The additional State Pension, also known as the Second State Pension (S2P) and before that SERPS, was abolished from 6 April 2016. However, any entitlement to additional State Pension that you qualified for in the past may affect the value of your pension under the new State Pension scheme. You can check your pension entitlement on the GOV.UK web site.
People who are self-employed did not build up any entitlement to S2P. And most people who had a salary-related pension would not have been be entitled to S2P for the period when they were building up benefits, as most salary-related schemes were 'contracted out' of the State Second Pension arrangements.