Study On 3-D SVM Modulation In Stationary Coordinates For Four Legged Inverters

Generally, the three phase inverters are composed of three legs. But, whenit supply to the three phase unbalanced loads, its three phase voltage outputswill be dissymmetrical. Three-phase four-legged inverters are bringing forwardto power unbalanced three-phase loads. The topology is known to producebalanced voltages even under unbalanced load conditions. And compared to theother three-phase four-wire inverters, its size and weight are smaller.At the beginning, the merits and faults of several methods which cansolve the unbalanced load question are discussed. According to the analyse, theconclusion that the structure of the three phase inverters with the forth bridgelegs excel to the other topology is got. After that, the principle of threedimensional space vector modulations in abc coordinates is introduced. Thanksto the use of abc coordinates, the algorithm is much simpler and more intuitivethan in α -β -γ representation, drastically reducing the complexity ofmodulations algorithm. And we supplied the calculation formulation.Secondly, the simulation of system control and switch strategy validatedconsistency with theory analysis using MATLAB. The result match with theanalyse.Finally, the experiments are completed under the digital control, thesimulation results is verified. The three-phase four-legged inverter with 3-DSVM in abc coordinates can output the excellent three-phase AC voltage underthe unbalanced load conditions.