Active Participation Of Air Conditioners In Power System Frequency Control Considering Users’ Thermal Comfort

Traditionally, the frequency regulation is implemented by generation side, including the primary frequency control and the secondary frequency control. Generally, these two types of control can improve the frequency quality in the time-scale of seconds to minutes. However, with the change of the generation structure, which is the increase of the nuclear and intermittent energy sources, the ability of providing reserve capacity in generation side has decreased. Besides, with the environmental and economical costs to be accounted for, reserve provision from generation, especially fossil-fueled generators, will be much more expensive. Therefore, relying solely on the generation side is not sufficient for frequency control. Supplementary to the generation side, resources from the load side have the potential to provide low cost and fast responsive regulation.As a typical thermostatically controlled load, the proportion of air conditioners in peak power grows year by year. Consequently, air conditioners can take an active role in frequency control. Besides, air conditioners are capable of providing reserve by adjusting the temperature setting point without compromising users’ utility because of their inherent thermal capacity. For air conditioners, the end-use utility is mainly evaluated by users’ thermal comfort. Therefore, fuzzy mathematics is utilized to establish membership functions for various temperature and relative humidity values. A decentralized control design for frequency regulation is proposed, with which users can adjust the temperature setting points of air conditioners according to thermal comfort rank and frequency deviation. Experiments are conducted to verify the effectiveness of the proposed fuzzy rule based decentralized control design for frequency regulation.Though the power demand of an air conditioner is not enough to influence the imbalance between generation side and load side, the power reduction of a large number of air conditioners in the study will mitigate the decrease of frequency. On the basis of a third-order model describing the states of air conditioners, Monte Carlo simulation method is adopted to obtain the aggregation power demand of air conditioners in control. Real and reactive power of the aggregation of air conditioners will change with time in response to frequency dynamics. Consequently, the relationship between the injection current and bus voltage is nonlinear. The aggregation of air conditioners can neither be treated as ZIP model nor induction motors. A structure preserving model is applied to multi-bus power system, with air conditioners are placed at corresponding load buses. An inner-outer iteration scheme is designed to solve power system dynamics. The inner iteration process is to solve voltage variables at the load bus with the aggregation of air conditioners. The outer iteration process is for solving dynamics of generating units and air conditioners.Quantity of data are transferred and processed during the implementation of load control. To describe the limit of information communication technology, a cyber physical system (CPS) interactive simulation platform is designed. OpenDSS is adopted for the physical system simulation, NS-2 is adopted for cyber system simulation, MATLAB is utilized as the control center for time synchronization and control strategy. To examine the influence of information communication technology, simulations are conducted on the IEEE 13-bus distribution system.