Installed capacity of Renewable energy sources (RES), especially variable renewable energy sources (VRE) such as photo voltaics and wind turbine, in remote islands is rapidly increases to reduce generation cost. Several example of VRE output power fluctuation compensation by use of demand side equipment in remote island power grid are introduced in this report.
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 Current (VSC-HVDC) transmission line. A control scheme of cluster converter and VSC-HVDC converter systems is developed so that power production by SCIGs can be delivered to the onshore system effectively. In this study dynamic behavior of the wind turbines has been investigated by simulation study performed by using PSCAD/EMTDC for fluctuating wind speed and short circuit fault. Simulation results show that the proposed cluster system composed of SCIGs has high performance under transient and steady state conditions.
A large blackout in 2006 because of two-circuit failure on 275kV transmission line will be well remembered. One of successful methods against such blackout is to maintain the islanded system stable. However, the stability is doubtful when renewable energy highly penetrates and as the result much amount of synchronous generator stops. There are two issues. One is frequency deviation due to demand-supply imbalance. Another is instability due to shortage of voltage support capability of the islanded system. The phenomenon is fast and therefore serious, if it can be exists. As the third issue of islanded system, frequency instability of hydro islanded system. However, it will be quite rare to appear a large islanded system only by hydro power. Usually oscillatory instability, in which small generator's rotor angle swing gradually grows, appears in loosely interconnected large system, which is divided into two groups, but is not remarkable in tightly interconnected local islanded system. However, another oscillatory instability can exists. The paper theoretically clarifies the phenomenon; identifies dominant factors of the phenomenon; verifies the theory by simulation; and make a caution for preparing high renewable energy integration.
When a small boat, which made of insulation material such as Fiber Reinforced Plastic (FRP) or wood, is struck by either direct or nearby lightning, a surge current flows in a power cable or a grounding wire on the boat. The current due to a direct lightning strike flows out from grounding electrodes for a radio or the other electrical equipment. On the other hand, if the boat is struck by nearby lightning, the current flowing in seawater invades into the equipment on the boat via the grounding electrodes. To reduce the current flowing in the circuit on the small boat, an installation of a ring electrode around the hull of the boat is proposed in this paper. For the direct lightning, the countermeasure can reduce the current flowing out from the grounding electrode for the radio and the other equipment by a connection of the electrodes with the appended ring electrode. The ring electrode bypassing the lightning current. Even if the lightning strikes a surface of seawater nearby the boat, a few percent of the lightning current invades into the boat. The proposed countermeasure also reduces the invading current by about 60%.
The experiments were conducted to verify the impact on the healthy system by the short-circuit accident in the 400VDC power supply system, which is expected to be introuced in the data center and communication building. Along with the short-circuit current breaking, transiently voltage fluctuation occurs. By comparing the existing standards of ICT equipment and result of the experiment, the wiring conditions that enable the ICT equipment to continue the operation during the fluctuation were derived. In addition, taking into account of the actual design of the wiring, specifications of instantaneous voltage drop and over voltage withstand for 400VDC class ICT equipment should have was newly derived.
Power generating characteristics of seed-free linear shaped Faraday type and disk shaped Hall type MHD generators are examined by two-dimensional numerical simulation with changing the inlet ionization degree. A liner shaped Faraday type generator can get stable and high power output at high inlet ionization degree. The net enthalpy extraction ratio, however, is reduced owing to the increase in the required preionization power. At low inlet ionization degree, on the other hand, ionization instability occurs and the enthalpy extraction ratio decreases. A disk shaped Hall type generator can get high net enthalpy extraction ratio even at low inlet ionization degree under a low preionization power. The net enthalpy extraction ratio decreases for an excessive inlet ionization degree because of a strong MHD interaction.
The test voltage function or k-factor was newly introduced in IEC 60060-1: 2010. With the k-factor combined with base curve technique, lightning impulse parameters have been evaluated much easily and stably than with the old method defined in IEC 60060-1: 1989. Now there has been a report in IEC TC 42 committee that front time evaluated from recorded curve of a smooth waveform at the end of a long measuring cable becomes much larger by IEC 60060-1: 2010 definition than with IEC 60060-1: 1989 description. Authors could not only confirm this phenomenon and found reasons to cause but also propose a technique to circumvent this difficulty. In the paper, details of the counter measures and arrangement of the measuring system, which eliminates erroneous front time evaluation, are introduced.
The large-scale installation of Wind Power into the power system is planned in order to realize security, relief and sustainable society. In this paper, a new output scenario generating method for stochastic scheduled operation of wind farm is proposed. This method can take account of autocorrelation of time series and generate scenarios which are similar to observed data of wind farm output.