Kenta Koiwa

Power system frequency control with dead band by using kinetic energy of variable speed wind power generators

This paper proposes a new method to suppress frequency variations of power system with large amount of wind power installed by using the kinetic energy of the wind power generators. In recent years, environmental problems have been becoming serious and wind power generation with less environmental impacts has attracted much attention and introduced. Since wind power generation is an unstable power source in which its output fluctuates due to wind speed variations, wind power generator output must be smoothed when supplied to the power system. This paper proposes a control method to suppress the power system frequency variation by increasing or decreasing the wind power generator output using its kinetic energy only when the frequency variation exceeds specified threshold value. It is shown in the paper that the new method makes it possible to decrease the loss of wind generator output as well as suppress the frequency variation than the conventional methods.

Frequency characteristic analysis of power system and its application to smoothing control of wind farm output

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 with small power loss.

Comprehensive design of linear control systems and its application to PWM inverters

A comprehensive design scheme of SIMO linear control systems is presented and applied to sinusoidal tracking of PWM inverters. Considering the design scheme, we deal with realizable transfer functions of control systems in general SIMO feedback configuration. As a result, a necessary and sufficient condition for transfer functions of achievable closed-loop maps is obtained. Based on the condition, we introduce a novel design scheme of linear control systems. Compared to conventional design scheme such as ß-parameter approach, the proposed one enables numerical optimization with a prescribed order of controller. Moreover, various multi-objective control requirements can be dealt with step by step in order of precedence. An illustrative example of the proposed design scheme applied to sinusoidal tracking of PWM inverters is investigated.

Sensorless virtual resistance damping method for grid-connected three-phase PWM converter with LCL filter

Three-phase PWM converter is commonly connected to utility grid through L or LCL filter to remove grid current harmonic components. LCL filter has many advantages compared with L filter. However, resonance at high frequency caused by the LCL filter may lead stability problem. Passive damping method (PD) or active damping method (AD) is used to solve this problem. PD brings the additional loss due to damping resistor. On the other hand, virtual resistance damping method of AD, in general, needs additional sensor. Therefore, this paper proposes sensorless virtual resistance damping method for grid-connected three-phase PWM converter with LCL filter.

Stand-alone hydrogen production system composed of wind generators and electrolyzer

Wind power generation as well as hydrogen energy have attracted much attention as a solution for solving the energy problem in the future. Though many strategies for the operation of a grid-connected wind farm have been proposed, operation method of stand-alone wind farm has not been studied sufficiently so far. There are many places with good wind condition but without connectable grid, where stand-alone wind farm can be very attractive. This paper proposes a stand-alone hydrogen production system composed of wind generators and hydrogen electrolyzer.