The convention - which takes place from 22nd to 24th November inclusive - will have a range of activities, including panels with key cast members from 50 years of the programme, special-effects shows, stunt workshops, quizzes, and games.
In a statement, BBC Worldwide said:
After tickets to the official Doctor Who 50th Celebration in November were snapped up in less than 24 hours earlier this year, a limited number of additional tickets are now available to apply for via a ballot process.Applications can be made online or by phone on 0844 693 0780 (charges will vary depending on the provider). Applicants with disability access requirements can discuss these with a team member by calling the dedicated CrowdSurge helpline on 0843 459 4939 (again, charges will vary depending on the provider).
The ballot will be open until 10am BST on Monday 30th September.
One entry is being allowed per person and names will be drawn at random from all of the applications that have been submitted by the closing date and time. Successful and unsuccessful applicants in the first ballot will be notified via e-mail on Tuesday 1st October. If successful applicants do not have a valid e-mail address they will be contacted by telephone. Unsuccessful applicants without an e-mail address will not be contacted.
Those who are successful will receive a unique code to be used by 10am BST on Thursday 3rd October to buy tickets to the convention. The code can only be used once, and up to four tickets can be bought but they must be in the same transaction. The code is only valid for the date and entry group originally chosen in the application.
Should any tickets remain from the first ballot, a second ballot will be opened and all applicants who were unsuccessful in the first ballot will be automatically entered into the second ballot. Ballot rounds will continue to be held until all the tickets have been sold.
The tickets being balloted and sold are the standard ones, with the price remaining at £45 for adults, £20 for children, and £104 for a family ticket (two adults and two children). Please note that these prices exclude any booking fees.
No additional merchandise, photos, autographs, or T-shirts will be available to buy at this stage. The limited-edition TARDIS tickets are sold out and will not be included in the ballot. Full terms and conditions can be found here.