三相功率因數修正器被廣泛地使用在電動車領域及資料中心等領域。多階式飛馳電容架構與二階式架構及其他多階式架構相比能使用低感值的電感、高功率密度的陶瓷電容，並有較低的開關切換損失，因此可以達到高效率及高功率密度。空間向量脈波寬度調變法(Space-Vector Pulse Width Modulation, SVPWM)常用在三相轉換器以減小電感電流漣波，但將其用在三相多階式FCML轉換器時，箝位電容的電壓會不平衡。相移調變法(Phase Shift Pulse Width Modulation, PSPWM)常用於FCML架構，以達成箝位電容的電壓平衡，並能增加開關切換點對地電壓的等效切換頻率以降低電感電流漣波，但將其用在三相多階式FCML轉換器時，因為開關切換點對地電壓會在部分的責任週期與開關的驅動信號間出現相位差，讓三相的開關切換點對地電壓無法保持中心對齊，使電感跨壓較使用SVPWM的三相轉換器大，而導致電感電流漣波上升。本篇論文提出一個適用於三相FCML轉換器的動態相移脈波寬度調變法(Dynamic Carrier Phase-shift Pulse Width Modulation, DPSPWM)，於PSPWM的基礎上改變各相載波之間的相位，讓三相的開關切換點對地電壓保持中心對齊，使此調變法可以大幅降低電感跨壓及電感電流漣波，並維持PSPWM原有的優點。本論文將說明新型調變法之詳細動作原理、三相FCML功率因數修正器之小訊號分析、補償器的設計、數位晶片的程式流程。本論文最終完成採用新型調變控制方式實現一高效率高功率密度之三相六階式功率因數修正器，其輸入電壓為120 Vrms、輸出電壓為400 V、輸出功率為6 kW、峰值效率為98.5%，而電感之等效頻率可達到1 MHz。

Three-phase rectifiers with power factor corrector (PFC) at kilowatt levels are widely used in applications such as electric vehicle (EV) charging and data center power delivery and so on. Compared to two-level and other multilevel toplologies, the three-phase flying-capacitor multilevel (FCML) rectifier with GaN devices can achieve high power density and high efficiency due to the smaller required inductance, the use of high-energy-density ceramic capacitors and smaller switching loss. Space-vector pulse width modulation (SVPWM) is a common modulation method to reduce the inductor current ripple in three-phase 6-switch ac-dc converters. Phase-shift PWM (PSPWM) which is commonly used in FCML boost converters to achieve natral balancing of flying capacitors and increase the switching node voltage’s equivalent frequency. Therefore, the inductor current ripple can be reduced. However, there is a phase shift between switching node voltage and driving signal of the switches under part of the duty cycle condition. If the FCML topology with PSPWM is used in three-phase converters, the switching node voltage in each phase can not be center-aligned, which results in higher voltage stress on the inductor than using SVPWM. Thus, the inductor current ripple increases. In this paper, d Dynamic Carrier Phase-shift Pulse Width Modulation for three-phase FCML converters which is based on PSPWM to dynamically phase shift the carrier between each phase is proposed. Then, the switching node voltage of each phase can be center-aligned. Hence, the control technique can greatly reduce the voltage stress of the inductor, reduce the inductor current ripple, and maintain the characteristics of PSPWM. The detailed operation of the proposed modulation, the small-signal analysis, the design of the controller, and the implementation in the digital controller are discussed. The three-phase six-level FCML PFC rectifier with high efficiency and high power density, which has been tested up to 6 kW at 120 Vrms to 400 V, achieves a peak efficiency of 98.5% and an effective inductor switching frequency of 1 MHz.

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