Junji Tamura

• Kitami Institute of Technology

A simplified model of a modular multilevel converter (MMC) implemented on a high voltage direct current (HVDC) transmission system is presented in this study for the analyses of steady-state and transient stabilities. The simplified model design’s goal is to reduce the complicated modeling of the MMC circuit as well as the simulation time of the an...

As the introduction of renewable energy sources (RESs) increases, there is a concern that the inertia and synchronizing power of power systems will decrease and the system stability will deteriorate. In particular, if a large-scale wind farm is disconnected from the grid in compliance with the grid code due to a grid fault, the entire grid may beco...

This paper proposes the application of an adjustable speed diesel engine‐driven power plant employing a doubly‐fed induction generator to an isolated small‐scale power system including renewable power sources. This type of power plant can contribute to fast and flexible power balancing regulations under vacillating power supplies such as wind, sola...

In recent years, penetration of renewable energy such as wind power generation has been increasing as measures against the global environmental problems. However, the system stability can be deteriorated when many such power supplies are introduced into the power systems. When a network fault such as a three-line-to-ground fault occurs in the grid...

This paper proposes the application of an adjustable speed diesel engine-driven power plant employing a doubly-fed induction generator to an isolated small-scale power system including renewable power sources. This type of power plant can contribute to fast and flexible power balancing regulation under vacillating power supply such as wind, solar a...

Renewable energy generation systems are promising energy sources; however, they have a problem that they do not have, in general, inertia and synchronous power. A system with low inertial and synchronization forces has low stabilizing capability, and such systems are vulnerable to network fault and can cause large frequency fluctuations. This paper...

In this paper, a detailed model and an average model of an MMC (Modular Multilevel Converter)-controlled Permanent Magnet Synchronous Generator (PMSG)-based direct drive wind turbine are proposed. The models are used to analyze the steady-state and transient characteristics of the grid connectivity study of the wind turbine generator. Configuration...

Wind power generation is a renewable energy source that has been gradually introduced in a variety of applications. However, this power is generated by the wind, and thus it is variable power source that fluctuates according to wind speed variations. This may cause frequency fluctuations in power systems, which can adversely affect the power grid o...

This paper proposes a novel coordinated control method of wind farms (WFs) and hydrogen production systems (HPSs). In a grid-connected system where the WF and the HPS are connected to the grid, the WF can supply the power to the grid, producing hydrogen in the HPS. Moreover, the output fluctuation of the WF can be mitigated when the HPS produces hy...

Renewable energy generation systems are promising energy sources, however, they have a problem that they do not have, in general, inertia and synchronous power. A system with low inertial and synchronization forces has low stabilizing capability, and such systems are vulnerable to network fault and can cause large frequency fluctuations. This paper...

Abstract Large‐scale integration of renewable energy sources (RESs) such as wind power can impact on the existing power system's stability. For example, there is a possibility that the wind farm (WF) cannot be maintained stable and then it is disconnected from the grid when the instantaneous voltage sag caused by a grid disturbance occurs. Moreover...

With the rising penetration of modern converter-based wind farm (WF) into the existing grid system deteriorates system inertia due to reduction of the capacity of conventional power stations which may lead to the frequency instability as well as power system transient instability. In order to solve this concern, this paper presents a robust virtual...

Abstract This paper proposes a novel optimization method for energy storage systems (ESSs) to smooth wind farm output to satisfy the technical requirements and reduce the rated power (rated energy capacity) and charge/discharge loss of the ESS. The state of charge of the ESS operated by the proposed method can be regulated, guaranteeing some constr...

Penetration level of large‐scale wind farm into the existing power system has been increasing significantly which impacts on the transient stability during a network fault. This is because wind farm can be disconnected from the grid according to a grid code of the system when instantaneous voltage drop due to a network fault occurrs in the grid sys...

This paper presents a basic study about the control ability of LNG thermal power plant driven by Motor‐assisting Gas Turbine (MGT) for frequency stabilization of power grid system. An analytical model of the regulation system with assisting motor and gas turbine is developed, and its performance for frequency stabilization under fluctuating power d...

