The invention relates to a powder coating composition for low temperature curing that can be used on temperature sensitive substrates and, despite of the low curing temperature, has excellent flow properties and forms a coating with excellent appearance and nevertheless also good mechanical and weathering properties. The invention also relates to an advantageous process for the manufacture of the powder coating composition. Said powder coating composition comprises a poly-acid functional polyester component A, a poly-epoxy functional component B, a poly-anhydride functional component C and a thermosetting curing catalyst D. The invention also relates to a polyester for use in the powder coating compositions according to the invention, in particular for durable powder coatings.