Control of DC voltage distribution system

A method of controlling a DC voltage distribution system, the DC voltage distribution system comprising:

• a DC voltage bus,
• a fuel cell electrically connected to the DC voltage bus,
• an energy storage and an energy storage converter, wherein the energy storage converter is a bi-directional DC to DC converter, and wherein the input of the energy storage converter is connected to the energy storage and the output of the energy storage converter is connected to the DC bus,
• wherein the method comprises:
• determining a DC voltage reference for the DC voltage bus, the energy storage converter controlling, based on the DC voltage reference, a voltage of the DC voltage bus by providing power from the energy storage to the DC bus or to the energy storage from the DC bus,
• determining, based on a measurement associated with the energy storage, whether a direction of power flow between the energy storage converter and the energy storage is towards the energy storage or towards the energy storage converter, and
• changing the DC voltage reference on the basis of the detected power flow between the energy storage converter and the energy storage to change the power taken from the fuel cell, wherein changing the DC voltage reference comprises:
• as a response to the direction of the power flow being from the energy storage converter towards the energy storage, raising the DC voltage reference so power provided by the fuel cell decreases;
• and
• as a response to direction of the power flow being from the energy storage to the energy storage converter, lowering the DC voltage reference so the fuel cell provides increased power,
• wherein the power flow between the energy storage and the DC voltage bus changes in response to changes in a load on the DC voltage bus.