Rinse beans. In a large saucepan combine beans and enough water to cover them. Bring to boiling; reduce heat. Simmer for 2 minutes. Remove from heat. Cover and let stand 1 hour. (Or, omit boiling and soak beans overnight.)
Drain and rinse the beans. In a 4- or 6-quart pressure cooker place beans, sausage, carrots, onion, sweet pepper, garlic, chili powder, oregano, chicken broth and water.
Lock lid in place. Place pressure regulator on vent pipe (if you have a first-generation cooker). Over high heat, bring cooker up to pressure. Reduce heat just enough to maintain pressure and pressure regulator rocks gently; cook for 12 minutes.
Quick-release the pressure. Carefully remove lid.
Sprinkle with green onion and tomatoes, if desired. Makes 6 main-dish servings (7 cups).