Research and Simulation of DC Microgrid Three-Phase AC-DC Converter Control Strategy Based on Double Loop

Abstract

The new voltage and current double loop control strategy is proposed to solve the DC microgrid bus voltage fluctuation caused by loads fluctuation, parameters perturbation and unbalanced three-phase power supply. Firstly, the dq axis mathematical model of three-phase AC-DC bidirectional converter in DC microgrid is analyzed and established, and then the controllers are designed according to the dq axis mathematical model. The outer loop is a voltage loop based on variable gain linear extended state observer (VGLESO) and sliding mode theory. VGLESO can not only effectively overcome the problem of peak output of traditional high-gain LESO in the initial stage of operation, and ensure that the system has good startup characteristics, but also quickly track and compensate the total disturbance of the system without additional current sensors. The inner loop is a current loop based on adaptive PI, which can eliminate the influence of system parameters perturbation on bus voltage and improve the system's adaptability. Under the action of the inner and outer loops, the system has good dynamic and static characteristics. Finally, the feasibility and correctness of the control strategy are verified by Matlab/Simulink.

Discrete-Time Adaptive Control for Three-Phase PWM Rectifier

“…Considering that the three-phase PWM rectifier normally operates at a unity power factor, i q * (k) = 0. Consequently, the discrete-time model of the rectifier can be obtained from Equation (4).…”

“…In Figures 5 and 6e, DDPIC exhibits an excellent steady-state performance. However, the PI controller based on the deviation control principle makes it difficult to overcome the control time lag caused by the capacitive element [4], resulting in a low response. From Figures 5 and 6c, it is evident that the DDFLC exhibits a significant steady-state error.…”

“…However, PWM rectifiers are inherently nonlinear, multivariable, and coupled systems [2], and their control performances are susceptible to practical disturbances such as DC load disturbances and mismatched parameters (parameter disturbances). Therefore, anti-disturbance control strategies for rectifiers have garnered significant attention in recent years [3][4][5].…”

Coordinated Voltage-Power Control for DC Distribution Networks Based on an Uncertainty and Disturbance Estimator

“…To effectively regulate the DC bus voltage, the current inner loop robust control in dualloop control has been studied in many kinds of literature. In [16], a current loop based on adaptive PI was proposed to eliminate the influence of system parameter disturbance on the DC bus voltage and improve the system's adaptability. In [17], a time-delay compensation method based on a second-order generalized integrator was applied to the current inner loop to reduce the system's sensitivity to parameter variations, thus improving the system's immunity.…”

A Novel Control Technique for Voltage Balancing in Bipolar DC Microgrids

“…To achieve a robust and efficient DC microgrid, an accurate design and control of the converters is required. Numerous studies have been conducted to improve the AC/DC converter's structure [13][14][15] and enhance the system stability by proposing different linear [16] and nonlinear [17] control strategies. However, few studies on bipolar DC microgrids have focused on proposing improved design and developing advanced control techniques for DC/DC converters; the latter plays an equally essential role in DC microgrids as the AC/DC converters.…”