# The Optimal Dispatch of a Power System Containing Virtual Power Plants under Fog and Haze Weather
###### Abstract  
With the growing influence of fog and haze (F-H) weather and the rapid development of distributed energy resources (DERs) and smart grids, the concept of the virtual power plant (VPP) employed in this study would help to solve the dispatch problem caused by multiple DERs connected to the power grid. The effects of F-H weather on photovoltaic output forecast, load forecast and power system dispatch are discussed according to real case data. The wavelet neural network (WNN) model was employed to predict photovoltaic output and load, considering F-H weather, based on the idea of \"similar days of F-H\". The multi-objective optimal dispatch model of a power system adopted in this paper contains several VPPs and conventional power plants, under F-H weather, and the mixed integer linear programming (MILP) and the Yalmip toolbox of MATLAB were adopted to solve the dispatch model. The analysis of the results from a case study proves the validity and feasibility of the model and the algorithms. f 2016 871  
The Chinese government has attempted several measures in the long run to restrict the impacts of F-H: introducing a variety of energy-saving equipment and employing new energy-saving technology to reduce the consumption of fossil fuels, substituting electricity for coal in industrial manufacturing to effectively control pollutant emissions and transforming the emissions technology of TPPs and other industries to realize solidified treatment of air pollutants. In addition, several emergency measures are taken when the F-H condition is serious. For instance, to ensure the smooth operation of the military parade in Beijing that commemorated the 70 th anniversary of the victory in the Anti-Japanese War, the government took several temporary control measures with regard to public traffic, industries and construction sites to reduce the emission of air pollutants. The above measures were highly effective and brought the \"blue sky of military parade\" to Beijing temporarily. The mean concentration of PM2.5 in Beijing was 17.8 \(\mu\)g/m\({}^{3}\), and the air quality was excellent (\(L_{\text{AQI}}=1\)) from 20 August-3 September 2015. However, Beijing was covered by F-H again after the anniversary. During the period of Chinese National Day holidays, the Air Quality Index (AQI) values in Beijing from 1-3 October 2015 were all lower than 60, whereas the air condition deteriorated from 4-7 October 2015, and the largest AQI value reached 335. Therefore, a long-term method is urgently needed to overcome F-H weather. The environmental benefits of a strategy of sustainable development have been emphasized, and clean energy that is abundant and renewable will gradually replace conventional fossil energy. Therefore, the permeability of distributed energy resources (DERs), which consist of distributed generation (intermittent power generation, controllable power generation, _etc._), electrical energy storage (static energy storage, electric vehicles, _etc._) and demand response resources (controllable load, efficiency resources, _etc._), would increase. The demerits of DERs, such as multiple and changeable output characteristics, various scales, decentralization, uncertainties, difficulties of distribution networks to absorb DERs, lower automation levels, outdated control strategies of dispatch and lack of interaction and communication between the power grid and consumers [3], greatly restrict the popularity of DERs. More control power is needed if a large number of DERs are connected to the grid directly, which would cause some complexity in the system control. A micro-grid that aggregates scattered DERs to form a single controllable unit could centrally control various DERs and weaken the impact on system stability [4; 5]. However the micro-grid is strict in its configuration and cannot be disassembled and reassembled at will. The objective of the micro-grid in early studies focused on the local application of DERs, which had some limitations on the large-scale application of scattered DERs.