Power electronics is a branch which deals with the study of AC and DC circuits. It requires basic knowledge about p-n junction diode and family of transistors. The power transistors are the main element of power electronics which deals with the power transfer characteristics. Like thyristor, mosfet, igbt, igct, mto, gto etc.. Are used in inverting or converting of AC power, and to balance active reactive components of power. In beginning it's quite tough to learn it but power electronics is just 1st layer of electrical power systems, it is in depth for whom who wants to study advanced power electronics which is the most important subject, to understand facts technology and power quality. But don't worry about it, just start with diodes, scr, and mosfet and learn how many types of converters and inverters are there. Describe each device with voltage and current characteristics, compare them, learn about techniques and concepts precisely frame it in your own words, draw table of switching characteristics. There are some books that you can refer- Power electronics by PS. Shinghare. Power electronics Tata Mcgraw Hill pub. Power electronics by Muhammad H. Rashid Handouts of power electronics by sir Bhim singh. Power electronics by sumitra mandal. (for numericals)