This paper proposes the application of an adjustable speed diesel engine-driven power plant employing a doubly-fed induction generator to an isolated small-scale power system including renewable power sources. This type of power plant can contribute to fast and flexible power balancing regulation under vacillating power supply such as wind, solar a...

The penetration level of large-scale wind farms into power systems has been increasing significantly, and the frequency stability and transient stability of the power systems during and after a network fault can be negatively affected. This paper proposes a new control method to improve the stability of power systems that are composed of large wind...

Wind power generation provides an attractive method for tackling global environmental issues. However, the power grid cannot accommodate large amount of wind farms (WFs) because the fluctuation of WF output degrades the power quality (frequency and voltage) in the power grid. Technical requirements that are related to WF power fluctuation are issue...

Recently, permanent magnet synchronous generator (PMSG) is one of the most familiar type of generator for wind power plant (WPP). Generally, PMSG is connected to grid using back to back converter. During fault period, power imbalance situation can be happened between machine side and grid converter. Thus, the DC-link voltage can be rise significant...

This paper presents a basic study about the control ability of LNG thermal power plant driven by Motor-assisting Gas Turbine (MGT) for frequency stabilization of power grid system. An analytical model of the regulation system with assisting motor and gas turbine is developed, and its performance for frequency stabilization under fluctuating power d...

Penetration level of large-scale wind farm into the existing power system has been increasing significantly, which impacts on the transient stability during a network fault. This is because wind farm can be disconnected from the grid according to a grid code of the system when instantaneous voltage drop due to a network fault occurrs in the grid sy...

Fixed speed wind turbine-squirrel cage induction generator (FSWT-SCIG) based wind farm (WF) is increasing significantly. However, FSWT-SCIG have no frequency control capability, which creates a significant problem on power system steady-state stability. This paper represents a new operational strategy to control frequency of the entire power system...

Penetration level of large-scale wind power into the existing grid has been increasing significantly which impacts on the frequency stability during transient condition. This paper proposes a novel virtual synchronous generator (VSG) control strategy based on PID fuzzy logic control for HVDC transmission line to stabilize the power system during ou...

This paper proposes a novel control approach to reduce the rated power of energy storage system (ESS) in the smoothing of wind power output. Wind power generation causes frequency fluctuations in power systems. Therefore, ESSs are used to absorb the fluctuating power of wind generators. Generally, the controller in an ESS is composed of a first-ord...

This paper addresses a controller for a full converter of variable-speed wind generators (VSWTs) composed of permanent magnet synchronous generators. Conventionally, several proportional-integral (PI) controllers and a phase lock loop (PLL) are used in the full converter for voltage-oriented control. The use of cascaded control loops with PI contro...

This letter proposes an optimization approach to suppress the fluctuation of wind farm (WF) output by using the kinetic energy of variable speed wind generators (VSWGs). A trade-off between the output smoothing and the generator efficiency cannot be directly considered in conventional methods using the kinetic energy of VSWG. We address the issue h...

Due to serious environmental issues in recent years, renewable energy has been focused on all over the world to solve the issues. However, because of indirect characteristics such as variations of solar radiation intensity or wind speeds, the output of power generation utilizing renewable energy becomes unstable. As a result, frequency and voltage...

This paper proposes a coordinated frequency control method for variable speed wind turbines with permanent magnet synchronous generators (VSWT-PMSGs) based offshore wind farm (OWF), which is connected to the main onshore grid through voltage source converter (VSC) based high voltage DC (HVDC) transmission system. The purpose of the proposed system...

This letter presents a consideration on Virtual Synchronous Generator (VSG) control of power system, in which an interpretation of each component of the VSG control, i.e., virtual inertia, virtual damping, and virtual synchronizing power, is developed based on the sustained oscillation theory. Finally the consideration is applied to the HVDC interc...

This paper focuses on a novel variable deloaded operation of variable speed wind turbines with permanent magnet synchronous generators (VSWT-PMSGs) based offshore wind farm (OWF) to maintain primary reserve, which is connected to onshore grid through voltage source converter based high voltage DC (VSC-HVDC) transmission system. A centralized droop...

