A High Power Medium Frequency DC/DC Converter for MVDC Collection System

A high power and high step-up ratio medium frequency DC/DC converter is proposed in this paper, which is suitable for new energy medium voltage dc (MVDC) collection systems. The converter proposed in this paper requires fewer passive devices as well as semiconductor devices. All power switches are insulated gate bipolar transistors, where the switch operating at mid-frequency can realize the ZCS turn-off. Meanwhile, the three-level bridge arm is modulated at high frequency while the two-level bridge arm is modulated at medium frequency to realize high-frequency PWM modulation output voltage and current at medium frequency, such as 400 or 500 Hz, making the transformer not only large capacity but also small size. The working principle of the converter is analyzed in detail and the parameter design is carried out. The operation principles of the proposed converter are verified by simulation and experimental results.