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In recent years, the amount of distributed generators in the power grid has increased. Most of these distributed generators are renewable energy facilities using wind turbine generators or photovoltaic power systems. The increase in distributed generators is mostly due to environmental issues, growing concern of resource depletion, and economic benefits for residents and homeowners. Along with the increase in distributed generators, all-electric apartment buildings and residential homes with electric vehicles are on the rise. This trend is beneficial for both the environment and the residents; however, the fluctuating power from renewable energy sources and unstable loads causes fluctuations in grid frequency and distributed voltage which become problematic. This paper presents a methodology to control system frequency and distributed voltage using distributed controllable loads such as the heat pump water heater (HP) and large capacity batteries such as those of the electric vehicle (EV). By applying a power consumption controller using decentralized control for heat pump water heaters and droop characteristics for batteries, fluctuations of grid frequency and voltage are suppressed to a desired value. In order to verify the effectiveness of the proposed system, MATLAB/Simulink is used for simulations. [ABSTRACT FROM AUTHOR]

In order to solve the problems of global warming and depletion of energy resource, renewable energy systems such as wind generation are getting attention. However, wind power fluctuates due to variation of wind speed, and it is difficult to perfectly forecast wind power. This paper describes a method to use power forecast data of wind turbine generators considering wind power forecast error for optimal operation. The purpose in this paper is to smooth the output power fluctuation of a wind farm and to obtain more beneficial electrical power for selling. [ABSTRACT FROM AUTHOR]

This paper deals with controlling the output power smoothing of a wind energy conversion systems (WECS) by using permanent magnet synchronous generator (PMSG). It uses the inertia control of the wind turbine and DC-link voltage control. The PMSG is connected to the grid through a generator-side converter and a grid-side inverter based on AC-DC-AC methods. The generator-side converter is used to control the torque of the PMSG while the grid-side inverter is used to control DC-Link voltage and grid voltage. Fuzzy logic is implemented to determine the torque command by using inertia of wind turbine. The inputs of the fuzzy logic are given by the operating point of the rotational speed of the PMSG and the difference between the wind turbine torque and the generator torque. From the proposed method, the generator torque is smoothed and kinetic energy generated by the inertia of the wind turbine is used to smooth the power fluctuations of PMSG. Also, a stable operation of WECS is achieved during the system fault by using the chopper circuit in the DC-link circuit. The output power smoothing is achieved with stability and low cost. The effectiveness of the proposed method is verified by the numerical simulations. [ABSTRACT FROM AUTHOR]

This paper presents the operation under fault and protection of multi DC smart grids connected to the DC transmission line. The smart grid consists of wind turbine and photovoltaic generators, controllable loads, generator side and grid side inverters. The voltage stability of the DC bus voltage is attained by applying the power consumption control of controllable loads, the power control of grid connected converter and power control of renewable plants. On the other hand, the fault protection for short-circuit and low resistance ground fault at the DC transmission line was sighted. Simulation results based on PSIM are provided to demonstrate the effectiveness of the system. [ABSTRACT FROM AUTHOR]

Currently, there are several published reports on wind farms (WFs) for controlling output power by using pitch angle control. In addition, to reduce the adverse effects of frequency deviations, battery energy storage systems (BESSs) are introduced to small power systems. In this context, this paper presents a frequency control method by the WF and the BESS using load estimation. The load is estimated by a disturbance observer. The frequency deviations in low and high frequency domain are reduced by the WF using pitch angle control and battery charge/discharge, respectively. By using the proposed method, the reduction of the rated capacity of the BESS is possible. Furthermore, for the pitch angle control system of each WTG in the WF, generalized predictive control (GPC) is applied to achieve robust control performance. The effectiveness of the proposed method is verified by numerical simulation. [ABSTRACT FROM AUTHOR]