This paper proposes a method for controlling power flow of High Voltage Direct Current (HVDC) interconnection line in order to suppress the frequency fluctuations of power system with renewable power sources. In this proposed method, by adopting the frequency control with a notch-band pass filter and the balancing control with respect to the energy...

As the penetration level of variable-speed wind turbines continues to increase, characteristics of low inertia and lack of synchronous power of such devices can have a serious impact on the transient stability of a grid. One solution toward stabilizing such a grid with renewable energy sources is to provide additional inertia and synchronizing powe...

This paper presents a new operational strategy for a large-scale wind farm (WF) which is composed of both fixed speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) and variable speed wind turbines with permanent magnet synchronous generators (VSWT-PMSGs) or VSWT with doubly fed induction generators (VSWT-DFIGs). SCIGs suffer gr...

Large integration of renewable energy sources (RESs), such as wind power and solar photovoltaic (PV) plants, into the power systems, impacts the system frequency stability. Normally, a wind farm (WF) and PV system do not provide frequency support because of the uncontrollability of the input energy. Moreover, overall system inertia will be reduced...

The environment friendly blessings of Electrical Vehicles (EV), human beings are becoming extra involved in the use of them alternatively than the usage of mechanical differentials. In electrical vehicles distinct sorts of electrical machines are used among them DFIM is used in this work. The challenging work is to design of a controller as the out...

This paper presents wind turbines cluster system composed of Squirrel Cage Induction Generators (SCIGs) controlled by cluster converter based VSC-HVDC System. The wind turbine cluster systems (multiple clusters) are installed in an offshore wind farm and connected to onshore system through a Voltage Source Converter based High Voltage Direct Curren...

Wind farm (WF) grid codes require wind generators to have low voltage ride through (LVRT) capability, which means that normal power production should be resumed quickly once the nominal grid voltage has been recovered. However, WFs with fixed-speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) have failed to fulfill the LVRT re...

As more and more wind farms are installed in power systems around the world, frequency fluctuations due to output power variations have become a serious problem. Various countermeasures for the problem, such as battery systems, have been investigated. It is very important to evaluate the magnitude of the frequency fluctuations in order to design co...

This letter addresses reduction of the energy capacity of energy storage systems (ESSs) using H∞ control theory. The ESSs have been widely used for smoothing fluctuations of wind generator outputs. We propose a direct and efficient method to design controllers that achieve the minimization considering the trade-off between the energy capacity of th...

This paper proposes a new control system for Adjustable-Speed Pumped-Storage Generator (ASG) to decrease frequency fluctuations of power system with a large amount of wind farm introduced. When a large amount of wind power generation is connected to the power system, it can decrease power quality, e. g., frequency variations. There are some methods...

This paper presents a new method to stabilize fixed speed wind turbine with squirrel cage induction generator (FSWT-SCIG) by using variable speed wind turbine with permanent magnet synchronous generator (VSWT-PMSG) in a wind farm (WF). A fuzzy logic controller (FLC) is proposed in the grid side converter (GSC) of VSWT-PMSG to improve the low voltag...

In recent years, environmental problems have been becoming serious and wind power generation has attracted much attention and been introduced due to its less environmental impacts. Since wind power generation is an unstable power source in which its output fluctuates due to wind speed variations, wind power generator output needs to be smoothed whe...

Micro-wind turbines (MWTs) should have wide range of wind speed. A MWT system can start quickly, but it may be difficult to stop it in low wind speeds. This paper proposes a converter system for variable-inertia and damping-control of MWT. The MWT controlled by the proposed method can be operating even if wind speed decreases momentarily.

This paper proposes a new filter design method that can smooth the wind power generation out- put while keeping the energy capacity and power rating of energy storage system (ESS) small. Wind power gen- eration causes frequency fluctuations in power systems. Therefore, in many cases ESS is needed for smoothing the fluctuations of wind generator out...

Recently, wind power has been attracting much attention because of its positive effect on the global warming. However, wind power generation causes frequency variations in electric power system. Therefore, battery systems for smoothing fluctuations of wind generator output are needed. Though battery control systems with simple low-pass filter (LPF)...

