Auxiliary power supply

1 . An auxiliary power supply arrangement of a wind turbine, comprising:

a standby power supply configured to supply sufficient power to cover the average steady state power requirements of auxiliary devices of the wind turbine when the wind turbine is operating in an off-grid mode, wherein the standby power supply is one device; and

an energy storage unit, wherein the energy storage unit is configured to cover peak transient power requirements of the auxiliary devices and/or to supplement the standby power supply in covering the peak transient power requirements of the auxiliary devices,

wherein the auxiliary devices comprise devices required temporarily during stages of installation, commissioning, or maintenance, and

wherein the standby power supply has a capacity that is less than a reference capacity that covers the peak transient power requirements of the auxiliary devices.

2 . The auxiliary power supply arrangement according to claim 1 , wherein the energy storage unit is a rechargeable energy storage module.

3 . The auxiliary power supply arrangement according to claim 2 , wherein the energy storage unit comprises a lithium-ion battery or a supercapacitor arrangement.

4 . The auxiliary power supply arrangement according to claim 1 , wherein the energy storage unit has an energy storage capacity in a range of 5 kWh-1 MWh and a rated apparent power output in a range of 50 kVA-400 kVA.

5 . The auxiliary power supply arrangement according to claim 1 , wherein the standby power supply generates power from a renewable energy source.

6 . The auxiliary power supply arrangement according to claim 1 , wherein the standby power supply comprises a photovoltaic arrangement, a gas turbine, a fuel cell, a wave energy converter, a compressed-air energy storage module, or a diesel generator.

7 . The auxiliary power supply arrangement according to claim 1 , wherein the energy storage unit and the standby power supply are connected in an inline arrangement.

8 . The auxiliary power supply arrangement according to claim 1 , wherein the energy storage unit and the standby power supply are connected in a line-interactive arrangement.

9 . A wind turbine comprising:

an aerodynamic rotor mounted to a hub;

a nacelle mounted on a tower;

a generator arranged in the nacelle;

a number of auxiliary devices; and

an auxiliary power supply arrangement according to claim 1 configured to supply power to the auxiliary devices during an off-grid state of the wind turbine.

10 . The wind turbine according to claim 9 , comprising a monitoring unit configured to monitor power consumed by the auxiliary devices.

11 . The wind turbine according to claim 10 , wherein the monitoring unit is configured to control the operation of an auxiliary device of the auxiliary devices on the basis of data provided by the monitoring unit.

12 . A method of operating the wind turbine according to claim 9 , said method comprising:

detecting the off-grid state;

controlling the standby power supply of the auxiliary power supply arrangement to cover the average power requirements of the auxiliary devices; and

discharging the energy storage unit to cover transient power requirements of the auxiliary devices.

13 . The method according to claim 12 , wherein the energy storage unit is recharged when power consumption of the auxiliary devices is below the output power capacity of the standby power supply.

14 . The auxiliary power supply arrangement according to claim 1 , wherein the standby power supply and the energy storage unit are connected to each other by a socket such that the standby power supply and the energy storage unit are each directly connected to the socket.

15 . The auxiliary power supply arrangement according to claim 14 , comprising a monitoring unit configured to monitor power consumed by the auxiliary devices, wherein the monitoring unit is connected to the standby power supply and the energy storage unit by the socket, and wherein the monitoring unit is directly connected to the socket.

16 . The auxiliary power supply arrangement according to claim 1 , wherein the capacity of the standby power supply is rated to cover only the average steady state power requirements of the auxiliary devices.

17 . The auxiliary power supply arrangement according to claim 1 , wherein the capacity of the standby power supply is at most 20% of the reference capacity.

18 . The auxiliary power supply arrangement according to claim 1 , wherein the auxiliary devices comprise devices required temporarily during stages of installation or commissioning.