Two Washington investors are expected to be elected to the board of directors of Advent Corp. today as part of an effort to provide new financing and new management for the struggling electronics manufacturing company.

Nominated for election at Advent's annual stockholders' meeting in Boston are Joseph Farland, 66, a veteran diplomat and former ambassador to Iran, and I. Townsend Burden III, 37, vice president of Secor Investments, a subsidiary of Security Storage Co. of Washington.

Farland and Burden are not opposed for seats on Avent's board, which already includes Washington businessman Robert D. van Roijen Jr., an officer of both Secor and Security Storage.

Burden, van Roijen, and Secor recently have made extensive investments in Advent, a company that makes stereo speakers and components and was the first to market a giant-screen television.

Since then Avent has sold more than 38,000 giant-screen TVs, making it the leader in that business. But sales plunged 28 percent last year, driving the company deeply into the red for the second year in a row. Advent lost $4.8 million in 1978 and 1979 and posted an $893,000 loss in its first quarter this year.

Recently van Roijen, Burden, Secor and others associated with the firm have bought the equivalent of an 11 percent interest in Advent, reports to the Securities and Exchange Commission show. Farland, who is not associated with Secor, owned no Advent stock at the time he was nominated to the board, the SEC files indicate.

The Secor group has not bought Advent stock directly, instead purchasing convertible debentures which can be exchanged for Advent stock. If all the debentures were converted, the Washington group would own more than 299,000 shares of Advent.

Advent's biggest shareholder -- who with his wife owns more than 25 percent of the stock -- is Board Chairman Peter J. Sprague, who is also chairman of National Semiconductor Co.