Control of an electrical converter

A method of controlling an electrical system including a three phase AC input supply and three or more H-bridge converter cells, each H-bridge converter cell having an active front end rectifier, a capacitor, and an inverter, the method including:

• operating each H-bridge converter cell such that:
• each active front end rectifier receives a three-phase AC input supply and transforms it into a DC supply providing a respective rectifier current ii;
• each capacitor receives a respective capacitor current iC, the capacitor smoothing the DC supply, and
• each inverter receives a respective inverter current io, wherein io=ii−ic, the inverter transforming the received inverter current io into a single phase AC supply;
• and
• providing a signal to the active front end rectifier of each H-bridge converter cell, the signal varying the rectifier current ii provided by the active front end rectifier such that the difference between the rectifier current ii, and the inverter current io, is substantially zero,
• wherein the signal is modified based upon a feed-forward load current corresponding to the inverter current io, and a value of the feed-forward load current is calculated based on a desired DC-link voltage across the capacitor, the desired DC-link voltage being calculated, and not based on an actual DC-link voltage across the capacitor, the actual DC-link voltage being measured.