Coordination Control Of Reactive Power And Voltage Of A Wind Farm Based On Model Predictive Control

As an environment-friendly new energy power generation technology,wind power generation technology has broad development prospects.At the same time,due to the richness of wind energy resources,it has been developed and utilized on a large scale.However,with the large-scale integration of wind power,many challenges need to be faced by the grid,one of which is the coordinated control of reactive power and voltage.The randomness and fluctuation of wind energy resources,the change of load size and the fault of transmission line are all the causes of voltage fluctuation.Therefore,the stability of control voltage,especially the stability of parallel point voltage,has always been a research hotspot.The main method to control voltage stability is reactive power compensation.There are many kinds of reactive power compensation devices in power grid and their characteristics are different.Therefore,it is necessary to select appropriate reactive power compensation devices.Also,the response characteristics of reactive power compensation devices with different time scales increase the difficulty of reactive power optimization and voltage control.Based on this background,the mathematical model of predictive control is established to coordinate the control of reactive power compensation device and the voltage stability of connection point.Based on the model predictive control(MPC)technology,the coordinated control of reactive power and voltage of wind farm is studied.Firstly,the principles and mathematical models of several reactive power compensation devices is introduced in this paper.Furtherly,in order to select the appropriate reactive power compensation equipment,the application scenarios and characteristics of each device are analyzed,and the static var generator(SVG)and wind turbine are selected as the research objects.Then the relationship between reactive power and voltage is deduced,and the calculation method of sensitivity between reactive power and voltage is introduced.The overall mathematical model and objective function of coordination control of reactive power and voltage of wind farm are established.Next,the model predictive control algorithm is introduced in detail.At the same time,according to the above mathematical model,PI controller,model predictive controller and incremental MPC controller are designed.MPC can detect the change trend of node voltage in advance and optimize the voltage control in real time.Simulation results show that MPC has a better performance and a shorter response time than PI control.It can effectively control the node voltage within the allowable range,and its node voltage deviation is also smaller,which is more conducive to the realization of economic operation of power grid.Finally,considering that in the actual operation,the load change,wind speed fluctuation,circuit fault and other disturbances will make the voltage fluctuate or even exceed the limit,so the anti-interference design of the system is carried out.Based on the above research,MPC based on disturbance observer is used to suppress the disturbance.The lumped disturbance which is composed of model parameter uncertainties and external load disturbance can be estimated by linear disturbance observer.Then,the disturbance estimation is introduced into the prediction model to obtain accurate prediction output.It is shown by simulation results that the robustness and disturbance rejection ability of this proposed method are strong.