Rub salmon fillets with about 1 tablespoon brown sugar. Lightly sprinkle with lemon pepper and garlic powder. Rub seasoning into salmon.
Into a small saucepan over medium heat, pour in soy sauce and olive oil. Stir in ginger and remaining brown sugar, lemon pepper and garlic powder. Bring to a gentle simmer, stirring constantly until sugar has dissolved. Remove from heat, stir in orange juice.
Place salmon and marinade into a resealable plastic bag; seal, and refrigerate overnight, or for at least 3 hours.
Preheat griller. Place fish in a foil-lined baking pan. Reserve marinade.
Grill fish skin-side up for 2 minutes. Remove from oven, pull skin off with tongs. Brush with marinade, return to griller and cook further 2 minutes. Turn salmon and grill until flesh flakes easily, about 4 minutes. Remove and stand for 5 minutes before serving.