Linverter a low-harmonic and high-bandwidth inverter based on a parallel multilevel structure

Switched mode power converters are the key element in modern drive systems. However due to their operating principle based on pulse-width modulation, there are some disadvantages for using converters as their functionality is restricted and additional stress is caused to the environment and to the motors they drive. The main problems in this regard are the additional harmonic losses, bearing currents, auxiliary stress of the winding insulation and pollution by acoustic as well as electromagnetic noise. Considering these issues a new inverter circuit has been developed in order to minimize these undesirable effects. The suggested circuit is based upon a parallel multilevel bridge structure. The load current is shared equally between the parallel bridge arms and the single inverter legs are decoupled by means of common mode chokes. Thus the currents of the different legs flow magnetically compensated towards the output. Therefore it is possible to carry high load currents even by using very small inductive components. By applying an appropriate pulse pattern to trigger the bridge transistors, a significant suppression of harmonics in the output is obtained. An additional damping effect can be obtained by using output capacitors, so that essentially only the desired fundamental wave remains in the output signal.