Power system for vertical transportation, method and vertical transportation arrangements

A method of controlling a power system for feeding power into a vertical transportation arrangement, the power system including a first interface for connecting to a primary power source and a second interface for connecting to a secondary power source, the method comprising:

• determining a minimum level other than a zero level for energy available from the secondary power source based on an amount of energy used for a rescue run of the vertical transportation arrangement, and
• controlling feeding of power from the primary power source and the secondary power source to a motor driving the vertical transportation arrangement such that at least some of the power used by the motor during normal operation is fed from the secondary power source while always maintaining the energy available from the secondary power source at or above the minimum level by (i) adjusting the minimum level for the energy available from the secondary power source level based on a load of the vertical transportation arrangement and (ii) planning trips for the vertical transportation arrangement in view of always maintaining the energy level from the secondary power source at or above the minimum level during the normal operation.