Sequentially controlled

Lower harmonic content is sometimes the attractive feature of some control systems. High power Axial flux Permanent Magnet Synchronous Generators for wind applications are often multi modular. Such system are often driven by a multilevel inverter due to its lower harmonic distortion compared to two level inverter. However a two level inverter has the advantage of a much simpler control system and lower cost. This thesis presents a particular system, each module of the machine is connected to a two level inverter; the inverters are paralleled on the dc side. The carrier signal of each inverter is shifted from its neighbouring inverter with an angle. The angles necessary are selected such to cancel out the least harmonic components in the dc side current. There are two types of modulation considered: square wave and pulse width modulation. We analysed the dc side current mathematically for both types of modulation; finding the full expression of the dc current ripple and finding the necessary angles to reduce the current ripple.