According to writer /artist Tony Isabella, DC didn’t want to pay him part of their cut from licensing characters for “Super Friends” and Hanna Barbara didn’t want to pay extra for the right to use the character. So, they created the character Black Vulcan as a copy of the character and DC let them do it.
In response, Isabella wrote the last story of Black Lightning called “The Other Black Lightning” where a villain called Barbara Hanna used a Black Lightning impostor as part of her crime syndicate. DC published the story anyway, as Isabella said in an interview “I don’t think they realized what I was doing there.”
Black Vulcan was pretty cool though... read Marc Tyler Nobleman's interview with the voice of Black Vulcan, Buster Jones.