Power conditioning units

A method of photovoltaic maximum power point tracking (MPPT) in a power conditioning unit for delivering power from a photovoltaic dc power source to an ac mains power supply, the power conditioning unit including an energy storage capacitor for storing energy from said photovoltaic dc power source for delivering to an ac mains power supply output, the method comprising:

• tracking a maximum power point of said photovoltaic dc power source by controlling a dc-to-ac converter converting energy stored in said energy storage capacitor to ac power for said ac mains power supply output, wherein said tracking is performed without measuring a dc voltage or dc current provided from said photovoltaic dc power source.

A method of photovoltaic maximum power point tracking (MPPT) in a power conditioning unit for delivering power from a photovoltaic dc power source to an ac mains power supply, the power conditioning unit including an energy storage capacitor for storing energy from said photovoltaic dc power source for delivering to an ac mains power supply output, wherein, in operation, a voltage on said energy storage capacitor has a sinusoidal voltage component at twice a frequency of said ac mains power supply, the method comprising:

• controlling an amplitude of an ac current provided to said ac mains power supply output such that an amount of power transferred to said ac mains power supply output is dependent on an amplitude of said sinusoidal voltage component on said energy storage capacitor, wherein said controlling is performed by controlling a dc-to-ac converter converting energy stored in said energy storage capacitor to ac power for said ac mains power supply output;
• and
• tracking a maximum power point of said photovoltaic dc source by controlling said dc-to-ac converter.