, it needs large capacity of battery system which increase the equipment cost. In this paper, we propose the coordinated control strategy between diesel generator and battery system for reducing the equipment cost of battery, inverter capacity and storage capacity. The proposed control system incorporates Hinfin control theory which enables intuitive controller design in frequency domain. The effectiveness of the proposed control system is validated by simulation results in MATLAB.

Frequency control strategy for parallel operated battery systems based on droop characteristics by applying H ∞ control theory

Stand alone ac power supply system like that is designed for isolated islands is subjected to large frequency and voltage fluctuations caused by power deviation of wind turbine generator and load demand. An autonomous decentralized frequency control system of parallel operated decentralized generators based on droop characteristic is presented in this paper. The conventional droop control methods proposed in past researches exhibit slow and oscillating dynamic responses. Moreover, the conventional droop control is affected by measurement noise when the fast controllability of the system is emphasized. This paper proposes the improved droop control system for load sharing of multi operated decentralized generators by applying H∞ control theory, improving transient response of droop control and robustness against measurement noise and parameter variations. Simulation results validate the effectiveness of the proposed control system.

Full state feedback digital control of WECS with state estimation by stochastic modeling design

With increased structural flexibilities of modern wind energy conversion systems (WECSs), drive-train torsional oscillations due to high wind disturbances can be hazardous to power systems. It is particularly important to design control schemes that properly account for the flexible modes of the turbine, and maintain stable closed-loop behavior of the WECS. To capture the essential features of the problem for controller design, the approach in this paper entails modeling the various WECS subsystems: the wind speed as a stochastic process generated by an autoregressive moving average (ARMA) model and the drive-train as a multimass system with an elastic shaft linking the turbine with the asynchronous induction generator (IG). The proposed control paradigm is based on the linear quadratic Gaussian (LQG) to damp these undesired oscillations, and utilizes only one measurable feedback signal: generator speed deviation. An optimal state estimator provides a good estimation for the aerodynamic torque thereby determining the target trajectory to which the controlled system should converge. The objective is to optimize aerodynamic efficiency in low to medium winds, and add damping to the drive train at above-rated wind speeds. A pitch controller ensures the maximum power constraint is respected by preventing rotor overspeed.

Stabilization Control for Remote Power System by Using H Decentralized Controllers

Generating power of wind turbine varies in proportion to the cube of wind speed, so they cannot supply constant power and this causes frequency and voltage fluctuations. This paper presents a methodology for controlling grid frequency, hydrogen volume and terminal bus voltage. This system consists of diesel generator, wind turbine and load. Aqua electrolyzer and fuel cell are installed in order to control grid frequency, terminal voltage and hydrogen volume. By applying Hinfin control, frequency, voltage fluctuations and hydrogen volume control are achieved. Hinfin decentralized controllers are designed and installed for diesel generator, aqua electrolyzer and fuel cell in series. In order to verify the effectiveness of the suggested system, MATLAB/SIMULINK is used for simulations.

Torsional torque suppression of decentralized generators using H ∞ observer with parameter identification

The output power fluctuation of renewable energy power plants such as wind turbine generator and photovoltaic system result in frequency deviation and terminal voltage fluctuation. Furthermore, these power fluctuations also affect the turbine shafting of diesel generator and gas-turbine generators which are the main power generation systems in isolated islands. This paper presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of the torsional torque is difficult technically, and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using developed H∞ observer with parameter identification system. The simulation results validate the effectiveness of the proposed control system.

Steady-state and transient dynamic response of grid-connected WECS with asynchronous DOIG by predictive control under turbulent inflow

Strong growth figures prove that wind is now a mainstream option for new power generation. However, wind stochasticity results in fluctuations in output power as well as undesirable dynamic loading of the drive-train during high turbulence. To provide industry with the support it needs to develop technologies capable of cost-effective operation, advanced power electronic components have become increasingly necessary. These yield robust, adaptive digital controllers for optimal performance of the wind energy conversion systems (WECSs). This paper presents a model-based predictive control (MBPC) strategy for the field oriented control of a double output induction generator (DOIG). The control region is defined over two wind profiles: average wind speeds below and above equipment rating, subject to assigned constraints of the maximum allowable system frequency fluctuations and the power limit of the wind energy conversion system (WECS). To meet the objectives of maximizing energy capture and alleviation of drive train fatigue loads, controller design is based on performability models of the WECSpsilas components. Simulations verify the proposed paradigm achieves regulation of torsional dynamics while maintaining optimal operation.

Functional modeling for intelligent controller design for MW-class variable speed wecs with independent blade pitch regulation

Recent advancements in size and technology of wind turbines require sophisticated control systems to effectively optimize energy conversion and enhance grid integration. This article investigates output power stability of a WECS in a highly fluctuating wind environment. The aim is advanced controls development to identify and assess the critical loads and instabilities, and improve the dynamic response and quality of power output of the wind energy conversion system (WECS). Based on a performability model, a control strategy is devised for maximizing energy conversion in low to medium winds, and maintaining rated output in above rated winds while keeping torsional torque fluctuations to a minimum. Control is exercised via individual blade pitch control as well as a self-tuning regulator (STR) for generator torque control. The fundamental philosophy behind the proposed control strategy for the wind turbine coupled to an asynchronous doubly-fed induction generator (DFIG) is general and can be easily extended to other WECS configurations.

Control Strategy of Torsional Torque Suppression of Decentralized Generators with Parameter Identification System

Abstract The output power fluctuation of such renewable energy power plants as a wind-turbine generator and a photovoltaic system results in frequency deviation and terminal voltage fluctuation. Furthermore, these power fluctuations also affect the turbine shafting of diesel generator and gas-turbine generators, which are the main power generation systems in isolated islands. This article presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of torsional torque is difficult technically, and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using a linear quadratic regulator observer with a parameter identification system. The simulation results validate the effectiveness of the proposed control system.

Robust Observer Design for an Isolated Power System with Model Uncertainty using H ∞ -Norm

The output power fluctuations of renewable energy power plants such as wind turbine generators and photovoltaic systems result in frequency deviations and terminal voltage fluctuations. Furthermore, these power fluctuations also affect the turbine shaftings of diesel generators and gas-turbine generators which are the main power generation systems on isolated islands. Therefore, it is important to achieve torsional torque suppression. Since the measurement of torsional torque is technically difficult, and there is an uncertainty in the mechanical constants of the shaft torsional system. This paper presents an estimation system that estimates torsional torque by using a developed H1 observer. In addition to the above functions, the proposed shaft torque observer incorporates a parameter identification system that aims to improve the estimation accuracy. The simulation results validate the effectiveness of the proposed H1 observer and the parameter identification.

Torsional torque suppression of decentralized generators using LQR obsever with parameter identification

The output power fluctuation of renewable energy power plants such as wind turbine generator and photovoltaic system result in frequency deviation and terminal voltage fluctuation. Furthermore, these power fluctuations also affect the turbine shafting of diesel generator and gas-turbine generators which are the main power generation systems in isolated islands. This paper presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of torsional torque is difficult technically, and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using LQR observer with parameter identification system. The simulation results validate the effectiveness of the proposed control system.