Apparatus and method for controlling DC-AC power conversion

An apparatus for controlling the delivery of power from a unipolar input source to an alternating-current (AC) grid at a grid voltage and grid frequency, the apparatus comprising:

• an inverter comprising:
• an input converter configured to deliver power from the unipolar input source to a unipolar bus;
• an active filter configured to supply energy to and absorb energy from the unipolar bus;
• and
• an output converter configured to deliver power from the unipolar bus to the AC grid, and
• an inverter controller configured to maintain a voltage of the unipolar bus at a pre-determined value, the inverter controller comprising:
• an input converter controller to control a power delivered by the input converter to the unipolar bus;
• an output converter controller to control the output converter to deliver power to the AC grid;
• and
• an active filter controller to control the active filter to supply time-varying power to the output converter.

A method for controlling an inverter that is configured to deliver power from a unipolar input source to an alternating-current (“AC”) grid at a grid voltage and grid phase, comprising:

• delivering, by an input converter, a pre-determined amount of power from the unipolar input source to a unipolar bus;
• supplying, by an active filter, energy to and absorbing energy from the unipolar bus;
• delivering, by an output converter, power from the unipolar bus to the AC grid;
• and
• controlling, by an inverter controller, the operation of the inverter by (i) controlling the input converter to deliver a first portion of the average power delivered to the AC grid, (ii) controlling the active filter to deliver a second portion of the time-varying power that is delivered to the AC grid, and (iii) regulating the unipolar bus voltage to a first pre-determined value.