Research on decoupling control method for single-phase cascade H-bridge rectifier in coal mine scenarios

In response to the problems of secondary voltage ripple on the DC side of single-phase cascade H-bridge rectifiers during operation in coal mine scenarios, such as grid side current distortion and capacitance drift, this paper analyzes the causes of secondary voltage ripple on the DC side of single-phase cascade H-bridge rectifiers and proposes an optimization control method based on an independent decoupling topology with unequal split capacitors. This method effectively suppresses the secondary voltage ripple on the DC side by overlaying twice the power frequency voltage on both ends of the capacitor to counteract the secondary voltage ripple. A study is conducted on parameter design and control strategies for three decoupling methods based on constructing secondary voltage (DC split capacitor with unequal capacitance values and equal DC voltage components; DC split capacitor with unequal capacitance values and unequal DC voltage components; DC split capacitor with equal capacitance values and unequal DC voltage components). By analyzing the influence of parameters on the amplitude of secondary voltage, the optimal parameter range is determined to achieve effective power decoupling, reduce capacitance values, and lower equipment volume and cost. The simulation results show the following points. ① The split capacitor IAPD (SC-IAPD) is added at 0.2 s, SC-IAPD circuit control method based on decoupling method 2, SC-IAPD circuit optimization control method based on decoupling method 2, and SC-IAPD circuit control method based on decoupling method 1 all control the DC side output voltage ripple at 1-1.5 V. This indicates that the symmetrical half bridge decoupling circuit can effectively suppress DC voltage fluctuations and has good decoupling performance when load changes. ② In the case of light load switching to heavy load, the optimized control method of SC-IAPD circuit based on decoupling method 2 can quickly follow the changes in load, achieve ripple suppression, and have stronger load carrying capacity and better decoupling effect. In the case of heavy load switching to light load, the SC-IAPD circuit control method based on decoupling method 1 can better achieve decoupling performance, controlling voltage ripple within 1 V. If we consider minimizing the capacitance value, the control method of SC-IAPD circuit based on decoupling method 2 is more advantageous. The experimental results show the following points. ① Before the sudden change of load, both traditional control methods and decoupling control methods based on secondary voltage can effectively suppress the voltage ripple on the DC side. However, decoupling control methods based on secondary voltage have better effects in suppressing voltage ripple, resulting in smaller voltage ripple on the DC side. ② After a sudden change in load, traditional control methods cannot maintain the stability of the DC side voltage, resulting in significant oscillations and loss of stability.