Is it possible to generate artificial gravity without using a centrifuge system?

While it is true that the energy content of something strengthens its gravitation, this is just another way of saying that a more energetic object weighs slightly more than the same object in a lower energy condition. As such, these facts don't furnish us with any tools with which to create "artificial gravity".

Mass and energy are equivalent, and affect gravity in the same way, so yes, you could produce gravity by putting enough energy on your spaceship. But then you're not producing "artificial" gravity, it would be real gravity, and that energy would have inertia just the same as the equivalent mass would. In fact matter is probably the most compact form of energy. Basically you're looking at having a spaceship big enough to have a significant gravitational field of its own. This is not very practical.

A far better way to produce artificial gravity is to accelerate. While your spaceship is accelerating, all of its passengers feel a force pushing them towards the back of the spaceship. This force is indistinguishable from gravity (it's called the "equivalence principle"). Of course this would require a lot of fuel or some form of external propulsion.