Large-scale Temperature Control Load Frequency Control That Takes Into Account Uncertainty

As a kind of grid friendly appliances capable of storing heat/cold energy,thermostatically controlled loads can not only promote the connection of larger-scale renewable energy to the grid,but also increase the capability of frequency modulation in power system.In the past few years,with the intelligent development of the power grid,the proportion of renewable energy in the power grid has been increased.And the intelligent measurement and control equipment have been begun to spread in the power grid.Traditional frequency modulation mainly relies on generator units and the units in the grid used for frequency adjustment,but the smart power grid places higher requirements on the system's frequency modulation and rotating reserve capacity.Based on this,a new kind of system frequency adjustment strategy by using TCLs is proposed in this thesis,which can not only increase the system frequency modulation capacity,but also improve the robustness of system frequency.The specific research contents of this article are as follows:(1)The research background and significance of this thesis are introduced,and the air-conditioning load,that is the most representative among thermostatically controlled loads,is focused as the research object.And this part points out the feasibility of air-conditioning load participating in system frequency adjustment.This part introduces the research status at home and abroad from the aspects of system frequency measurement technology,air-conditioning load control strategy,air-conditioning load modeling.And then the main research contents of this thesis are determined;(2)Based on the second-order equivalent thermal parameter model of the air conditioner,the state-space equations of the air-conditioning loads are established.And the relationship between the indoor temperature and the switching state during the operation of a single air-conditioner is studied.Considering the parameter diversity in the air-conditioning cluster,the Monte Carlo method is used to study the aggregate response characteristics of the air-conditioning cluster,and the parameters of the air-conditioning cluster are analyzed for sensitivity.And then the second-order transfer function model of the air-conditioning cluster is established based on the response characteristics of the air-conditioning cluster.(3)A frequency estimation method for power system based on Kalman filter is proposed.Considering the influence of the harmonics and the transient disturbances,a Kalman filter is designed for the frequency response model.Compared with traditional methods such as zero-crossing detection,the method proposed in this thesis can effectively suppress the influence of interference signals on the frequency measurement,reduce the system response delay time,and improve the accuracy of the system frequency measurement.(4)Based on the frequency response model,a H_?robust controller for the air-conditioning cluster is designed.The closed-loop control strategy is adopted,and the system frequency error is used as a feedback signal.The temperature setting value of the air conditioning cluster is set as the control signal.And the output power of the air conditioning cluster could be controlled by changing the temperature setting value of the air conditioning cluster.In order to improve the robustness of the system frequency,H_?robust controller that includes H_?state feedback controller and H_?output feedback controller is designed.The simulation further verifies the superiority of the controller that designed in this thesis in suppressing power system fluctuations.