Control and modulation strategies for a multi-level H-bridge StatCom

This thesis develops control and modulation schemes for a multi-level H-bridge StatCom (HStatCom). The use of H-StatComs in high-power applications is increasing primarily due to the smaller footprint, higher achievable voltage levels, and ease of construction and maintenance of the device. However, there remain areas of research aimed at improving the performance of the topology. With improved performance and lower cost, the H-StatCom will find increasing application in both the medium and high voltage networks, and become an integral component in the distributed generation landscape. The practical performance of the industry standard modulation technique for H-StatComs is explored. It is shown that subtle implementation issues degrade the harmonic performance of this scheme. It is then observed that the existing modulation technique does not consider the large amounts of redundancy in the available switching states for the topology. Given this observation, the main contribution of this thesis is to develop a variation on a typical model predictive control scheme. The scheme can exploit the switching redundancy to simultaneously balance the H-bridge capacitor voltages, provide excellent current reference tracking and minimise converter switching losses. Finally, experimental and simulation results are presented that confirm the validity of the new strategy. The results show that model predictive control exceeds the performance of well established modulation schemes and provides extra flexibility to optimise user-defined key performance indicators.