# Grid-Friendly Active Demand Strategy on Air Conditioning Class Load
## 1 Introduction  
As the main facility of a building, air conditioning configurations grow quickly, accompanied by increased buildings, which are used by more and more enterprises and groups because they can provide comfortable surroundings, such as air temperature, relative humidity, and cleanliness. However, the maximum load capacity designed on the central air conditioning is according to the local maximum temperature of the working environment by a national standard, but it works mostly at 70% of the full load, which is massive redundancy in the system design [1]. This means that the demand for building energy consumption is improved continuously. Consequently, massive harmonics appear with increased inverter air conditioners (IRC) connected to the grid [2]. The high-order harmonics may cause false triggers on other load equipment, affecting the normal operation and even run out of control [3]. On the other hand, frequency conversion may increase the power loss of transmission lines, dwindle transformer power capacitors, lead to overheating of the equipment, and reduce equipment utilization life and economic benefits [4]. Techniques such as power factor correction rectifiers are also used but do not consider total harmonic processing on the grid [5]. The detection and processing technology of grid harmonics must be studied [6]. Relevant harmonic suppression technology is proposed and improved continuously [7]. When the contradiction is very prominent between power supply and demand, the active demand-side management needs to be promoted, which is a set of flexible and efficient active management schemes to make load demand changes stable. Power quality can be improved under the measurement of the power grid and load parameters, while some policy incentives or technologies are provided as well [8]. Measures for using electricity safely and improving the central air conditioning cooling or chilling water system would be imperative for the host to operate efficiently and reduce energy consumption. Some experts and scholars have proposed innovative operation measures for energy-saving technologies [9]. The authors of literature [10] proposed temporary cut out measures of air condition load when receiving an emergency request from the smart grid or to circumvent the impact of the grid by shutting down the number of the cooling group through a power demand optimization scheme, which did not sacrifice too much comfort. With the development and utilization of new energy, coordinated scheduling of related equipment, the power mismatch between supply and demand of air conditioning load is solved to the utmost extent [11], where new energy is used to achieve the goal, but the impact of air conditioning on the grid is not considered. Of course, to achieve better goals of energy-saving and comfort and minimize the impact of nonlinear load operation on grid quality, LVRT and harmonic control technology are essential. Some experts have proposed some related techniques based on the cost function; active consumption behavior is stimulated to deal with peak load shifts and reduce the unstable operation of the grid [12]. From the perspective of operating characteristics of the air conditioning group load, designing a grid-friendly system composed of harmonic suppression and the LVRT mechanism at the load side is necessary [13]. In addition, the lack of reactive power at peak load can cause voltage fall and even lead to the entire system collapse, which undoubtedly has a great impact on the normal daily life of the people. Therefore, reactive power compensation technology also plays a pivotal role in the safe and stable operation of the power grid [14]. Hence, the goal of active demand-side management is proposed to cater to the energy crisis and alleviate power supply demand, mainly by changing the way of electricity consumption and improving the benefit of terminal electricity, making full use of the functions and operation characteristics of the energy storage system.