President Carter this week will ask Congress for a five year, $1-billion authorization for public broadcasting and at the same time seek major changes in its current structure to end years of internal strife in the system.

Key features of the administration proposal which will be contained in a message to Congress expected on Thursday include:

Authorization of $180 million to public broadcasting in fiscal 1981 and $200 million for each of the four years thereafter. Twenty-five per cent of the total federal contribution would be earmarked for national programming each year under the White House plan.

Designation of the Public Broadcasting Service as the central programming authority for public television.

The assignment of long-range planning responsibilities to the Corporation for Public Broadcasting as overseer of the TV an dradio system with increased emphasis on aiding minority participation in public broadcasting.

CPB would be given the added task of administering $30 million a year in facilities grants, currently handled by the Department of Health, Education and Welfare.

However, responding to pressure from public TV stations which have often circumvented CPB funding strictures in the past by obtaining money directly for specialized programming from agencies like the National Institute of Health and the National Endowment. CPB will not gain control over every federal funding source for TV under the administration bill. Instead, the corporation will be charged with maintaining an up-to-date list of funding sources to aid stations in their money search, a service previously not available.

CPB will be required to cease its current programming functions and cut the size of its present staff, which new frequently overlaps PBS functions. The Corporation was created by the Public Broadcasting Act of 1967 to distribute federal funds to the public system and to serve as a non-political buffer between Congress and the broadcasters.

Under the Nixon administration, however, the presidentially-appointed CPB board of directors moved into the programming area, long a sore point with PBS, which represents the 260 TV stations in the public system.

The White House also will ask that Congress approve a new system of appointing CPB board members to include four members to be chosen by the industry, two by PBS membership and two by National Public Radio. The remaining seven members would still be chosen by the President.

Barry Jagoda, special assistant to the President, said yesterday that a major aspect of the Carter plan for CPB is to make public broadcasting a "truly national system."

He pointed out that currently only 50 per cent of the country is covered by public TV, which is mostly confined to UHF outlets, while NPR's 199 stations reach just (6) per cent of the potential national audience.

Terming the reorganization plan "a principal initiative in the communications field," he emphasized that "the White House is not choosing between CPB and PBS."

He said the plan follows "wide-ranging briefings and consultations with key members of Congress and leaders of the public broadcasting community. An effort has been made to effect changes in complete harmony. All the persons we've talked to are sincerely concerned about a strong public system in this country."

Jagoda said the reorganization plan has been coordinated by Stuart Eizenstadt, assistant to the President for domestic policy, working closely with White House aide Richard Neustadt. Washington attorney Frank Lloyd and Robert Sachs, a former congressional aide.

Public broadcasting is currently operating on a federal appropriation of $103 million, only $13 million of which has been designated for national programming and $4 million for national radio. In addition, around $19 million is available for programming from PBS station cooperative system.

The present five-year authorizations, which began in 1975, are made two years in advance and are based on a matching formula under which the system must raise $2.50 from non-federal sources for every $1 in federal funds. The administration bill would lower the matching through formula to $2.25 for every $1 over the next five-year authorization.