# Grid-Friendly Active Demand Strategy on Air Conditioning Class Load
## 2 Active Demand Strategy Design  
Based on experience, the factors affecting human comfort include atmospheric temperature, humidity, air pressure, illumination, wind, clothing, and individual differences. Since not all indicators have equal impacts on human comfort, an improved non-dimensional regression model is proposed by coefficient parameters method, where several main factors are selected, and coefficient and modified parameters are designed according to their differences in the impact on human comfort [15; 16]. Among the meteorological factors that affect the comfort level of the human body, the temperature is in the first place, next is humidity, followed by wind direction and wind speed. To make air-conditioned meet the requirements of human comfort, the water system, wind system, and cold and heat source must be coordinated and properly controlled. Generally, the following objectives such as air quality (freshness), comfort (temperature, humidity, and ventilation), and energy-saving (minimum power consumption) must be taken into account in air conditioning control. Thus, the multi-objective working model should be expressed as Formula (1). \[\left\{ \begin{array}{c}ssd=(1.818t+18.18)(0.88+0.002f)+(t-32)/(45-t)-3.2\sqrt{v}+18.2 \\ \text{OPT(RAF)}\\ \text{Min}(\sum\ W_{i})\end{array} \right. \tag{1}\]  
Among them, \(ssd\) is the human body comfort index; the formula definition of comfort level is not the same according to a different classification. \(t\) is the average temperature, \(f\) is the relative humidity, and \(v\) is the wind speed. The comfort formula is an empirical formula based on long-term statistics of the project. \(\sum\ W_{i}\) is the sum of energy consumed by motor drag systems. \(W_{i}\) is the energy consumed by the pump and the fan. RAF is an abbreviation of relative air freshness; the best comfort index is 59-70 and the human body feels the most comfortable and acceptable. In the selecting process of many parameters, the average temperature \(t\) and relative humidity \(f\) can be freely selected according to the actual situation, and the wind speed \(v\) is determined according to the control demand. From the perspective of meteorology, the human body feels more comfortable when the temperature is between 18 and 20 Celsius and the relative humidity is between 50% and 60%. At present, the human body comfort index adopted in Jiangsu Province has nine grades from \(-4\) to 4, of which level 0 is the most comfortable and most acceptable [17]. It can also be seen from the formula that the air conditioning operation is mainly the coordination work of the fans, pumps, compressors, and heaters. Therefore, in the same external environment, the higher is the human comfort control index, the higher is the energy consumption of air conditioning equipment. The air conditioning group load simulation with typical nonlinear characteristics motors group as shown in Figure 1.  
The left side of the figure shows the power quality monitor of the current harmonics and voltage distortion caused by the group load operation of the air conditioning system. The middle is the inverter system that supplies power to the air conditioning system. The right part represents the load of the air conditioning group. It includes a variable water volume system, a variable air volume system, and a cold-heat source system. They are respectively composed of different motor machines, yet the sensors and data analysis unit in the figure are designed to realize active energy monitoring. Based on the analysis of load operation characteristics, a friendly scheduling design on the energy-saving operation is carried out. The hardware functional modules included in the overall active demand strategy are made of harmonic suppression and governance, LVRT control and reactive power compensation, peak sh  
Figure 1: The module structure of active demand management. The \(Z\)-type filter and harmonic prevention circuit are designed on the DC bus side between the power supply and load.