A photovoltaic power conditioning unit for delivering power from a dc photovoltaic power source to an ac mains power supply is disclosed. The photovoltaic power conditioning unit may include a non-electrolytic energy storage capacitor, a dc-to-dc converter having an input connection coupled to an input and an output connection coupled to the energy storage capacitor. The photovoltaic power conditioning unit also may include a dc-to-ac converter having an input connection coupled to the energy storage capacitor and an output connection coupled to an output and a power injection control block configured to control an amount of power transferred from the dc-to-ac converter to the ac mains power supply based, at least in part, on an amplitude of a fluctuating sinusoidal component of a dc voltage on the non-electrolytic energy storage capacitor.