Climate vulnerability index fluctuation: a case of Iran

Climatic fluctuations have severe effects on water and soil resources and economy as a whole. It is hence important to study the fluctuations of climatic parameters in different regions in order to recognize the source and type of parameter that have led to fluctuating climatic parameters. To achieve this goal, the current study attempts to address the following issues: what are the different sources of fluctuations in climate parameters? Do different regions have the same degree of vulnerability and what is the most fluctuating parameter in each region? To answer these questions, the study suggests climate vulnerability index fluctuation. Calculating the index requires data provided by weather stations, so 115 weather stations were divided into 12 climatic zones based on the availability of data. This index considered permanent and frequent temperature, precipitation, storm and aridity shocks. The results indicated that the maximum rank of index has occurred in hot semi-mountainous and very hot desert. Also, temperature fluctuation was the major factor in five regions, whereas wind fluctuation was the major factor in three regions. Generally, the northern and western parts of the country experienced minimum climatic changes. Moving towards southern regions of the country, more climatic changes were observed.

Vertical wavenumber spectra of three-dimensional winds revealed by radiosonde observations at midlatitude

By applying 12-year (1998–2009) radiosonde data over a midlatitude station, we studied the vertical wavenumber spectra of three-dimensional wind fluctuations. The horizontal wind spectra in the lower stratosphere coincide well with the well-known universal spectra, with mean spectral slopes of −2.91 ± 0.09 and −2.99 ± 0.09 for the zonal and meridional wind spectra, respectively, while the mean slopes in the troposphere are −2.64 ± 0.07 and −2.70 ± 0.06, respectively, which are systematically less negative than the canonical slope of −3. In both the troposphere and lower stratosphere, the spectral amplitudes (slopes) of the horizontal wind spectra are larger (less negative) in winter, and they are larger (less negative) in the troposphere than in the lower stratosphere. Moreover, we present the first statistical results of vertical wind fluctuation spectra, which revealed a very shallow spectral structure, with mean slopes of −0.58 ± 0.06 and −0.23 ± 0.05 in the troposphere and lower stratosphere, respectively. Such a shallow vertical wind fluctuation spectrum is considerably robust. Different from the horizontal wind spectrum, the slopes of the vertical wind spectra in both the troposphere and lower stratosphere are less negative in summer. The height variation of vertical wind spectrum amplitude is also different from that of the horizontal wind spectrum, with a larger amplitude in the lower stratosphere. These evident differences between the horizontal and vertical wind spectra strongly suggest they should obey different spectral laws. Quantitative comparisons with various theoretical models show that no existing spectral theories can comprehensively explain the observed three-dimensional wind spectra, indicating that the spectral features of atmospheric fluctuations are far from fully understood.

A Study on Multistage Coordination and Control Strategy for JiBei Grid Considering Wind Power Fluctuation

The establishment of independent control area for JiBei grid will improve the flexibility of regulation for local units, and absorb more wind power and other clean energy. However, due to the high proportion of wind power capacity and the fluctuation and intermittent of wind power, it presents a challenge to the power supply safety. In this paper, based on the prediction of regulation demand and regulation speed in different time scales, dynamic hierarchical control method is proposed. Several strategies of hierarchical control under the emergency of steady climbing, reverse and fluctuations are established. Hence, it improves the capacity of power supply safety and the proportion of wind absorption. Finally, based on the measurement of characteristics of wind fluctuation, the value of reserve capacity in different control levels is calculated.

A Study of Wind Power Inverter Operating in Grid-Connected and Stand-Alone Mode

Wind turbine system (WTS) is a representative distributed power generation (DG). Establishment of WTS model and control strategies is of important practical significance. One critical field is the research of inverter system. It should be operated in stand-alone (SA) or grid-connected (GC) mode. The purpose of this thesis is to establish simulation platform of WTS inverter control model in Matlab/Simulink environment, which includes two typical DG control strategies, PQ and V/f. The wind fluctuation makes inverter output power harder to follow wind turbine (WT) power. In GC mode, PQ strategy was adopted to balance inverter output power and WT generated power. In SA mode, V/f strategy was applied to keep emergency load voltage stable. The bidirectional smooth transitions between SA and GC mode were well accomplished. Simulation proves the model can survive grid failures or load shedding. The study can be used in research of DG operation control.

Dynamic Analysis of Transient Voltage for Distribution Network with the Consideration of Wind Power

Distributed wind power will bring great impact on transient voltage of distribution network. Based on the characteristics of distributed wind power, this paper presents a doubly-fed induction Generator with four wind speed model and Crowbar protection model in DigSILENT/PowerFactory. The analysis is carried out for a test distribution system representative of the Benchmark 20kv grid. Firstly, this paper respectively provide simulation results showing the effects of distributed wind power on the dynamic voltage in wind fluctuation and a faulted system. Then, a static synchronous compensator (STATCOM) is used to improve the voltage profile of the distribution system.