Design and Implementation of High Efficiency, High Power Density Front-End Converter for High Voltage Capacitor Charger

Pulse power system is widely used for medical, industrial and military applications. The operational principle of the pulse power system is that the energy from the input source is stored in the capacitor bank or superconducting inductive device through a dc-dc converter. Then, when a discharging signal exists, the stored energy is released to the load through pulse forming network (PFN) generating high peak power pulse up to gigawatts within several tens of or hundreds of microseconds.

The pulse power system has been originally developed for the defense application. After the format of the voltage compression and voltage addition stages for the short-pulse high power acceleration has been established, it has been evolved to be common. Then, its application has been extended to food processing, medical equipment sterilization and wastewater treatment since many present environmental problems have been known in the early 70's or even earlier. In addition, the pulse power system is newly spotlighted due to the recent world events. The application examples are to treat anthrax-contaminated mail, and the use of accelerators to produce high power X-rays for security screening.

Furthermore, the pulse power system has been applied for the tactical weapon system such as electrothermal-chemical (ETC) gun, coilgun and active armor system. Because the pulse power system applied for the tactical weapon system has the potential to be integrated in the military vehicle, a compact, lightweight pulse power system is strongly required for the future weapon system.

In this thesis, a distributed power system (DPS) for the capacitor charger is introduced for the application of the active armor system. Furthermore, a design methodology is presented for the front-end converter to achieve the high efficiency as well as the high power density. Design parameters are identified and their impact on the design result is studied. the optimal operating point is determined based on the loss comparison between different operating points.

In order to further improve the power density utilizing the unique operation mode i.e. pulse power operation, transformer design using amorphous-based core is provided and the design result is compared with that using ferrite-based core. A 5 kW prototype converter is built up and the experimentation is performed to verify the design.