What questions to prepare for PhD defense? I will soon defend my PhD in social science in Sweden. I want to ask what questions the evaluation committee will ask me during the defense? 
If they ask me some questions outside my thesis, what shall I do? Is it enough only know well my own research?
What quality I need to successfully defend my PhD?
Generally speaking, PhD defenses come in two flavors, and it is not possible to say a priori which one yours will fall into:


A real thesis "defense" focuses on the thesis, and all questions will relate to the scope of the research work. In this case, knowing your own work and its context well enough should be sufficient, but it is of course possible that somebody asks you why you used method A rather than B. In this case, saying that you don't know B may not fly as an answer. However, you should not get a completely disconnected question just to test your general subject area knowledge.
A "Rigorosum" (dict.leo translated this for me to "doctoral viva", no idea if this is a well-known term) is a general final exam for a doctoral candidate. Typically, this will also include questions about the disseration, but anybody in the exam commission is free to ask about other topics in the field as well. Typically, the questions are getting "easier" (more high-level) the farther they are away from the topic of the dissertation. The claim here is that a fresh PhD should have both, depth and breadth in her/his knowledge.


There are a number of ways to figure out which class your defense will fall into:


Attend other defenses. Typically, PhD defenses are public, and it is highly recommended that any PhD candidate should visit a few before her/his own, to get to know the procedure and get a feel for what the defense talk is supposed to look like.
Ask your advisor. The advisor should obviously know what the requirements of the defense are, exactly.
Look it up in the programme description. Usually, the programme description will contain exam regulations for the defense, and this should describe the exam procedure and who is supposed to ask what kind of questions. This approach has two dangers: (1) you may misunderstand what the exam regulations are saying - as they are more legalese text, you may misunderstand the gist of it, and (2) the actual exam may happen differently than specified - there is no telling whether the exam regulation exactly captures the real spirit of the defense. Hence, you should really also talk to your advisor and/or attend other defenses as well.