This paper proposes an application of the Model Following Controlled (MFC) PWM inverter to grid-connected variable–speed wind generators using parallel-connected two-generator model in order that the wind generator system controlled by the grid connected MFC PWM inverter can behave as a synchronous generator. Simulation analysis is performed for ev...

Conventional PI controller has overshoot effect at the transient period of the speed response curve. Most of the controllers of Induction Motor (IM) for industrial applications have been designed based on PI controller without consideration of core loss (CL) and stray load loss (SLL). In order to obtain the precise performance of torque as well as...

This paper presents simplified models to represent a grid connected wind farm composed of variable speed wind turbines with Doubly Feed Induction Generator (DFIG) and Permanent Magnet Synchronous Generator (PMSG) for dynamic simulation study. Aim of the simplified models is to diminish the complexity and simulation time of the analysis of grid conn...

Renewable energies having little effect on the global environment have been attracting much attention. Among them, wind power has been introduced widely. However, output power of wind power generation is unstable, and thus it can have bad influence on power system operation. Therefore, control of the introduction or battery system for smoothing the...

This paper provides comprehensive design method of compensator for grid-connected PWM inverters with LCL-filter to supply high quality electric power from distributed generations. The proposed compensator ensures: i) high speed tracking with low distortion and zero steady-state errors for sinusoidal current reference; ii) robust responses against f...

This paper analyses the frequency characteristic of the power system and apply the result to wind farm output smoothing control, which uses the inertial energy of wind power generators and is designed based on a notch filter. It is concluded that the proposed method can control the frequency variations of the power system due to wind generators wit...

A number of offshore wind farms are being in operation in the world. It is important to evaluate the characteristics of losses and output power of a large scale wind generation system like an offshore wind farm. This technical note presents analyses about the output power and loss characteristics of an offshore wind farm composed of permanent magne...

Wind energy is a clean and renewable energy source. The wind generator using the PMSG with grid interface inverter can control its active and reactive power output independently. In addition, it has high performances for fault ride through (FRT) capability, and voltage regulations. Usually, the generator in the grid system has a synchronizing power...

In this paper, a grid connected variable speed wind turbine (VSWT) PMSG integrated with the NaS-type battery energy storage system (BESS) is modeled in the real-time digital simulator (RTDS) to analyze the performance in a real system. This study is also a part of the future power hardware-in-loop (PHIL) test; therefore, individual components are m...

This paper proposes a new method for evaluating characteristics of frequency and voltage fluctuations of power system in which wind generators are installed. In this paper, a new method based on the transfer function models for frequency response and voltage responses of the power system is developed, from which voltage response of each node in the...

As a number of wind power generation systems have been installed in power systems in the world, frequency fluctuations due to output power variations from wind farms have become a serious problem. Battery systems have been studied for smoothing the output variations and decreasing the resulting frequency fluctuations. Among these studies, efficient...

Wind energy is a clean and renewable energy source. A wind generator using a PMSG can operate in maximum power point tracking (MPPT) mode. In addition, it has capabilities for fault ride through (FRT), active power and reactive power control issues, and voltage regulations. We have already proposed a model following controlled PWM inverter that exh...

As a number of wind power generation systems have been installed in power systems in the world, frequency fluctuations due to output power variations from wind farms have become a serious problem. Various countermeasures for the problem such as battery systems have been investigated. It is very important to evaluate the magnitude of frequency fluct...

This letter presents a new method for calculating frequency and voltage fluctuations of power system with wind generators installed. The new method is based on the transfer function models for frequency and voltage responses, from which voltage response of each node in the power system as well as the frequency response can be obtained easily and qu...

As many wind farms have been installed in power systems in the world, frequency fluctuations due to output power variations have become a serious problem. Various countermeasures for the problem such as battery systems have been investigated. It is very important to evaluate the magnitude of frequency fluctuation for designing compensating systems....

In this paper dynamic behavior analysis of offshore wind farm with permanent magnet wind generators is performed. A simplified model of the permanent magnet synchronous generator is proposed to implement in PSCAD/ EMTDC in order to reduce the complexity of the analysis of a large offshore wind farm and the long simulation time. The performance of s...