Control apparatus for an arcp inverter

An auxiliary resonant commutated pole (ARCP) inverter device, comprising:

• a control apparatus
• a dc-link having a first DC rail and a second DC rail,
• a series connection of at least two dc-link capacitances between the two rails of the dc-link, which series connection through a midpoint, called a neutral point (NP) of the dc-link, is divided into two equal parts,
• one or more inverter phases, each of said inverter phases including:
• a series connection of at least two main switching devices between a first DC voltage rail and a second DC voltage rail to alternatively connect the first and second dc-link rails to a phase output by a PWM modulation from the control apparatus,
• one or more resonant capacitors connected in such manner that at least one terminal of the one or more resonant capacitors is operationally connected to one of the dc-link rails or the neutral point and the other terminal is operationally connected to the phase output,
• a series connection of at least two dc-link capacitances between the two rails of the dc-link, which series connection through a midpoint, called a neutral point (NP) of the dc-link, is divided into two equal parts,
• a series connection of a resonant inductance and at least one bi-directional auxiliary switch between said phase output and said neutral point,
• the control apparatus further comprising:
• a modulator configured to carry out a commutation of an auxiliary resonant commutated pole (ARCP) inverter by a pulse width modulation (PWM) technique, wherein the modulator can use a Continuous PWM (CPWM) modulation and a Discontinuous PWM (DPWM) modulation for the commutation of the ARCP inverter, and
• a modulation control configured to dynamically select either the CPWM modulation or the DPWM modulation in a such a way that switching losses of the ARCP inverter are reduced while a failure of the commutation of the ARCP inverter due to a neutral point voltage unbalance of the ARCP inverter is avoided.