A minimum-energy-based capacitor voltage balancing control strategy for MPC conversion systems

In AC/DC/AC power conversion, the connection of a multi point clamped (MPC) rectifier with an MPC inverter simplifies the balancing of the voltages on the series-connected DC link capacitors as well as giving input power-factor correction capability. This is only true provided that an alternative balancing PWM control strategy is adopted instead of the standard PWM one. A control strategy is proposed which is based on the development of an energy function which may be minimized in real time by exploiting the existing redundancies in power-converter switching states. This strategy may be easily implemented in a DSP controller and is usable with any number of voltage levels and input/output phases. A validation has been performed by simulating a 5-level 3-phase MPC system and the significant waveforms are presented