Abstract
Soft open point (SOP) is a key power electronic device to improve the flexibility and stability of the distribution network and is becoming a research hotspot. The traditional double closed-loop control of SOP has a complex structure, difficult process of parameter design, and poor output power quality. To solve these problems, finite control set model predictive control (FCS-MPC) has been adopted. Since FCS-MPC involves a large amount of calculation and experiences delay in current tracking, an improved FCS-MPC with delay compensation is proposed for three-port SOP in this paper to replace the inner loop current control strategy. Improved model predictive control combines the two-step prediction method based on the voltage vector and vector angle compensation method. The vector method is used to construct a mathematical model and a prediction model of three-port SOP. Based on FCS-MPC, the two-step prediction method that takes voltage as the target is used to compensate for the current delay problem, and the amount of calculation is reduced by converting the control target. Meanwhile, the vector angle compensation method is used to compensate the future reference value. Finally, a simulation model is built in MATLAB/Simulink. The simulation results under steady state and dynamic conditions show that the proposed strategy can effectively improve the current delay and reduce the amount of calculation. Furthermore, it has better current tracking accuracy and faster dynamic response speed.
Highlights
With the increasing application of new energy such as wind energy and solar energy, the penetration rate of renewable distributed energy in the distribution network is getting higher and higher [1, 2]
Ese problems have seriously affected the stability and safety of the distribution network [3, 4]. e original adjustment methods of the distribution network have limited control accuracy and adjustment speed, which has restricted the improvement of the control ability of the distribution network. erefore, to further improve the flexibility and reliability of the operation of the distribution network, the development of power electronic equipment for the distribution network has attracted the attention of scholars from all over the world
To realize the decoupling control between the variables of the system, this paper uses the vector method and dq coordinate transformation method to establish a three-port Soft open point (SOP) mathematical model. e control scheme designed in this paper combines the advantages of finite control set model predictive control (FCS-MPC) while improving its shortcomings
Summary
With the increasing application of new energy such as wind energy and solar energy, the penetration rate of renewable distributed energy in the distribution network is getting higher and higher [1, 2]. To solve the above problems, an improved model predictive control strategy based on three-port SOP is proposed, which can replace the inner loop current control of double closed-loop control. By using the improved FCS-MPC to replace the inner loop current control with double closed-loop control, the complex parameter design process of the proportional-integral (PI) regulator can be omitted, and the dynamic response speed and steady-state tracking accuracy of the current can be effectively improved. Where Pj and Qj are the active and reactive power output of port j, ijd and ijq are the components of three-phase load output current on the d-axis and q-axis, respectively, and Ejd and Ejq are the components of grid voltage on the d-axis and q-axis of port j, respectively. By controlling ijd and ijq, the active power and reactive power of each port of the three-port SOP can be independently controlled, so the power decoupling control is realized
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